مبدل AC/DC سه فاز دو جهته
Abstract
1- Introduction
2- System description
3- Principle of DPC
4- Proposed control strategy for LVRT and enhanced reactive power support
5- Simulation and experimental results
6- Case I: simulation and experimental results of AC/DC converter control strategy for three different modes of operation (Inversion, Shut Down and Rectification Modes)
7- Case II: study of the LVRT
8- Conclusion
References
Abstract
This paper describes an advanced control strategy of a bidirectional three-phase PWM AC/DC converter embedded between a micro-grid and utility. This converter proves an ability to control a bidirectional power flow. Firstly, the improved control strategy is based on direct power control using a new switching lookup table obtained from the derivative analysis of the active and reactive power. Furthermore, the improved control strategy is verified by simulation. In addition, many operating modes are established due to verify the capability of a bidirectional power flow of the converter. Particularly, authors focus on three operating scenarios which are cited as follow: Inversion Mode (IM), Shut-Down Mode (S-DM) and Rectification Mode (RM). Moreover, the authors show the capability of the DPC with respect to the LVRT for Tunisian grid. Finally, the performances of this converter are validated experimentally using a Dspace 1104 board, a bidirectional AC/DC converter and the wind turbine using a SM connected with the rectifier. The simulation results compared to the experimental ones demonstrated the good performances of the proposed control strategy.
Introduction
In order to offset the growing demand for electricity in the world, the majority of countries are investing in the development of new renewable sources such as Wind Energy, Fuel Cells and Solar Energy [1–3]. For this purpose, the integration of a bidirectional AC/DC converter is necessary for the interfacing between the renewable energy sources and grid. However, its control strategy has attracted the attention of researchers since it has a THD ratio meeting the standards IEEE Std 519™ ‒ 2014 [4]. Several control approaches of the bidirectional AC/DC converter are cited in the literature [5–7], Voltage Oriented Control (VOC) [8], Virtual-Flux Oriented Control (V-FOC) [9], Voltage-based Direct Power Control (V-DPC) [9], Virtual-Flux-based Direct Power Control (VF-DPC) [10]. In this paper, we introduce an improved DPC approach since it has several advantages [9,11]. First, the PWM voltage modulation block is not separated. In contrast, the active and reactive power control is decoupled and the control is activated without a current regulation loops. In addition, this control technique gives good dynamic performances. Consequently, the improvement of power factor and efficiency is accomplished. Because of its main role in the majority of applications, various studies are being raised around the bidirectional AC/DC converter. Thus, in the literature, three operating scenarios are studied. Firstly, an improved control strategy for bidirectional AC/DC converter is developed in Ref. [1]. Then, Rakesh et al. described the three modes of operation (Inversion Mode, Shut-Down Mode and Rectification Mode). Moreover, they practically justified simulation results on an OPAL-RT test bench. However, this work has been done for a bidirectional single phase AC/DC converter. In addition, in order to reduce switching losses, a new control strategy has been addressed for a bidirectional AC/DC converter in reference [12]. So, Yi L. discussed only two modes of operation (rectifier and inverter). Finally, they have completed this work with an implementation of the control law on a Spartan-3E XC3S250E FPGA board. Furthermore, three operating modes such as Grid-Connected Mode (Inversion Mode and Rectification Mode) and Isolated Mode (Shut-Down Mode) are described in Ref. [13]. Indeed, Xiong et al. intercalated a bidirectional three-phase converter between AC Micro-grid and DC Micro-grid. Moreover, they simulated these three operating scenarios in Matlab/Simulink. Finally, however the interest of this work, the authors not validated experimentally these three operating modes.