Design and quasi-equilibrium analysis of a distributed frequency-restoration controller for inverter-based microgrids

This paper discusses a proposed frequency-restoration controller which operates as an outer loop to frequency droop for voltage-source inverters. By quasi-equilibrium analysis, we show that the proposed controller is able to provide arbitrarily small steady-state frequency error while maintaing power sharing between inverters without need for communication or centralized control. We derive rate of convergence, discuss design considerations (including a fundamental trade-off that must be made in design), present a design procedure to meet a maximum frequency error requirement, and show simulation results verifying our analysis and design method. The proposed controller will allow flexible plug-and-play inverter-based networks to meet a specified maximum frequency error requirement.

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North American Power Symposium (NAPS), 2013

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High temperature low sag (HTLS) technologies as upgrades for overhead transmission systems

This paper addresses the subject of transmission expansion. A relatively new technology, high temperature low sag (HTLS), is considered for overhead transmission. HTLS conductors have high ampacity, but also high cost. The paper outlines the favorable and unfavorable characteristics of HTLS conductors. The portion of the Western Electricity Coordinating Council (WECC) system in the state of Arizona is used as a test bed. The summer peak 2012 loading data are used. The case considered is the expected integration of large scale solar generation resources.

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North American Power Symposium (NAPS), 2013

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Validated short circuit modeling of Type 3 Wind Turbine Generator with crowbar protection

With fast increasing penetration of wind generation around the world, it is important to document accurate short circuit models of different types of wind turbine generators (WTGs) and wind farms. This paper documents and analyzes the short circuit response of Type 3 WTG with crowbar protection. The model is first simulated and validated using field data from a wind farm having Type 3 WTGs. PSCAD is used for simulation. The validated model is used to study the short circuit behavior of the WTG. Based on the study, Thevenin model of the wind farm is derived.

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North American Power Symposium (NAPS), 2013

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Development of a linearized model of a pressurized water reactor generating station for power system dynamic simulations

A pressurized water reactor (PWR) nuclear power plant (NPP) model is introduced into Positive Sequence Load Flow (PSLF) software in order to evaluate the load-following capability of NPPs. The nuclear steam supply system (NSSS) consists of a reactor core, hot and cold legs, plenums, and a U-tube steam generator. The physical systems listed above are represented by mathematical models utilizing a state variable lumped parameter approach. A steady-state control program for the reactor, and simple turbine and governor models are also developed. Subsequently, the NSSS representation is incorporated into PSLF and coupled with built-in excitation system and generator models. Different simulation cases are run when sudden loss of generation occurs in a power system which includes hydroelectric and natural gas power plants besides the developed PWR NPP. The effect of the load-following operational mode on the key variables of the NSSS is observed.

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North American Power Symposium (NAPS), 2013

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Parallel Kalman filter based time-domain harmonic state estimation

A time domain methodology is proposed for the harmonic state estimation (HSE) in power systems based on parallel Kalman filter (PKF) algorithm implemented on a graphical processing unit (GPU). The output variable measurements to be used by the HSE are taken from the simulation of the harmonics propagation in the power system. The time domain HSE solution process is based on the application of the PKF algorithm to estimate the waveforms for nodal voltages and line currents with various sources of harmonics, time-varying harmonics and inter-harmonics. The results obtained with the PKF to solve the HSE are validated against the transient program PSCAD/EMTDC. The PKF algorithm is implemented using the Compute Unified Device Architecture (CUDA) platform and the CUDA Basic Linear Algebra Subprograms (CUBLAS) library on a NVIDIA GPU card. Case studies show the effectiveness of the PKF to solve the HSE on the GPU, the speed-up is dependent of the size and complexity of the network model.

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North American Power Symposium (NAPS), 2013

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Frequency control design for two-areas network connected with HVDC

Regulating frequency deviation is one of the most important issues in power systems. For this purpose, it is necessary to maintain the balance between demand and supply power in real time. Governors change inputs of turbines when frequency variation is caused by a load change. But, in an overload condition, the governor cannot control the frequency drop because of its slow response. In this paper, a new control strategy for two connected systems with HVDC is proposed. The performance of the control system has been validated by simulations of normal operation and overload conditions in MATLAB/Simulink.

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North American Power Symposium (NAPS), 2013

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A machine learning-based faulty line identification for smart distribution network

This paper presents a machine learning-based faulty-line identification method in smart distribution networks. The proposed method utilizes postfault root-mean-square (rms) values of voltages measured at the main substation and at selected nodes as well as fault information obtained by fault current identifiers (FCIs) and intelligent electronic re-closers (IE-CRs). The information from FCIs and IE-RCs are first used to identify the faulty region in the network. The normalized rms values of voltages are then utilized as the input to the support vector machine (SVM) classifiers to identify the faulty-line according to the pre-determined fault type. The IEEE 123-node distribution test system is simulated in ATP software. MATLAB is used to process the simulated transients and to apply the proposed method. The performance of the method is tested for different fault inception angles (FIA) and different fault resistances with satisfactory results.

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North American Power Symposium (NAPS), 2013

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Suitable placements of multiple FACTS devices to improve the transient stability using trajectory sensitivity analysis

Trajectory sensitivity analysis (TSA) is used as a tool for suitable placement of multiple series compensators in the power system. The goal is to maximize the benefit of these devices in order to enhance the transient stability of the system. For this purpose, the trajectory sensitivities of the rotor angles of the most critical generators with respect to the reactances of transmission lines are calculated in the presence of the most severe faults. Based on the obtained trajectory sensitivities, a method is proposed to determine how effective the series compensation of each transmission line is for improving the transient stability. This method is applied to the Nordic-32 test system to find the priorities of the transmission lines for installation of several series compensators. Simulation with industrial software shows the validity and efficiency of the proposed method.

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North American Power Symposium (NAPS), 2013

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Accelerated parallel WLS state estimation for large-scale power systems on GPU

Owing to the growing size and complexity of power networks, online monitoring of the power system state is a challenging computational problem. State estimation is paramount for reliable operation of large-scale power systems. Even with modern multi-core processors, the large number of computations in state estimation are still a burden on time and are highly memory intensive. In this paper the idea of using massively parallel graphic processing units (GPUs) for weighted least squares (WLS) based state estimation is introduced and executed. The GPU is especially designed for processing large data sets. A data-parallel implementation of the WLS method is proposed. The speed of the GPU-based state estimation for several test systems is compared with a sequential CPU-based program. The simulation results show a speed-up of 38 for a 4992-bus system.

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North American Power Symposium (NAPS), 2013

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Real-time synchronization control for standalone distribution networks in islanded power systems

Traditional synchronizer cannot control multiple generators in distribution networks in coordination. In this paper, a real-time synchronization control (RTSC) is designed to keep all generators in different standalone distribution networks in synchronization at all times, which realizes a fast and reliable reconnection of disconnected power network. The frequency control and phase control in RTSC are investigated and low-pass filters are properly designed to avoid interference between these two controls. The simulation results in an isolated power system is verified the effectiveness of RTSC and have proved that the transient stability during reconfiguration process can be greatly enhanced by applying RTSC into system-level supervisory control of isolated power system.

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North American Power Symposium (NAPS), 2013

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