A modular multilevel converter single-phase inverter test circuit and its test method

Abstract

A single-phase inverter test circuit for a modular multi-level convertor and a test method therefor. The method comprises: constructing a single-phase test circuit by using two modular multi-level bridge arms; connecting a passive resistance-inductance load; by means of the open-loop passive inversion algorithm and capacitive balancing algorithm, outputting a sine voltage and a sine current; and simulating the normal operation of a modular multi-level convertor, thereby completing the test of the electrical and capacitive balancing algorithms of the modular multi-level convertor. In the test circuit, a direct-current side is supported by a voltage source, so that in the control algorithm, there is no need to control a direct-current voltage, thereby simplifying the controller algorithm of the test. In the test circuit, a direct-current voltage source at the direct-current side is connected to a capacitor in parallel, so that bidirectional currents can flow in a direct-current bus and bridge arms, thereby solving the problem that a sub-module can be charged only, but cannot discharge when the direct-current voltage source is tested separately.

Description

technical field [0001] The invention relates to a test circuit of a modular multilevel converter, in particular to a single-phase inverter test circuit of a modular multilevel converter and a test method thereof. Background technique [0002] Modular multilevel converters use sub-modules in series, can use lower voltage turn-off devices to achieve high voltage output, and can use lower switching frequency to obtain better output voltage waveform, low switching frequency brings device switching The loss and the total loss of the system are greatly reduced, which improves the efficiency, reliability and economy of the converter system. Modular multilevel converters are used in flexible DC transmission, high-voltage frequency converters and other fields. [0003] In the development process of the modular multilevel converter, it is necessary to test the power devices, sub-modules, valve sections and other levels first, and then test the entire converter. In this way, the faul...

AI Technical Summary

Problems solved by technology

Since the current of the bridge arm will charge or discharge the capacitance of the sub-module, each bridge arm of the modular multilevel converter must have both positive and negative currents, so that the sub-module can be charged and also charged. Only when it can be discharged, the voltage can be maintained within a certain range, so as not to keep charging or discharging all the time and cause the circuit to eventually fail to work

The conventional DC voltage source can only output forward current, therefore, the single-phase inverter circuit of the modular multilevel converter cannot be directly connected in parallel with the DC voltage source

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