Direct torque control method for harmonic voltage injected multi-phase induction motor

Abstract

The invention discloses a direct torque control method for a harmonic voltage injected multi-phase induction motor. In a multi-phase motor system, non-sinusoidal voltage and current are supplied, so that the air gap magnetic density waveform is quasi-square wave, the magnetic potential and the magnetic density peak of fundamental wave can be reduced, and the utilization rate of an iron core material and the power density of a motor are improved. When the multi-phase motor is driven by a voltage type frequency converter, the circuit impedance of fundamental wave and harmonic spaces is changed together with the change of a load, and the control requirement that the air gap magnetic density is square wave cannot be met by adopting fundamental wave and harmonic voltage constant proportion control. Therefore, in a direct torque control system of the multi-phase motor driven by the voltage type frequency converter, effective control of fundamental wave and harmonic voltage amplitudes and phases must be realized. A variable frequency speed control system of a five-phase centralized integral pitch winding induction motor is taken as an example in the method (which is also suitable for a random multi-phase induction motor system), a control scheme of combining spatial voltage vector modulation and direct torque control is adopted, and fundamental wave and third harmonic reference voltages are calculated by controlling torques respectively formed by the fundamental wave and the third harmonic and controlling stator flux. The control method realizes closed loop control of the fundamental wave and harmonic voltages, ensures a constant phase relationship between the fundamental wave and the third harmonic flux, and achieves the control requirement that the air gap magnetic density waveform is the quasi-square wave. Due to effective control on harmonics, the output torque of the motor is increased, and the robustness and the dynamic steady state performance are also improved.

Description

technical field [0001] The invention belongs to the technical field of AC motor system speed regulation, and specifically relates to the direct torque control of multi-phase motors. By effectively controlling the variables of the fundamental wave and harmonic space, the magnetic saturation of the motor is reduced, and the utilization rate of iron core materials and the efficiency of the motor are improved. power density. Background technique [0002] This patent takes five-phase induction motor frequency conversion speed regulation system as an example (also applicable to any multi-phase induction motor system), the system structure is as follows figure 1 shown. The whole system is mainly composed of transformer, uncontrolled rectifier, chopper circuit, inverter, induction motor load and so on. In view of the obvious advantage that each H bridge in the H bridge structure is one phase, which is convenient for harmonic injection, the inverter driving the motor adopts the H b...

AI Technical Summary

Problems solved by technology

[0020] The method for direct torque control of multi-phase induction motors with harmonic voltage injection provided by the present invention is characterized in that space voltage vector modulation and direct torque control are combined to solve torque ripple and low speed caused by transmission hysteresis switch meter control. Poor performance and other problems; through the control of the torque and stator flux linkage formed by the fundamental wave and the third harmonic respectively, the closed-loop control of the fundamental wave and the third harmonic voltage is realized, and the fundamental and third harmonic flux are guaranteed at the same time. The phase relationship of the chain is constant, so that the air-gap flux density waveform is a quasi-square wave, which can effectively reduce the fundamental magnetic potential and peak flux density, thereby improving the utilization rate of core materials and the power density of the motor

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