A simple high-performance current control strategy for V2G three-phase four-leg inverter with LCL filter

Electric vehicles (EVs) can behave as distributed energy storage devices for providing on-demand smart grid support service, that is an emerging Vehicle-to-Grid (V2G) technology. A high-performance and easy-implementation current control strategy for V2G Three-phase four-leg inverter with LCL filter is proposed. It consists of a deadbeat (DB) controller and a paralleled repetitive controller (RC). The DB controller is based on weighted average inductor current (WAIC) scheme, which simplifies the third-order LCL filter to be an equivalent 1st order L filter. The stability of the DB controlled inverter with the unmodelled system time delay is analyzed. DB controller is of very fast response and easy implementation, but is not immune to system time delay and various uncertainties. To overcome the disadvantages, a plug-in RC is added to reinforce the DB controller to remove harmonic distortion from the feed-in current in the presence of parameter uncertainties. A lab prototype of 10kW grid-connected three-phase four-leg inverter has been built up to validate the proposed current control strategy. The simulations and experiments are provided to demonstrate the validity of the proposed control strategy

Double Deadbeat Plus Repetitive Control Scheme for Microgrid System

Parallel connection of converters is a convenient choice when system capacity is to be increased. Parallel-connected voltage source converters, especially neutral point clamped converters, are one of the best choices for its range. However, with the parallel connectivity, the converter possesses a circulating current in its legs, which consequently threatens the safe operation of the system. To alleviate this circulating current problem, in this paper, a double deadbeat (DD) plus repetitive control (RC) scheme is proposed. The RC scheme is employed to mitigate the circulating currents and the DD loop control scheme is employed to achieve a high operating bandwidth for voltage and current characteristics. Furthermore, the DD loop is associated with an adaptive controlling technique, which adjusts internally by itself and provides better performance for nonlinear loads. The proposed DD method forces the equivalent system elements to be placed outside the closed loop, which does not affect the system stability. Initially, the system has been executed with a conventional proportional + integral scheme and then with the proposed DD + RC scheme. The proposed method is verified by implementing a Simulink model in the OPAL-RT platform. Furthermore, the proposed method is built with a prototype, and its results are explored

Control and quality analysis of grid connected inverters output current

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do ParanáWith the expansion of the use of renewable energies to generate electricity, the global energy matrix tends to become more sustainable. The inverter is an essential part of an electricity generation system from renewable sources, it interfaces between the system and the electrical network, supplying power to the grid or feeding the household loads. As a result, the number of inverters connected to the grid has become increasingly larger, with the possibility of injecting current with harmonic components in the system. So that this does not affect the normal operation of the distribution system, some regulations were created defining energy quality parameters to be respected. Therefore, the objective of this dissertation is to study and experimentally validate some techniques for controlling the output current of an inverter and output filter topologies, analyzing the impact of these components on the quality of the injected current. The converter model, as well as the control strategies and the output filters were validated through a simulation in Simulink / MATLAB. For the experimental tests, a power structure of a DC-AC converter previously used in the LSE was used, which consists of a simple topology of a DC-DC converter and a complete bridge inverter. For the control of the platform the dSPACE system was used, which allows a simple programming of the control structure, as well as the acquisition and processing of the test data. The objective of this dissertation was achieved, obtaining results that present the quality of the injected current under different test conditions and system configurations. The resonant proportional control with harmonic compensation showed better results in the nominal power, but the other applied strategies also proved to be valid for some applications.Com a expansão do uso de energias renováveis para a geração de energia elétrica, a matriz energética mundial tende a se tornar mais sustentável. O inversor é uma peça essencial em um sistema de geração elétrica a partir de fontes renováveis pois ele realiza a interface entre o sistema e a rede elétrica, fornecendo potência para a rede ou alimentando as cargas locais. Com isso, o número de inversores conectados à rede tem se tornado cada vez maior, podendo injetar correntes com componentes harmônicas no sistema. Para que isso não afete a operação normal do sistema de distribuição, algumas regulamentações foram criadas definindo parâmetros de qualidade da energia a serem respeitados. Sendo assim, o objetivo dessa dissertação é estudar e validar experimentalmente algumas técnicas de controle da corrente de saída de um inversor e topologias de filtro de saída, analisando o impacto desses componentes na qualidade da corrente injetada. O modelo do conversor, bem como as estratégias de controle e os filtros de saída foram validados através de uma simulação em Simulink/MATLAB. Os testes experimentais realizaram-se em uma estrutura de potência de um conversor DC-AC implementada previamente no Laboratório de Sistemas Eletromecatrônicos (LSE). Para o controle da plataforma foi utilizado o sistema dSPACE, que permite uma programação simples da estrutura de controle, assim como a aquisição e processamento dos dados dos testes. O objetivo desta dissertação foi atingido, obtendo resultados que apresentam a qualidade da corrente injetada sobre diferentes condições de teste e configurações do sistema. O controle proporcional ressonante com compensação harmônica apresentou melhores resultados na potência nominal, mas as demais estratégias aplicadas também se mostraram válidas para algumas aplicações

Double Deadbeat plus Repetitive Control Scheme for Microgrid System

Parallel connection of converters is a convenient choice when system capacity is to be increased. Parallel-connected voltage source converters, especially neutral point clamped converters, are one of the best choices for its range. However, with the parallel connectivity, the converter possesses a circulating current in its legs, which consequently threatens the safe operation of the system. To alleviate this circulating current problem, in this paper, a double deadbeat (DD) plus repetitive control (RC) scheme is proposed. The RC scheme is employed to mitigate the circulating currents and the DD loop control scheme is employed to achieve a high operating bandwidth for voltage and current characteristics. Furthermore, the DD loop is associated with an adaptive controlling technique, which adjusts internally by itself and provides better performance for nonlinear loads. The proposed DD method forces the equivalent system elements to be placed outside the closed loop, which does not affect the system stability. Initially, the system has been executed with a conventional proportional + integral scheme and then with the proposed DD + RC scheme. The proposed method is verified by implementing a Simulink model in the OPAL-RT platform. Furthermore, the proposed method is built with a prototype, and its results are explored

Adaptive Backstepping-based H∞ Robust controller for Photovoltaic Grid-connected Inverter

To improve the robustness and stability of the photovoltaic grid-connected inverter system, a nonlinear backstepping-based H∞ controller is proposed. A generic dynamical model of grid-connected inverters is built with the consideration of uncertain parameters and external disturbances that cannot be accurately measured. According to this, the backstepping H∞ controller is designed by combining techniques of adaptive backstepping control and L2-gain robust control. The Lyapunov function is used to design the backstepping controller, and the dissipative inequality is recursively designed. The storage functions of the DC capacitor voltage and grid current are constructed, respectively, and the nonlinear H∞ controller and the parameter update law are obtained. Experimental results show that the proposed controller has the advantage of strong robustness to parameter variations and external disturbances. The proposed controller can also accurately track the references to meet the requirements of high-performance control of grid-connected inverters