DC (direct current) loop-current suspension device for inverter parallel system

Abstract

The invention discloses a DC (direct current) loop-current suspension device for an inverter parallel system. According to the invention, a DC loop-current control device is added to the control circuit of the existing inverter parallel system, the DC loop-current control device is composed of a voltage DC component suspension circuit. Each inverter module in the parallel system has an independent DC component suspension circuit, a voltage DC component feedback quantity can be obtained through carrying out differential amplification sampling, low-pass filtering and proportional integral regulation on high-frequency PWM (pulse width modulation) wave between an inverter half-bridge midpoint and a dividing capacitor midpoint, a DC component deviation can be obtained through the comparison between the voltage DC component feedback quantity and a voltage DC component reference value, and the DC component deviation is added to an inversion reference voltage, and then the voltage DC component of each inverter can be controlled to be zero through correcting the inversion reference voltage, so that the DC loop-current of the parallel system can be controlled to be zero. The device disclosed by the invention has simple structure and is convenient to implement; and by the adoption of the invention, the characteristics of the original parallel system are maintained, and the DC loop-current of the parallel system can be eliminated.

Description

technical field [0001] The invention belongs to the field of inverter power supply, and relates to a device for suppressing the DC circulating current of an inverter parallel system. Background technique [0002] With the development of information technology, users' requirements for AC power supply capacity and power supply reliability are also increasing. The redundant parallel connection technology of inverter power supply is an effective technical means to solve the above problems. [0003] The parallel current sharing control methods of inverter power supply mainly include master-slave control, droop control, instantaneous average current control and active power and reactive power sharing current control. The active power and reactive power are evenly distributed in each parallel module, it is necessary to control the amplitude, phase and frequency of the inverter output AC voltage of the parallel module to be equal in time, otherwise active circulating current and rea...

AI Technical Summary

Problems solved by technology

This method has the following disadvantages: First, because it is an indirect control, the inverter reference can only be adjusted according to the proportional relationship between the DC circulating current and the DC voltage difference when the DC circulating current changes significantly, and there is a lag in the adjustment time; secondly, this method can only be based on The proportional relationship between the size of the DC circulating current and the DC voltage difference is used to obtain the DC voltage difference between the parallel modules. It is not possible to determine the specific DC voltage component of each module. In this way, when multiple modules are connected in parallel, this scheme is used to adjust the DC circulation of the parallel system. It is easy to cause the misadjustment of individual modules and cause the failure of the parallel system

Since this method samples on the output filter capacitor, for a parallel system, the output filter capacitor of each inverter is connected in parallel on the AC output bus, so a single inverter cannot distinguish the sampled voltage DC Whether the component is its own or other inverters, it is prone to misadjustment

Similarly, when multiple modules are connected in parallel, it is difficult to control the DC circulation of the parallel system by using this scheme

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