Hybrid modulation-based control method for mid-point voltage balance of multilevel inverter

Abstract

The invention discloses a hybrid modulation-based control method for the mid-point voltage balance of a multilevel inverter. The method comprises the following steps: detecting a capacitance transient voltage between the midpoint and the anode and a capacitance transient voltage between the midpoint and the cathode of a direct-current bus of the multilevel inverter by a sampling unit of a digital processing control module within each control period, and determining the bias of the two capacitance transient voltages; selecting an SVPWM (space vector pulse width modulation) or DPWM (digital pulse width modulation) control mode through a pulse width modulation strategy switching unit to work; outputting a control signal through an SVPWM / DPWM control processing unit; outputting a PWM signal through a drive circuit to control the working condition of each phase bridge arm switch tube of the multilevel inverter, and meanwhile, controlling the mid-point voltage balance of the multilevel inverter. The control method disclosed by the invention has the advantages that the switching frequency is reduced, the switching loss is reduced, output voltage and current harmonics are small, the output waveform quality is high, digital realization is convenient, and the like, and has an important engineering application value.

Description

technical field [0001] The invention belongs to the technical field of control in power electronic conversion technology, in particular to a hybrid modulation-based midpoint voltage balance control method of a multilevel inverter. Background technique [0002] The traditional two-level inverter has a simple control method and is easy to implement, but it also has the disadvantages of high output harmonic distortion rate, large voltage stress on the switching tube, and low efficiency. Multilevel inverters have the advantages of low withstand voltage level of switching devices, high equivalent switching frequency and small output waveform harmonics, so they are widely used in medium and high voltage high power conversion circuits. In order to generate multiple levels in the output phase voltage, two DC bus capacitors must be used in both T-type and NPC-type inverter topologies. Ideally, the voltage of each capacitor is half of the DC bus voltage, but in reality, both topologi...

AI Technical Summary

Problems solved by technology

[0004] 1) The deviation of the actual capacitance value due to the error of the manufacturing process;

[0005] 2) The characteristics of the switching tube are inconsistent;

Different sectors and different triangles have different formulas for calculating allocation factors; this method is complex and requires a lot of calculations

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