带混合负载的电动无人机双极性直流电力系统拓扑结构设计及稳定性分析

Topology Design and Stability Analysis of Bipolar DC Power System of Electric Unmanned Aerial Vehicle Feeding Mixed Load

电动无人机的直流电力系统主要为推进电机、环控和雷达等机载设备提供可靠的电能,而根据系统母线的结构,可以将系统分为单极性结构和双极性结构。为了降低推进电机的损耗和体积、提高系统容错性,双极性结构被广泛地应用在无人机和飞机当中。然而由于燃料电池、光伏等新能源发电系统通常输出单极性直流电,需要一个单双极性转换接口,实现单双极性转换。首先在电感电流脉动量、电容电压脉动量和开关管应力等方面,对比分析两种单双极性转换接口,即电压平衡器和多电平变换器。然后,基于对比结果,选取多电平变换器作为单双极性接口,设计母线电压控制器和中位点电压控制器实现双极性直流电力系统的电压电流控制和电压均衡控制。最后,分析控制器参数以及广泛存在于系统中的恒功率负载、恒流负载、恒阻负载对系统稳定性的影响,并通过仿真进行验证。

The DC power system of electric unmanned aerial vehicles(UAVs)mainly provides reliable power for airborne equipment such as propulsion motors,environmental control systems,and radar.According to the bus scheme of system,the DC power system can be divided into unipolar architecture and bipolar architecture.To reduce the loss and volume of a motor and increase the fault tolerance of the system,bipolar architecture is widely used in UAVs and planes.However,since renewable energy generation systems such as fuel cells and photovoltaic usually output unipolar DC voltage,a unipolar-to-bipolar conversion interface is needed to realize unipolar-to-bipolar conversion.Firstly,two kinds of unipolar-to-bipolar conversion interfaces,namely voltage balancer and multilevel converter,are compared and analysed in terms of inductance current ripple,capacitor voltage ripple,and switch stress.Then,based on the comparison results,the multilevel converter is selected as the unipolar-to-bipolar interface,and the bus voltage and neutral-point-voltage controller are designed to realize the voltage and current control,and voltage balance of the bipolar DC power system.Finally,the effects of constant power load,constant current load,and constant resistance load widely existing in the DC system and controller parameters on system stability are analysed.The analysis result is verified by simulation.