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This paper proposes an improved hybrid distribution static compensator (DSTATCOM) topology to address some practical issues such as power rating, filter size, compensation performance, and power loss. An $LCL$ filter has been used at the front end of a voltage source inverter (VSI), which provides better switching harmonics elimination while using much smaller value of an inductor as compared with the traditional $L$ filter. A capacitor is used in series with an $LCL$ filter to reduce the dc-link voltage of the DSTATCOM. This consequently reduces the power rating of the VSI. With reduced dc-link voltage, the voltage across the shunt capacitor of the $LCL$ filter will be also less. It will reduce the power losses in the damping resistor as compared with the traditional $LCL$ filter with passive damping. Therefore, the proposed DSTATCOM topology will have reduced weight, cost, rating, and size with improved efficiency and current compensation capability compared with the traditional topology. A systematic procedure to design the components of the passive filter has been presented. The effectiveness of the proposed DSTATCOM topology over traditional topologies is validated through both simulation and experimental studies. [ABSTRACT FROM PUBLISHER]

This letter presents a dynamic hysteresis current control algorithm for a three-phase four-leg voltage-source inverter (VSI) topology. In order to improve the performance and life of the power switches of VSI, we require an optimized control technique that reduces its switching frequency. Proposed hysteresis current control method is a generalized control method that minimizes switching operations to compensate nonlinear load under both balanced and unbalanced supply voltages. It is shown that this control scheme is able to reduce the switching frequency by more than 50% compared to conventional hysteresis current control method and retain the quality of load compensation. The effectiveness of the proposed control scheme is illustrated through simulations using Power Systems Computer-Aided Design (PSCAD) 4.2.1. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study on the design and analysis of user-defined constant switching (UDCS) frequency current-control-based four-leg distribution static compensator (DSTATCOM). The three phase legs of its voltage source inverter are operated in hysteresis current tracking mode whereas the fourth leg is controlled by a square switching pulse of user-defined frequency. Consequently, the switches of the other three legs also get tuned to this user-defined frequency. Analytical expressions are derived that prescribe the range of frequencies for which the scheme works effectively. Design procedure is also suggested for the selection of the parameters of the four-leg inverter such as dc-link voltage, dc-link capacitor, interface inductor, and hysteresis band. Simulation and experimental studies are conducted to validate the proposed design procedure for a UDCS-controller-based DSTATCOM. Its performance is compared with a conventional hysteresis-controlled DSTATCOM. [ABSTRACT FROM AUTHOR]

In this paper, design aspects of various passive components and switching dynamics of a voltage source inverter (VSI) for compensating unbalanced and nonlinear load are presented. The design method for VSI to track desired reference currents smoothly, is illustrated. By using the proposed method, it is possible to design the passive components of different VSI topologies used for load compensation. The results are supported by detailed simulation studies on a three-phase four-wire compensated system using PSCAD 4.2.1. The design steps are also verified by conducting experiments using a prototype model developed in the laboratory. [ABSTRACT FROM AUTHOR]

The paper presents the operating principles of a distribution static compensator (DSTATCOM) that is used to maintain the voltage of a distribution bus. A three-phase, four-wire distribution system is assumed in this study. A three-phase bridge inverter circuit that is supplied by two neutral-clamped dc storage capacitors realizes the DSTATCOM. Three filter capacitors, one for each phase, are connected in parallel with the DSTATCOM to eliminate high-frequency switching components. The voltage across the filter capacitor is controlled by a dead-beat controller to maintain the ac bus voltage. The magnitude of the bus voltage is chosen as nominal value, i.e., 1.0 p.u., while its phase angle is obtained through a feedback loop that maintains the voltage across the dc storage capacitors. Through detailed simulation and experimental results, it has been shown that the DSTATCOM can maintain the voltage against any unbalance and distortion in either the load or supply side. [ABSTRACT FROM AUTHOR]