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As penetration of renewable energy sources is increasing, Long-Term Voltage Stability of FSIGs has raised major concern for distribution power networks since they will always consume reactive power. When either the voltage profile of FSIG severely declines due to load consumption increasing in nearby area, or mechanical power of wind turbine increases owing to wind speed increasing, the loss of stable...
In this paper, a new planning methodology is proposed for existing distribution grids, considering both passive and active network measures. The method is designed to be tractable for large grids of any type, e.g., meshed or radial. It can be used as a decision-making tool by distribution system operators which need to decide whether to invest in new hardware, such as new lines and transformers, or...
This paper studies the coordination of MMC converter protection and DC line protection in DC transmission networks. To quickly isolate a DC line fault, hybrid DC circuit breaker is connected at each end of every DC transmission line. DC line protection based on measuring derivative of DC voltage is employed to timely trip faulted DC line only. The goal of protection coordination is to prevent blocking...
In recent years, voltage and reactive power control in distribution systems is becoming increasingly complex with the growing penetration levels of distributed energy resources (DER), electric vehicle loads, and new requirements like conservation voltage reduction (CVR). Traditional approaches of voltage control rely on slow acting electromechanical devices installed on the primary feeder. These approaches...
In Germany, the absorption capacity of distributed generation (DG) in rural and suburban low voltage (LV) networks is currently restricted due to possible over-voltages above the limit set by the voltage standard. Whilst the thermal limits can only be solved by storage, curtailment or network extension, a number of advanced and relatively affordable technologies can be implemented to maintain the...
The main task of the state estimator in power systems is the provision of the power system state accurately. In order to achieve this, the measurement set has to be validated by identifying erroneous measurements. This is usually achieved by using either the Chi-square or the Largest Normalized Residual test. In both tests, the estimated states that are provided by the state estimator and the measurement...
Wide-area measurement-based voltage stability assessment (VSA) by coupled single-port circuit models has been widely discussed recently. This method models the coupling effects of load buses within a meshed network into extra impedance of a single-port model for each load bus. In simulation studies, overestimations of voltage stability margin using this approach have been observed when critical load...
The smart grid is a typical cyber-physical system (CPS) utilizing more advanced information and communication technologies (ICTs), in which hierarchical control system (HCS) plays an essential role. However, it should be noted that for the same control function, HCSs could have multiple modes for making control decisions. They may have different cyber structures and information flows, which could...
This paper explores the area of double-input single-output DC-DC converters to develop a photovoltaic (PV) source based DC microgrid which is incorporated with maximum power point tracking control technique. The converter used is a fifth-order converter utilizing boost plus single ended primary inductor converter topology which draws power from the two PV sources simultaneously and supplies upstream...
In modern power systems, the integration of variable and random renewable energy brings more challenges to real-time voltage stability monitoring and control. Loading margin sensitivity (LMS) is an index that is widely-used to evaluate voltage stability. The accuracy of LMS relies on the credibility of the data collected by local measurement units, which are used to estimate the system model parameters...
Analyzing the voltage stability of the smart grid requires accurate mathematical models of the load. Several static and dynamic load models were proposed, but most of them did not incorporate the frequency component. In order to build more accurate dynamic load models in the power system, we must examine the mathematical characteristics (short range versus long range dependence) of the power system...
This paper proposes a measurement-based voltage stability monitoring method for a load area fed by N tie lines. Compared to a traditional Thevenin equivalent based method, the new method adopts an N+1 buses equivalent system so as to model and monitor individual tie lines. For each tie line, the method solves the power transfer limit against voltage instability analytically as a function of all parameters...
Recently, many aspects of power system dynamic analysis, including oscillation identification, load model identification and system state estimation, are conducted based on the measurement data from phasor measurement unit (PMU). However, the impact of PMU measurement error, especially in power system dynamic process, has an assignable impact on these analysis results and thus cannot be neglected...
In a modern transmission system, wide area monitoring system (WAMS), which is capable to perform real time monitoring and control, is employed. State estimation process using PMU data is one of the important parts in WAMS since the current operating condition of the power system should be represented precisely. Practically, the measurement errors due to the communication congestion are existed and...
In most substation protection studies, capacitor bank parameters are derived from manufacturer nameplate values. However, the actual parameters could be different from the nominal rating as a result of manufacturing variance, assembling, material aging, and temperature dependencies. Wide manufacturing tolerance could lead to non-negligible calculation inaccuracy that affecting successive studies....
A measurement-based voltage stability assessment and closed-loop control strategy is proposed and demonstrated on the Center for Ultra-Wide-Area Resilient Electric Energy Transmission Networks (CURENT) Hardware Test Bed (HTB) system, a power electronic converter-based research and experiment platform. This new strategy is based on an N+1 buses equivalent proposed recently by Ref. [1] for calculating...
This paper proposes an Unscented Kalman Filter (UKF) based Load Model Identification method to analyze the Conservative Voltage Reduction (CVR) effects, i.e., the change in load consumption to the change in voltage. We use exponential load model to represent load as a function of voltage. With the implementation of UKF, real-time CVR effects can be assessed by estimating the load-to-voltage sensitivities...
The growing integration of distributed energy resources (DERs) in urban areas raises various reliability issues. To ensure robust distribution grid operation, grid monitoring tools are needed, where the topology reconstruction serves as the first step. However, the topology reconstruction is hard in distribution grid. This is because 1) the branches are difficult and expensive to monitor since most...
Traditional monitoring systems for transmission and distribution (T&D) networks are only installed in substations, so there is no real-time and accurate power information available for on-site power quality monitoring and equipment maintenance. This issue increases the fault risk in T&D networks, and degrades the reliability and quality of power supply. Moreover, it is often difficult and...
This paper presents a practical method for a real-time measurement of the ratio ρ = rneq / r (r = line resistance, rneq = equivalent neutral path resistance) of a three-phase four-wire distribution feeder and advocates the possibility of ignoring the zero-sequence voltage component due to its reduced magnitude in practical situations. The ratio ρ has a significant impact on the value of the apparent...
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