| The long-term coexistence of traditional fossil energy and renewable energy is the current situation and trend of energy development in the world.Microgrid system can build suitable multienergy complementary micro power architecture according to different local resource conditions to enhance the security,redundancy and economy of microgrid system,and further get rid of the limitation of fossil energy to promote the transformation of energy structure and sustainable development.The parallel micro power system of PV,wind power,hydro power,energy storage and diesel generators can realize multi-energy cooperative power generation,of which droop control technology is an important part of the system.The droop control based multiple micro power system can reduce the dependence on the communication system and realize the peer-to-peer control and plug-and-play between micro power sources.However,there are differences in energy conversion,control methods and electrical characteristics between the power electronic generation units connected with renewable energy and the synchronous generators in traditional energy generation,and it is difficult to solve the problems of new energy backflow counter-current and inertia mismatch between micro power sources in the scenario of high percentage of new energy access and parallel connection of multiple types of micro power sources by traditional droop control.Therefore,it is a hot issue to further improve the droop control strategy for multimicro power parallel system.In this paper,the stability of the parallel system of multi-micro power supply is analyzed by establishing the equivalent output impedance model of voltage source inverter and synchronous type power supply with droop control.A distributed secondary control method is proposed to compensate the static deviation of the AC bus voltage and frequency for the inherent deviation of the steady-state voltage and frequency of the conventional droop control.Further,in the coordinated control problem of multiple types of micro-power parallel systems,adaptive improvement strategies are proposed in the voltage source inverter droop control inertia link and current source inverter power control link to realize the power adaptive distribution and inertia matching of multiple types of micro-power parallel systems,which improves the flexibility and stability of the parallel systems.Finally,the theoretical analysis,modeling simulation and experiments are combined to verify the effectiveness of the parameter design and control strategy of the improved droop control technology proposed in this paper,which provides a reference design and theoretical basis for the practical application of multiple types of micro-power parallel systems. |
