Research On Auxiliary Converter Parallel Technology Based On Virtual Synchronous Generator

With the rapid development of rail transit industry,more and more intercity rails appear in the field of rail transit.Power EMU has the characteristics of comfort,convenience and rapidity,which makes people regard EMU as the first choice for intercity travel.As the auxiliary power supply unit on EMU,the auxiliary converter supplies power for medium voltage load on EMU.In order to improve the reliability and redundancy of auxiliary power supply system,this paper focuses on the research of auxiliary parallel technology based on virtual synchronous generator.As the basis of parallel operation of auxiliary converters,this paper firstly studies the technology of single virtual synchronous generator.Using the synchronous generator model to build the mathematical model of the governor and exciter,the core control algorithm of the virtual synchronous generator is further derived to control a single auxiliary converter.The control technology of single auxiliary converter adopts the technology of virtual synchronous generator,which makes the auxiliary converter have multiple excellent performances,such as large moment of inertia,droop characteristics,frequency and voltage self-regulation,similar to synchronous generator.In the aspect of parallel control technology of auxiliary converter,this paper proposes a control strategy of virtual synchronous generator without PLL.In this paper,the key technologies of auxiliary parallel are analyzed.Based on the single control strategy,the pre-synchronization algorithm is introduced to realize seamless and smooth switching between single and parallel operation,and the whole control strategy is optimized.In order to select the control parameters reasonably,this paper analyzes the small signal model of the virtual synchronous generator,gives the design method of the key parameters,and applies the control parameters to the parallel control of the auxiliary converter,so that the power of the whole parallel system is naturally evenly distributed,and the dynamic and stable performance of the system frequency is greatly improved.In this paper,the S-function module of MATLAB/Simulink is used to compile and build the simulation platform of the auxiliary parallel system,and the accurate model is built and simulated according to the different operating conditions of the auxiliary parallel system;the no-load and on load parallel experiments are carried out by using the parallel system experiment platform of the auxiliary converter of EMU.The simulation and experimental results show that the parallel process of the auxiliary converter is smooth and the current sharing effect is excellent,which proves the effectiveness and feasibility of the proposed auxiliary parallel technology based on virtual synchronous generator.53 Figures,3 tables,60 references...