Power System Dynamic Model Research Articles

Foreign aid via 3-Party Covenant Financings of capital-intensive infrastructure

Purpose The purpose of this article is to analyse electricity supply in the Solomon Islands face extraordinarily expensive electricity tariffs – currently set at 96 c/kWh – making them amongst the highest in the world. Power is supplied by a fleet of diesel generators reliant on imported liquid fuels. In this article, the authors model the 14,100 kW power system on the island of Guadalcanal and demonstrate that by investing in a combination of hydroelectric and solar photovoltaic generating capacity, power system costs and reliability can be improved marginally. However, when the authors model a 3-Party Covenant (3PC) Financing structure involving a credit wrap by the Commonwealth of Australia, electricity production costs fall by 50 per cent, thus resulting in meaningful increases in consumer welfare. Design/methodology/approach This study’s approach uses an integrated levelised cost of electricity model and dynamic partial equilibrium power system model. Doing so enables the authors to quickly analyse the rich blend of fixed, variable and sunk costs of generating technology options. The authors also focus on the cost of capital that is likely to be achieved under various policy settings. Findings The authors find that a 3PC Financing policy can substantially reduce the production costs associated with capital-intensive power projects in an unrated sovereign nation. Such a policy and associated prescriptions are not specific to the Solomon Islands or power generation. The conceptual framework and associated financial logic that underpins the initiative can be generalised to other “user pays” infrastructure projects and to other developing nations. The broad applicability of 3PC financing means that it is not country specific, project specific or asset class specific. Research Limitations/implications It is important to note that the analysis in this paper has a number of limitations in that the authors do not deal with rural electrification or distribution network costs. The focus of this paper is to identify policy interventions that are capable of making profound changes to the cost and the reliability of wholesale electricity production. Originality/value The focus of this paper is to identify a policy intervention capable of making profound changes to the cost and the reliability of wholesale electricity production. While there is nothing novel associated with a 3PC Financing per se, the authors are unaware of its direct use as a form of delivering foreign aid. A 3PC Financing has the effect of shifting the source of aid funding from fiscal account surplus/deficit (i.e. cash outlays) to balance sheet (i.e. credit wrap). However, this is not a “magic pudding” – 3PC Financing creates an asset-backed contingent liability and will have the effect of reducing the donor country’s own debt capacity by a commensurate amount, holding the nation’s credit rating constant.

The Effect of FRT Behavior of VSC-HVDC-Connected Offshore Wind Power Plants on AC/DC System Dynamics

Future power systems will contain more converter-based generation, among which are the voltage-source converter–high-voltage direct-current (VSC-HVDC)-connected offshore wind power plants (WPP). Their interaction with the onshore system influences power system dynamics in the transient stability timeframe. The respective protection and control methods which cause this interaction must be taken into account in grid-integration studies performed today. This paper gives insight into the effect of typically required fault ridethrough (FRT) and post-FRT measures of VSC-HVDC-connected offshore WPPs on the combined ac and HVDC system dynamics. Several important sensitivities are addressed, among which are: 1) FRT implementation, 2) the postfault active power-recovery rates, 3) the ac network dynamic characteristics, and 4) the HVDC topology. The analysis is first performed as a proof of concept on a small benchmark system, and subsequently generalized to a realistic dynamic model of the future Northwestern European power system. The results of this paper can be used as a reference for understanding the effects of large-scale VSC-HVDC-connected offshore WPPs on the stability of the onshore interconnected power systems.

Assess the Modeling Effects of PSS and Governor on Voltage Stability of Power System

In this paper, we assess the modeling effects of PSS and governor on voltage stability of power system by applied accurate dynamic model of power system. This model consists of the detailed models for the synchronous machines, automatic voltage regulators (AVRs), Prime mover and speed governor, Power system stabilizer (PSS) is used for voltage stability assessment. Voltage stability assessment is done by calculation of voltage stability margin (VSM). The VSM is an index that describes distance between the current operation state point and the maximum voltage stability limit point. The IEEE 14-bus standard test system is used for simulation. The obtained results from preformed simulation show effects of PSS and governor on voltage stability.

Improvement of Power System Performance Using Fuzzy Logic Based Interline Power Flow Controller [IPFC

In this paper, the nonlinear dynamic model of a multi machine power system incorporated with Interline Power Flow Controller [IPFC] has been developed for improvement in damping of power system oscillations and transient stability. The IPFC performance is tested with PI controllers in comparison with fuzzy logic based controller under healthy and abnormal operating conditions. The IPFC fuzzy controller is design to coordinate two control inputs: change in voltage and change in capacitor voltage to improve the transient stability of the multimachine system. The Interline Power Flow Controller [IPFC] with fuzzy logic controller is designed with simple fuzzy rules to coordinate the additional damping signal. The proposed controller for IPFC is able to achieve improved designed performance of the power system. Digital simulations are carried out in MATLAB environment.

Real Time Dispatch Training Simulator based on TRIS/DMES ELEKTROSYSTEM

Abstract: This article introduces the Dispatch Training Simulator for transmission and distribution system operators. The DTS is a combination of real time control system TRIS developed by ELEKTROSYSTEM a.s. and a verified analytical simulation engine called DMES (Dynamic Model of Electric power System).

On the steady-state behavior of a nonlinear power network model

Abstract: In this paper, we consider a dynamic model of a three-phase power system including nonlinear generator dynamics and transmission line dynamics. We derive conditions under which the power system admits a steady-state behavior characterized by an operation of the grid at a synchronous frequency as well as a power balance for each single device. Based on this, we specify a set on which the dynamics of the power grid match the desired steady-state behavior and show that this set is control-invariant if and only if the control inputs to the generators are constant. Moreover, we constructively obtain network balance equations typically encountered in power flow analysis and subsequently show that the power system can be operated at the desired steady-state if and only if the network balance equations can be solved.

Model Free Backstepping Control for Marine Power Systems

In order to retrain chaotic oscillation of marine power systems which are excited by periodic electromagnetism perturbation, in this paper, a novel model free backstepping control methods are designed. First, the dynamic model of marine power system is established based on the two parallel nonlinear model. Then, extended state observer (ESO) is de- signed to estimate the velocity signal and unknown function. Next, the model free backstepping controller is proposed based on the ESO. Finally, simulation results demonstrate the proposed model free control algorithm can quickly retrain chaotic oscillation. And it shows the proposed control method is effectiveness and potential.

Sensitivity analysis of stack power uncertainty in a PEMFC-based powertrain for aircraft application

Experimental data concerning the reliability of fuel cell systems (FCS) in aviation are still unavailable to technical community, while assessing reliability of a component or a whole system represents a fundamental aspect that allows a new technology to be introduced in a high safety system such as an aircraft. The main aim of this paper is to show a method to estimate the reliability of an aircraft power system based on a hydrogen fuel cell, mainly for design purposes. The method is based on a high-order adaptive response surface technique, coupled with a dynamic model of the aircraft power system, and it is applied to the failure event represented by an incorrect power supply due to the failure of sensors of the control system of the powertrain. The most important advantage of the proposed method is the low computational effort it requires. The result is a ranking of the most critical sensors to be considered in the design phase of the power system and demonstrate that accurate temperature sensors and sensor calibration are of dramatic importance for the control of the stack power, in case of powertrain based on PEM fuel cell systems.

Automatic generation control of power system using a novel quasi-oppositional harmony search algorithm

Abstract The present work approaches a novel quasi-oppositional harmony search (QOHS) algorithm, as an optimization technique, for its optimum performance in the subject area of automatic generation control (AGC) of power system. The proposed QOHS algorithm is applied with an aim to converge rapidly towards the optimal solution(s) that houses both the characters of two guesses, i.e. opposite-point and quasi-opposite point. The area of concern of this study is to discuss the multi-objective problems of an interconnected power system for the benefits of AGC. The proposed QOHS algorithm is, individually, applied to single-area, precede to two-area considering the non-linearity effects of governor dead band and generation rate constraint and, finally, extended to four-area power system showing the consequences of multiple load disturbances. A case of robustness and stability analysis are also investigated for the studied two-area power system model. The control strategy, for the dynamic power system model, is based on area control error. The simplicity of the structure and acceptability responses of the well-known proportional–integral–derivative controller enforces to implement as a controller in this work. The comparative evaluation of the proposed QOHS algorithm is carried out by the way of comparing the dynamic performances of the studied power system model with those offered by other algorithms reported in the recent state-of-the-art literature. The simulation works, presented in the paper, reveal that the proposed QOHS algorithm may be effectively utilized for the purpose of AGC study of power system having varying degrees of complexities and non-linearities. Moreover, the proposed QOHS based control strategy adopted in this work provides a robust and stable speed control mechanism.

Dynamic model of a pumping kite power system

Converting the traction power of kites into electricity can be a low cost solution for wind energy. Reliable control of both trajectory and tether reeling is crucial. The present study proposes a modelling framework describing the dynamic behaviour of the interconnected system components, suitable for design and optimization of the control systems. The wing, bridle, airborne control unit and tether are represented as a particle system using spring-damper elements to describe their mechanical properties. Two kite models are proposed: a point mass model and a four point model. Reeling of the tether is modelled by varying the lengths of constituent tether elements. Dynamic behaviour of the ground station is included. The framework is validated by combining it with the automatic control system used for the operation of a kite power system demonstrator. The simulation results show that the point mass model can be adjusted to match the measured behaviour during a pumping cycle. The four point model can better predict the influence of gravity and inertia on the steering response and remains stable also at low tether forces. Compared to simple one point models, the proposed framework is more accurate and robust while allowing real-time simulations of the complete system.

Approximate Bisimulation-Based Reduction of Power System Dynamic Models

In this paper we propose approximate bisimulation relations and functions for reduction of power system dynamic models in differential-algebraic (descriptor) form. The full-size dynamic model is obtained by linearization of the nonlinear transient stability model. We generalize theoretical results on approximate bisimulation relations and bisimulation functions, originally derived for a class of constrained linear systems, to linear systems in descriptor form. An algorithm for transient stability assessment is proposed and used to determine whether the power system is able to maintain the synchronism after a large disturbance. Two benchmark power systems are used to illustrate the proposed algorithm and to evaluate the applicability of approximate bisimulation relations and bisimulation functions for reduction of the power system dynamic models.

Multivariable control with grid objectives of an HVDC link embedded in a large-scale AC grid

Abstract The HVDC links are increasingly used not only to interconnect asynchronous AC systems but are also embedded into a same meshed AC power system. Thanks to its speed and flexibility, the HVDC technology is able to provide transmission system advantages as transfer capacity enhancement and power flow control. In addition, studies have shown that the way of controlling the HVDC converters impacts the stability of the AC system. This can be particularly exploited to enhance the dynamic power system performances during transients. In this paper a robust multivariable control design for HVDC link converters is proposed. It is based on the coordination of the control actions of the HVDC converters and the use of a control model which takes into account the dynamics that mostly impact stability of the neighbor zone of the HVDC link. This new methodology was used to synthesize the controller for an actual grid 1000 MW HVDC link reinforcement project called “Midi-Provence” in the southern part of the French grid. The synthesis, implementation and validation processes are presented in detail. The new controller is tested in comparison with the standard vector control. A large-scale dynamic model of the whole European power system, currently used and updated by the European TSO’s for the interconnection studies has been used with Eurostag simulation software.

A measurement-based power system model for dynamic response estimation and instability warning

Traditional power system dynamic models are very complex due to the intricacy of power system networks and can be inaccurate for control because of the amount of details needed and the fact that the grid topology changes all the time. With the fast deployment of a large number of phasor measurement units (PMUs) in the transmission network, a purely measurement-based model for dynamics estimation and control may be obtained. After a preliminary examination of the strong linearity of large-scale power systems, this paper proposes a linear autoregressive with exogenous input model (ARX)-structured power system dynamic model and demonstrates that this proposed model is effective in power system dynamic response estimation and instability warning. Both simulation and real measurement data have been used to validate the proposed method.

Model Free Command Filtered Backstepping Control for Marine Power Systems

In order to retrain chaotic oscillation of marine power systems which are excited by periodic electromagnetism perturbation, two novel model free command-filtered backstepping control methods are designed in this paper. Firstly, the dynamic model of marine power system based on the two parallel nonlinear models is established. Secondly, extended state observer (ESO) and adaptive neural network observer (NNO) are designed to estimate the velocity signal and the unknown dynamic model. Moreover, the uniform form of ESO and NNO is given. Next, the model free command-filtered backstepping controller is put forward based on the uniform observer form. Finally, the simulation results indicate that the two proposed control algorithms can quickly retrain chaotic oscillation and their effectiveness and potential are amply demonstrated.

Open Source Software Based Modeling of MEPE Test System for Stability Studies

This paper presents an implementation of MEPE test system in Power System Analysis Toolbox (PSAT)—free and open source software. This paper mainly focuses on the application of newly developed hydro turbine and governor model with detailed dynamic power system models on Myanmar national grid because the power system network is largely supplied by hydro power. This paper also demonstrates the rotor angle stability analysis of test system including classical small signal stability and transient stability criteria. Transient stability assessments of national grid test system are carried out through nonlinear time domain simulation by applying both large and small disturbances. Moreover, a statistical t-test is performed to ensure the effective of proposed model to deal with dynamic problem of the power system.

주파수추종 운전 적용을 위한 BESS의 운용 방법 및 효과

As the development of Battery Energy Storage System(BESS) and the increasing of intermittent energy sources like wind power and photovoltaic, the application of BESS in load frequency control is considered as an effective method. To evaluate the effectiveness of BESS application in frequency control, we defined a governor free model of BESS to conduct dynamic simulation. Using the BESS dynamic model, we implemented the power system dynamic model including steam, gas and hydro turbine generators. In this paper we study the control performance of BESS in primary frequency control. The effect of BESS speed regulation rate and response time on governor free operation is investigated. In addition, we compared BESS from steam turbine generator in view point of frequency regulation.

A probabilistic load shedding concept considering highly volatile local generation

Automatic load shedding is the ultimate countermeasure against imbalance in a power system and can effectively help preventing large blackouts. Taking into account a high penetration of renewable energy sources (RES) in the distribution grid, a clear distinction between load and generation at the PCC becomes increasingly more difficult. For that reason an adaptation of frequency relay parameters and their locations of installation are necessary. In Europe this is rest on a multi-step plan based on values such as the yearly peak load. In this paper a novel probabilistic method for automatic load shedding is presented that uses the average values instead of peak values for load shedding. Its applicability is verified by a dynamic power system model that was developed to compare the classical and novel probabilistic load shedding principle. The method is verified using data from a German TSO.

Applying a wide-area measurement system to validate the dynamic model of a part of European power system

In this paper a validation of dynamic model of a Slovenian power system using WAMS is presented. For this purpose a dynamic model of a part of the ENTSO-E system was constructed by applying two professional dynamic-simulation software tools that use different approaches to obtain mathematical solutions for the model to solve the problem. The simulation results were compared with each other as well as with the measurements gathered by the WAMS. Namely, Slovenia has almost full coverage of PMU measurements at the high-voltage level (220- and 400-kV) buses. This fact has been used to adapt the model, especially for the representation of the rest of the ENTSO-E network, as well as for the validation of the results and explaining the physical background for the existing differences. WAMS measurements for several different events occurring during 2010 and 2011 were used to adapt the model, which then exhibits a good match in all situations recorded by the WAMS. The physical background for the resulting deviations is presented. However, it should be pointed out that, after the model was finalized, for all the validated cases the system element parameters remained unchanged. Of course, depending on the simulated case, the initial steady-state conditions were set according to the measurements.

On modeling and control of advanced aircraft electric power systems: System stability and bifurcation analysis

This paper presents a comprehensive dynamic bifurcation model and stability study of advanced aircraft electric power system (AAEPS). The proposed bifurcation model is utilized to investigate the aircraft electric power system stability under various system configurations and loading conditions. Further investigations are performed to verify the sustainability and robustness of the aircraft electric power system and subsystems to time-dependent changes occurring in the system dynamics due to variations in control loop parameters and changes in the loading conditions and power demand. Moreover, stability analysis for changes in operating frequency of the aircraft electric power system’s AC channel is reported. It has been demonstrated that equilibrium points corresponding to the differential equations of the aircraft electric power systems undergo different bifurcation behaviors when the system’s operating parameters are subjected to variations. Finally, several case-study models are developed and implemented and the corresponding two-dimensional bifurcation diagrams were obtained with results verified using available experimental measurements. The AAEPS stability study and bifurcation analysis can assist engineers in identifying preferred regions of operation and safe margin design based on the variation of the system’s loading and parameters.

Automated modeling of power system dynamics using the Lagrangian formulation

SUMMARY An automated method is introduced for deriving the governing dynamic equations of electric power systems using the Lagrangian formulation. A main advantage of using the Lagrangian formulation to model the system dynamics is that this framework has been shown to be useful for passivity-based control. The automation of the modeling is valuable because for interconnected power systems, it is very complex to derive by hand. The automated method is demonstrated on an example interconnected power system. Finally, the differential equations derived in the stationary three-phase reference frame for this example are transformed to the rotating two-phase reference frame, and simulations in the different reference frames are shown and analyzed. Copyright © 2014 John Wiley & Sons, Ltd.