Study On IGBT Switching Mode Excitation System Of Synchronous Generator Based On Soft Switch Technique

IGBT switching mode excitation of synchronous generator embraces the disadvantages of faultiness of IGBT driver & protect, large heat release, bigness of EMI. Aiming at these problems, ZCS-PWM soft-switching technique is introduced in main power circuit of this excitation system.Based on the demands of forcing excitation and realization the soft switching, choosing methods of resonance capacitance and resonance inductance are analyzed. TX-KA101 which is a new IGBT driver module is chosen as IGBT driver module, and the connect circuit of DSP to the driver module is designed too. The test results indicate that the performance of connect circuit and TX-KA101 is excellent.Make use of the powerful ability of data processing and high speed real-time control, integrate the abundant resources on-chip, aiming at the characteristic of IGBT switching mode excitation of synchronous generator main circuit, peripheric circuits and software of excitation controller are designed based on DSP. Based on the duty ratio which calculated by PID arithmetic and time process of series resonance, then time span of zero-current off of main switch and assistant switch. So realization method of ZCS-PWM is obtained. Also, this paper based on the require of excitation control, improve the position type discrete PID arithmetic of integral weakened when integral meet limit, and make use of the functions of compare interrupt and periodical interrupt of DSP timer, PWM pulse trigger method is presented.Some limit & protect functions of DSP excitation controller are designed in this paper too, which are based on the run requirements of excitation system. V/f limit, excess low excitation limit, over loading of reactive power limit, maximal excitation current instantaneous limit, force excitation by error on no-load state limit, excitation over-currentof inverse time lag delay limit programs are designed.Soft switching test of excitation main circuit indicate that the soft switch technique can obtain the goal in this excitation system. No-load and grid-connected test on small synchronous generator in laboratory, the performances of IGBT switch excitation controller based on DSP are excellent, all kinds of parameters can reach the requires of state standard.