Balanced Source Currents Research Articles

Reactive Power Control and Neutral Current Elimination of Four Wire Five Level NPC Inverter based STATCOM using 3D-SVPWM Technique

In this paper, three phase four wire five level Neutral Point Clamped Inverter (NPCI) based Static synchronous Compensator (STATCOM) is implemented for reactive power control and neutral current elimination. Three dimensional Space Vector Pulse Width Modulation (3D-SVPWM) control strategy is developed to control this 5-level NPC inverter. The behaviour of static synchronous compensator is analyzed and reactive power control is done using constant DC voltage. The objective of this compensating method is to provide balanced and sinusoidal source currents under unbalanced and nonlinear load conditions and reactive power control. The 3D-SVPWM technique provides reduced harmonic content in output voltage and current, controlled source current, minimized common mode voltage and improved output voltage. In 3D-SVPWM, switching pulses are generated with non-redundant switching states, which lead to reduce the complexity in switching time calculation and computational time is less. The highlights of the paper includes the neutral current is reduced to 0.25A, source current harmonics is minimized and it provides balanced and sinusoidal source currents with help of STATCOM compensation. The simulation and experimental results demonstrates the sinusoidal and harmonics free source current and minimized neutral current for four wire five level NPCI based STATCOM.

Constant DC-Capacitor Voltage-Control-Based Harmonics Compensation Strategy of Smart Charger for Electric Vehicles in Single-Phase Three-Wire Distribution Feeders

This paper discusses harmonic current compensation of the constant DC-capacitor voltage-control (CDCVC)-based strategy of smart chargers for electric vehicles (EVs) in single-phase three-wire distribution feeders (SPTWDFs) under nonlinear load conditions. The basic principle of the CDCVC-based harmonics compensation strategy under nonlinear load conditions is discussed in detail. The instantaneous power flowing into the three-leg pulse-width modulated (PWM) rectifier, which performs as a smart charger, shows that the CDCVC-based strategy achieves balanced and sinusoidal source currents with a unity power factor. The CDCVC-based harmonics compensation strategy does not require any calculation blocks of fundamental reactive, unbalanced active, and harmonic currents. Thus, the authors propose a simplified algorithm to compensate for reactive, unbalanced active, and harmonic currents. A digital computer simulation is implemented to confirm the validity and high practicability of the CDCVC-based harmonics compensation strategy using PSIM software. Simulation results demonstrate that balanced and sinusoidal source currents with a unity power factor in SPTWDFs are obtained on the secondary side of the pole-mounted distribution transformer (PMDT) during both the battery-charging and discharging operations in EVs, compensating for the reactive, unbalanced active, and harmonic currents.

Novel Reactive Power Control Strategy Based on Constant DC-Capacitor Voltage Control for Reducing the Capacity of Smart Charger for Electric Vehicles on Single-Phase Three-Wire Distribution Feeders

This paper proposes a novel reactive power control strategy to reduce the capacity of the previously proposed smart charger for electric vehicles (EVs) on single-phase three-wire distribution feeders. The proposed reactive power control strategy is based on the constant dc-capacitor voltage control of the grid-connected pulsewidth-modulated rectifier. Any calculation blocks of the load-side active current are not needed. Thus, we offer the simplest reactive power control strategy. The basic principle of the proposed reactive power control strategy is discussed in detail, and then confirmed by a digital computer simulation using the PSIM software. A prototype experimental model is constructed and tested. Experimental result demonstrates that balanced source currents with a power factor of 0.9, which is an acceptable value in Japanese home appliances, are obtained on the secondary side of the pole-mounted distribution transformer during the battery charging operation in the EVs, reducing the capacity of the smart charger by 36% as compared with that of the smart charger with the previously proposed control strategy.

Performance of synchronous reluctance generator for DG set based standalone supply system

This paper presents the performance of a SyRG (Synchronous Reluctance Generator) for DG (Diesel Engine Driven Generator) set based standalone generating system. A STATCOM (Static Compensator) is used for its voltage control, harmonics reduction and load balancing on a SyRG based DG set. The proposed system consists of a diesel engine driven specially designed SyRG with a rating of 3-phase, 3.7kW, 50Hz, 4-pole, 230V line voltage SyRG, an excitation capacitor bank of 6.25kVAr and a STATCOM of 5kVA. The modified PBT (Power Balance Theory) based control algorithm is used to estimate the reference source currents for control of STATCOM. A DSP (dSPACE) is used to implement this control algorithm of STATCOM. The performance of the proposed system is studied using STATCOM which improves the performance by exchanging the reactive power with the system. The source of reactive power is a capacitor bank and VSC (Voltage Source Converter) with a DC link capacitor used as STATCOM. The gating signals of VSC of the STATCOM are generated using PBT based control algorithm. The energy stored in the DC link is exchanged with the system to eliminate harmonics, voltage regulation and load balancing. The performance of the SyRG based standalone DG system is observed under a linear load of 3.19kW with power factor of 0.8 and a nonlinear load of 2.99kW under both balanced and unbalanced conditions. The proposed system has maintained fixed terminal voltage at 220V, voltage and current harmonics within 5% under highly nonlinear load and balanced source currents under highly unbalanced load currents.

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.

Reactive Power Control Strategy Based on DC Capacitor Voltage Control for Active Load Balancer in Three-Phase Four-Wire Distribution Systems

This paper proposes a reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy is based on constant DC capacitor voltage control, which is always used in active power line conditioners. Therefore, the proposed reactive power control strategy does not require active, reactive calculation blocks of load currents for the reference source current calculation. Balanced source currents with a predefined power factor can be achieved without unbalanced active and reactive components detection of the load currents. The basic principle of the reactive power control strategy for the ALB is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested to validate the feasibility of the proposed control algorithm. Simulation and experimental results demonstrate that balanced source currents with a predefined power factor are achieved in three-phase four-wire distribution systems.

Reduced-Capacity Smart Charger for Electric Vehicles on Single-Phase Three-Wire Distribution Feeders With Reactive Power Control

In this paper, we propose a new control algorithm to reduce the capacity of a previously proposed smart charger for electric vehicles (EVs) on single-phase three-wire distribution feeders with reactive power control. The basic principle of the proposed control algorithm is discussed in detail. It is shown that controlling the reactive power on the source side reduces the capacity of the previously proposed smart charger. A digital computer simulation is implemented to confirm the validity of the proposed control algorithm using PSIM software. A prototype experimental model is also constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of 0.9, which is acceptable for Japanese home appliances, are obtained on the secondary side of the pole-mounted distribution transformer during both the battery charging and discharging operations in EVs. The capacity of dc capacitor $C_{\rm DC}$ is also reduced by 37% with the proposed reactive power control algorithm.

Application of shunt active power filter for harmonic reduction and reactive power compensation in three‐phase four‐wire systems

This study deals with the analysis and implementation of compensation algorithms applied to a shunt active power filter, which uses three single-phase full-bridge converters sharing the same dc-bus voltage. The shunt filter is applied to three-phase four-wire systems, performing harmonic current suppression, reactive power compensation and power factor improvement. In addition, load unbalances compensation is also carried out. Two different control strategies are presented. In the first strategy, which is called independent current control, the currents of the three-phase power source are independently compensated performing harmonic suppression and load reactive power compensation, that is, the three-phase four-wire system is treated as three independent single-phase systems. In the second strategy, in addition to harmonic suppression and load reactive power compensation, the shunt filter also performs load unbalance compensation, resulting in sinusoidal and balanced source currents. The compensating algorithms are evaluated by means of several experimental test conditions, in order to validate the theoretical development and analyse the performance of the shunt filter.

Smart Charger for Electric Vehicles With Power-Quality Compensator on Single-Phase Three-Wire Distribution Feeders

In this paper, we propose a smart charger for electric vehicles with a power-quality compensator. The proposed smart charger consists of four-leg insulated-gate bipolar transistors (IGBTs). Three legs are used for a single-phase full-bridge-based pulsewidth-modulated (PWM) rectifier, which converts power from ac to dc during the battery-charging operation or from dc to ac during the battery-discharging operation. This PWM rectifier can compensate reactive and unbalanced active currents on single-phase three-wire distribution systems because the third leg is connected to the neutral line of single-phase three-wire distribution feeders. The fourth leg is used as a bidirectional dc-dc converter for battery-charging and battery-discharging operations. The three-leg PWM rectifier uses only constant dc-capacitor voltage control, which is commonly used in active power line conditioners. Thus, the authors have developed the simplest possible control method for a single-phase power-quality compensator. The basic principle of the proposed smart charger is discussed in detail and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents are obtained on the secondary side of the pole-mounted distribution transformer for battery-charging and battery-discharging operations.

A new current control strategy based on the internal model principle for a current balancer in single‐phase three‐wire distribution systems

AbstractThis paper proposes a new current control strategy that is based on the internal model principle for a current balancer in single‐phase three‐wire distribution systems. The proposed current control strategy includes a sinusoidal reference input model to achieve the zero steady‐state error tracking. The appropriate control gains of this control strategy can be systematically determined by using a state‐feedback controller design method via linear matrix inequalities. The basic principle of the proposed control strategy is discussed in detail, and then confirmed by digital computer simulation using the PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that zero steady‐state error tracking is achieved by the proposed control strategy. Also, balanced source currents are obtained on the secondary side of a pole‐mounted distribution transformer while the load conditions are unbalanced. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Topology for current balancer with half‐bridge inverters in single‐phase three‐wire distribution systems with DC‐capacitor‐voltage balancer

AbstractThis paper proposes a new topology for a current balancer with half‐bridge inverters in single‐phase three‐wire distribution systems. Two half‐bridge inverters are connected to the sources. The midpoint of the two capacitors on the DC‐side is connected to a neutral line. The two half‐bridge inverters function as a current balancer for single‐phase three‐wire distribution systems by exchanging the active and reactive power on each feeder through the two DC capacitors. The third leg functions as a DC‐capacitor‐voltage balancer for two DC capacitors connected to the half‐bridge inverters. Thus, balanced source voltages and currents are obtained on the secondary side on the pole‐ mounted distribution transformer with balanced DC‐capacitor voltages. The basic principle of the proposed current balancer is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results show that balanced source voltages and currents are obtained on the secondary side on the pole‐mounted distribution transformer with balanced DC‐capacitor voltages. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(4): 38–46, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22277

A constant DC voltage control‐based strategy for an active power quality compensator in electrified railways with improved response

AbstractThis paper proposes a constant DC voltage control‐based strategy for an active power quality compensator (APQC) used in electrified railways. The proposed strategy consists of only an I‐PD‐based constant DC capacitor voltage control with an added moving‐average type low‐pass filter (LPF). The added LPF improves the response of the constant DC capacitor voltage control for the APQC. Thus we offer the simplest control method for the APQC used in electrified railways with improved response. The basic principle of the proposed control strategy is discussed in detail, and then confirmed by digital computer simulation using the PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with unity power factor are obtained on the primary side of the Scott transformer in the traction substation systems, improving the response by one‐fourth as compared to that of the previously proposed control method. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A Constant DC-Capacitor Voltage Control Based Strategy for Current Balancer in Single-Phase Three-Wire Distribution Systems

This paper proposes a constant dc-capacitor voltage control based strategy for a current balancer in single-phase three-wire distribution systems. The proposed control strategy only uses the constant dc-capacitor voltage control block commonly used in active power conditioners to calculate the compensation current. No calculation blocks to obtain the reactive and unbalanced-active components are necessary. Thus, we provide the simplest possible control strategy for the current balancer. The basic principle of the proposed control method is discussed in detail then its validity is confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of unity are obtained on the secondary side of a pole-mounted distribution transformer while retaining unbalanced load current conditions with a lagging power factor.

直流電圧平衡化回路を有するハーフブリッジインバータを用いた単相三線式配電用電流バランサ

This paper proposes a new topology for a current balancer with half-bridge inverters in single-phase three-wire distribution systems. Two half-bridge inverters are connected to the sources. The midpoint of the two capacitors on the DC-side is connected to a neutral line. The two half-bridge inverters function as a current balancer for single-phase three-wire distribution systems by exchanging the active and reactive power on each feeder through the two DC capacitors. The third leg functions as a DC-capacitor-voltage balancer for two DC capacitors connected to the half-bridge inverters. Thus, balanced source voltages and currents are obtained on the secondary side on the pole- mounted distribution transformer with balanced DC-capacitor voltages. The basic principle of the proposed current balancer is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results show that balanced source voltages and currents are obtained on the secondary side on the pole-mounted distribution transformer with balanced DC-capacitor voltages. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(4): 38–46, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22277

A Constant DC Voltage Control Based Strategy for the Current Balancer in Single-Phase Three-Wire Secondary Distribution Systems

This paper deals with applying the constant dc voltage control based algorithm to the current balancer in single-phase three-wire secondary distribution systems. The power flows into a three-leg inverter, which performs the current balancer, are discussed, and then we show that only the reactive power flows into the three-leg inverter. This demonstrates that the required-capacity of the dc capacitor can be reduced as compared to that of the active power quality compensator used in the electrified railways. This reduced-capacity dc capacitor results in the rapid and stable balancing. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. Digital computer simulation results demonstrate that the balanced source currents with unity power factor are obtained remaining the unbalanced load currents conditions.

A new current balancer in single‐phase three‐wire secondary distribution feeders using the correlation coefficients

AbstractThis paper proposes a new current balancer in single‐phase three‐wire secondary distribution systems using the correlation coefficients. The components of the load currents correlative to the primary side voltage waveform, which correspond to the active currents, are detected in each feeder, then the nonactive and unbalanced‐active components are compensated on the source side. The balanced currents with unity power factor are obtained in each feeder. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. A prototype experimental system is constructed and tested. Experimental results demonstrate that the balanced source currents with unity power factor are obtained in spite of unbalanced load currents. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(1): 50–58, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20843

A constant DC voltage control based compensation method of an active power quality compensator for electrified railways

AbstractThis paper proposes a novel and simple control method for the active power quality compensators (APQCs) used in electrified railways. The proposed method uses only the constant dc capacitor voltage control block, which is commonly used in the APQCs. No detection blocks of the harmonic, reactive, and negative‐sequence components are necessary. Thus we offer the simplest way to compensate the harmonic, reactive, and negative‐sequence currents on the primary side of the Scott transformer in the traction substation. The basic principle of the proposed control method is discussed in detail, and then confirmed by digital computer simulation usingPSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that the balanced source currents with the unity power factor are obtained on the primary side with the proposed control method, which uses only the constant dc capacitor voltage control. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

New Control Method of Active Power Quality Compensator with Reduced-Capacity Three-Leg Inverter for Electrified Railways

This paper proposes a new control method for reducing the capacity of an active power quality compensator with a three-leg inverter used in electrified railways. In the proposed control method, the fundamental reactive and unbalanced-active components of the load currents are detected. The non-active and unbalanced-active components are compensated on the source side with the fundamental reactive power control. This reactive power control reduces the capacity of the three-leg inverter, which performs the active power quality compensator. The basic principle of the proposed control method is discussed in detail, and then confirmed by digital computer simulation using the PSIM software. A reduced-scale experimental model is constructed and tested. Experimental results demonstrate that the balanced sinusoidal source currents with the power factor of 0.9 are obtained, reducing the capacity of the three-leg inverter by 13% as compared to the already proposed control method.

A New Control Method of Current Balancer for Single-Phase Three-Wire Secondary Distribution Systems Using the Correlation and Cross-Correlation Coefficients

This paper proposes a new control method of the current balancer for single-phase three-wire secondary distribution systems using the correlation and cross-correlation coefficients. The components of the load currents correlative and cross-correlative to the primary side voltage waveform, which correspond to the active and reactive currents, are detected in each feeder, then the reactive and unbalanced-active components are compensated on the source side. The balanced currents with the variable power factor are obtained in each feeder. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. A proto-type experimental system is constructed and tested. Experimental results demonstrate that the balanced source currents with the power factor of 0.9 are obtained in spite of unbalanced load currents.

電源電圧と負荷電流の相関に着目した単相三線式配電用電流バランサの制御法

This paper proposes a new current balancer in single-phase three-wire secondary distribution systems using the correlation coefficients. The components of the load currents correlative to the primary side voltage waveform, which correspond to the active currents, are detected in each feeder, then the nonactive and unbalanced-active components are compensated on the source side. The balanced currents with unity power factor are obtained in each feeder. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. A prototype experimental system is constructed and tested. Experimental results demonstrate that the balanced source currents with unity power factor are obtained in spite of unbalanced load currents. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(1): 50–58, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20843