Dan V. Nicolae

Reconfiguration and Load Balancing in the LV and MV Distribution Networks for Optimal Performance

To get the distribution network to operate at its optimum performance in an automated distribution system reconfiguration was been proposed and researched. Considering, however, that optimum performance implies minimum loss, no overloading of transformers and cables, correct voltage profile, and absence of phase voltage and current imbalances, network reconfiguration alone is insufficient. It has to be complemented with techniques for phase rearrangement between the distribution transformer banks and the specific primary feeder with a radial structure and dynamic phase and load balancing along a feeder with a radial structure. This paper contributes such a technique at the low-voltage and medium-voltage levels of a distribution network simultaneously with reconfiguration at both levels. While the neural network is adopted for the network reconfiguration problem, this paper introduces a heuristic method for the phase balancing/loss minimization problem. A comparison of the heuristic algorithm with that of the neural network shows the former to be more robust. The approach proposed here, therefore for the combined problem, uses the neural network in conjunction with a heuristic method which enables different reconfiguration switches to be turned on/off and connected consumers to be switched between different phases to keep the phases balanced. An application example of the proposed method using real data is presented.

Analytical design and analysis of Line-Start Permanent Magnet Synchronous Motors

The Line-Start Permanent Magnet Synchronous Motor (LSPMSM) attracted a considerable attention because of the higher value of the product between the power factor and the efficiency. The paper proposes an analytical design method for the LSPMSM, considering the asynchronous starting and the synchronous steady state parameters. Using this theoretical approach, all the synchronous and asynchronous starting characteristics will be calculated. The design of a motor having the following specifications: rated output power 3.5 kW, rated voltage 200 V, rated frequency 50 Hz, rated speed 3000 rpm is presented.

Reversible DC-to-DC converter for a dual voltage automotive system using zero voltage switching technique

A novel hysteretic controller for a bi-directional dc-dc converter with ZVS and interleaving for dual voltage systems in automobiles is presented. A variable frequency extended band hysteretic current control method is proposed. In comparison with classical fixed frequency current control PWM, the reverse polarity peak current needed for ZVS operation is kept constant. Inductor current ripple decreases with load reduction. Automatic changes in operation between buck and boost modes are accomplished without transient currents. Converter simulations are carried out using Matlab/Simulink platform.

Load balancing in distribution feeder through reconfiguration

The electrical distribution system is to ensure that an adequate supply is available to meet the estimated load of the consumers in both the near and more distant future. This must of course, be done for minimum possible cost consistent with satisfactory reliability and quality of the supply. In order to avoid excessive voltage drop and minimize technical loss, it may be economical to install apparatus to balance or partially balance the loads. It is believed that the technology to achieve an automatic load balancing lends itself readily for the implementation of different types of algorithms for automatically rearranging the connection of consumers on the low voltage and of a feeder for optimal performance.

Multilevel high power converters for reversible power flow between utilities and power pool transmission corridor

Multilevel converters have emerged as the state of the art high power conversion for applications in reversible power flow. Electric power could be tapped from or injected to the grid regardless of the discrepancies in voltage levels, frequency, phase number and different modes of operation of the grid and the system. This paper presents an overview of different topologies of multilevel converters and modulation strategies with a verification of back-to-back neutral point converter for bi-directional power flow application.

A Study of Improving the Power Factor of a Three-Phase Induction Motor Using a Static Switched Capacitor

In this paper a static switched capacitor with an auxiliary three-phase stator winding, which is only magnetically coupled to the stator main winding, is explored for improving the starting and operating power factor of a three-phase induction motor. The scheme improves the power factor of the motor without compromising significantly on other performances. Important advantages of the scheme include preventing harmonics in the line current, and eliminating regeneration possibility as well as preventing high inrush currents at starting

Control algorithm of a smart grid device for optimal radial feeder load reconfiguration

Secondary distribution network, generally speaking, performs as well as the performance of its LV feeders. The main problem a feeder is experiencing is the load unbalancing due to the stochastic nature of its individual single-phase loads: bigger losses in certain phase accompanied with bed voltage regulation and voltage unbalance. The aim of this paper is to address the issue of automatic balancing as progressing from the end of the feeder towards the front using smart device based on three-ways switch selector and artificial intelligence algorithm to minimize the neutral current.

Phase load balancing in the secondary distribution network using a fuzzy logic and a combinatorial optimization based on the Newton Raphson

The electrical network system is to ensure that an adequate supply is available to meet the estimated load of the consumers in both the near and more distant future. This must of course, be done for minimum possible cost consistent with satisfactory reliability and quality of the supply. In order to avoid excessive voltage drop and minimize loss, it may be economical to install apparatus to balance or partially balance the loads. It is believed that the technology to achieve an automatic load balancing lends itself readily for the implementation of different types of algorithms for automatically rearranging the connection of consumers on the low voltage and of a feeder for optimal performance. In this paper the combination of the fuzzy logic with Newtown Raphson as optimization method are been implemented to balance the load in the secondary part of the transformer.

Improving three-phase induction machines power factor using single phase auxiliary winding fed by an active power filter

This paper presents a three-phase induction machine that employs a single phase auxiliary winding, which is only magnetically coupled to the stator main winding, and controlled by an active power filter. The active filter consists mainly of a two leg PWM voltage source inverter, which together with the auxiliary winding serves to supply leading reactive power to the machine. With sufficient ampere-turn capability of the auxiliary winding and an adequate control algorithm, the computer simulation results show that it is possible to obtain nearly unity power factor operation at the terminals of the main winding over a range of load conditions including rated load. The simulated power factor of this scheme is compared with the measured result for a typical practical induction motor.

Phase load balancing in the secondary distribution network using fuzzy logic

The electrical network system is to ensure that an adequate supply is available to meet the estimated load of the consumers in both the near and more distant future. This must of course, be done for minimum possible cost consistent with satisfactory reliability and quality of the supply. In order to avoid excessive voltage drop and minimize loss, it may be economical to install apparatus to balance or partially balance the loads. It is believed that the technology to achieve an automatic load balancing lends itself readily for the implementation of different types of algorithms for automatically rearranging the connection of consumers on the low voltage and of a feeder for optimal performance. In this paper the fuzzy logic is been implemented to balance the load in the secondary part of the transformer.