This paper maps the expected and possible adverse consequences for power quality of introducing several smart distribution-grid technologies and applications. The material presented in this paper is ...the result of discussions in an international CIGRE-CIRED joint working group. The following technologies and applications are discussed: 1) microgrids; 2) advanced voltage control; 3) feeder reconfiguration; and 4) demand-side management. Recommendations are given based on the mapping.
The possibility of leveraging the data provided by smart meters to understand the load characteristics is studied in this paper. The loads are modeled as voltage-dependent elements to increase the ...accuracy of volt-VAR optimization (VVO) techniques for distribution systems. VVO techniques are part of the distribution management system and may be used for purposes such as loss reduction, voltage profile improvement, and conservation voltage reduction. A deterministic framework is proposed that formulates the VVO problem as a mixed-integer quadratically constrained programming problem, which is solved efficiently using advanced branch-and-cut techniques. The proposed framework is capable of optimally controlling capacitor banks, voltage regulators, and under-load tap changers (ULTCs) for day-ahead operation planning. The results indicate that loss reductions of up to 40% and a total demand reduction of up to 4.8% are achievable under some loading conditions in a radial test system. The effect of the load voltage dependence is also demonstrated through analytical simulations.
Voltage regulation in distribution networks is challenged by increasing penetration of distributed energy resources (DERs). Thanks to advancement in power electronics, DERs can be leveraged to ...regulate the grid voltage by quickly changing their reactive power outputs. This paper develops a hybrid voltage control (HVC) strategy that can seamlessly integrate both local and distributed designs to effectively coordinate the network-wide DERs. By minimizing a special voltage mismatch objective, we achieve the proposed HVC design by adopting partial primal-dual gradient updates that can allow for a distributed and online implementation. The proposed HVC design improves over existing distributed approaches by reliably integrating local voltage feedback. As a result, it can dynamically adapt to varying system operating conditions while being fully cognizant of the instantaneous availability of communication links. Under the worst-case scenario of total link outages, the proposed design naturally boils down to a surrogate local control implementation. Numerical tests on realistic feeder cases have been made to corroborate our analytical results and demonstrate the algorithmic performance.
Training intensity distribution is important to training program design. The zones 1 to 2 boundary can be defined by the Talk Test and the rating of perceived exertion. The zones 2 to 3 boundary can ...be defined by respiratory gas exchange, maximal lactate steady state, or, more simply, by critical speed (CS). The upper boundary of zone 3 is potential defined by the velocity at maximum oxygen uptake (vVO2max), although no clear strategy has emerged to categorize this intensity. This is not normally definable outside the laboratory.
This study predicts vVO2max from CS, determined from 1 (1.61 km) and 2 (3.22 km) citizen races in well-trained runners.
A heterogeneous group of well-trained runners (N = 22) performed 1- and 2-mile races and were studied during submaximal and maximal treadmill running to measure oxygen uptake, allowing computation of vVO2max. This vVO2max was compared with CS.
vVO2max (4.82 0.53 m·s-1) was strongly correlated with CS (4.37 0.49 m·s-1; r = .84, standard error of estimate SEE = 0.132 m·s-1), 1-mile speed (5.09 0.51 m·s-1; r = .84, SEE = 0.130 m·s-1), and 2-mile speed (4.68 0.49 m·s-1; r = .86, SEE = 0.120 m·s-1).
CS, calculated from 2 citizen races (or even training time trials), can be used to make reasonable estimates of vVO2max, which can be used in the design of running training programs.
This article proposes a two-stage optimization strategy for solving the voltage-var optimization (VVO) problem considering stochastic penetration of plug-in electric vehicles (PEVs) to unbalanced, ...three-phase power distribution networks (PDN). The optimization strategy considers the prospect of forced active power curtailment at a minimized level, bidirectional PEVs activities. It also includes simple tap operations of shunt capacitor banks, online tap changing transformers, and voltage regulators to achieve optimal economic gain while satisfying the VVO operational constraints. The first stage aims for the optimal decomposition of the PDN into well-defined, cross-checked smaller partitions via a proposed community-based detection particle swarm optimization algorithm. The second stage incorporates a mixed-integer linear programming formulation to solve the VVO problem per partition level. This is done considering the nonlinearity and nonconvexity of the electrical system via applied approximation. This reduces the complexity and computational burdens that usually arise in solving the problem on a larger scale. The proposed two-stage strategy was tested on the modified IEEE 123 bus system with various case scenarios. Economical operation of the PDN is achieved during peak demand hours while maintaining a safe operation within the VVO problem.
This work proposes a novel zone-based multistage "time-graded" operation of cascaded on-load tap changing transformers, capacitor banks, and step voltage regulators in the presence of large-scale ...photovoltaic (PV) sources. A multistage Volt-VAr optimization (VVO) algorithm is proposed to regulate the voltage in a medium voltage unbalanced distribution system while trying to relax the tap/switch operations of regulators that are cascaded in series, and minimize the curtailment of PV inverter output. A linearized power system model is formulated and a mixed-integer quadratic programming solver is utilized to solve the subobjective optimization at each stage in near to real time. The multistage coordinated operations are performed successively based on the regulator zones starting from the zone nearest to the substation, to achieve the overall voltage regulation of the system. Simulation studies were performed for various scenarios of PV and load profile variations. A comparison study between the novel multistage VVO and a multiobjective VVO was done to observe the convergence performance. Results show the efficient usage of the conventional voltage regulating devices along with minimal power curtailment from PVs when required.
This study proposes a strategy for coordinated operation of networked microgrids (MGs), distributed energy resources (DERs), and volt-VAR control devices in the implementation of volt-VAR ...optimisation (VVO). The authors’ formulation is focused on implementing conservation voltage reduction, although it can be extended for any other VVO problems. They consider the voltage–power control modes of DERs contemplated in IEEE Std. 1547, namely, constant power factor, voltage–reactive power, active–reactive power, and constant reactive power. DERs are considered at the distribution network (DN) and within the MGs. The problem is formulated as a bi-level optimisation problem where the DN operator (DNO) is in the upper-level and each MG in the lower-level. The DNO and each MG are assumed to be players with their individual objective functions. Finally, they validate their formulation in two test systems: a 9-node system and a modified IEEE 33-node system. On average the proposed method can improve the efficiency of the grid by 4% compared to the economic operation scenario. The results of the study show that the different control modes of the DERs can have better performance depending on the objective of the VVO formulation. The findings of this study are compelling for the implementation of VVO in active distribution systems with networked MGs.
Today, the evolution of smart grid, electric vehicles (EVs) with voltage to the grid mode, and deployment of renewable energy sources (RESs) are bringing revolutionary changes to the existing ...electrical grid. Volt-VAR optimization (VVO) is a well-studied problem, for bringing solutions to reduce the losses and demand along the distribution lines. The current VVO, however, does not acknowledge the role of elastic and inelastic loads, EVs, and RESs to reduce the reactive power losses and hence the cost of generation. We propose a mathematical model Volt-VAR and CVR optimization (VVCO)/optimal energy consumption model (OECM) to solve the VVO problem by considering load shifting, EV as the storage and carrier of the energy, and use of RES. The VVCO/OECM not only reduces the reactive load but also flatten the load curve to reduce the uncertainty in the generation and to decrease the cost. The system also considers the efficiency of the electrical equipment to enhance the lifetime of the devices. We develop a non-cooperative game to solve the VVCO/OECM problem. To evaluate the performance, we simulate the VVCO/OECM model and compare with the existing VVO solution. We found that our method took almost a constant time to produce a solution of VVO regardless of the size of the network. The proposed method also outperform the existing VVO solution by reducing the generation cost and flatten the load and minimizes the uncertainty in the power generation. Results have shown that exploiting RES will reduce the voltage drop through reducing the injection of reactive power to the system.
This paper presents an implementation of an IEC 61850-based real-time co-simulation platform for verification of the performance of a volt-VAR optimization (VVO) engine for smart distribution ...networks. The proposed VVO engine is able to minimize grid loss, volt-VAR control asset operational costs, and conservation voltage reduction operational costs through its comprehensive objective functions, weighted by fuzzification using advanced metering infrastructure (AMI) data. The optimization engine receives the AMI data stream through measurement aggregators. Moreover, it sends control commands to volt-VAR control components modeled in real-time digital simulator (RTDS) through DNP.3 protocol. To check the performance and the precision of proposed VVO, a fault scenario is imposed upon the system. IEC 61850 GOOSE messages are generated and sent to change the status of specified breakers, while the VVO engine receives system reconfiguration commands via IEC61850 Manufacturing Message Specification (MMS) protocol. The results of the study on 33-node feeder showed adequate performance of proposed VVO in grid operating scenarios.
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