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Nowadays Static Synchronous Compensator (STATCOM) has gradually become one of the representative techniques in the field of dynamic reactive power compensation in the power distribution system. This paper analyzed the topology and the voltage imbalance problem of the up and down capacitors on DC side of the three-phase four-wire STATCOM. In allusion to the imbalance problem of neutral point, a novel control strategy based on the control of zero-sequence current was proposed. By the triple close-loop control strategy, the STATCOM can achieve great control accuracy and dynamic performance. Simulation result proves that the proposed control method is effective.

Nonlinear loads generate a large amount of characteristic harmonics , deteriorate the power quality of power distribution systems in Advanced manufacturing enterprises. In this paper a novel hybrid active power filter is proposed which consists of a series thyristor switched filter (TSF) and small rated shunt active power filter(APF). TSF is tuned at fifth and seventh order harmonic frequencies. Consequently APF compensates for third and other order harmonics, unbalance current and reactive power. A new control method based on PHC strategy is presented for APF. The device has already got an application in one of the transformer substations of a automobile factory. It’s revealed that the proposed device can improve the power factor , reduce the harmonics injection and enhancement power quality of the power distribution systems.

Nonlinear loads are widely spread in automobile industry along with the development of power electronic technology, which causes proliferation of power quality problems, such as harmonics, voltage fluctuation, etc. The problems result in detrimental effects to the power distribution systems, increasing power loss in the network and affecting the safety operation of electrical appliances. This paper analyzed the power quality problems and proposed an enhancement scheme implemented in an automobile factory. The scheme has already got an application in one of the transformer substations. It’s revealed that the proposed scheme can improve significantly the power factor of the 400V bus in car body workshop, and the harmonics injection to the utility grid can be within the limit of related standard．

This paper analyzes the construction and control principle of Thyristor Switched Capacitor(TSC) and Active Power Filter(APF) integrated device. An harmonics detection method based on the instantaneous reactive power theory is also discussed. This method is effective to apply to TSC&APF integrated device and can get better result to eliminate the harmonics and compensate reactive power. A new integrated device which consists of TSC and APF is developed with this method. The application in the automobile industry shows that this device is correct and effective. It is a favorable model of improving the power quality and save the energy.