Research On The Comprehensive Compensation System For The Power Quality Of High-speed Electrified Railway Based On V/v Transformer

As a result of the unique power supply mode and complex operating conditions ofelectric locomotive, the traction power supply system brings in serious power qualityproblems, for example, negative sequence current, harmonics and voltage fluctuations. as aresult of national economic loss，lowing the efficiency of energy, and endangering the stableoperation of electrical equipment, even cause serious electrical accident, resulting in regionalpower outage or equipment damage, which are serious losses of national economy.In this paper, the traction load-characteristics of AC-DC-AC electric-locomotive ofhigh-speed electrified railway is firstly analysed. Then, a detailed study is under-taken on theworking principle, operating characteristics and power quality problems generated bysimple-operation of the electric-locomotive, including the negative sequence currentmechanism under a variety of traction transformers, the unbalance of grid current, harmonicsand voltage fluctuations, which provide a good instruction for the compensation system tocontrol the power quality of high-speed railway.The Comprehensive Compensation System proposed in this paper is constituted by3part,which is railway power conditioner (RPC) parallel with thyristor controlled reactor (TCR) andthyristor switched capacitor (TSC). With this topology, compensation principle of negativesequence current, reactive power allocation strategy, the detection method of negativesequence current and harmonic compensation current, and the RPC control strategies are alsostudied detailly. Finally, a1/100capacity experimental prototype and the corresponding softplatform and hardware platform are also developped for the experimental verification. Thework in this paper will provide theoretical and engineering reference for high-speed railway.As the topology of the compensation system fundamentally determines governanceschemes of the power quality, it is the prerequisite to analysis and study the power quality ofthe high-speed railway. To achieve a prefect control effect, a high-speed railwaycompensation system constituted by railway static power conditioner (RPC) parallel withthyristor controlled reactor (TCR) and Thyristor Switched capacitor (TSC) is proposed in thispaper under a careful analysis.The compensation principle, appropriate compensationstrategies and electrical equivalent model is discussed followed by. Finally, the simulationand a1/100capacity experimental prototype are developped to verify the correctness and effictiveness of the compensation system.The control effect of the Comprehensive Compensation System has a great relationshipwith its control strategies, as a result, seeking a simple and effictive control strategy is veryimportant. In this paper, a dual-loop control strategy consisted of DC-voltage outer loop andinner current loop is adopted. To the control of the DC-voltage, the core is to ensure that theenergy of the storage capacitor absorbed is equal to the energy of the storage capacitorreleased. On the consideration of the voltage fluctuations on the DC side, a PI control methodwith parametrics dynamic adjusted is proposed to supress voltage fluctuation. In the practicalengineering application, better control strategies for AC signal tracking is hysteresis controlstrategy and deadbeat control strategy, so the simulations using these two control strategies isrespectively conducted to compare the control effects. Because of deadbeat control strategyhas a better control effect when the carrier frequency is low, the experiments adopt deadbeatcontrol strategy preferentially.