Improved repetitive control method for three-phase PWM inverter

Abstract

The invention discloses an improved repetitive control method suitable for a three-phase PWM inverter. A fractional-order repetitive controller is obtained through Lagrangian interpolation, and therefore, a voltage of a specified fluctuating frequency can be outputted, and at the same time, the dynamic response speed and steady state output accuracy of the device can be improved; state feedback control is additionally adopted to compensate the resonance peak of a compensation system, and therefore, the performance of the system can be improved, and the design of the repetitive controller can be facilitated; the repetitive controller is used to accurately track input signals, can achieve the zero-error tracking of a command voltage, and can completely suppress a non-command voltage, so thatadditional interference can be prevented from being introduced into system measurement; state feedback control and repetitive control are combined, so that stability and response speed can be well balanced; and with the repetitive control adopted, the dead zone effect of a switching device can be compensated, and the adverse effects of a dead zone on an entire control system can be reduced. Withthe method of the invention adopted, the output distortion rate of the PWM inverter can be significantly reduced, and the output accuracy and response speed of the PWM inverter under frequency varyingand voltage varying commands can be improved.

Description

technical field [0001] The invention relates to the control field of three-phase PWM inverters, in particular to a control method of a three-phase PWM inverter with output fluctuating frequency. Background technique [0002] With the development of power electronics technology, the three-phase PWM inverter technology has become increasingly mature, and the main circuit of the PWM inverter has developed from the early semi-controlled device bridge to the current full-controlled device bridge; its topology has changed from Single-phase and three-phase circuits are developed to multi-level topological circuits. Conventional inverters are usually relatively simple to control, and open-loop operation can also output better waveforms. However, when some high-performance output requirements are required, the output performance of the open-loop operation of the inverter cannot meet the accuracy requirements. In order to improve the output steady-state performance and dynamic respon...

AI Technical Summary

Problems solved by technology

The hysteresis control is simple and robust, but the switching frequency is not fixed and the current ripple is large, which affects the control accuracy of the DC side voltage; the traditional PI control is simple in design and easy to implement, but it cannot realize the unsteady error tracking of the AC quantity Control; the proportional resonance (PR) controller has infinite gain at the resonant frequency, and can track the AC reference current with zero steady-state error, but because it only has a large gain at one frequency point, it cannot output tracking of multiple frequency points Waveform; deadbeat control is a control algorithm based on the precise circuit model of the controlled object, which has the characteristics of fast response speed and small control error, but it needs to establish an accurate mathematical model, which is often difficult to obtain. In addition, in order to achieve the effect of eliminating errors within a sampling period, the controller often takes very drastic control actions. When there is a difference between the ideal model and the actual counterpart, this will not only fail to achieve the effect, but will cause the output voltage to oscillate. It is not conducive to the safe and stable operation of the inverter; repetitive control is a control method based on the internal model principle, which is actually a cycle-by-cycle integral control. By supplementing the waveform error cycle by cycle, no static error can be achieved in the steady state effect, and when the system has disturbances, including nonlinear loads, dead zone effects, etc., the use of repetitive control has a good anti-disturbance ability, so the use of repetitive control for PWM inverters has a better output effect

[0004] However, when it is necessary to output a voltage with fluctuating frequency in some special occasions, it is difficult for the traditional repetitive control method to have a good tracking effect at the point of frequency fluctuation, and the output effect will be significantly reduced, and the dynamic performance of the traditional repetitive control is not good. When When the output needs to change suddenly, it is difficult to meet the high performance requirements

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