- 學位論文
光伏電模組串聯負載共振式蓄電池充電器之分析與設計
Analysis and design of battery charger with series-loaded resonant converter for photovoltaic modules
摘要
由於串聯負載共振式直流轉換器更具有電路結構簡單、控制電路設計容易、元件數目少、體積小、重量輕、必v密度高、效率高以及低成本等各項優點。因此，為了實現高性能、低切換損失、高效率與低成本的目的，本論文採用具有柔性切換特性的串聯負載共振式直流轉換器作為光伏電模組蓄電池充電器電路。另外，為了避免因太陽光線變化，造成光電模組輸出電壓變動，進而影響串聯負載共振式轉換器操作點偏移問題，本論文於光伏電模組與串聯負載共振式蓄電池充電器間設計一閉迴路升壓式轉換器，以穩定光伏電模組的輸出電壓。 藉由設計適當的共振槽特性阻抗，可調整蓄電池的充電電流，進而控制蓄電池充電所需的時間。而串聯負載共振式充電器所產生的高頻交流電源，需於輸出端經由整流器轉換為直流，再由低通濾波器消除高頻漣波，然後再供給蓄電池穩定的直流電進行充電。控制電路設計是以脈波寬度調變的方式控制兩個主動開關，經由適當的參數設計使共振式轉換器操作於連續導通模式，並使主動開關能於零電壓與零電流切換導通，減少切換損失以維持電路的高效率。至於電路參數的設計均以共振槽之特性阻抗為基準，調變切換頻率並固定主動開關的責任週期，經由切換頻率的變化而改變電路阻抗，進而控制充電電流大小。 本論文根據開關切換時情況配合輸出濾波器電路結構，建立出整體等效電路的工作模式，並加以分析其操作原理，撰寫電路各特性方程式。本文使用基本波近似法與蓄電池簡化等效電路以簡化電路分析，建立串聯負載共振式充電器之等效電路，並以此等效電路為基礎，推導電路參數設計方式及電路設計流程。然後以電腦模擬與實作電路做理論驗證，實驗結果令人相當滿意。最後，本篇論文為了在短時間內，更有效的儲存太陽能光電模組所產生的電力，減少蓄電池充電時間，提出一改良型的串聯負載共振式蓄電池充電器，此種新型的蓄電池充電器，不僅能大幅地提升充電電流，降低蓄電池充電所需的時間，其充電效率更高達85%以上。
並列摘要
Series-loaded resonant converter features several merits, such as simple circuit configuration, easy control demand, small volume, light weight, high power density, high efficiency and low cost. In order to implement a battery charger for photovoltaic modules with high performance, low switching loss, high efficiency and low cost, this paper proposed a series-loaded resonant converter with soft-switching characteristics. Furthermore, to alleviate the photovoltaic output voltage fluctuation induced by the solar power change, this paper designed a close-loop-controlled boost converter in-between the photovoltaic module and charger. This design can inhibit the operation point shift and stable the output voltage of photovoltaic modules. The charging current and charging time can be regulated by designing suitable characteristic impedance of the resonant tank. The high-frequency current produced by series-loaded resonant converter is rectified and passed through a low pass filter to eliminate the high frequency ripples, and then the steady dc current is fed into the batteries. The active switches are gated by pulse width modulation (PWM). The converter is operated at continuous conduction mode (CCM). The active switches are suitably controlled to operate at zero voltage and zero current switching to reduce the switching loss and improve the circuit efficiency. Circuit operation modes are identified according to the conduction profiles. Operation equations and operation theory are also developed. This paper applies fundamental wave approximation and battery equivalent circuit to simplify the circuit analyses. The circuit is approved by computer simulation and experiments. In order to efficiently store enough power into the photovoltaic modules in short period, this paper proposed a modified series-loaded resonant battery charger. This battery charger can provide high charging current and reduce the charging time. The charging efficiency is as high as 85%.