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Primary open-phase faults on station auxiliary transformers(SATs) are characterized by the presence of voltage unbalance at the auxiliary equipment level that could lead to protective device tripping, increased motor acceleration times, overheating or failure to start critical safety loads, particularly in the nuclear power industry. The transformer primary to ground zero sequence impedance has a...
Interactions between three-phase grid-connected voltage source converter (VSC) and ac network have been analyzed using the VSC ac-side impedance models in the dq-domain, and more recently, in the sequence domain. Both dq and sequence domain approaches ignore the effects of a network at the VSC dc-side terminals. Interactions between VSC and dc network have been similarly analyzed by ignoring the effects...
Electrical distribution systems are experiencing higher amount of distributed generation (DG), which originates from societal and environmental concerns, economical benefits of local generation, and more deregulated energy systems. While having numerous advantages, the presence of DG in the system is limited by several constraining factors. In this paper, in order to allow for higher hosting capacity...
Energy router is an emerging conceptual device based on advanced power electronic technique. It is able to realize the flexible and dynamic electric power distribution in power systems as information router in the Internet. It is of great interest to investigate how the energy router can be used to improve the power system operation. This paper proposes a generalized configuration of the energy router...
The impact of phase locked loop (PLL) parameters on the dynamic and steady-state behavior of a Voltage Sourced Converter (VSC) in an HVdc transmission system is determined as a function of the system strength (parameterized by the short circuit ratio -SCR). This is achieved by using a linearized small signal model of the converter system and its controls. The model is validated via electromagnetic...
Multiple events across the nuclear power industry have highlighted the need for greater understanding of what happens during an open phase fault. These open phase events have occurred on the high side of offsite power supply transformers and have involved loss of one or two phases. This paper explores a method to characterize the downstream system response to an open phase fault using steady-state...
Dynamic load controllers for thermostatically controlled loads should allow for accurate control of power consumption and should not disrupt the quality of service. This paper proposes an intuitive definition of nondisruptiveness for systems with second-order thermal models, based on a decomposition into fast and slow temperature modes. It enables the explicit control of the slow mode temperature...
This paper presents a constraint formulation for the dynamic control of HVDC links that are used to support the surrounding AC power grid during power oscillations and electromechanical transients. The admissible HVDC injection references have to respect physical constraints, imposed by the converter and the strength of the connected AC network. The main result is a derivation of the HVDC constraint...
In recent years, complex operating conditions have greatly reduced the predictability of electric grid operations and hence, there is an urgent need to improve grid security more than ever before. The best approach would be to improve grid intelligence rather than simply hardening the grid. An implementation of dynamic security assessment (DSA) would require carrying out time-domain simulations that...
In power systems with increasing variable renewable sources, gas generation is playing an increasingly prominent role in providing flexibility to meet net-load requirements. The flexibility provided by the gas turbines in turn relies on the flexibility of the gas network. While there are several discussions on the gas network's ability in providing this operational flexibility, this has not been clearly...
The encroachment of the measured load impedance into the outer tripping zone was one of the main problems of distance protection relays since their application. Highly loaded transmission lines intensified this issue and caused cascading failures worldwide during the last decades. Restricted zone reach settings or load blinders in the R-X-impedance plane were the common countermeasures until now....
Capacitor banks are commonly connected to the power system to enhance its reliability by providing voltage support, improving power factor, and increasing the system capacity. They are usually switched in and out of the system according to the amount of connected load. This paper analyzes the measurement data of a distribution utility with shunt capacitor banks located downstream from the power quality...
This paper proposes a new method to train a regression tree for disturbance classification based on long term records considering the most probable operational conditions obtained by historical data of the analyzed system. Unlike the usual, deterministic approach of simulating a set of predetermined conditions varying fault resistance and position, the decision making process is now supported by a...
The primary objective of this paper is to highlight the need for and benefits of studying the steady state and dynamic response of power systems using three phase integrated transmission and distribution (T&D) system models (hereafter referred to as hybrid models). Modeling and simulation requirements for building and analyzing hybrid models are also discussed. Finally, results from steady state...
This paper presents a new control strategy for a distributed static compensator (also known as distributed STATCOM or DSTATCOM), configured to regulate the reactive (VAr) flow at a point in a transmission system. This new control strategy takes into account the operating VAr limits of that reactive flow in determining the steady-state output of the DSTATCOM. The new control strategy applies a slow...
In this paper, a generalized models are presented for different hybrid ac/dc microgrids components in the islanded mode of operation. In this scenario, power sharing schemes are based on local information to manage the system power with the absence of the main substation. Instead, the DG units operate based on droop characteristics, thereby forming a multi-slack distribution system, and accordingly...
The integrated energy systems (IESs), composed of deeply interdependent electric power systems (EPSs) and natural-gas systems (NGSs), are expected to play an important role in the transition to low-carbon sustainable energy systems. To facilitate the security assessment of IESs, this paper initially proposes the concept of IES security region. First, The security region of the IES is defined as a...
This paper develops an integrated multi-domain simulation tool for distribution systems designed specifically for applications in wind power analysis. The proposed tool consists of steady-state, electromechanical transient, and electromagnetic transient models of voltage sources, transmission lines, transformers, capacitor banks, fixed-speed wind turbines (FSWTs), and wide-slip wind turbines (WSWTs)...
This paper presents a multi-objective optimization model based on DC power flow to maximize the active power steady-state security region whilst minimizing the total generation cost. The stochastic and fluctuant nature of wind power is incorporated into the model as well. Regarding the cost of wind power, the concepts involving opportunity costs of wind power shortage and surplus are introduced in...
Aiming at the problem of circulating current in MMCs, a novel circulating current suppressing controller (CCSC) is proposed based on the internal-model principle in stationary αβ0 frame in dc-loop control, with the proportional-resonant (PR) regulator adopted. Compared with the existing one, the proposed CCSC seems better, since it does not need the massive amount of computation for estimating the...
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