Power System Stability Control Research Articles

Coordinated Design of PSS and TCSC Controller for Power System Damping Improvement with Multiple Control Design Requirements

In this paper an Optimization based linear control design method is used to achieve a coordinated design of Power System Stabilizer (PSS) and Thyristor Controlled Series Capacitor (TCSC) for power system damping improvement with pre specified control design requirements. The settling time is considered as main performance criteria in time domain specification and gain and phase margins for frequency domain specifications. The main objective of the coordination of controllers is to improve the global stability through damping of oscillations by improving the damping ratio of the system and minimizing the settling time of the system response. Thus coordination increases the reliability of the system and maintains the required damping even one or more controllers are out of service and hence reduces the need for additional controller. Optimization based linear control design is used to determine the optimal gain and time constant setting of lead-lag controller parameters for PSS and TCSC. The coordinated PSS and TCSC controller is tested in the Single Machine Infinite Bus Power System (SMIB). Simulation is carried out using Matlab2011b. From the time domain simulation results it is observed that oscillations are damped out, settling time is reduced and damping ratio is improved. From bode plot it is inferred that gain and phase margin of the system is further improved to satisfy the system requirements. In the overall analysis, optimization based linear control design implemented for the coordination of PSS and TCSC controller satisfies the practical requirements of the power system oscillation damping problem, also shift the eigen values to the left half of the s-plane as far as possible and hence enhances the overall system stability

Damping control strategies of inter-area low-frequency oscillation for DFIG-based wind farms integrated into a power system

This study investigates the inter-area low-frequency damping control strategies of a doubly fed induction generator (DFIG)-based wind farm through oscillation transient energy function (OTEF) analysis. Based on the OTEF descent expressions, the feasibility of damping the inter-area low-frequency oscillation is theoretically analyzed through the active/reactive power control of grid-connected wind farms. Additional damping control strategies with the active/reactive power loop of the DFIG-based wind farm are presented using the feedback signal of the transmission line active power flow based on the power system stabilizer (PSS) control method. Transient simulation on different damping gain coefficients are conducted for justification. Following the OTEF mechanism analysis, an additional fuzzy damping control strategy with the active/reactive power loop is proposed by identifying the oscillation phase and the severity to prevent different damping gain coefficients from affecting the presented PSS damping control method. Transient and dynamic simulation results and comparisons showed that both additional control strategies with the active and reactive power loops of the DFIG-based wind farm can damp the inter-area low-frequency oscillation of the integrated power system. The additional damping control strategy with the reactive power loop can damp the transmission line active power oscillation better than that with the active power loop as well as prevent an increase in the torsional oscillation of the wind turbine shaft. The proposed additional fuzzy control strategy with the active/reactive power loop has better damping performance than the presented PSS control, especially for damping the inter-area low-frequency oscillation.

Design and experimental evaluation tests of a Takagi–Sugeno power system stabiliser

In this study, the design, implementation and experimental evaluation tests of a Takagi-Sugeno power system stabiliser (TSPSS) controller is presented. The controller was designed in order to provide a good damping for dominant electromechanical oscillations in power systems for the set of allowed operating conditions. In the proposed TSPSS controller, such requirement was accomplished by implementing a supervision scheme which performs the adaptation of the TSPSS parameters at each sample time, according to the current detected plant operating condition. The TSPSS controller has been implemented as a microcontroller-based embedded system and its performance was assessed by performing experimental tests in a laboratory scale (10 kVA) power system as well as in field tests performed in a large (350 MVA) generating unit, at Tucurui Hydroelectric Power Plant. The experimental results also show the good performance of the TSPSS to cope with varying plant operation condition.

A real-time nonlinear decentralized control of multimachine power systems

This paper proposes the application of a new nonlinear decentralized control to the multi-input multi-output model of multimachine power systems. The goal is to control the terminal voltage as well as the rotor angle to obtain high-performance transient stability and good post-fault voltage regulation. The proposed stabilizing feedback laws for the power system are shown to be globally asymptotically stable in the context of Lyapunov theory. The effectiveness of the proposed control action is demonstrated through some computer simulations on a two-area benchmark power system under a large sudden fault and a wide range of operating conditions. The results are compared with those of the traditional automatic voltage regulator (IEEE type I AVR) plus the power system stabilizer control structure and speed governor.

An Improved Optimal Algorithm of N-1 PMU Location

PMU has been widely used in the power system state estimation, dynamic monitoring, and stability control. To achieve system completely observable and a certain degree of reliability, we need to set N-1 redundancy for PMU in the system. LR is a traditional method solving the N-1 best location problem. However, it can't meet the need of economical efficiency due to its oversimplified computation. This article make the biggest intersection between the solution from which that won't set redundancy and that from the LR[ method. On the basis of the intersection result, several iteration is needed to get the appreciate result which would lead the least cost.

The Lagrangian of Analytical Mechanics and its Application in Power System with TCSC

The research and development of Hamilton system have provided an effective approach for the nonlinear analysis and stability control of power system. It also plays an important role in the control of flexible AC transmission system. The application of Lagrange analytical mechanics can improve the realization of Hamilton system and the controller design. The model of single-machine infinite-bus system with TCSC is extended to an even-order system in this paper. On the basis of self-adjoint conditions the standard form of Hamilton realization is obtained with the theory of Lagrange mechanics. By non-conservative analytical mechanics theory, the system controller is designed and Matlab programming is realized on the single-machine infinite-bus system. The simulation effects of the designed controller and general controller under three-phase grounded short-circuit faults are compared, which verifies the effectiveness of the proposed control strategy in this paper. The construction of Hamilton function and design of the controller have a broad prospect of applications.

A Power System Stabilizer for Wind Power Generation

The parameter setting of the power system stabilizer (PSS) is very important. This paper presents a PSS for wind power generation. We describe a method of simulation for PSS based on MATLAB Simulink, and research that how to build the mathematic model and get the parameters that are fitted to the real power plant generator Excitation System and PSS used the Real Time Digital Simulator (RTDS), then builds the model on RTDS, and does the simulated testing. It is shown that this PSS can significantly influence the contribution that a wind farm can make to network damping. The optimal parameters of PSS can be obtained quickly through the approach of parameter optimization and it is a high efficiency and practicable parameter setting method. Performance capabilities superior to those provided by synchronous generation with automatic voltage regulator and PSS control are demonstrated.

Combined design of VSC-HVDC and PSS controllers for LFO damping enhancement

The purpose of this paper is to present a novel combined design of the voltage source converter–high voltage direct current (VSC-HVDC) and the power system stabilizer (PSS) controllers to obtain a better dynamical response. The proposed technique is applied to enhance the damping of the power system low-frequency oscillations (LFOs) and results are compared with traditional design. A fuzzy logic controller is designed for PSS (FPSS). Then, a chaotic optimization algorithm, which has a strong ability for finding the most optimistic results, is employed, in presence of FPSS, to search for optimal VSC-HVDC output feedback controller parameters. Moreover, a singular value decomposition method is utilized to select the most effective damping control signal of the VSC-HVDC output feedback controllers. The novel proposed controllers are evaluated on an AC/DC power system. The simulation results demonstrate that the combined controllers have an excellent capability for damping power system LFOs and greatly enhance the dynamic stability of the power system. Also, the system performance analysis under different operating conditions and some performance indices show the effectiveness of the proposed controllers. The benefit of the suggested procedure is greatly improving the dynamic response of the system. In addition, the overshoots, undershoots and the settling times are dramatically reduced by applying the proposed method.

Adaptive robust PSS to enhance stabilization of interconnected power systems with high renewable energy penetration

Today, the penetration of renewable energies in power system significantly increases. However, the intermittent power of renewable energies may cause severe problems of low frequency oscillations in interconnected power systems due to insufficient system damping. Moreover, the operating condition of power system may change any time. This paper proposes a design of adaptive robust power system stabilizer (PSS) to damp low frequency oscillations in an interconnected power system with high renewable energy (RE) penetration. System identification is used to construct an estimated model, and the estimated model will be updated whenever the estimated mismatch exceeds predetermined bound. Based on the estimated model, the PSS controller of each generator will be re-tuned using a genetic algorithm. The optimization problem is formulated to guarantee the robustness of PSS and to increase the damping ratio of the dominant mode. In this work, we also install a memory so that several models and corresponding PSS parameter sets can be stored in the memory and re-used in the similar situations. Moreover, the PSSs on generators are able to control without communications among them; it will reduce investment cost significantly. The performance, effectiveness and robustness of the proposed method have been investigated in an interconnected power system in comparison with a conventional PSS (CPSS). Simulation results confirm that the damping effects of the proposed PSS are much better than that of the CPSS against various operating conditions and system uncertainties.

Coordinative Optimal Design for PSS and Auxiliary Damping Controller on SVC under Multi-Operating Conditions

Based on power system stabilizer (PSS) and the damping controller of flexible AC transmission system (FACTS),a problem of optimal design is researched by the example of static var compensator (SVC). Minimum damp ratio of system electromechanical oscillation modes eigenvalue in the weak damping operation condition is selected as the object function. Parameters of damping controllers are optimized by the algorithm which is combined by genetic algorithm (GA) and back propagation (BP) neural network based on adaboost (Ada-BP). Simulation shows the optimized damping controllers can restrain the low frequency oscillation in multi-operating conditions of system. The algorithm provides an effective solution for optimization calculations which calls the complicated calculations.

Optimal Comprehensive Control of Prevention and Emergency Based on DSR and Probabilistic Insecurity Measurement

Transient stability control of power system is a non-linear optimization problem which contains many constraints. Considering the cost of preventive control, emergency control and the following restorative control synthetically, a model of preventive control and emergency control based on DSR(Dynamic Security Region) and probabilistic insecurity measurement is proposed in the paper, and the optimal operating point of the system was obtained by using the improved genetic algorithm. In the end, the feasibility of the model and optimization strategy are verified by the case of the IEEE 4-generators 11-nodes system. Simulation show that the cost of comprehensive control of prevention and emergency is 13.2% less than the case that without the consideration of the random factors of the fault.

A novel current injection model of PWMSC for control and analysis of power system stability

This paper proposes a novel current injection model of Pulse width Modulation based Series Compensator (PWMSC), as new FACTS controller, for damping of low frequency oscillations. The PWMSC operates as a means of continuous control of the degree of series compensation through the variation of the duty cycle of a train of fixed frequency-pulses. The methodology is tested on the sample single machine power system including PWMSC controller by performing computer simulations for small and large distributions. MATLAB/ Simulink software package was used for the simulations.

Optimal Coordinated Design of Multiple Damping Controllers Based on PSS and UPFC Device to Improve Dynamic Stability in the Power System

Unified Power Flow Controller (UPFC) device is applied to control power flow in transmission lines. Supplementary damping controller can be installed on any control channel of the UPFC inputs to implement the task of Power Oscillation Damping (POD) controller. In this paper, we have presented the simultaneous coordinated design of the multiple damping controllers between Power System Stabilizer (PSS) and UPFC-based POD or between different multiple UPFC-based POD controllers without PSS in a single-machine infinite-bus power system in order to identify the design that provided the most effective damping performance. The parameters of the damping controllers are optimized utilizing a Chaotic Particle Swarm Optimization (CPSO) algorithm based on eigenvalue objective function. The simulation results show that the coordinated design of the multiple damping controllers has high ability in damping oscillations compared to the individual damping controllers. Furthermore, the coordinated design of UPFC-based POD controllers demonstrates the superiority over the coordinated design of PSS and UPFC-based POD controllers for enhancing greatly the stability of the power system.

Improving power system dynamic performance using attuned design of dual-input PSS and UPFC PSD controller

The objective of this work is the coordinated design of controllers that can enhance damping of power system swings. With presence of flexible AC transmission system (FACTS) device as unified power flow controller (UPFC), three specific classes of the power system stabilizers (PSSs) have been investigated. The first one is a conventional power system stabilizer (CPSS); the second one is a dual-input power system stabilizer (dual-input PSS); and the third one is an accelerating power PSS model (PSS2B). Dual-input PSS and PSS2B are introduced to maintain the robustness of control performance in a wide range of swing frequency. Uncoordinated PSS and UPFC damping controller may cause unwanted interactions; therefore, the simultaneous coordinated tuning of the controller parameters is needed. The problem of coordinated design is formulated as an optimization problem, and particle swarm optimization (PSO) algorithm is employed to search for optimal parameters of controllers. Finally, in a system having a UPFC, comparative analysis of the results obtained from application of the dual-input PSS, PSS2B, and CPSS is presented. The eigenvalue analysis and the time-domain simulation results show that the dual-input PSS & UPFC and the PSS2B & UPFC coordination provide a better performance than the conventional single-input PSS & UPFC coordination. Also, the PSS2B & UPFC coordination has the best performance.

Power System Stability Enhancement via Bacteria Foraging Optimization Algorithm

Social foraging behavior of Escherichia coli bacteria has recently been explored to develop a novel algorithm for distributed optimization and control. The Bacterial Foraging Optimization Algorithm (BFOA) is currently gaining popularity in the community of researchers, for its effectiveness in solving certain difficult real world optimization problems. This paper proposes BFOA-based power system stabilizer (PSS) for the suppression of oscillations in power systems. The proposed design problem of PSS over a wide range of loading conditions and system configurations is formulated as an optimization problem. BFOA is employed to search for optimal controller parameters by minimizing the time domain objective function.The performance of the proposed technique has been evaluated with the performance of genetic algorithm, the Conventional one and no controller in order to demonstrate the superior efficiency of the proposed BFOA in tuning PSS controller. Simultaneous tuning of the Bacterial Foraging-based PSS gives robust damping performance over wide range of operating conditions, and system configurations in comparison to optimized PSS controller based on GA and conventional PSS.

PSS CONTROLLER FOR WIND POWER GENERATION SYSTEMS

Small signal stability analysis for power systems with wind farm interaction is presented. Power systems oscillation modes can be excited by disturbance or fault in the grid. Variable speed wind turbines can be regulated to reduce these oscillations, stabilising the power system. A power system stabiliser (PSS) control loop for wind power is designed in order to increase the damping of the oscillation modes. The proposed power system stabiliser controller is evaluated by small signal analysis.

Robust Wide-Area TS Fuzzy Output Feedback Controller for Enhancement of Stability in Multimachine Power System

This paper presents a systematic procedure for designing a wide-area centralized Takagi-Sugeno fuzzy controller to improve the angular stability of a multimachine power system. The proposed fuzzy controller is robust and designed by satisfying certain linear matrix inequality conditions, to stabilize the system at multiple operating points. The bilinear matrix inequality problem, encountered in Lyapunov-based stability criterion, has been converted into a convex optimization problem to eliminate iterative solution. The input-output control signals are selected in the proposed control scheme by defining joint model controllability and observability index applying geometric approach. The proposed wide-area control scheme employs a global signal from the centralized controller to damp out the interarea mode of oscillations, apart from the local controllers, which are assumed to be present to damp out the local mode of oscillations. The proposed control scheme has been implemented on three test systems. The effectiveness of the proposed control scheme has been compared with a robust wide area control scheme based on mixed H2/H∞ output feedback synthesis and with a conventional power system stabilizer control scheme.

Mode selective damping of power system electromechanical oscillations for large power systems using supplementary remote signals

This paper presents the design of local decentralized power system stabilizer (PSS) controllers, using selected suitable remote signals as supplementary inputs, for a separate better damping of specific inter-area modes, for large-scale power systems. System identification technique is used for deriving lower order state-space models suitable for control design. The lower-order model is identified by probing the network in open loop with low-energy pulses or random signals. The identification technique is then applied to signal responses, generated by time-domain simulations of the large-scale model, to obtain reduced-order model. Lower-order equivalent models, thus obtained, are used to design each local PSS controller separately for each of the inter-area modes of interest. The PSS controller uses only those local and remote input signals in which the assigned single inter-area mode is most observable and is located at a generator which is most effective in controlling that mode. The PSS controller, designed for a particular single inter-area mode, also works mainly in a frequency band given by the natural frequency of the assigned mode. The locations of the local PSS controllers are obtained based on the amplitude gains of the frequency responses of the best-suited measurement to the inputs of all generators in the interconnected system. For the selection of suitable local and supplementary remote input signals, the features or measurements from the whole system are pre-selected first by engineering judgment and then using a clustering feature selection technique. Final selection of local and remote input signals is based on the degree of observability of the considered single mode in them. To provide robust behavior, H∞ control theory together with an algebraic Riccati equation approach has been applied to design the controllers. The effectiveness of the resulting PSS controllers is demonstrated through digital simulation studies conducted on a sixteen-machine, three-area test power system.

Coordinated design of PSSs and SVC via bacteria foraging optimization algorithm in a multimachine power system

This paper develops a novel algorithm for simultaneous coordinated designing of power system stabilizers (PSSs) and static var compensator (SVC) in a multimachine power system. The coordinated design problem of PSS and SVC over a wide range of loading conditions is formulated as an optimization problem. The Bacterial Foraging Optimization Algorithm (BFOA) is employed to search for optimal controllers parameters. By minimizing the proposed objective function, in which the speed deviations between generators are involved; stability performance of the system is improved. To compare the capability of PSS and SVC, both are designed independently, and then in a coordinated manner. Simultaneous tuning of the bacterial foraging based coordinated controller gives robust damping performance over wide range of operating conditions and large disturbance in compare to optimized PSS controller based on BFOA (BFPSS) and optimized SVC controller based on BFOA (BFSVC). Moreover, a statistical T test is performed to ensure the effectiveness of coordinated controller versus uncoordinated one.

Gravitational search algorithm for coordinated design of PSS and TCSC as damping controller

A newly developed heuristic global optimization algorithm, called gravitational search algorithm (GSA), was introduced and applied for simultaneously coordinated designing of power system stabilizer (PSS) and thyristor controlled series capacitor (TCSC) as a damping controller in the multi-machine power system. The coordinated design problem of PSS and TCSC controllers over a wide range of loading conditions is formulated as a multi-objective optimization problem which is the aggregation of two objectives related to damping ratio and damping factor. By minimizing the objective function with oscillation, the characteristics between areas are contained and hence the interactions among the PSS and TCSC controller under transient conditions are modified. For evaluation of effectiveness and robustness of proposed controllers, the performance was tested on a weakly connected power system subjected to different disturbances, loading conditions and system parameter variations. The eigenvalues analysis and nonlinear simulation results demonstrate the high performance of proposed controllers which is able to provide efficient damping of low frequency oscillations.