Stability Of Hybrid Power System Research Articles

Saturated full model capability of virtual synchronous generator to improve transient stability of hybrid power system

In hybrid power system (HPS), there are many inverter-based generators (IBGs) that inject renewable energy into the system as electrical power. Transient stability analysis of HPS in which synchronous generators (SGs) are operated in parallel with IBGs is necessary to operate the network safely under large disturbances. This paper examines the transient behaviour of IBGs with effective strategies, in which constraint on output current of IBGs is strictly considered to bring the results closer to reality. The control strategy is based on reference model tracking and substitution theory for networks, including parallel SG-IBGs to full IBGs. First, for a network with full IBGs, a constant power model reference is proposed as a static model. Then a dynamic reference model called saturated full model of virtual synchronous generator (VSG) or simply SFMVSG is introduced as the final solution for the controller of IBG in HPS. The SFMVSG has all existing VSG features and provides virtual damping torque created by the interaction of virtual damping fluxes. The simulation results confirm that the study is efficient.

Secure Frequency Control of Hybrid Power System Under DoS Attacks via Lie Algebra

Secure frequency control of multi-area hybrid power systems with wind power is a research problem involving active defense, vulnerability, and resilience. Considering the scenario that Denial-of-Service (DoS) attack intrude into the control channels of thermal power and wind farm, the hybrid power system is modeled by a switched system with four subsystems. Then, the exponential stability of hybrid power system is studied under arbitrary DoS attack. An active defense scheme is proposed to design switched control gains by Lie algebra method achieved by a distributed consensus method. Furthermore, following the resulted exponential stability, the load disturbance attenuant performance of frequency control is studied by the proposed concepts of vulnerability point and resilience point. Under a class of event-DoS attack model, the estimation method of vulnerability point and resilience point is given. Finally, simulations of a three-area hybrid power system and NE39bus test system are carried out to verify our theories.

Damping controller design based on FO-PID-EMA in VSC HVDC system to improve stability of hybrid power system

Wind energy sources have different structures and functions from conventional power plants in the power system. These resources can affect the exchange of active and reactive power of the network. Therefore, power system stability will be affected by the performance of wind power plants, especially in the event of a fault. In this paper, the improvement of the dynamic stability in power system equipped by wind farm is examined through the supplementary controller design in the high voltage direct current (HVDC) based on voltage source converter(VSC) transmission system. In this regard, impacts of the VSC HVDC system and wind farm on the improvement of system stability are considered. Also, an algorithm based on controllability (observability) concept is proposed to select most appropriate and effective coupling between inputs-outputs (IO) signals of system in different work conditions. The selected coupling is used to apply damping controller signal. Finally, a fractional order PID controller (FO-PID) based on exchange market algorithm (EMA) is designed as damping controller. The analysis of the results shows that the wind farm does not directly contribute to the improvement of the dynamic stability of power system. However, it can increase the controllability of the oscillatory mode and improve the performance of the supplementary controller.

Optimal Fractional Order BELBIC to Ameliorate Small Signal Stability of Interconnected Hybrid Power System

The small signal stability of power systems integrated with fallback large‐scale distributed energy resources is of utmost importance during the perturbation conditions. Among the various renewable resources in power systems: photovoltaic, fuel cell, wind turbine, diesel engine, aqua electrolyser, battery, ultra‐capacitor, and flywheel is becoming more favored in last decades. AGC, a main control system of frequency modulation, must correctly alleviate the low frequency oscillations caused by the perturbation and variable output power of renewable resources. In this regard, FOBELBIC is here introduced to enhance the damping capability of AGC. Since both the frequency and tie‐line power oscillations must be concomitantly alleviated, the small signal stability problem has been multi‐objectively formulated. Due to the exploration capability of MOALO, it has been chosen to extract the optimal parameters of FOBELBIC. Furthermore, MOPSO, MOBA, and NSGA‐II have been studied to demonstrate the capability of MOALO. To verify and validate the damping performance of suggested controller, it has been evaluated in three‐area reconstructed power system under the load perturbations as well as wind speed and sun radiation variations, and at the same time compared with BELBIC and PID controllers. Finally, the simulation results have evidently confirmed the damping the performance of MOALO‐based FOBELBIC to enhance the small signal stability of hybrid power system. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019

A New Hybrid PSS Optimization Method Based on Improved Active Set Algorithm

This paper proposes a new hybrid optimization method for the phase-frequency characteristics of the double input power system stabilizer (PSS) based on the improved active set algorithm. This method takes the effect of the filtering section optimization on the parameter improvement into account, and the optimized model focuses on the minimum residual sum of squares between the actual and the target phase-frequency characteristics. The result shows that the improved parameters obtained from the proposed method provide much better phase-frequency characteristics than the widely used engineering parameters. The comparison between the proposed method and the typical commercial software indicates the universal superiority of the proposed method. And the studies on the impact of considering the filter section optimization on the phase-frequency improvement show that taking the filter section optimization into account will be beneficial for the phase-frequency improvement, though in application to the PSS2A model and the PSS2B model there are some differences. The achievements obtained in this paper provide a significant reference for the practical PSS parameter modification and improvement.

Decentralized coordinated neural control of doubly fed induction generator based wind farm for power system stability support

This paper aims at improving the excitation control system for the doubly fed induction generator-based wind farm (WF). The proposed decentralized coordinated neural control is consisted of two controllers, i.e., a multiple model predictive controller (MPC) and an artificial neural network (ANN) controller. The MPC is based on the interaction measurement model and designed to guarantee the performance of system-wide optimization around the chosen operating points, while the ANN controller is used to calculate the weights of MPC controllers and trained to guarantee the control performance over the full operating region. The proposed control strategy allows to reduce the computational cost, and at the same time to take advantage of the distributed nature of the power system. Moreover, a simple, generic hybrid power system is used to demonstrate transient stability contributions. The problems of large-scale WF integration and its impact on transient stabilities of power systems are discussed through the eigenvalue analysis and time domain simulation. The results show that system damping and transient stability of hybrid power system are considerably improved.

An Application of Developing Renewable Energy in an Extreme Arid and Energy-Scarce Area in Tarim Desert

This paper provides the systemic procedure to introduce local renewable energy into the local power system in the Tarim Desert and foot of the Kunlun Mountain. This research takes seven townships of Qira County as the research basis. By using forecast technique, the Intensive Load-Area was formed based on the forecasted local population and load condition by the year 2020. According to the local urbanization plan that is widely applied in Xinjiang Uygru Autonomous Region (XUAR), this paper defines the two types of rural power system namely township branch system and village terminal system. The optimal development procedure makes a small-scaled and weak power system expanded it's the ultimate ability to accept the capacity of renewable energy. According to national standard indexes, special simulation is used for testing stability of hybrid power system in normal operation and dynamic performance under the composed operational manners. The numerical statistics indicate the efficiency of saving energy and protecting the desert environment after introducing renewable energy.

A Hybrid Power System Stabilizer Using Neuro-identifier and Predictive Controller

This paper presents the development of a hybrid power system stabilizer (PSS) model designed to enhance the damping characteristics of a practical power system network representing a part of the Electricity Generating Authority of Thailand (EGAT) system. The PSS consists of a predictive controller and a neuro-identifier which has been developed based on the functional link network (FLN) model. A recursive on-line training algorithm has been proposed to train the neural network. Simulation results have been obtained under various operating conditions and severe disturbance cases that show that the proposed PSS can provide a better damping to the local as well as interarea modes of oscillations, as compared with a conventional PSS.

A neuro-fuzzy hybrid power system stabilizer

Abstract The paper presents a novel neuro-fuzzy hybrid power system stabilizer (PSS) design for damping electromechanical modes of oscillation and enhancing power system synchronous stability. The hydrid PSS comprises a front-end conventional analog PSS design, an artificial neural network (ANN) based stabilizer, and a fuzzy logic post-processor gain scheduler. The stabilizing action is controlled by the post-processor gain scheduler based on an optimized fuzzy logic excursion based criterion J0. The two PSS stabilizers, conventional and neural network, have their damping action scaled online by the magnitude of J0 and its rate of change dJ0. The ANN feedforward two-layer based PSS design is the curve fitted nonlinear mapping between the damping vector signals and the desired optimized PSS output and is trained using the benchmark analog PSS conventional design. The fuzzy logic gain scheduling post-processor ensures adequate damping for large excursions, fault conditions, and load rejections. The parallel operation of a conventional PSS and a neural network PSS provides optimal sharing of the damping action under small as well as large-scale generation-load mismatch or variations in external network topology due to fault or switching conditions.

Slow-coherency based composite mode oscillatory stabilization by means of a hybrid PSS

This paper addresses the problem of the stabilization of composite mode electromechanical oscillations of generators. A Hybrid PSS of the two-level structure including of a local PSS and a global PSS is introduced. Time-scale decomposition is applied to the decoupling of the local and global stabilization problems, where determination of the global (inter area) control law is based on slow-coherency aggregation. Composite mode electromechanical rotor oscillations are observed, in practice, with weakly interconnected power systems. These oscillations are characterized by local and inter-area modes. In certain cases of operating conditions and/or network topology, the damping of these oscillatory modes may be negligible or even negative. The existing approaches to the stabilization of power system are basically in decentralized way, and the objective of the stability measures are largely concentrated on the damping improvement of local modes by means of a power system stabilizer (PSS), using only the local information. However, for those systems with poorly or negatively damped inter-area modes, applications of the locally tuned PSS cannot bring a total stabilization to the system, and the inter-area oscillations remain unaffected or possibly building-up to excessive margins. In this paper we have introduced the idea of the Hybrid PSS which is of a two-level control structure with local and global inputs, as in Fig. 1. The desired supplementary control signal for composite mode oscillations is obtained by a weighted combination of the local and global (inter-area) stabilization signals.

Implementation of a hybrid power system stabilizer

Dynamic stability enhancement of composite mode oscillations of interconnected power systems by means of a hybrid power system stabilizer is discussed. The proposed hybrid PSS is of a two-level structure composed of a local mode and a global PSS inter-area mode damping. The input of the global stabilizer is the center of inertia speed deviation of slow-coherent generators. This work is mainly focused on the practical considerations in implementation of the proposed stabilizer. The optimum allocation of this stabilizer is discussed. An index of mode-input-assignability, by which the best sites of the stabilizer can be identified, is introduced. For practical applications, an estimation for the approximation of the input of the global PSS is introduced. An approximated value of the center of inertia speed is obtained from a suitable combination of the rotor speed data of a few properly selected key generators.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Implementation of a Hybrid Power System Stabilizer

Dynamic stability enhancement of composite mode oscillations of interconnected power system by means of a hybrid power system stabilizer is discussed here. The proposed Hybrid PSS is of a two-level structure composed of a local PSS for local mode and a global PSS for inter-area mode damping as in Fig. 1. The input of the global stabilizer is the center of inertia speed deviation of slow-coherent generators. The present paper is mainly focused on the practical considerations in implementation of the proposed stabilizer. First, the optimum allocation of this stabilizer is discussed. We introduce an index of "modeinput-assignability," by which the best sites of the stabilizer can be identified. Next, for practical applications, an estimation method for the approximation of the input of the global PSS is introduced. Here, an approximated value of the center of inertia speed is obtained from a suitable combination of the rotor speed data of a few properly selected "key generators." Lightly damped or even negative damping oscillatory modes associated with rotor dynamics of synchronous generators are widely experienced in practice. When the individual power grids are interconnected with AC tie-lines, it forces the generating units to participate in both local and inter-area oscillations, which are referred to "composite mode oscillations." Our research is concerned with the dynamic stability enhancement of interconnected power systems through stabilization of composite mode electromechanical oscillations.