According to relevant statistics, by the end of June 2020, the cumulative installed capacity of PV power stations in China has exceeded 186GW. With the rapid increase of construction volume and installed capacity, the operation of photovoltaic power generation challenges the existing power grid system. Therefore, the power grid companies are imposing increasingly strict grid connection requirements on new energy power stations are increasingly strict.
Not long ago, a PV power station in Hubei Province was fined by the power grid company for its low power factor. In June, more than 10% of the electricity fee charged to the station is penalty. The power supply company proposed to “increase the number of reactive power compensators and make adjustment to power factor”.
“The problem with non-compliant power factor” has prevented the power stations to gain revenues, so it is urgent to solve this problem.
Based on the field investigation results, the PV power station is equipped with 16Mvar dynamic reactive power compensator so that it is capable of proper power generation in the daytime and supplying power to the grid, with a power factor above 0.98 (as shown on Figure 1). The reverse metering power factor of the power station fully meets the power grid company’s assessment standard of a power factor 0.9. While at night or during rainy days and the PV power station does not generate electricity or very small power is generated (the power generated is smaller than the power consumed in the station), the power grid supplies power to the power station, and the power factor is small (as shown on Figure 2). At this time, the forward metering power factor of the power station fails to meet the power grid company’s assessment standard of a power factor 0.9.
Therefore, the root cause of revenue loss of the power station lies in the factor that the forward metering power factor of the power station fails to meet the applicable standard when the PV power station does not generate electricity or the power generated is small, which results in the factor adjusted electricity fee (penalty) to the PV power station.
The PV power station is with active power about 0.05MW~0.21MW and reactive power demand about 0.2Mvar~0.4Mvar at night, and the existing dynamic reactive power compensator is less capable of small-current output, so there is large output error in case of small reactive power demand at night, and the power factor cannot be guaranteed.
When it is necessary to ensure that the PV power station meets the power grid company’s assessment requirements of a power factor of 0.9 at night, the control accuracy of dynamic reactive power compensator must reach 0.01Mvar, and the minimum current control output is required to be smaller than 1% of the rated capacity, which is much demanding than the 2.5% set forth in the power industry standard Technical Regulation for Distribution Static Synchronous Compensator (DL/T1216-2013).
In the TBEA Sunoasis reactive power compensation solution, the model TSVG-16/35-W-C static var generator is adopted, whose performance fully meets applicable provisions in Technical Rule for Connecting Photovoltaic Power Station to Power Grid. In addition, through algorithm optimization to improve the sampling accuracy, control the injection frequency conversion and improve the small current control accuracy of products and the control accuracy of reactive power at point of common coupling, the power factor of the power station at night is successfully enabled to reach or exceed the assessment requirements of the power grid company, the loss of the power station caused by factor adjusted electricity fee is avoided, and the electricity cost of the power station is saved by more than 11%, thus the income of the new energy power station is guaranteed.
TBEA Sunoasis power quality solution team is committed to exploring the special application conditions of clean energy power generation, intelligent distribution and new energy electric field. Oriented by market demand, the team constantly updates and optimizes products and proposes comprehensive power quality solutions in order to guarantee the safe and economic operation of power grid.