Research On MMC-RPC Modeling And Power Quality Control

Due to the temporal shift,nonlinearity,and volatility of electric locomotives,the power quality issue of the traction power supply system is becoming more and more evident with the continual increase of railway speed and power.In order to efficiently address power quality issues in the traction power supply system,such as negative sequence,reactive power,and harmonics,RPC demonstrates a promising application promise.However,the traditional railway power conditioner is limited by its insulation level and compensation capacity.It needs to be matched with a step-down transformer before it can be connected to the traction network.In order to overcome the shortcomings of traditional RPC,this article uses MMC to form MMC-RPC.With all the advantages,it also has the advantages of high withstand voltage level,large compensation capacity,excellent dynamic and static performance,and direct connection to traction network without step-down transformer.This article conducts indepth research on the MMC-RPC modeling and power quality control of the traction power supply system applied to V/V traction transformers,and carries out the following work:(1)Establish the mathematical model of MMC-RPC.The three operational states of MMC half-bridge sub-modules are investigated,together with the structure and compensation principle of the V/V traction transformer,the derivation of the current and power compensation commands,and the topology of the three-phase and single-phase MMC.By using SOGI to create orthogonal virtual quantities,the mathematical model of single-phase MMC in the rotating coordinate system is derived based on the principle.(2)A rapid sort algorithm-based MMC composite sliding mode control approach is suggested.Because the conventional sorting method is inefficient and uses a lot of system resources,the quick sorting algorithm is used to sort the capacitor voltages by using the divide-and-conquer technology,so as to improve the system’s operating speed and dynamic response characteristics,and reduce the computing resources occupied by capacitor voltage equalization.Aiming at the problems of the traditional PI control of three-phase MMC,the slow response speed of sliding mode control,and large overshoot,it is proposed to combine the sliding mode controller with the extended state observer,and use the extended state observer without an accurate model to simulate the three The disturbance amount in the transient state during the input process of the phase MMC can improve the response speed of the system and reduce the overshoot.Finally,the effectiveness and superiority of the MMC compound sliding mode control strategy based on the quick sorting algorithm are verified by simulation.(3)A new control strategy of MMC-RPC based on multidimensional Taylor net is proposed.MMC-RPC is a multivariable,strongly coupled,nonlinear system.When the disturbance is large,MMC-RPC under traditional PI control cannot accurately eliminate the transient stability error of the system.Therefore,it is proposed to apply MTN optimal control to MMC-RPC.Aiming at the parameter tuning problem of multiple terms of MTN controller,the integral of the dq-axis current reference value and the square of the actual value error is used as the output performance index,and the parameters in MTN are iteratively optimized by using particle swarm optimization algorithm.It is verified by simulation that the MMCRPC using the MTN controller has stronger anti-disturbance ability,better robustness,lower harmonic distortion rate and shorter adjustment time than the PI control under the two complex working conditions.