Research On Waveform Control Technique For Voltage Source Converter Based On Feedforward Control Of Inductor Current

Voltage source converter are widely used because of flexible and controllable,such as inverter power supply,uninterruptible power supply(UPS),active power filter(APF),static reactive power generator(SVG),unified power flow control(UPFC),new energy grid-connected inverter and power quality testing supply.The output waveform of the voltage source converter will determine the reliability of these applications.The traditional waveform control strategy has good steady-state accuracy for the amplitude,frequency and phase of the output waveform.But in the case of load disturbance and non-linear load,the steady-state performance and dynamic performance of the output waveform are difficult to meet the requirements.Therefore,it is of great significance to study the output waveform of voltage source converter.In this paper,the structure of the voltage converter is analyzed,and the model of the single-phase voltage converter is established.The main reasons for the distortion of the output voltage caused by the dead time and the load current disturbance is analyzed theoretically.In order to ensure that the output voltage quickly and accurately track the command voltage waveform,taking into account the existence of the output impedance makes the disturbance current will produce a voltage drop in the output voltage,affecting the output voltage waveform.And then in the traditional voltage outer loop capacitor current inner loop based on the introduction of the inductor current differential feedforward,through the inductance current in the harmonic component of the feedforward control to eliminate its impact on the output voltage.Through theoretical analysis and simulation studies show that the method can effectively improve the steady state output accuracy and dynamic response speed.Finally,the design scheme and the design of hardware parameters of the experimental system of power quality voltage disturbance source are given.And the differential feedforward control is applied to the experimental system of the voltage disturbance source.The steady-state accuracy of the output voltage after the differential feedforward control strategy is improved and compared with that of the non-added power quality.Then,the output waveform of the voltage controller under different parameters is compared and analyzed.It is found that the parameters of the voltage controller are reduced after the addition of the inductor current differential feedforward control,the pressure of the voltage control loop is reduced.It is proved that the proposed differential feedforward method can improve the steady state accuracy of the output voltage and reduce the pressure of the voltage control loop.