應用於太陽能系統之自主串聯型微轉換器

Abstract

本論文提出一個自主串聯型微轉換器(Series-Connected Micro-Converter, SCMC)之太陽能發電系統。這是一種最有希望同時滿足低系統成本與高效率的分散式最大功率追(Distributed Maximum Power Point Tracking, DMPPT)太陽能系統。此系統屬於兩級式電路架構，由一串列的微轉換器和一單相市電併聯換流器所組成。系統前級採用有三種操作模式和平滑轉換的四開關升降壓型轉換器(Four-Switch Buck-Boost Converter, FSBBC)來實現最大功率追蹤的功能。系統後級的單相市電併聯換流器則利用雙極性正弦脈波寬度調變搭配直流鏈電壓控制來達成輸出電流與輸入電壓控制。此外，本論文針對此系統提出一個可行之自主控制策略(Autonomous Control Strategy, AUC Strategy)。結合此控制策略，每一組FSBBC與其所連接之太陽能可以形成一個可獨立操作的自主式太陽能模組(Autonomous PV Module, APVM)。為了有效分析APVM之動態表現與穩定度，本論文接著推導及分析其不包含和包含模組互動的兩種小訊號模型。此外，根據所建立的模型提出了控制器設計準則，並分析了APVM的穩定度。最後，以模擬與實驗結果來驗證本論文所提出的小訊號模型準確度和自主串聯型微轉換器太陽能發電系統的特性與功能。

An autonomous series-connected micro-converter (SCMC) photovoltaic (PV) system is proposed in this dissertation. It is the most promising candidate to achieve both low system cost and high efficiency among the distributed maximum power point tracking (DMPPT) PV systems. The proposed SCMC PV system has a two-stage circuit topology, which is composed of a set of SCMCs and a single-phase grid-tied inverter. The four-switch buck-boost converter (FSBBC) with three operation modes and a smooth transition method is adopted to realize the maximum power point tracking (MPPT) function for each PV panel. The single-phase grid-tied inverter with bipolar sinusoidal pulse width modulation (SPWM) control and the AC line current regulation is utilized to control the inverter output current and string voltage. Besides, the autonomous control (AUC) strategy are well-developed for the success of the non-communicating system operation. By adopting the AUC strategy to a PV module which is composed of a PV panel and an FSBBC, a self-contained autonomous PV module (APVM) can be formed. The small-signal AC models, with and without the module interaction considered, are derived to analyze the dynamic behavior and the stability of the APVM. Moreover, the design of controller based on the developed small-signal AC model and the stability analysis of the APVM are presented. Finally, computer simulations and experimental results are presented to verify the accuracy of the small-signal AC model and the performance of the proposed autonomous SCMC PV system.