Weiwei Zheng

Modeling and global maximum power point tracking for photovoltaic system under partial shading conditions using modified particle swarm optimization algorithm

Under partial shading conditions (e.g., due to buildings, trees, and clouds), multiple peaks may exist on the power-voltage (P-V) characteristic curve of photovoltaic (PV) array, leading to the conventional maximum power point tracking methods fail to extract the global maximum power point (GMPP). In this paper, a mathematical model of PV array under partial shading conditions with a voltage calculated principle is established. The presented model is implemented with an m-file in MATLAB software, which is used as a tool to study the non-linear characteristics of current-voltage (I-V) and P-V curves of PV array, as well as quickly develop the GMPP tracking controllers. Besides, an adaptive random particle swarm optimization (ARPSO) algorithm is presented to accurately extract the GMPP under partial shading conditions. Five simulation cases with different partial shading patterns are used to evaluate the performance of the presented approach by comparing with the conventional PSO, perturbation and observation (P&O), incremental conductance (INC), and genetic algorithm (GA) methods. Simulation results show that the ARPSO algorithm can rapidly find the GMPP under different shading conditions compared with the conventional PSO algorithm. Furthermore, the presented algorithm can accurately extract the GMPP when the shading condition sharply changes, while the P&O and INC algorithms fail to track the GMPP, but only detect the rightmost MPP encountered either local or global and regardless of the course. Besides, the ARPSO can rapidly and accurately converge to the GMPP with smaller population size and higher convergence speed compared with the GA.

SOC estimation of LiNi 1/3 Co 1/3 Mn 1/3 O 2 battery using Unscented Kalman Filtering Method

LiNi1/3Co1/3Mn1/3O2, well known as the ternary material, is currently considered as one of the promising cathode materials for lithium-ion battery (LIB). In application, accurate estimation for state of charge (SOC) is crucial for the performance and safety use of LIB. However, it is a hard work as the SOC cannot be directly measured and is affected by many factors, such as ambient temperature, current rate and cycle number. Moreover, the influence of electromagnetic interference on measurement results (current, voltage and temperature etc.) makes the situation more terrible. In this paper, an approach of SOC estimation for LiNi1/3Co1/3Mn1/3O2 battery, which is based on the Unscented Kalman Filtering (UKF) is presented. An improved model for online SOC estimation under abominable operating conditions is presented, in which the battery rated capacity variation with ambient temperature and discharge current rate are taken into consideration. A modified two-order RC equivalent circuit model is employed to simulate the battery characteristics, based on which the state-space equation of battery is established. Experimental results show that the presented model can capture the battery characteristics very well and the UKF-based SOC estimator can ensure the estimation accuracy even if the measurement is incorrect.

Simulation and implementation of State-of-Charge estimation of power lithium-ion battery using energy method

Battery is the major energy storage source of electric vehicles (EVs), which makes the accurate estimation of State-of-Charge (SOC) very crucial. Various SOC estimation methods have been proposed in recent years. Among of them, Ah method is widely used due to its easy implementation. This paper presents an energy method for SOC estimation of power lithium-ion battery, which is based on the law of energy conservation. The mathematical model is firstly built to describe its principle. A MATLAB-Simulink simulation model and a laboratory prototype are established to verify the performance of the energy method. Simulation and experimental results show that this SOC estimation method is more accurate than the Ah method, especially under high current and variable current conditions.

Analysis on Power Battery Performance Test and Consistency in Packing Process

In order to solve the application of the battery consistency group problem, a new type of power Li-ion battery consistency assemblying method is proposed and analysed through testing the DC resistance, capacity, self-discharge of the battery, which ensures not only maximum utilization rate of monomer battery in the samples but also makes certain battery does not occur over charge/discharge and improves battery life and safety.

A New Type Battery Equalization Circuit of Electric Vehicle

A new type of electric vehicle battery equalization circuit is described and analyzed in this paper. The circuit uses a two-way flyback converter and relay group to achieve energy transformation between the batteries and realize energy balance of electric vehicle battery pack, which could prevent battery over charging and over discharging. Compared to conventional equalizer, the equalizer is faster and more effective.

Smart Charge/Discharge Management System of a Portable Computer with Dual Batteries

A double-battery charging/discharging management system, which is applied in the notebook computer, is proposed and analyzed in this paper. The main circuit of the system is based on a charger chip and a micro card is used as an intelligent controller. The system controls the charge and discharge of double battery through software programming. Experiment shows that this system can fast and safe charge.