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Renewable energy-based smart grids are famous nowadays due to their high intellectual properties. The world is starting new inventions in renewable energy-based electrical power generation systems to reduce global warming. However, a single renewable energy source cannot maintain a proper energy management system and reliability of power towards loads. Hence, integrating two or more systems is very important and can form a smart grid with an appropriate energy management system. Effective energy management system for a 4-wire 1-MW smart grid system is proposed in this paper. The system is composed of three solar plants and three wind farms with a battery bank. The battery energy management system can operate the complete system as a smart grid with the proper design of the controllers. The maximum power points of PV plants are tracked using a hybrid algorithm that merges the merits of Modified Invasive Weed Optimization and Perturb and Observe (P&O). Thus, the maximum power is obtained under partial shading conditions. The P&O algorithm is also developed to track the maximum power of wind farms. All the loads and generation units are connected in a ring-configuration distribution with a centralized battery energy management system. The loads are selected to be unbalanced, nonlinear and reactive to simulate practical cases. TS-Fuzzy based common inverter controller is implemented to maintain acceptable power quality, which is linked to the battery. The proposed inverter controller can work as a reactive power compensator, active power filter, voltage regulator under unbalanced load, and power balancing device between generation and load. Extensive Hardware-in-Loop (HIL) results are presented to validate the effectiveness of the proposed system.

Normally, the BLDC motor drives a sensitive load which is severely influenced by such disturbances. The main aim of this work is to investigate the performance of BLDC motors when they are tied to weak grids. Thus, this paper presents a study on the performance of the BLDC motor under disturbed utility conditions and implements an efficient solution in order to guarantee a soft operation in the case that a BLDC drives a sensitive load. A buck-boost DC converter is merged with the BLDC drive inverter in order to be able to mitigate voltage dips as well as voltage swells. A short interruption of one or two phases of the grid voltage can also be mitigated. The BLDC motor is controlled via cascade PI-controller layout that has an outer loop for the speed control and inner loop for the DC voltage control. The PI controllers’ gains are optimized by using the ant-colony optimization technique and then implemented in a simulation model using MATLAB/SIMULINK. Six cases of disturbances have been simulated including balanced and unbalanced dips, swells and short interruption of one or two phases of the grid. Simulation results with various disturbances show the ability of the proposed controller to mitigate the grid disturbances with good transient and steady-state responses.

The small-scale power systems favor the installation of self-excited synchronous generators due to their simple construction. Many configurations were reported in the literature but there have been always two issues: voltage regulation (VR) and total harmonic distortion (THD) of the output voltage. This paper presents an experimental investigation to improve the performance of single-phase, self-excited, synchronous generator (SPSESG) in terms of the VR and THD. The applied modification is the implementation of sinusoidally-distributed stator windings which implies a different number of turns in each slot. A typical lab single-phase synchronous machine was rewound with the proper number of turns in each slot and then tested against resistive, resistive-inductive, resistive-capacitive, and dynamic loads (induction motor). The experimental results proved that the modified generator performance has significantly improved in terms of the VR and THD. The worst VR was recorded in the case of dynamic load and it was 6.5 %. While the highest THD was 4.5 %, at no load. These figures are much better than other configurations reported in the literature.

as the power generated by a Photovoltaic (PV) system is affected by the weather conditions, there must be storage units to store and deliver energy as per customer needs. One of the potential solutions to this issue is the integration of the PV generator with electrolytic hydrogen and fuel cell (FC). This paper proposes a hybrid-power system that combines a PV generator, Proton-Exchange-Membrane FC, Electrolyzes (ELZ) and hydrogen tanks to serve as energy storage. Depending on the amount of solar radiation, two approaches of connecting the PV generator and FCs are implemented. In the first approach, the FC acts like a backup for the PV system while with the second approach, a hybrid PV-FC generation system is employed. A model of the (ELZ) is implemented in order to simulate the production and storing of hydrogen. The operation of the fuel cell is simulated and analyzed using Matlab/Simulink where many of the encountered problems were solved. The simulation results of the proposed system prove that it can efficiently solve the intermittent nature of the PV energy systems while preserving the environment.

In order to overcome the intermittence of renewable energy sources, such sources are connected in parallel forming hybrid systems. One of these hybrid systems is presented in this paper aiming to investigate and improve its dynamic performance. The hybrid energy system is composed of photovoltaic (PV) arrays and wind turbine (WT) that drives a doubly-fed induction generator (DFIG). Both the PV and WT are linked together through a DC-capacitor link. In order to improve the dynamic performance, a Particle-Swarm Optimization algorithm is implemented to tune the gains of the applied controllers. The obtained optimum gains are then implemented in a simulation model using the simulink program (MATLAB). Results in the case of optimized gains are compared with initial design results in the relevant literature. Results show that the dynamic performance of the hybrid energy system with PSO is improved in terms of speed and steady-state error.

This paper introduces a new ellipsoidal-based tracker design to control a grid-connected hybrid direct current/alternating current (DC/AC) microgrid (MG). The proposed controller is robust against both parameters and load variations. The studied hybrid MG is modelled as a nonlinear dynamical system. A linearized model around an operating point is developed. The parameter changes are modelled as norm-bounded uncertainties. We apply the new extended version of the attractive (or invariant) ellipsoid for this tracking problem. Convex optimization is used to obtain the region’s minimal size where the tracking error between the state trajectories and the reference states converges. The sufficient conditions for stability are derived and solved based on linear matrix inequalities (LMIs). The proposed controller’s validity is shown via simulating the hybrid MG with various operational scenarios. In each scenario, the performance of the controller is compared with a recently proposed sliding mode controller. The comparison clearly illustrates the superiority of the developed controller in terms of transient and steady-state responses.

In order to optimize the efficiency of solar-power systems, sun tracking techniques are implemented and tested experimentally. Both Microcontrollers (MC) and Programmable Logic Controllers (PLC) have been used for tracking purposes with both open-loop and closed-loop control systems. This research aims at comparing between both technologies from the performance and cost perspectives. For a valid comparison, an experimental setup is built and both MC and PLC were tested under the same operating conditions. The results show that from the performance point of view, they are comparable and the maximum difference was about 1.8% of efficiency improvement. But from the cost point of view, the MC tracker is cheaper than the PLC tracker by 30%, roughly in the Egyptian markets.

The proliferation of the Photovoltaic (PV) applications has made the PV - based houses a viable solution to the energy savings and environmental issues, particularly for sunny countries like Egypt. In order to maximize the efficiency and decrease the cost of PV - based houses, various layouts for the electrical network have been reported in literature. A typical layout of an electrical network of a PV house include the PV system, power converters (AC/DC, DC/DC, DC/AC) and loads that might be AC- or DC-based appliances. PV-based houses are classified into three main categories: 1) standalone(off-grid); 2) directly connected to the grid and 3) grid connected with batteries (backup). This paper aims at comparing between the layouts from the perspectives of cost and efficiency. The comparison is based on a case study for house data that is typical for a moderate-income family in Egypt. Some of the reported layouts are modified to suit the local requirements, update with the technology advances, especially in the field lighting and reduce the cost without degrading the overall performance. Two more layouts are proposed in this work to accommodate all possible scenarios of availability and accessibility of the public national grid. It is found that a proper combination between AC and DC wiring in a PV-based house achieves the compromise between the efficiency and the cost.

Solar power is a promising technology as an alternative for the fossil-fuel energy sources. Thus, many researches are done in order to maximally exploit solar energy. In this context, the paper presents the development process of a sun-tracking system based on a stepper motor and an 16f877a-microcontroller. The use of stepper motors enables accurate tracking of the sun. The system has been experimentally tested at different times and under various irradiance conditions. The experimental results show that the output current has considerably increased within the acceptable range of irradiance and the system efficiency has increased by 23 %.

An experimental investigation has been don on a class of self-excited synchronous generator and the results are presented and analyzed in this paper. The investigation focused on the load characteristics under static and dynamic loads. For each loading case, the output voltage harmonics are recorded and analyzed. It is found that the machine performance is robust under all loading conditions. However, there is a considerable amount of harmonic distortion under some loading conditions and it is mainly due to the ripples of the excitation current. Some recommendations are proposed in order to reduce such distortion.

In order to overcome the intermittence of renewable energy sources, such sources are connected in parallel forming hybrid systems. One of these hybrid systems is presented in this paper aiming to i...

Typically, the photovoltaic (PV)-fed houses are based on AC networks. However, a transition to DC networks is currently running due to the proliferation of DC microgrids and the merits of DC systems. This paper considers three distinct designs: AC-based, DC-based and hybrid (AC and DC)-networks. A comparison between three configurations is done based on essential aspects such as the efficiency and the cost. Basic design features such as circuit breakers and cross section area of cables are included. Although the DC-based network has more merits compared to the AC-based network, problems such the DC circuit breakers and the availability of DC-based appliances still present some challenges. Thus, the study found that a proper combination of AC- and DC-based appliances is currently the best choice for PV-based houses.

Accurate phase information is crucial for most of the modern power-electronics apparatus such as the static series compensator (SSC). A software phase-locked loop (SPLL) has been proposed in literature to obtain phase and frequency information of the grid voltage. Either a lead/lag filter or a proportional-plus-integral (PI) controller is employed to control the performance of the SPLL. In this paper, a criterion to tune the SPLL is discussed and the gains of the PI-controller are determined to obtain the desired performance. The proposed criterion is based on the fact that a phase shift of the grid voltage is sensed as a frequency deviation by the load. If the deviation of the grid frequency is kept within the range /spl plusmn/1 Hz, most of the loads function properly. Hence and by the SSC, the response of the phase angle of the load voltage is designed to follow the grid voltage angle while satisfying the frequency range at all times. Consequently, the gains of the PI-regulator of the SPLL are dependent on the maximum phase shift of the grid voltage. Unbalanced grid voltages are separated into positive- and negative-sequence components and the SPLL is locked to the positive sequence. The response of the SPLL has been evaluated by using PSCAD/EMTDC simulation package.

By proper control algorithms, the energy flow between the static series compensator (SSC) and the distribution system can be fully controlled. This paper proposes and describes two control techniques to exchange electric energy between the energy storage capacitor (ESC) of the SSC and the utility. The first is based on using a shunt diode rectifier, which is placed either on the load side or the grid side (both configurations are studied). The other exploits the voltage source converter of the SSC to charge its the ESC. A design guide for the dc-capacitor is given. The proposed techniques are validated by PSCAD/EMTDC simulation.

In this paper, an extensive study on the operation, control and performance of a hybrid photovoltaic and wind turbine system is presented. The study includes the operation of the hybrid system under different weather conditions which are reflected as a change in the wind speed and irradiance. Various loading conditions are investigated such as a change in active and reactive power demands for static and dynamic loads. The performance of the hybrid system is examined via MATLAB/SIMULINK simulations.

The static series compensator (SSC) has shown a significant capability to mitigate voltage dips, which are the most severe problem to sensitive loads. Also, it has been declared that the function of the SSC can be extended to work as a series active filter. This paper proposes a moving average filter (MAF) to detect the fundamental component of the measured voltages and currents (needed to control the SSC) while using a double vector control algorithm (DVC) to improve the transient performance of the SSC. This is made to accurately control the fundamental voltage component at the load terminals in the case of distorted grid voltage. Furthermore, a selective harmonic compensation strategy is applied to filter out the grid harmonics. The operation of the SSC under distorted utility conditions and voltage dips is discussed. The validity of the proposed controller is verified by experiments, which have been carried out on a 10-kV SSC laboratory setup. Experimental results have shown the ability of the SSC to mitigate voltage dips and harmonics. It is also shown that the proposed controller has improved the transient performance of the SSC even under distorted utility conditions.

Udgivelsesdato: FEB The static series compensator (SSC) has shown a significant capability to mitigate voltage dips, which are the most severe problem to sensitive loads. Also, it has been declared that the function of the SSC can be extended to work as a series active filter. This work proposes a moving-average filter to detect the fundamental component of the measured voltages and currents (needed to control the SSC) while using a double vector control algorithm to improve the transient performance of the SSC. This is made in order to accurately control the fundamental voltage component at the load terminals in the case of distorted grid voltage. Furthermore, a selective harmonic compensation strategy is applied to filter out the grid harmonics. The operation of the SSC under distorted utility conditions and voltage dips is discussed. The validity of the proposed controller is verified by experiments, carried out on a 10-kV SSC laboratory setup. Experimental results have shown the ability of the SSC to mitigate voltage dips and harmonics. It is also shown that the proposed controller has improved the transient performance of the SSC even under distorted utility conditions.

Power quality problems encompass a wide range of disturbances, which cause costly loss of production to critical processes. Voltage dips are the major source of power quality-related problems. The static series compensator (SSC), commercially known as dynamic voltage restorer (DVR), is best suited to protect sensitive loads against such incoming supply disturbances. This paper presents an overview of configuration, design criteria, and rated power estimation of the SSC. The used control techniques are discussed aiming to compromise among them based on their suitability with the SSC requirements.

The static series compensator (SSC) has shown to be an effective power electronics apparatus for mitigation of voltage dips. However, the power system operation is not only affected by voltage dips but also other power system events may cause disturbances. In this paper, the behavior of the SSC is investigated in case of upstream capacitor-bank energizing. Upstream capacitor-bank energizing leads to a transient at the terminals of the SSC followed by a sustained overvoltage. This over-voltage is exploited to charge the energy-storage capacitor of the SSC to the maximum allowable dc voltage. Simulations with PSCAD/EMTDC show that the capacitor-energizing transient does negatively affect the performance of the SSC.

The static series compensator (SSC) is suited to protect sensitive loads against voltage dips. Because most of the power system faults are single- or double-phase, the control algorithms of the SSC should be adapted for unbalanced dips. This paper proposes two control strategies to improve the dynamic performance of the SSC. The first strategy uses a fast technique for separating positive and negative sequence components of the supply voltage, which are then controlled separately. Thus, two controllers are implemented for the two sequences, each based on vector control. The second strategy is based on using only a positive sequence controller and increasing the switching frequency. Consequently, the negative sequence due to the unbalanced dip is transformed into variations in the positive sequence. As the switching frequency increases, the ability of the controller to follow those variations improves. The validity of the proposed strategies is demonstrated through PSCAD/EMTDC simulation and experimental measurements carried out on a 10-kV SSC, when the grid is subjected to unbalanced voltage dips.

Control of most of the industrial loads is mainly based on semiconductor devices, which causes such loads to be more sensitive against power system disturbances. Thus, the power quality problems have gained more interest recently. This paper presents a review of some the disturbances, on the source side that may cause problems on the load side. Focus is given on problems associated with voltage dips as voltage dips have been reported to be the most severe problems to industrial loads. Solutions towards such problems using power electronics equipment are explored.

Swells and overvoltages can cause overheating, tripping or even destruction of industrial equipment such as motor drives and control relays. This paper investigates the possibility of employing the Static Series Compensator (SSC) to mitigate voltage swells/overvoltages. In the case of voltage swells, active power may be drawn from the grid into the energy-storage capacitor (ESC) of the SSC, depending on the load current and the SSC impedance. This active power may overcharge the ESC. Two possibilities to overcome this situation are explored in this paper: 1) if the dc-voltage of the ESC is lower than a predetermined voltage level, the active power is employed to charge the ESC to this voltage level; 2) otherwise, the overvoltage protection of the SSC must operate. This paper also applies an overvoltage protection scheme based on a combination of a dc resistor with a chopper and the valves of the SSC. The design of the dc resistor is discussed. A 10 kV SSC experimental setup is exploited to carry out experiments in the case of balanced and unbalanced voltage swells at the grid side.

Voltage dips due to faults are considered the most critical power quality problem to sensitive industrial loads. The voltage source converter, connected in series with the grid as a static series compensator (SSC), is suited to protect sensitive loads against such disturbances. This paper proposes a fast control algorithm to improve the dynamic performance of the SSC. Because most faults are single- or double-phase, this algorithm uses a fast technique for separating positive and negative sequence components of the supply voltage, which are then controlled separately. Thus, two controllers are implemented for the two sequences, each based on double vector control, i.e. constituted by a voltage-control loop and a current-control loop. The validity of the proposed algorithm is demonstrated through PSCAD/EMTDC simulation, when the grid is subjected to unbalanced three-phase voltage dips.

The energy-storage of the static series compensator (SSC) dictates its capability to mitigate voltage dips. Capacitors are considered the most feasible energy storage for the SSC, particularly in high power applications. However, charging techniques of such energy-storage capacitors (ESC) have not been reported in literature. This paper proposes and describes the self-charging, technique that uses the voltage source converter of the SSC to charge its ESC. The active power, used in charging, is taken at the expense of the load active power. Thus two different cases are considered. One case considers that the phase angle of the load voltage is not allowed to jump during the charging process but the magnitude of the load voltage is reduced to 95-99% of its rated value. The other case assumes that the phase angle of the load voltage is allowed to jump. In this case, the VSC of the SSC extracts active power from the grid and injects reactive power into the grid. In both cases, a proper control algorithm is presented. PSCAD/EMTDC simulation verifies the validity of the proposed technique.

The injecting capability of the static series compensator (SSC) to mitigate voltage dips is limited by its energy storage size. Among the existing energy storage devices, capacitors are considered the most feasible solution for high power applications. This paper proposes and describes two control techniques to charge such capacitors. One technique uses a shunt diode rectifier, which is placed either on the load side or the grid side (both configurations are studied). The other technique exploits the voltage source converter of the SSC with a proper control algorithm. A design guide for the energy storage capacitor is given. The proposed techniques are validated by PSCAD/EMTDC simulation.

The phase advance compensation (PAC) has been proposed in literature in order to minimize the injected active power by the static series compensator (SSC) for mitigation of the voltage dips. However, in some cases, the PAC may fail to minimize the active because of the load power factor. This paper discusses and compares four different compensation strategies in order to ensure the minimization of the active power: 1) voltage difference compensation; 2) in-phase compensation; 3) phase advance compensation; 4) progressive phase advance compensation. The effect of the load power factor is investigated on the compensation techniques. A control algorithm based on a combination of the four strategies is proposed taking into account the minimization of the active power and keeping the injected voltage within the ratings of the SSC. PSCAD/EMTDC simulation results are presented to verify the proposed algorithm.

The voltage source converter, connected in series with the grid, as a static series compensator (SSC) is suited to protect sensitive loads against incoming supply disturbances such as voltage dips. Dynamic performance of the SSC is very important since it is essential to start compensation for voltage sags without a sensible delay. This paper proposes a double-vector control algorithm to be implemented to the SSC to improve its dynamic performance. The proposed algorithm incorporates both current and voltage controllers with an inner current control loop and outer voltage control loop. The validity of the proposed algorithm has been demonstrated through a PSCAD/EMTDC simulation, when the grid is subjected to a symmetrical three-phase voltage dip. Simulation results have proved that the proposed algorithm is able to improve the transient response of the SSC, compared to traditional control concepts, such as concepts related to phasors of the sequence components and RMS calculations.