A Wide Output Range Three-Phase LCC Reasonant Converter

In some certain applications, the output voltage of the converter need continuous adjustment over a wide range, and the converter can realize constant power output at a certain working period. Based on the three-phase LCC resonant converter, a resonant converter with pulse frequency modulation is designed in this thesis.Compared with the usual converter with wide range output and the single-phase LCC resonant converter, three-phase LCC resonant converter has a small output ripple, is easy to achieve soft switching and suitable for high-power applications. ZVS soft switching characteristics and output current ripple characteristics are discussed through analyzing the operating modes and features of single-phase and three-phase LCC resonant converter.An equivalent mathematical model with the fundamental component method is established in this thesis. The model is only related to the switching frequency, load and transformer gain. According to this model, this thesis discusses the impact of quality factor and resonant element parameters on the resonant converter gain curve and ZVS soft switching. Then the reasonable working area of the converter is achieved.The rationality of the converter working area is verified by simulation and experiment. An experimental prototype is designed with input voltage of 100 V, output voltage of 150V-300 V, output power of 420 W and frequency range of 100 k Hz-115 k Hz. Digital frequency control is used to achieve closed-loop control. Measurement results at different load conditions and output voltage level verify the correctness of theoretical analysis and the rationality of design parameters. Finally,the stability and rapidity of the closed-loop control system is verified, the experiment achieves the expected results.