关键词: 氢燃料电池堆, DC-DC变换器, 等效阻抗, 滑模预测控制, 变步长线性查表法

Abstract:

In hydrogen fuel cell vehicles, the Fuel Cell DC-DC converter (FDC) is a key interface between the hydrogen fuel cell stack(hydrogen stack) and the inverter, and the stability of its output DC bus voltage is a key link to ensure the normal operation of loads such as the motor. So, a new type of sliding mode predictive control is proposes in this article. Firstly, the topology of FDC is improved and a predictive model based on sliding mode surface is established. Then, a sliding mode surface value function is designed to improve the tracking accuracy of FDC; On this basis, in order to achieve online intelligent monitoring of the hydrogen reactor, the variable step linear interpolation lookup table method is further adopted to accurately estimate the impedance of the hydrogen reactor online. Firstly, the FDC is digitally controlled to generate small sinusoidal harmonics with variable frequency, and the multi frequency impedance value of the hydrogen reactor is estimated based on the input voltage and current sampling of the FDC; Then, the variable step linear interpolation lookup table method is used to compare the estimated impedance value with the design standard value, evaluate the current state of the hydrogen reactor, and achieve online intelligent monitoring of the hydrogen reactor. Finally, simulation and experimental verification will be conducted. The results show: ①When the experimental reference current is set to 100 A, The system current overshoot and response time under traditional PI control are 20 A and 15ms, respectively. In contrast, the system current overshoot and response time under sliding mode predictive control are 1.5 A and 2.5 ms, respectively; ②The tracking accuracy of FDC for self generated harmonics can be controlled within 2%; ③The variable step linear interpolation lookup algorithm can achieve accurate estimation of fuel cell impedance. Verify the effectiveness of the algorithm.

Key words: hydrogen fuel electric reactor, DC-DC converter, equivalent impedance, sliding mode predictive control, variable step linear table lookup method