Research On Interface Algorithms Of Power-hardwarein-the-loop Simulation System

In recent years,with the increase of the permeability of distributed power generation units,the operation characteristics of the grid are constantly changing,which is more likely to cause problems,such as grid obstruction and voltage stability reduction.As a modern cutting-edge technology,simulation technology can simulate the actual system and process in a variety of complex environments,and is widely used in scientific research and production testing of power devices.Among them,power hardware in the loop(PHIL)technology,as a new simulation technology,effectively combines the advantages of traditional digital simulation and physical simulation.It "breaks down" the actual system and loads the part of structure which is easy to carry out accurate mathematical modeling into the digital simulator.Others are connected to the digital simulator through the power interface to realize the signal interaction with the digital side model and reduce the simulation cost.Because PHIL simulation technology combines the advantages of real-time digital simulation and physical simulation,it can effectively simulate various working conditions of the grid and is a new method of power system research.Interface algorithm realizes the signal interaction and energy transmission between the digital side and the physical side,which is the key technology of PHIL simulation.Therefore,this paper studies the key problems of PHIL system and its interface algorithm.The main research contents are as follows:First of all,several typical interface algorithms are summarized.The ideal transformer model(ITM)method and damping impedance method(DIM)are regarded as the main research object.Through the study of the mathematical modeling of PHIL system,the stability of ITM-based and DIM-based PHIL simulation system is contrasted and analyzed.After that,the simulation accuracy of frequency domain evaluation indexs are proposed.With the aid of the intuitive multidimensional graphic method and considering the impedance measurement bias of DIM,simulation accuracy of DIM-based and ITM-based PHIL system are analyzed.In addition,the question how the accuracy of the simulation system is influenced by the equivalent impedance,delay type,the harmonic component(harmonic frequency defined within 2 kHz),and other factors on,is discussed.Then,several opinions for configuration PHIL system are put forward:(1)In most of the lowvoltage power system conditions,can give priority to the ITM,other condition choose DIM as far as possible;(2)For PHIL system hardware selection,in order to improve the simulation accuracy of the system,priority is given to the fpga-based(real-time simulation delay is small)simulator,and then consider the use of linear power amplifier instead of switching power amplifier.Finally,the significance of the existence of damped impedance branches in DIM-based PHIL system is discussed,and the relationship between the impedance matching degree and the simulation accuracy of DIM-based PHIL system is analyzed.The impedance measurement technology of DIM interface system is studied,including sweep frequency method,white noise disturbance injection method and multiple sinusoidal disturbance injection method,etc.The advantages and disadvantages of the three methods are compared.After weighing the advantages and disadvantages,the multiple sinusoidal disturbance injection method is selected for impedance measurement.Based on MATLAB/Simulink simulation environment,four representative simulation cases are designed in HUT side:(1)single-phase RLC load;(2)single-phase grid-connected inverter;(3)three-phase RLC load;(4)three-phase grid-connected inverter.The validity of the proposed impedance matching strategy is verified in these conditions.