Practical Application of the Wave-Trap Concept in Battery–Cell Equalizers

Abstract

Abstract.-The use of battery cell equalizers is mandatory in order to assure that all the cells connected in series are charged to its maximum capacity, even when they present small differences in this parameter due to several factors, such as aging, manufacturing or temperature. Active equalizers, with a higher efficiency in comparison to passive ones, have the disadvantage of using a considerable number of components. Moreover, in the case of active equalizers with very high performance, this number can be even higher. In this paper, the use of the wave-trap concept, widely used in telecommunication systems, is studied. This concept allows the battery cell equalizer to use its switching frequency as the control variable that decides which cell is being charged. Hence, it is not necessary to use a complex system based on a high number of controlled switches in order to determine which cell is being charged. In this way, the number of switches (and the corresponding driving signals) can be strongly minimized without reducing the performance of the system. In order to proof the validity of this concept (i.e., wave traps) in the design of battery-cell equalizers, a topology based on a half-bridge structure is also proposed in this paper. It uses only two controlled switches in order to decide which cell is charged. Experimental results are provided for a 4-cell equalizer as a proof of concept.

A Hierarchical Active Balancing Architecture for Lithium-Ion Batteries

“…A modular designed flyback converter is proposed in [23] that can reduce the number of voltage sensors and is suitable for modular design, but the balance can only be achieved in different battery modules instead of each cell. Some advanced control methods such as the time sharing strategy [24] and the wave-trap concept [25] are developed. With these control methods, the required semiconductor devices and magnetic components of the balancing circuit are reduced, which simplifies the structure and lowers the cost.…”

A Cell-to-Cell Equalizer Based on Three-Resonant-State Switched-Capacitor Converters for Series-Connected Battery Strings

“…Transformer-based solutions [22][23][24][25][26][27][28][29][30][31][32] have the inherent advantages of easy isolation, high efficiency, and simple control. However, it is definitely difficult to apply a single multi-winding transformer into a long series-connected battery string because of the mismatching, bulk size, and high complexity implementation of the multi windings.…”

“…Therefore, active balancing methods have higher balancing capacity and efficiency than the passive equalization ones. They can be further divided into three groups, which are capacitor based [10][11][12][13][14][15][16][17][18], inductor based [19][20][21], and transformer based [22][23][24][25][26][27][28][29][30][31][32] methods. Among these active balancing topologies, switched-capacitor (SC) based solutions have the inherent advantages of smaller size, lower cost, simpler control, and higher efficiency.…”

Bidirectional Interleaved PWM Converter with High Voltage-Conversion Ratio and Automatic Current Balancing Capability for Single-Cell Battery Power System in Small Scientific Satellites

“…To ensure years of safe operation of batteries consisting of multiple cells connected in series, a cell equalizer is indispensable to mitigate or even eliminate cell voltage imbalance. Cell equalizers are essentially a switching power converter, such as nonisolated bidirectional converters [2][3][4][5], single-input multi-output converters [6][7][8][9], etc. [10], and these add complexity to spacecraft power systems.…”