Three-phase Four-wire Distribution Feeders Research Articles

Harmonics Compensation in Three-Phase Four-Wire Distribution Feeders With a Four-Leg Structured Active Power-Line Conditioner

Harmonics Compensation in Three-Phase Four-Wire Distribution Feeders With a Four-Leg Structured Active Power-Line Conditioner

Neutral Current Reduction in Three-Phase Four-Wire Distribution Feeders by Optimal Phase Arrangement Based on a Full-Scale Net Load Model Derived from the FTU Data

An increase in the neutral current results in a malfunction of the low energy over current (LCO) protective relay and raises the neutral-to-ground voltage in three-phase, four-wire radial distribution feeders. Thus, the key point for mitigating its effect is to keep the current under a specific level. The most common approach for reducing the neutral current caused by the inherent imbalance of distribution feeders is to rearrange the phase connection between the distribution transformers and the load tapped-off points by using the metaheuristics algorithms. However, the primary task is to obtain the effective load data for phase rearrangement; otherwise, the outcomes would not be worthy of practical application. In this paper, the effective load data can be received from the feeder terminal unit (FTU) installed along the feeder of Taipower. The net load data consisting of customers’ power consumption and the power generation of distributed energy resources (DERs) were measured and transmitted to the feeder dispatch control center (FDCC). This paper proposes a method of establishing the equivalent full-scale net load model based on FTU data format, and the long short-term memory (LSTM) was adopted for monthly load forecasting. Furthermore, the full-scale net load model was built by the monthly per hour load data. Next, the particle swarm optimization (PSO) algorithm was applied to rearrange the phase connection of the distribution transformers with the aim of minimizing the neutral current. The outcomes of this paper are helpful for the optimal setting of the limit current of the LCO relay and to avoid its malfunction. Furthermore, the proposed method can also improve the three-phase imbalance of distribution feeders, thus reducing extra power loss and increasing the operating efficiency of three-phase induction motors.

Novel Simple Reactive Power Control Strategy With DC Capacitor Voltage Control for Active Load Balancer in Three-Phase Four-Wire Distribution Systems

This paper proposes a novel simple reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy may be applicable for adjustment of the source-side power factor under the balanced load condition. Only dc capacitor voltage control is used in the proposed control strategy. Therefore, the calculation blocks of the active and reactive components of the load currents are not necessary. The authors, thus, offer the simplest control strategy to control reactive power under the balanced load condition on three-phase four-wire distribution feeders. The basic principle of dc-capacitor-voltage-control-based reactive power control strategy is discussed in detail and then confirmed by digital computer simulation. A prototype experimental system was constructed and tested. Experimental results demonstrate that balanced source currents with reactive power control are achieved on three-phase four-wire distribution feeders. These experimental results also demonstrate that controlling the reactive power reduces the required power rating of the ALB compared with that of the conventional unity power factor control strategy.

Effects of a cogeneration plant on the system imbalance of a distribution feeder connected with it

This paper has evaluated the effects of a cogeneration plant on the system imbalances of a radial three-phase four-wire distribution feeder connected with it. A three-phase four-wire distribution feeder is often operated under unbalanced circumstances by reason of unequal individual phase loads. The degree of voltage and current imbalances in a three-phase four-wire feeder might be significantly enlarged while a cogeneration plant is operating in parallel. In this paper, a sample distribution feeder with a cogeneration plant connected at its end was simulated. The effects of the cogeneration plant on the voltage imbalances, current imbalances, and system loss of the specific distribution feeder were evaluated based on the simulation results. The simulation results and conclusion are of value to distribution engineers for planning and operating such a system.

Reactive power compensation and load balancing for unbalanced three-phase four-wire system by a combined system of an SVC and a series active filter

A combined reactive power compensation method of a static VAr compensator (SVC) and a series active filter is described for unbalanced three-phase four-wire distribution feeders with harmonic distortion. The SVC which consists of Δ-connected thyristor-controlled reactors, Y-connected thyristor-controlled reactors and passive filters, acts as a classic reactive power compensator for load balancing and power factor correction. The small rating active filter is used to improve the filtering characteristics of the passive filter in the SVC and suppress possible resonance between the system impedance and the passive filter. Simulation results performed by the electromagnetic transients program show that the proposed reactive power compensation configurations can effectively balance currents, correct power factor and eliminate harmonic currents.

On-line reactive power compensation schemes for unbalanced three phase four wire distribution feeders

A new reactive power compensation method is developed to reduce the negative and zero sequence components of load currents and to improve the load bus power factor of unbalanced three-phase four-wire distribution feeders. Negative and zero sequence currents may cause additional losses and damage to power systems. Load compensation at the load bus is an effective method to eliminate those undesired sequence currents. The compensation technique uses a Y-connected and a Delta -connected static reactive power compensators (SVCs) to give a different amount of reactive power compensation to each phase. The compensation formulas are very suitable for on-line control by measurement of phase voltages and currents in real time. The compensation effect can also be achieved even if one leg of the SVCs is out of service. In addition to balancing effect and power factor improvement at the load bus, the SVCs can also be used to support the load bus voltage and to maintain the substation feeder at unity power factor. Digital simulations are made with the load data measured from an 11.4 kV secondary substation feeder.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>