Harmonic Analysis And Suppression Methods Study Of Cycloconverter Synchronous Motor Drive System

In industrial production, cycloconverter-feed synchronous motor vector control system has already been developed to be a certain trend of large rolling mill main drive. But its harmonic problem can not be ignored when running this system. During the period of June 28 to July 1 in 2003, power quality testing and analysis on the power grid of Middle-broad Plant of Chongqing Steel Group Corporation was performed. From the testing report, it can been seen that the refine rolling mill system will inpour badly harmonic to the power grid, which will affect the normally function of power grid. To solve the problem, researches on the theory of refine rolling mill cycloconverter-feed synchronous motor vector control system are carried out, while the characteristic of this system are analyzed and the model of air-gap flux orientation control system of synchronous motor is set up. This paper does simulation analysis of this model, especially emphasizes on harmonic analysis of the power grid. And some changing rules and influencing factors of this vector operation system are deduced. Practice testing, theory analysis and simulation results all indicate that cycloconverter-feed synchronous motor vector control system inpours vast harmonic to the power grid.Active power filter (APF) is a new power electronic device used to restraining harmonics and compensating reactive power. APF can achieve dynamic compensation for harmonics and reactive current, and the compensation performance is not affected by the impedance of power grid, it has advantages as follows, fast response, high controllability and adaptability, etc. Brief illuminations of advantages and disadvantages are performed to various harmful current detecting methods and control techniques. A new harmonic current detecting method is brought forward, namely ip-iq harmonic current detecting method without phase lock loop (PLL). In addition, the basic theory of one-cycle control is introduced and the key control equations are derived. Model of APF based on ip-iq harmonic current detecting method & one-cycle control technique and three-phase three-wire APF based on one-cycle control are set up with PSIM software, and simulation analyses are performed.On the other hand, APF with vector operation of Unified Constant Frequency Integration (UCI) control is presented in this thesis. Circuit model of APF with this method is set up with PSIM. Simulations are performed with this kind of APF applied to different nonlinear loads, including cycloconverter load. Load-adaptabilities of this APF...