Optimal Design For High-frequency High-voltage And High-power Electrostatic Precipitators Power Supplies

For LCC series-parallel resonant converter(LCC-SPRC), the leakage inductance and the winding capacitance of transformer can be used as parts of series resonant inductor and parallel resonant capacitor, which can weaken the unfavorable effects of parasitic parameters on the converter. LCC-SPRC is considered to be appropriate for high frequency, high voltage and high power applications, such as electrostatic precipitator(ESP) power supply with capacitive load.Zero-voltage-switching(ZVS) can be achieved for LCC-SPRC working in continuous current mode. However, losses are generated in the turn-off process with the large off current for the low-voltage and high-current operation. Another drawback is that a high switching frequency is required for the light load operation which makes it difficult to design the magnetic components. Therefore, a novel control method named variable frequency phase-shifting control(VF-PS control) is introduced. The output power is controlled by the duty cycle and the switching frequency is automatically adjusted to ensure zero-current-switching(ZCS) of one bridge leg. The method combines the advantages of both phase-shift(PS) control and variable-frequency(VF) control, aiming to narrow the switching frequency variation and to reduce the switching power losses to improve the efficiency of the converter.The trial and error method which is usually used in the engineering applications has poor theoretical guidance to design the controller. A fifth order small–signal model for LCC-SPRC under VF-PS control is established based on generalized averaging method which provides a theoretical basis for controller designer. The design method is considered to be valuable for theoretical guiding. Meanwhile, a steady state model under VF-PS control is developed based on first harmonic analysis method. On this basis, the circuit’s operation characteristics are analyzed and the optimal parameter design is achieved. In addition, a design method for the semiconductor power losses model is discussed. The losses model is obtained according to the relevant data in the semiconductor’s datasheet. Simplification and high accuracy can be achieved without modeling for semiconductor.A 1k VA experimental platform of the ESP power supply is built based on F28335 control. The feasibility experiment of VF-PS control strategy is implemented. The results illustrate that ZVS and ZCS can be achieved under the VF-PS control. For novel VF-PS control and traditional VF control, voltage regulation experiments under constant load and variable load are completed. The results illustrate that VF-PS control has better voltage regulating features. The high accuracy for the semiconductor power loss model is proved through experimental verification. What’s more, the comparative experiment about semiconductor loss between novel VF-PS control and traditional VF control shows that the former significantly lowers switching losses and conduction losses.