Self-adaptive dynamic reactive power compensation method for photovoltaic grid-connection inverter

Abstract

The invention provides a self-adaptive dynamic reactive power compensation method for photovoltaic grid-connection inverter. The method comprises the following steps: 1) acquiring direct current voltage command value (marked in the figure) and the current command value (marked in the figure) under voltage-current double-loop control; 2) disconnecting the DC-voltage outer-loop control of the double ring control; 3) establishing a new outer ring control for the power grid voltage including an outer ring control circuit based on a self-adaptive controller and an inner control circuit based on a PIR controller; 4) disconnecting the outer ring control circuit based on the self-adaptive controller when the power grid voltage is recovered to normal within a preset time; and 5) assigning the direct current voltage command value (marked in the figure) to the reference voltage of an MPPT controller in the direct current voltage outer ring control; and conducting another time the outer ring control of the direct current voltage of the power grid and the inner ring control of the grid-connection current. Compared with the prior art, the self-adaptive dynamic reactive power compensation method for photovoltaic grid-connection inverter of the invention is capable of switching between different strategies quickly when the voltage of a power grid is detected to have dropped so as to ensure photovoltaic grid-connection.

Description

technical field [0001] The invention relates to the field of photovoltaic grid-connected power generation, in particular to an adaptive dynamic reactive power compensation method for a photovoltaic grid-connected inverter. Background technique [0002] As the proportion of photovoltaic installed capacity in the power grid continues to increase, the impact of photovoltaic grid-connected inverters on the power grid is becoming increasingly prominent. When the grid voltage drops to a certain value, conventional small-scale photovoltaic power generation systems are disconnected from the grid to protect the photovoltaic system safely, which is possible in grids with a low proportion of photovoltaic power generation. However, for large-scale photovoltaic systems connected to the grid, the off-grid of the photovoltaic system may cause the collapse of the grid voltage and frequency, which will cause greater harm to the stability of the grid. Therefore, photovoltaic power plants mus...

AI Technical Summary

Problems solved by technology

The existing problems are: 1) The dynamic reactive current support sent by the photovoltaic grid-connected inverter to the grid during the asymmetric drop of the grid voltage is not considered too much; It has good control performance; however, when the grid asymmetry fault is serious, the filter introduced by the current positive and negative sequence separation will increase the delay of the control system, and the moment when the grid voltage fault occurs and recovers, there will usually be a current shock, which greatly affects the transient state of the system performance, which reduces the low voltage ride-through capability of the photovoltaic system

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