Research On Interface Algrithm Of Power Hardware-in-the-loop Simulation For Flexible DC Transmission

Power hardware in the loop(PHIL)simulation,combining advantages of digital simulation and physical experiments,can effectively analyze the steadystate characteristics of large-scale power grids and accurately simulate the dynamic characteristics of power electronic devices.It brings great flexibility to the theoretical research and engineering design of the flexible DC transmission.Delay time and noise disturbance introduced by the hardware in the digitalphysical interface will reduce accuracy or even lead to instability problems.It is necessary to compensate the stability and accuracy by choosing appropriate digital-physical interface algorithms.On the other hand,the MMC prototype is difficult to reach the voltage and power levels of the flexible DC transmission projects.The MMC prototype parameters should be rationally designed so as to reflect similar characteristics to real converters in the flexible DC transmission.This paper firstly puts forward a unified interface algorithm model in combination with the existing interface algorithms,in which different interface algorithms appear as different component parameters.Then the influences of various interface algorithms on system stability and accuracy can be compared horizontally under the same structure,which provides a theoretical basis for choosing appropriate interface algorithms.Next,this paper proposes an improved interface algorithm based on the damping impedance method and designs an appropriate compensation impedance according to the MMC DC impedance.This compensation impedance can not only suppress the delay time and the lowfrequency steady-state error caused by the temperature drift and zero drift of the feedback components,but also meet system stability and accuracy requirements.Further,aiming at the problem of different power levels of the digital and physical sides,this paper adopts the standardization parameter design theory to give the design method of the MMC prototype,reflecting real characteristics of the high power MMC station.Finally,a 300V/3k W MMC-based back-to-back flexible DC transmission PHIL system is built for reliable verification of the proposed theory.The relevant results can help to promote the application of this emerging PHIL technology in the flexible DC transmission.