Grid-connected photovoltaic power station reactive power-voltage control method based on power prediction

Abstract

The invention provides a grid-connected photovoltaic power station reactive power-voltage control method based on power prediction. A photovoltaic AVC system is used to coordinate reactive power adjusting equipment in a grid-connected photovoltaic power station so that grid-connected point voltage control is completed. The method comprises the following steps of based on power prediction data, determining a reactive power loss of the grid-connected photovoltaic power station when grid-connected point voltage adjusting is ended; determining a reactive power adjustment total amount of the grid-connected photovoltaic power station; determining reactive power limits of a photovoltaic inverter and a static reactive power compensation device; carrying out switching control of a parallel compensation capacitor group; and carrying out control on the photovoltaic inverter and the static reactive power compensation device. In the invention, photovoltaic power station control sensitivity is accurately calculated and good reactive power-voltage control precision and a good response speed are possessed; and power prediction and photovoltaic power station AVC system are combined so as to realize segmentation control of a photovoltaic power station capacitor group and good balance between reactive power-voltage control and equipment protection.

Description

technical field [0001] The invention relates to a control method, in particular to a reactive power-voltage control method of a grid-connected photovoltaic power station based on power prediction. Background technique [0002] Solar photovoltaic power generation has the characteristics of randomness, intermittent, periodicity and volatility. As the scale of photovoltaic power generation continues to grow, the impact on grid voltage stability is becoming more and more obvious. Installing a reactive power-voltage automatic control system (hereinafter referred to as photovoltaic AVC system) in a grid-connected photovoltaic power station is an important means to ensure grid voltage stability and reactive power balance. The typical photovoltaic AVC system structure is as follows: figure 1 As shown, the photovoltaic AVC system completes the voltage control of the grid-connected point by coordinating the output of the reactive power adjustment equipment in the photovoltaic power st...

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Problems solved by technology

[0004] (1) The control and coordination of reactive power adjustment equipment is difficult. In theory, photovoltaic inverters and static reactive power compensation equipment have millisecond response speeds, and the switching time of capacitors is also less than 1 second. The speed is greatly affected by the communication method

Especially for independently controlled photovoltaic inverters, if the ring communication is used instead of optical fiber direct connection, the response speed of the inverter is often more than a few seconds, and the traditional control method is prone to overshoot or overshoot of the bus voltage within the specified adjustment time. The problem of improper adjustment

[0005] (2) It is difficult to calculate the total amount of reactive power adjustment. Due to the influence of factors such as reactive power and voltage changes at the grid-connected point and asynchronous measurement data, the system impedance obtained by online calculation based on voltage deviation and reactive power changes often has a large error, resulting in adjustment There is a problem in the total calculation, which affects the response time and control accuracy of the photovoltaic AVC system

Therefore, the capacitor switching operation generally lags behind the voltage change of the grid-connected point of the power station, and causes the reactive power output of the photovoltaic inverter and static reactive power compensation equipment to be high in some periods, affecting power generation efficiency

[0007] (4) The influence of reactive power loss in the power station is less considered. When the overall reactive power of the grid is balanced, one of the important factors affecting the voltage of the grid-connected point of the photovoltaic power station is the reactive power loss in the station. Therefore, the reactive power-voltage adjustment process should be fully Considering the change of reactive power loss in the station, the existing reactive power-voltage control algorithm generally does not take into account the reactive power loss in the station

[0008] (5) Unreasonable application of static var compensation equipment (SVC / SVG / MCR)

On the one hand, it is easy to cause frequent switching of capacitors; on the other hand, it also makes the reactive power demand of the main transformer completely provided by the remote photovoltaic inverter, which increases the line loss to a certain extent

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