Qihong Chen

Nonlinear predictive control for oxygen supply of a fuel cell system

This paper presents a neural network predictive control strategy to optimize oxygen supply for a proton exchange membrane fuel cell system. We propose using a time varying and local linearization auto-regressive moving average with exogenous (ARMAX) to model the nonlinear system, and employing recurrent neural network to estimate coefficients of the ARMAX model. Then constrained linear model predictive algorithm is presented to optimize oxygen supply of the fuel cell system, which significantly simplifies implementation and can handle multiple constraints. Study results demonstrate that the modeling and control strategy are effective.

Neural Network Based Multiple Model Adaptive Predictive Control for Teleoperation System

Environment model and communication time delays of a teleoperation system are variant usually, which will induce bad performance, even instability of the system. In this paper, neural network based multiple model adaptive predictive control method is proposed to solve this problem. The whole control system is composed of predictive controller and decision controller. First of all, neural network model set of any possible environment is built up, and time forward state observer based predictive controllers are designed for all models. In succession, decision controller is designed to adaptive switch among all predictive controllers according to performance target. This method can ensure stability and performance of the system. Finally, simulation results show effectiveness of the proposed method.

Model Predictive Control for Three-Phase Four-Leg Grid-Tied Inverters

In order to improve the quality of the power injected into a grid, this paper presents a model predictive control strategy for three-phase four-leg grid-tied inverters. For the convenience of optimization, the discrete-time model of the inverter in which duty ratios are modeled as continuous control variables is investigated. A current tracking error oriented cost function is employed as a criterion to optimize duty ratios of the inverters. In order to eliminate the effects of sampling delay, a model predictive control with delay compensation method (MPC-DC) is proposed. Because there is a large amount of calculations in implementing predictive control algorithm, a double-CPU, namely FPGA plus DSP controller, is employed to implement parallel calculation, so as to reduce the computation time. Simulation and experimental results demonstrate the effectiveness of the proposed method.

Sliding mode control of a phase shifted full bridge DC/DC converter

In order to improve steady and dynamic characteristics, a sliding mode control for a phase shifted full bridge DC/DC converter with fixed switching frequency is presented. Mode of the full bridge DC/DC converter is established by averaged current method. Linear combination of output voltage and its differential and integral is chosen to design sliding mode surface. The proposed algorithm is validated through MATLAB/Simulink. Simulation results demonstrate effectiveness of the sliding mode control with respect to load and input voltage variation.

Loss analysis of IGBT in three-phase rectifier based on five-segment SVPWM

Three-phase rectifier topology is given first, on this basis, analyzing the differences of seven-segment SVPWM modulation method and five-segment SVPWM modulation method, and show two kinds of duty ratio calculation formula in different sectors. And then consider the influence of DC-bus voltage, temperature and the IGBT junction temperature on the loss of IGBT, giving different calculation methods of conduction loss, switching loss and total loss about IGBT and diode, deriving the calculation formula of the power device junction temperature using thermal resistance equivalent circuit method, and then calculate the loss of the three-phase rectifier through the formulas in different modulation method, the result is the loss of the three-phase rectifier under the five-segment SVPWM modulation method is loss compare to under the seven-segment SVPWM modulation method. Finally experiment and verify on a 60KW DC charging pile experiment platform.

Design of voltage loop for three-phase PWM rectifier based on single neuron adaptive PID control

During the control process of the three-phase PWM rectifier, the parameters of the conventional PID controller are kept constant. Its unable to make appropriate changes according to the actual working condition of the rectifier and the change of working environment, which limits the adaptability of the rectifier to environment and working conditions. Against this point, the single neuron adaptive PID is used as the voltage outer loop controller of the three-phase PWM rectifier instead of the conventional PID. The single neuron could make online adjustment of PID parameters according to the working state of the three-phase PWM rectifier. As a result, it solves the phenomenon that the control performance of the conventional PID controller varies with different working conditions. Through theoretical analysis and simulation verification, the three-phase PWM rectifier controlled by single neuron adaptive PID controller not only own the simple parameter setting process, but strong adaptability, better dynamic and static performance.

Design of power allocation strategy and passivity based controller for multiple module fuel cell hybrid power system

In order to improve reliability and efficiency of single fuel cell hybrid power system, a system composed of multiple fuel cell modules and supercapacitor is proposed, and the power allocation strategy based on passive control is developed according to the efficiency curve of the fuel cell. In this control strategy the multiple working modes are analyzed and the output powers of fuel cell and supercapacitor are allocated. So this hybrid power system can follow the requested load power rapidly and work in high efficiency area as far as possible. The simulation results demonstrate that the fuel cells of the hybrid power system can work in high efficiency area, and the complex and variable load power can be satisfied rapidly.