Method for controlling parallel running of micro-grid multi-inverter combination on basis of capacitor voltage differentiation

Abstract

The invention relates to a method for controlling parallel running of a micro-grid multi-inverter combination on the basis of capacitor voltage differentiation. The method is suitable for a micro-grid multi-inverter parallel control system consisting of a plurality of inverters connected to one another in parallel. Filtering capacitor voltage is differentiated to obtain filtering capacitor current, the filtering capacitor current can be acquired without the aid of a current transformer, and the designing amount of a hardware circuit is reduced; alternating quantity serves as the filtering capacitor voltage and filtering inductor current during power computing, and the outputting power of the inverters is reflected accurately; virtual complex impedance is guided in droop control, the output impedance of the inverters is ohmic, the inverters are suitable for a low-voltage micro-grid, and ring current among the inverters which are connected to one another in parallel is greatly reduced; and a dead-beat control method is used in current inner ring control, the filtering inductor current is controlled, the robustness of the system is high, the stability of the inverters which are connected to one another is high, and dynamic response is fast.

Description

technical field [0001] The invention relates to a method for controlling the parallel operation of multiple inverters in a micro-grid based on capacitance voltage differentiation, and belongs to the technical fields of distributed power generation and power electronics. Background technique [0002] Adopting the form of micro-grid to accept distributed power and solve the adverse effects of distributed power generation on large power grids has become a hot spot in current power system research. [0003] There are a large number of distributed power sources in the microgrid. For example, when photovoltaic power generation mainly provides energy sources for local loads, multiple inverters are required to operate in parallel to achieve large-capacity power supply and redundant power supply. At this time, the microgrid needs Reliable multi-inverter parallel operation control system to achieve operation in island mode. At the same time, in order to realize the hot swap of parall...

AI Technical Summary

Problems solved by technology

[0006] (1) Traditional droop control methods generally design the output impedance of the inverter to be inductive, but in low-voltage microgrids, the line resistance of the connecting line is much greater than the line inductive reactance. At this time, it is impossible to achieve accurate power distribution. , it is easy to have a large circulation

[0007] (2) In order to realize the controllability of the output impedance of the inverter, the researchers proposed virtual impedance, but some virtual impedance strategies are too complicated to realize; and the control strategy focuses on voltage control, which makes the dynamic response of the system slow. The current distortion rate also increases

[0008] (3) In some technologies, the AC quantity used in the power calculation link is the filter capacitor voltage and line current, which cannot accurately reflect the output power of the inverter

However, the design of the current control link is not fully considered in this paper

In addition, in this paper, the AC quantity used in the power calculation link is the filter capacitor voltage and line current, which cannot accurately express the output power of the inverter

[0011] Chinese patent document CN 102437589 B discloses a single-phase solar power multi-inverter parallel power sharing control method, including a single-phase solar power multi-inverter parallel system composed of several parallel inverters. However, the control method The virtual impedance technology was not used in the paper, especially the virtual complex impedance technology proposed later, which needs to be further improved and perfected in changing the output impedance of the inverter and making the parallel control method more widely adaptable.

[0012] Chinese patent document CN 102447268 B discloses a robust double-loop photovoltaic grid-connected control method based on power feedforward, which mainly includes three parts: outer loop voltage PI control, inner loop robust predictive current deadbeat control, and power feedforward control , where the voltage outer loop PI control is used to stabilize the DC side capacitor voltage; the inner loop robust predictive current dead-beat control uses advanced control to linearly predict the grid voltage and nonlinearly predict the grid-connected current in the next control cycle, Obtain the grid-connected current command value of the next cycle, and then realize PWM modulation and grid-connected control through deadbeat control. However, this invention is aimed at grid-connected inverters. Parallel control of inverters not yet mentioned

In addition, the AC quantity used in the power calculation link of this patent is the filter capacitor voltage and line current, not the filter capacitor voltage and filter inductor current, which also cannot accurately express the output power of the inverter.

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