전기차 충전상태를 고려한 V2G기반 1차예비력의 제어알고리즘과 운영방안에 관한 연구 = A Study on the Control Algorithm and Operating Method for V2G-based Primary Frequency Response Considering State-of-Charge of EVs

다국어 초록 (Multilingual Abstract)

Vehicle-to-Grid (V2G) primary frequency response has a potential as a new resource in the power system, and it is feasible enough to contribute to the grid stability. However, in order to leverage the electric-vehicle (EV) fleets participating in such V2G services and realize the potential of them, a sophisticated approach is required. This is due to the physical constraints and the requirements in the grid. Moreover, it is essential to consider the needs of EV owners―charging their vehicles.
From this viewpoint, the control algorithm proposed in this thesis aims to restore the SoC of EVs by prioritizing charging and leverage V2G fleets while preserving their SoC and mitigating the battery degradation. Also, this algorithm reflects the limitations of the conventional EV charging infrastructure and requirements for primary frequency response in the electricity market.
In order to achieve the aims, the proposed control algorithm determines control MODEs depending on the SoC of EVs and differentiates the primary frequency control strategies. This enables the fleets to restore and preserve their SoC while contributing to the grid.
In addition, the effect of the proposed V2G model is quantified as the ratio of replaced governor response to V2G response, defined as Replacement Factor (RF). Since it is obtained in the range 0.953–1.523, it can be concluded that the proposed V2G model can effectively replace governor response while prioritizing charging and preserving the SoC of EVs.
Replacement Factor is also linearized with respect to SoC distribution in the fleets, and the Replacement Factor Estimation Function is derived. By utilizing this function, Replacement Factor can be conservatively estimated, and the corresponding amount of governor response can be replaced with V2G response based on the proposed control algorithm. In other words, it is possible to operate V2G fleets as a new resource of primary frequency response that can replace governor response, without deterioration of frequency stability.

목차 (Table of Contents)

• List of Figures ⅲ
• List of Tables ⅴ
• ABSTRACT ⅵ
• 1. Introduction 1
• 1.1 Background 1
• 1.2 Proposed method 8
• 1.3 Structure 10
• 2. Considerations for V2G-based Primary Frequency Response 11
• 2.1 Limitations of the conventional EV charging infrastructure 12
• 2.2 Requirements for primary frequency response in Korean power system 14
• 2.3 Importance of state-of-charge of EVs in V2G service 16
• 3. Proposed Primary Frequency Control Algorithm for V2G Fleets Considering Their State-of-Charge 21
• 3.1 Approaches to V2G primary frequency response considering state-of-charge and constraints 22
• 3.2 Definition of control MODEs considering state-of-charge of EVs 25
• 3.3 Control parameters determined from the analysis of V2G primary frequency response 28
• 3.4 Proposal of control strategies and algorithm for V2G fleets to provide primary frequency response 32
• 4. Operating Method for V2G Fleets Based on the Proposed Control Algorithm 35
• 4.1 Quantification method of the effect of V2G primary frequency response on the power system 36
• 4.2 Linearization method of Replacement Factor with respect to MODE distribution in V2G fleets 40
• 4.3 Operating method for V2G fleets using Replacement Factor Estimation Function 44
• 5. Case Studies 46
• 5.1 SoC restoration of the proposed control algorithm 47
• 5.2 Integration of the proposed V2G model into Korean power system 51
• 5.3 Analysis of the effect of the proposed V2G model in Korean power system 55
• 5.4 Deriving Replacement Factor Estimation Function based on the linearization method 68
• 5.5 Validation of the proposed operating method for V2G fleets in terms of replacing governor response 71
• 6. Conclusion 74
• References 76
• 요약(국문초록) 80