Inverter circuit and voltage space vector pulse width modulation method thereof

Abstract

The invention discloses an inverter circuit and a voltage space vector pulse width modulation method thereof, which belong to the technical field of circuits. The inverter circuit comprises a direct current capacitor, a first three-phase bridge inverter circuit, a second three-phase bridge inverter circuit and a three-phase isolating transformer. The voltage space vector pulse width modulation method comprises the following steps of: acquiring basic voltage space vectors of the inverter circuit and corresponding switching tube switching state combinations thereof; computing a modulation degree according to an expected voltage space vector; determining the basic voltage space vector for synthesizing the expected voltage space vector according to the modulation degree, finding the corresponding switching tube switching state combinations of the determined basic voltage space vector, and selecting a switching tube switching state combination with the lowest switching frequency from the found switching tube switching state combinations; and regulating a switching tube according to the selected switching tube switching state combination to realize the synthesis of the expected voltage space vector. By the inverter circuit and the method, the problem of voltage unbalance of the direct current capacitor is solved, and the aim of lowest switching frequency in vector switching is fulfilled.

Description

technical field [0001] The invention belongs to the technical field of circuit design, in particular to an inverter circuit and a voltage space vector pulse width modulation method thereof. Background technique [0002] In medium-voltage high-power electric energy conversion applications, multi-level inverter technology has received more and more attention due to its unique advantages. Compared with the traditional two-level inverter circuit, the multi-level inverter has a large number of output voltage levels, less harmonic content, small du / dt caused by switching actions, reduced device withstand voltage requirements, and the same output. Advantages such as low device switching frequency. [0003] Common multi-level structures mainly include diode-clamped multi-level inverters, capacitor-clamped multi-level inverters, and H-bridge cascaded inverters with independent DC power supplies. Taking three-level as an example, diode-clamped three-level inverters and capacitor-cla...

AI Technical Summary

Problems solved by technology

Due to the structural characteristics of the diode-clamped three-level inverter itself, the O state leads to the charging and discharging of the DC side capacitors, resulting in unbalanced capacitor voltages. Therefore, the selection of the basic voltage space vector is subject to the capacitor voltage unbalanced problem. limits

Moreover, the state of the same bridge arm is prohibited from directly switching between the P state and the N state, and the O state must be added as a transition state in the middle, which again limits the selection range of the synthetic vector

Although the diode-clamped three-level inverter has increased the number of levels of the output voltage, the maximum amplitude of the fundamental wave of the output line voltage has not increased, and it is still the DC side voltage

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