Research On Control Strategy Of Two-way Enhanced Z-Source Converter

In order to adapt to the development of new energy generation and energy storage systems,distributed generation systems have placed increasing demands on converters.The three-phase converter is the core component of the microgrid and is the guarantee for the efficient operation of the microgrid.It is the medium for energy transfer between the new energy generation system and the large grid.The enhanced Z-source converter achieves a high boost gain of the Z-source topology by introducing a switch inductor structure,but the unidirectional energy flow of the enhanced Z-source converter is not conducive to the application in the energy storage system.Therefore,the introduction of a fully controlled switch tube to improve the enhanced Z-source converter is of great significance to the energy storage application technology of the microgrid.First of all,this paper introduces the research status and development of Z source converter at home and abroad.The principle analysis of the Z-source converter is carried out.To solve the shortcomings of the classical Z-source converter,a bidirectional enhanced Z-source converter is proposed.According to Kirchhoff's law and the volt-second balance principle,the mathematical relationship between the physical quantities of the bidirectional enhanced Z-source converter in the through state and the non-through state is analyzed.The state space method is used to DC the bidirectional enhanced Z source converter.The mathematical modeling is carried out on the side,and the transfer function between the through-duty ratio,the input power supply voltage,the DC link bus voltage,and the Z-source topological capacitor voltage is derived.The zero-pole distribution of each transfer function is analyzed,and the bidirectional enhanced Z source is verified.The feasibility of the converter topology.Secondly,compared with the advantages and disadvantages of the classic boost mode,the five-segment control mode is introduced to improve the direct-segment SVPWM modulation mode in the existing SVPWM control mode,which causes the switching frequency of the full-control switch to be too high.The on-time of the fully-controlled switch tube is fixed and the switching frequency is greatly reduced.In the distributed generation,the DC link voltage is greatly affected by the new energy generation operation mode,the output voltage is unstable,and the sliding mode control algorithm with strong robustness is added.The voltage error integral is selected as the sliding mode control variable,which reduces the sliding mode control.The steady state error of the system.Finally,in order to verify the advantages of the bidirectional enhanced Z-source converter,this paper uses the improved straight-through segmented SVPWM modulation method to build the SIMULINK simulation platform of the improved Z-source converter.It is verified that the improved Z-source converter has the advantages of strong boosting capability,small starting impulse current,good output waveform effect,bidirectional flow of energy and stable DC link voltage.