CN-115313496-B - Energy storage converter grid-connected control method based on sagging control

CN115313496BCN 115313496 BCN115313496 BCN 115313496BCN-115313496-B

Abstract

The invention discloses a sagging control-based energy storage converter grid-connected control method, which comprises the steps of firstly obtaining a power grid voltage phase by using a phase-locked loop and realizing converter grid-connected by current control, then the droop control loop is started, the voltage and the frequency are set as the voltage loop, and finally the phase-locked loop output electric angle is switched into the frequency set integrator output. The method is applicable to grid-connected control of a single converter or grid-connected control of a plurality of converters without a presynchronizing process, and can avoid the problems of control lag and the like caused by the closing delay of a circuit breaker.

Inventors

LIU ZHIBO
ZHANG CHUNXIAO
DU YUNTAO

Assignees

天津瑞源电气有限公司

Dates

Publication Date: 20260512
Application Date: 20220905

Claims (3)

1. The energy storage converter grid-connected control method based on droop control is characterized by comprising the following steps of Collecting power grid voltage and current; Starting a phase-locked loop control module, taking the power grid voltage as the input of the phase-locked loop, and calculating to obtain a power grid angle theta g through the phase-locked loop, wherein the power grid angle theta g is used for realizing coordinate transformation and control of voltage and current; closing a grid-side circuit breaker, and connecting the converter to a power grid; Coordinate transformation is carried out on the three-phase current i a ,i b ,i c at the net side to obtain dq axis components i d and i q , the dq axis currents are set to be 0, and a current controller at the net side is started to control the current at the net side; After the grid-connected operation is stable, giving the voltage loop given u dref and u qref as actual voltage dq axis components u d and u q respectively after a period of time delay, and ensuring that the output of the voltage loop is 0; And starting the droop controller, giving the output voltage of the droop controller as a voltage loop, taking the phase of the moment before switching as the initial phase, and integrating the output frequency to obtain a control angle theta c to finish grid connection of the energy storage converter.
2. The grid-connected control method of an energy storage converter based on droop control according to claim 1, wherein after the droop control is started, a phase reference is generated by using a phase-locked loop output angle θ g as an initial phase.
3. The grid-connected control method of an energy storage converter based on droop control according to claim 2, wherein the droop control controls the converter to output active power and reactive power by adjusting voltage frequency and amplitude respectively, and the droop control expression is that Wherein ω and U are given values of the inverter output angular frequency and voltage amplitude, P and Q are actual active power and reactive power output by the inverter, P 0 and Q 0 are rated output active power and reactive power of the inverter, ω 0 and U 0 are rated angular frequency and voltage amplitude of the inverter, and k p and k q are active and reactive droop coefficients, respectively.

Description

Energy storage converter grid-connected control method based on sagging control Technical Field The invention relates to the technical field of energy storage converter control, in particular to an energy storage converter grid-connected control method based on droop control. Background Along with the development of economy and social progress, the energy demand is increased, but the traditional fossil energy is rapidly developed, the problems of grid connection difficulty and difficult digestion caused by intermittence and fluctuation are more prominent, the development of renewable energy power generation is restricted seriously, and a good development opportunity is brought to the energy storage technology. The droop control enables all distributed power supplies to participate in maintaining the stability of the system frequency and voltage through simulating the power frequency characteristic of the generator set, achieves interconnection-free control of active power and reactive power, is suitable for a micro-grid peer-to-peer control mode, and can avoid adverse effects possibly caused by single main control unit faults on the system performance. The droop control is essentially voltage control, and when the converter is integrated into a power grid or put into parallel connection, if the frequency, the phase or the voltage amplitude is inconsistent with other systems or a large power grid, the forced parallel connection or grid connection can cause large impact current, so that accidents occur. Therefore, the droop control firstly carries out synchronous control before grid connection, and carries out switching-on operation after the presynchronization is finished when the amplitude value and the phase of the grid voltage reach the threshold value. This method requires that a filter capacitor exists on the ac side of the energy storage converter, otherwise ac synchronous control cannot be completed. And then, after the presynchronization is finished, a closing command is issued, and the presynchronization control cannot be accurately stopped to cause delay in control due to certain delay in closing of an actual breaker. Therefore, a reliable and effective grid-connected control method is necessary to be provided, and the energy storage converter can be guaranteed to be connected in a non-impact and rapid mode. Disclosure of Invention The invention aims to provide an energy storage converter grid-connected control method based on droop control. For this purpose, the technical scheme of the invention is as follows: A droop control-based energy storage converter grid-connected control method comprises the following steps of Collecting power grid voltage and current; Starting a phase-locked loop control module, taking the power grid voltage as the input of the phase-locked loop, and calculating to obtain a power grid angle theta g through the phase-locked loop, wherein the power grid angle theta g is used for realizing coordinate transformation and control of voltage and current; closing a grid-side circuit breaker, and connecting the converter to a power grid; Coordinate transformation is carried out on the three-phase current i a,ib,ic at the net side to obtain dq axis components i d and i q, the dq axis currents are set to be 0, and a current controller at the net side is started to control the current at the net side; After the grid-connected operation is stable, giving the voltage loop given u dref and u qref as actual voltage dq axis components u d and u q respectively after a period of time delay, and ensuring that the output of the voltage loop is 0; And starting the droop controller, giving the output voltage of the droop controller as a voltage loop, taking the phase of the moment before switching as the initial phase, and integrating the output frequency to obtain a control angle theta c to finish grid connection of the energy storage converter. Further, after the droop control is started, the phase reference is generated by using the phase-locked loop output angle θ g as an initial phase. Further, the droop control is used for controlling the converter to output active power and reactive power respectively by adjusting the frequency and amplitude of the voltage, and the droop control expression is that Wherein ω and U are given values of the inverter output angular frequency and voltage amplitude, P and Q are actual active power and reactive power output by the inverter, P 0 and Q 0 are rated output active power and reactive power of the inverter, ω 0 and U 0 are rated angular frequency and voltage amplitude of the inverter, and k p and k q are active and reactive droop coefficients, respectively. Compared with the prior art, the energy storage converter grid-connected control method based on sagging control can directly realize grid connection of the converters without a grid-connected presynchronization process, is suitable for single converter grid-connected control or multiple converter g