Hung-Lu Wang

An Improved Backward/Forward Sweep Load Flow Algorithm for Radial Distribution Systems

This letter presents an improved backward/ forward sweep algorithm for three-phase load-flow analysis of radial distribution systems. In the backward sweep, Kirchhoffs Current Law and Kirchhoffs Voltage Law are used to calculate the upstream bus voltage of each line or a transformer branch. Then, the linear proportional principle is adopted to find the ratios of the real and imaginary components of the specified voltage to those of the calculated voltage at the substation bus. In the forward sweep, the voltage at each downstream bus is then updated by the real and imaginary components of the calculated bus voltage multiplying with the corresponding ratio. The procedure stops after the mismatch of the calculated and the specified voltages at the substation is less than a convergence tolerance. The proposed algorithm is tested with three IEEE benchmark distribution systems. Results show that the algorithm is accurate and computationally efficient in comparing with two other commonly used methods

Passive Harmonic Filter Planning in a Power System With Considering Probabilistic Constraints

This paper presents a new method for planning single-tuned passive harmonic filters to control harmonic voltage distortion throughout a power system. In the problem, the probabilistic characteristics of the harmonic source currents and network harmonic impedances in the filter planning are taken into account. The objective is to minimize the total filter installation cost, while the harmonic voltage limits and filter component constraints are satisfied with predetermined confidence levels. To obtain the optimal size of each filter component of the planning problem, the proposed procedure is first to find the candidate filter buses based on the sensitivity analysis. Next, the formulated probability-constrained problem is transformed into a deterministic nonlinear programming problem and is solved by a genetic-algorithm-based optimizer. The proposed solution procedure is tested with an actual distribution network and is verified by the conventional deterministic approach and by the Monte Carlo simulation. Numerical experiences show that the proposed method yields favorable results compared with the other two approaches.

Strategic placement and sizing of passive filters in a power system for controlling voltage distortion

This paper presents an approach for determining optimal or near-optimal locations and sizes of single-tuned passive harmonic filters among existent capacitor busses in a power system. The objective of the harmonic filter planning is to control the system-wide voltage distortion, while individual/total harmonic voltage distortion limits at each network bus, and the filter component limits are considered as constraints. The tuned frequency deviation of the filter caused by component manufacturing errors and environment is also taken into account in the problem. The proposed two-phase planning procedure is first to formulate an unconstrained optimization problem for placement of the filters based on sensitivity analysis. Next, a constrained problem is formulated and is solved by a genetic algorithm-based optimizer. The proposed method is tested with an actual distribution system. Test results show that the method is effective, computationally robust, and suitable for passive filter planning in a power system.

Sensitivity-based approach for passive harmonic filter planning in a power system

This paper presents a study of passive harmonic filter planning in the power system. The purpose is to find the optimal locations for harmonic filters among existing capacitor buses in the power network, based on sensitivity analysis. The planning problem is formulated as an unconstrained optimization problem. The inductor size of each shunt filter is then determined while IEEE-519 recommended harmonic voltage and voltage distortion limits are maintained at each network bus. Simulation results obtained by testing a distribution system show that the proposed approach is robust, computationally efficient and suitable for siting and sizing passive harmonic filters.

A new approach for placement of single-tuned passive harmonic filters in a power system

The purpose of this paper is to present a new method for determining locations of single-tuned passive harmonic filters in a power system. The harmonic filter planning is for controlling the system-wide voltage distortion while against individual and total harmonic distortion limits at each network bus as well as filter component limits. The planning problem is formulated as a constrained optimization problem, and is then solved to find the optimal size of each filter component. The proposed method has been tested with an actual system. Test results show that the method is effective, computationally robust, and suitable for passive filter planning in a power system.

A Simplified Forward and Backward Sweep Approach for Distribution System Load Flow Analysis

This paper presents a simplified forward and backward approach for load flow analysis in radial distribution system. The proposed method includes two phases. At Phase I (forward sweep), the KCL and KVL are used to find the calculated voltage for each bus located at upstream of each line segment or transformer. At Phase II (backward sweep), the linear proportion concept for real and imaginary decomposition is adopted to find the ratios of real and imaginary parts of specified voltage to the calculated voltage at each upstream bus. Then, the voltage at each downstream bus is updated by real and imaginary parts of initial or calculated voltage multiplying with the corresponding ratios, respectively. The solution procedure is terminated after the mismatch of calculated voltage and specified voltage of substation is less than the tolerance value. The proposed method is tested with three IEEE distribution benchmark systems. Results show that the proposed method is effective, computationally robust, and faster than conventional forward/backward sweep and the ladder iteration method.

A new method of passive harmonic filter planning for controlling voltage distortion in a power system

This paper presents a new method for planning single-tuned passive harmonic filters to control harmonic voltage and voltage distortion throughout a power system. Several alternative objective functions are considered as performance indices in the filter planning problem while the IEEE-519 individual and total harmonic voltage distortion limits at each network bus, as well as filter component limits, are modeled as constraints. The tuned frequency deviation of the filter caused by component manufacturing errors and environmental changes is also taken into account. To solve the problem, a two-step procedure is first proposed to place the filters. Next, the planning problem is formulated as a constrained optimization problem for minimizing the defined network objective function and is then solved by a genetic algorithm-based optimizer to obtain the optimal size of each filter component. The usefulness of the proposed method is tested with an actual distribution network. Results show that the method is effective, computationally robust, and is suitable for the passive filter planning in a power system.

The Average Intensity of Illumination and the Power Optimization

This paper presents a set of calculation ways in which fast illumination is designed. Its method utilize the concept of average intensity of illumination, derive one group that appear lighting calculate formulae fast, and utilize optimization model, determine to offer the number of lamps and lanterns taking saving the electric energy as goal. For the purpose to input the data for being convenient and easy to understand the results, utilize MATLAB procedure language and GUIDE to write a design users interface for the average intensity of illumination and power optimization. Utilize the single interface to do different changes, operate interfaces simple and easy to understand, and enable users to obtain optimization and design the result fast.

A fuzzy-based algorithm for shunt capacitor planning in a distorted power system

This paper presents a fuzzy-based algorithm for the placement and sizing of shunt capacitor banks in a harmonics-polluted distribution system. In the problem the objective function is the total system power loss and the capacitor installation cost, while the constraints are the rms voltage, the individual and total harmonic voltage distortion limits at each bus, and the limit of the available capacitor units to be placed. In the study the power loss index associated with each bus, the rms voltage, the individual and total harmonic voltage distortions at each bus, and the capacitor site suitability are modeled as fuzzy membership functions. A useful solution algorithm is then proposed to find the most suitable capacitor locations and corresponding sizes for an actual distribution network. Results obtained by the proposed approach are compared with those obtained by a traditional nonlinear programming method and a maximum sensitivity-based approach. Numerical experiences show that the proposed method yields favorable results for the capacitor planning problem.

Probabilistic Approach for Passive Harmonic Filter Planning in a Power System

This paper presents a new method with considering the probabilistic characteristics of harmonic current sources for single-tuned harmonic filter planning in the power system. The filter planning problem is formulated as an unconstrained optimization problem. The objective is to minimize the voltage distortion throughout the system while determining the optimal filter locations and sizes. The usefulness of the proposed approach is test by an actual distribution system. Results show that the proposed method is robust and computationally efficient.