2018 IEEE Power & Energy Society General Meeting (PESGM), 2018
This paper investigates the overvoltage problem caused by micro-generators (MGs) in secondary dis... more This paper investigates the overvoltage problem caused by micro-generators (MGs) in secondary distribution feeders. The allowable MG active power injection into a particular feeder essentially depends on the system R/X ratio, supply impedance (system fault level) and feeder topology. Different from transmission systems, distribution systems exhibit a high R/X ratio, involving large amount of reactive power for voltage regulation which cannot be entirely provided by MGs alone. Hence, a limit exists on the allowable MG power injection within acceptable voltage rise tolerances. This paper presents analytical and case studies, clarifying the relation between MG power, feeder characteristics (R/X ratio and fault level) and voltage rise. It also provides some useful charts and equations to estimate voltage rise, maximum allowable MG power and required reactive power for typical R/X ratios and fault levels. The application of switchable shunt inductors as means of voltage rise mitigation in secondary distribution systems with high R/X ratios is also demonstrated in this paper.
Distributed energy resources (DERs) are a new class of disruptive technologies with rapidly incre... more Distributed energy resources (DERs) are a new class of disruptive technologies with rapidly increasing adoption levels due to favorable government policies and subsidies. However, these emerging technologies come with technical challenges for utilities and system operators; for instance, voltage rise issues in residential secondary distribution systems with high penetration of DERs. One of the low-cost mitigation options to alleviate the overvoltage problem is reactive power absorption. Nevertheless, secondary feeders exhibit a high R/X ratio more noticeably than primary distribution systems, requiring large amount of reactive power for voltage regulation that cannot be entirely provided by the DERs alone. It is also necessary to minimize the reactive power drawn from the primary distribution system to prevent any stress on the network and reduce extra system losses, while at the same time ensuring the voltage within admissible limits. To address these critical issues, this paper proposes a distributed reactive power management, where additional source is provided from inexpensive devices such as switchable shunt reactors. The proposed overvoltage mitigation is accompanied by detailed analytical investigation that estimates the minimum amount of required reactive power to manage the voltage with user specified voltage rise tolerances. Case studies have also been conducted on real residential distribution systems subjected to severe voltage rise issues provoked by large adoption of DERs.
IEEJ Transactions on Electrical and Electronic Engineering, 2016
This paper presents an efficient way of solving the distribution system reconfiguration (DSR) pro... more This paper presents an efficient way of solving the distribution system reconfiguration (DSR) problem in electrical power systems with consideration of different types of distributed generators (DGs). The objective of a DSR is to minimize the system power loss while satisfying the system constraints and keeping the topology of the system radial. In this paper, a new DSR algorithm based on a modified particle swarm optimization (PSO) is proposed to incorporate DGs with the constant voltage control mode. The proposed method is very efficient because it avoids an extra iteration loop for computing the reactive power at PV buses in order to keep the voltage at a specified magnitude. Furthermore, if the reactive power requirement is not met in between the extreme limits, the proposed algorithm strictly searches for the best possible tie switch combination to simultaneously reduce the power loss and ensure that the DGs operate in PV mode within acceptable reactive power limit. The propose...
The stochastic nature of demand and wind generation has a considerable effect on solving the sche... more The stochastic nature of demand and wind generation has a considerable effect on solving the scheduling problem of a modern power system. Network constraints such as power flow equations and transmission capacities also need to be considered for a comprehensive approach to model renewable energy integration and analyze generation system flexibility. Firstly, this paper accounts for the stochastic inputs in such a way that the uncertainties are modeled as normally distributed forecast errors. The forecast errors are then superimposed on the outputs of load and wind forecasting tools. Secondly, it efficiently models the network constraints and tests an iterative algorithm and a piecewise linear approximation for representing transmission losses in mixed integer linear programming (MILP). It also integrates load shedding according to priority factors set by the system operator. Moreover, the different interactions among stochastic programming, network constraints, and prioritized load ...
2016 IEEE International Conference on Advanced Intelligent Mechatronics (AIM), 2016
A detailed traction model for the Taipei Mass Rapid Traction system is developed, and a new speed... more A detailed traction model for the Taipei Mass Rapid Traction system is developed, and a new speed controller based on Neural Network and PID (NN-based PID) is proposed. The model, which is developed in MATLAB/ Simulink, has three main parts: traction system, third rail voltage system, and load. The train model characterizes the traction motor and the coupling effect of mechanical and electrical parts of the train system. Moreover, the efficiency changes and switching transitions can be observed. An NN-based PID controller is used because of its self-adaptive capability. A case study of an actual track is presented to demonstrate the robustness of the proposed controller.
2015 IEEE 15th International Conference on Environment and Electrical Engineering (EEEIC), 2015
This paper presents an efficient and accurate way of solving radial distribution system reconfigu... more This paper presents an efficient and accurate way of solving radial distribution system reconfiguration (DSR), which plays an important role in distribution automation for realizing smart grids. It deploys different heuristic optimization approaches to resolve the desired optimum configuration and to efficiently reconfigure the connectivity of the distribution networks. The objective is to minimize the system power loss while the voltage in each bus is limited to some allowable range, and the topology of the system is kept radial. In this paper, a hybrid algorithm consisting of particle swarm optimization (PSO) and genetic algorithm (GA) is proposed. The first part of the hybrid approach is based on a modified PSO where the initial swarm of particles fit the radiality constraint and it introduces external randomness to velocities and locations with certain probabilities when particles are in equilibrium or close to equilibrium state. The second part is a modified GA which receives its initial population from best solutions of the modified PSO and uses adaptive mutation for introducing population diversity. In addition, the particle's location in PSO and each chromosome in GA are repaired in such a way that the radiality constraint is always satisfied. The validity and the effectiveness of the proposed method has been tested using the standard IEEE 33-bus distribution network. The results show that the proposed method is robust and delivers a minimal average power loss of independent runs with reduced computational time.
2015 International Conference on Advanced Robotics and Intelligent Systems (ARIS), 2015
This paper presents a new robust methodology for solving radial distribution system reconfigurati... more This paper presents a new robust methodology for solving radial distribution system reconfiguration (DSR) problem based on the concept of cooperative multi-thread strategy and hybrid meta-heuristics. The parallel cooperative meta-heuristics (PCMH) method deploys multiple concurrent explorations of the solution space using genetic algorithm (GA), particle swarm optimization (PSO) and ant colony system (ACS) running in parallel on independent processors. The meta-heuristics are subjected to communicate and cooperate with each other synchronously at a specified interval in the course of iteration. Dynamically at each interval, the best solution so far found is exchanged among all the three processors. In addition, the worst individuals of GA are replaced by the best particles of PSO if the current optimum is delivered by PSO; otherwise the best ants from ACS replace these individuals. The proposed method is applied to the standard IEEE 33-bus distribution network with the objective of minimizing the overall power loss while at the same time accounting for the operational constraints within allowable limits. The results demonstrate the validity and the effectiveness of the proposed approach in terms of accuracy and robustness.
2018 IEEE Power & Energy Society General Meeting (PESGM), 2018
Increased environmental concerns, changing regulations, and government subsidies have played a ke... more Increased environmental concerns, changing regulations, and government subsidies have played a key role in incenting renewable generation. Solar generation has been increasingly proliferating among residential customers in many US states and Canadian provinces. Photovoltaic generation is connected through DC-AC inverters. The operation of these inverters has been a focal point of discussion in recent years. The California Independent System Operator has chaired the development of Rule 21, which was the base for the subsequent UL1741SA standard, paving the way for the upcoming revision of IEEE 1547. Canadian standards are following suit, with upcoming revisions to CSA C22.3 No 9 and C22.2 No 257. These standards require new inverters to feature autonomous functions such as Volt-Watt and Volt-VAR, as well as provision for compatibility with centralized management systems. This paper analyzes the impact of PV curtailment through the Volt-Watt function, as compared with the installation of a Battery Energy Storage System, on voltage management of one feeder of a Canadian electric utility. Technical constraints and economic factors are considered.
2018 IEEE Power & Energy Society General Meeting (PESGM), 2018
This paper investigates the overvoltage problem caused by micro-generators (MGs) in secondary dis... more This paper investigates the overvoltage problem caused by micro-generators (MGs) in secondary distribution feeders. The allowable MG active power injection into a particular feeder essentially depends on the system R/X ratio, supply impedance (system fault level) and feeder topology. Different from transmission systems, distribution systems exhibit a high R/X ratio, involving large amount of reactive power for voltage regulation which cannot be entirely provided by MGs alone. Hence, a limit exists on the allowable MG power injection within acceptable voltage rise tolerances. This paper presents analytical and case studies, clarifying the relation between MG power, feeder characteristics (R/X ratio and fault level) and voltage rise. It also provides some useful charts and equations to estimate voltage rise, maximum allowable MG power and required reactive power for typical R/X ratios and fault levels. The application of switchable shunt inductors as means of voltage rise mitigation in secondary distribution systems with high R/X ratios is also demonstrated in this paper.
Distributed energy resources (DERs) are a new class of disruptive technologies with rapidly incre... more Distributed energy resources (DERs) are a new class of disruptive technologies with rapidly increasing adoption levels due to favorable government policies and subsidies. However, these emerging technologies come with technical challenges for utilities and system operators; for instance, voltage rise issues in residential secondary distribution systems with high penetration of DERs. One of the low-cost mitigation options to alleviate the overvoltage problem is reactive power absorption. Nevertheless, secondary feeders exhibit a high R/X ratio more noticeably than primary distribution systems, requiring large amount of reactive power for voltage regulation that cannot be entirely provided by the DERs alone. It is also necessary to minimize the reactive power drawn from the primary distribution system to prevent any stress on the network and reduce extra system losses, while at the same time ensuring the voltage within admissible limits. To address these critical issues, this paper proposes a distributed reactive power management, where additional source is provided from inexpensive devices such as switchable shunt reactors. The proposed overvoltage mitigation is accompanied by detailed analytical investigation that estimates the minimum amount of required reactive power to manage the voltage with user specified voltage rise tolerances. Case studies have also been conducted on real residential distribution systems subjected to severe voltage rise issues provoked by large adoption of DERs.
IEEJ Transactions on Electrical and Electronic Engineering, 2016
This paper presents an efficient way of solving the distribution system reconfiguration (DSR) pro... more This paper presents an efficient way of solving the distribution system reconfiguration (DSR) problem in electrical power systems with consideration of different types of distributed generators (DGs). The objective of a DSR is to minimize the system power loss while satisfying the system constraints and keeping the topology of the system radial. In this paper, a new DSR algorithm based on a modified particle swarm optimization (PSO) is proposed to incorporate DGs with the constant voltage control mode. The proposed method is very efficient because it avoids an extra iteration loop for computing the reactive power at PV buses in order to keep the voltage at a specified magnitude. Furthermore, if the reactive power requirement is not met in between the extreme limits, the proposed algorithm strictly searches for the best possible tie switch combination to simultaneously reduce the power loss and ensure that the DGs operate in PV mode within acceptable reactive power limit. The propose...
The stochastic nature of demand and wind generation has a considerable effect on solving the sche... more The stochastic nature of demand and wind generation has a considerable effect on solving the scheduling problem of a modern power system. Network constraints such as power flow equations and transmission capacities also need to be considered for a comprehensive approach to model renewable energy integration and analyze generation system flexibility. Firstly, this paper accounts for the stochastic inputs in such a way that the uncertainties are modeled as normally distributed forecast errors. The forecast errors are then superimposed on the outputs of load and wind forecasting tools. Secondly, it efficiently models the network constraints and tests an iterative algorithm and a piecewise linear approximation for representing transmission losses in mixed integer linear programming (MILP). It also integrates load shedding according to priority factors set by the system operator. Moreover, the different interactions among stochastic programming, network constraints, and prioritized load ...
2016 IEEE International Conference on Advanced Intelligent Mechatronics (AIM), 2016
A detailed traction model for the Taipei Mass Rapid Traction system is developed, and a new speed... more A detailed traction model for the Taipei Mass Rapid Traction system is developed, and a new speed controller based on Neural Network and PID (NN-based PID) is proposed. The model, which is developed in MATLAB/ Simulink, has three main parts: traction system, third rail voltage system, and load. The train model characterizes the traction motor and the coupling effect of mechanical and electrical parts of the train system. Moreover, the efficiency changes and switching transitions can be observed. An NN-based PID controller is used because of its self-adaptive capability. A case study of an actual track is presented to demonstrate the robustness of the proposed controller.
2015 IEEE 15th International Conference on Environment and Electrical Engineering (EEEIC), 2015
This paper presents an efficient and accurate way of solving radial distribution system reconfigu... more This paper presents an efficient and accurate way of solving radial distribution system reconfiguration (DSR), which plays an important role in distribution automation for realizing smart grids. It deploys different heuristic optimization approaches to resolve the desired optimum configuration and to efficiently reconfigure the connectivity of the distribution networks. The objective is to minimize the system power loss while the voltage in each bus is limited to some allowable range, and the topology of the system is kept radial. In this paper, a hybrid algorithm consisting of particle swarm optimization (PSO) and genetic algorithm (GA) is proposed. The first part of the hybrid approach is based on a modified PSO where the initial swarm of particles fit the radiality constraint and it introduces external randomness to velocities and locations with certain probabilities when particles are in equilibrium or close to equilibrium state. The second part is a modified GA which receives its initial population from best solutions of the modified PSO and uses adaptive mutation for introducing population diversity. In addition, the particle's location in PSO and each chromosome in GA are repaired in such a way that the radiality constraint is always satisfied. The validity and the effectiveness of the proposed method has been tested using the standard IEEE 33-bus distribution network. The results show that the proposed method is robust and delivers a minimal average power loss of independent runs with reduced computational time.
2015 International Conference on Advanced Robotics and Intelligent Systems (ARIS), 2015
This paper presents a new robust methodology for solving radial distribution system reconfigurati... more This paper presents a new robust methodology for solving radial distribution system reconfiguration (DSR) problem based on the concept of cooperative multi-thread strategy and hybrid meta-heuristics. The parallel cooperative meta-heuristics (PCMH) method deploys multiple concurrent explorations of the solution space using genetic algorithm (GA), particle swarm optimization (PSO) and ant colony system (ACS) running in parallel on independent processors. The meta-heuristics are subjected to communicate and cooperate with each other synchronously at a specified interval in the course of iteration. Dynamically at each interval, the best solution so far found is exchanged among all the three processors. In addition, the worst individuals of GA are replaced by the best particles of PSO if the current optimum is delivered by PSO; otherwise the best ants from ACS replace these individuals. The proposed method is applied to the standard IEEE 33-bus distribution network with the objective of minimizing the overall power loss while at the same time accounting for the operational constraints within allowable limits. The results demonstrate the validity and the effectiveness of the proposed approach in terms of accuracy and robustness.
2018 IEEE Power & Energy Society General Meeting (PESGM), 2018
Increased environmental concerns, changing regulations, and government subsidies have played a ke... more Increased environmental concerns, changing regulations, and government subsidies have played a key role in incenting renewable generation. Solar generation has been increasingly proliferating among residential customers in many US states and Canadian provinces. Photovoltaic generation is connected through DC-AC inverters. The operation of these inverters has been a focal point of discussion in recent years. The California Independent System Operator has chaired the development of Rule 21, which was the base for the subsequent UL1741SA standard, paving the way for the upcoming revision of IEEE 1547. Canadian standards are following suit, with upcoming revisions to CSA C22.3 No 9 and C22.2 No 257. These standards require new inverters to feature autonomous functions such as Volt-Watt and Volt-VAR, as well as provision for compatibility with centralized management systems. This paper analyzes the impact of PV curtailment through the Volt-Watt function, as compared with the installation of a Battery Energy Storage System, on voltage management of one feeder of a Canadian electric utility. Technical constraints and economic factors are considered.
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