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A Bridgeless Luo Converter Based Speed Control Of Switched Reluctance Motor Using Particle Swarm Optimization (Pso) Tuned Proportional Integral (Pi) Controller
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A Bridgeless Luo Converter Based Speed Control Of Switched Reluctance Motor Using Particle Swarm Optimization (Pso) Tuned Proportional Integral (Pi) Controller R Kalai Selvi , R Suja Mani Malar PII: DOI: Reference:
S0141-9331(19)30661-1 https://doi.org/10.1016/j.micpro.2020.103039 MICPRO 103039
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Microprocessors and Microsystems
Received date: Revised date: Accepted date:
3 December 2019 12 February 2020 14 February 2020
Please cite this article as: R Kalai Selvi , R Suja Mani Malar , A Bridgeless Luo Converter Based Speed Control Of Switched Reluctance Motor Using Particle Swarm Optimization (Pso) Tuned Proportional Integral (Pi) Controller, Microprocessors and Microsystems (2020), doi: https://doi.org/10.1016/j.micpro.2020.103039
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A BRIDGELESS LUO CONVERTER BASED SPEED CONTROL OF SWITCHED RELUCTANCE MOTOR USING PARTICLE SWARM OPTIMIZATION (PSO) TUNED PROPORTIONAL INTEGRAL (PI) CONTROLLER Kalai Selvi.R1 Suja Mani Malar.R2 Associate Professor, 2Professor& Vice-Principal, 1 Department of Electrical & Electronics Engineering, Vallioor, Tirunelveli 2 DMI College of Engineering, Palanchur, Chennai, Tamil Nadu, India. [email protected] 1
Abstract: Motors are essential parts of each moving equipments that is used for various sorts of moving applications. There are a few kinds of motors accessible for different types of industrial applications, But compared to all types of motors the advantages of Switched Reluctance Motor (SRM) in low and medium power applications has ended up being much effective than the other kinds of motors considering the variables like high flux thickness per unit volume, high effectiveness, low electromagnetic obstruction and low maintenance requirements. This work proposes a bridgeless based Luo converter fed Switched Reluctance Motor drive utilizing Particle Swarm Optimization (PSO) tuned Proportional Integral (PI) controller. The PI tuned converter gives high proficiency, high power thickness, and small structure of the motor driver. The accomplished yield voltages of the proposed converter are connected to SRM motor. The SRM here is chosen for the drive because of its minimal effort and simple development. The proposed Luo converter based SRM drive framework have been approved through simulation utilizing Matlab/ Simulink design. The simulation results validate the Power Factor Correction (PFC) activity with reduced output current THD underneath 9%, according to the given IEEE standard. Keywords: Switched Reluctance Motor, Power Factor Correction, Particle swarm optimization, Total Harmonic Distortion, Bridgeless Luo Converter. 1.
Introduction
The Switched Reluctance Motor is a kind of electric motor that keeps running by reluctance torque. Switched Reluctance Motor is electromagnetic and electro-dynamic hardware which convert electrical energy into mechanical energy. It gives high dependability; at steady power it provides an electric range, low fabricating cost, good dynamic reaction, and ruggedness and fault resistance. The switched reluctance motor drives are discovering application in high volume apparatuses and modern applications which can take significantly preferred standpoint of their qualities with high starting torque. The torque is formed by the sequence action of poles. The PFC converters give the power factor according to power quality standards for low power equipment such as IEC 61000-3-2.Additionally, the present forming lessens the input current THD which enhances the present correction factor. Many single-stage PFC converter topologies are accounted for in the literature. Three working modes are explored to work these PFC converters, for example, Continuous Conduction Mode (CCM), Discontinuous Conduction Mode (DCM) and Critical Conduction Mode (CRM). The constant inductor current in CCM offers low input current swell and lessened Electromagnetic Interference (EMI). Electromagnetic Interference encounters hard switching, as inductor current stays constant all through the switching time frame. In CRM of activity, PFC converters accomplish zero current of power switch and zero current for the diode. However, switching frequency fluctuating over a wide range is the negative mark related with CRM, which results in decrease in productivity and complexity in Electro Magnetic Field (EMF) channel outline. In late, the
transition techniques are quickly formed and DC-DC converters have a lot of divisions. Dr. Fang Lin remarkable arrangement has been created by the DC / DC converters, including LUO converter, positive/negative/double output LUO converters over the amount of 100 novel propagation. A LUO converter is broadly used because the voltage has its inherent properties such as the lift, super lift and ultra-lift literature. Among them, the super-lift LUO converter is said to be exceptionally based on the fact that the voltage switch gain is higher. The voltage lift (VL) process is commonly used in electronic circuit strategy. Along with the improvement of the transformation system, the Super-Lift (SL) strategy is more powerful than the voltage lift system. SRMs require energy converters to control the succession of the stator windings. Generally SRM motor converters have two switches at each stage. These SRM current waveforms are highly adaptable and compulsive controls, and the most astounding number of switches. The converter circuit additionally comprises of low pass LC passive filter. The LC passive filter gives change in the Distortion Power Factor (DPF), as the outline of filter capacitor is made to give the required stage move to PFC. In the mean time, this passive filter additionally offers low impedance for the switching harmonic, without considering the supply side information. II. Literature Survey The Switched Reluctance Motor (SRM) is a single excited system in which the magnetic flux responsible for producing the torque is produced by the excitation of a single coil at a time [1]. No other magnetic fields are involved in the dynamics of the machine. Therefore, the SRM uses neither permanent magnets nor the principle of electromagnetic induction. The stator of the SRM consists of wound discrete pole type with 6 or 8 poles much similar to the conventional DC motors [2]. The rotor of the salient pole structure and typically the rotor poles are formed by laminated cores with shapes so designed to form the salient poles. The number of stator poles are not equal to the number of rotor poles [3- 7].The rotor poles do not carry any winding, which depends on the weight, inertia and exhibits low frictional losses. The SRM does not exhibit high hysteresis, eddy current and copper losses like other motors and hence it is highly efficient and is suitable in high speed applications. Although simple in construction the SRM is not an easy to drive machine like the squirrel cage induction motor or the conventional DC motors. The phases of the SRM, or in other words the poles of the stator in the SRM are to be energized, which is based on Hall Effect or an Infrared Slot sensor based position sensor. SRM needs the support of power electronics circuit for routing the electrical power to the machine and need some digital electronics methods for controlling. To develop the closed loop speed controller a digital microprocessor or micro controller like the PIC Micro controller is required [8-10]. There are two major drawbacks with the SRM. The first issue is the ripple that is contained in the torque. Because of sequential switching of the stator poles one after the other and since there exists a dead time between the energizing of each of the stator coils there is a drop in torque produced during every transition period [11]. Further because of the intermittent switching of the stator coils, the power drawn from the main power supply is also intermittent [12]. If the source is derived from a three phases or single phase AC utility supply the source currents exhibit rich harmonics. Exhaustive research has been carried out and is still going on to improve the quality of torque produced and the quality of the source current, when power is drawn from the utility AC power supply [13-15]. Research in certain distinguishable prime directions are going on to explore the various possibilities of using the modern design tools like the finite element analysis or by using the various other electromagnetic design software tools, that could lead to improved torque production capabilities with less torque ripple [16]. Shaping of the pole faces is also considered as a feasible method to improve torque quality [17]. The other direction of research is to find the possibilities of novel circuit topologies [18] for driving the SRM and this direction of research, also contributed significantly with many topological variations that usually happens with the type of the available sources like DC source from rectifiers, renewable sources like the solar PV panel, the fuel cell sources and batteries. Controlled and uncontrolled rectifiers followed by DC to DC converters of the generic type or the advanced converters like CUK, SEPIC or the LUO converters have also been tried with the SRM. The matrix converter is another option when the source is the multiphase type AC.
The other direction of research has been the development of various control schemes [19, 20]. Right from the PI or the Proportional Integral Derivative (PID) controller, Fuzzy logic Controllers (FLC) and the Artificial Neural Network (ANN) based controllers have been developed to manage the torque and speed control of the SRM. Another trending method of control involves the optimal tuning of the traditional PI or the PID controller with modern computer based algorithms. The off line tuning techniques like Fuzzy Logic, or the ANN, the Genetic Algorithm (GA) and on line tuning techniques like the Particle Swarm Optimization (PSO) based tuning of the PID controller has also been demonstrated [21-23]. III. Materials and Method The block diagram of proposed bridgeless Luo Converter based Switched Reluctance motor drive system has been appeared in figure 1. This proposed framework is then taken by a single phase supply taken after by filter and Bridgeless-Luo (PL) converts to an SRM motor drive. The BL-Luo converter is considered to be a pre-controller of an in-built power factor to work with the DICM (Discontinuous Inductor Current Mode). By changing the DC link Voltage of proposed Luo Converter the speed of the SRM motor is significantly controlled.
Figure 1 : Block Diagram of proposed Bridgeless LUO Converter Figure 1.demonstrates the block diagram of the proposed framework. The SRM is worked with DC power which is drawn from a bridgeless LUO converter, utilized as Power Factor Corrected rectifier that is sustained from a single phase AC utility power supply. The subtle elements of the bridgeless LUO converter based PFC rectifier are given in the accompanying subsections. 3.1 Design of proposed PFC Bridgeless-Luo Converter
Lf Dn1
Lo1
SW1 Cf
AC SUPPLY
Dpi
LOAD
Lo2
SW2
Dn
Dp
Li1
Li2
C1
C2 CD
Figure 2: Proposed PFC BL-Luo Converter β Circuit Diagram The proposed, PFC BL-Luo converter is arranged into two sections which incorporate the task among
the positive and negative half cycles of the supply voltage and the total switching cycle. The following Figure 2. Shows the circuit diagram of proposed BL-Luo Converter. Figure. 3 and 4 separately demonstrates the PFC BL-Luo converter function for the positive and negative half-cycle of input voltage separately.
Figure 3: Circuit Diagram of Positive Voltage Action
Figure 4: Circuit Diagram of Negative Voltage Action As appeared in the figure. 3 switch SW1 Li1 and Lo1 and diodes Dp and DP1 direct the positive half-cycle of the supply voltage. In a similar way, passing SW2, inductances Li2 and Lo2 and diodes Dn and Dn1 lead the negative half-cycle of the supply voltage as shown in Figure.4.
Figure5: Output Waveforms of Vs,iLi1 ,iLi2 ,iLo1 ,iLo2 and Vc1 , Vc2
The variety of different components are shown in Figure.5 for example the corresponding waveforms, supply voltage, input inductor currents (iLi1 andiLi2 output inductor current (iLo1 andiLo2 ) and the middle capacitor's voltage (Vc1 πππ Vc2 ) amid finish cycle of supply voltage. 3.2 Modes of operation in bridgeless Luo converter In addition the following figures 6, 7 and 8 demonstrate power factor correction function in Bridgeless Luo Switch between a positive half-cycle of supply voltage and a full switching period.
Figure 6: Mode I Operation Mode I: As appeared in the figure. 6, when the switch SW1 is turned on, the inductor on the information side(iLi1 ) stores vitality based on the passage of a current (iLi ) through it and the inductor (iLi1 ) furthermore, the energy stored in the transition capacitor (C1) is exchanged at the DC side capacitor (Cd) and the inductor at the output side (Lo1). Thus, the voltage on the median transverse capacitor (Vc1 ) decreases, while the current in the output inductance (iLo1 )) and the DC interface voltage (Vdc) are extended as shown in the figure. 9
Figure 7: Mode II Operation Mode II: As appeared in Figure. 7, when SW1has been turned off, the input side inductor (πΏi1 ) exchanges its energy to the middle of the capacitor (C1) through diode π·p1. Hence, the current πLi1 diminishes till it achieves zero, while the voltage crosswise over middle of the middle capacitor (πC1 ) increments as appeared in Figure. 9. DC interface capacitor (Cd) gives the expected vitality to the Load. Thus DC connect voltage πdC lessens in this method of activity.
Figure8: Mode III Operation Mode III: As appeared in the figure. 8, no energy was left in the input inductor (πΏi1 ) ie πLi1 current ends in zero and goes into discontinuous conduction mode of the activity. The middle of the capacitor and the inductance πΆa output (πΏo1 ) are released; Therefore πC1 voltage current of ππΏπ1 and are decreased when DC and DC voltage connect πdC increases in this task method appeared in the figure. The task is rewritten when the switch SW1has been turned once more.
Figure9: Waveforms of Modes of operation In the same manner, by negative half-cycle of the supply voltage πΏi2 and πΏo2 of the inductor, a capacitor diode and intermediate π·n1 , πΆ2 conduct to achieve a desired operation 3.3 The Zeigler Nicholas First Method of tuning the PI controller. The Zeigler Nicholas (ZN) first method of tuning the PI controller is also known as the reaction curve method. From the reaction curve obtained, two quantities a and b are found and from these two quantities and by using an empirical law the values of Kp and Ki are acquired. For a given load torque the speed of the SRM is a function of the operating voltage and operating DC link voltage is controllable by controlling the duty cycle used in the PWM drive system used for sequentially energizing the phases of the SRM. Thus the DC link voltage becomes the controlled variable and the duty cycle becomes the manipulated variable. To plot the reaction curve between the DC link voltage and the duty cycle a transfer function is derived as follows. The transfer function of an approximated model of the PFC- LUO converter is given in equation (1). The transfer function between the duty cycle and the DC link voltage is estimated. DC link Voltage = 1.746e05 s + 4.542e08-----------------------------
(1)
Figure 10.The Matlab SIMULIK setup to get the Reaction curve. The transfer function is used to get the reaction curve. The reaction curve is obtained by applying a step input with the step change happening from 0 to 0.5. The reaction curve is as shown in figure 11.
Figure 11. The reaction curve obtained between the DC link voltage and the step duty cycle. The ZN tuning procedure is a traditional procedure in which the reaction is first drawn. The curve, starting from origin has a concave segment followed by a convex segment. The point of change from the concave portion to the convex portion in the reaction curve is called the point of inflexion. A tangent is drawn through the point of inflexion and this tangent intercepts the x and the y axes and also the line drawn to the Y axes by extending the level of steady state. With reference to the diagram in figure 11, the values obtained for Kp, and Ki. 3.4 PSO based tuning of the PI controller The Particle Swarm Optimization is a heuristic search algorithm inspired by the social behavior of certain swarm of birds or insects. Each member of the swarm community 'interacts' with the other members of the community and updates its position, at the end of certain number of iterations all the member particles point to the same solution contained in the search space. The search space is the virtual space contained within the 'n' dimensional space. Each particle participating in the search operation is assigned with a vector, called the potential 'solution vector', with the number of elements of the vector equal to the number of dimensions of the search space. To start with, each particle is assigned with random values for their respective solution vectors. The initialization of the vectors for all member particles should be random and within the allowable limits of the search space. In a typical PI tuning controller technique the objective is to achieve a minimum or the maximum value of the performance index under consideration. For example in this the Integral Square Error (ISE) is the performance index of the objective function which is framed with the intention of reducing the ISE. At the end of each iteration, the solution vector of each of the particle will be updated. If the present iteration is not satisfactory for a particular particle then that particle will update its past best value. After updating each of the particles with the best solution of the particle selected in the objective function Velocity vector is arrived as per equations (2) and (3) for each of the particle to displace the solution vector of particle into a new position within the search space. πππ = π(πΊ) + π£ππ + π1 β ππππ1ππ β (ππππ π‘ππ β πππ) + π2 β ππππ2ππ β (ππππ π‘ β πππ) (2) π π‘+1 = π π‘ + ππππ‘+1
(3)
Where gbest = global best value, pbest = population best, Vid = Input of converter C1,C2 = Converterβs capacitor. π π‘+1 = Previous iteration π π‘ = Updated iteration ππππ‘+1 = Evaluated Objective Function
After altering the position of all the particles by using the velocity vector corresponding to each of the particles in respect of the objection function is estimated. The process repeats iteration until all the particles arrive at nearly the same position with the admissible error. The velocity vector for each particle is calculated by considering the personal best of the particle, the globally best particle and two random numbers attributed to the social behavior and personal behavior that has a relationship to the global search feature and the local search feature. Since the inception of the PSO many modifications have been made to the basic PSO algorithm. Table 1: Kp and Ki Evaluation
Method of tuning
Gain parameter -Kp
Gain parameter -Ki
ZN Method
0.1
1.2
PSO Method
0.124
1.43
However along with this basic PSO algorithm the two random numbers are used. The kp and ki values as found from the ZN method and the PSO method have been tabulated in Table 1. IV. Results and Discussion The description of the MATLAB SIMULINK based simulation and the hardware based experimental setup built around a 1 Hp 220 V, 8 /6 type SRM has been presented for this section..
12a.Simulated waveforms of source voltage and current.
12b. The FFT Analysis of the source current. Figure 12: Simulated waveforms of Front end diode rectifier. Figure 13 shows the simulation result for the SRM fed by front end diode rectifier. The FFT waveform of the source current has high THD value compared to that of the FFT of the source current when driven with a bridgeless LUO converter. The dc supply fed by BL- LUO converter produces input current with THD value of 8.26% as shown in figure 14c.
12c. Simulated waveforms of Torque produced by the SRM
Figure 13: Simulated waveforms of Phase Shifted MOSFET current Figure 13 shows the waveform circuit arrangement of the PFC LUO converter. The PFC LUO converter is fed from a single phase 230V 50 Hz utility power supply. A virtual ground is created with respect to which the output DC voltage is derived. The two MOSFETS that come in series with the phase and the neutral wires each conduct for half cycle when the switch is forward biased. The additional inductors on the output side provide filtering action making the DC output voltage pure and free from ripple. The special feature of this configuration
is that while applying the switching pulses it is not necessary to check zero crossing and relevantly apply the switching pulses to the particular MOSFET that is getting the conductive polarity for the cycle. Instead the switching pulses at the appropriate switching frequency of 20 KHz with the required duty cycle as supplied by the PI controller, is applied to the gates of both the MOSFETs but only that MOSFET that is appropriately biased in each cycle conducts. In figure 13 the first wave is that of the periodic current pulses train of near sinusoidal distribution through MOSFET 1 and the second wave is that of the periodic current pulses train of near sinusoidal distribution through MOSFET 2. The third waveform is that of the switching pulses that are applied in unison for both the MOSFETs simultaneously.
a)
Simulated waveforms of Source side Voltage and Current without filter
b) Simulated waveforms of Source side Voltage and Current with filter
c)
FFT Analysis of the Source Current Figure 14: Source side performance analysis When the PFC based BL-LUO is in operation the source current is sinusoidal and is in phase with the
source voltage. The power factor of the source current is unity. The source voltage and the source current without filter is shown in figure 14.a.,The source voltage and the source current without filter is shown in figure 14.b.and with a front end LC filter the source current becomes free from harmonics as shown in figure 14.c
Figure 15.Simulated waveforms of torque produced by SRM driven by the DC output of the Bridgeless LUO converter The PFC LUO converter gives a negative voltage output with respect to the virtual ground line. The transient and steady state voltage output of the converter and the load current are shown in figure 15. Although there are more energy storage elements, because of the large value of the capacitor across the output terminals the transient characteristics suggest first order nature that helps the design controller easy.
Figure 16. The transient and steady state DC link voltage and current The above figure 16 .shows the transient and steady state DC link voltage and current of proposed PSO based SRM drive system. The output voltage of the converter supplies 180V steady value at stable condition.
Figure 17.The response of the control system or a change in speed command happening at 2 sec.
A PI Controller was designed with the Zeigler Nicholas tuned PI controller and then the PI controller was tuned with the PSO technique. The results obtained with the PSO tuned PI controller is shown in figure 17. The performance comparison of the two controllers is shown in table 2. Table 2. Statistical Performance of tuning of Tuned PI Controller
Tuning
Overshoot (RPM)
Transient Time(ms)
Integral Square Error(ISE) RPM
Speed (RPM)
ZN
18
12
1240
1440
PSO
10
8
560
1405
Performance analysis 1600 1400 1200 1000 800 600 400 200 0 -200O V E R S H OTORTA N( RSPI EMN)T R E S P O N S E ( M ISS)E
ZN PSO
SPEED
Figure 18: Performance analysis The SRM was first set to run at 1200 RPM and the speed command was changed to 1400 RPM at time 2 seconds. The observed results are shows in figure 19 and tabulated in table 2. As compared with ZN method the proposed PSO was produce perfect result for every working condition.
Figure 19: Hardware setup of Luo Converter
The above figure 19 shows the hardware model of proposed system. An experimental setup has been made to validate the proposed idea of driving the SRM from a PFC rectifier of the Bridgeless LUO type. The circuit arrangement of the bridgeless Luo converter implemented in hardware is the same as shown in figure 19.
Figure 20. The position sensor output Figure 20 gives the position sensor output. The position sensor has two bits output. As the motor shaft rotates the position sensor gives a sequence of two bit data as given in figure 20.
Figure 21.The sequential activation of the four phases of the SRM. Based on position sensor output the PIC microcontroller gives the sequence of switching signals to the four phases of SRM. The sequence of activation captured at the output port of controller is shown in the figure 21. In order that each phase is activated only during the positive slope of the inductance profile a delay is introduced in turning on and the switched are turned off a specific time as programmed. This delay and advance are observable from the waves given in figure 22. The current through each of the four phases are presented in figure 22.
Figure 22. The current response of each phase winding in SRM In figure 22.It can be seen that the SRM motor phase windings current in all the 4 phases are displayed as if having a 200 mV. It is actually the output of four shunts that are of resistance 0.01 Ohm. Therefore the current is in each phase is 200mV/0.01 = 200 / 100 = 2.5A.
Figure 23. The AC source current with diode bridge rectifier powered SRM drive The source current from the single phase AC source drawn by a conventional Diode Bridge Converter circuit was observed to be as shown 24. The FFT analysis of the source current is given in figure 23.
Figure 24. The FFT of the source current With reference to wave shapes given in figures 24 and 26 it can be concluded that the BL-LUO converter provides a dc source to the SRM driver with improved power quality and this is confirmed with the FFT details as given in figures 23 and 25.
Figure 25. The source current observed with the BLLUO converter driving the 8/6 SRM drive
a) The source side voltage and current
b) voltage drop across the clamping diodes D1 and D2.
Figure 26: Source side voltage, current and voltage drop The above figure 26 shows the source side voltage, current and voltage drop result of proposed PSO tuned PI controller.
Figure 27: The waveform and spectrum of the source current with the bridgeless LUO converter The above figure 27 shows the waveform and spectrum of the source current with the bridgeless LUO converter of proposed PSO tuned PI controller as compared with ZN tuned PI the PSO tuned PI delivered perfect result for every working condition. v. Conclusion In this work a novel PFC corrected bridgeless Luo converter has been developed for driving the 8/6 SRM with a split DC power supply. The speed regulation of the SRM has been carried out using a ZN and PSO based PI tuned controller that controls the duty cycle of the BL-LUO converter thereby controlling the DC link voltage. The source current drawn from a single phase AC source exhibited improved power quality as compared to a conventional rectifier based drive for the SRM. The proposed idea has been validated using simulation in the MATLAB SIMULINK environment and experimental verification. As compared with ZN method the proposed PSO based PI tuned method gives perfect results of transient response in 8ms, peak overshoot value for 10rpm, ISE is 560 rpm and achieved the THD of 8.26%.
Conflict of interest The speed regulation of the SRM has been carried out using a ZN and PSO based PI tuned controller that controls the duty cycle of the BL-LUO converter thereby controlling the DC link voltage. The source current drawn from a single phase AC source exhibited improved power quality as compared to a conventional rectifier based drive for the SRM.
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BIBLIOGRAPHY
Ms.R.Kalai Selvi has received her B.E degree in Electrical and Electronics Engineering in 2000 from The Indian Engineering College Vadakkangulam and received her M.E. degree in Power Electronics and Drives in 2009 from Government College of Engineering Tirunelveli she is working as an Associate Professor in Electrical and Electronics Engineering in PET Engineering College, Vallioor, His teaching experience was nearly 15-16 years. Her research interests are Power Electronics, Artificial Intelligence, and electrical machines
Dr. R Suja Mani Malar has received her B.E degree in Electrical and Electronics Engineering in 1998 from Mananonmanium Sundardar University and received her M.E. degree in Power System Engineering from Annamalai University in 2000 and Ph.D degree in faculty of Electrical Engineering in 2010 from Anna University, Chennai. She is working as Professor and Head of the department in Electrical and Electronics Engineering in DMI College of Engineering Palanchur Chennai Her teaching experience was nearly 22 years Her research interests are Power System Control, Control System and Artificial Intelligence. She has contributed more than 20 papers in several reputed Journals and Conferences.
A Bridgeless Luo Converter Based Speed Control Of Switched Reluctance Motor Using Particle Swarm Optimization (Pso) Tuned Proportional Integral (Pi) Controller R Kalai Selvi , R Suja Mani Malar PII: DOI: Reference:
S0141-9331(19)30661-1 https://doi.org/10.1016/j.micpro.2020.103039 MICPRO 103039
To appear in:
Microprocessors and Microsystems
Received date: Revised date: Accepted date:
3 December 2019 12 February 2020 14 February 2020
Please cite this article as: R Kalai Selvi , R Suja Mani Malar , A Bridgeless Luo Converter Based Speed Control Of Switched Reluctance Motor Using Particle Swarm Optimization (Pso) Tuned Proportional Integral (Pi) Controller, Microprocessors and Microsystems (2020), doi: https://doi.org/10.1016/j.micpro.2020.103039
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A BRIDGELESS LUO CONVERTER BASED SPEED CONTROL OF SWITCHED RELUCTANCE MOTOR USING PARTICLE SWARM OPTIMIZATION (PSO) TUNED PROPORTIONAL INTEGRAL (PI) CONTROLLER Kalai Selvi.R1 Suja Mani Malar.R2 Associate Professor, 2Professor& Vice-Principal, 1 Department of Electrical & Electronics Engineering, Vallioor, Tirunelveli 2 DMI College of Engineering, Palanchur, Chennai, Tamil Nadu, India. [email protected] 1
Abstract: Motors are essential parts of each moving equipments that is used for various sorts of moving applications. There are a few kinds of motors accessible for different types of industrial applications, But compared to all types of motors the advantages of Switched Reluctance Motor (SRM) in low and medium power applications has ended up being much effective than the other kinds of motors considering the variables like high flux thickness per unit volume, high effectiveness, low electromagnetic obstruction and low maintenance requirements. This work proposes a bridgeless based Luo converter fed Switched Reluctance Motor drive utilizing Particle Swarm Optimization (PSO) tuned Proportional Integral (PI) controller. The PI tuned converter gives high proficiency, high power thickness, and small structure of the motor driver. The accomplished yield voltages of the proposed converter are connected to SRM motor. The SRM here is chosen for the drive because of its minimal effort and simple development. The proposed Luo converter based SRM drive framework have been approved through simulation utilizing Matlab/ Simulink design. The simulation results validate the Power Factor Correction (PFC) activity with reduced output current THD underneath 9%, according to the given IEEE standard. Keywords: Switched Reluctance Motor, Power Factor Correction, Particle swarm optimization, Total Harmonic Distortion, Bridgeless Luo Converter. 1.
Introduction
The Switched Reluctance Motor is a kind of electric motor that keeps running by reluctance torque. Switched Reluctance Motor is electromagnetic and electro-dynamic hardware which convert electrical energy into mechanical energy. It gives high dependability; at steady power it provides an electric range, low fabricating cost, good dynamic reaction, and ruggedness and fault resistance. The switched reluctance motor drives are discovering application in high volume apparatuses and modern applications which can take significantly preferred standpoint of their qualities with high starting torque. The torque is formed by the sequence action of poles. The PFC converters give the power factor according to power quality standards for low power equipment such as IEC 61000-3-2.Additionally, the present forming lessens the input current THD which enhances the present correction factor. Many single-stage PFC converter topologies are accounted for in the literature. Three working modes are explored to work these PFC converters, for example, Continuous Conduction Mode (CCM), Discontinuous Conduction Mode (DCM) and Critical Conduction Mode (CRM). The constant inductor current in CCM offers low input current swell and lessened Electromagnetic Interference (EMI). Electromagnetic Interference encounters hard switching, as inductor current stays constant all through the switching time frame. In CRM of activity, PFC converters accomplish zero current of power switch and zero current for the diode. However, switching frequency fluctuating over a wide range is the negative mark related with CRM, which results in decrease in productivity and complexity in Electro Magnetic Field (EMF) channel outline. In late, the
transition techniques are quickly formed and DC-DC converters have a lot of divisions. Dr. Fang Lin remarkable arrangement has been created by the DC / DC converters, including LUO converter, positive/negative/double output LUO converters over the amount of 100 novel propagation. A LUO converter is broadly used because the voltage has its inherent properties such as the lift, super lift and ultra-lift literature. Among them, the super-lift LUO converter is said to be exceptionally based on the fact that the voltage switch gain is higher. The voltage lift (VL) process is commonly used in electronic circuit strategy. Along with the improvement of the transformation system, the Super-Lift (SL) strategy is more powerful than the voltage lift system. SRMs require energy converters to control the succession of the stator windings. Generally SRM motor converters have two switches at each stage. These SRM current waveforms are highly adaptable and compulsive controls, and the most astounding number of switches. The converter circuit additionally comprises of low pass LC passive filter. The LC passive filter gives change in the Distortion Power Factor (DPF), as the outline of filter capacitor is made to give the required stage move to PFC. In the mean time, this passive filter additionally offers low impedance for the switching harmonic, without considering the supply side information. II. Literature Survey The Switched Reluctance Motor (SRM) is a single excited system in which the magnetic flux responsible for producing the torque is produced by the excitation of a single coil at a time [1]. No other magnetic fields are involved in the dynamics of the machine. Therefore, the SRM uses neither permanent magnets nor the principle of electromagnetic induction. The stator of the SRM consists of wound discrete pole type with 6 or 8 poles much similar to the conventional DC motors [2]. The rotor of the salient pole structure and typically the rotor poles are formed by laminated cores with shapes so designed to form the salient poles. The number of stator poles are not equal to the number of rotor poles [3- 7].The rotor poles do not carry any winding, which depends on the weight, inertia and exhibits low frictional losses. The SRM does not exhibit high hysteresis, eddy current and copper losses like other motors and hence it is highly efficient and is suitable in high speed applications. Although simple in construction the SRM is not an easy to drive machine like the squirrel cage induction motor or the conventional DC motors. The phases of the SRM, or in other words the poles of the stator in the SRM are to be energized, which is based on Hall Effect or an Infrared Slot sensor based position sensor. SRM needs the support of power electronics circuit for routing the electrical power to the machine and need some digital electronics methods for controlling. To develop the closed loop speed controller a digital microprocessor or micro controller like the PIC Micro controller is required [8-10]. There are two major drawbacks with the SRM. The first issue is the ripple that is contained in the torque. Because of sequential switching of the stator poles one after the other and since there exists a dead time between the energizing of each of the stator coils there is a drop in torque produced during every transition period [11]. Further because of the intermittent switching of the stator coils, the power drawn from the main power supply is also intermittent [12]. If the source is derived from a three phases or single phase AC utility supply the source currents exhibit rich harmonics. Exhaustive research has been carried out and is still going on to improve the quality of torque produced and the quality of the source current, when power is drawn from the utility AC power supply [13-15]. Research in certain distinguishable prime directions are going on to explore the various possibilities of using the modern design tools like the finite element analysis or by using the various other electromagnetic design software tools, that could lead to improved torque production capabilities with less torque ripple [16]. Shaping of the pole faces is also considered as a feasible method to improve torque quality [17]. The other direction of research is to find the possibilities of novel circuit topologies [18] for driving the SRM and this direction of research, also contributed significantly with many topological variations that usually happens with the type of the available sources like DC source from rectifiers, renewable sources like the solar PV panel, the fuel cell sources and batteries. Controlled and uncontrolled rectifiers followed by DC to DC converters of the generic type or the advanced converters like CUK, SEPIC or the LUO converters have also been tried with the SRM. The matrix converter is another option when the source is the multiphase type AC.
The other direction of research has been the development of various control schemes [19, 20]. Right from the PI or the Proportional Integral Derivative (PID) controller, Fuzzy logic Controllers (FLC) and the Artificial Neural Network (ANN) based controllers have been developed to manage the torque and speed control of the SRM. Another trending method of control involves the optimal tuning of the traditional PI or the PID controller with modern computer based algorithms. The off line tuning techniques like Fuzzy Logic, or the ANN, the Genetic Algorithm (GA) and on line tuning techniques like the Particle Swarm Optimization (PSO) based tuning of the PID controller has also been demonstrated [21-23]. III. Materials and Method The block diagram of proposed bridgeless Luo Converter based Switched Reluctance motor drive system has been appeared in figure 1. This proposed framework is then taken by a single phase supply taken after by filter and Bridgeless-Luo (PL) converts to an SRM motor drive. The BL-Luo converter is considered to be a pre-controller of an in-built power factor to work with the DICM (Discontinuous Inductor Current Mode). By changing the DC link Voltage of proposed Luo Converter the speed of the SRM motor is significantly controlled.
Figure 1 : Block Diagram of proposed Bridgeless LUO Converter Figure 1.demonstrates the block diagram of the proposed framework. The SRM is worked with DC power which is drawn from a bridgeless LUO converter, utilized as Power Factor Corrected rectifier that is sustained from a single phase AC utility power supply. The subtle elements of the bridgeless LUO converter based PFC rectifier are given in the accompanying subsections. 3.1 Design of proposed PFC Bridgeless-Luo Converter
Lf Dn1
Lo1
SW1 Cf
AC SUPPLY
Dpi
LOAD
Lo2
SW2
Dn
Dp
Li1
Li2
C1
C2 CD
Figure 2: Proposed PFC BL-Luo Converter β Circuit Diagram The proposed, PFC BL-Luo converter is arranged into two sections which incorporate the task among
the positive and negative half cycles of the supply voltage and the total switching cycle. The following Figure 2. Shows the circuit diagram of proposed BL-Luo Converter. Figure. 3 and 4 separately demonstrates the PFC BL-Luo converter function for the positive and negative half-cycle of input voltage separately.
Figure 3: Circuit Diagram of Positive Voltage Action
Figure 4: Circuit Diagram of Negative Voltage Action As appeared in the figure. 3 switch SW1 Li1 and Lo1 and diodes Dp and DP1 direct the positive half-cycle of the supply voltage. In a similar way, passing SW2, inductances Li2 and Lo2 and diodes Dn and Dn1 lead the negative half-cycle of the supply voltage as shown in Figure.4.
Figure5: Output Waveforms of Vs,iLi1 ,iLi2 ,iLo1 ,iLo2 and Vc1 , Vc2
The variety of different components are shown in Figure.5 for example the corresponding waveforms, supply voltage, input inductor currents (iLi1 andiLi2 output inductor current (iLo1 andiLo2 ) and the middle capacitor's voltage (Vc1 πππ Vc2 ) amid finish cycle of supply voltage. 3.2 Modes of operation in bridgeless Luo converter In addition the following figures 6, 7 and 8 demonstrate power factor correction function in Bridgeless Luo Switch between a positive half-cycle of supply voltage and a full switching period.
Figure 6: Mode I Operation Mode I: As appeared in the figure. 6, when the switch SW1 is turned on, the inductor on the information side(iLi1 ) stores vitality based on the passage of a current (iLi ) through it and the inductor (iLi1 ) furthermore, the energy stored in the transition capacitor (C1) is exchanged at the DC side capacitor (Cd) and the inductor at the output side (Lo1). Thus, the voltage on the median transverse capacitor (Vc1 ) decreases, while the current in the output inductance (iLo1 )) and the DC interface voltage (Vdc) are extended as shown in the figure. 9
Figure 7: Mode II Operation Mode II: As appeared in Figure. 7, when SW1has been turned off, the input side inductor (πΏi1 ) exchanges its energy to the middle of the capacitor (C1) through diode π·p1. Hence, the current πLi1 diminishes till it achieves zero, while the voltage crosswise over middle of the middle capacitor (πC1 ) increments as appeared in Figure. 9. DC interface capacitor (Cd) gives the expected vitality to the Load. Thus DC connect voltage πdC lessens in this method of activity.
Figure8: Mode III Operation Mode III: As appeared in the figure. 8, no energy was left in the input inductor (πΏi1 ) ie πLi1 current ends in zero and goes into discontinuous conduction mode of the activity. The middle of the capacitor and the inductance πΆa output (πΏo1 ) are released; Therefore πC1 voltage current of ππΏπ1 and are decreased when DC and DC voltage connect πdC increases in this task method appeared in the figure. The task is rewritten when the switch SW1has been turned once more.
Figure9: Waveforms of Modes of operation In the same manner, by negative half-cycle of the supply voltage πΏi2 and πΏo2 of the inductor, a capacitor diode and intermediate π·n1 , πΆ2 conduct to achieve a desired operation 3.3 The Zeigler Nicholas First Method of tuning the PI controller. The Zeigler Nicholas (ZN) first method of tuning the PI controller is also known as the reaction curve method. From the reaction curve obtained, two quantities a and b are found and from these two quantities and by using an empirical law the values of Kp and Ki are acquired. For a given load torque the speed of the SRM is a function of the operating voltage and operating DC link voltage is controllable by controlling the duty cycle used in the PWM drive system used for sequentially energizing the phases of the SRM. Thus the DC link voltage becomes the controlled variable and the duty cycle becomes the manipulated variable. To plot the reaction curve between the DC link voltage and the duty cycle a transfer function is derived as follows. The transfer function of an approximated model of the PFC- LUO converter is given in equation (1). The transfer function between the duty cycle and the DC link voltage is estimated. DC link Voltage = 1.746e05 s + 4.542e08-----------------------------
(1)
Figure 10.The Matlab SIMULIK setup to get the Reaction curve. The transfer function is used to get the reaction curve. The reaction curve is obtained by applying a step input with the step change happening from 0 to 0.5. The reaction curve is as shown in figure 11.
Figure 11. The reaction curve obtained between the DC link voltage and the step duty cycle. The ZN tuning procedure is a traditional procedure in which the reaction is first drawn. The curve, starting from origin has a concave segment followed by a convex segment. The point of change from the concave portion to the convex portion in the reaction curve is called the point of inflexion. A tangent is drawn through the point of inflexion and this tangent intercepts the x and the y axes and also the line drawn to the Y axes by extending the level of steady state. With reference to the diagram in figure 11, the values obtained for Kp, and Ki. 3.4 PSO based tuning of the PI controller The Particle Swarm Optimization is a heuristic search algorithm inspired by the social behavior of certain swarm of birds or insects. Each member of the swarm community 'interacts' with the other members of the community and updates its position, at the end of certain number of iterations all the member particles point to the same solution contained in the search space. The search space is the virtual space contained within the 'n' dimensional space. Each particle participating in the search operation is assigned with a vector, called the potential 'solution vector', with the number of elements of the vector equal to the number of dimensions of the search space. To start with, each particle is assigned with random values for their respective solution vectors. The initialization of the vectors for all member particles should be random and within the allowable limits of the search space. In a typical PI tuning controller technique the objective is to achieve a minimum or the maximum value of the performance index under consideration. For example in this the Integral Square Error (ISE) is the performance index of the objective function which is framed with the intention of reducing the ISE. At the end of each iteration, the solution vector of each of the particle will be updated. If the present iteration is not satisfactory for a particular particle then that particle will update its past best value. After updating each of the particles with the best solution of the particle selected in the objective function Velocity vector is arrived as per equations (2) and (3) for each of the particle to displace the solution vector of particle into a new position within the search space. πππ = π(πΊ) + π£ππ + π1 β ππππ1ππ β (ππππ π‘ππ β πππ) + π2 β ππππ2ππ β (ππππ π‘ β πππ) (2) π π‘+1 = π π‘ + ππππ‘+1
(3)
Where gbest = global best value, pbest = population best, Vid = Input of converter C1,C2 = Converterβs capacitor. π π‘+1 = Previous iteration π π‘ = Updated iteration ππππ‘+1 = Evaluated Objective Function
After altering the position of all the particles by using the velocity vector corresponding to each of the particles in respect of the objection function is estimated. The process repeats iteration until all the particles arrive at nearly the same position with the admissible error. The velocity vector for each particle is calculated by considering the personal best of the particle, the globally best particle and two random numbers attributed to the social behavior and personal behavior that has a relationship to the global search feature and the local search feature. Since the inception of the PSO many modifications have been made to the basic PSO algorithm. Table 1: Kp and Ki Evaluation
Method of tuning
Gain parameter -Kp
Gain parameter -Ki
ZN Method
0.1
1.2
PSO Method
0.124
1.43
However along with this basic PSO algorithm the two random numbers are used. The kp and ki values as found from the ZN method and the PSO method have been tabulated in Table 1. IV. Results and Discussion The description of the MATLAB SIMULINK based simulation and the hardware based experimental setup built around a 1 Hp 220 V, 8 /6 type SRM has been presented for this section..
12a.Simulated waveforms of source voltage and current.
12b. The FFT Analysis of the source current. Figure 12: Simulated waveforms of Front end diode rectifier. Figure 13 shows the simulation result for the SRM fed by front end diode rectifier. The FFT waveform of the source current has high THD value compared to that of the FFT of the source current when driven with a bridgeless LUO converter. The dc supply fed by BL- LUO converter produces input current with THD value of 8.26% as shown in figure 14c.
12c. Simulated waveforms of Torque produced by the SRM
Figure 13: Simulated waveforms of Phase Shifted MOSFET current Figure 13 shows the waveform circuit arrangement of the PFC LUO converter. The PFC LUO converter is fed from a single phase 230V 50 Hz utility power supply. A virtual ground is created with respect to which the output DC voltage is derived. The two MOSFETS that come in series with the phase and the neutral wires each conduct for half cycle when the switch is forward biased. The additional inductors on the output side provide filtering action making the DC output voltage pure and free from ripple. The special feature of this configuration
is that while applying the switching pulses it is not necessary to check zero crossing and relevantly apply the switching pulses to the particular MOSFET that is getting the conductive polarity for the cycle. Instead the switching pulses at the appropriate switching frequency of 20 KHz with the required duty cycle as supplied by the PI controller, is applied to the gates of both the MOSFETs but only that MOSFET that is appropriately biased in each cycle conducts. In figure 13 the first wave is that of the periodic current pulses train of near sinusoidal distribution through MOSFET 1 and the second wave is that of the periodic current pulses train of near sinusoidal distribution through MOSFET 2. The third waveform is that of the switching pulses that are applied in unison for both the MOSFETs simultaneously.
a)
Simulated waveforms of Source side Voltage and Current without filter
b) Simulated waveforms of Source side Voltage and Current with filter
c)
FFT Analysis of the Source Current Figure 14: Source side performance analysis When the PFC based BL-LUO is in operation the source current is sinusoidal and is in phase with the
source voltage. The power factor of the source current is unity. The source voltage and the source current without filter is shown in figure 14.a.,The source voltage and the source current without filter is shown in figure 14.b.and with a front end LC filter the source current becomes free from harmonics as shown in figure 14.c
Figure 15.Simulated waveforms of torque produced by SRM driven by the DC output of the Bridgeless LUO converter The PFC LUO converter gives a negative voltage output with respect to the virtual ground line. The transient and steady state voltage output of the converter and the load current are shown in figure 15. Although there are more energy storage elements, because of the large value of the capacitor across the output terminals the transient characteristics suggest first order nature that helps the design controller easy.
Figure 16. The transient and steady state DC link voltage and current The above figure 16 .shows the transient and steady state DC link voltage and current of proposed PSO based SRM drive system. The output voltage of the converter supplies 180V steady value at stable condition.
Figure 17.The response of the control system or a change in speed command happening at 2 sec.
A PI Controller was designed with the Zeigler Nicholas tuned PI controller and then the PI controller was tuned with the PSO technique. The results obtained with the PSO tuned PI controller is shown in figure 17. The performance comparison of the two controllers is shown in table 2. Table 2. Statistical Performance of tuning of Tuned PI Controller
Tuning
Overshoot (RPM)
Transient Time(ms)
Integral Square Error(ISE) RPM
Speed (RPM)
ZN
18
12
1240
1440
PSO
10
8
560
1405
Performance analysis 1600 1400 1200 1000 800 600 400 200 0 -200O V E R S H OTORTA N( RSPI EMN)T R E S P O N S E ( M ISS)E
ZN PSO
SPEED
Figure 18: Performance analysis The SRM was first set to run at 1200 RPM and the speed command was changed to 1400 RPM at time 2 seconds. The observed results are shows in figure 19 and tabulated in table 2. As compared with ZN method the proposed PSO was produce perfect result for every working condition.
Figure 19: Hardware setup of Luo Converter
The above figure 19 shows the hardware model of proposed system. An experimental setup has been made to validate the proposed idea of driving the SRM from a PFC rectifier of the Bridgeless LUO type. The circuit arrangement of the bridgeless Luo converter implemented in hardware is the same as shown in figure 19.
Figure 20. The position sensor output Figure 20 gives the position sensor output. The position sensor has two bits output. As the motor shaft rotates the position sensor gives a sequence of two bit data as given in figure 20.
Figure 21.The sequential activation of the four phases of the SRM. Based on position sensor output the PIC microcontroller gives the sequence of switching signals to the four phases of SRM. The sequence of activation captured at the output port of controller is shown in the figure 21. In order that each phase is activated only during the positive slope of the inductance profile a delay is introduced in turning on and the switched are turned off a specific time as programmed. This delay and advance are observable from the waves given in figure 22. The current through each of the four phases are presented in figure 22.
Figure 22. The current response of each phase winding in SRM In figure 22.It can be seen that the SRM motor phase windings current in all the 4 phases are displayed as if having a 200 mV. It is actually the output of four shunts that are of resistance 0.01 Ohm. Therefore the current is in each phase is 200mV/0.01 = 200 / 100 = 2.5A.
Figure 23. The AC source current with diode bridge rectifier powered SRM drive The source current from the single phase AC source drawn by a conventional Diode Bridge Converter circuit was observed to be as shown 24. The FFT analysis of the source current is given in figure 23.
Figure 24. The FFT of the source current With reference to wave shapes given in figures 24 and 26 it can be concluded that the BL-LUO converter provides a dc source to the SRM driver with improved power quality and this is confirmed with the FFT details as given in figures 23 and 25.
Figure 25. The source current observed with the BLLUO converter driving the 8/6 SRM drive
a) The source side voltage and current
b) voltage drop across the clamping diodes D1 and D2.
Figure 26: Source side voltage, current and voltage drop The above figure 26 shows the source side voltage, current and voltage drop result of proposed PSO tuned PI controller.
Figure 27: The waveform and spectrum of the source current with the bridgeless LUO converter The above figure 27 shows the waveform and spectrum of the source current with the bridgeless LUO converter of proposed PSO tuned PI controller as compared with ZN tuned PI the PSO tuned PI delivered perfect result for every working condition. v. Conclusion In this work a novel PFC corrected bridgeless Luo converter has been developed for driving the 8/6 SRM with a split DC power supply. The speed regulation of the SRM has been carried out using a ZN and PSO based PI tuned controller that controls the duty cycle of the BL-LUO converter thereby controlling the DC link voltage. The source current drawn from a single phase AC source exhibited improved power quality as compared to a conventional rectifier based drive for the SRM. The proposed idea has been validated using simulation in the MATLAB SIMULINK environment and experimental verification. As compared with ZN method the proposed PSO based PI tuned method gives perfect results of transient response in 8ms, peak overshoot value for 10rpm, ISE is 560 rpm and achieved the THD of 8.26%.
Conflict of interest The speed regulation of the SRM has been carried out using a ZN and PSO based PI tuned controller that controls the duty cycle of the BL-LUO converter thereby controlling the DC link voltage. The source current drawn from a single phase AC source exhibited improved power quality as compared to a conventional rectifier based drive for the SRM.
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BIBLIOGRAPHY
Ms.R.Kalai Selvi has received her B.E degree in Electrical and Electronics Engineering in 2000 from The Indian Engineering College Vadakkangulam and received her M.E. degree in Power Electronics and Drives in 2009 from Government College of Engineering Tirunelveli she is working as an Associate Professor in Electrical and Electronics Engineering in PET Engineering College, Vallioor, His teaching experience was nearly 15-16 years. Her research interests are Power Electronics, Artificial Intelligence, and electrical machines
Dr. R Suja Mani Malar has received her B.E degree in Electrical and Electronics Engineering in 1998 from Mananonmanium Sundardar University and received her M.E. degree in Power System Engineering from Annamalai University in 2000 and Ph.D degree in faculty of Electrical Engineering in 2010 from Anna University, Chennai. She is working as Professor and Head of the department in Electrical and Electronics Engineering in DMI College of Engineering Palanchur Chennai Her teaching experience was nearly 22 years Her research interests are Power System Control, Control System and Artificial Intelligence. She has contributed more than 20 papers in several reputed Journals and Conferences.