This study introduces a type of solid-state transformer (SST) for solar power station design and an energy management strategy (EMS) for the SST. The purpose of this study is to design a real efficient EMS for the photovoltaic-assisted charging station in smart grid ancillary services and apply the optimal decision method. Also, the energy bound calculation (EBC) model is proposed to find the upper and lower bounds of flexible sources. Also, taking into account the EBC results and the power order from the aggregator, a charge power allocation algorithm is designed to distribute the power of flexible electric vehicles (EVs). With the help of a case study and laboratory analysis, the proposed EMS strategy is effective in real-time energy management and is suitable for practical applications. The obtained results show the stable performance in the calculation of the energy range and real-time power allocation which improves the efficiency of the photovoltaic-based charging station. Also, the SST improves the operation of charge stations for supplying the sustaining power.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-rpg.2020.0399

Energy management strategy for solid-state transformer-based solar charging station for electric vehicles in smart grids

Increase in global energy demand and constraints from fossil fuels have encouraged a growing share of renewable energy resources in the utility grid. Accordingly, an increased penetration of direct current (DC) power sources and loads (e.g., solar photovoltaics and electric vehicles) as well as the necessity for active power flow control has been witnessed in the power distribution networks. Passive transformers are susceptible to DC offset and possess no controllability when employed in smart grids. Solid state transformers (SSTs) are identified as a potential solution to modernize and harmonize alternating current (AC) and DC electrical networks and as suitable solutions in applications such as traction, electric ships, and aerospace industry. This paper provides a complete overview on SST: concepts, topologies, classification, power converters, material selection, and key aspects for design criteria and control schemes proposed in the literature. It also proposes a simple terminology to identify and homogenize the large number of definitions and structures currently reported in the literature.

Solid state transformers: concepts, classification, and control

A state-of-the-art review on topologies and control techniques of solid-state transformers for electric vehicle extreme fast charging

In this article, an integrated solid-state transformer (I-SST) with high-frequency (HF) isolation for electric vehicle (EV) fast-charging applications is proposed In the approach proposed in this article, a three-phase I-SST is used as HF galvanic isolation for the system with respect to the medium-voltage grid A direct multipulse ac–dc rectifier is shown to eliminate low-order harmonics in the input current over a wide range of output dc voltage variation The proposed approach has the following advantages: no dc link, hence no bulky electrolytic capacitors, galvanic isolation is via a three-phase HF transformer, high-power density, and simple control scheme for regulating output voltage The approach is easily scalable to several hundreds of kilowatts and is ideal for high-power level-3 EV fast-charging stations A simplified output voltage regulation scheme for the proposed topology is discussed Regulating the output voltage enables the circuit to be used as a direct topology for level-3 charge stations with ac bus architecture Experimental results on a scale down laboratory prototype at 208 V, 15 kW are discussed 1

An Integrated Solid-State Transformer With High-Frequency Isolation for EV Fast-Charging Applications

The main objective of this article is to present a comprehensive review of soft open point (SOP), an emerging power electronics technology to maximize future distribution networks’ (DNs) resiliency and flexibility as well as increase hosting capacity for distributed energy resources like photovoltaics and electric vehicles. The SOP is currently an active area of research and ongoing development of new control techniques for SOP and optimization algorithm for the optimal use of SOP in DNs produces new techniques until DN operators use it comprehensively in their systems. The motivation for this work is to present the research that has been completed for the SOP and summarize the duties of SOP in DNs according to the literature and propose advanced duties for SOP according to modern standards. Finally, future research directions are mentioned to pave the way for research in the coming years to drive the DNs towards more flexibility and ‘Robust’ from controllability, stability, and protection structure point of view.

/pdf/soft-open-point-in-distribution-networks-5cck2t1jrn.pdf

Soft Open Point in Distribution Networks

Solid-state transformer (SST) is an emerging technology integrating with a transformer power electronics converters and control circuitry. This paper comprehensively reviews the SST topologies suitable for different voltage levels and with varied stages, their control operation, and different trends in applications. The paper discusses various SST configurations with their design and characteristics to convert the input to output under unipolar and bipolar operation. A comparison between the topologies, control operation and applications are included. Different control models and schemes are explained. Potential benefits of SST in many applications in terms of controllability and the synergy of AC and DC systems are highlighted to appreciate the importance of SST technologies. This review highlights many factors including existing issues and challenges and provides recommendations for the improvement of future SST configuration and development.

/pdf/state-of-the-art-of-solid-state-transformers-advanced-4j8kucud9h.pdf

Zhen Hang Choi

Papers

State of the art of solid-state transformers: Advanced topologies, implementation issues, recent progress and improvements