Parallel Time-sharing Power Supply Forward DC Chopper Type Single-stage Multi-input High-frequency Link Distributed Power Generation System

With the reserves of traditional energy such as coal and oil are becoming increasingly tight and the environmental pollution is gradually intensifying,Countries around the world pay more and more attention to renewable and non-polluting green new energy such as solar energy and wind energy.A single new energy system that supplies power to the load alone is not stable enough and greatly affected by day and night and climatic conditions.In order to improve the stability of the power generation system and ensure that multiple new energy can be used preferentially and fully,the distributed generation system(DGS)that multiple new energy supply power at the same time or time-sharing is needed.Based upon the discussion of single-input and multi-input DC converter type two-stage distributed generation systems,this paper proposes a parallel time-sharing forward DC chopper type single-stage multi-input high-frequency distributed generation system.The key technologies such as the circuit topology,energy management control strategy,steady-state principle characteristics,and major circuit parameters design criteria of the power generation system are theoretically analyzed and simulated,with the following important conclusions obtained:The circuit topology of the parallel time-sharing forward DC chopper type single-stage multi-input high-frequency distributed generation system are proposed and studied in depth,the circuit topology is composed of a single-stage multi-input high-frequency inverter and a single-stage isolated battery charging/discharging converter,with their outputs connected in parallel on the AC side.The former is cascaded by the parallel-timesharing selection switches,single-input single-output isolated bidirectional forward DC chopper and output LC filter,the latter is equivalent to a single-stage bidirectional Buck mode inverter/Boost mode rectifier.This paper proposes and analyzes the multi-input source maximum power output energy management control strategy of the proposed power generation system with the single-stage isolation bidirectional charge and discharge converter output voltage independent control loop of the power generation system,as well as 3 power supply modes and their smooth transition mechanism.According to the balance between the total power of multi-input source and the load power,the system has three power supply modes,the energy management control strategy can realize the stability of the output voltage of the system and the smooth and seamless switching of the three power supply modes through this energy management control strategy.The HF switching process,external characteristics and the key issues on the voltage spikes of power switch and battery input second harmonic current,are discussed in detail.The design criteria of key circuit parameters such as the input,output filter,high-frequency transformer turns ratio,power switch current,voltage stress and so on are derived.A simulation system of 3kVA 240-360VDC/220V50 Hz AC distributed generation system is designed,Simulation results have verified the feasibility and correctness of the proposed circuit topology and energy management control strategy,the power generation system has a simple circuit structure,single-stage power conversion in addition to battery charging,high conversion efficiency,multi-input source parallel time-sharing power supply,multi-input source-battery-AC load electrical isolation,it provides an effective new method for the distributed power generation system with multiple new energy joint power supply.