Model Of Solid State Transformer Research Articles

RETRACTED ARTICLE: Power sharing scheme in interconnected DC microgrids – A new approach

While the techno-economic feasibility of Solid State Transformer (SST) is constantly under question, some of the leaders in the power sector have recognised the potential of the technology and have started efforts of commercialisation. One of the important advantages of SST is its ability to integrate the low voltage DC grids technology. The key areas of research in this field is to use the accurate model of SST between two dc grids. In this article, an accurate composite model of SST that incorporates high switching frequency is developed. The model is controlled using a conventional voltage control technique and with a proposed power control technique. Thus developed SST is employed in transferring the power between two ring main dc microgrids (composed with distributed energy resources) using dual active bridge configuration. This article provides detailed insight of power-sharing scheme between two interconnected ring dc microgrids while maintaining its individual bus voltages within prescribed limits with supervisory communication control approach. Experiments have been conducted on the proposed method by using proposed control approach, and its results are explored.

Port-Controlled Phasor Hamiltonian Modeling and IDA-PBC Control of Solid-State Transformer

This paper presents an application of interconnection and damping assignment passivity-based control (IDA-PBC) principle to the port-controlled phasor Hamiltonian (PCPH) model of solid-state transformer (SST) (comprising of three stages, namely, ac/dc rectifier, dual active bridge converter, and dc/ac inverter). A PCPH model of SST is established for each individual stages using dynamic phasor concept. In comparison with other PBC approaches, IDA-PBC offers an additional degree of freedom to solve the partial differential equations. According to the target of the controller design at each stage, the desired equilibrium point of the system is obtained. The closed-loop system performance achieves regulation of constant output dc-bus voltage and unity input power factor. Large-signal simulation results for the full system validate the simplifications introduced to obtain the controller and verify the proposed controller. Robustness of the controller is demonstrated with 20% load disturbance and 10% input disturbance. For validation of the proposed approach and its effectiveness, hardware-in-loop simulation is carried out using Opal-RT and dSPACE simulators.

Design and Analysis of PWM Inverter for 100KVA Solid State Transformer in a Distribution System

Conventional Magnetic Transformers are key components in a distribution system as it performs several functions like voltage transformation and isolation. However due to increase in penetration of renewable energies into distribution system, existing conventional transformers are expected to be replaced by a solid-state transformer (SST) which offers several advantages as reported in literature. SST can also be used to connect AC or DC grids because it can be operated at a much higher frequency and voltage which results in reduction in the size of conventional transformers as size of transformer is inversely proportional to frequency. In this paper, design and analysis of a 3-phase PWM Inverter using half - bridge topology for 11kV/381V, 100kVA solid-state transformer (SST) is presented for power distribution system application. The mathematical model of SST is developed using analytical calculations and then implemented in MATLAB simulation program. Finally it is implemented in hardware in a laboratory for a half-bridge topology. The main system has been virtually created in order to actualize the conversion from DC to AC.

EMTP Model of a Bidirectional Cascaded Multilevel Solid State Transformer for Distribution System Studies

Abstract: This paper presents a time-domain model of a MV/LV bidirectional solid state transformer (SST). A multilevel converter configuration of the SST MV side is obtained by cascading a single-phase cell made of the series connection of an H bridge and a dual active bridge (dc-dc converter); the aim is to configure a realistic SST design suitable for MV levels. A three-phase four-wire converter has been used for the LV side, allowing the connection of both load/generation. The SST model, including the corresponding controllers, has been built and encapsulated as a custom-made model in the ATP version of the EMTP for application in distribution system studies. Several case studies have been carried out in order to evaluate the behavior of the proposed SST design under different operating conditions and check its impact on power quality.

A Solid State Transformer model for power flow calculations

This paper presents the implementation of a Solid State Transformer (SST) model in OpenDSS. The goal is to develop a SST model that could be useful for assessing the impact that the replacement of the conventional iron-and-copper transformer with the SST can have on the distribution system performance. Test distribution systems of different characteristics and size have been simulated during different time periods. The simulations have been carried out assuming voltage-dependent loads and considering that power flow through either the HV/MV substation transformer or any of the MV/LV distribution transformers can be bidirectional. Simulation results prove that a positive impact should be expected on voltages at both MV and LV levels, but the efficiency of current SST designs should be improved.

Sliding mode control of solid state transformer using a three-level hysteresis function

The solid state transformer (SST) can be viewed as an energy router in energy internet. This work presents sliding mode control (SMC) to improve dynamic state and steady state performance of a three-stage (rectifier stage, isolated stage and inverter stage) SST for energy internet. SMC with three-level hysteresis sliding functions is presented to control the input current of rectifier stage and output voltage of inverter stage to improve the robustness under external disturbance and parametric uncertainties and reduce the switching frequency. A modified feedback linearization technique using isolated stage simplified model is presented to achieve satisfactory regulation of output voltage of the isolated stage. The system is tested for steady state operation, reactive power control, dynamic load change and voltage sag simulations, respectively. The switching model of SST is implemented in Matlab/ Simulink to verify the SST control algorithms.

Performance Analysis of a Solid State Transformer for Smart Grid

Solid State Transformer (SST) has many attractive characteristics, including power quality improvement and reactive power compensation. The paper investigates the topology and control schemes of SST, and discusses its flexibility and reliability for both grid and customers. A model of SST applied for distribution network is constructed, and simulation shows the SST with appropriate control scheme can provide excellent power supply during both steady-state and dynamic-state with varying load.