Research On High Voltage Capacitor Charging Power Supply Based On Series-parallel Resonant Converter

Not only is the support technology of high power pulse radiation physics, controlled nuclear fusion physics and high-energy density physics, pulsed power technology is also widely used in high and new technology industry and new weapons, for example, radiation sterilization, gas cleaning, bioengineering, electromagnetic pulse weapons and so on. Capacitors have become the most common energy storage element due to simplicity, reliability and mature technology. As a result, it is significant to research the control strategy and the appropriate topology of capacitor charging power supply(CCPS).Because of merits like compact size, high power density and high efficiency, resonant converters have become the preferred topology for CCPS. In all resonant converters, series resonant converter(SRC) is the most common and mature topology, because it has a lot of merits like soft switching, simplicity of control, pure current source peculiarity and so on. However, the working characteristics of SRC will change with parasitic capacitance and leakage inductance of the high voltage transformer affecting. In addition, the voltage gain of SRC is less than one, which is not beneficial to boost voltage of CCPS.For these reasons, this thesis selects series-parallel resonant converter(SPRC) as the topology of CCPS. SPRC not only possesses advantages of SRC, and also absorbs parasitic parameters of high voltage transformer as its resonant elements. Besides, its voltage gain is larger than one.At first, working principle of SPRC working in current continuous mode is analyzed in this thesis. There are three working modes and their advantages and disadvantages are discussed. Then the forced-type commutation mode is selected as the best working mode. Secondly, the large-signal model of SPRC is builded with extended describing functions. Then the steady-state model and equivalent circuit of SPRC for steady-state condition are derived from the large-signal model. With the steady-state model, the boundary of forced-type commutation model is deduced. It is studied that how relevant parameters like the quality factor of the load, the switching frequency and the parallel resonant capacitor, influences the characteristics of SPRC, by the means of two-dimensional diagrams. Moreover, soft switching principle of SPRC is analyzed.According to the characteristics of SPRC, on the basis of considering the peal value of voltage and current in the resonant tank, voltage gain and charging current, the design method of CCPS is proposed, and a constant-current charging scheme on the basis of variable frequency control is designed. For verifying the model and the control scheme, a simulation is made.Finally, a 30 kV, 825J/s prototype is proposed. The theoretical analysis and the proposed control method are experimentally confirmed.