Parallel inverter system capable of realizing structure reorganization and control method of system

Abstract

The invention discloses a parallel inverter system capable of realizing structure reorganization and a control method of the system. Structure reorganization of the parallel inverter system can be realized at any time through control on IGBT (insulated gate bipolar transistor) switch states of inverters, a parallel inverter structure is endowed with a function for parallel connection / removal of the inverters at any time, that is, under the condition that the parallel inverter system works, the N inverters can be connected in parallel or disconnected randomly so as to be matched with loads, and the overall efficiency of the system is improved; the structure has the function for parallel connection / removal of the inverters at any time, that is, under the condition that the parallel inverter system works, the N inverters can be connected in parallel or disconnected randomly; active power control and reactive power control can be provided simultaneously, meanwhile, ZSCC (zero-sequence circulating current) suppression can also be realized through adoption of prediction control on the redundant zero switch state; besides, the system does not affect current and voltage vectors on the alternating current side.

Description

technical field [0001] The invention relates to a parallel inverter system capable of structural reorganization and a control method thereof. Background technique [0002] With the increasing shortage of non-renewable energy sources, renewable energy sources such as solar energy and wind energy are developing rapidly and playing an increasingly important role. The grid-connected inverter is the interface between the renewable energy generation system and the grid. It plays an indispensable role, and its performance will directly affect the power quality of the grid. Therefore, the research work on the grid-connected inverter has important application value. [0003] Parallel three-phase inverters have attracted extensive attention due to their advantages of high efficiency, low cost, and scalability. Compared with the rated power limit of a single inverter, parallel inverters can meet higher rated power, higher efficiency and lower harmonics. In addition, it is more conveni...

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Problems solved by technology

However, due to the uncertainty of the load and load power, the inverters in the parallel inverter system often cause low efficiency because they do not work near the rated power, and when the inverters are connected in parallel, there will be a zero-sequence cycle in the system Current (zero-sequence circulating currents, ZSCCs) problem

As we all know, the generation of zero-sequence circulating current is caused by the fact that the hardware parameters of multiple inverters / bidirectional converters are not completely consistent, and the control signals cannot be synchronized. ZSCCs will cause current distortion and harmonic loss of parallel modules, and will reduce the overall performance of the parallel system. performance

[0004] There are currently the following methods for suppressing ZSCCs in inverter parallel systems: it can be eliminated by using a separate DC power supply or using an isolation transformer on the AC side, but this will greatly increase the size and cost of the system; the application is based on interleaved intermittent space The parallel PWM converter control strategy of vector modulation suppresses ZSCCs, but it will cause high output current ripple; uses nonlinear control methods to suppress ZSCCs, but the algorithm is too complicated; uses SVM technology to control ZSCCs or introduces control variables, Using methods such as proportional integral (PI) control and deadbeat control to adjust the distribution of zero vectors in each PWM cycle requires a large number of parameters to be adjusted, and can only be used at higher switching frequencies, and the dynamic response is slow.

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