Quasi-resonance converter adopting LLCL-type filter and limiting reverse recovery current

Abstract

The invention provides a quasi-resonance converter adopting an LLCL-type filter and limiting a reverse recovery current. The quasi-resonance converter comprises an equivalent DC (Direct Current) power supply, a controllable capacitance branch circuit and a three-phase output converter, wherein an output end of the equivalent DC power supply is connected with an input end of a boosting converter, two ends of the three-phase output converter are connected with the output end of the boosting converter, one end of the controllable capacitance branch circuit is connected with a positive bus-bar end of the three-phase output converter, the other end of the controllable capacitance branch circuit is connected with a position output end of the equivalent DC power supply, and the three-phase output converter is provided with a filter in a connection manner and is communicated with a power grid or a load through the filter. According to the quasi-resonance converter provided by the invention, the problems of large DC voltage output range, softened switch, filtering output of the converter and the like of a renewable energy source power generation system during the application are comprehensively considered, the connection mode of the controllable capacitance branch circuit is changed, the withstand voltage of the controllable capacitance branch circuit can be greatly reduced, and thus the cost can be further lowered.

Description

technical field [0001] The invention relates to a converter, in particular to a quasi-resonance converter which adopts an LLCL type filter and limits reverse recovery current. Background technique [0002] With the increasing shortage of traditional energy sources, new clean energy (such as solar energy, fuel cell) power generation technologies have attracted more and more attention. Commonly used grid-connected converters based on PWM modulation technology will generate a large number of high-order harmonics, which will easily pollute the public power grid. Considering the requirements of "green" power grid, the converter device and the public grid are generally connected through a low-pass filter to prevent excessive switching frequency and current harmonics at double frequency from being injected into the public grid. For single-phase converters, the output filter adopts LLCL filter to achieve the purpose of minimum inductance. LLCL filter is a resonant branch composed o...

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Problems solved by technology

However, when the triangular carrier modulation method is used, the LLCL filter needs to provide dual current bypass channels with the carrier frequency and twice the frequency for the harmonic current generated by the converter, and the structure is complex

If the sawtooth carrier modulation method is adopted, the output harmonic current frequency of the converter is just concentrated at the carrier frequency. At this time, the LLCL filter only needs to provide a single current bypass channel. At this time, the structure and parameter design method of the LLCL filter are also Relatively simple; however, the filtering capability of the system from 150 kHz to 30 MHz is degraded with only conventional LLCL filters

When the traditional three-phase inverter adopts the sawtooth carrier modulation method, the output current waveform is seriously distorted

In the traditional three-phase converter power supply system, since the reverse recovery characteristics of high withstand voltage devices are much worse than those of low withstand voltage devices, and most switching devices are in hard on and off states, three-phase DC / AC converter It is difficult for converters to increase power density under the premise of low cost

At the same time, the use of quasi-resonant converters that limit the reverse recovery current, the capacitor voltage of the controllable voltage branch is high, and the cost should not be further reduced

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