Jizhong Zhu

Optimal generation scheduling based on AHP/ANP

This paper proposes an application of the analytic hierarchy process (AHP) and analytic network process (ANP) for enhancing the selection of generating power units for appropriate price allocation in a competitive power environment. The scheme addresses adequate ranking, prioritizing, and scheduling of units before optimizing the pricing of generation units to meet a given demand. In the deregulated environment, the classical optimization techniques will be insufficient for the above-mentioned purpose. Hence, by incorporating the interaction of factors such as load demand, generating cost curve, bid/sale price, unit up/down cost, and the relative importance of different generation units, the scheme can be implemented to address the technical and nontechnical constraints in unit commitment problems. This information is easily augmented with the optimization scheme for an effective optimal decision. The scheme proposed is tested using the IEEE 39-bus test system.

Optimal VAr pricing and VAr placement using analytic hierarchical process

This paper proposes a new method to study reactive power pricing and new VAr source selection using the analytic hierarchical process (AHP), and presents a price structure for providing reactive power service and control based on the OPF approach. The cost of reactive power support service is determined based on capability and contribution to improvement of system performance such as security, reliability and economics, by calculating sensitivity of objective function with respect to reactive power support. For VAr planning purpose, an analytic hierarchical process model is devised which comprehensively considers the network topology and all types of benefits including operating cost, system voltage and loss for each candidate VAr source site. The proposed approach for calculating VAr pricing and selecting the new VAr sources was tested on an IEEE 30-bus system. The calculation results are analyzed by the cost-benefit analysis (CBA) method.

Multi-area power systems economic dispatch using nonlinear convex network flow programming

Abstract This paper presents a new nonlinear convex network flow programming (NLCNFP) model and algorithm for solving the security-constrained multi-area economic dispatch (MAED) problem. The tie-line security and transfer constraints in each area are considered in the MAED model. A simple analysis of a buying and selling contract in a multi-area environment is also made. The NLCNFP model of security-constrained multi-area economic dispatch was set up and solved by using a combined method of quadratic programming (QP) and network flow programming (NFP). The concept of maximum basis in the network flow graph was introduced to change the constrained model into an unconstrained QP model, which was easily solved by the reduced gradient method. The proposed approach is tested on a system of four interconnected areas with satisfactory results.

Application of AHP/ANP to unit commitment in the deregulated power industry

This paper proposes an application of the analytic hierarchy process (AHP) and analytic network process (ANP) for enhancing the selection of generating power units for appropriate price allocation in a competitive power environment. The scheme addresses adequate ranking, prioritizing and scheduling of units before optimizing the pricing of generation units to meet a given demand. In the deregulated environment the classical optimization techniques will be insufficient for the above-mentioned purpose. Hence by incorporating the interaction of factors such as load demand, generating cost curve, bid/sale price, unit up/down cost, and the relative importance of different generation units, the scheme can be implemented to address the technical and nontechnical constraints in unit commitment problems. This information is easily augmented with the optimization scheme for an effective optimal decision. The scheme proposed is tested using the IEEE 39-bus test system.

A new approach to optimal power flow with phase shifter

This paper presents an integrated approach to study the optimal power flow (OPF) with phase shifter for alleviating line overloads. It is noted that the general OPF calculations are hourly based and the control variables of OPF are continuous. However, the calculations of phase shifter are daily based, and the variable of phase shift is discrete as well as the numbers of allowable adjustments for each phase shifter per day are also discrete. The proposed scheme uses the rule-based method to bridge the problems. The hourly based OPF solution will be sent to rule based system to check the phase shifter constraints. Meanwhile, the rule based system will transfer the available phase shifter control as input to OPF. The OPF hourly based is solved by the extended quadratic interior point method. The proposed approach is tested on the IEEE 30-bus system with 4 phase shifters.

A new approach to VAr pricing and control in the competitive environment

The paper develops a price structure for providing reactive power service and control based on optimal power flow (OPF) approach. The cost of reactive power support service is determined based on capability and contributions to the improvement of system performance such as security, reliability and economics, by computing sensitivity of objective function with respect to reactive power support. The OPF model, in which the objective function is minimization of system loss, is solved by the interior point approach. For VAr planning purpose, three parallel indices are first presented to determine the sites of new VAR sources, based on the cost benefit analysis, the sensitivity method and the voltage security margin method. Then, the analytic hierarchical process is used to comprehensively consider the effect of three indices and the network topology for each candidate VAr source site. The proposed approach was tested on an IEEE 30 bus system with satisfactory results.

Optimal load shedding study of naval-ship power system using the Everett optimization technique

Abstract This paper reports an application of the Everett optimization technique for value-based load shedding in naval-ship power system with network constraints and application of reliability constraints. A new congestion analysis index—expected contingency margin (ECM), which considers the probability of disturbance, and reliability indices loss of load probability (LOLP) and expected unserved energy (EUE) are presented to filter the critical outage and congestion cases. The optimal load shedding scheme carried out using the Everett optimization technique uses a utility function, which addresses the cost of allocating pay-off while satisfying the network and reliability constraints and generation capacity limits. The algorithm search for the optimal λ to form a fair pricing mechanism, which produces maximum pay-off and minimum load shedding while, satisfying system constraints. The proposed approach is examined on naval-ship power system and detailed results are shown.

Optimal Allocation with Network Limitation for Autonomous Space Power System

A new approach is presented to congestion analysis and optimal load shedding for aerospace power systems. Optimal powere ow,ananalytichierarchicalprocess,and theEverett optimization method (Everett,H., Operations Research, Vol. 11, 1963, pp. 399 ‐417) are employed for implementing this approach. Several system performance indices are developed to evaluate the degree of system congestion for different operation time stages. These performance indices include a circuit overload index and a system voltage problem index obtained through the optimal powere owcalculation.Thecongestedsystemisalleviatedby theavailablecontrolsuchasloadshedding.Therefore, themathematicalmodelofloadshedding,inwhichtheobjectiveisapayofffunction,isdevised.Thesolutionmethod of the model is the Everett method, generalized Lagrange multipliers. Detailed results are given in the paper.

Multiple indices for optimal reactive power pricing and control

Abstract An integrated approach for reactive power price and control is developed. Reactive power price is divided into fixed and variable parts. The fixed part is the operational cost of reactive power service. The variable part of reactive power price is determined based on capability and contributions to the improvement of system performance such as security, reliability and economics. These contributions can be evaluated by computing sensitivity of objective function with respect to reactive power support. The optimal power flow (OPF) approach is used to carry out this purpose. For VAr planning (or control) purposes, three parallel indices are first presented to determine the sites of new VAr sources. They are benefit-to-cost ratio index, voltage reactive sensitivity index, and the bus voltage security index. The analytic hierarchical process is then used to comprehensively consider the effect of the three indices and the network topology for each candidate VAr source site. The proposed approach was tested on an IEEE 30-bus system with satisfactory results.

Aerospace power system automation—using Everett method

This paper studies aerospace power system automation using the optimal power flow (OPF) and Everett method. Several system performance indices are developed to evaluate the degree of system congestion for different operation time stages. These performance indices include a circuit overload index and a system voltage problem index and obtained through the OPF calculation. The congested system is alleviated by the available control such as load shedding. In order to reach this objective, the mathematical model of load shedding, in which the objective is payoff function, is devised. The Everett method—Generalized Lagrange Multipliers is employed to solve the problem. The results on NASA power system and IEEE-30 bus test system are given in the paper.