The Design Of MMC-HVDC Physical Dynamic Simulation System

In recent years,with the development of power grid construction in China,MMC-HVDC plays a pivotal role in areas such as large-scale renewable energy grid and isolated power supply because of the advantages of low harmonic content of output waveform,fast response speed and the high level of modularity.MMC-HVDC is needed for all kinds of test under different working conditions before actual operation,in order to ensure the feasibility of each component parameters and the effectiveness of the control strategy.Due to the complexity of the control system,inverter contains a lot of power electronic devices,using digital simulation can't reflect the dynamic characteristics.Physical dynamic simulation can not only test the performance of the inverter control system,but also reflect detailly the dynamic characteristics of the inverter power devices,capacitor and bridge arm reactor in various operation conditions.This paper researchs the equivalent principle,system construction method,hardware circuit design and the related control strategy of physical dynamic simulation system.The basic working principle of MMC converter is analyzed,inverter topology structure,the dynamic mathematical model and decoupling control method are studied.In addition,the operation control and inverter modulation modulation are analyzed,including preliminary charging control strategy,nearest level modulation and sub-module capacitance equalizing control strategy,which provides a basis for the construction of physical dynamic simulation system.The design of MMC-HVDC physical dynamic simulation system is Carried out,and the overall structure of MMC-HVDC physical dynamic simulation system is constructed including the system's overall design and the design of the control system architecture;That the equivalent method of simulating converter sub-module,the component selection method and sub-module and controller hardware circuit are designed.Designing the software part of the control system,the hree-phase phase-locked loop control algorithm is put forward which improves the performance of control system;The data transfer method,between control panel,based on the FPGA communication is also forward which improves the efficiency of data transmission.Carring out the ststem test work on the established system of MMC-HVDC physical dynamic simulation.The response speed and stability of the inner loop controller are improved by the parameter setting and optimization of the inner ring current PI;That the constant reactive power control and constant DC voltage control experiment verify the controller control strategy at all levels,the completeness and accuracy of the communication protocol between the layers;In addition to that,the all kinds of working condition and the fault event are carried out,which verify the performance of the physical dynamic simulation system.