固態變壓器平均模型建立與驗證

Abstract

根據格拉斯哥氣候公約，多數成員國承諾要在2050年實現淨零碳排。為了應對此項這個公約，所有部門需要做出相對應的調整——電力部門綠色化，其他部門電力化。新型態的能源應用對傳統電網產生巨大的影響，加上科技的發展，越來越多新型設備投入電網，固態變壓器(Solid State Transformer, SST)正是其中之一。 固態變壓器不僅僅是一個變壓器，它具備多項功能，例如：功率因素校正、電壓控制、虛功控制、諧波抑制以及平衡功率流動等功能。因此，固態變壓器又可以被稱為電網控制器(Grid Controller). 本研究著重在固態變壓器的平均模型的建立與驗證。平均模型將快速的開關動態行為在一個開關週期內進行平均，形成線性模型，這在控制器設計上是一項優勢。多數的控制理論是以線性系統為基礎發展而成，使其能夠引導使用者設計以及優化控制器。相反的，詳細模型屬於非線性模型，因為非線性系統較難分析，所以沒有一套設計準則是根據非線性系統而提出的，這使得設計詳細模型的控制器較為困難。為了驗證平均模型的結果，要先對詳細模型進行設計，當確認詳細模型正確後，將詳細模型進行化簡得到平均模型後，對其進行驗證。本論文簡化模型的準確度高，數值的誤差不超過5%，因此可以表明該簡化模型是正確的。除了確認簡化模型與詳細模型之間的準確度外，本研究也對平均模型進行功能驗證，包含電壓控制以及虛功控制。虛功控制的部分可以完全實現，而電壓控制會稍微偏移標稱電壓。最後，固態變壓器也嘗試與分散式能源(distributed energy resources, DER)連接在直流微電網中，結果也表明了固態變壓器的平均模型可以應用於直流微電網中，且可以經由轉換器提供/接收功率，以供給負載或是儲存電能。

According to the Glasgow Climate Campact, most of members promised that they will achieve net-zero emission in 2050. In order to fulfill the compact, all sectors have to make corresponding adjustment: the power sector should adopt renewable energy resource, while other sectors should advance toward electrification. The applications of new type energy resource have an impact on the traditional power grid. As the development of the technology, more and more new devices integrate into the power grid, where solid state transformer (SST) is one of them. An SST is more than a transformer because it has a lot of functions, such as power factor correction, voltage control, reactive power control, harmonic mitigation, and balanced power flow control among others. Therefore, The SST may be referred to as a grid controller. In this thesis, it focuses on the development and verification of the solid state transformer average model. An average model averages the fast switching dynamics over a switching period, resulting in a linear model, which is considered an advantage in control design. Most control theories are developed based on linear models, and it is able to guide users to design and optimize controllers. In contrast, a detailed model is a nonlinear model and there are no design guidelines for controller design based on nonlinear models. To verify the results of the average model, the design of the detailed model is required. The average model is obtained after validating the detailed model and performing simplification. The accuracy of the average model is high, and the errors are below 5% in each result. Therefore, the average model is valid. Besides verifying the accuracy of the average model, the functions of the average model is been tested, including voltage control and reactive power control. The reactive power control function is fully realized, while the voltage control function slightly deviates from the nominal voltage. Finally, the SST is also interconnected to the DC microgrid along with the solar system and the energy storage system. The result also indicates that the average model of the SST is able to apply in DC micro grids and the SSTs deliver and receive power via the converters to provide loads or store energy.