Research On Three-Phase Harmonic Energy Extraction Circuit

With the development of industrial technology, harmonic pollution is becoming severity in power system. We usually adopt passive filter and active filter to filter the harmonic in power system, and make sure the harmonic distortion rate satisfy the national standards. However, the harmonic voltage and harmonic current are also kinds of energy, merely its frequency is not the same as the fundamental frequency of the grid. The harmonic energy of power grid can be extracted and utilized, meanwhile realize using the harmonic energy and filter the harmonic at the same time.This paper proposes a new method of harmonic extraction, which base on the harmonic sequence characteristics and the principle of fundamental magnetic flux compensation, and combined the single-tuned filter circuit and three-phase transformer to extract harmonic energy. A single-tuned filter circuit in series with the primary winding of the transformer, and they are paralleled in power system as a whole to filter harmonic, meanwhile extract grid harmonic energy from the secondary winding of the transformer. A fundamental tuned circuit is paralleled with the primary winding of the transformer. The equivalent impedance of the fundamental turned circuit at fundamental frequency is zero and bypasses the capacitive fundamental current, meanwhile makes the harmonic extraction circuit as a short circuit, achieves the goal of extract harmonic energy without consuming fundamental energy. A transformer based on the fundamental magnetic flux compensation series between the grid and the passive filter to improve harmonic impedance of grid, force more harmonic current flow into passive filter and maximize the harmonic extraction.Finally, the harmonic energy extraction model is built and its working principle is analyzed. Using MATLAB built the harmonic energy extraction model, by means of simulation, this model realize extract the fifth and seventh harmonic energy from power grid without consuming fundamental energy, and provide power to load as a three-phase source. The simulation results verify the feasibility and correctness in theory of this method.