具電池溫昇抑制之光伏電池快速充電系統設計

Abstract

本論文針對鋰電池因快速充電所導致溫度急速上升之情況進行補償，並且搭配光伏系統完成具即時溫昇抑制之鋰電池快速充電系統。光伏系統最主要之研究為擷取當下太陽能陣列之最大功率給予後端負載使用，亦即最大功率追蹤，有別於傳統最大功率追蹤技術，本論文使用模糊控制完成智慧型太陽能最大功率追蹤控制器，此控制器能夠快速且準確的追蹤到最大功率點。搭配前端太陽能發電，本論文設計了三種直流直流轉換電路以調節系統功率供給後端負載使用，其轉換電路為兩階式昇壓轉換電路、降壓轉換電路以及返馳式轉換電路。首先兩階式昇壓轉換電路是應用於一市售直交流轉換器，第一階昇壓電路搭配所設計之模糊控制器以達到最大功率追蹤；第二階昇壓電路則搭配電壓回授控制將輸出電壓昇壓至直交流轉換器之操作電壓值。完成光伏系統設計後，接著設計一返馳式直流直流轉換電路並且搭配電池內阻特性所設計之電池充電系統，此充電法則有三種模式：微小電流充電、定電流充電、定電壓充電。微小電流充電模式是基於電池內阻特性所設計之充電模式，此模式能有效抑止電池溫度急速上升，而定電壓與定電流充電模式使用所設計之特殊控制法則以完成電池充電。最後結合前面兩項之研究成果設計出一降壓型轉換電路，搭配所設計之充電法則---定電流充電、脈衝充電、微小電流充放電。模糊控制器於定電流充電與脈衝充電模式下完成太陽能最大功率追蹤以提供最大功率時之電流予以充電，於微小電流充放電模式中調整太陽能陣列之輸出電流以達到微小電流之設定。脈衝充電法則是以電池即時溫度回授控制其充電之責任週期進而達到抑制電池溫度急遽上升之效果，而微小電流充電之目的是將電池電量充飽至100%SOC (State of Charge)。本論文所提出之具電池溫昇抑制之快速充電法則搭配所設計之轉換電路能夠有效利用光伏系統達到快速且安全之充電目標。

This thesis presents a battery fast charging mechanism for an intelligent generic photovoltaic (PV) system with temperature rise suppression. The fuzzy logic control (FLC) is adopted for fast and accurate maximum power point tracking (MPPT) of the PV system. This thesis designs three types DC-DC converter to converter the power of front-end solar array to load where the converters are two-stage boost converter, flyback converter and buck converter. The two-stage boost converter is designed to convert the solar energy to an inverter. The first stage is used to achieve the MPPT with the designed FLC controller. The second stage is used to boost the output voltage above the operable voltages of the inverter with the designed voltage boost controller. After completion of the PV system design, a flyback converter with the internal resistance characteristics of battery is designed to charge the battery. The designed charge modes are trickle current, constant current (CC) and constant voltage (CV) charge. The trickle current charge mode could suppress temperature rise effectively because that the internal resistance of battery is big when the battery is at the low electricity condition. The CC and CV modes are achieved by the proposed duty control method and PI control with only output voltage feedback. Continuation of the above results, the PV system is designed to charge the battery with a buck converter. Here are three charge modes to design to fast charging --- constant current (CC), pulse charge and trickle current charge-discharge. By the designed FLC controller, the current at MPP is used to charge the battery in CC and pulse charge mode for the fast charging. The duty cycle of the pulse charge is determined by the temperature of battery for on-line compensation. The trickle current charge-discharge mode is used to achieve fully capacity of battery as much as possible. The PV system is successfully achieves the fast charging and on-line temperature rise suppression by the proposed charging algorithm with a designed intelligent controller.