一种适用于航空DC/DC变换器短路限流的控制策略

针对航空变换器在负载短路时需要输出3倍额定电流的要求,提出了一种适用于航空DC/DC变换器短路限流的控制策略。在传统电压-电流双环控制DC/DC变换器的基础上,引入输出电压前馈控制,即将输出电压作为前馈信号,与电流控制器的输出信号相加共同作为调制信号与三角载波交截。通过合理设计前馈系数,保证电流控制器的输出电压在负载短路前后基本保持不变,旁路了PI补偿网络的延时影响,使得短路瞬间占空比即时修正,有效抑制了短路瞬间的电流冲击。小信号建模分析表明,输出电压前馈的引入基本不会影响原双环控制系统的稳态和动态性能。仿真和实验均验证了该控制策略的有效性。

An Improved Control Method for Aviation DC/DC Converter with Overshoot Suppression under Shorted Load

For double-loop controlled Buck converter, the output of the voltage controller provides the maximum current-limiting signal in order to achieve over-current protection when the load shorted. However, due to the delay characteristics of PI compensation network, the current-overshoot maybe occur and damage the power devices. In this paper, an improved control method is proposed to suppress the current-overshoot. The output voltage is taken as the feed-forward input signal, which is added with the output of the current controller as the modulation signal to achieve intersection with the triangle wave. Through rational design of feed-forward coefficient, it can be ensure that the output of the current controller is roughly constant when the load shorted, which bypasses the delay effect of PI compensation network and corrects the duty cycle instantly, so the current-overshoot can be suppressed effectively. Small signal modeling shows that output voltage feed-forward (OVFF) control does not affect the steady-state and dynamic characteristics of the original double-loop control system. The effectiveness of the proposed control method is verified by both simulation and experiment.