Summary: Distributed photovoltaic power plants have seen rapid development due to their short construction time, mature technology, and clear returns. However, the issue of abnormal power factor caused by photovoltaic grid connection is also becoming increasingly prominent. This article analyzes the reasons for the failure of low-voltage reactive power compensation devices and proposes an effective solution for the reduction of power factor after the integration of distributed photovoltaic power plants into the distribution network.
Keywords: Distributed Photovoltaics; Power Factor; Low-Voltage Reactive Compensation
1. Overview
As the profitability of distributed photovoltaic power generation increases, small and medium-sized distributed photovoltaic power plants are rapidly developing in some enterprises. They typically operate on a self-consumption and surplus electricity-to-grid model, connecting to the enterprise internal grid at low-voltage AC 380V. The majority of the electricity generated by photovoltaics is consumed by the enterprise itself, achieving good economic benefits. However, abnormal power factor issues often arise after the photovoltaic systems are connected to the enterprise's distribution network.
Photovoltaic grid connection point is located at the front of the incoming line cabinet; the photovoltaic grid connection point is situated at the back end of the load.
2. Power Factor Anomaly Issue Analysis
The required active power is 100kW, reactive power is 50kvar, and the current power factor is 0.89. When the photovoltaic system is turned off, the capacitor, due to step-by-step compensation, can only provide about 30kvar of reactive power, failing to fully compensate. The grid supplies 100kW of active power and 20kvar of reactive power, raising the power factor to 0.98, resulting in better compensation. When the photovoltaic system is turned on, 80kW of active power is supplied by the photovoltaic, while the capacitor provides 30kvar of reactive power. In this case, the grid supplies 20kW of active power and 20kvar of reactive power, causing the power factor to drop to 0.7. The site can improve the accuracy of reactive power compensation by using small-capacity capacitors for fine compensation or an SVG (Static Var Generator) to resolve this issue.
3. Reactive Compensation Device
3.1 ANSVC Reactive Compensation Device
The ANSVC reactive power compensation device is suitable for systems with a frequency of 50Hz and a voltage of 0.4KV. The ANSVC low-voltage reactive power compensation device is connected in parallel throughout the entire power supply system and can control the switching of power capacitors for compensation based on the changes in the power factor of the grid load. The principle is as follows: The ANSVC low-voltage reactive power compensation device collects current and voltage signals through CTs, calculates the switching scheme for capacitors using the reactive power compensation controller, and controls the switching of each group of power capacitors through switching switches.
3.2 ANSVG Static Var Generator Unit
Equipped with reactive power compensation, three-phase current balancing, and voltage stabilization functions, it can also filter harmonics up to the 5th, 7th, 11th, and 13th orders. It features automatic operation detection, measurement supervision, and setpoint adjustment capabilities. It is equipped with intelligent heat dissipation and variable speed control functions. It has dynamic expansion capabilities, supports plug-and-play for easy replacement, and includes overvoltage shutdown, overvoltage lockout, undervoltage shutdown, and overtemperature alarm protection functions.
- Conclusion
Many factors can cause abnormal power factor after a distributed photovoltaic power station is connected to the user's distribution network. It requires a comprehensive analysis considering technical and economic aspects to find a good reactive power compensation solution. It is recommended that the installed capacity of the photovoltaic power station not exceed 80% of the special transformer capacity of the connected factory area, and to try to move the connection point before the incoming line transformer, which can avoid the problem of frequent switching of the capacitor group caused by the connection of the photovoltaic power station.
