Common Mode Voltage And Suppression Of Control Signal's Narrow Pulse For Matrix Converter

Matrix converter (MC) is a kind of direct AC-AC conversion device. It has important characteristics needed for the ideal variable_frequency power supply such as sinusoidal input and output waveforms, unit input power factor, bi-directional power flow, the ability of four quadrant operation of the loading motor, and no need of medium DC link, which is in accordance with the modularization trend of power converters. However, the problem of switching control signal narrow pulse cannot be avoided due to restrictions on modulation algorithm of two line voltage and input and output waveforms. Narrow pulse may lead to commutation failure, voltage and current spike signals and input and output performances of the system have been influenced. Moreover, the high-frequency common mode voltage (CMV) caused by the matrix converter has a great harm to the load and the electrical equipments.In this paper, considerting the harm to MC control system caused by control signal's narrow pulse and CMV, the two line voltage systhesis is improved by adjusting the duty cycle and choosing the input phase of zero output voltages.Firstly, the topology and mathematical model of the MC are introduced, and the two line voltage systhesis is described in this paper. The simulation model is established using Matlab/Simulink. Simulation results show the two line voltage systhesis has the feasiblilty and the ascendant anti-jamming characteristic.Secondly, the modulation strategy is improved. Considering the commutation failure caused by narrow pulse, a new type of narrow pulse suppressing method is proposed in this paper. Based on retaining constant output voltage, the duty cycle less than the minimum commutation time is adjusted in the sampling period when narrow pulse exists, and the input and output waveforms are improved. Due to the great harm to the load and the electrical equipments caused by CMV, the instantaneous value of CMV in the sampling period for matrix converter under the control strategy of the basic two line voltage is analyzed in the paper. Aiming at the delay effect of four step commutation, the determinants of the CMV error and the change of average common mode voltage in the sampling period are analyzed. By choosing the input phase of zero output voltages combination accurately, the peak value of CMV can be reduced to 3/3 times the peak value of input phase voltage. Simulation results demonstrate the correctness and the validity of the modified systhesis.Finally, based on theoretical analysis and simulation, the MC test platform is designed by adopting DSP TMS320F28335 as main controller and FPGA EP1C6T144C8 as coprocessor. Based on the test platform, programs are designed, and the anti-interference characteristic of the two line voltage systhesis, the harmfulness of narrow pulse, and the availability of CMV suppression are proved. The experimental results show that the input and output spike signals is avoided, the input and output performances of MC are improved, the negative effect of CMV is reduced, and the reliability of systems operation is enhanced.