Access to the distribution network of distributed photovoltaic system to produce the eight affected

Centralized power distribution network generally radially . Steady state of operation , the voltage gradually decreases along the direction of the trend feeders . Connected photovoltaic power , due to the reduced transmission power feeder , so that the load node along the feeder voltage is raised , it may cause some load bus voltage excursion is exceeded, the voltage is raised to the access number of photovoltaic power location and size of the total capacity is closely related .

Under normal circumstances , can be in the low voltage distribution network settings OLTC transformers and voltage regulators and other pressure control equipment , the load node voltage offset control in compliance range. For the distribution network voltage regulation , a reasonable set of photovoltaic power mode of operation is very important. Sunny in the afternoon , the photovoltaic power output is usually large , if the line light loads , photovoltaic power will significantly raise the voltage of the access point .

If the access point is at the end of the feed line , the voltage of the access point is likely to cross the limit , then you must set a reasonable photovoltaic power operating mode , such as the provisions regulating photovoltaic power must be involved in the absorption lines in excess of reactive . Heavy-duty during the night time period , usually without photovoltaic power output , but still provide reactive power , improve the quality of the line voltage . Influence on the voltage photovoltaic power is also reflected in may cause voltage fluctuations and flicker .

Since the power output of photovoltaic solar irradiance with incident and change , it may cause local distribution line voltage fluctuations and flicker, if added together with the load change will cause a greater voltage fluctuation and flicker . Although the actual operation of photovoltaic power did not cause significant voltage fluctuations and flicker, but a large number of grid-connected photovoltaic power access when the access location and capacity for rational planning is still very important.

Usually considered a short circuit in the power distribution network side , the access to the distribution network, the power of the short-circuit current of photovoltaic contribute little , steady-state short-circuit current is generally higher than the rated output current of photovoltaic power is 10% to 20%, short circuit instantaneous current peak PV power inverter with its own storage elements and output control performance related . In the distribution network , plus short-circuit protection fuse overcurrent protection commonly used . For high penetration of photovoltaic power feeder road to short circuit fault occurs , probably due to the vast majority of photovoltaic power supply short-circuit current caused by the feed line can not detect short-circuit fault .

In 1999 , IEA-PVPS-Task-5 ( IEA Technical Working Group in PV ) in Japan, manufacturers have used four different injection control current inverter is connected to a power distribution line of the column adapter, then the transformer other side of the short-circuit tests. Tests showed that the short circuit current did not rise above 2 times before failure , 1 to 2 cycles to isolate a fault . In addition, Japan also a 200kWp photovoltaic power system short-circuit tests , the study found : short-circuit current through the transformer , the current becomes smaller , the transformer overcurrent protection does not operate.

In 2003, the United States NERL ( U.S. National Renewable Energy Laboratory ) has done on distributed power generation and distribution networks of interactions between . Adopt inverter http://www.gridtiepowerinverteronline.com/ way to access the distributed power , simulation prototype based on the 13.2kV ​​medium voltage distribution networks, distributed power capacity is 5MW, research is focused on fusing characteristics . The results show that when the single-phase and three-phase fault in the inverter way to access the distributed power to the small contribution of short circuit current , short-circuit current is mainly from the main network, or even more than 5MW induction motor to provide short-circuit current but also much smaller. Therefore, in order to control the current drawn into the photovoltaic power inverter not contribute to the short-circuit current conclusions.