Load compensators are used for reactive power compensation as well as harmonic compensation have the disadvantage of high cost and poor efficiency due to switching losses. So it is good to use active harmonic filters for harmonic compensation and traditional methods comprising of thyristor-switched capacitors for reactive power compensation. Existing load compensators have the capability to differentiate between the fundamental reactive component and harmonic components of the load currents ,but are complex and so they are not cost effective. In order to overcome this limitation, a shunt harmonic filter, which is capable of compensating only the harmonic components of the load current and having a simple control circuitary is proposed in this paper.
I.INTRODUCTIONA shunt load compensator is used for harmonic current requirement of the nonlinear load can additionally provides reactive power support for power factor correction and/or voltage regulation As the load compensator supplies the reactive component of the load current along with harmonics, it is required to be rated to carry the reactive component of the load current also. Moreover, the high bandwidth requirement of the controller which forces the compensator to supply the harmonic component of the load current necessitates the semiconductor switches to operate at high switching frequencies Operation of semiconductor devices at high switching frequency while they carry large current leads to increment in device current rating and switching losses. The increased rating makes the load compensators expensive.The objective is to overcome this limitation is by providing compensators that act as active harmonic filters (AHFs) to compensate only for the harmonic components of the load current, while traditional methods comprising of thyristor switched capacitors/reactors are used to carry out reactive power compensation of the given load. So the converter of an AHF has to carry only the harmonic components of the load current, its current rating and the incurred power loss are less compared to that of a load compensator.In this paper, it proposes an efficient and simple control scheme for harmonic elimination using shunt active filter. It is capable of compensating only the harmonic components of the load current .So the losses can be minimized and also the cost.
II.LITERATURE SURVEYThere are so many methods for harmonic elimination. Some of these methods [1],[2] require the information of the fundamental component of the grid voltage to extract the harmonics present in the source current. The grid voltage is likely to contain distortions, including multiple zero crossings, and the service of a phase-locked loop (PLL) is employed to extract the fundamental component of the grid voltage. These methods also require separate harmonic resonance generator and current controller. Some other methods [3],[4] except [5], [6] cannot differentiate between the reactive component and harmonic components of the load current. Some methods [7] has the flexibility to ...