A System Of Energy Feedback And Active Filter Based On Three-phase Voltage Source Converter

Nowadays,in most of frequency transformer systems,grid-side rectifiers in the structure of frequency converters often adopt an uncontrollable diode.They will be in a state of regenerative electric power when electric motors slow down or brake,which may give rise to the rise of DC capacitor voltage and thus threaten the normal operation of the systems.The traditional countermeasure is to add an energy consumption braking unit.Therefore,energy feedback devices can be used to give back the regenerative energy to power networks;however,they will lay idle during the normal operation of frequency converters.Since energy feedback devices have consistency with traditional active power filters in topological structure,in order to take full advantage of them,their operating state can be changed into the operating mode of active filters,so the harmonics generated from the rectifying of frequency converters can be compensated and the grid-side current harmonics can also be purified so as to realize their double purposes and improve their cost performance.Based on the structure of three-phase voltage source converters,this paper mainly designs energy feedback systems and active filter control systems.Firstly,it gives a general introduction of instantaneous reactive power theory and harmonic detection principle,analyzes the mathematical model of three-phase voltage source converters,and designs some key structures,such as phase-locked loops,low pass filters,etc.Then,it has a further research on the control method of the system,discusses the commutation process of the device and relevant current-transformation method,designs the voltage and current controller,and carries out a simulation to verify the rationality of the system.Finally,taking RX63t DSP produced by Renesas as a processor,it designs a software algorithm,introduces the design platform of the system,and elaborates the whole structure of the algorithm,phase-locked loops,energy feedback,harmonic compensation and the working process of voltage rise.In the end,this paper conducts an experimental verification on the proposed prototype,records the voltage and current waveform in a state of energy feedback and active filter,and analyzes the experimental results.The experimental results demonstrate that the algorithm and the device designed in this paper can achieve the desired functionality,give back the energy generated from braking timely and compensate the grid-side current harmonics.