| The explosive DC circuit breaker donated by French GHMFL has the characteristics of high breaking capacity and high reliability,which can be used as a protection switch in the power supply system.In order to make the breaker function properly,the charging and control system of it need to be re-developed.Based on the recent research status of the CCPS(capacitor charging power supply),the high frequency LC series resonant converter is chosen as the topology circuit of the CCPS which will be applied on the energy-storage capacitor of the breaker.The theoretical analysis of series resonant CCPS shows that in DCM(discontinuous current mode)the CCPS works in ZCS(zero-current switching)condition.And when switching frequency and DC bus voltage remain constant,the average charging current will remain a constant value as well,thus the constant-current charging under the open-loop control can be realized.The circuit parameters are designed according to the conclusion of theoretical derivation.The validity of the conclusion and the reasonability of the parameters are confirmed by the PSIM simulation.And the influence on the operation characteristics of series resonant circuit caused by the ratio of switching frequency to resonant frequency and the distributed capacitance of the transformer is also analyzed emphatically.Combined with the circuit parameters and the performance requirements of the DC circuit breaker for the CCPS,the detailed design and the components selection of the main circuit in charging system are accomplished.The design of the control circuit based on MC33066,the high performance resonant mode controller,is also completed,which can produce the drive signal,acquire and display the signal of voltage and current,realize the soft-start,provide over-charge protection and the failure protection for the system.Meanwhile,the control system based on S7-300 PLC is designed and the control flow is detailed introduced.Ultimately,the performance of the prorotype is tested through multi-groups charging experiments.It is conformed that the prototype of CCPS which basically meet the requirements of the design is able to operate safely and stably. |
