This paper presents a Load Frequency Control (LFC) design using a new optimal PID controller-based Moth Swarm Algorithm (MSA) in Egyptian power system (EPS) in the presence of wind farms. To improve ...the frequency stability of the EPS, the control action needs to be more robust and efficient. Hence, this study presents a coordination between the secondary control (i.e., LFC), and controlled Superconducting Magnetic Energy Storage (SMES) using the optimal PID controller-based MSA for frequency stability enhancement of the EPS. Moreover, the performance of the proposed coordination is compared with both; the optimal LFC with/without the uncontrollable SMES under different load profiles, wind power fluctuations, and system uncertainty. To prove the effectiveness of the proposed coordination, the EPS with inherent nonlinearity was tested using Matlab/SIMULINK® software. The results confirmed that the robustness of the proposed coordination in terms of reducing transient time, minimizing the frequency deviations, and preventing conventional generators from exceeding their power ratings during load disturbances.
Ahstract- The frequency stability is a basic principle in the power system operation. Various reasons such as, load shedding, load restoring, and short circuits cause large frequency fluctuations ...which threaten the system security and could lead to complete blackouts as well as damages to the system equipment. Hence, this paper proposes a coordination of Load Frequency Control (LFC), which uses an optimized PID controller-based Moth Swarm algorithm (MSA) and digital under/over frequency relay for a realistic multi-source power system protection considering different cases study of load shedding and restoring. The discrete-time data of system frequency which obtained from data conversion system is applied for energizing the digital frequency relay under the normal and faulted conditions. The presented digital frequency relay will include both over and under frequency functions. To prove the efficient effect of the proposed coordination, the Egyptian Power System (EPS), which contains three dynamics subsystems, hydro, reheat, and non-reheat power plants was investigated for the MATLAB/SIMULINK simulation considering the effect of system nonlinearity. The obtained simulation results stated the effectiveness of the proposed coordination to maintain the power system frequency stability and security. Furthermore, the superiority of the under/over digital frequency relay in terms of accuracy and speed has been approved.
In this paper, a developed technique of Model Predictive Control (MPC) is proposed to decrease the execution time of the control algorithm for Modular Multilevel Converter (MMC) based on grouping the ...switching states. There are two stages in the control strategy to get the optimal switching state for the converter in the next sampling interval. Within the first stage, the allowable switching states of MMC are divided equally into (M) groups based on the number of sub-modules (SMs) per arm of a single-phase line. Therefore, the output of second-stage obtains the optimal state from each group of the switching states. In addition, all M groups are running simultaneously to reduce the execution time. Unlike the previous algorithm, the second stage of the proposed algorithm uses directly the optimal state and the corresponding cost function for each group from the first stage, then the optimal switching state is selected according to the minimum cost function from the M groups. Therefore, a reduction in the computational time of the MMC algorithm is achieved. The control objectives here are the injected grid currents, balancing the capacitor voltages of SMs at their setpoint, and minimizing the circulating currents in the MMC. The effectiveness of the proposed algorithm is verified by using the nonlinear simulation of MATLAB/SIMULINK
This paper presents a discrete-time model of an optimal controller based on Particle Swarm Optimization (PSO) algorithm for Egyptian Power System-Load Frequency Control (EPS-LFC) with inherent ...nonlinearities. The realistic power system in Egypt is modeled as three dynamics subsystems which are non-reheat, reheat, and hydro power plants. Moreover, the effects of the physical constraints such as Generation Rate Constraints (GRC) and speed governor dead band are taking into consideration. Subsequently, an optimal controller is discretized to obtain optimal digital controller via bilinear transform method of mapping discretization technique for regulating the system frequency. The performance of the presented discrete-time model of EPS-LFC is compared with an analog model for different cases of disturbance and system parametric uncertainties. The results by nonlinear simulation Matlab/Simulink for the EPS-LFC approves that the digital model ensures frequency regulation performance and almost have the same performance as the analog one for different uses sampling intervals. However, the digital model produces a little larger amount of overshoot than analog model in case of large sampling time which satisfy the cost of hardware requirement.
This paper proposes a new topology for a single-phase grid-tie two-stage DC-AC boost inverter for the application of PV systems that utilize high-frequency transformer (HFT) for galvanic isolation. ...In the first stage, a new single-stage high-frequency boost inverter (HFBI) is proposed to boost and convert the DC output voltage of the PV modules to a high-frequency single-phase square waveform and to realize maximum power point tracking (MPPT). The second stage is rectifier-inverter system (RIS) that interfaces HFBI to the grid. Therefore, a single-phase high-frequency transformer is used to link both stages and to provide galvanic isolation between the AC and DC sides. The proposed topology has many advantages such as increasing the inverter output voltage level, MPPT, high reliability, small size and lightweight. In addition, a proportional integral current control (PI) conventional is used to inject a sinusoidal current into the grid at unity power factor. The proposed topology has been verified analytically by using PSIM software and experimentally by using a laboratory prototype.
This paper proposes a new topology for a three-phase PV grid-tie converter. The Whole system consists of two-stage, high-frequency boost inverter cascaded by rectifier-inverter system. A single-phase ...high-frequency transformer is used to link both stages and provide galvanic isolation between the AC and DC sides. In the first stage, a new single-stage high-frequency boost inverter is proposed to boost and convert the DC output voltage of the PV array to a high-frequency single-phase square waveform and to realize maximum power point tracking (MPPT). The second stage is rectifier-inverter system that interfaces the first stage to three-phase grid connected. The 5kW three phase grid connected proposed system has many features such as rising the inverter output voltage level, MPPT, galvanic isolation, small size, high reliability, and light weight. In addition, a grid side controller is used to inject a sinusoidal current into the grid at unity power factor. The proposed topology has been verified analytically by using PSIM software.
Upgrading power system in Egypt towards smart grid Magdy, G.; Shabib, G.; Elbase, Adel A. ...
2017 Intl Conf on Advanced Control Circuits Systems (ACCS) Systems & 2017 Intl Conf on New Paradigms in Electronics & Information Technology (PEIT),
2017-Nov.
Conference Proceeding
The world is turning towards smart grids. However, upgrading the existing systems could be the easiest solution for such approach. On the other hand, Load Frequency Control (LFC) is a critical issue ...in the dynamical operation of power systems. This paper presents LFC scheme for a realistic Power System operational in Egypt(EPS) with inherent nonlinearities. Moreover, the speed response of every subsystem is different from each other. The effects of the physical constraints such as Generation Rate Constraints (GRC) of power plants and speed governor dead band (blackash) are taken into consideration. In this paper, each subsystem controller has been designed independently to guarantee the stability of the overall closed loop system. Hence, optimal PID controllers based on Particle Swarm Optimization (PSO) algorithm are proposed for every subsystem separately to regulate the frequency and track the load. In order to investigate the ability of upgrading the system to smart grids, the performance of the proposed decentralized PID controller of each subsystems is compared with aggregate one. The proposed model can achieve a robust stability against changing the system parameters and operating load condition for the EPS with multi-source environment. The results by nonlinear simulation Matlab/Simulink for the EPS LFC approves that the decentralized model of the controller gives the same performance as the aggregated one. However, in case of large disturbances, the aggregated controller design cannot handle the fault while the decentralized scheme is more robust and effective against all disturbances and operating conditions. In contrast, in the advanced smart grids, the aggregated design would give a better flexible control strategy for the system.
The rise of electricity demand in a power system requires the use of discrete-time devices. They are widely spread and play an essential task in the operation and control of power systems. Several ...kinds of digital controlled devices have been put into practical use in power systems for the last decade, such as power system stabilizer PSS, automatic voltage regulator AVR, and proportional-integral plus derivative PID controllers. In this paper, an online digital PSS is designed for single machine infinite-bus systems. In this study the power system (plant) is represented by nonlinear model while the PSS (controller) is represented by a three-pole three-zero, lead-lag type PSS. Tustin's discretization method is used to discretize the transfer function of the PSS. The effect of sampling intervals on the proposed digital PSS parameters is examined through simulations. They show that this approximation yields a good digital PSS for sufficiently small intervals. It was also found that, to counter larger disturbances, smaller sampling intervals are desired (about 2 ms-8 ms). For larger sampling intervals, fine-tuning of digital PSS parameters is required. The digital PSS is applied to one machine infinite-bus system, tested for different load conditions and disturbances, and found to be satisfactory.
The wind turbine operating area can be divided into several regions, depending on wind speed. Transition from fixed speed to variable speed wind turbines has been a significant element in the Wind ...energy technology improvements. This has allowed adapting the turbine rotational speed to the wind speed variations with the aim of optimizing the aerodynamic efficiency. In this paper, a multivariable control strategy based on model predictive control (MPC) techniques for the control of variable-speed variable-pitch wind turbines is introduced. The main advantages of the proposed controller are that it is easily adaptable for different conditions in addition to its very fast response. The proposed control strategy is described for the two operating regions of the wind turbine, i.e. both partial and full load regimes. Pitch angle and generator torque are controlled simultaneously to maximize the captured energy and smooth the power generated while reducing the pitch actuator activity. Simulation results show an excellent performance in improving the transition from power optimization to power limitation of the wind turbine.
