Saber Krim

Design and Implementation of Direct Torque Control Based on an Intelligent Technique of Induction Motor on FPGA

In this paper the hardware implementation of the direct torque control based on the fuzzy logic technique of induction motor on the Field-Programmable Gate Array (FPGA) is presented. Due to its complexity, the fuzzy logic technique implemented on a digital system like the DSP (Digital Signal Processor) and microcontroller is characterized by a calculating delay. This delay is due to the processing speed which depends on the system complexity. The limitation of these solutions is inevitable. To solve this problem, an alternative digital solution is used, based on the FPGA, which is characterized by a fast processing speed, to take the advantage of the performances of the fuzzy logic technique in spite of its complex computation. The Conventional Direct Torque Control (CDTC) of the induction machine faces problems, like the high stator flux, electromagnetic torque ripples, and stator current distortions. To overcome the CDTC problems many methods are used such as the space vector modulation which is sensitive to the parameters variations of the machine, the increase in the switches inverter number which increases the cost of the inverter, and the artificial intelligence. In this paper an intelligent technique based on the fuzzy logic is used because it is allows controlling the systems without knowing the mathematical model. Also, we use a new method based on the Xilinx system generator for the hardware implementation of Direct Torque Fuzzy Control (DTFC) on the FPGA. The simulation results of the DTFC are compared to those of the CDTC. The comparison results illustrate the reduction in the torque and stator flux ripples of the DTFC and show the Xilinx Virtex V FPGA performances in terms of execution time.

Implementation on the FPGA of DTC-SVM Based Proportional Integral and Sliding Mode Controllers of an Induction Motor: A Comparative Study

The conventional direct torque control (DTC), based on the hysteresis controllers and the switching table, operates with a variable switching frequency, which decreases the conventional DTC performances, like the torque and flux ripples. Thus, the space vector modulation (SVM), used in the DTC, ensures a constant switching frequency and improves the DTC performances. The first aim of this paper is to present a comparison study between the DTC with an SVM (DTC-SVM) based on the Proportional Integral regulators (DTC-SVM-PI) and the DTC-SVM based on the sliding mode controllers (DTC-SVM-SMC). These two approaches are complex control algorithms which require faster micro-controllers; therefore the second objective of this paper is to present the implementation of the DTC-SVM-PI and the DTC-SVM-SMC on the Field Programmable Gate Array (FPGA), due to the parallel processing capability of the FPGAs. The two approaches are designed and simulated using the Xilinx System Generator (XSG) and implemented using an FPGA Virtex 5. The simulation results in the transient behavior and the steady state of the induction motor controlled by these two approaches are compared and discussed. The hardware FPGA implementation results show the effectiveness of the FPGA relative to the digital signal processor in terms of execution time.

Classical vector, first-order sliding-mode and high-order sliding-mode control for a grid-connected variable-speed wind energy conversion system: A comparative study

This article proposes a comparative study between different control strategies of a wind energy conversion system. It aims to guarantee a robust control strategy which gives a good performance despite the external disturbances. Studied system comprises a wind turbine, a permanent magnet synchronous generator, and two converters linked by a DC bus. The whole is connected to the grid through a resistor–inductor filter. A classical vector control based on proportional–integral controller is applied to our system. Owing to the sensitivity of this control against external disturbances, a control strategy using first-order sliding mode has been proposed. This strategy provides good performance, such as insensitivity to non-linearity of system. Yet, the theory of first sliding mode has faced the problem of chattering, which proved to be a major drawback. To overcome this problem, a control strategy using sliding mode of higher order was implemented on the basis of the super-twisting algorithm.

FPGA implementation of the direct torque control with constant switching frequency of induction motor

The aim of this paper is to present a digital implementation of the direct torque control (DTC) of an induction motor with a constant switching frequency using the field programmable gate array (FPGA) component. The FPGA is used in order to overcome the digital Signal Processing And Control Engineering (dSPACE) limitations such as the sequential processing which increase the sampling time. The Conventional Direct Torque Control (CDTC) presents some disadvantages, such as the torque and stator flux ripples, and stator current distortions due to the variable commutation frequency of the inverter. To overcome the conventional DTC limitations the switching frequency is imposed by using space vector modulation (SVM). The hardware implementation is proposed to take advantages of the FPGA in digital control field of electrical machines in real time, such as the reduction of the execution time by adopting a parallel processing, the possibility of implementing more complex and more efficient algorithms by exploiting the parallel computing. The performances of the direct torque control with space vector modulation are evaluated by digital simulation using the toolbox Xilinx System Generator (XSG) and implementation results on the FPGA. It has been found that the proposed control yields high performances in term of ripples and execution time.

Power management and second-order sliding mode control for standalone hybrid wind energy with battery energy storage system

The purpose of this article is to provide a high performance control of a renewable distributed generator to guarantee an electric power quality and jointly reduce the mechanical stress despite any possible uncertainties such as the random nature of wind speed, the presence of parameters uncertainties, and external perturbations acting on the system (sudden load variation). The renewable distributed generator integrating a wind generator associated with a batteries module is considered as an energy storage device and a variable load. The proposed method is designed by a power management supervisor and a sliding mode control technique. First, the power management supervisor is used to monitor the power flows transferred between the different system devices depending on the load variation and on the intermittency of wind production. In fact, it enables to ensure the balance at the continuous, Direct Current (DC) bus between the powers supplied by the renewable distributed generator and those demanded by the load. In addition, it prevents batteries from exceeding its maximum or minimum state of charge (SOCbat) by keeping it at an acceptable level [30%, 90%]. Second, a second-order sliding mode control based on the super-twisting algorithm is suggested to control the two subsystems (generator side and load side converters). The main target of the first one is to extract the maximum wind power taking into account the parameter variations and the fluctuating nature of wind. The second one is to investigate a second-order sliding mode control of active and reactive load power quantities, which provides better results in terms of attenuation of the harmonics present in the load voltage and current while considering the sudden load variations. In addition, a proportional–integral controller is also designed and simulated to establish a comparison framework. According to the simulation results, the second-order sliding mode control successfully deals with the nonlinearity of the renewable distributed generator compared with the proportional–integral performance.

Implementation of Direct Torque Control of an Induction Motor with high gain observer on FPGA

The Conventional Direct Torque Control (CDTC) of Induction Motor (IM) with an open loop estimator of stator flux suffers from problem like the correction of measurement errors of the stator current and estimation errors of stator flux and the problem of integration particularly at low speeds. To solve these problems, we use the high gain observer (HGO). This observer is used to estimate the stator flux, the stator currents, the load torque and the mechanical speed. In this paper, we investigate the hardware implementation method of Direct Torque control with High Gain Observer on FPGA using a Xilinx System Generator tool that generates synthesizable VHDL (VHSIC Hardware Description Language) code. The advantages of this method are the rapid time to market, real time and portability. The model of the CDTC with HGO has been designed and simulated using Xilinx System Generator blocks, synthesized with Xilinx ISE 12.4 tool and implemented on Xilinx Virtex-V FPGA.

Modeling and Hardware Implementation on the FPGA of a Variable Structure Control Associated with a DTC-SVM of an Induction Motor

Abstract The conventional Direct Torque Control (DTC) is considered as a powerful approach which is widely used to control induction motors. However, this control approach suffers from several problems like undesirable torque and flux ripples and stator resistance variations, especially at low speed. To overcome these problems, a Variable Structure Control associated with a DTC based on Space Vector Modulation (VSC-DTC-SVM) is proposed in this paper to reduce ripples and enhance the system robustness. Due to the complex scheme of the suggested VSC-DTC-SVM approach, its implementation on software solutions such as microcontrollers and digital signal processors requires a high sampling period. In fact, this period creates delay in applying the inverter switching states which results undesirable ripples and distortions in the torque and the stator current, respectively. This delay is inevitable, and thus the VSC-DTC-SVM performances are affected and the sampling frequency is limited. These limitations in digital control are mainly caused by the calculation speed which depends on the complexity of the algorithm and the serial processing of the software solutions. To cope with this problem, a programmable digital circuit such as the FPGA is chosen to preserve the performances of the VSC-DTC-SVM in spite of its complexity, thanks to its parallel processing. To illustrate this, a hardware implementation of the VSC-DTC-SVM of an induction motor on the FPGA is presented and analyzed. The VSC-DTC-SVM performances in terms of ripples, under stator resistance variation, are presented by a theoretical study, a digital simulation and a hardware co-simulation using an FPGA Virtex 5.

Non-linear control of a wind energy conversion system based on a permanent magnet synchronous generator

This paper discusses a robust control of a wind energy conversion chain based on a Permanent Magnet Synchronous Generator. This command is evaluated in the context of controlling the speed of PMSG and to control the active and reactive power injected into the grid, to increase the power generated and thus improve the efficiency of wind power system. A non-linear controller was implanted. The control of wind systems mainly uses the Proportional Integral controller. However, this type of regulators does not give good control performance because of the disturbance and nonlinearity of the wind systems. Therefore, a nonlinear robust control strategy based on Second-Order Sliding Mode is implanted. In order to validate the proposed control strategy, a system dynamics model proposed was modeled and simulated in MATLAB / Simulink environment.

Nonlinear control strategy of a wind farm for participation in the system services without adding any storage organs

In this paper, we are interested in a nonlinear control of a wind farm connected to the electrical network based on permanent magnet synchronous generator. This control has two main objectives. Firstly, since the major problem of wind energy is the fluctuation of its primary source, to solve this problem, we develop in this study a control approach applied to this wind farm to ensure balance between production and consumption without adding storage organs despite intermittent form of the wind speed. Secondly, a comparative study between a classical PI controller and a non-linear regulator sliding mode are used to control our farm has been proposed. Due to external and internal perturbations of wind systems and the high range of wind speed variation, a PI controller has limited performances. It is sensitive against uncertainties and fluctuations. The simulation results validate the control strategy developed and show superior behaviour of the sliding mode than the PI controller.

FPGA-based DTC-SVM: A comparative study between two approaches

In the conventional Direct Torque Control (DTC) the stator flux and the electromagnetic torque have high ripples due to the switching frequency variations. To fix it, the Space Vector Modulation (SVM) is used in this paper. This paper aims firstly to develop a novel DTC-SVM structure based Sliding Mode (SM) controllers to overcome the DTC-SVM based PI controllers limitations, such as the sensitivity to the external disturbances and the parameter variations. Secondly, this paper deals to reduce the sampling period of the system utilizing the Field Programmable Array (FPGA). The conventional DTC, DTC-SVM with PI controllers and the DTC-SVM with SM controllers are developed, designed from Xilinx system generator tool, implemented on the FPGA-Virtex-5 ML507, and then compared in terms of ripples and the stator resistance variation. It has been noticed that the DTC-SVM with SM controllers provides a torque and flux with very low ripples and it is robust under stator resistance variations.