- Email: [email protected]
The Hokuto mega-solar project
ARTICLE IN PRESS Solar Energy Materials & Solar Cells 93 (2009) 1091–1094
Contents lists available at ScienceDirect
Solar Energy Materials & Solar Cells journal homepage: www.elsevier.com/locate/solmat
The Hokuto mega-solar project Hiroo Konishi , Ryo Tanaka, Toshiyuki Shiraki Energy Business Headquarters, NTT FACILITIES INC., Granparktower, 3-4-1 Shibaura, Minato-ku, Tokyo 108-0023, Japan
a r t i c l e in fo
abstract
Article history: Received 10 January 2008 Received in revised form 1 December 2008 Accepted 11 December 2008 Available online 24 January 2009
Solar generation systems are one of the measures for reducing global warming. An installed capacity target of solar generation systems in our country will be set 4.82 GW in 2010, while the total installed capacity is still 1.92 GW in 2007. About 80% of the systems are mainly residential use and each is very small. Constructions of some large-scale solar generation systems will be expected and intensive development of related technologies are urgent. The New Energy and Industrial Technology Development Organization (NEDO) advertised for consignment research business ‘‘Verification of Grid Stabilization with Large-scale Photovoltaic (PV) Power Generation Systems’’ in 2006. The verification tests are carried out in two sites of Hokuto City, Yamanashi Prefecture and Wakkanai City, Hokkaido. The outlines and the developing targets and some of studying results of the Hokuto mega-solar project (HMSP) are introduced in this paper. & 2008 Elsevier B.V. All rights reserved.
Keywords: PCS Operating method PV module Support structure Simulation technique
1. Hokuto mega-solar project
2. Developing target and results
The one-line diagram and monitoring system of Hokuto megasolar project (HMSP) is shown in Fig. 1. About 600 kW of photovoltaic (PV) modules will be installed in FY2007 and those are connected to 6.6 kV power grids. After that, about 1.2 MW of PV modules will be installed in FY2009. At the final stage, about 100 kW PV modules will be added in FY2010, total generating facilities will be about 2 MW and all are connected to 66 kV power grids and monitored. In order to connect large-scale PV modules to extra-highvoltage power grids, we develop a 400 kW large-scale powerconditioning system (PCS) for interface. To reduce affecting voltage fluctuations of utility power grids due to power fluctuations inherent in PV systems, a suppression control function is included in the PCS. When the voltage of power grids decreases due to faults, the PCS have a ride-through ability against voltage drops within 40%. A harmonic voltage suppression function is also developed. We will study the effectiveness and usefulness of those developing items using digital simulations and a miniature model of HMSP before verifying in the field. Additional R&D of the HSMP contains life cycle assessment (LCA) and evaluating environmental effects in HMSP and making a guideline to be designed in large-scale PV systems. The R&D period is 5 years from FY2006 to FY2010. After completing R&D and verification tests, the HMSP system is scheduled to handle to Hokuto City and put into operation.
2.1. 400 kW PCS
Corresponding author. Tel.: +81 354445066; fax: +81 354445630.
E-mail address: [email protected] (H. Konishi). 0927-0248/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.solmat.2008.12.020
To connect large-scale PV systems to existing extra-highvoltage power grids, a large-scale power-conditioning system has been developed. The 400 kW PCS is consisted of a large-scale inverter and two 200 kW choppers. The choppers have a maximum power point tracking (MPPT) function of the PV modules. The PCS operates continuously in greater than 60% of AC voltage and suppresses AC voltage fluctuations due to output power fluctuations inherent in the PV modules by controlling reactive power. Connection of three PCSs is shown in Fig. 2. They are connected to 6.6 kV distribution line with both the 1st and the 2nd stages of PV modules in parallel via a 6.6 kV/420 V transformer. The 6.6 kV distribution line is connected to ultrahigh-voltage power grids via a 66/6.6 kV transformer. Specifications and developing targets are listed in Table 1. The PCS is introduced from 2nd stage. Two operation methods for three PCSs are thought. One is integrated operating method in which they are operated the same as if they were one large capacity of inverter. Another is an individual operating method in which each inverter operates individually responding to the PV generation output PVo. When the PVo is small, all three PCSs are not operated but selected responding to the PVo. The operating method is shown in Fig. 3. First, a PCS-1 (master-PCS) is started and operated responding to the PVo until it becomes 400 kW. After that a PCS-2 (slave-PCS) is started by 200 kW and output of PCS-1 is decreased to 200 kW. When the PVo increases, output of PCS-2 is increased responding to an increase of the PVo, while output of PCS-1 is kept 200 kW.
ARTICLE IN PRESS 1092
H. Konishi et al. / Solar Energy Materials & Solar Cells 93 (2009) 1091–1094
Fig. 1. Configuration of Hokuto mega-solar power generation.
PV module
6.6kV/210V AC/DC (10kW×60) 6.6kV/210V
3rd stage (100kW)
AC/DC (10kW×10)
Transmission Line 6.6kV/420V 66kV/6.6kV
PV module
Connecting point
Chopper (200kW) Chopper (200kW)
PCS-1 PCS-2
PCS-3 Fig. 2. System configuration.
Table 1 Specifications and developing targets of PCS. AC voltage Converter transformer DC voltage Input DC voltage Switching freq. Conversion efficiency Control functions
PCS-1+PCS-2+PCS-3 PVo 0.8
PCS-1+PCS-2 PCS-2
PCS-3
0.4 PCS-1 0
AC/DC (400kW)
2nd stage (1,200kW)
1.2 PCS output (MW)
1st stage (600kW)
420 V ac710% Transformer-less 650 V dc 230–600 Vdc 4–6 kHz 495% from 30% to 100% /MPPT (by choppers) /Suppression of DVac /Continuous operation /Suppression of low-order harmonics
0
0.4 0.8 PV generation output PVo (MW)
1.2
Fig. 3. Individual operation of three PCSs.
When the PVo becomes 600 kW, output of PCS-2 is kept 400 kW constant and the output of PCS-1 is increased again responding to the increase of the PVo until it becomes 400 kW. When the PVo becomes 800 kW, a PCS-3 (another slave-PCS) is started by 200 kW and output of PCS-1 is decreased to 200 kW. When the PVo increases further, the output of PCS-3 is increased responding to an increase of the PVo, while output of PCS-1 is kept 200 kW. When the PVo becomes 1000 kW, output of PCS-3 is kept 400 kW constant. The output of PCS-1 is increased responding to the increase of the PVo until it becomes 400 kW. When the PVo decreases, three PCSs are operated oppositely above. PCS output is evaluated for above two PCSs’ operating methods in consideration of the PV generating output characteristics in HMSP and efficiency of the developing large-scale PCS. Statistical PV generation output data in Kofu city by Japan Weather Association (JWA) is shown in Fig. 4. These data are data of Kofu that exists in the nearest to Hokuto city of the data that can be acquired. According to the data, the band width of the PVo becoming less than 30% is small and is less than 20% of the total. Fig. 5 shows efficiency to which the PCS under development is assumed. The efficiency is presumed from 30% to 100% of PCS output with 95% or more.
ARTICLE IN PRESS H. Konishi et al. / Solar Energy Materials & Solar Cells 93 (2009) 1091–1094
Distribution of kWh (%)
Accumulative value of kWh (%)
1093
Table 3 Selected advanced PV modules and systems in 1st stage.
Accumulation 100
20
80
15
Distribution
Classification
Manufacture
Installed capacity (kW)
Remarks
Mono-crystal Si
Sharp Sanyo Isofoton GE-energy Sun powder
30 30 30 30 50
High efficiency High efficiency Large area Chemical processing Back wiring
Poly-crystal Si
Sharp Kyocera Mitsubishi Suntech Day 4 energy Kaneka Fujipream Schott Solar
30 100 30 30 30 40 20 30 30 32
High efficiency High efficiency Tandem, high efficiency Large area No bus-bar Single/multi-layer Spherical concentrating Ribbon processing Compound semiconductor Concentrating and tracking
60
10
40
5
20
0
~10 ~20 ~30 ~40 ~50 ~60 ~70 ~80 ~90 ~100 Band width of PV generation output (%)
0
Fig. 4. PV generation output in Kofu city. a-Si Spherical Ribbon type CIS Tracking
Efficiency of PCS (%) 100
Sharp
80 60 40 20 0
0
10
20
30 40 50 60 70 Output of PCS (%)
80 90 100
Fig. 5. Efficiency of PCS.
Joint fitting
Table 2 Comparison of Po calculation.
Steel pipe
Method
Integrated
Individual
Po (%)
95.6
96.1
Screwed pipe
Fig. 6. Image of PV support structures.
Output power of the PCSs Po in two operating methods is calculated and compared using a following equation. X Po ¼ ðZk P k Þ (1) k
where Zk is the efficiency of PCS in band width k of Pvo, Pk the distribution in band width k of Pvo, and k the band width. Table 2 shows the calculation results of Po, the individual operating method is 0.5% higher than the integrated operating method. As deference is little, the integrated operating method is taken in HMSP because of simplicity of the operating method and reliability improvement by it. The larger, the PV generating output for low output power and the lower, the efficiency for lower output of PCS, the difference becomes large. Fig. 7. Photograph of PV modules at the site.
2.2. PV module and support structure Performance evaluation of several kinds of PV modules and systems are carried out. Table 3 shows mainly selected advanced PV modules and systems installed in 1st stage (FY2007). The total capacity is about 600 kW. Some of their performance characteristics are compared with those of Wakkanai site. Support structure for PV modules are designed in consideration of 3R (reduce cost, reuse, recycle). Screwed pipes are buried and jointed with stainless steel pipes as shown in Fig. 6. It depicts image of support structures for PV modules. Every PV support structure consists of steel pipes and joint fittings to combine. They can be reused. Fig. 7 shows a photograph of the PV modules at the site.
2.3. Life cycle assessment and environmental effects LCA of large-scale PV systems will be evaluated by calculating CO2 reduction and energy income and outgo using net data concerning of mining, manufacturing, transportation, construction, operation and maintenance, and removal. Related data are gathering. About environmental effects, following items have been investigated and watched. (1) Habits of animals and plants: the field mice designated to be protected in the red-data-book of Yamanashi prefecture have been found out in the site.
ARTICLE IN PRESS H. Konishi et al. / Solar Energy Materials & Solar Cells 93 (2009) 1091–1094
Transformer (66kV/6.6kV) Ultra high voltage system 66kV
A
B
P=1.2MW
Transformer (6.6kV/420V) C P
Line
a PCS
P=10MW
P=5MW
500 400 300 200 100 0 -100 0.56 -200 -300 -400 -500
V420
1094
0.57
0.58
0.6
0.59
0.8 line voltage V420 containing 2.1% of 5th harmonics voltage
0.6
b
0.4
0.04% 0.2 /1.2MW 0.0
1000 500
A Connecting point
B Line
C PCS terminal
V420
Δ Vac (%)
1.0
Fig. 8. Simulation results of voltage fluctuation.
0 0.56 -500
0.57
0.58
0.59
0.6
-1000
time [s] Analysis of Impedance characteristics Transformer (66kV/6.6kV)
With harmonics suppression control
c
1st stage (600kW)
1000
V420
500
2nd stage (1,200kW)
0 0.56 -500
Impedance ?
0.57
0.58
0.59
0.6
-1000
[Ω]
time [s] Frequency vs. AC system impedance 0.6 0.54Ω (550Hz) 0.4 0.2 0
0
1000 2000 frequency [Hz]
3000
Fig. 9. Calculation results of AC system impedance.
They will be chased and watched after this. (2) Contents of water in a pond near the site. (3) Atmosphere: temperature, humidity, direction and velocity of wind, air pressure, and solar irradiation at chosen 5 spots in the site will be measured in every 10 min. (4) Pollution: mining dust, noise and vibrations are watched through construction of the site.
Without harmonics suppression control Fig. 10. Simulation results of harmonics suppression methods.
fluctuations zero at a connecting point A shown in Fig. 8 regardless of the fluctuations of PV generation output. The voltage fluctuations due to the PV fluctuations are 0.04% and very small because connecting power grids are very large and strong. So effects of voltage fluctuation suppression function of the PCS are evaluated at the point of the PCS terminal C. (2) Study of harmonics: Fig. 9 shows calculation results of harmonics impedance. A precise layout of AC and DC system of 1st stage is used to calculate a harmonics impedance. Seen from a connecting point of 2nd stage, 11th order of harmonics impedance shows high. It is found that we take care of 11th order harmonics in connecting 2nd stage of PV generation system. Fig. 10 shows simulation results of effect of harmonics suppression function of the PCS. In the figure, waveform (a) shows 420 V line voltage containing 2.1% of 5th harmonics, (b) and (c) show with and without the suppression control of PCS, respectively.
2.4. Simulation technique 3. Conclusions To make a guidebook offering in design a large-scale PV generation system, simulation techniques will be developed. They are analysis of power system, analysis and suppression of AC voltage fluctuation, harmonics analysis, LCA and so on. As for LCA, we need to develop analysis programs and we are under framing. (1) Analysis of power system: Fig. 8 shows voltage fluctuations due to the fluctuations of PV generation output considering the power grids conditions. The PCS controls to keep voltage
The outlines and the developing targets and some of studying results of HMSP are introduced. The 1st stage construction has just started.
Acknowledgment We thank to NEDO for various kinds of assistance.
Contents lists available at ScienceDirect
Solar Energy Materials & Solar Cells journal homepage: www.elsevier.com/locate/solmat
The Hokuto mega-solar project Hiroo Konishi , Ryo Tanaka, Toshiyuki Shiraki Energy Business Headquarters, NTT FACILITIES INC., Granparktower, 3-4-1 Shibaura, Minato-ku, Tokyo 108-0023, Japan
a r t i c l e in fo
abstract
Article history: Received 10 January 2008 Received in revised form 1 December 2008 Accepted 11 December 2008 Available online 24 January 2009
Solar generation systems are one of the measures for reducing global warming. An installed capacity target of solar generation systems in our country will be set 4.82 GW in 2010, while the total installed capacity is still 1.92 GW in 2007. About 80% of the systems are mainly residential use and each is very small. Constructions of some large-scale solar generation systems will be expected and intensive development of related technologies are urgent. The New Energy and Industrial Technology Development Organization (NEDO) advertised for consignment research business ‘‘Verification of Grid Stabilization with Large-scale Photovoltaic (PV) Power Generation Systems’’ in 2006. The verification tests are carried out in two sites of Hokuto City, Yamanashi Prefecture and Wakkanai City, Hokkaido. The outlines and the developing targets and some of studying results of the Hokuto mega-solar project (HMSP) are introduced in this paper. & 2008 Elsevier B.V. All rights reserved.
Keywords: PCS Operating method PV module Support structure Simulation technique
1. Hokuto mega-solar project
2. Developing target and results
The one-line diagram and monitoring system of Hokuto megasolar project (HMSP) is shown in Fig. 1. About 600 kW of photovoltaic (PV) modules will be installed in FY2007 and those are connected to 6.6 kV power grids. After that, about 1.2 MW of PV modules will be installed in FY2009. At the final stage, about 100 kW PV modules will be added in FY2010, total generating facilities will be about 2 MW and all are connected to 66 kV power grids and monitored. In order to connect large-scale PV modules to extra-highvoltage power grids, we develop a 400 kW large-scale powerconditioning system (PCS) for interface. To reduce affecting voltage fluctuations of utility power grids due to power fluctuations inherent in PV systems, a suppression control function is included in the PCS. When the voltage of power grids decreases due to faults, the PCS have a ride-through ability against voltage drops within 40%. A harmonic voltage suppression function is also developed. We will study the effectiveness and usefulness of those developing items using digital simulations and a miniature model of HMSP before verifying in the field. Additional R&D of the HSMP contains life cycle assessment (LCA) and evaluating environmental effects in HMSP and making a guideline to be designed in large-scale PV systems. The R&D period is 5 years from FY2006 to FY2010. After completing R&D and verification tests, the HMSP system is scheduled to handle to Hokuto City and put into operation.
2.1. 400 kW PCS
Corresponding author. Tel.: +81 354445066; fax: +81 354445630.
E-mail address: [email protected] (H. Konishi). 0927-0248/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.solmat.2008.12.020
To connect large-scale PV systems to existing extra-highvoltage power grids, a large-scale power-conditioning system has been developed. The 400 kW PCS is consisted of a large-scale inverter and two 200 kW choppers. The choppers have a maximum power point tracking (MPPT) function of the PV modules. The PCS operates continuously in greater than 60% of AC voltage and suppresses AC voltage fluctuations due to output power fluctuations inherent in the PV modules by controlling reactive power. Connection of three PCSs is shown in Fig. 2. They are connected to 6.6 kV distribution line with both the 1st and the 2nd stages of PV modules in parallel via a 6.6 kV/420 V transformer. The 6.6 kV distribution line is connected to ultrahigh-voltage power grids via a 66/6.6 kV transformer. Specifications and developing targets are listed in Table 1. The PCS is introduced from 2nd stage. Two operation methods for three PCSs are thought. One is integrated operating method in which they are operated the same as if they were one large capacity of inverter. Another is an individual operating method in which each inverter operates individually responding to the PV generation output PVo. When the PVo is small, all three PCSs are not operated but selected responding to the PVo. The operating method is shown in Fig. 3. First, a PCS-1 (master-PCS) is started and operated responding to the PVo until it becomes 400 kW. After that a PCS-2 (slave-PCS) is started by 200 kW and output of PCS-1 is decreased to 200 kW. When the PVo increases, output of PCS-2 is increased responding to an increase of the PVo, while output of PCS-1 is kept 200 kW.
ARTICLE IN PRESS 1092
H. Konishi et al. / Solar Energy Materials & Solar Cells 93 (2009) 1091–1094
Fig. 1. Configuration of Hokuto mega-solar power generation.
PV module
6.6kV/210V AC/DC (10kW×60) 6.6kV/210V
3rd stage (100kW)
AC/DC (10kW×10)
Transmission Line 6.6kV/420V 66kV/6.6kV
PV module
Connecting point
Chopper (200kW) Chopper (200kW)
PCS-1 PCS-2
PCS-3 Fig. 2. System configuration.
Table 1 Specifications and developing targets of PCS. AC voltage Converter transformer DC voltage Input DC voltage Switching freq. Conversion efficiency Control functions
PCS-1+PCS-2+PCS-3 PVo 0.8
PCS-1+PCS-2 PCS-2
PCS-3
0.4 PCS-1 0
AC/DC (400kW)
2nd stage (1,200kW)
1.2 PCS output (MW)
1st stage (600kW)
420 V ac710% Transformer-less 650 V dc 230–600 Vdc 4–6 kHz 495% from 30% to 100% /MPPT (by choppers) /Suppression of DVac /Continuous operation /Suppression of low-order harmonics
0
0.4 0.8 PV generation output PVo (MW)
1.2
Fig. 3. Individual operation of three PCSs.
When the PVo becomes 600 kW, output of PCS-2 is kept 400 kW constant and the output of PCS-1 is increased again responding to the increase of the PVo until it becomes 400 kW. When the PVo becomes 800 kW, a PCS-3 (another slave-PCS) is started by 200 kW and output of PCS-1 is decreased to 200 kW. When the PVo increases further, the output of PCS-3 is increased responding to an increase of the PVo, while output of PCS-1 is kept 200 kW. When the PVo becomes 1000 kW, output of PCS-3 is kept 400 kW constant. The output of PCS-1 is increased responding to the increase of the PVo until it becomes 400 kW. When the PVo decreases, three PCSs are operated oppositely above. PCS output is evaluated for above two PCSs’ operating methods in consideration of the PV generating output characteristics in HMSP and efficiency of the developing large-scale PCS. Statistical PV generation output data in Kofu city by Japan Weather Association (JWA) is shown in Fig. 4. These data are data of Kofu that exists in the nearest to Hokuto city of the data that can be acquired. According to the data, the band width of the PVo becoming less than 30% is small and is less than 20% of the total. Fig. 5 shows efficiency to which the PCS under development is assumed. The efficiency is presumed from 30% to 100% of PCS output with 95% or more.
ARTICLE IN PRESS H. Konishi et al. / Solar Energy Materials & Solar Cells 93 (2009) 1091–1094
Distribution of kWh (%)
Accumulative value of kWh (%)
1093
Table 3 Selected advanced PV modules and systems in 1st stage.
Accumulation 100
20
80
15
Distribution
Classification
Manufacture
Installed capacity (kW)
Remarks
Mono-crystal Si
Sharp Sanyo Isofoton GE-energy Sun powder
30 30 30 30 50
High efficiency High efficiency Large area Chemical processing Back wiring
Poly-crystal Si
Sharp Kyocera Mitsubishi Suntech Day 4 energy Kaneka Fujipream Schott Solar
30 100 30 30 30 40 20 30 30 32
High efficiency High efficiency Tandem, high efficiency Large area No bus-bar Single/multi-layer Spherical concentrating Ribbon processing Compound semiconductor Concentrating and tracking
60
10
40
5
20
0
~10 ~20 ~30 ~40 ~50 ~60 ~70 ~80 ~90 ~100 Band width of PV generation output (%)
0
Fig. 4. PV generation output in Kofu city. a-Si Spherical Ribbon type CIS Tracking
Efficiency of PCS (%) 100
Sharp
80 60 40 20 0
0
10
20
30 40 50 60 70 Output of PCS (%)
80 90 100
Fig. 5. Efficiency of PCS.
Joint fitting
Table 2 Comparison of Po calculation.
Steel pipe
Method
Integrated
Individual
Po (%)
95.6
96.1
Screwed pipe
Fig. 6. Image of PV support structures.
Output power of the PCSs Po in two operating methods is calculated and compared using a following equation. X Po ¼ ðZk P k Þ (1) k
where Zk is the efficiency of PCS in band width k of Pvo, Pk the distribution in band width k of Pvo, and k the band width. Table 2 shows the calculation results of Po, the individual operating method is 0.5% higher than the integrated operating method. As deference is little, the integrated operating method is taken in HMSP because of simplicity of the operating method and reliability improvement by it. The larger, the PV generating output for low output power and the lower, the efficiency for lower output of PCS, the difference becomes large. Fig. 7. Photograph of PV modules at the site.
2.2. PV module and support structure Performance evaluation of several kinds of PV modules and systems are carried out. Table 3 shows mainly selected advanced PV modules and systems installed in 1st stage (FY2007). The total capacity is about 600 kW. Some of their performance characteristics are compared with those of Wakkanai site. Support structure for PV modules are designed in consideration of 3R (reduce cost, reuse, recycle). Screwed pipes are buried and jointed with stainless steel pipes as shown in Fig. 6. It depicts image of support structures for PV modules. Every PV support structure consists of steel pipes and joint fittings to combine. They can be reused. Fig. 7 shows a photograph of the PV modules at the site.
2.3. Life cycle assessment and environmental effects LCA of large-scale PV systems will be evaluated by calculating CO2 reduction and energy income and outgo using net data concerning of mining, manufacturing, transportation, construction, operation and maintenance, and removal. Related data are gathering. About environmental effects, following items have been investigated and watched. (1) Habits of animals and plants: the field mice designated to be protected in the red-data-book of Yamanashi prefecture have been found out in the site.
ARTICLE IN PRESS H. Konishi et al. / Solar Energy Materials & Solar Cells 93 (2009) 1091–1094
Transformer (66kV/6.6kV) Ultra high voltage system 66kV
A
B
P=1.2MW
Transformer (6.6kV/420V) C P
Line
a PCS
P=10MW
P=5MW
500 400 300 200 100 0 -100 0.56 -200 -300 -400 -500
V420
1094
0.57
0.58
0.6
0.59
0.8 line voltage V420 containing 2.1% of 5th harmonics voltage
0.6
b
0.4
0.04% 0.2 /1.2MW 0.0
1000 500
A Connecting point
B Line
C PCS terminal
V420
Δ Vac (%)
1.0
Fig. 8. Simulation results of voltage fluctuation.
0 0.56 -500
0.57
0.58
0.59
0.6
-1000
time [s] Analysis of Impedance characteristics Transformer (66kV/6.6kV)
With harmonics suppression control
c
1st stage (600kW)
1000
V420
500
2nd stage (1,200kW)
0 0.56 -500
Impedance ?
0.57
0.58
0.59
0.6
-1000
[Ω]
time [s] Frequency vs. AC system impedance 0.6 0.54Ω (550Hz) 0.4 0.2 0
0
1000 2000 frequency [Hz]
3000
Fig. 9. Calculation results of AC system impedance.
They will be chased and watched after this. (2) Contents of water in a pond near the site. (3) Atmosphere: temperature, humidity, direction and velocity of wind, air pressure, and solar irradiation at chosen 5 spots in the site will be measured in every 10 min. (4) Pollution: mining dust, noise and vibrations are watched through construction of the site.
Without harmonics suppression control Fig. 10. Simulation results of harmonics suppression methods.
fluctuations zero at a connecting point A shown in Fig. 8 regardless of the fluctuations of PV generation output. The voltage fluctuations due to the PV fluctuations are 0.04% and very small because connecting power grids are very large and strong. So effects of voltage fluctuation suppression function of the PCS are evaluated at the point of the PCS terminal C. (2) Study of harmonics: Fig. 9 shows calculation results of harmonics impedance. A precise layout of AC and DC system of 1st stage is used to calculate a harmonics impedance. Seen from a connecting point of 2nd stage, 11th order of harmonics impedance shows high. It is found that we take care of 11th order harmonics in connecting 2nd stage of PV generation system. Fig. 10 shows simulation results of effect of harmonics suppression function of the PCS. In the figure, waveform (a) shows 420 V line voltage containing 2.1% of 5th harmonics, (b) and (c) show with and without the suppression control of PCS, respectively.
2.4. Simulation technique 3. Conclusions To make a guidebook offering in design a large-scale PV generation system, simulation techniques will be developed. They are analysis of power system, analysis and suppression of AC voltage fluctuation, harmonics analysis, LCA and so on. As for LCA, we need to develop analysis programs and we are under framing. (1) Analysis of power system: Fig. 8 shows voltage fluctuations due to the fluctuations of PV generation output considering the power grids conditions. The PCS controls to keep voltage
The outlines and the developing targets and some of studying results of HMSP are introduced. The 1st stage construction has just started.
Acknowledgment We thank to NEDO for various kinds of assistance.