Research On Interface Algorithm With Parameter Adaptability Of Power Hardware-in-the-loop Simulation For DC Grid

DC power grids are developing towards multi-terminal,networking,and having more and more power electronics in recent years.The dynamic behavior of the system is complex and the transient response is fast.There is an urgent need for flexible,accurate and fast simulation and testing methods.Among them,power hardware-in-the-loop simulation can not only simulate a large-scale,flexibly modified power grid environment,but also accurately reproduce the high-speed dynamic process of power electronic equipment.It is gradually becoming an effective means for basic theoretical research on DC power grids and testing of key power electronic devices.In power-in-the-loop simulation,the discretization of the simulation model and non-ideal hardware within interface will introduce additional delay to the power-in-the-loop simulation system,resulting in poor simulation accuracy,and even stability problems in severe cases.Therefore,it is necessary to design a suitable interface algorithm to compensate for this.First,the influences of commonly used interface algorithms on the system stability,accuracy,and noise suppression are analyzed.Relationship is established by comparing the two commonly used interface algorithms.Particularly,the modular multilevel converter(MMC)is taken as an example,to reveal the impedance characteristics of typical equipment in DC grid.On this basis,an improved interface algorithm based on frequency division is proposed by combining the advantages of commonly used interface algorithms.The compensation impedance form can be designed only by acquiring the partial impedance characteristics of the physical equipment,and the constraint range of its parameter is given.It is suitable for testing different DC grid equipment.When the physical system equipment changes,the designed interface algorithm may no longer be effective.For this reason,an online parameter optimization method of the interface algorithm is proposed.By obtaining the highfrequency impedance value of the physical equipment in real time and updating the compensation impedance parameters in time,the PHIL system can still run stably or quickly return to a stable state when the impedance changes.Finally,a DC grid power hardware-in-the-loop platform based on back-toback MMC is built.The proposed theory is fully verified based on this platform.