skip to main content


Title: Design and Implementation of a Medium Voltage, High Power, High Frequency Four-Port Transformer
With the growth in penetration number and power level of renewable energy resources, the need for a compact and high efficient solid state transformer becomes more important. The aim of this paper is to design a compact solid state transformer for microgrid application. The proposed transformer has four ports integrated on a single common core. Thus, it can integrate different renewable energy resources and energy storage systems. The transformer is operating at 50kHz switching frequency, and each port can handle 25kW rated power. In this paper, the ports are chosen to represent a realistic industrial microgrid model consisting of grid, energy storage system, photovoltaic system, and load. The grid port is designed to operate at 4160V AC, while the other three ports operate at 400V. Moreover, the grid, energy storage, and photovoltaic ports are active ports with dual active bridge topologies, while the load port is a passive port with full bridge rectifier one. In this paper, an extensive and complete design and modeling of the entire solid state transformer is presented. The proposed design is first validated with simulation results, and then the proposed transformer is implemented. Some preliminary experimental tests are also performed and the obtained results are reported.  more » « less
Award ID(s):
1939124
NSF-PAR ID:
10221387
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
2020 IEEE Applied Power Electronics Conference and Exposition (APEC)
Page Range / eLocation ID:
2352 to 2357
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. null (Ed.)
    In this paper, design of a compact high frequency four-port transformer for a Solid-State Transformer (SST) arrangement is presented. Unlike other SSTs, the four-port system integrates three active sources and a load port with galvanic isolation via a single transformer core. In addition to this feature, one of the three source ports is designed to operate at Medium Voltage (MV) 7.2kV for direct connection to 4.16kV AC grid, while other ports nominal voltages are rated at 400V. The transformer is designed to operate at 50kHz and to supply 25kW/port. Thus, the proposed system connects the MV grid, Energy Storage System (ESS), PV, and DC load to each other on a single common transformer core. Based on the system power demand and availability of renewable energy resources, utility and energy storage ports can either supply or draw power, while PV port can only supply power, maintaining the required demand for the load. This work focuses mainly on the High Frequency Transformer (HFT) design. An extensive study is carried out to obtain the optimal, compact, cost effective, and high efficiency model. Modeling, mathematical, and simulation results are derived and presented to demonstrate the viability of this design. 
    more » « less
  2. Distribution systems need significant voltage support with growing penetration of distributed generations especially intermittent renewable energy resources and smart loads. This paper introduces the application of the Multi-Port Solid State Transformer (MPSST) as an effective tool to support grid voltage at distribution level while integrating distributed energy resources. The solid state transformer replaces the conventional transformer between two voltage zones of distribution systems. Matlab/Simulink environment is used to simulate the IEEE 14 bus test system with an MPSST as a case study. The simulation results prove the effectiveness of the MPSST supporting the distribution system at local level in a fast and efficient manner in response to disturbances caused by load variations. 
    more » « less
  3. Solid State Transformers (SSTs) are being considered as a replacement to the classic transformers especially for renewable energy and energy storage systems mainly due to their much smaller size and controllability and regulation over the transferred power. Multi-Port SSTs share one high frequency core for the isolation between several devices and hence are even more compact and efficient but the system is complex and the control of such a system is a challenge. This paper considers a four-port, MPSST connected to a renewable source, battery, load, and the grid and discusses various scenarios and operating points. It is shown that several factors including the ratio of the renewable power to the load, battery SOC status and role of the battery in the system change the desired power flow in the system and there are several control structure needed for each mode of operation. These modes of operation and the boundary between them are recognized and eventually a MIMO control scheme is suggested that includes several switches to changes the structure of the controller to adjust the controller structure to the operating condition. Eventually, input-output linearization technique has been adopted to the system to linearize the model and achieve a better control performance. 
    more » « less
  4. In this study, a four-port solid-state transformer (SST) with decoupled control scheme to control the power flow and the output voltage is proposed. The proposed decoupled control scheme controls all of the four ports' powers independently. In addition, the design of the four-port transformer including core material selection and winding placement is investigated. The designed transformer is modeled in ANSYS-Maxwell and also co-simulated with ANSYS-Simplorer. The operating frequency of the system is designed for 100 kHz; therefore, a very compact size is obtained for the entire multi-port converter. The performance of the proposed system is validated throughout MATLAB/Simulink simulation and experimental studies carried out for a 10kW/port SST prototype. The obtained results show that the four-port SST provides an interface for four-different power supplies or loads. It is seen that the proposed decoupled control scheme can control the output voltage at the desired value and track the reference power signals for each port. It provides as well a good steady state and dynamic performance. 
    more » « less
  5. A three-port multilevel inverter with two DC ports and an AC port using Flying Capacitor Multilevel (FCML) design based on Gallium Nitride (GaN) switches is proposed in this paper. Recently, FCML inverter has shown a superior ability for power conversion with high power density, improved Total Harmonic Distortion (THD), and efficiency. The presented three-port multilevel inverter fits various applications such as battery and photovoltaic (PV) grid integration and standalone AC load. The proposed inverter is experimentally verified by building a 3-kW prototype using GaN switches which include two 4-level FCML converter paths, each share the same bus capacitor (C bus ), which links them together. One FCML path is 1 kW that incorporates an unfolder for the DC-to-AC conversion and has achieved a peak efficiency of 98.2% with AC voltage and current THDs of 1.26% and 1.23%, respectively. While the second FCML converter path is 2 kW used for the DC-to-DC conversion and has achieved a 99.43% peak efficiency. 
    more » « less