Research On Harmonic Current Detection And Control Based On Variable Step Size LMS Algorithm

With the rapid development of power electronic technology,various nonlinear load also gradually plays an indispensable role in people’s production and life,leading to the problem of harmonic in power system is becoming more and more serious,the problem of harmonic pollution has been the impact of power quality in power system is an important factor,always haunt the power related workers,At present,the most commonly used method for harmonic control is passive harmonic control scheme,among which Active Power Filter(APF)has been widely used for its advantages of rapid and accurate harmonic current detection and timely compensation.The two most important links in APF are harmonic current detection and harmonic current tracking compensation.And harmonic governance is the premise of must quickly and accurately detect the harmonic current,as the need for compensation,and then to detect harmonic harmonic current signal,through the high frequency switch control circuit to drive the main circuit device to make it produce a same as the harmonic current amplitude,frequency,equal and opposite current signal of two signals after stacking offset each other,The harmonics in the system can be eliminated,so as to achieve the purpose of harmonic control.Firstly,in the aspect of harmonic current detection,this paper focuses on the mathematical models of the most commonly used recursive least square algorithm(RLS)and least mean square algorithm in the adaptive algorithm,through the mathematical model analysis of their respective advantages and disadvantages,and then use the programming simulation,According to the simulation results,the convergence speed,steady-state accuracy and algorithm complexity of the two algorithms are analyzed and compared.After that,the most widely used variable step size adaptive algorithm and its fixed-step size algorithm are analyzed and studied in this paper.Finally,the variable step size least mean square algorithm is selected as the main research algorithm in this paper.The mathematical model is built and its performance is analyzed and verified by comparison.The algorithm used in this paper has good performance in terms of convergence speed,steady-state accuracy and computational complexity.Secondly,in terms of control strategy,this paper selects the hysteresis comparison tracking control strategy for harmonic current tracking compensation,and at the same time,the DC side voltage and other parameters of the main circuit are studied and analyzed.Finally,the proposed algorithm and the selected control strategy are simulated and analyzed,and the APF model is verified by the actual working conditions of a pumping unit well in Daqing Oilfield.From the simulation results,the method used in this paper has a good governance effect on the harmonic current,thus verifying the correctness of the conclusion in this paper.