Photovoltaic inverter steady-state voltage balance control method and system thereof

Abstract

The invention relates to a photovoltaic inverter steady-state voltage balance control method and a system thereof, and belongs to the photovoltaic power generating control technology field. A virtual synchronous generator model is established according to a principle of conventional synchronous generators of carrying out negative sequence compensation by single-phase exciters, the split-phase control of the internal potential of the virtual synchronous generator model is carried out. The current instruction of the photovoltaic inverter current closed loop control is generated according to the virtual synchronous generator model, and the inverter current closed loop control is used for tracking synchronous generator stator current. The split-phase control of the internal potential of the virtual synchronous generator model is carried out, and then the photovoltaic inverter is automatically used for the reactive power compensation under a working condition of imbalance voltage or negative load of a three-phase power grid, and the supporting of the balance of the grid-connected point voltage is facilitated.

Description

technical field [0001] The invention relates to a photovoltaic inverter steady-state voltage balance control method and system, belonging to the technical field of photovoltaic power generation control. Background technique [0002] The intermittent and random large-scale output fluctuations of distributed photovoltaics determined by the inherent characteristics of solar energy resources will cause large-scale changes in the power flow of the distribution network in the case of grid-connected distributed photovoltaic clusters with high penetration rates. Both the degree and speed of the PV grid-connected point exceed the general load change, which leads to problems such as voltage deviation exceeding the limit and increased voltage fluctuation in the distribution network, and the voltage deviation and fluctuation range of the photovoltaic grid-connected point are higher than that of the distribution network side. Only relying on the distribution network Conventional measures...

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Problems solved by technology

[0002] The intermittent and random large-scale output fluctuations of distributed photovoltaics determined by the inherent characteristics of solar energy resources will cause large-scale changes in the power flow of the distribution network in the case of grid-connected distributed photovoltaic clusters with high penetration rates. Both the degree and speed of the PV grid-connected point exceed the general load change, which leads to problems such as voltage deviation exceeding the limit and increased voltage fluctuation in the distribution network, and the voltage deviation and fluctuation range of the photovoltaic grid-connected point are higher than that of the distribution network side. Only relying on the distribution network Conventional measures such as grid regulation transformer taps and switching shunt capacitors will not be able to meet the overall reactive voltage regulation requirements; on the other hand, the photovoltaic inverter itself has reactive power regulation capabilities. Adaptive control capability and grid friendliness, on the contrary, can improve the reactive power and voltage regulation capability of the distribution network

[0003] At present, distributed photovoltaic voltage and reactive power control methods mainly include three forms: constant reactive power control, power factor control and transient reactive power support control. In practical applications, although the above methods can realize distributed photovoltaic voltage and reactive power control , but because it cannot simulate the working principle of the synchronous generator excitation regulation system, there are defects in the rapidity, accuracy and autonomy of the grid-connected point voltage and reactive power regulation

In order to effectively deal with these defects, a lot of research has been carried out on virtual synchronous generator technology at home and abroad in recent years. Using virtual synchronous generator technology can make the photovoltaic inverter not only regulate the voltage of the grid-connected point in a steady state, but also realize the Dynamic reactive power support of the power grid, but the current research in this area is based on the working condition of three-phase voltage balance, and the potential amplitude is unified control of the three phases. When the power grid or load is asymmetrical, it is impossible to balance the power grid.

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