Impact of Reverse Power Flow in Distribution Feeders on Under-Frequency Load Shedding Schemes

2020 ◽  
Author(s):  
Russell Frost ◽  
Lucas Zieland ◽  
Dean Sharafi ◽  
Julius Susanto
Keyword(s):  
Power Flow ◽  
Load Shedding

scholarly journals A Three-Stage Procedure for Controlled Islanding to Prevent Wide-Area Blackouts

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3066 ◽  
Author(s):  
Hongbo Shao ◽  
Yubin Mao ◽  
Yongmin Liu ◽  
Wanxun Liu ◽  
Sipei Sun ◽  
...  
Keyword(s):  
Power System ◽  
Dynamic Stability ◽  
Power Flow ◽  
Transient Stability ◽  
Load Shedding ◽  
Area Measurement ◽  
Wide Area ◽  
Measurement Systems ◽  
Controlled Islanding ◽  
Three Stages

Controlled islanding has been proposed as a last resort action to stop blackouts from happening when all standard methods have failed. Successful controlled islanding has to deal with three important issues: when, and where to island, and the evaluation of the dynamic stability in each island after islanding. This paper provides a framework for preventing wide-area blackouts using wide area measurement systems (WAMS), which consists of three stages to execute a successful islanding strategy. Normally, power system collapses and blackouts occur shortly after a cascading outage stage. Using such circumstances, an adapted single machine equivalent (SIME) method was used online to determine transient stability before blackout was imminent, and was then employed to determine when to island based on transient instability. In addition, SIME was adopted to assess the dynamic stability in each island after islanding, and to confirm that the chosen candidate island cutsets were stable before controlled islanding was undertaken. To decide where to island, all possible islanding cutsets were provided using the power flow (PF) tracing method. SIME helped to find the best candidate islanding cutset with the minimal PF imbalance, which is also a transiently stable islanding strategy. In case no possible island cutset existed, corresponding corrective actions such as load shedding and critical generator tripping, were performed in each formed island. Finally, an IEEE 39-bus power system with 10 units was employed to test this framework for a three-stage controlled islanding strategy to prevent imminent blackouts.

scholarly journals A Computationally Improved Heuristic Algorithm for Transmission Switching Using Line Flow Thresholds for Load Shed Reduction

2021 ◽  
Author(s):  
Tanveer Hussain ◽  
S M Shafiul Alam ◽  
Timothy M. Hansen ◽  
Siddharth Suryanarayanan
Keyword(s):  
Power Flow ◽  
Optimal Power Flow ◽  
Heuristic Method ◽  
Search Space ◽  
Load Shedding ◽  
Mesh Topology ◽  
Transmission Switching ◽  
Computational Performance ◽  
Topology Changes ◽  
Line Flow

A computationally improved algorithm to find the best transmission switching (TS) candidate for load shed reduction after (<i>N</i>-2) contingencies is presented. TS is a planned line outage and research from the past shows that changing transmission system's mesh topology changes the power flows and removes post contingency violations (PCVs). One of the major challenges is to find the best TS candidate in a suitable time. Here, the best TS candidate is determined by using a novel heuristic method by decreasing the search space based on proximity to load shedding bus (LSB). The proposed method is capable of finding the best TS candidate faster than the well-known existing algorithm in the literature and guarantees removal of PCVs. Moreover, proposed algorithm is compatible with both AC and DC optimal power flow (OPF) formulations. Finally, the proposed method is implemented by modifying the topology of the transmission system after (<i>N</i>-2) contingencies in the IEEE 39-bus, IEEE 118-bus, and Polish 2383-bus test systems. Two metrics are used to compare results from the proposed method with those from state-of-the-art to show the speedup and accuracy achieved. Parallel computing is used to increase the computational performance of the proposed algorithm.

scholarly journals Study on Emergency Load Shedding of Hybrid AC/DC Receiving-End Power Grid with Stochastic, Static Characteristics-Dependent Load Model

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3912 ◽  
Author(s):  
Yingying Jiang ◽  
Xiaolin Chen ◽  
Sui Peng ◽  
Xiao Du ◽  
Dan Xu ◽  
...  
Keyword(s):  
Direct Current ◽  
Transmission Lines ◽  
Power Flow ◽  
Large Scale ◽  
Power Grid ◽  
Fault Analysis ◽  
Load Shedding ◽  
Total Power ◽  
Power Imbalance ◽  
Factors Affecting

When large-capacity HVDC (high voltage direct current) transmission line blocking occurs in a hybrid AC/DC (alternating current/direct current) power grid, the receiving-end system will encounter a huge power imbalance, which will lead to a frequency drop and redistribution of the power flow, and which may further lead to the overload of other transmission lines, cascading failures and a large-scale blackout. To resolve these problems, an emergency load-shedding strategy for the DC receiving-end system is proposed from the perspective of a quasi-steady state. The proposed method can accurately calculate the actual total power imbalance by modeling more detailed stochastic loads with static frequency/voltage characteristics and involving the inertia effect of the generator during the response delay period, which can effectively reduce the amount of load curtailment. In addition, several factors affecting the power imbalance estimation in stochastic scenarios and their mechanisms are analyzed in detail, and the key aspects relevant to the DC blocking fault analysis are identified as well. Finally, the influence of different load-shedding strategies on the receiving-end system security after a DC blocking fault is compared with the security indices, including those that are relevant to the frequency/load change proposed herein, and a uniform load-shedding coefficient is obtained via the proposed method, even for different power imbalances under a stochastic context, which makes the load-shedding strategy more practical.

Effect of Advanced Static VAR Compensator on Control of Power System Load Shedding

2011 ◽  
Vol 403-408 ◽  
pp. 4867-4872
Author(s):  
B. Venkateswara Rao ◽  
G. V. Nagesh Kumar ◽  
R. V. S. Lakshmi Kumari ◽  
M. Vinay Kumar
Keyword(s):  
Power System ◽  
Power Flow ◽  
Test System ◽  
Load Shedding ◽  
System Stability ◽  
Static Var Compensator ◽  
System Load ◽  
Flow Solution ◽  
Newton Raphson ◽  
Raphson Method

This paper investigates the effect of Static VAR Compensator (SVC) on power system load shedding. SVC is mainly used in power system stability improvement. This paper proposes a new use of SVC to reduce load shedding. An algorithm of Newton Raphson method (NR) to reduce the load shedding for installing SVC in the system is proposed in this paper. 5 bus test system example is used to demonstrate the effect on load shedding. The test results show that the effect of SVC is significant, in this Static VAR compensator (SVC) is incorporated in Newton Raphson method in which Power Flow Solution is a solution of the network under steady state conditions subjected to certain constraints under which the system operates. The power flow solution gives the nodal voltages and phase angles given a set of power injections at buses and specified voltages at a few, the model of SVC i.e. SVC Susceptance model is discussed. It is also shown that the power system losses are decreased after incorporating the SVC in this N-R method. The results are generated for 5-Bus system. By incorporating the SVC the amount of load shedding is reduced to get the voltages in their limits.

scholarly journals A Computationally Improved Heuristic Algorithm for Transmission Switching Using Line Flow Thresholds for Load Shed Reduction

2021 ◽  
Author(s):  
Tanveer Hussain ◽  
S M Shafiul Alam ◽  
Timothy M. Hansen ◽  
Siddharth Suryanarayanan
Keyword(s):  
Power Flow ◽  
Optimal Power Flow ◽  
Heuristic Method ◽  
Search Space ◽  
Load Shedding ◽  
Mesh Topology ◽  
Transmission Switching ◽  
Computational Performance ◽  
Topology Changes ◽  
Line Flow

A computationally improved algorithm to find the best transmission switching (TS) candidate for load shed reduction after (<i>N</i>-2) contingencies is presented. TS is a planned line outage and research from the past shows that changing transmission system's mesh topology changes the power flows and removes post contingency violations (PCVs). One of the major challenges is to find the best TS candidate in a suitable time. Here, the best TS candidate is determined by using a novel heuristic method by decreasing the search space based on proximity to load shedding bus (LSB). The proposed method is capable of finding the best TS candidate faster than the well-known existing algorithm in the literature and guarantees removal of PCVs. Moreover, proposed algorithm is compatible with both AC and DC optimal power flow (OPF) formulations. Finally, the proposed method is implemented by modifying the topology of the transmission system after (<i>N</i>-2) contingencies in the IEEE 39-bus, IEEE 118-bus, and Polish 2383-bus test systems. Two metrics are used to compare results from the proposed method with those from state-of-the-art to show the speedup and accuracy achieved. Parallel computing is used to increase the computational performance of the proposed algorithm.

scholarly journals A Novel Self-Healing Strategy for Distribution Network with Distributed Generators Considering Uncertain Power-Quality Constraints

2020 ◽  
Vol 10 (4) ◽  
pp. 1469
Author(s):  
Song Ke ◽  
Tao Lin ◽  
Rusi Chen ◽  
Hui Du ◽  
Shuitian Li ◽  
...  
Keyword(s):  
Power Quality ◽  
Power Flow ◽  
Distribution Network ◽  
Load Shedding ◽  
Network Reconfiguration ◽  
Self Healing ◽  
Distributed Generators ◽  
Recovery Capacity ◽  
Sequence Components ◽  
Optimization Efficiency

Self-healing of smart distribution networks with distributed generators, which are usually operated as independent islands after fault, can improve power-supply reliability. As a hot research topic, a self-healing scheme is usually treated as the output of a nonlinear optimizuoation model. However, existing strategies have two main shortcomings. The first, high-optimization dimension, results in low-optimization efficiency. The second, the effects of power-quality issues, which are more serious on islands and may further threaten the safe operation of islands, is usually neglected. To quickly obtain a reliable self-healing scheme, a novel strategy is proposed. As the first step, the distribution network after a fault occurrence can be divided into several trouble-free subnets via the connectivity analysis; each subnet is called an initial island. Further, for each initial island, a two-step optimization model of self-healing, which consists of load-shedding optimization and network reconfiguration optimization, is proposed to obtain the self-healing strategy with lower searching space as well as higher solving efficiency. In detail, in load-shedding optimization, by means of heuristic differential evolution algorithm, larger total recovery capacity is achieved by considering the droop characteristic of distributed generators (DGs) within the permissible change in frequency. In network-reconfiguration optimization, based on the improved hybrid particle swarm optimization algorithm, a comprehensive set of power-quality constraints, including constraint of change in frequency, uncertain constraints of node voltage total harmonic distortion (THD), and negative sequence components of DGs, is developed to guarantee the reliability of each island. To evaluate whether the constraints are satisfied during the optimization procedure, an improved flexible power-flow algorithm is developed to calculate the power flow of each island under change in frequency. Further, 2m+1-point estimate method is employed for uncertainty analyses of the distributions of harmonic and negative sequence components caused by the uncertainty of corresponding sources. Finally, via a 94-node practical distribution network, the effectiveness and advantages of the proposed strategy in safety, recovery capacity, and optimization efficiency are verified.

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