Feng Ziping

A critical review on state of charge of batteries

The accurate and reliable SOC (state of charge) estimation is difficult, although it is a core factor especially for battery energy storage system. Current studies of SOC estimation theories and models are mainly focused on voltage model, current model, resistance model, intelligent algorithm model, and hybrid model. Specific attentions were paid to estimate the model and their impact factors on SOC. Then, a critical review of available literature on major SOC issues was presented. Influencing factors on SOC were studied and analyzed, such as dynamic hysteresis characteristics, temperature, aging, self-discharge, and rate of charge/discharge. The economy and practicability of the SOC estimation are analyzed and compared objectively.

Application of two-stage fuzzy PID control in variable refrigerant volume air conditioning systems

The variable refrigerant volume (VRV) air conditioning systems have been employed in small and medium sized buildings recently for its advantages of comfort, energy conservation and easy maintenance. However, the optimal control of VRV air conditioning systems is very difficult due to cross-coupling system parameters and time-variant operating conditions. In this paper, the indoor temperatures are taken as the controlled variables to regulate the openings of individual electronic expansion valve (EEV) and the suction pressure is taken to modulate the speed of inverter-driven compressor, a robust and self-adaptive two-stage Fuzzy Proportional Integral Derivative (PID) controller is proposed. The controllability is tested in a triple evaporator VRV air conditioning system, experimental results show that the proposed two-stage fuzzy PID controller could achieve desired control accuracy and guarantee good robustness for room temperature control.