Balance controlling method and system for capacitance and level of three-phase five-level converter

Abstract

The invention discloses a balance controlling method and system for capacitance and level of a three-phase five-level converter. The method comprises the steps that a zero-sequence component is calculated according to a volume sequence result of three-phase output modulation voltage and an output current, reference level and capacitance neutral-point voltage offset of a corresponding phase; the zero-sequence component is respectively superimposed to the original three-phase output modulation voltage to obtain revised modulation voltage; voltage of a flying capacitor of each phase in a three-phase five-level topology, the switch state combination of a switching tube in the five-level topology of the corresponding phase and acting time of the corresponding switch state of the switching tube are determined according to a three-phase current, the revised modulation voltage and the voltage of the flying capacitor; the switch state combination and the acting time of the switch state are achieved by controlling the switching tube, so that the capacitance and the level are balanced. An auxiliary circuit does not need to be added, the method is low in cost and simple and easy to achieve, accuracy of balance control of the capacitance and the level of the converter is further ensured, meanwhile level control of the flying capacitors is further achieved, and the problem in the prior art is solved.

Description

technical field [0001] The present application relates to the technical field of electric power control, in particular to a method and system for controlling capacitor potential balance of a three-phase five-level converter. Background technique [0002] In new energy fields such as photovoltaic power generation and wind power generation, multilevel converters have attracted more and more attention because of their characteristics such as large output power, fast dynamic response, and good electromagnetic compatibility. However, because the capacitor potentials of four-level and above-level converters are not easy to balance, the potential control process is complicated, or additional circuit devices need to be added to realize the balance control of each capacitor potential, so the four-level and above-level converters are limited. application of the converter. [0003] In particular, the existing three-phase five-level converter system shown in Figure 1(a) (the five level...

AI Technical Summary

Problems solved by technology

For the three-phase five-level converter shown in Figure 1(a), it needs to control the potential of the midpoint N in balance and control the potential of the flying capacitor C1 of each phase in addition to the general multi-level circuit. Now The control method for the three-phase five-level converter system shown in Figure 1 is relatively complicated to implement, and the effect is not ideal

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