Power System Dynamic Performance Research Articles

Economic flexible AC transmission system devices placement/sizing with (N-1) contingency using genetic algorithm

<span>The rise in demand for electricity and the high cost of constructing new power networks reckons optimal utilization of electric power overloading and excessive power transfer along transmission lines, high losses, voltage instability, poor power quality, reliability issues. Flexible AC transmission system (FACTS) boosts the static and dynamic performance of power systems. Although efficient power transmission by improving power quality and voltage profile enhancement is controlled using the FACTS devices the placement, types, and sizing are important parameters to be optimized for the power system. This paper develops the economic multiple FACT placements and sizing solution during N-1 contingency conditions. Placement and sizing being the stochastic problem meta-heuristic algorithm genetic algorithm (GA) is used and applied on the standard IEEE 9 bus system. MATLAB-based simulation is developed for economic placement of multiple FACTS and single FACTS devices in different scenarios (without FACTS devices, with single FACTS devices, and with multiple FACTS devices). Both static VAR compensators (SVC) and thyristor-controlled series capacitors (TCSC) are used (either single or multiple) to optimize the transmission loss and total cost. The results show that transmission loss and cost reduction with 70% compensation is working better with about 0.1 MW lesser loss in many cases.</span>

Modeling and simulation of stochastic transients in power systems based on frequency shifting theory

The increasing uncertainties in power systems have brought non-negligible influences on the dynamic behaviors. An accurate and efficient simulation method considering the effects of stochastic disturbances is of critical importance for the analysis of the dynamic performance of power systems. In this paper, a methodology for the simulation of stochastic transients in power systems is developed based on frequency shifting theory. The stochastic differential equations describing the stochastic process of parameter migration are represented through analytic signals. The frequency shifting operation is introduced. The Fourier spectra of analytic signals are shifted to reduce their maximum frequency contents, thereby permitting a larger time-step in time-domain simulation in accordance with Shannon’s sampling theory. Through the trapezoidal Milstein scheme, the stochastic differential equations with shifted analytic signals are discretized. Branch companion models that process analytic signals for the simulation of stochastic transients are formulated. The numerical properties of branch models are further examined. The analysis of test cases demonstrates that the proposed method can be used to represent stochastic transients caused by parameter migrations accurately and efficiently.

Design, testing and commissioning of power system stabilizer in gas-fired generating unit on the Hong Kong electric power system

With the aim to improve power system dynamic performance, power system stabilizers (PSS) have been adopted in the Hongkong Electric Power System since 1990s, which has made a significant contribution to system dynamic stability by enhancing the system damping against system disturbance of low frequency power oscillation. Upon the satisfactory performance of PSS adopted in generating units in the past, the Hongkong Electric Company Limited (HK Electric) continues to employ PSS to gas-fired generating units in Lamma Power Station Extension (LMX). A gas-fired generating unit, L10, equipped with PSS, was commissioned in February 2020. Being the manufacturer of Automatic Voltage Regulator (AVR) and PSS of L10, Mitsubishi Electric Corporation (MELCO) partnered with HK Electric for the design, testing and commissioning of the PSS. This paper presents the design and practical experience in testing and commissioning of PSS installed in L10.

Guest Editorial: Grid‐forming converters placement and utilisation to enhance transmission and distribution performances under high penetration of inverter‐based resources

Power systems around the world are rapidly transitioning to much higher shares of inverter-based resources (IBRs) with few synchronous generators remaining online. IBRs and synchronous generators have fundamentally different dynamic performance characteristics resulting in a difference in the overall power system dynamic performance. IBRs are generally more flexible and controllable than synchronous generators; however, at the same time they exhibit significantly more complex control systems. Furthermore, new and emerging capabilities are being developed progressively and in particular the so-called grid-forming inverters (GFM). GFM offer several new capabilities not previously possible with conventional grid-following inverters (GFL). However, they are not well understood currently when applied in a mega scale and moving forward when they will likely take over the role synchronous generators have been performing for several decades as the workhorse of system security support. Key questions currently in the technical community include the extent to which GFM shall be similar or different to each of the synchronous machines and conventional GFL, and how various control strategies can assist in maximising the grid support capabilities sought and minimise or ideally eliminate any adverse impacts. The objective of this special issue is to provide insights into some of these unknowns.

Power System Dynamic Performance Analysis Based on Frequency Control by Proton Exchange Membrane Electrolyzers

Intermittency of renewable energy sources can cause greater frequency variations and with no other intervention, the generation reserve capacity of a power system needs to be significantly increased to ensure frequency stability, resulting in increased costs. With appropriate control actions, proton exchange membrane electrolyzers (PEMELs) can be used to regulate power system frequency stability, but their adjustable demand-side response capabilities need to be investigated. This article first introduces the dynamic characteristics of the PEMEL stack to examine the impact of incorporating the control loop of the PEMEL stack into a single-area power system populated with solar photovoltaic units, taking into account the communication time lag during the control signal transfer process. The dynamic performance of the proposed power system and steady-state errors are then analyzed demonstrating contribution of the PEMEL stack to frequency regulation services effectively. Moreover, the frequency stability of the power system with and without the PEMEL stack is assessed to illustrate improvement in the stability and robustness of the power system during system uncertainties. Numerical studies are used to validate the efficiency of the presented models and approaches.

Design of a Robust Coordinated Power Oscillation Damper for Use with Large-Scale Wind Energy System Connected to a Multimachine Power System

Many researchers have proposed the use of the doubly fed induction generator (DFIG)-based wind energy conversion system (WECS) in the enhancement of power system dynamic performance. However, the application of a coordinated design strategy to coordinate the DFIG and other synchronous generators in the system for the improvement of small-signal stability is rarely researched. What is more, the use of strategy with a low computational burden to enhance the robustness of coordinated strategy for the design of damping controllers is rare. A coordinated strategy in designing multiple damping controllers, including DFIG-based power oscillation damper (POD) and power system stabilizers (PSSs), is proposed in this paper. A modal participation factor is employed to find out the most effective feedback signal for the POD. A hybrid optimization algorithm based on the grey wolf optimizer (GWO) and particle swarm optimizer (PSO) is applied for parameter optimization of the damping controllers considering a multiobjective eigenvalue-based optimization problem. Modal analysis is carried out on the widely studied two-area four-generator benchmark power system to establish the theoretical viability of the proposed approach. Probabilistic analysis established on Monte Carlo simulation is then carried out to prove the robustness of the coordinated design strategy under diverse operating conditions. Nonlinear time-domain simulations are used to verify the damping performance and robustness of the proposed strategy under different operating scenarios.

New EiC, Same Mission: Serving Energy Professionals and PES [Editors’ Voice

Thirty-nine years ago, I joined IEEE as a Student Member of the Quebec Chapter, with control systems as my area of interest. When I attended my very first IEEE Power & Energy Society (PES) Winter Meeting in 1990 in Atlanta as a utility research engineer, I met legends of industry, like Prabha Kundur and Charles Concordia, and famous professors whom I admired. My immediate desire was to follow in their steps. During my early career, I was concerned about developing impactful technologies and writing research papers of archival value. To this aim, I engaged as a volunteer in various IEEE technical activities, mainly within the Electric Machinery and Power System Dynamic Performance Committees. This professional development led me to some consequential contributions to electric machinery standards and power grid control and protection systems. I was lucky enough to see some of them adopted and implemented in my own Hydro-Quebec, the public utility of the Province of Quebec in Canada, and elsewhere. This drive to design, build, implement, and report to peers was my main source of motivation during most of my career.

WAMS-based two-level robust detection methodology of power system events

With the advance of Wide-Area Measurement Systems (WAMS), power system operators have direct access to a large amount of data with valuable information about the power system dynamic performance. As a result, there is a clear need for new data-driven methodologies capable of extracting relevant information from this collected data. One of the key challenges is correctly detecting power system disturbances to avoid false alarms during real-time operation as well as off-line disturbance analysis. This paper proposes a two-level robust event detection methodology aiming to reduce false disturbance detection (false positives/alarms) and validate true events. The methodology is divided into two-levels: (i) signal processing analysis (ii) deep neural network (DNN) classification. In the first level, we apply a widely used spectral analysis based on the Discrete Wavelet Transform (DWT) to event detection. In the second level, the events detected by the DWT are processed by a DNN to check if they are real events or false alarms. Finally, the proposed methodology is evaluated using real synchrophasor event records from the Brazilian Interconnected Power System (BIPS).

Curvature-Based Control for Low-Inertia Systems

This letter proposes a simple and inexpensive control of distributed energy resources aimed at improving the power system dynamic performance. The rationale behind the proposed control relies on a recent interpretation of the frequency in the differential geometry framework. A comparison with well-established controls in terms of eigensensitivity and time-domain performance is carried out to show the effectiveness of the proposed control.

Impacts of integration of very large‐scale photovoltaic power plants on rotor angle and frequency stability of power system

The increase in penetration of large-scale renewable generation significantly affects power system characteristics. Thus, it is necessary to assess the steady state and dynamic performance of a power system for different installing scenarios of renewable power plants such as photovoltaic (PV) ones. The paper specifically investigates the impacts of very large-scale photovoltaic (VLS-PV) generation on the power system dynamic performance including rotor-angle and frequency stabilities. For this purpose, a detailed equivalent dynamic model for a multi-unit VLS-PV system and corresponding controllers are developed. The paper also proposes a comprehensive set of replacement scenarios comprising different PV penetration, location, and voltage control strategies as well as simulating various large disturbances. To investigate the impacts of VLS-PV generation on dynamic system performance, a study framework for frequency and rotor-angle stability involving the modal and transient analysis is presented as well. By using the VLS-PV detailed model along with other dynamic components of a power system such as synchronous generators, automatic voltage regulators (AVRs), and governors, the stabilities studying instructions are employed for the IEEE 39-bus and 118-bus test systems.

Power system modelling as stochastic functional hybrid differential‐algebraic equations

This paper presents the software tools developed for the research project Advanced Modelling for Power System Analysis and Simulation (AMPSAS) funded by Science Foundation Ireland from 2016 to 2021. The main objective of AMPSAS was the development of novel analytical and computational tools to understand, efficiently design, and optimise ever-changing modern power systems and smart grids, through model-based approaches. In particular, the paper discusses (i) stochastic differential equations for modelling power systems, which are subject to large stochastic perturbations (e.g. wind and solar generation); (ii) the effect of controller and modelling imperfections, for example, delays, discontinuities, and digital signals, on both local and area-wide regulators in power systems; and (iii) the stability analysis and dynamic performance of power systems modelled through stochastic, delay and hybrid implicit differential-algebraic equations. The software tool developed during the execution of AMPSAS integrates areas of applied mathematics, automatic control, and computer science. Several implementation features and open challenges of this software tool are also discussed in the paper. A variety of examples that illustrates the features of this software tool are based on a dynamic model of the all-island Irish transmission system.

Optimal Equilibrium Selection of Price-maker Agents in Performance-based Regulation Market

This paper analyzes the oligopolistic equilibria of multiple price-maker agents in performance-based regulation (PBR) markets. In these markets, there are price-maker agents representing some frequency regulation (FR) providers and a number of independent price-taker FR providers. A model of equilibrium problem with equilibrium constraints (EPECs) is employed in this paper to study the equilibria of a PBR market in the presence of price-maker agents and price-taker FR providers. Due to the incorporation of the FR providers' dynamics, the proposed model is reformulated as a mixed-integer linear programming (MILP) problem over innovative mathematical techniques. An optimal equilibrium point is also selected for the market, where none of the agents is the unique deviator and the dynamic performance of power system is improved simultaneously. The effectiveness of the proposed optimal equilibrium point is evaluated by comparing the outputs with the conventional optimal dispatches of the FR providers.

Uncertainty Evaluation Algorithm in Power System Dynamic Analysis With Correlated Renewable Energy Sources

The variation and uncertainty of renewable energy potentially impact power system stability. This article proposes an efficient uncertainty evaluation algorithm to evaluate the influence of renewable energy uncertainty on power system dynamic performance. This algorithm applies probabilistic collocation method (PCM), which greatly reduces the simulation burden without compromising the result accuracy, to approximate the dynamic simulation results. The proposed algorithm also considers the correlation among adjacent renewable generators by using the Copula function, which is suitable to model nonlinear correlations. Additionally, this article extends the utilization of PCM. The actual historical data of renewable generation productions can be utilized directly, and kernel density estimation (KDE) is used to capture the nonparametric distribution of renewable generation production. To improve the accuracy of the approximation results, the proposed method adopts K-means clustering technique to select the approximation samples of input variables. The proposed probabilistic dynamic simulation algorithm is compared with Monte Carlo simulations (MCS) with the probabilistic results on the IEEE 39-bus system with multiple renewable generators, and the accuracy and efficiency of the proposed algorithm are validated.

Performance evaluation of different structures of power system stabilizers

The electric power from the system should be reliable and economical for consumer’s equipment satisfaction. An electric power system consists of many generators, transformers, transmission lines, loads, etc. For the power system network, dynamic performance and stability are important. The system is lost its stability by some disturbances i.e., load variations, generator failure, prime mover failure, transmission line outage, etc. Whenever load variations in the system, generator rotor speed will vary, means oscillations in the rotor speed, which is deviating from rated speed. The excitation system will control the generator rated line voltage. When fault occurs at any equipment in the system, the system will unstable. If fault occurs at generator, the generator oscillates. To reduce the oscillations and to make the system stable used power system stabilizers (PSS’s). Here, three types of PSS’s are used i.e., PSS1B, PSS2B, PSS4B. Comparisons of three PSS’s are on the multi machine system under some disturbance. From the observations, concluding that PSS4B is quickly control the oscillations in the physical parameters of machine in the system than other power system stabilizers.

Synergy of adaptive super-twisting method (ASTM) and game-theory algorithm (GTA) for dynamic stability improvement of interconnected grids

In this research work, a proposed technique of adaptive super-twisting method (ASTM) and game-theory algorithm (GTA) is presented. The proposed technique is applied to improve the dynamic stability of UPFC-based tidal energy resource. The impact of UPFC-based tidal energy resource on the power network is significantly recognized to support the demands supply and to enhance the dynamic performance. UPFC is able to control and enhance the power flow, voltage profile, power angle profile, and transmission lines loadability. The proposed technique has been optimally tuned to control the operational parameters of UPFC-based tidal energy resource. Both scenarios of single machine connected to infinite-bus grid, and multi-machine system are considered. The dynamic modelling of underlined system is done by d–q axis reference modelling. The analysis of steady-state stability is represented by the dynamic response specifications with stability discussion to evaluate the system performance. The simulations, including modelling, analysis and results, are carried out to confirm the entire stability of underlined systems. It has been confirmed the superb characteristics of proposed technique on interconnected UPFC-based tidal energy resource to power systems. The results of concerned scenarios have been emphasized that the proposed technique outperforms other well-established techniques. It is consolidated that UPFC-based tidal energy resource with proposed technique achieves significant performance and strengthened response. Therefore, the proposed solution can be offered as a favourable technique for enhancing the dynamic performance of power systems.

A Method Based on Linear Matrix Inequalities to Design a Wide-Area Damping Controller Resilient to Permanent Communication Failures

One of the main advantages of the wide-area measurement systems in the small-signal stability of the electric power systems is to use synchrophasor data from the phasor measurement units (PMUs) for the operation of a central controller, or wide-area damping controller (WADC), to improve the damping ratio of the low-frequency oscillation modes. However, cyber-attacks in the PMU measurements can lead to permanent communication failure of the WADC channels and, therefore, the dynamic performance of the power system can be damaged. Besides, the signals for this controller are from different locations and thus they present time delays that can also damage the power system dynamic performance. This article introduces a method based on linear matrix inequalities to design a WADC robust to power system operation uncertainties, time-delay uncertainties, and permanent communication failure of the WADC channels. The proposed method was applied and evaluated in the IEEE 68-bus system by modal analysis and time-domain nonlinear simulations.

Test Systems for Voltage Stability Studies

This paper describes the two test systems for voltage stability studies set up by the IEEE PES Task Force on “Test Systems for Voltage Stability Analysis and Security Assessment” under the auspices of the Power System Stability Subcommittee of the Power System Dynamic Performance Committee. These systems are based on previous test systems, making them more representative of voltage stability constraints. A set of representative results are provided for both systems, with emphasis on dynamic simulation. They illustrate various aspects such as long-term dynamics, voltage security assessment, real-time detection, and corrective control of instabilities. The value for educators, researchers and practitioners are emphasized.

ANN-Based Relaying Algorithm for Protection of SVC- Compensated AC Transmission Line and Criticality Analysis of a Digital Relay

Background:The Static VAR Compensator (SVC) has the capability of improving reliability, operation and control of the transmission system thereby improving the dynamic performance of power system. SVC is a widely used shunt FACTS device, which is an important tool for the reactive power compensation in high voltage AC transmission systems. The transmission lines compensated with the SVC may experience faults and hence need a protection system against the damage caused by these faults as well as provide the uninterrupted supply of power.Methods:The research work reported in the paper is a successful attempt to reduce the time to detect faults on a SVC-compensated transmission line to less than quarter of a cycle. The relay algorithm involves two ANNs, one for detection and the other for classification of faults, including the identification of the faulted phase/phases. RMS (Root Mean Square) values of line voltages and ratios of sequence components of line currents are used as inputs to the ANNs. Extensive training and testing of the two ANNs have been carried out using the data generated by simulating an SVC-compensated transmission line in PSCAD at a signal sampling frequency of 1 kHz. Back-propagation method has been used for the training and testing. Also the criticality analysis of the existing relay and the modified relay has been done using three fault tree importance measures i.e., Fussell-Vesely (FV) Importance, Risk Achievement Worth (RAW) and Risk Reduction Worth (RRW).Results:It is found that the relay detects any type of fault occurring anywhere on the line with 100% accuracy within a short time of 4 ms. It also classifies the type of the fault and indicates the faulted phase or phases, as the case may be, with 100% accuracy within 15 ms, that is well before a circuit breaker can clear the fault. As demonstrated, fault detection and classification by the use of ANNs is reliable and accurate when a large data set is available for training. The results from the criticality analysis show that the criticality ranking varies in both the designs (existing relay and the existing modified relay) and the ranking of the improved measurement system in the modified relay changes from 2 to 4.Conclusion:A relaying algorithm is proposed for the protection of transmission line compensated with Static Var Compensator (SVC) and criticality ranking of different failure modes of a digital relay is carried out. The proposed scheme has significant advantages over more traditional relaying algorithms. It is suitable for high resistance faults and is not affected by the inception angle nor by the location of fault.

A Library of Second-Order Models for Synchronous Machines

This article presents a library of second-order models for synchronous machines that can be utilized in power system dynamic performance analysis and control design. The models have a similar structure to that of the so-called classical model in that they consist of two dynamic states, the power angle and the angular speed. However, unlike the classical model, they find applications beyond first swing stability analysis, i.e., they can be utilized for multi-swing transient stability analysis. The models are developed through a systematic reduction of a nineteenth-order model using singular perturbation techniques. They are validated by comparing their response with that of the high-order model from which they were derived, as well as that of other synchronous machine models existing in the literature, such as the so-called two-axis model and the so-called one-axis model.

Many-Objective Robust Optimization for Dynamic VAR Planning to Enhance Voltage Stability of a Wind-Energy Power System

Growing integration of wind power and increasing use of induction motor loads dramatically affect a power system's dynamic performance. To address the challenges, this paper proposes a robust dynamic VAR planning method to enhance the voltage stability of wind energy power systems under uncertainty. Firstly, two indices are developed to evaluate the steady-state and the short-term voltage stability of the system. Then, a robustness index is proposed to quantitatively evaluate the robust optimality of the solutions, considering the uncertainties from wind power output and STATCOMs initial state before a contingency. Four objectives are optimized simultaneously: 1) total planning cost, 2) short-term voltage stability index, 3) steady-state voltage stability index, and 4) robustness of the solutions. Finally, an Adaptive Non-dominated Sorting Genetic Algorithm-III based on Latin Hypercube Sampling (A-NSGA-III-LHS)is designed to solve this many-objective optimization problem with 3 improvements over the standard NSGA-III: 1) adaptive mutation rate, 2) Differential Evolution operator, 3) Latin Hypercube Sampling based initial population generation. The proposed method is tested on the New England 39-bus system with an industry-standard complex load model, showing high robust optimality and computational efficiency over conventional methods.