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In this article, the control of hybrid off-grid configuration based on a variable-speed diesel generator and solar photovoltaic array, is implemented. To ensure a stable operation with the ac voltages and system frequency regulation, back-to-back connected converters are controlled using vector-based control, and stator flux-oriented frame-based control. To adjust the speed of diesel engine according to specific fuel consumption, an effective control strategy is developed. In addition, to compensate for the slow dynamics of variable speed operation and to balance the power in the system the dc-link voltage and battery current are controlled using a double-loop control strategy. Furthermore, the dynamic model of the dc–dc boost converter is integrated with the perturbation and observation method for obtaining smooth and efficient maximum power point tracking (MPPT). To prevent overshoots during the sudden transition, all proportional-integral controllers are reinforced with a back-calculation antiwindup scheme. The performance is obtained using MATLAB/Simulink and validated on real-time hardware to demonstrate the effectiveness of coordinated control under variations of loading and weather conditions. [ABSTRACT FROM AUTHOR]

In this article, the design and implementation of a cooperative multitasking control strategy for standalone photovoltaic (SPV) system is presented. A double-loop control strategy based on the fuzzy logic controller is developed to achieve high performance from the SPV without using the maximum power point technique, balance the power in the system, regulate the common dc-link voltage, and maintain system operation stability under disturbance. To ensure uninterruptible power supply to the critical loads during diminution of generated power from the SPV, turned on and off the diesel generator and the dc dump load, power management technique based on load scheduling technique is developed and implemented using the state-flow approach. Furthermore, the stability analysis in open and closed-loop using the average model of the dc–dc buck-boost converter is investigated. The performance of the dc off-grid configuration based on a single dc–dc converter and their control strategies are performed under load and solar irradiation change using MATLAB/Simulink and in real-time through hardware prototyping with DSP controller TMDS28379D. [ABSTRACT FROM AUTHOR]

This article presents control strategies developed with two-level coordinated and double loop control for a standalone microgrid. The interfacing inverter is controlled to perform multifunctions. It incorporates the compensation for power quality problems at the point of common coupling and controls the voltage and frequency deviation to provide a constant voltage and frequency to connected ac loads in standalone and grid-connected operating modes. The power demand during battery charging and discharging is controlled using a buck–boost converter. To control overshoot and settling time while following a dc and sinusoidal references without losing control during the transition, proportional-integral, and proportional-resonant controllers with optimal gain designs are reinforced by antiwindup feedback. To ensure a soft and secure transition, even under disturbances, such as distortions and notches, an enhanced phase-locked loop is used. The performance of this system is simulated in MATLAB and validated on a 2-kW laboratory prototype. [ABSTRACT FROM AUTHOR]

This article deals with the control of a standalone microgrid based on variable speed wind turbine (WT) and fixed speed diesel generator (DG) for water treatment application. A perturb and observe (P&O) method is used to achieve the maximum power point tracking (MPPT) from the WT without using speed sensors. Two levels of control are proposed for the three-phase voltage source inverter for voltage and frequency regulation at the point of common coupling (PCC) and power management in standalone and diesel connected modes. Furthermore, the battery energy storage is controlled using simple approach to balance the power in the system during load variations and wind speed changes. The performance of the proposed system is tested using MATLAB/Simulink under load and weather variations. In addition, the system is tested on a small-scale prototype in the laboratory under load and wind speed variations. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive controller of a standalone microgrid is implemented, which has three dispersed generation units based on a wind, solar photovoltaic (PV) array, and a diesel generator (DG). The power ratio variable step perturb and observe method is applied to achieve maximum power point tracking of a solar PV array and a variable speed wind turbine coupled a permanent magnet brushless dc generator without rotor/wind speed sensors. Moreover, to ensure perfect synchronization of a DG to the point of common coupling (PCC), a control algorithm is developed, which is based on in-phase and quadrature units. An active power control based on proportional–integral controller with anti-windup, is used for voltage and frequency regulation. The LCL filter based on virtual resistor, is used for power quality improvement at PCC. Simulation and test results are presented for the validation of the proposed system using a prototype of 2 kW in the laboratory. [ABSTRACT FROM AUTHOR]

In this paper, the design and implementation of active power control with antiwindup PI controller (AWPI) and improved perturbation and observation (P&O) method with sliding mode control (SMC), are investigated to get a high level of performance with a reduced number of sensors for a stable operation of a wind-PV-battery-based hybrid standalone power generation system (HSPGS). The SMC approach with boundary layer is used for an optimum trajectory on the sliding surfaces, with variable operating conditions of many power converters connected at the same DC bus. Furthermore, detailed modeling and stability analysis to demonstrate the transversality, reachability, and equivalent control are presented. The effectiveness and robustness of HSPGSs and their respective control strategies are validated by simulation and test results on a hardware prototype using a DSP-dSPACE real time controller. [ABSTRACT FROM PUBLISHER]

This paper deals with control of a solar-photovoltaic (PV) power-generating system interfaced with the grid. A sliding mode control approach is used for achieving maximum power tracking control of a solar-PV array. The Lyapunov function-based control approach is designed and modeled for the dc–ac inverter to serve the functions of an active power injection to the grid, balanced grid currents at unity power factor and load currents harmonics compensation. The proposed approaches eliminate the need of adjustment of system parameters under changing loads and generation scenario. The effectiveness of the proposed control strategies is established using its stability analyses. The performance of the solar-PV power-generating system with the proposed control algorithms is demonstrated using simulation and experimental studies under various operating conditions. [ABSTRACT FROM PUBLISHER]

Diesel generators (DGs) are set to work as a backup during power outages or support the load in remote areas not connected to the national grid. These DGs are working at a constant speed to produce reliable AC power, while electrical energy demand fluctuates according to instantaneous needs. High electric loads occur only for a few hours a day in remote areas, resulting in oversizing DGs. During a low load operation, DGs face poor fuel efficiency and condensation of fuel residues on the walls of engine cylinders that increase friction and premature wear. One solution to increase combustion efficiency at low electric loads is to reduce diesel engine (DE) speed to its ideal regime according to the mechanical torque required by the electrical generator. Therefore, Variable Speed Diesel Generators (VSDGs) allow the operation of the diesel engine at an optimal speed according to the electrical load but require additional electrical equipment and control to maintain the power output to electrical standards. Variable speed technology has shown a significant reduction of up to 40% fuel consumption, resulting in low GHG emissions and operating costs compared to a conventional diesel generator. This technology also eliminates engine idle time during a low load regime to have a longer engine lifetime. The main objective of this survey paper is to present the state of the art of the VSDG technologies and compare their performance in terms of fuel savings, increased engine lifetime, and reduced greenhouse gases (GHG) emissions. Various concepts and the latest VSDG technologies have been evaluated in this paper based on their performance appraisal and degree of innovation. [ABSTRACT FROM AUTHOR]

An electric vehicle uses multiple energy-storage systems to power the traction motor. Dual-source inverters (DSIs) are used for single-stage power conversion by skipping the dc/dc boost converter stage; therefore, eliminating the passive magnetic storing element which improves the overall efficiency of the drive; moreover, multiple energy-storage systems improve the power density of the system. This article discusses the fine control of a traction motor from zero speed to rated speed supplied through a dual-source inverter. Field-oriented control with space vector modulation technique is applied to achieve closed-loop control. Two dc sources are used, one having a higher-voltage battery and one a lower-voltage battery. The higher-voltage battery is the main battery which supplies power to the traction motor, whereas the lower-voltage battery supplies power to supplementary loads of the EV. This article presents improved dynamic behaviour of an induction-motor-driven EV fed from a dual-source inverter using modified closed-loop field-oriented control with space vector modulation. The improvement includes reduced control complexity due to space vector modulation and achieving the option of EV operation in an emergent situation using the same converter and control system. The simulated performance of the presented system is obtained in MATLAB/Simulink. A step-down experimental prototype is used for verification of effective control of the induction motor as the EV is under constant torque variable speed operation with real-time parameters such as power, power factor, current harmonics, and voltage/current stresses across the switch using two batteries individually. [ABSTRACT FROM AUTHOR]

In this paper, the predictive-based control with bacterial foraging optimization technique for power management in a standalone microgrid is studied and implemented. The heuristic optimization method based on the social foraging behavior of Escherichia coli bacteria is employed to determine the power references from the non-renewable energy sources and loads of the proposed configuration, which consists of a fixed speed diesel generator and battery storage system (BES). The two-stage configuration is controlled to maintain the DC-link voltage constant, regulate the AC voltage and frequency, and improve the power quality, simultaneously. For these tasks, on the AC side, the obtained power references are used as input signals to the predictive-based control. With the help of the system parameters, the predictive-based control computes all possible states of the system on the next sampling time and compares them with the estimated power references obtained using the bacterial foraging optimization (BFO) technique to get the inverter current reference. For the DC side, the same concept based on the predictive approach is employed to control the DC-DC buck-boost converter by regulating the DC-link voltage using the forward Euler method to generate the discrete-time model to predict in real-time the BES current. The proposed control strategies are evaluated using simulation results obtained with Matlab/Simulink in presence of different types of loads, as well as experimental results obtained with a small-scale microgrid. [ABSTRACT FROM AUTHOR]

Configurations, coordinated controller design and applications of various off-grid systems with distributed energy resources (DERs) for an uninterrupted supply, are presented in this paper. The performances for the optimal operation of a diesel generator (DG) in the presence of nonlinear loads, fuel-savings, voltage and frequency regulation, a soft and secure transition among different operating modes, an optimization, and power management control, are validated through simulated results and test results on the prototype to demonstrate the suitability of these configurations with natural energy resources (NERs) for continuous development in remote as well as in isolated locations. [ABSTRACT FROM AUTHOR]

In this study, improved predictive model control (PMC) strategy with prediction horizon of one sampling time for standalone solar photovoltaic (PV) system is discussed. Two control strategies based on the improved PMC approach are designed and implemented to ensure a fast and accurate stability of the system. Enhanced PMC‐based maximum power point tracking is developed and implemented to extract maximum power and achieve high performance from solar PV under the presence of severe conditions by estimating the equivalent system resistance and output PV voltage. Furthermore, to achieve high performance without saturation issue, adaptive proportional–integral controller with anti‐windup is employed. In addition, modelling as well as the parameters design method are offered. An efficient dc–dc boost converter is employed. To regulate the output ac voltage and frequency, as well as, supply a clean power to the connected load, improved PMC controller is developed and implemented. To predict the attitude of the output ac voltage at each sampling prediction interval for all possible switching states, the cost function is defined and evaluated as a standard to select the position function of the switches. The performances of the proposed system and their enhanced control strategies are verified using MATLAB/Simulink, and validated in real time using laboratory prototype. [ABSTRACT FROM AUTHOR]

Summary: Wind turbine emulators (WTE) have become a necessity for testing, developing, and improving design and control strategies in the renewable energy domain. The aim of this paper is to realize an experimental standalone wind energy conversion system emulator (WECSE) with improved torque and current control strategy using a nonlinear PI controller. The prototype was developed with a separately excited DC motor to simulate the wind turbine by providing the required speed and torque for power generation using a directly driven wound‐rotor synchronous generator and a power conversion system controlled by a modified drift‐free Perturb and Observe (P&O) Maximum Power Point Tracking algorithm (MPPT). The DC motor torque is controlled by an nonlinear PI controller regulator for an estimated current reference through a chopper driven by a dSPACE control board where the MATLAB/Simulink platform is used for wind turbine simulation. The proposed method was validated by experimental tests for different wind speeds and was compared with the conventional method. The experimental results have demonstrated that the control, emulation, and MPPT performances of the proposed method are significantly better. [ABSTRACT FROM AUTHOR]

Summary: This article proposes an adaptive and modified Perturb and Observe (P&O) maximum power point tracking (MPPT) algorithm, using fuzzy logic step size controller, for a wind energy conversion system (WECS) based on wound rotor synchronous generator. The modified P&O controller uses additional current information of the dc‐link, to decrease power oscillation around MPP, and choose the correct direction of the perturbation, while wind speed increase condition, depending on the sign of dc‐link current change. So, in this contribution, a modified drift‐free P&O algorithm was chosen because it gives better results, but the duty cycle step size in the proposed MPPT controller has been varied adaptively, using a fuzzy logic inference system based on the variation of the rectifier output power and the previous change of the duty cycle to get fast convergence until the MPP is reached in increasing and decreasing wind speed conditions. Performances and robustness of the proposed speed sensorless MPPT controller are evaluated in an experiment implementation, using a WECS emulator and dSpace DS1104 controller board, where experimental results show that the proposed method guarantees fast convergence with better energy quality and high robustness against speed or load change conditions. [ABSTRACT FROM AUTHOR]

Variable speed generators can improve overall genset performance by allowing the diesel engine to reduce its speed at lower loads. In this project, a variable speed diesel generator (VSDG) uses a rotating stator driven by a compensator motor. At lower loads, the stator turns in the opposite direction of the rotor, a process that can be used for purposes like maintaining a fixed relative speed between the two components of a generator. This allows the diesel engine to turn at a lower speed (same as the rotor) and to increase its efficiency. The present research addresses the control of the compensator motor driving the generator's stator using a variable-frequency drive that adapts the speed to its optimal value according to the load. The performance of the proposed control strategy was tested using a Freescale microcontroller card programmed in C-code to determine the appropriate voltage for the variable-frequency drive. The control algorithm uses a real-time application implemented on an FDRM-KL25Z signal processor board. The control performance of a 2 kW asynchronous motor (LabVolt EMS 8503-00/208 V/3 ϕ/60(50) Hz) was demonstrated experimentally at different operating conditions. [ABSTRACT FROM AUTHOR]