Multiple Power System Stabilizers Research Articles

Comparative analysis of probabilistic and deterministic approach to tune the power system stabilizers using the directional bat algorithm to improve system small-signal stability

The modern power system consists of a large mixture of renewable energy sources (RES), varying and flexible loads, and is also experiencing a situation where a significant number of conventional generators are being replaced by power electronics based sources. All of these factors may lead to a decrease in the small-signal stability (SSS) margin of the system which in turn can cause power system instability. Power system stabilizers (PSSs) are widely used to improve the low-frequency oscillatory stability of power systems. Currently, there are two popular methods to coordinate multiple PSSs to improve SSS: deterministic and probabilistic method. This paper first formulates the problem of coordinating multiple PSSs to improve SSS as a deterministic and a probabilistic optimization problem which is then solved using the new directional bat algorithm. A detailed comparison between the two design methods under different scenarios based on obtained results is carried out afterward. All of the analysis was carried out on a modified IEEE 68 bus system. The obtained results provide key insights as well as the advantages and limitations of the probabilistic and deterministic approach to optimize the PSS parameters.

Adaptive Damping Control Strategy of Wind Integrated Power System

Random variation of grid-connected wind power can cause stochastic variation of the power system operating point. This paper proposes a new scheme to design an adaptive damping controller by tracking the variation of system operating points and updating the controller’s functions to achieve a robust damping control effect. Firstly, the operating space is classified into different modes according to the classification of wind power outputs. Multiple power system stabilizers (PSSs) are then designed. Secondly, the method of optimal classification and regression decision tree (CART) is utilized for classifying subspaces of system operating point and it is proposed that the on-line measurements from wide area measurement system (WAMS) are used for tracking the dynamic behaviors of stochastic drifting point and thus guide the updating of appropriate PSSs be switched on adaptively. A 16-generator-68-bus power system integrated with wind power is presented as a test system to demonstrate that the adaptive control scheme by use of the CART can damp multi-mode oscillations effectively when the wind power output changes.

Multi-machine optimal power system stabilizers design based on system stability and nonlinearity indices using Hyper-Spherical Search method

Design of power system stabilizer (PSS) withstanding critical situations is a challenging task. In this paper, an effective method for the design of a coordinated multiple PSS in power systems are offered and weaknesses of the existing methods are disclosed. The setup includes the nonlinear model of the system, a specific multi-objective function and a newly developed meta-heuristic Hyper-Spherical Search (HSS) optimization algorithm. The objective function includes both eigenvalue stability index (SI) and nonlinearity index (NI). The employed new NI is the second order modal interaction of the lightly damped electromechanical modes. The performance of the proposed Stability-Nonlinearity index (SN) based PSS design by HSS (SNPSS-HSS) is compared with SNPSS-GA, SI based PSS (SPSS) and the conventional design method (CPSS) under various operating conditions and disturbances. The investigations are conducted over both a single lead PSS and PSS2B. The performance is detailed using time domain simulations, SI and NI analysis. A four-machine two-area system and the IEEE 39-bus system are utilized for test purpose. The results of extensive simulations indicate the superiority of SNPSS-HSS design with respect to the others. The obtained relative stability is higher and the nonlinearity index is lower than the product of the other designs. Besides, as it is expected, using a high degree of freedom PSS2B improves the performance of the aforementioned algorithms.

Damped Nyquist Plot for a pole placement design of power system stabilizers

This paper proposes a new frequency domain control design method through the use of a modified Nyquist diagram with an embedded partial pole-placement capability. The proposed Damped Nyquist Plot (DNP) method evaluates the open loop transfer function (OLTF) along a line of constant damping ratio to provide a graphical tool to design power system stabilizers (PSS). The graphical tool shows how the closed loop poles move around this damping ratio line for different choices of PSS parameters, all of them placing a selected pair of complex-conjugate poles at the same desired point in the complex plane. New formulas are developed to determine the exact PSS parameters that promote the several possibilities of partial pole placement considering the parameter ranges used in tuning practice. These formulas can also be used for phase compensation of conventional methods of PSS design, such as GEP or Residue Angle Compensation. Multiple PSSs can be tuned using the DNP method sequentially. The proposed method is applied to two stabilization examples, the first of tutorial nature and the second is the large actual Brazilian Interconnected Power System.

Coordinated design of power system stabilizers and TCSC employing improved harmony search algorithm

Power System Stabilizers (PSS) are generally employed to damp electromechanical oscillations by providing auxiliary stabilizing signals to the excitation system of the generators. But it has been found that these Conventional PSS (CPSS) do not provide sufficient damping for inter-area oscillations in multi-machine power systems. Thyristor Controlled Series Capacitor (TCSC) has immense potential in damping of inter-area power swings and in mitigating the sub-synchronous resonance. In this paper Improved Harmony Search Algorithm (IHSA) has been proposed for coordinated design of multiple PSS and TCSC in order to effectively damp the oscillations. The results obtained by using IHSA on WSCC 3-machine, 9-bus system are found to be superior compared to the results obtained using Bacterial Swarm Optimization (BSO) algorithm. The damping performance of conventional PSS and TCSC controllers is also compared with coordinated design of IHSA based PSS and TCSC on New England 10-machine, 39-bus system over wide range of operating conditions and contingencies. To demonstrate the effectiveness of the proposed technique the results obtained on this test system are also compared with the results obtained with Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Harmony Search Algorithm (HSA) and Bacterial Swarm Optimization (BSO).

Coordinated Setting of Multiple PSSs for Actual Size Power Network

SUMMARYThe power system stabilizer (PSS) is a low‐cost method of stabilizing the intertie and local oscillations of a power network. The PSS parameters are usually adjusted based on the one‐machine infinite‐bus system model. In contrast, a real power system consists of multimachine systems. Thus, coordinated setting of the PSS parameters, with the real characteristics of the power system network taken into consideration, is expected to improve stability. For this purpose, the modal performance measure (MPM) method is used to adjust the PSS parameters. The power network mathematical model that is required for this calculation is given by the system identification method. Utilizing the MPM method characteristics, restrictions such as the damping coefficient and maximum gain, which constitute practical design specifications used for conventional controllers, are naturally introduced. Furthermore, radial basis function (RBF) frequency weighing is introduced in order to adjust the frequency responses. The expected favorable results were found in large‐scale power system simulations.

Optimal Coordination of Multiple ESS-based Stabilizers and PSS in Multi-machine Power System for Damping Improvement

This paper proposes to optimally coordinate multiple Energy Storage System (ESS) based stabilizers and Power System Stabilizers (PSS) to increase damping in a multi-machine power system using an improved particle swarm optimization (IPSO). The IPSO has the strong and global searching ability and high efficiency by applying chaos initialization and simulated annealing (SA) algorithm in iteration. All eigenvalues, including both electromechanical and non-electromechanical modes, that meet the stability requirements in a wide range of operating conditions have been included in the objective function. In the 4-machine power system, the power system oscillations are effectively suppressed at different operating conditions by multiple ESS-based stabilizers and PSSs coordinated by IPSO, where the damping effect is better with the stabilizers designed by the IPSO than with the stabilizers tuned individually by the conventional compensation method. The results show the validity, robustness and superiority of the IPSO design.

Coordinated Setting of Multiple PSSs for Actual Size Power Network

SUMMARY The power system stabilizer (PSS) is a low-cost method of stabilizing the intertie and local oscillations of a power network. The PSS parameters are usually adjusted based on the one-machine infinite-bus system model. In contrast, a real power system consists of multimachine systems. Thus, coordinated setting of the PSS parameters, with the real characteristics of the power system network taken into consideration, is expected to improve stability. For this purpose, the modal performance measure (MPM) method is used to adjust the PSS parameters. The power network mathematical model that is required for this calculation is given by the system identification method. Utilizing the MPM method characteristics, restrictions such as the damping coefficient and maximum gain, which constitute practical design specifications used for conventional controllers, are naturally introduced. Furthermore, radial basis function (RBF) frequency weighing is introduced in order to adjust the frequency responses. The expected favorable results were found in large-scale power system simulations.

Feasibility study to damp power system multi-mode oscillations by using a single FACTS device

To damp power system multi-mode oscillations, the commonly-used method is to arrange multiple decentralized stabilizers, such as PSS (Power System Stabilizer) and FACTS (Flexible AC Transmission Systems) stabilizers. In order to overcome the problem of interactions between stabilizers, coordinated design of multiple decentralized stabilizers has been proposed to simultaneously set parameters of all stabilizers. However, in practice it could be very difficult to implement the coordinated design of multiple stabilizers. This is because those stabilizers are often at different geographical locations in a power system and cross-location simultaneous field tuning of stabilizers’ parameters is a tremendous task due to their interactions. Hence this paper proposes a novel scheme of damping power system multi-mode oscillations by using a single FACTS device and presents the results of feasibility study of the proposed scheme. It is demonstrated that multiple stabilizers can be arranged in a single FACTS device to effectively damp power system multi-mode oscillations. Under this scheme, multiple stabilizers are at a same geographical location in the power system and hence their parameters can be tuned simultaneously in coordination in the field. In the paper, three examples of multi-machine power systems installed with a UPFC (Unified Power Flow Controller), a STATCOM (Static Synchronous Compensator)/BESS (Battery Energy Storage System) and a MUPFC (Multiple-terminal UPFC) respectively are presented. Parameters of multiple stabilizers are designed in coordination by using a newly appeared method of optimisation–artificial fish swarm algorithm. Simulation results in the paper are compared with those obtained from applying the conventional scheme of decentralized control involving multiple PSSs. They demonstrate and confirm the feasibility of proposed scheme in the paper.

RMP model based optimization of power system stabilizers in multi-machine power system

This paper describes the nonlinear parameter optimization of power system stabilizer (PSS) by using the reduced multivariate polynomial (RMP) algorithm with the one-shot property. The RMP model estimates the second-order partial derivatives of the Hessian matrix after identifying the trajectory sensitivities, which can be computed from the hybrid system modeling with a set of differential-algebraic-impulsive-switched (DAIS) structure for a power system. Then, any nonlinear controller in the power system can be optimized by achieving a desired performance measure, mathematically represented by an objective function (OF). In this paper, the output saturation limiter of the PSS, which is used to improve low-frequency oscillation damping performance during a large disturbance, is optimally tuned exploiting the Hessian estimated by the RMP model. Its performances are evaluated with several case studies on both single-machine infinite bus (SMIB) and multi-machine power system (MMPS) by time-domain simulation. In particular, all nonlinear parameters of multiple PSSs on IEEE benchmark two-area four-machine power system are optimized to be robust against various disturbances by using the weighted sum of the OFs.

Robust Coordinated Design of Multiple Power System Stabilizers Using Particle Swarm Optimization Technique

Robust Coordinated Design of Multiple Power System Stabilizers Using Particle Swarm Optimization Technique

Optimal location and controller design of STATCOM for power system stability improvement using PSO

The optimal location of a static synchronous compensator (STATCOM) and its coordinated design with power system stabilizers (PSSs) for power system stability improvement are presented in this paper. First, the location of STATCOM to improve transient stability is formulated as an optimization problem and particle swarm optimization (PSO) is employed to search for its optimal location. Then, coordinated design problem of STATCOM-based controller with multiple PSS is formulated as an optimization problem and optimal controller parameters are obtained using PSO. A two-area test system is used to show the effectiveness of the proposed approach for determining the optimal location and controller parameters for power system stability improvement. The nonlinear simulation results show that optimally located STATCOM improves the transient stability and coordinated design of STATCOM-based controller and PSSs improve greatly the system damping. Finally, the coordinated design problem is extended to a four-machine two-area system and the results show that the inter-area and local modes of oscillations are well damped with the proposed PSO-optimized controllers.

A comparison of classical, robust, and decentralized control designs for multiple power system stabilizers

Several control design techniques, namely, the classical phase compensation approach, the /spl mu/-synthesis, and a linear matrix inequality technique, are used to coordinate two power system stabilizers to stabilize a 5-machine equivalent of the South/Southeast Brazilian system. The open-loop system has an unstable intearea mode and cannot be stabilized using only one conventional power system stabilizer. Both centralized and decentralized controllers are considered. The different designs are compared and several interesting observations are provided.