Wide Area Control Research Articles

Design of Filter based Wide Area Damping Controllers in Power System

AbstractIn this paper, the concept of analog filter circuit is used for designing of wide area damping controller (WADC) in power system. The designed continuous mode filter based WADC is robust enough to deal with the problem of imperfect communication medium, which include process noise, measurement noise and signal latency in wide area remote signal. Residue method is used for the selection of wide area control signal and controller location. Modelling of imperfect communication network is done using Pade approximation and by inserting Gaussian random noise. The effectiveness of filter based WADC as a power system stability agent is assessed in the frequency domain using two typical test power systems and via appropriate time domain simulations based upon the non-linear model on MATLAB/Simulink software platform.

Designing a wide area damping controller to coordinate FACTS devices in the presence of wind turbines with regard to time delay

The main objective of this study is to increase the power system oscillation damping in the presence of wind farms using flexible alternating current transmission systems (FACTS) devices and predictive control. The desired design is conducted to coordinate static synchronous compensator-static synchronous series compensator and rotor side converter in doubly-fed induction generator (DFIG). This design is done to compensate for the DFIG reactive power and increase power system oscillation damping in the presence of uncertainties in the wind turbine. The method proposed for coordinated design was based on the network predictive control (NPC) so that it could improve damping, and compensate for the time delays in sending wide area signals. In fact, NPC is based on generalised predictive control (GPC) which has the ability to compensate for time delays using model identification method. Using MATLAB software, the simulation results were conducted on a 16-machine and 69-bus power system under different scenarios; and the ability of NPC is well proven compared with GPC and the classic method of wide area controller.

Integration of Renewables into the Wide Area Control Scheme for Damping Power Oscillations View Document

Integration of Renewables into the Wide Area Control Scheme for Damping Power Oscillations View Document

Scalable Coordinated Control of Energy Storage Systems for Enhancing Power System Angle Stability

In this paper, a scalable wide area control scheme using distributed model predictive control is proposed to enhance the angle stability of power systems following large disturbances. In this regard, dynamic model of the local subsystems in the multiarea power system is developed for the model predictive controller and each subsystem is controlled by the associated controller. The controller of each subsystem exchanges minimum information with the controllers of the neighboring subsystems to reach the final result. The proposed controller works based on optimality condition decomposition to coordinate the subsystems. In the proposed wide area control system, the available actuators are mechanical power and field voltage controller of a synchronous generator, and energy storage systems (ESS), which are able to provide synchronizing power support. The performance of the proposed transient stability controller is studied in the New England 68-bus test system. The simulation results demonstrate the effectiveness of the proposed method to improve the angle stability of power systems subsequent to severe disturbances in the system.

Assessing the Risk of Implementing System Integrity Protection Schemes in a Power System With Significant Wind Integration

System integrity protection schemes (SIPS) are widely applied to power networks to ensure their operating security. This is particularly important when a network is operating close to its limits. As a result of green initiatives, SIPS are being applied on many national networks to accommodate new generation interconnections and especially wind farms. However, this results in an increased probability of undesirable interactions between multiple SIPS and raises concerns about SIPS reliability. A procedure to assess the risk of SIPS maloperations and undesirable interactions between different SIPS on the same or neighboring systems is proposed in this paper. A numerical illustration of this method is presented using the PJM 5-bus system to demonstrate the performance of various SIPS solutions that involve advanced information communication technologies and wide area monitoring, protection, and control. The risk assessment method can be used to integrate the impact of SIPS into a SIPS-aided transmission expansion plan. A new type of SIPS with adaptive protection logics that adjusts to the increasingly variable system conditions and the performance of other protection schemes is proposed to manage the induced risk.

Distributed wide-area control of power system oscillations under communication and actuation constraints

In this paper a distributed Model Predictive Control design is presented for inter-area oscillation damping in power systems under two critical cyber–physical constraints — namely, communication constraints that lead to sparsification of the underlying communication network, and actuation constraints that respect the saturation limits of generator controllers. In the current state-of-art, distributed controllers in power systems are executed over fixed communication topologies that are most often agnostic of the magnitude and location of the incoming disturbance signals. This often leads to a sub-optimal closed-loop performance. In contrast, the communication topology for the proposed controller is selected in real-time after a disturbance event based on event-specific correlations of the generator states with the dominant oscillation modes that are excited by that event. Since these correlations can differ from one event to another, so can the choice of the communication topology. These correlations are used to identify the most important sets of generators that must exchange state information for enhancing closed-loop damping of the inter-area modal frequencies. Effectiveness of this strategy is shown via simulations on the 48-machine, 140-bus model for the Northeast Power Coordinating Council.

Algorithm for Fast and Efficient Detection and Reaction to Angle Instability Conditions Using Phasor Measurement Unit Data

In wide area monitoring, protection, and control (WAMPAC) systems, angle stability of transmission network is monitored using data from phasor measurement units (PMU) placed on transmission lines. Based on this PMU data stream advanced algorithm for out-of-step condition detection and early warning issuing is developed. The algorithm based on theoretical background described in this paper is backed up by the data and results from corresponding simulations done in Matlab environment. Presented results aim to provide the insights of the potential benefits, such as fast and efficient detection and reaction to angle instability, this algorithm can have on the improvement of the power system protection. Accordingly, suggestion is given how the developed algorithm can be implemented in protection segments of the WAMPAC systems in the transmission system operator control centers.

Distributed wide-area control of power system oscillations under communication and actuation constraints

Distributed wide-area control of power system oscillations under communication and actuation constraints

Energy Function Inspired Value Priority Based Global Wide-Area Control of Power Grid

Conventional wide-area control strategies that are deployed to damp inter-area oscillations use fixed a priori schemes based on modal analysis of the power system. As these controllers cannot be tuned online, such schemes fail to perform well during severe dynamic system changes. In this paper, a wide-area control architecture designed based on reinforcement learning and optimal adaptive critic network is proposed, that learns and optimizes the system closed-loop performance. Also, a value priority scheme is designed using a derived Lyapunov energy function for prioritization of local and the proposed wide-area global controller which ensures coherent damping of local and inter-area oscillations. The method increases the reliability and allows for automatic tuning of stabilizing controllers especially in the presence of wide-area monitoring constraints. Simulation results on 8-bus 5-machine and 68-bus 16-machine IEEE test systems highlight the efficiency of the proposed method.

Time-Delay Analysis of Wide-Area Voltage Control Considering Smart Grid Contingences in a Real-Time Environment

This paper addresses the time-delay effects of the wide-area monitoring and control systems (WAMCS) in smart power grids which may critically impact system stability. The main purpose is to conduct a detailed delay analysis of the WAMCS in case of grid contingences. This analysis is performed via an advanced WAMCS testbed where a flexible ac transmission system (FACTS) device is utilized and controlled via a wide-area controller (WAC). Phasor measurements units (PMUs) are adopted to collect the real-time measurements for the WAC. The testbed results from an interface of four main segments known as the WAC; the actual FACTS device, the local area controller, and the power grid system along with the PMUs are simulated via a real-time digital simulator. To mimic the real case scenario, both hardware-in-the-loop and software-in-the-loop schemes are adopted in the experimental testbed, considering time-delay effects. The results obtained clarify the effect of delay in WAMCS in case of smart grid contingences.

Reliability analysis of a phaser measurement unit using a generalized fuzzy lambda-tau(GFLT) technique

Nowadays power consumption is increasing day-by-day. To fulfill failure free power requirement, planning and implementation of an effective and reliable power management system is essential. Phasor measurement unit(PMU) is one of the key device in wide area measurement and control systems. The reliable performance of PMU assures failure free power supply for any power system. So, the purpose of the present study is to analyse the reliability of a PMU used for controllability and observability of power systems utilizing available uncertain data. In this paper, a generalized fuzzy lambda-tau (GFLT) technique has been proposed for this purpose. In GFLT, system components' uncertain failure and repair rates are fuzzified using fuzzy numbers having different shapes such as triangular, normal, cauchy, sharp gamma and trapezoidal. To select a suitable fuzzy number for quantifying data uncertainty, system experts' opinion have been considered. The GFLT technique applies fault tree, lambda-tau method, fuzzified data using different membership functions, alpha-cut based fuzzy arithmetic operations to compute some important reliability indices. Furthermore, in this study ranking of critical components of the system using RAM-Index and sensitivity analysis have also been performed. The developed technique may be helpful to improve system performance significantly and can be applied to analyse fuzzy reliability of other engineering systems.

Wide area damping of electromechanical low frequency oscillations using phasor measurement data

A wide area controller using modern multi-band power system stabilizer (PSS) is proposed to damp low frequency oscillations (LFOs) in the presence of wind power penetration. The proposed scheme is perfected in two stages. In the first stage, as the online stage, the generation re-dispatch is utilized to improve the damping of LFOs. In the second stage, as the real-time stage, the modern multiband PSSs are tuned in a wide area basis using ambient synchro-phasor measurements. A hybrid subspace identification approach based on estimation of signal parameters via rotational invariance technique (ESPRIT) and robust project approximation subspace tracking (PAST) technique is developed for online estimation of electromechanical modal properties using ambient phasor measurement data. The estimated modal information is then utilized for optimal wide area tuning of multi-band PSSs. Performance of the proposed scheme is then compared with local and global conventional PSSs. The proposed wide area damping controller is simulated over the IEEE-39 Bus test systems.

A Robust Decentralized Wide Area Damping Controller for Wind Generators and FACTS Controllers Considering Load Model Uncertainties

This paper presents a systematic procedure to design a decentralized wide area damping controller for the wind farms and flexible ac transmission system (FACTS) controllers in a smart grid considering uncertainties in the load parameters. The effect of uncertainties in load parameters on damping of inter-area modes of oscillations is investigated through the probability collocation method. A robust $\boldsymbol {H_{\infty }}$ output feedback controller is then designed for the uncertain fuzzy system by satisfying linear matrix inequalities, which are obtained from the original bilinear matrix inequalities derived from the Lyapunov-based stability criterion. The input and output signals for the proposed controller are selected based on a joint observability/controllability index. The input signals are wide area signals obtained from the phasor measurement units and the output signals are fed to wind farm generators and the FACTS controllers. The input signal delay compensation is addressed in this paper. The performance of the controller has been tested on New England 39 bus system developed on real time digital simulator and on a practical large Indian power system under various operating scenarios and faults. Its effectiveness is also compared with a conventional power system stabilizer, local damping controllers, and an existing robust centralized wide area controller designed based on mixed $\boldsymbol {H_{2}} / \boldsymbol {H_{\infty }}$ output feedback synthesis.

Wide-Area Control of Power Networks with Time-Delay

Abstract This work investigates performance and optimal distributed controller design of power networks with time-delay (latency). Performance of the network is measured by the square of the system’s H2-norm. The focus of this paper is on allocating weights to interconnections in order to enhance the performance of the time-delay network and these weights serve as feedback gains in the system. We consider a stylized power system model that inspires our analysis. First, we provide an exact expression for the time-delay margin. Then, we find the performance formula as a function of the spectrum of the Laplacian matrix of the coupling graph, time-delay, and the distributed controller gains. Moreover, we formulate the weight allocation problem as an optimization problem and compare the cases where time-delay is considered and time-delay is neglected in the design process. Lastly, we show that in the presence of time-delay increasing connectivity does not necessarily improve the performance.

A Procedure to Design Fault-Tolerant Wide-Area Damping Controllers

The idea of a smart grid is based on the increased integration of information technologies throughout the power grid. Technologies, such as phasor measurement units, are being deployed to increase the number of wide-area measurements across the bulk power system providing increased awareness of the system operational state. However, from a critical infrastructure perspective, the advanced metering infrastructure introduces a concern: the loss of communication among devices and the power grid. This communication loss may interfere with the wide-area control system performance and adversely affect the power system dynamics. This paper proposes a method based on genetic algorithms for wide-area robust damping controller design considering multiple operation points and loss of communication links related to the input and to the output of the central controller. The method is applied to enhance the damping of the electromechanical oscillations in an IEEE benchmark system: the simplified 14-generator model of the Southeastern Australian power system. The performance of the designed controller is evaluated using modal analysis and non-linear simulations in the time domain. The obtained results demonstrate the effectiveness of the method to design a single centralized controller that provides satisfactory damping to the electromechanical oscillations over several operating points, even when there is a loss of a communication link, thus being robust with respect to is an important aspect of a critical power grid infrastructure.

Robust Decentralized Fixed Order Wide Area Damping Controller

Abstract This paper presents a robust decentralized fixed order wide area damping controller to damp low frequency oscillation in interconnected power systems. The proposed H∞ approach is robust with respect to parametric and dynamic uncertainty. Dynamic uncertainty comes from different system operating points and varying grid topologies. Wide-area control signals have communication links which cause time delay as parametric uncertainty. This H∞ controller is based on loop shaping. The degree of controller is defined by the user. The performance of the controller has been tested on two-areas, four machines system under different uncertainties.

A New Wide Area Intelligent Multi-agent Islanding Detection Method for Implementation in Designed WAMPAC Structure

In this paper, a new multi-agent distributed neural network based islanding detection algorithm is presented. The proposed algorithm is placed in the designed wide area monitoring, control, and protection system (WAMPAC) as one of its applications. Therefore, firstly, the proposed WAMPAC structure and its main parts including WAMS, WACS and WAPS are highlighted that are designed to have a situational awareness to perform both of control and protection actions. To have fast and accurate responses at different contingencies such as WAMS equipment failures or data transmission latency, the multi-agent concept, and neural network algorithm are used at some of the WAMPAC control and protection applications. To show the effectiveness of the designed algorithms, the islanding detection application and its algorithms are described in detail. The proposed method is applied to the IEEE-118 bus power system and its performance is demonstrated at various disturbances. It is shown that the islanding necessity is predicted correctly that helps to perform corrective actions such as controlled islanding execution to avoid wide area blackout. In addition, the algorithm response is increased significantly that contributes to overcome the possible drawbacks of WAMS in large interconnected power systems.

Dynamic performance improvement of New York state power grid with multi‐functional multi‐band power system stabiliser‐based wide‐area control

This study demonstrates the application of a wide-area control scheme based on multi-functional multi-band power system stabilisers (MF-MBPSS) in New York State grid for the purpose of system stability improvement. The aspects of oscillation damping, frequency and voltage closed-loop control are considered. The study describes useful techniques for placing and tuning of MF-MBPSSs based on simulation models and suitable techniques for very large power grids. The application of these concepts is demonstrated on a transient stability model of Eastern Interconnection. Results show a reduction of system frequency nadir during generation outages, significant improvement in damping of post-disturbance swings and capabilities to contribute to long-term voltage stability using only a modest amount of dynamic reactive power resources.

The German experience with integrating photovoltaic systems into the low-voltage grids

Abstract The integration of rooftop photovoltaic systems in the low-voltage distribution grids has become a major international trend, helped by the sinking prices for photovoltaics. One of the key questions revolves around the technical challenges brought about by the grid integration of these decentralized systems. This paper therefore analyzes the substantial practical experiences of ten representative German distribution system operators, who play a leading role in this field. Our findings show that grid expansion measures are primarily undertaken to ensure compliance with the permissible limits for voltage and current. Grid optimization measures represent the most economical initial step and include, for instance, changes in grid structure and wide-area control. Once their potential is maximized, classic grid expansion measures such as laying parallel cables are implemented. In individual cases, the low-voltage grid is reinforced by so-called intelligent operating equipment such as voltage regulators or voltage-regulated local distribution transformers. Moreover, improved grid planning measures lead to a better use of the available low-voltage grid capacity. The practical solutions successfully implemented by German distribution system operators should also prove relevant for other countries that are currently planning the deployment of decentralized renewable energies.

Transient Stability Enhancement of Power Grid With Integrated Wide Area Control of Wind Farms and Synchronous Generators

This paper presents a Wide Area Control (WAC) design to enhance the transient stability of Doubly Fed Induction Generators (DFIG) integrated power grid. The proposed WAC design is based on a nonlinear optimal control algorithm using Reinforcement Learning (RL) and Neural Networks (NNs), which optimizes the closed-loop performance of the wind integrated power grid through Approximate Dynamic Programming (ADP). The aim of the WAC is to estimate the global energy function of the system, independent of the contingency, and derive supplementary damping control to augment the excitation system of synchronous generators and local active and reactive power control of DFIG. The controller objective is evolved from transient energy function terms developed for synchronous generators and wind farms within the framework of a coupled oscillatory system. The theoretical results are verified by conducting simulation studies on the modified IEEE 68-bus system with three aggregated wind farms modeled in electromagnetic transient simulator test-bed. It has been shown that the method improves transient stability of the test system and damps the interarea oscillations faster, including the active and reactive power support from DFIG during grid transient conditions.