Research On Decoupling Method And Harmonic Characteristic Of Controllable Reactor Of Transformer Type

Controllable Reactor of Transformer Type(CRT)is an important compensation device to ensure the reactive power balance and voltage stability of high voltage transmission system.Current research on CRT shows that the current of each control winding can not be maintained at its rated value under most operating conditions because of the electromagnetic coupling between the windings of CRT,which would cause serious waste of winding material.Therefore,complete realization scheme of decoupling operation mode is proposed again based on the idea of decoupling operation mode in this thesis.Decoupling operation mode is compared with sequential single branch operation mode,and its superiority is analyzed.In this thesis,the following aspects are mainly researched: improvement of winding current calculation model of CRT,solution of current-limiting inductance of CRT under decoupling operation mode and sequential single branch operation mode,the realization scheme of decoupling operation mode,harmonic optimization of CRT under decoupling operation mode.The above works have laid the foundation for good operating performance of CRT.(1)The existing calculation model of winding current is inaccurate and inconvenient to use.On the basis of the above problem,the adjustment range of each thyristor is segmented and instantaneous current calculation model of each winding of CRT is reformulated and improved.Then,the effective value calculation model of each winding current of CRT is obtained by Fourier decomposition.(2)Under decoupling operation mode,according to that each control winding voltage is equal to each current-limiting inductance voltage,winding voltage formulas are listed,and the first calculation method of current-limiting inductance is derived by the derivation of the voltage formula.Then,according to the characteristics of the decoupling operation mode,the winding current calculation model is simplified,and the second calculation method of current-limiting inductance is obtained by solving the winding current equations.Finally,current-limiting inductance is calculated by two methods in the example,and the correctness of two methods is verified by each other.(3)Under sequential single branch operation mode,in view of the shortcoming of the existing current-limiting inductance calculation method,the current-limiting inductance calculation model is established by using the winding current calculation model.Finally,the current-limiting inductance is obtained by solving the nonlinear equations,and the correctness of the proposed method in this thesis is verified by comparing with the existing recursive algorithm.(4)After analyzing the coupling effect between CRT winding currents,according to the rated current of the each control winding,the regulating range is graded,and the current ofevery control winding is discrete.Then,based on the winding current calculation model of CRT,a new realization scheme of decoupling operation mode is proposed and realized by an example.(5)The harmonic current calculation formula of CRT is given.Under decoupling operation mode and sequential single branch operation mode,the harmonic distortion rate,the harmonic coefficient and the harmonic current effective value of CRT are analyzed and compared by an example.Finally,the harmonic current under decoupling operation mode is optimized by changing the rated current of each control winding.And optimization result is compared with the harmonic under sequential single branch operation mode.