Abstract
In recent years, electronic power transformer (EPT), which is also called solid state transformer, has attracted great interest and has been used in place of the conventional power transformers. These transformers have many important functions as high unity power factor, low harmonic distortion, constant DC bus voltage, regulated output voltage and compensation capability. In this study, proposed EPT structure contains a three-phase pulse width modulation rectifier that converts 800 Vrms AC to 2000 V DC bus at input stage, a dual active bridge converter that provides 400 V DC bus with 5:1 high frequency transformer at isolation stage and a three-phase two level inverter that is used to obtain AC output at output stage. In order to enhance dynamic performance of EPT structure, neuro fuzzy controllers which have durable and nonlinear nature are used in input and isolation stages instead of PI controllers. The main aim of EPT structure with the proposed controller is to improve the stability of power system and to provide faster response against disturbances. Moreover, a number of simulation results are carried out to verify EPT structure designed in MATLAB/Simulink environment and to analyze compensation ability for voltage harmonics, voltage flicker and voltage sag/swell conditions.
Highlights
Generation, transmission and distribution of electrical energy are the most important factors in modern energy systems and transformers provide the most important role in these systems
K is transformation ratio of high frequency (HF) transformer. m1 and Θ1 are amplitude modulation index and modulation angle for Pulse width modulation (PWM) rectifier used in the input stage. m2 and Θ2 are amplitude modulation index and modulation angle for PWM inverter used in the output stage. usa, usb and usc are input voltages. uLa, uLb and uLc are output voltages
electronic power transformer (EPT) structure in this study is composed of input, isolation and output stages
Summary
Generation, transmission and distribution of electrical energy are the most important factors in modern energy systems and transformers provide the most important role in these systems. Transformers which carry out many fundamental tasks such as galvanic isolation, voltage transformation, noise decoupling are widely used in electric power systems It is well-known that classic (50/60 Hz) transformers have many positive features such as high efficiency, low cost and high reliability (Ronan et al 2002; Yang et al 2015; Zhao et al 2013; Wang et al 2007; Hwang et al 2013). EPT structure with DC-link consisting input, isolation and output stages has several key features such as reactive power and voltage sag/swell compensations (Yang et al 2015; Lai et al 2005). Mathematical model of EPT block diagram of proposed EPT structure is consisted of input, isolation and output stages and has AC/DC/AC/DC/AC conversions as seen Fig. 1.
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