A Novel Unbalance Compensation Method for Distribution Solid-State Transformer Based on Reduced Order Generalized Integrator

Abstract

Owing to its modular construction, ability for bi-directional power flow and suitability for AC/DC grids, solid-state transformer (SST) is expected to be the backbone of the future smart grids. One of the main drawbacks of SST is the generation of negative-sequence current component at its input stage under unbalanced distribution system which causes adverse impacts on the power quality of the electricity grids. This paper is aimed at proposing a novel unbalance compensation method based on reduced order generalized integrator to suppress the negative-sequence current. Unlike the conventional sequence compensation method that is based on dual synchronous reference frames, the new proposed method does not involve complex calculation of the command current and sequence decomposition. As such, the response speed of the compensation controller is significantly improved. Additionally, the proposed method is easy to implement when compared with the current conventional compensation technique as there is no need to inject sequence components into the grid. A simulation model of three-module cascaded SST with threephase star connection is established in Matlab/Simulink. Several case studies are carried out under different operating conditions. Simulation results validate the feasibility of the proposed method. INDEX TERMS Solid-state transformer, negative-sequence current suppression, reduced order generalized integrator, three-phase unbalance compensation.

Energy Management Strategy of AC/DC Hybrid Microgrid Based on Solid-State Transformer

“…Meanwhile, multiform and high-reliable power grid has become essential to satisfy the demands of power consumers, which is difficult to achieve through traditional distribution networks [5]. In order to tackle the above objectives, the concept of energy router (ER) is proposed in the recent literatures [6], [7], [8].…”

“…A new method to control the power and DC bus voltage is proposed in [5], but the control of AC bus is not considered. A DC bus voltage droop control strategy based on SST and energy storage unit is presented in [8]. Conventional droop control, which mimics the behavior of a synchronous generator in the power systems to modulate active and reactive powers by respectively regulating the frequency and voltage magnitude, is widely utilized to coordinate parallel inverters.…”

State of the Art of Solid-State Transformers: Advanced Topologies, Implementation Issues, Recent Progress and Improvements

“…Solid state transformer (SST) is an emerging technology that could influence the developments in many areas such as smart-grids, traction systems, the system with renewable energy sources (RESs) to mention just a few [1]- [3]. Some advantages of SST when compared with low-frequency transformer (LFT) include reactive power compensation, voltage regulation, power flow control, voltage sag compensation, bi-directional power flow, fault current limiting, harmonic block, and galvanic isolation [4]- [6]. One of the most noticeable advantages of SST is the size and weight reduction.…”

An Overview of the Role of Solid State Transformer in Smart Grid

“…SST has much smarter protection approach, able to effectively isolate load and grid side transients, including load short circuit conditions and unbalanced input voltages, among others, hence increasing the power quality of the system. It guarantees seamless fault ride through operation during both symmetrical and unsymmetrical faults as per the latest grid codes, it provides instantaneous voltage and current regulation because of the solid state devices and switches, active power transfer, reactive power compensation capability, and voltage-conversion functions and a lot more [10][11][12]. It has DC port for easy integration of other renewable energy resources and DC microgrid, it has low electromagnetic compatibility concerns and is equipped with fault current management capability on low-voltage and high voltage side.…”