Three-phase Four-wire Distribution System Research Articles

Power Quality Improvement on 11kV/440V Distribution System using DSTATCOM

At the PCC and source side, current and voltage harmonics are compensated by utilizing a distribution static compensator. In this work, we also compensated for voltage control and reactive power correction. An improved reference current switching signal is suggested using a synchronous reference frame control technique. The analysis is done on an 11kV/440V three-phase four-wire unbalanced nonlinear load distribution system. The DC link voltage and harmonic reduction of the suggested distribution system performance is compared with the PI and fuzzy logic controllers. Harmonic distortion is reduced, and reactive power is successfully compensated with the suggested method. These simulation results are obtained by MATLAB/SIMULINK software.

A Hybrid Compensator for Unbalanced AC Distribution System With Renewable Power

A hybrid compensator with a new coordinated control is proposed for mitigating power quality aspects and integration of renewable power in an unbalanced three-phase four-wire distribution system. The proposed compensator comprises of thyristor switched capacitor (TSC) banks, delta connected thyristor controlled reactor (TCR), a 3rd and a 5th harmonic tuned passive LC filter & a low rating three-phase four-wire D-STATCOM. The TSC-TCR operates asymmetrically for the base var compensation and also eliminates negative sequence current during unbalanced loading at the point of common coupling (PCC). The D-STATCOM works in coordination with the TSC-TCR and the passive filters to compensate fundamental var, zero sequence current, voltage flicker & 7th harmonic currents at the PCC. The D-STATCOM thus serves as a supportive var compensator as well as an active filter in selective harmonic compensation mode, thereby improving the var compensation and harmonic current filtering at the PCC. A new coordination control system is proposed to control the operation of the D-STATCOM which is also employed to integrate a PV source & a doubly fed induction generator (DFIG) based wind energy conversion system (WECS) to the PCC. This scheme with grid connected and islanded mode of operation using D-STATCOM exhibits low-voltage ride-through capabilities. Further, the chance of resonance of the passive filters used with source inductance is eliminated in the proposed scheme. Simulation results show that the proposed hybrid system effectively compensates var, negative & zero sequence current, reduces voltage flicker and harmonic currents at PCC.

Cone-structured seven-level boost inverter topology for improvising power quality using online monitoring controller scheme for DSTATCOM application

In this article, a seven-level triple-time voltage-boosting topology (8S7L-TTB) is proposed, which has eight switches as the minimum. This topology is used as DSTATCOM to eliminate power-quality issues. In a three-phase four-wire distribution system, specific unpredictable issues have emerged through the increase of unbalanced linear and non-linear loads, which has caused various drawbacks such as voltage imbalance, poor voltage regulation, increased reactive components, and harmonics generation, through which the life period of the system has been minimized, undesirable heating has been produced, and the RMS voltage has been reduced. Hence, it is highly essential to eliminate the issues as mentioned earlier. In this research, a PV-based DSTATCOM is introduced for online-monitoring adaptive Chebyshev neural network controller with triple-boost inverter topology. The three-phase system’s D-Q components, which have been continuously extracted under instant-loading conditions, and the reference magnitude, have been compared through the proposed controller. The error signal is received from the adaptive Chebyshev neural network controller, through which the proposed inverter-switching devices are triggered with multi-carrier pulse width-modulation technique are used to compute the THD of 2.79%. Furthermore, this proposed seven-level inverter and controller have solved the aforementioned problems and maintained the floating capacitor’s voltage nearly as similar as the source voltage in different loading conditions to ensure the efficiency of the system is at 96.82%. To ensure its suitability in real-time, the proposed controller is simulated with MATLAB software and validated through the downscale experimental setup and the results are observed.

Mitigation of Harmonics in Neutral Conductor for 3-Phase 4-Wire Distribution Systems

Three-phase four-wire distribution systems are very common and widely used in commercial and industrial installations and therefore power systems harmonics is an area that merits a great deal of attention.

Enhanced controller for a four-leg inverter operating in a stand-alone microgrid with unbalanced loads

<span lang="EN-US">Stand-alone low voltage (LV) microgrids supplying small local loads far from the utility grid are becoming an increasingly popular alternative to a total reliance on the centralized utility grid. In most of LV microgrids, three-phase four-wire distribution systems are used to supply both single- and three-phase loads. Unequal distribution of loads can result in voltage unbalance problems. The use of the four-leg inverter is one of the best solutions for providing a neutral current path and compensating unbalanced load conditions in stand-alone LV microgrids. This paper proposes a fast control technique to compensate unbalanced voltage conditions for a four-leg inverter operating in a stand-alone LV microgrid. The suggested technique provides the current controller’s orthogonal component without introducing any additional dynamics or distortions. The major benefits of the recommended per-phase control technique over conventional orthogonal signal generation (OSG) methods are enhanced steady-state and dynamic performances as well as independency to the system parameters. Several simulation results are provided to confirm the superior performance of the suggested methods.</span>

Experimental Validation of Photovoltaic System with Isolated Dual Inductor dc-dc Converter for Grid-Connected Application

Abstract This article presents a double inductor–based converter for a grid-connected photovoltaic (PV) system with the utilization of the battery bank. This converter used to give continuous power to the three-phase four-wire power distribution system from the PV array. In order to increase the low magnitude of the PV array output voltage into a high dc voltage required for the three-phase dc link, the proposed system offers two boost stages. The double inductor–based converter gives power to the load in both the switched ON and OFF conditions of the chopping switch over buck, boost, and Cuk converters utilized in the PV-coordinated grid-connected applications. The operations of the proposed double inductor–based converter sustained three-phase four-wire power distribution system are analyzed and presented. The digital simulation and hardware experimental prototype results are presented to examine the performance of the presented double boost converter fed to the three-phase four-wire power distribution system.

Dynamic Voltage Restorer Integrated with Photovoltaic-Thermoelectric Generator for Voltage Disturbances Compensation and Energy Saving in Three-Phase System

The dynamic voltage restorer (DVR) combined with a photovoltaic–thermoelectric generator (PV-TEG) system is proposed for voltage disturbance compensation in the three-phase four-wire distribution system. The PV-TEG hybrid energy source is used in the DVR system to improve the system ability for deep and long-period power quality disturbance compensation. In addition, the DVR will save grid energy consumption when the hybrid PV-TEG module generates sufficient power to meet the load demand. An enhanced variable factor adaptive fuzzy logic controller (VFAFLC)-based maximum power point tracking (MPPT) control scheme is proposed to extract the maximum possible power from the PV module. Since the PV and TEG combine a hybrid energy source for generating power, the DVR can work efficiently for the voltage sag/swell, outage compensation, and energy conservation mode with minimum energy storage facilities. The in-phase compensation method and the three-leg voltage source inverter (VSI) circuit are chosen in the present system for better voltage and/or power compensation. To confirm the effectiveness of the proposed hybrid PV-TEG integrated DVR system, a simulation-based investigation is carried out with four different operational modes with MATLAB software. The study results confirm that the proposed DVR system can compensate power quality disturbances of the three-phase load with less total harmonics distortion (THD) and will also work efficiently under energy conservation mode to save grid energy consumption. Moreover, the proposed VFAFLC-based control technique performs better to achieve the maximum power point (MPP) quickly and accurately, thereby improving the efficiency of the hybrid energy module.

Power Quality Improvement for Grid-connected PV System Based on Distribution Static Compensator with Fuzzy Logic Controller and UVT/ADALINE-based Least Mean Square Controller

This paper presents a novel method of power quality enrichment in a grid-connected photovoltaic (PV) system using a distribution static compensator (DSTATCOM). The paper consists of two-step control processes. In the primary step, a fuzzy logic controller (FLC) is employed in the DC-DC converter to extract the peak power point from the PV panel, where the FLC produces a switching signal for the DC-DC converter. In the secondary step, a unit vector template (UVT)/adaptive linear neuron (ADALINE)-based least mean square (LMS) controller is adopted in the DC-AC converter, i.e., voltage source converter (VSC). The input to this VSC is the boosted DC voltage, which originates from the PV panel as a result of DC-DC conversion. The VSC shunted with the power grid is known as a DSTATCOM, which can maintain the power quality in the distribution system. The UVT controller generates reference source currents from the grid voltages and DC-link voltages. The ADALINE-based LMS controller calculates the online weight according to the previous weights by the sensed load current. The UVT/ADALINE-based LMS controller of a DSTAT-COM performs several tasks such as maintaining the sinusoidal source current, achieving a unity power factor, and performing reactive power compensation. The reference current extracted from the UVT/ADALINE-based LMS controller is fed to the hysteresis current controller to obtain the desired switching signal for the VSC. A 100 kW solar PV system integrated into a three-phase four-wire distribution system through a four-leg VSC is designed in MATLAB/Simulink. The performances of the FLC and UVT/ADALINE-based LMS controllers are demonstrated under various irradiances as well as constant temperature and nonlinear loading conditions.

A complete state estimation algorithm for a three-phase four-wire low voltage distribution system with high penetration of solar PV

Low Voltage Distribution Grids (LVDGs) become highly unbalanced due to the advent of single-phase solar PV plants. As a result, the voltage and current levels of the neutral conductor show a significant increase. Therefore, monitoring of the entire state of the network is essential. However, the existing state estimation algorithms estimate voltage states of the phase conductors while ignoring the state of the neutral conductor. This paper presents a novel approach to estimate the complete state of the LVDGs. A novel state reduction method was introduced to model the three-phase four-wire feeder line using a 3×3 admittance matrix, which incorporates the neutral coupling effect on phase conductors. Next, the reduced admittance matrix together with the linear approximations of active and reactive power functions were combined to formulate the Low Voltage-Linear State Estimation (LV-LSE) algorithm. Finally, the performance of LV-LSE algorithm was analyzed for different measurement uncertainties, scales of line lengths of the network, and data-loss conditions. Results show that, for all the cases, LV-LSE algorithm together with the proposed reduction method can estimate voltage states with an average maximum voltage magnitude error of less than 4.32×10-3 pu and current states with an average maximum current magnitude error of less than 1.81×10-3 pu.

Performance Analysis of ANN Based three-phase four-wire Shunt Active Power Filter for Harmonic Mitigation under Distorted Supply Voltage Conditions

This paper presents the design and implementation of three-phase four-wire shunt active power filter (SAPF). It consists of insulated gate bipolar transistors, IGBT based current-controlled voltage source inverter (CC-VSI), series coupling inductor and self-supported DC bus. Power electronics based converters and non-linear loads generate waveform-driven power quality issue as harmonics. Three-phase four-wire SAPF mitigates harmonics, compensates for reactive power, neutral current and power factor correction. Conventionally, the positive sequence detection control strategy using phase-locked loop (PLL) is applied as the synchronizing unit vector element to generate reference source currents. Conventional controller tuning process is difficult and fails to perform satisfactorily under supply voltage variation conditions. In this paper, Levenberg-Marquardt back propagation training algorithm based artificial neural network (ANN) controller is proposed to regulate DC link voltage due to its self-adapting and rapid calculation characteristics that allow the controller to handle high nonlinearity and uncertainty in a non-linear system. Weights of a neuron are adapted to minimize total harmonic distortion (THD) of source current under the step, ramp, time series amplitude variation and frequency and amplitude of modulation conditions. The proposed system is modelled in MATLAB/SIMULINK environment and laboratory prototype with dSpace1104 control card is developed. Experimentation results validate the simulated results of the proposed scheme under supply voltage variations for three-phase four-wire distribution system.

Smart Voltage-Source Inverters With a Novel Approach to Enhance Neutral-Current Compensation

The presence of a neutral current is quite common in three-phase (3P) four-wire (4W) distribution systems due to an unequal distribution of linear and nonlinear single-phase (1P) loads and small distributed generators. However, a high neutral current can overload the neutral conductor and distribution transformer, which can cause electrical safety concerns and even fire. Among several existing neutral current compensators, the 3P four-leg (4L) voltage-source inverter (VSI) provides better control flexibility and more efficient performance than the passive compensators but requires a higher VSI capacity for the fourth-leg operation. To provide a solution to the aforementioned problem, this paper presents a novel control method to utilize the available capacity of a 3P-4L VSI after active and reactive power regulation to enhance the neutral-current compensation. A smart VSI (SVSI) is designed to operate with a solar photovoltaic unit, regulate the ac side voltage, and minimize the neutral current. Case studies are conducted with actual load data from a commercial building in the PSCAD/EMTDC software environment. The designed system with the proposed control method can provide a significant improvement in the neutral-current compensation, phase balancing, and unbalance factor compared to a fixed-capacity 3P-4L SVSI. Experimental results using a TMS320F28335 digital signal processor microcontroller and modified Semiteach 3P-4L inverter are presented to verify the robustness of the designed controller and the enhancement to the neutral-current compensation using the proposed dynamic capacity-control method.

Three‐phase four switch DSTATCOM topologies with special transformers for neutral current compensation and power quality improvement

Three-phase four switch (TPFS) inverters are an effective solution to reduce the size and cost of the distribution STATic COMpensator (DSTATCOM). The performance of TPFS inverter is identical to three-phase four leg, three-phase split capacitor inverter topologies during balanced load conditions. During unbalanced load conditions, the absence of the neutral wire in TPFS topologies does not allow the DSTATCOM to compensate the unbalance in load currents. To overcome this limitation, a special purpose transformer is connected across the load along with the DSTATCOM. This special transformer provides a path for neutral current, reduces the cost and rating of the inverter, improve the performance under stringent unbalanced currents generated by computer loads and also improves short duration overloading capability. In the proposed work, two different TPFS topologies namely four switch one capacitor and four switch split capacitor are proposed along with two special purpose transformers which include zigzag and T-connected for three-phase four-wire distribution systems. The combination of TPFS inverter and special transformer can achieve power factor improvement, harmonic elimination, neutral current compensation and load balancing. The evaluation of the proposed method has done using simulation and experimental investigations.

Chebyshev Functional Expansion Based Artificial Neural Network Controller for Shunt Compensation

Three-phase four-wire (TPFW) distribution systems are prone to various power quality (PQ) issues, such as voltage fluctuations, poor power factor, unbalanced load conditions, and the presence of harmonics in current. Mitigation of these PQ problems using appropriate shunt compensator requires advanced control algorithms for control of three-phase voltage source converters (VSC) in a distribution system. In this paper, Chebyshev functional expansion based artificial neural network ( ChANN ) algorithm for shunt compensation using distribution static compensator (DSTATCOM) is proposed. The parameters of ChANN are trained in real time. Implementation results with linear and nonlinear loads are demonstrated on a prototype hardware designed and developed using dSPACE 1104, current and voltage sensors for the realization of DSTATCOM for TPFW system. A zigzag transformer is used along with conventional three-phase, three-wire (TPTW) DSTATCOM to reduce its overall rating. Suitable comparisons with conventional control techniques are also mentioned.

Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single-Wire Earth Return Electric Power Distribution Grids

This paper deals with the deployment of a local three-phase four-wire (3P4W) electrical power distribution system (EPDS), using a single- to three-phase unified power quality conditioner (UPQC) topology, called UPQC-1Ph-to-3Ph. The topology is indicated for applications in rural or remote areas in which, for economic reasons, only EPDS with single-wire earth return are accessible to the consumer. Since the use of three-phase loads is increasing in these areas, access to a three-phase distribution system becomes preponderant. By adopting a dual compensation strategy, the proposed UPQC-1Ph-to-3Ph is able of draining from the single-phase electrical grid a sinusoidal current and in phase with the voltage, resulting high-power factor. Furthermore, the system is also able to suppress grid voltage harmonics, as well as to compensate for other disturbances, such as voltage sags. Thus, a 3P4W system with regulated, balanced, and sinusoidal voltages with low-harmonic contents is provided for single- and three-phase loads. An analysis of the power flow through the series and parallel converters is performed in order to aid the designing of the power converters. Experimental results are presented for validating the proposal, as well as evaluating the static and dynamic performances of the proposed topology.

Novel adaptive reclosing scheme using wavelet transform in distribution system with battery energy storage system

Most distribution systems are operated in an unbalanced state; hence, neutral currents can be generated by unbalanced currents in three-phase four-wire distribution systems. This paper proposes a novel adaptive reclosing scheme that uses the neutral current in a distribution system with a battery energy storage system (BESS). The BESS, which operates as an uninterruptible power supply, is connected to the load side. In the proposed scheme, there are two circuit breakers (CBs) at the source and load sides. The wavelet transform of neutral current is performed using symlets 5 mother wavelet at level 2. The summation of the absolute values of level 2 detail coefficients is calculated, and the absolute value of the differentiation of this summation is proposed as a new index for detecting fault clearance. The CB at the source side is reclosed after detecting fault clearance using ADSum. Then, the CB at the load side is reclosed after the completion of a synchronism check. To verify the proposed scheme, the BESS is modeled using the ATP-ElectroMagnetic Transients Program. In addition, various simulations are conducted according to fault types and fault clearance times. Simulation results show that successful adaptive reclosing is possible in the distribution system with the BESS.

FLC-Based SOGI Controller for Photovoltaic-Operated STATCOM for Current Harmonic Elimination

In this paper, a photovoltaic (PV)-array-interfaced static synchronous compensator (STATCOM) with a fuzzy-logic-controller (FLC)-based second-order generalized integrator (SOGI) is presented to compensate for the current harmonics in the three-phase four-wire distribution system. The compensation ability and the effectiveness of the compensation depend on the capability of the dc link and the control techniques employed. The control techniques used in the system decides the required quantity of the measurement devices and the cost of the control unit. The proposed SOGI controller uses only the currents measured at the converter and load terminals. It does not require any voltage sensor. The proposed topology of STATCOM uses the energy generated in the PV array and FLC-based SOGI to offer the sufficient energy and provide the sustainable compensation against the current disturbances. The simulation results and experimental results of the prototype model are presented to validate the performance of the proposed STATCOM in compensating the current harmonics.

Improved Neutral Current Compensation With a Four-Leg PV Smart VSI in a LV Residential Network

Loads in low voltage (LV) residential areas are mainly single-phase types which are supplied from a delta/wye connected distribution transformer with a grounded neutral conductor creating a three-phase (3P) four-wire (4W) distribution system. The unbalanced single-phase load distributions in traditional 3P-4W LV networks cause significant neutral currents which can result in the overloading of the neutral conductor and electrical safety concerns for customers. In this paper, the dependency of the load generated neutral current on the distribution line variable zero sequence R/X ratios is developed, and a new decentralized robust active neutral compensation method is proposed using a multifunctional transformerless 3P four-leg (4L) photovoltaic (PV) smart voltage source inverter (SVSI). System stability is verified from the bode analysis and the improved neutral compensation is evaluated from the circuitry model analysis. Actual single-phase customer loads with real sun irradiance and temperature profiles are used with an urban 3P-4W LV network model from Australia and implemented in simulation using the PSCAD/EMTDC software to verify the efficacy of the proposed controller in real world distribution networks. Different transient faults analyses and point of common coupling dynamic voltage regulation are also performed and faster fault recovery, better neutral compensation, and optimized voltage profile are achieved from the designed PV-SVSI.

3상 4선식 저압 배전선로에서 선형 및 비선형 부하의 사용시 전압 불평형률 비교 분석

In the three-phase four-wire low-voltage power distribution equipment, single-phase and three-phase load have been used mainly mixed. Also linear and nonlinear loads have been used together in the same conditions. In a three-phase four-wire distribution line, the current distribution of three-phase linear load is almost constant in each phase during driving or stopping, but the single-phase load is different from each other for each phase in accordance with the operation and stop. So that the voltage unbalance is caused by the current difference of each phase. In the three-phase four-wire distribution system, non-linear load is used with linear load. The presence of single-phase nonlinear loads can produce an increase in harmonic currents in three-phase and neutral line. It can also cause voltage unbalance. In the present study, we analyzed for the voltage unbalance fluctuations by the operation pattern of the single and three-phase linear and non-linear load in three-phase four-wire low voltage distribution system.

Power Quality Improvement in Three-phase Four-wire Distribution System using STATCOM with Reduced Switches

Power Quality Improvement in Three-phase Four-wire Distribution System using STATCOM with Reduced Switches

Power quality issues in small rating wind generation in weak distribution system

In this paper, a wind generator system (WG) comprising of squirrel cage induction generators (SCIGs) is described and its impact on three-phase four-wire weak distribution system is analysed with different short circuit ratio. This integrated system has various power quality issues such as voltage variation, harmonics, and unbalancing, etc. These issues are thoroughly examined and addressed in this paper with use of a distribution static compensator (DSTATCOM). The voltage source converter (VSC) of DSTATCOM is controlled to provide needed compensation to the foresaid system. DSTATCOM injects compensating current to the distribution system for reactive power and transient voltage support for zero voltage regulation (ZVR). A complete power balance analysis of the proposed system is also presented under different operating conditions of the distribution system through simulation in MATLAB 2011b.