獨立型太陽能路燈之高性能充放電控制技術研究

Abstract

本研究旨在探討獨立太陽能LED路燈之充電與放電控制方式，使蓄電池的蓄電量可以提高，且不會產生過充；在夜間放電時，可依蓄電量大小做最佳放電控制，以提高照明續航力。 本研究首先探討蓄電池充電過程的動態系統模型，再利用此一模型進行控制器設計與分析，利用閉迴路敏感度分析找出一最佳控制系統，以消除太陽輻射變化對充電過程的影響。夜間照明時之放電，試圖利用時間序列(Time series)預測隔日全日輻射量，再配合開路電壓法所得之當日電容量，決定放電照明功率。 本研究發現蓄電池充電過程的動態系統模型可用一階線性微擾模型來精確描述在不同操作狀態下的動態變化。本研究採用利用PI控制器進行充電控制，發現在太陽輻射量由344W/m2瞬間變化至862 W/m2時，電池端電壓變化量不超過0.2V，可妥善抑制輻射改變之干擾。在放電控制方面，本研究先利用氣象資料推導太陽輻射量的時間序列模型，並用以預測隔日輻射量，唯預測之輻射量在±2MJ/day m2誤差範圍內之成功率只有約30%。因此改以只利用開路電壓法檢測電容量並應用PWM技術，控制放電照明的功率，發現只要蓄電池初始電量高於80%以上，即可使整個太陽能照明系統即使在連續5日陰雨天，亦能提供夜晚的照明。

A battery charge and discharge control technique for solar lighting system was developed to prevent the battery from being over charged in the daytime and to adjust the discharge power for lighting in order to extend the lighting time at night-time. A linear system dynamics model for battery discharge was first derived in the present study. It is found that a first-order perturbed model can accurately describe the system dynamic behavior of the battery at different operating conditions. A feedback control system utilizing PI control is designed. The closed-loop controller design uses a closed-loop sensitivity function to make a compromise between the disturbance rejection and the system response requirement. The experimental results show that the battery voltage can be controlled within 0.2V for the step change of solar irradiation from 344W/m2 to 862 W/m2. The present study also derives a time-series model for predicting the variation of daily total solar radiation using meteorological data in order to control the discharge power effectively to extend the light hours at night. However, the probability of success in forecasting the daily solar radiation within the range ±2MJ/day m2 is only about 30%. A simple algorithm utilizing the PWM power control technique and open-loop voltage check is thus developed. It is found that the present control system can extend the lighting at night for 5 continuous cloudy and rainy days.