A Feeder Fault Power Flow Control For Micro-source Based On Energy Storage Type Quasi-Z Source Inverter

With the development of distributed new energy power generation technology,the application of microgrid composed of distributed power sources is becoming more and more widespread.The operation of the microgrid must meet reliability requirements.As an inevitable phenomenon in the operation of power system,faults have an important impact on the reliable operation of microgrid system.When dealing with fault power flow,the power support ability and control method of micro-source are critical to maintain the power supply operation ability and performance of island microgrid system.Therefore,the research on the control technology of micro-source inverter under micro-grid fault condition is of great significance.In this paper,based on the analysis of the operation characteristics of the micro-source inverter symmetrical fault,the emergency control strategy of the island micro-grid fault based on the energy storage type quasi-Z source inverter is studied.First,the structure and working principle of energy storage type quasi-Z source inverter are modeled and analyzed,and the control strategy of quasi-Z source inverter and super-capacitor energy storage system is introduced.Then the independent microgrid model of quasi-Z source inverters operating in parallel is established.The simulation of normal operation control of the island microgrid,and the distortion-free current limiting control under the symmetry fault of the island microgrid is carried out.The change of fault electric quantity in microgrid with distortion-free current limiting control is analyzed.Furthermore,a feeder fault power flow control strategy of micro-source inverter is proposed.The super-capacitor energy storage system is introduced into the quasi-Z source network,which makes use of the characteristics of the super-capacitor fast charging and discharging to enable the micro-source to provide fast fault power compensation for the grid side and improve the voltage support ability of the micro-source under symmetrical fault condition.Under the symmetrical fault condition of the island microgrid,the simulation results of distortion-free current limiting control and feeder fault power flow control arecompared.The results show that the feeder power flow control strategy proposed in this paper can quickly compensate the fault power flow under symmetrical fault and effectively suppress the drop of the operating voltage of the island microgrid.An independent microgrid experiment platform for parallel power supply with dual micro-sources based on super-capacitor energy storage type quasi-Z source inverter was built.The feeder fault power flow control strategy is verified by experiment,and compared with the experimental waveforms under distortion-free current limiting control.The experimental results verify the effectiveness of the control strategy to improve the micro-source's ability to support the grid-side voltage under fault conditions.