Three-level converter and control method thereof

Abstract

Disclosed are a three-level converter and a control method thereof. The three-level converter comprises four legs connected in parallel and a capacitance circuit in parallel connection with the legs. Four phase wires a, b, c and n are led out from the four legs, respectively. A neutral wire is led out from a midpoint of the capacitance circuit. The capacitance circuit comprises a first capacitor and a second capacitor serially connected and then parallelly connected to two ends of a direct current busbar. Each leg comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, each of which is reversely parallelly connected with a diode; the first switch tube, the second switch tube and the third switch tube are connected in series and are then connected in parallel at two ends of the direct current busbar; one phase wire is led out from between the second and third switch tubes; one end of the fourth switch tube is connected between the first and second switch tubes; the other end of the fourth switch is connected between the first and second capacitors. The three-level converter has the advantages that complex coordinate transformation in PARK transformation or CLARK transformation is avoided, vectors are processed by making direct use of space geometry, the modulating process is simple and easy to understand and has clear physical meanings.

Description

technical field [0001] The invention relates to an inverter, in particular to a three-level inverter and a control method thereof. Background technique [0002] There are three types of commonly used inverter structures: full bridge cascaded, flying capacitor and diode clamped. For inverters of the same level, full bridge cascaded inverters do not require clamping diodes and flying capacitors, but require more DC sources; flying capacitor inverters require a corresponding number of flying capacitors Capacitance; diode-clamped inverters require certain clamping diodes. [0003] Among the pulse width modulation methods of inverters, there are two commonly used sinusoidal pulse width modulation methods (SPWM) and space vector modulation methods (SVPWM). The advantage of the SPWM method lies in its simple principle and good control and regulation performance, and it can play multiple functions such as eliminating harmonics, regulating and stabilizing the output voltage, but th...

AI Technical Summary

Problems solved by technology

At present, the three-phase voltage is mainly transformed from the abc coordinate system to the αβo coordinate system by using the PARK transformation or the CLARK transformation, but the transformation process requires a large number of calculation processes, and there are also three-dimensional space vector modulation methods based on the abc coordinate system (without coordinate transformation). , but the whole process is not very easy to understand

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