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AC electrified railway system is a huge single-phase load, which causes significant power quality (PQ) problems to the upstream power grid. Active railway PQ conditioners (ARPQC) have been introduced to overcome the PQ problems. One of the most important complications of the ARPQCs is its high VA rating which entails significant escalation in the price of the conditioner. To mitigate the rating of the ARPQC, a hybrid configuration including an asymmetric balancing traction transformer and a half-bridge railway PQ conditioner (HBRPC) is proposed in this study. The predictive deadbeat current control with low computational burden and fast dynamic response is used to optimise the performance of the HBRPC. Additionally, a PI adaptive gain controller is proposed for DC-link voltage stabilisation, which minimises the negative impact of the voltage control on the current control stage. The feasibility and functionality of the proposed scheme is validated via simulation and experimental results. [ABSTRACT FROM AUTHOR]

In recent years, the harmonics and unbalance problems endanger the voltage and current quality of power systems, due to increasing usage of nonlinear and unbalanced loads. Use of Distributed Generation (DG)-interfacing inverters is proposed for voltage or current compensation. In this paper, a flexible control method is proposed to compensate voltage and current unbalance and harmonics using the distributed generation (DG)-interfacing inverters. This method is applicable to both grid-connected and islanded Microgrids (MGs). In the proposed method, not only the proper control of active and reactive powers can be achieved, but also there is flexibility in compensating the voltage or current quality problems at DG terminals or Points of Common Coupling (PCCs). This control strategy consists of active and reactive power controllers and a voltage/current quality-improvement block. The controller is designed in a stationary (aß) frame. An extensive simulation study has been performed and the results demonstrate the effectiveness of the proposed control scheme. Depending on the compensation modes, the harmonics and unbalance compensation of DG output current, MG-injected current to the grid, as well as PCC and DG voltages, can be achieved in grid-connected operation of MG while in the islanded operation, and the PCC and DG voltages compensation can be obtained through the proposed control scheme. [ABSTRACT FROM AUTHOR]

In this paper operation of a hybrid active filter consist of a shunt active filter and distributed passive filters in a simple distribution system is investigated. The test system contains nonlinear loads among with passive filters to eliminate certain harmonics of the load current and also to supply reactive power. A micro turbine unit is also considered as a DG in the test system. The active filter is utilized and controlled to eliminate the remaining harmonics of the supply current and to correct the current unbalance. In order to examine the operation of the compensation system, simulations are carried out using Matlab/Simulink software. Simulations are conducted under different cases including the operation of passive, active and hybrid filters individually and in combination. Simulation results demonstrated the effectiveness of the described hybrid structure to improve the power quality indices of the system under study. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid power quality solution in a test system consisting of distributed passive filters, an Universal Power Quality Conditioner (UPQC) and Distributed Generation (DG) units. In the system, single passive filters are designed and connected to eliminate main harmonics and compensate reactive power for each nonlinear load. The UPQC is utilized for voltage unbalance compensation and cancellation of the remaining current harmonics at the point of common coupling of the power distribution system. Configuration of the test system, nonlinear loads, DGs, active filters and UPQC and their modeling in Matlab software are presented in this paper. Matlab implementation of the control system based on dq reference frame theory is also described. Frequency response of the given system is performed and presented to study the issue of resonance under harmonic conditions. Simulation results are demonstrated and confirmed the effectiveness of the proposed configuration in simulated test system. It is shown that the UPQC rating can be reduced in the proposed configuration due to the reactive power compensation using passive filters. [ABSTRACT FROM AUTHOR]