Research On Induction Generator Variablespeed Constant Frequency Vehicle Power Supply System Based On Engine Driven Generating

With the growing number of on-board electrical devices and the continuous improvement of equipment precision, higher demands are proposed on the on-board power capacity and power quality. In order to solve this problem and not to introduce extra burden into relatively narrow vehicles, “engine driven generating” arises at the right moment. “Engine driven generating” means taking power from the vehicle engine and using it to drive the generator of the power supply system. Due to the poor road conditions and other various reasons, the speed of the vehicle engine is in a state of constant changing. In order to get a perfect on-board three-phase ac power supply with stable frequency and good quality, the variable speed constant frequency(VSCF) technology is a suitable scheme to be used. Taking this idea into consideration, this paper proposes an induction generator VSCF vehicle power supply system based on engine driven generating. It can output stable three-phase ac voltage when the engine speed changes and load condition is complex.Choose squirrel-cage induction generator which has features of simple structure, low cost and high reliability as the generator of system. Adopt back-to-back converters as the main circuit topology and use the split capacitor in the dc bus of the converter. On the one hand, cooperate the rectifier stage of back-to-back converter with induction generator to constitute an induction generator controlled rectifier power system; On the other hand, assort the inverter stage of the converter with spilt capacitor and output filter to make up a split capacitor three phase four wire inverter system. The two cascading subsystems make up the VSCF off-grid power system.The existence of the dc bus capacitor helps to decouple the rectifier and inverter stages of the converter, which means the system can be regarded as two independent subsystems. As a result, control strategies of the induction generator and the split capacitor three phase four wire inverter can be designed respectively to form the overall control strategy. Induction generator adopts the slip frequency control strategy, which can work without coordinate transformation and is suitable for wide speed range. Considering the characteristics of the split capacitor three phase four wire inverter, two different control strategies are proposed from the perspectives of changing voltage controller and changing the given voltage respectively, and both of them can realize single-phase voltage control. The one is double loop control strategy with proportional resonant(PR) voltage controller, and the other one is double loop proportional integral(PI) control strategy based on virtual dq transformation. The inverter subsystem can work normally with unbalanced loads when it applies either of these two control strategies. Then due to power balance thoery, the inverter's load power is added to the rectifier stage as a feedforward in the control loop to improve the performance of the overall system.At first, a simulation model based on Plecs is set up to verify the feasibility of the proposed scheme. Then, experiments under various conditions such as variable speed and unbalanced loads are carried out on a 30 k W experimental prototype. The experimental results show that the system has excellent dynamic and static characteristics.The results of the research in this paper show that the VSCF off-grid power system based on engine driven generating would be an excellent choice for the vehicle power supply system and owns good development and application prospects.