Reactive voltage control method and system for grid-connected photovoltaic power station

Abstract

The invention discloses a reactive voltage control method and system for a grid-connected photovoltaic power station. A three-layer reactive power control strategy is adopted to coordinate the reactive output between a reactive compensation device and a photovoltaic power generation unit and between inverters of a single photovoltaic power generation unit. Under the control strategy, the reactive voltage support is provided for the power grid; the photovoltaic power station can effectively regulate the power grid voltage; the active loss and the reactive loss of the power grid are minimal on the premise of keeping the power grid voltage within the required range. A photovoltaic array power reduction running strategy is further combined, the stable operation of the power grid is ensured on the premise of maintaining a certain reactive output capacity of the photovoltaic power station. The reactive voltage control method and the system solve the problem that the voltage at the grid-connected point is out of limit, which is caused by the fact that the large-scale photovoltaic power station is connected to the power grid, increase the permeability of the photovoltaic current in the power grid, and improve the stable running performance of the power grid voltage.

Description

technical field [0001] The invention relates to the field of photovoltaic power station control, in particular to a method and system for controlling reactive power and voltage of a grid-connected photovoltaic power station. Background technique [0002] In recent years, with the continuous reduction of photovoltaic system costs and the maturity of photovoltaic grid-connected technology, large-scale photovoltaic power generation has become more and more favored by the international community. Large-scale photovoltaic power plants are generally built in remote areas with abundant solar energy resources. Compared with small and medium-sized photovoltaic systems, solar energy can be used more intensively, and parallel inverters can be controlled and managed. However, as the proportion of photovoltaic power generation in the power grid continues to increase, photovoltaic power needs to be transmitted to the load center over long distances, and the photovoltaic system has an adve...

AI Technical Summary

Problems solved by technology

Among them, the constant power factor cosφ control, when the photovoltaic active output is very small, in order to maintain the power factor unchanged, the photovoltaic system still needs to generate a certain amount of reactive power, which increases the loss of the grid; the cosφ(P) control based on the photovoltaic active output, according to the photovoltaic The power factor value of the active output of the system is changed from C1 to C2 to overcome the shortcomings of cosφ control, but the premise of this control strategy is to assume that the grid-connected point voltage increases with the increase of photovoltaic active output. When the photovoltaic active output is large It happens to be the peak time of the user's power consumption, and the voltage of the grid-connected point does not exceed the limit at this time, and a large amount of reactive power output will bring great losses to the power grid; based on the Q(U) control strategy of the voltage amplitude of the grid-connected point, the absorption or output Reactive power has no direct relationship with photovoltaic active output and load. Compared with cosφ and cosφ(P) control, its control strategy absorbs the lowest total amount of reactive power and reduces power grid losses, but its voltage regulation capability is weak

Images