This chapter focuses on the solar battery equalization management technology in distributed power supply systems. The performance and cycle life of solar battery packs are significantly influenced by the inconsistency of individual cells during charging and discharging. Therefore, effective equalization charging control is crucial to extend the solar battery life and improve the performance of the entire system.
1. Introduction
The development of renewable energy requires the use of large-capacity solar battery packs for energy storage. However, the inconsistency of individual cells in the solar battery pack can lead to rapid decay and early failure of the solar battery pack. Therefore, it is necessary to study effective equalization charging control strategies to address this issue.
2. Solar Battery Equalization Management System Structure
The solar battery management system consists of a charging manager, an equalization management unit, and a solar battery pack. The equalization management unit monitors the voltage, current, and temperature of each cell in the solar battery pack and adjusts the charging current of each cell to achieve equalization charging.
3. Impact of Series Charging and Discharging on Solar Battery Packs
During the charging process, the inconsistency of individual cells can lead to an increase in the voltage difference between cells, resulting in overcharging of some cells and undercharging of others. This can accelerate the deterioration of the solar battery pack and reduce its cycle life. During the discharging process, the capacity of the cell with the lowest capacity determines the discharge capacity of the entire solar battery pack.
4. Comparison and Analysis of Equalization Control Circuit Structures
There are currently seven main types of equalization control circuits, including the switched-resistor type, the switched-capacitor type, the fly-back converter type, the bidirectional converter type, the single-input multi-output flyback converter type, the bidirectional single-input multi-output flyback converter type, and the independent equalizer series type. Each type has its own advantages and disadvantages.
5. Structure of the Equalization Charging Control System
The equalization charging control system consists of a charger, an equalization circuit, and a solar battery pack. The charger provides a given charging current, and the equalization circuit adjusts the charging current of each cell to achieve equalization charging.
6. Switched-Resistor Type Equalization Circuit
6.1 Solar Battery Charging Current Control
The charging current of the individual cell is controlled by adjusting the duty cycle of the switching signal of the parallel branch composed of the equalization switch and the equalization resistor.
6.2 Circuit Model Analysis
The equivalent model of the individual cell is established, and the relationship between the cell voltage, charging current, and equalization current is analyzed.
6.3 Charging Control Strategy
The charging control strategy is based on the 马斯（Mas）charging curve, which adjusts the charging current according to the solar battery voltage to achieve fast and efficient charging.
6.4 Equalization Control Strategy
The equalization control strategy is based on the voltage difference and threshold values of the individual cells. The duty cycle of the equalization switch is adjusted to control the equalization current.
6.5 Experimental Results
Experiments show that the equalization charging control can effectively reduce the voltage difference between cells and improve the charging efficiency and cycle life of the solar battery pack.
7. Fly-Back Converter Type Equalization Circuit
7.1 Equalization Current Control
The equalization current is controlled by adjusting the duty cycle of the switching signal of the fly-back converter.
7.2 Solar Battery Charging Current Control
The charging current of the individual cell is the sum of the charging current from the charger and the equalization current from the fly-back converter.
7.3 Circuit Model Analysis
The equivalent model of the individual cell is established, and the relationship between the cell voltage, charging current, and equalization current is analyzed.
7.4 Equalization Charging Control Strategy
The equalization charging control strategy is based on the voltage and current of the individual cells. The duty cycle of the fly-back converter is adjusted to control the equalization current.
7.5 Simulation Analysis
Simulations show that the fly-back converter type equalization circuit can effectively equalize the voltage of individual cells and improve the performance of the solar battery pack.
In summary, this chapter analyzes the impact of series charging and discharging on solar battery packs and compares the advantages and disadvantages of different equalization control circuits. The switched-resistor type and fly-back converter type equalization circuits are studied in detail, and the corresponding equalization charging control strategies are proposed and verified through experiments and simulations. These results provide important references for improving the performance and life of solar battery packs in distributed power supply systems.
The following is a summary of the equalization control circuits in tabular form:
| Circuit Type | Advantages | Disadvantages |
|---|---|---|
| Switched-Resistor Type | Simple structure, easy implementation, low cost | Energy loss during equalization, suitable for solar battery packs with small capacity |
| Switched-Capacitor Type | No energy loss during equalization | Circuit complexity, large impact current, limited application |
| Fly-Back Converter Type | Can be used for both charging and discharging equalization, high efficiency | Circuit complexity, high cost |
| Bidirectional Converter Type | Can achieve independent parallel charging and discharging of each cell, high equalization accuracy | Circuit complexity, high cost, difficult control |
| Single-Input Multi-Output Flyback Converter Type | Reduces the number of components, lowers cost | Difficult to achieve precise equalization, limited application |
| Bidirectional Single-Input Multi-Output Flyback Converter Type | More flexible control, can achieve bidirectional energy transfer | Circuit complexity, high cost |
| Independent Equalizer Series Type | Can achieve precise equalization, suitable for solar battery packs with large number of cells | Circuit complexity, high cost, low system efficiency |