Cascade type time-interval variable-order multi-level static converter

Abstract

The invention provides a cascade type time-interval variable-order multi-level static converter, which can be modularized; a previous-stage four-way isolation DC-DC (Direct-Current-Direct-Current) converter (1) is connected to a subsequent-stage four-unit cascade inverter (2); a novel time-interval variable-order multi-level control circuit (3) is connected between the previous stage and the subsequent stage; the converter is characterized in that the previous stage is adopted with four ways of mutually independent, staggered and parallel double-tube forward direct-current converters; the subsequent stage is a cascade structure composed of four single-phase H bridges; a carrier phase-shifting frequency-doubling SPWM (Sinusoidal Pulse Width Modulation) technology is adopted; the time-interval variable-order multi-level control circuit is connected between the previous stage and the subsequent stage; the previous stage of the static converter is beneficial to reducing input current ripple and reducing the volume of a filter; the subsequent stage is low in voltage stress of a power switch device, high in circuit modularization degree and low in loss; and, by means of the time-interval variable-order multi-level control circuit, on the premise of not increasing the number of independent sources of the previous stage, the more level number of output can be realized, and the THD (Total Harmonic Distortion) of the harmonic wave is low.

Description

technical field [0001] The invention relates to a cascade type time-divided step-variable high multi-level static converter, which belongs to the power electronic conversion technology. Background technique [0002] In recent years, cascaded multilevel inverters have received extensive attention in various occasions where DC power is converted into AC power. A single-phase / three-phase inverter formed by connecting several basic inverter units in series is called a cascaded inverter. Since the cascaded inverter has a single device with less voltage stress, it is easier to achieve high voltage and large capacity; at the same switching frequency, the output voltage and current waveforms are closer to sine waves, and the harmonic content is low; no clamping diodes and clamping Capacitor, simple structure, easy to modularize and other advantages, and although the overall equivalent switching frequency becomes higher, the switching frequency of each H-bridge unit is reduced, whic...

AI Technical Summary

Problems solved by technology

At the same time, cascaded inverters need to isolate a large number of DC voltage sources, consider balancing the utilization of each unit, and in the case of a large number of cascaded units, various PWM control strategies will be very complicated, and the control is relatively difficult. The application of cascaded inverters is restricted

[0004] Therefore, it is necessary to seek a new type of static device that can not only reduce the volume and weight of passive devices, but also solve the problems of excessive number of independent DC voltage sources and complex logic of PWM control strategy caused by increasing the number of cascade units, and can be designed in a modular manner. Converters are imminent, which will also be of great significance to effectively improve the conversion efficiency, reliability and cost reduction of static converters

Images