Topology Of Distribution Static Compensator Research Articles

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.

Predictive current control of distribution static compensator for load compensation in distribution system

Predictive control is an emerging alternative in the control of power converters because of its potential for achieving fast transient response and increased control accuracy. Research on this topic has increased in recent years owing to the availability of high speed digital controllers that can be used for the control of power electronic systems. This study proposes a predictive current control scheme for an improved topology of distribution static compensator (DSTATCOM) intended for load compensation. The proposed strategy derives the converter switching pulses using a cost function that defines the desired system behaviour. An improved DSTATCOM topology employing predictive current control algorithm tracks reference current effectively and makes source current sinusoidal and also in-phase with voltage at the point of common coupling in both steady state and transient conditions. In addition, this scheme does not require any modulation technique. The control scheme has been implemented using field programmable gate array. Simulation and experimentation have been carried out to verify and validate the performance of the proposed scheme and the results are reported in this study.

Three‐leg inverter‐based distribution static compensator topology for compensating unbalanced and non‐linear loads

This study proposes a new three-leg voltage source inverter (VSI)-based distribution static compensator (DSTATCOM) topology to compensate unbalanced and non-linear loads in low-voltage three-phase four-wire distribution systems. The proposed topology uses a three-leg VSI with a single DC storage capacitor. This scheme has an additional small AC capacitor which is connected between negative DC bus to the system neutral. As the proposed topology uses a single DC-link capacitor, the DC voltage balancing issues associated with the popular split capacitor neutral clamped VSI topology is avoided. Moreover, the topology is able to compensate neutral current without using four-leg inverter topology. Analysis and modelling of the proposed topology is explained in detail. Simulation studies are carried out to verify the performance of the proposed scheme and results are presented. The performance of the new topology has been compared with conventional three-leg two level split capacitor VSI-based DSTATCOM topology. Results are also experimentally verified on a laboratory prototype of DSTATCOM.

An Improved New Technique to Compensate Reactive and Nonlinear Loads by Hybrid DSTATCOM Topology

This project presents a control algorithm based on enhanced phase locked loop (EPLL) for distribution static compensator (DSTATCOM) to compensate reactive power, to provide load balancing, to eliminate harmonics, to correct power factor, and to regulate point of common coupling (PCC) voltages. Under linear and nonlinear loads An LCL filter has been used at the front end of a voltage source inverter (VSI), which provides better switching harmonics elimination while using much smaller value of an inductor as compared with the traditional L filter. A capacitor is used in series with an LCL filter to reduce the dc-link voltage of the DSTATCOM. This consequently reduces the power rating of the VSI. With reduced dc-link voltage, the voltage across the shunt capacitor of the LCL filter will be also less. It will reduce the power losses in the damping resistor as compared with the traditional LCL filter with passive damping. Therefore, the proposed DSTATCOM topology will have reduced weight, cost, rating, and size with improved efficiency and current compensation capability compared with the traditional topology. A systematic procedure to design the components of the passive filter has been presented. The effectiveness of the proposed DSTATCOM topology over traditional topologies is validated through both simulation and experimental studies. Index Terms—Distribution static compensator (DSTATCOM), hybrid topology, passive filter, power quality (PQ).

An Improved Hybrid DSTATCOM Topology to Compensate Reactive and Nonlinear Loads

This paper proposes an improved hybrid distribution static compensator (DSTATCOM) topology to address some practical issues such as power rating, filter size, compensation performance, and power loss. An LCL filter has been used at the front end of a voltage source inverter (VSI), which provides better switching harmonics elimination while using much smaller value of an inductor as compared with the traditional L filter. A capacitor is used in series with an LCL filter to reduce the dc-link voltage of the DSTATCOM. This consequently reduces the power rating of the VSI. With reduced dc-link voltage, the voltage across the shunt capacitor of the LCL filter will be also less. It will reduce the power losses in the damping resistor as compared with the traditional LCL filter with passive damping. Therefore, the proposed DSTATCOM topology will have reduced weight, cost, rating, and size with improved efficiency and current compensation capability compared with the traditional topology. A systematic procedure to design the components of the passive filter has been presented. The effectiveness of the proposed DSTATCOM topology over traditional topologies is validated through both simulation and experimental studies.

Modified DSTATCOM Topology with Reduced DC Link Voltage for Reactive and Harmonic Power Compensation of Unbalanced Nonlinear Load in Distribution System

Abstract This paper proposes a modified four-leg distribution static compensator (DSTATCOM) topology for compensation of unbalanced and nonlinear loads in three-phase four-wire distribution system. DSTATCOM, connected in parallel to the load, supplies reactive and harmonic powers demanded by unbalanced nonlinear loads. In this proposed topology, the voltage source inverter (VSI) of DSTATCOM is connected to point of common coupling (point of interconnection of source, load, DSTATCOM) through interface inductor and series capacitance, unlike the conventional topology which consists of interface inductor alone. Load compensation with a lower value of input DC link voltage of VSI is possible in this modified topology compared to conventional topology. A comparative study on modified and conventional topologies in terms of voltage rating of inverter power switches, switching losses in VSI and power rating of input DC capacitor of VSI is presented. The detailed design aspects of DC link capacitor and interface series capacitor are also presented. The reference filter currents are generated using instantaneous symmetrical component theory and are tracked using hysteresis current control technique. A detailed simulation study is carried out, to compare the compensation performances of conventional, modified topologies using PSCAD simulator and experimental studies are done to validate the simulation results.

Three-level NPC inverter based new DSTATCOM topologies and their performance evaluation for load compensation

Now-a-days for effective load compensation, a conventional three-level neutral point clamped (CNPC) inverter topology is more preferably used. This compensator, however, faces the problems of additional clamping diodes, which reduces the redundant switching states and improves the problem of capacitor voltage imbalance; further increasing the inverter cost. In this paper, a detailed analysis of conventional NPC voltage source inverter (VSI) based Distribution Static Compensator (DSTATCOM) is given for shunt applications and to overcome its limitations, Conergy NPC and Active NPC VSI based new DSTATCOM topologies are proposed, exclusively for the load compensation. To demonstrate the effectiveness of the aforementioned topologies for shunt compensation, a three phase four wire system has been taken into consideration. Instantaneous symmetrical component theory (ISCT) is used for reference current generation, while, the hysteresis current control pulse width modulation (PWM) is used to generate the switching sequence for all the NPC configurations. A detailed simulation study has been carried out in MATLAB environment and the comparative evaluation of all the above DSTATCOM topologies is being provided.

Modeling and Simulation of Different System Topologies for DSTATCOM

Power Quality enhancement in a distribution network is achieved by shunt compensation device known as Distribution static compensator (DSTATCOM).In this paper, three different system topologies for Distribution Static Compensators (DSTATCOMs) are modeled and tested using Simulink'SimPowerSystem Toolbox for power system quality studies. Simulation tests on a distribution system, equipped with the unbalanced and non-linear load. With the different system topologies of Distribution Static Compensators (DSTATCOMs) it is observed that power factor can be improved in supply system. The DSTATCOM controls are based on Synchronous Reference Frame control. The modeled DSTATCOM topologies can be used to develop and test different, control strategies and methods for the DSTATCOM. These models can also aid instructors in teaching power quality courses.

A DSTATCOM Topology With Reduced DC-Link Voltage Rating for Load Compensation With Nonstiff Source

The distribution static compensator (DSTATCOM) is used for load compensation in power distribution network. In this paper, a new topology for DSTATCOM applications with nonstiff source is proposed. The proposed topology enables DSTATCOM to have a reduced dc-link voltage without compromising the compensation capability. It uses a series capacitor along with the interfacing inductor and a shunt filter capacitor. With the reduction in dc-link voltage, the average switching frequency of the insulated gate bipolar transistor switches of the DSTATCOM is also reduced. Consequently, the switching losses in the inverter are reduced. Detailed design aspects of the series and shunt capacitors are discussed in this paper. A simulation study of the proposed topology has been carried out using power systems computer-aided design simulator and the results are presented. Experimental studies are carried out to verify the proposed topology.

DSTATCOM topologies for three-phase high power applications

This paper proposes distribution static compensator topologies for application in three-phase high power distribution systems. These topologies overcome both the voltage and current rating constraints imposed by the semiconductor switches by the use of three single-phase multi-secondary transformers. Five topologies, namely, four leg-group, three leg-group split-capacitor, H bridge-group, three leg-group and two leg-group are suggested. These can effectively compensate unbalance, harmonics and low power factor of the load currents. Apart from the use of minimum number of current sensors and a single capacitor, the control circuit is very simple. It provides the electrical isolation and security deemed essential for high voltage systems. A detailed comparison is made for these topologies. Based on the hardware requirement and compensation quality, the four leg-group and three leg-group topologies are shown to be superior than the other structures for application in three phase four-wire and three-wire systems respectively. They are validated through extensive simulation studies using PSCAD in a three-phase four-wire power network with non-linear unbalanced load. Experimental verification is conducted for H bridge-group topology on a single phase system using a DSP-based prototype laboratory model.

Star/Hexagon Transformer Based Three-Phase Four-Wire DSTATCOM for Power Quality Improvement

A new topology of DSTATCOM (distribution static compensator) is proposed for power quality improvement in three-phase four-wire distribution systems. A three-leg VSC (Voltage Source Converter) is integrated with a star/hexagon transformer for the compensation of reactive power for voltage regulation or for power factor correction along with load balancing, elimination of harmonics currents and neutral current compensation. The star/hexagon connected transformer provides a path to the zero sequence current in a three-phase four-wire distribution system. In order to optimize the voltage rating of the VSC, the star/hexagon transformer is designed to have a suitable voltage rating for the secondary windings for integrating the three-leg VSC. This transformer connection provides the selection of 'off the shelf' VSC for this application and it also provides isolation for the VSC system. The performance of the proposed DSTATCOM system is validated through simulations using MATLAB software with its Simulink and Power System Block set (PSB) toolboxes.

State Feedback Control of Multilevel Inverters for DSTATCOM Applications

In this paper, load compensation using multilevel inverter-based distribution static compensator (DSTATCOM) is presented. The DSTATCOM is connected to a three-phase four-wire (3p4w) distribution system. Two different multilevel inverter topologies are used to realize the DSTATCOM. They are diode-clamped multilevel inverter (DCMLI) and flying capacitor multilevel inverter (FCMLI). A compensating technique has been derived, which uses the state feedback control to the multilevel inverters-based DSTATCOMs. A switching strategy for the multilevel inverters that ensures utilization of all output voltage states of the inverter for efficient tracking of references has been proposed. The schemes of dc-link capacitor voltage control for DCMLI and flying capacitor voltage control for FCMLI have been discussed. Comparative studies of performances of the two DSTATCOM topologies are performed. The simulation studies are performed using PSCAD/EMTDC to validate the efficacy of the proposed control scheme.

Inverter topologies for DSTATCOM applications—a simulation study

This paper describes a few different topologies of inverters used for realizing a distribution static compensator (DSTATCOM). A brief introduction of the need for shunt compensation as well as the requirements of the shunt compensator has also been given. An algorithm for generating references has been described. Three major topologies of inverters – three-leg inverter with single dc capacitor, three-leg inverter with neutral clamped dc capacitors, four-leg inverter and three single-phase inverters with common dc capacitor – have been described and simulated. DSTATCOM topologies for high voltage distribution systems have also been described. The Voltage Source Converter (VSC) topologies have been compared on the basis of the performance of the inverter for certain chosen system conditions and the number of switch devices and dc capacitors used. All simulations have been performed using PSCAD/EMTDC.

A flexible DSTATCOM operating in voltage or current control mode

The topology and control are discussed of a distribution static compensator (DSTATCOM) that can be operated flexibly in the voltage or current control mode. In the voltage control mode, the DSTATCOM can force the voltage of a distribution bus to be balanced sinusoids. In the current control mode, it can cancel distortion caused by the load, such that current drawn by the compensated load is pure balanced sinusoid. Both these objectives are achieved, irrespective of unbalance and harmonic distortions in load currents or source voltages. The chosen DSTATCOM topology includes three single-phase voltage source inverters connected in parallel to a filter-capacitor, which allows the high-frequency component of the current to pass. A switching control scheme is proposed, and its suitability is proved for this problem. The proposed scheme is verified using computer simulation studies.