Power hardware-in-the-loop setup for power system stability analyses

The authors present a sparse-matrix formulation of the transient energy function method, to analyze the transient stability of large-scale power systems. The proposed formulation preserves the original network structure and avoids network reduction. Consequently, all matrices used in the calculations are very sparse, leading to a significant saving in computational time as compared to the reduced-network-formulation approach. The proposed solution can handle very-large-scale power systems which are beyond the scope of the current reduced-network techniques. The sparse formulation is applied to several practical utility systems of up to 300 generators and 1724 buses. It is concluded that the results obtained demonstrate the superiority and potential of the sparse formulation in the stability analysis of large-scale power systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper deals with the problem of transient stability of large-scale power systems by visting decomposition-aggregation techniques. In this approach based on a priori criteria, the system is decomposed to N-subsystems, the first (N— 1) subsystems described by linear model and the Nthdescribed by nonlinear model. Then each linear subsystem is reduced by aggregation techniques to an equivalent machine. Using this approach the problem of transient stability of large power systems is investigated. An algorithm for calculating the critical switching time based on this technique is proposed. The validity of this method is examined by studying large power systems of 11 machines, and the results obtained using IBM 370/165 digital computer of L.A-A.S. are reported.

With the wide application of power electronic technologies in power system, such as HVDC, new energy power stations and FACTS, the dynamic characteristics of the interconnected power grid have changed dramatically, and the traditional quasi steady model based electromechanical transient program cannot simulate the fast switching process of the power electronic components and its non-fundamental frequency or asymmetry characteristic, which is important to the accuracy of HVDC and FACTS models. Because of the limitation of calculation load and computing speed, traditional electromagnetic transient program cannot replace electromechanical transient program in large-scale power system stability analysis. FEMTP should be redesigned for transient stability analysis of large-scale electronic power system. Then the generator and transmission line’s electromagnetic models are discussed in this paper, and the discussion and simulation shows the adequation of their electromechanical transient model in FEMTP. Afterwards, the implementation of FEMTP was discussed in detail, and the example of China East power grid shows the appropriation of simplified electromechanical models and proposed technologies.

In this paper the problem of transient stability of large-scale power systems is examined through decomposition-aggregation techniques. Two approaches for decomposition and reduction of dynamical models of the systems are described. Then the stability studies for the reduced models are investigated, and some of the results of application of these approaches to a practical system are reported.

Power systems are moving toward a low-carbon or carbon-neutral future where high penetration of renewables is expected.With conventional fossil-fueled synchronous generators in the transmission network being replaced by renewable energy generation which is highly distributed across the entire grid, new challenges are emerging to the control and stability of large-scale power systems.New analysis and control methods are needed for power systems to cope with the ongoing transformation.In the CSEE JPES forum, six leading experts were invited to deliver keynote speeches, and the participating researchers and professionals had extensive exchanges and discussions on the control and stability of power systems.Specifically, potential changes and challenges of power systems with high penetration of renewable energy generation were introduced and explained, and advanced control methods were proposed and analyzed for the transient stability enhancement of power grids.

Time delay is prejudicial to power system stability and generally worsens the performance of control system. In this paper, the approaches for stability analysis and stabilization of a power system consisting of time-varying delay are established. The paper starts with modeling of the power system according to time-delay differential algebraic equations. An Integral Quadratic Constraints (IQC) method is constructed to guarantee the stability of proposed feedback controller. The frequency-domain IQC and time-domain dissipation inequality are effectively combined to perform stability analysis and stabilization of power system considering time delays, without complex numerical computation. A 2-area 4-machine system, an IEEE ten-machine thirty nine-bus system and a WECC 179-bus system are employed to support the stability criteria and IQC method. The simulation results indicate that the combined methods effectively damp the oscillation and improve the performance.

Fast electric vehicle(EV) charging stations have become one of the fastest-growing penetrated power electronics (PE) interfaced loads to the electric power system. The lack of accurate model of the fast EV charger in transient stability (TS) simulation tools limits the effectiveness of power system dynamic performance evaluation and stability analysis. In this paper, The electromechanical model of a fast EV charging unit is proposed, which is suitable for large-scale power system dynamic analysis in TS simulators. The EV charger model is simplified to guarantee a balance between model accuracy and simplicity. The validity of the proposed model has been demonstrated by a comparative study with the benchmark model created in PSCAD/EMTDC.

In this paper, the H∞ robust control technique is presented to design a power system stabilizer. First, the H∞ standard problem is expressed and then, the modeling and stability analysis of power systems are studied. Finally, a H∞ power system stabilizer is designed and the simulation results are discussed.

Direct stability analysis using an energy function has recently been widely used for angular and voltage stability analysis in electric power systems. Considerable efforts have concentrated on seeking energy functions for lossy power systems, accomplished only for the simple two-bus system. A new approach is presented to derive an energy function by using the complex integral of bus current equations with respect to bus voltages. Under an assumption that all transmission lines have a uniform R/X ratio, it is shown that the energy function can be developed for multimachine power systems with losses. The proposed energy function is tested on sample systems by comparing the time simulation method, which shows the validity of the proposed method.

A new decomposition-aggregation approach is developed to perform transient stability analysis of an N-machine power system with a speed governor. The system decomposition is performed so that every subsystem includes four machines, instead of only two or three machines as considered in other work. The system model is derived and decomposed into (N − 1)/3 11th-order interconnected subsystems considering transfer conductances, nonuniform mechanical damping, electromagnetic damping and speed governor action. Each of these subsystems is decomposed into a free subsystem containing 12 nonlinearities and interconnections. A square aggregation matrix of order (N − 1)/3 is obtained instead of orders N and (N + 1)/2 for the pair-wise and triple-wise decompositions, respectively. The approach is applied to a 10-machine power system and an estimate for the system asymptotic stability domain is determined. System transient stability computations are carried out considering a three-phase short circuit fault, with successful reclosure, near a system bus or a sudden loss of one of the system loads. The approach is used to determine a reclosure time for the faulted line and a reconnection time for the lost load required for the system to regain its prefault (normal) conditions. The approach developed is suitable and can be easily used for stability analysis of power systems (the number of machines may be more than 10). The developed approach can also reduce the conservativeness of the decomposition-aggregation method.

The transient stability analysis of power systems can be described by differential and algebraic equations, and due to the increased speed with parallel computing techniques, use of the waveform relaxation method to solve these equations has attracted much attention. In order to enhance the calculation speed of the waveform relaxation method, it is of prime importance to reduce the required number of iterations for each time window. To this end, an initialization and preconditioning techniques have been proposed to improve convergence of the iterative procedure. In this paper, in order to enhance convergence, we developed a new global initialization technique that consists of linear analysis and a preconditioning technique. Specifically, global initialization is the result of the repeated application of conventional initialization and preconditioning techniques before each of the nonlinear iterative procedures, and then using linear analysis to determine the interaction between the CPUs. By calculating the initial waveforms more accurately, it is expected that additional speedup can be achieved by reducing the required number of iterations necessary for convergence of the nonlinear analysis.

Power systems are being operated close to their voltage security limit which makes their reliable operation more challenging. Voltage stability has been a major problem faced by utilities now a days. Many blackout have been reported around the world related to voltage instability problem. Many voltage stability analysis methods have been presented up till now. Here artificial neural network based approach for voltage stability analysis of power system is presented. Voltage stability analysis of power system has been done in terms of voltage stability margin. Voltage stability margin is calculated by estimating distance from current operating point to maximum voltage stability point according to loading parameter. Principal Component Analysis is an efficient feature selection method used here to find few input variables required to estimate voltage stability margin with sufficient accuracy and execution speed. Major drawback of previously published work is they need to train new neural network whenever change in system topology occur which is very time consuming process. Therefor in this paper single ANN has been prepared for estimating VSM for several system configuration. Feed forward neural network and radial basis function neural network have been used for voltage stability analysis of power system. The final result indicate that proposed method provide an efficient and compact ANN model for different system configuration as well as base case operating condition with lowest possible input required.

Power systems with high renewable energy sources: A review of inertia and frequency control strategies over time

Measurement-based investigation of inter- and intra-area effects of wind power plant integration

This paper presents the protective relay settings of tie line tripping and design of load-shedding scheme for an integrated steelmaking industrial power system to ensure system stability after a severe fault contingency on an external utility power network. The transient stability analysis of the industrial power system with the equivalent external Taipower system has been executed for an actual fault contingency in 2005. The mathematical models of 13 cogeneration units in the plant and several large generators of a nearby Taipower thermal plant are included in the computer simulation to solve the system transient response for the fault contingency to verify the accuracy of the models used. To prevent tripping of critical loads due to an external fault contingency, the undervoltage and under/overfrequency relays with proper settings are applied for the tripping of external and internal tie lines. To restore system stability of the industrial power system for the islanding operation after tie line tripping, load shedding is designed to disconnect a proper amount of noncritical loads by considering the governor response and protective constraints of cogeneration units. According to the transient stability analysis of the industrial power system with the proposed protective relay settings and load-shedding scheme, it is found that the voltage sag and oscillation problem caused by fault contingency in the external Taipower system can be mitigated if the tie line tripping is executed in time to prevent the shutdown of critical loads and tripping of cogeneration units.