| With the expanding scale of power network.the problem of system stability between regional power grids has become increasingly prominent.In order to solve the problem of system oscillation and power angle stability,our group proposed the phase sequence exchanging stability control technology to suppress system oscillation and power angle swing.The series of operation of phase sequence exchanging such as opening,exchanging phase sequence and reclosing need to be completed in a very short time,so a circuit breaker which can be switched on and off quickly is urgently needed.Therefore,the research of solid state circuit breaker(SSCB)is carried out under the application background of exchange sequence technology.Firstly,a new type of AC solid state circuit breaker based on Insulated Gate Bipolar Transistor(IGBT)is designed.In order to improve the voltage sharing problem and peak voltage of series IGBTs caused by phase sequence exchanging,a new type of RCD voltage equalizing circuit is proposed.The advantages of RCD voltage equalizing circuit are verified by PSPICE simulation software.The work of solid state circuit breaker is described in detail.Based on this principle,the parameters of solid-state circuit breaker are designed,the simulation prototype of solid-state circuit breaker is built,and the short-circuit breaking test of solid state circuit breaker is carried out on PSPICE,which verifies the rapidity and reliability of solid state circuit breaker.Secondly,the transient characteristics of phase sequence exchanging process are analyzed,and a two-terminal power supply system model with solid state circuit breaker is constructed.The transient characteristics of voltage and current in three stages of phase sequence exchan ging technology application are deduced theoretically.The expressions of impulse voltage and impulse current in exchanging sequence process are obtained,and the optimal opening and closing time are analyzed.The correctness and feasibility of the theory are verified by MATLAB simulation.Finally,according to the conclusion of the optimal sw itching-on and closing time.two control modes of selection phase switching-closing and synchronous switching-closing are proposed.and a single-machine infinite-bus system is built.The phase sequence exchanging technology of two different control modes is applied to the oscillating power system,and the effect of the phase sequence exchanging technology of the two control modes to suppress the oscillation of the system is compared,which not only verifies the effectiveness of the phase sequence exchanging technology.In addition.a control scheme is obtained,which is give priority to selection phase switching-closing and is supplemented by synchronous switching-closing.The AC solid state circuit breaker developed in this paper not only can break the circuit quickly,accurately and without arc,but also does not need to restore the cooling time of insulation strength.It satisfies the requirements of the phase sequence exchanging technology which needs one or more phase sequence exchanging operations on the breaking speed,control accuracy and the function of multiple opening and closing in a short time.At the same time,the equalizing circuit of solid state circuit breaker is excellent.The voltage and current shocks caused by phase sequence exchanging can be effectively reduced by the control mode of selection phase switching-closing,and the effect of restraining system oscillation by phase sequence exchanging technology can be maximized. |
