Current Source Converter Topology Research Articles

Three-Phase Flying Capacitor Clamped Current Source Converter With Active Capacitor Voltage and CMV Control

AC-type flying capacitor (FC) concept has been proposed for current source converter (CSC) topologies recently, which offers unique merits over the traditional CSCs, such as lower <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> with improved dc-link voltage quality as well as flexible common-mode voltage (CMV) control. To cope with the main-stream three-phase industrial applications, in this article, the three-phase flying-capacitor-clamped CSC is introduced and extensively investigated for the first time. A novel space vector modulation is proposed, featuring a modular design process, active FC voltage control, and CMV suppression. The detailed commutation principles and the capacitor clamping voltage influence under different switching states are comprehensively addressed. Then, the redundant switching states are optimized to fulfill the multiple targets simultaneously. Simulation and experimental results are performed to demonstrate the superior dc-link power quality and CMV performance compared with the traditional three-phase CSC topology.

Power‐take‐off topology comparison for a wave energy converter

Wave Energy Converters (WECs) generally use a Mechanical Power-Take-Off (MPTO) involving hydraulics or gearing to optimise the extraction of energy from the incoming waves before converting it into electrical energy via a high speed rotating generator. This simplifies the design of the Electrical Power Conversion System (EPCS). Further, it facilitates the use of mechanical energy storage such as hydraulic accumulators to reduce the peaky nature of the power flow and allows the WEC resonant frequency to be tuned for maximum energy capture. This work compares two power electronic converter topologies for an Electrical PTO (EPTO). This EPTO is intended to replace the aforementioned MPTO and generator with a Permanent Magnet Linear Machine (PMLM) directly coupled to the WEC. The compared topologies comprise either a Current Source Converter (CSC) or a Voltage Source Converter (VSC) as the generator interface working in combination with a DC-DC converter and an Energy Storage System (ESS). The principle differences between the two topologies are explored and losses are evaluated in a modular EPCS working with a WEC. Wide-bandgap power electronic switches are assumed for both topologies over a range of switching frequencies. The evaluation concludes that the CSC topology is advantageous at higher switching frequencies.

Implementation of a new high‐power current‐source single‐stage PV grid‐connected system with reactive power compensation

In view of the shortcoming of voltage source converter in the application of high-power photovoltaic (PV) grid-connected system, this study designs a new single-stage current source PV grid-connected system based on dc current reinjection conversion. The system can freely control the dc current in a wide range, so only one stage of conversion is needed to achieve wide range control of the dc side maximum power point tracking. The amplitude and phase angle of the ac output current can be freely regulated, so it is able to realise grid-connected power generation under unit power factor and supply a certain amount of reactive power according to the control order while grid-connected power generation. Meanwhile, the new current source converter topology eliminates the ac capacitors which are arranged between the converter and the power grid, and gets approximately sinusoidal ac currents without setting filters. This study describes the circuit structure and control of the PV grid-connected system, and builds an experimental prototype. The simulation and experimental results will be shown to demonstrate the feasibility of the converter topology, and the effectiveness of the control strategy.

Switched-Boost Action Based Multiport Converter

Multioutput converters with single input source are currently studied as an alternative to conventional dc–dc topologies in order to improve power density in low-power multiload applications. This paper reviews three different ways in which a boost topology can be customized to supply multiple outputs. The first way uses a charge-sharing approach using individual switches to distribute inductor energy to different capacitors. The second method of creating a multiport converter (MPC) combines two converters with similar front end to generate two outputs using only one controlled switch. Using this method, a boost converter can be combined with single–ended primary–inductor converter (SEPIC), Cuk, and current source converter topologies. The third method uses time multiplexing of switches to produce two regulated ports and is referred to as switched-boost action. This method uses relatively less number of switches and allows regulation and control of all the outputs. Practical utility of switched-boost action based MPC is reported in this paper. This switched-boost MPC is applied to a renewable power converter system to interface a solar panel, a battery, and home loads to produce a 12-V and a 48-V bus. The 12-V bus is interfaced to battery and capable of optimally charging the battery in constant current–constant voltage (CC-CV) mode. The converter is demonstrated to operate with solar panel as it supplies a 12-V battery and a 48-V load bus. When the solar power is not available, the converter automatically goes into a mode in which the 12-V battery supplies the loads on the 48-V bus.

Control of Three-Phase Bidirectional Current-Source Converter to Inject Balanced Three-Phase Currents Under Unbalanced Grid Voltage Condition

A single-stage, bidirectional, current-source converter (CSC) topology to interface a dc microgrid with an ac grid is reported in the literature. In this topology, under a balanced grid voltage condition, the dc-link inductor current can be regulated over a wide range—from zero to rated value—while the ac-side current has low harmonic distortion. However, unbalanced grid voltages result in second-harmonic pulsation in the current and power on the dc side of the converter. In addition, the ac-side currents will be unbalanced due to the presence of a negative-sequence component. This would result in undesired tripping of the converter if one of the phase currents exceeded its rated value. Various control loop structures for the operation of voltage-source converter under unbalanced grid voltage conditions are reported in the literature. However, use of similar control loop structures for CSC may lead to unstable operation. Therefore, a control scheme to inject balanced three-phase currents into the ac grid under an unbalanced grid voltage condition is proposed in this paper. The stability of the proposed control scheme is studied using a small-signal model of the converter. Performance of the proposed control scheme is studied using MATLAB/Simulink and is experimentally validated.

Integrated fuzzy-PI controlled current source converter based D-STATCOM

AbstractThe distribution static synchronous compensator (D-STATCOM) is a shunt-connected current injection custom power (CP) device that can be used for improving quality and reliability of the power supplied to electric consumers under dynamic conditions of the distribution system. The CP devices such as dynamic voltage restorer and unified power quality conditioner including D-STATCOM are mostly designed and implemented using voltage source converter topology. The performance of D-STATCOM can be improved, if it is realized by using a current source converter topology which can generate a controllable current directly at its output terminals. Although the current source converter (CSC) topology offers many promising advantageous features, not much research publications with CSC-based approach in the field of CP devices has been reported over the last one decade. This paper presents a novel method of realizing a D-STATCOM using CSC topology with an integrated fuzzy-PI controller for not only mitigating vo...

Modular Multilevel Converters for HVDC Applications: Review on Converter Cells and Functionalities

In this paper, the principle of modularity is used to derive the different multilevel voltage and current source converter topologies. The paper is primarily focused on high-power applications and specifically on high-voltage dc systems. The derived converter cells are treated as building blocks and are contributing to the modularity of the system. By combining the different building blocks, i.e., the converter cells, a variety of voltage and current source modular multilevel converter topologies are derived and thoroughly discussed. Furthermore, by applying the modularity principle at the system level, various types of high-power converters are introduced. The modularity of the multilevel converters is studied in depth, and the challenges as well as the opportunities for high-power applications are illustrated.

Current source converter based D-STATCOM for voltage sag mitigation

This paper presents a novel method of realizing one of the custom power controllers, the distribution static synchronous compensator (D-STATCOM) using current source converter (CSC) topology. Almost all the custom power controllers such as dynamic voltage restorer (DVR), unified power quality conditioner (UPQC) including D-STATCOM are generally designed and implemented by using voltage source converters (VSC) and not much research publications with CSC based approach has been reported over the last one decade. Since the D-STATCOM is a current injection device, its performance can be improved when realized by a current-source converter which can generate a controllable current directly at its output terminals and offers many advantageous features. In this paper, an attempt has been made to study the performance of a CSC based D-STATCOM suitable for use in the power distribution system in order to mitigate voltage sag and improve power quality. The proposed model uses a three leg CSC whose switching strategy is based on sinusoidal pulse width modulation (SPWM). The model has been simulated in the Matlab/Simulink environment. The results of the simulation runs under steady state and dynamic load perturbation provide excellent voltage and current waveforms that support the justification of the proposed model.

English

FACTS technologies allow for improved transmission system operation with minimal infrastructure investment, environmental impact and implementation time compared to the construction of new transmission lines. FACTS provide the needed corrections of transmission functions in order to efficiently utilize existing transmission systems and therefore minimize the gap between the stability and the thermal level. Interline Power Flow Controller(IPFC) is a Voltage Source Converter(VSC) based FACTS controller for controlling power in multi-line system located at a substation. The main aim of the IPFC is to verify the power transfer capability between two or more lines and to establish the proposed voltage regulation function. In this paper, a current source converter topology based IPFC is proposed. In this structure, the dc-side current is regulated to a value larger than the peak value of the maximum line current. The injected voltage is controlled according to the desired reactive power compensation and management active power flow for master line. The decoupled state feedback control for the injected voltage with a separated dc current control is applied to the proposed system. The proposed IPFC has been simulated using the Matlab program.

Power quality improvement by unified power quality conditioner based on CSC topology using synchronous reference frame theory.

This paper deals with the performance of unified power quality conditioner (UPQC) based on current source converter (CSC) topology. UPQC is used to mitigate the power quality problems like harmonics and sag. The shunt and series active filter performs the simultaneous elimination of current and voltage problems. The power fed is linked through common DC link and maintains constant real power exchange. The DC link is connected through the reactor. The real power supply is given by the photovoltaic system for the compensation of power quality problems. The reference current and voltage generation for shunt and series converter is based on phase locked loop and synchronous reference frame theory. The proposed UPQC-CSC design has superior performance for mitigating the power quality problems.

DC fault ride‐through capability and STATCOM operation of a HVDC hybrid voltage source converter

High voltage direct current (HVDC) transmission systems are becoming increasingly popular when compared to conventional AC transmission methods. HVDC voltage source converters (VSC) can offer advantages over traditional HVDC current source converter topologies; as such, it is expected that HVDC-VSCs will be further exploited with the growth of HVDC transmission. This study presents the DC fault ride through capability and new static synchronous compensator (STATCOM) modes of operation for the recently published alternate arm converter, intended for the HVDC market. Operation and fault ride through of the converter during a local terminal to terminal short circuit of the DC-link is demonstrated; during the fault STATCOM operation is also demonstrated.

A Hybrid Modular Multilevel Voltage Source Converter for HVDC Power Transmission

HVDC transmission systems are becoming increasingly popular when compared to conventional ac transmission. HVDC voltage source converters (VSCs) can offer advantages over traditional HVDC current source converter topologies, and as such, it is expected that HVDC VSCs will be further exploited with the growth of HVDC transmission. This paper presents a novel modular multilevel converter hybrid VSC intended for the HVDC market. The concept of the converter operation is described based on steady-state ac-dc power balance. Techniques for dynamic voltage control, enabling the active and reactive powers exchanged with the grid to be controlled, are introduced. Simulation results further illustrate the theory of operation of the converter and confirm the viability of the proposed control approaches. Detailed predictions of the semiconductor losses confirm the potential to achieve very high efficiencies with this topology. Experimental results are provided to validate the presented converter operation.

Current source converter based STATCOM: Operating principles, design and field performance

This paper describes the operating principles, design and field performance of two-level, three-leg device commutated current source converter (CSC) topology based Static Synchronous Compensator (STATCOM), which is developed for medium voltage industry applications. In the paper, the relationship between the reactive power and the control variables is obtained, harmonic minimization techniques applicable to CSC are investigated, and then Selective Harmonic Elimination Technique is applied for the elimination of the 5th, 7th, 11th and 13th harmonics in CSC line current. The design principles of the input filter are also set out. Considerations for optimum sizing of STATCOM in common industry applications are described with the design objective of maximum utilization of power semiconductors. Two CSC based STATCOMs, which are rated at ±500kVAr and 0–1500kVAr capacitive are implemented and applied to industry. Field results are also given in the paper in order to validate the operating principles and design criteria.

Design and Performance of a 200-kHz All-SiC JFET Current DC-Link Back-to-Back Converter

Silicon carbide (SiC) switching devices have been widely discussed in power electronics due to their desirable properties and are believed to set new standards in efficiency, switching behavior, and power density for state-of-the-art converter systems. In this paper, the design, construction, and performance of a 3-kVA All-SiC current-source converter (CSC), also known as current dc-link back-to-back converter (CLBBC), is presented. CSC topologies have been successfully used for many years for high-power applications. However, for low-power-range converter systems, they could not compete with voltage-source-converter topologies with capacitors in the dc-link, since the link inductor has always been a physically large and heavy component due to the comparatively low switching frequencies of conventional high-blocking-voltage silicon devices. New SiC switches such as the JFET, which are providing simultaneously high-voltage blocking, low switching losses, and low on-state resistance (three times lower compared with Si MOSFET with similar V- I rating), offer new possibilities and enable the implementation of a high switching frequency CLBBC and, thus, reducing size and weight of the dc-link inductor. The prototype CLBBC has been designed specifically for the latest generation 1200-V 6-A SiC JFETs and a target switching frequency of 200 kHz.

Conformation of Multilevel Current Source Converter Topologies Using the Duality Principle

This paper explores the issue of constructing multilevel current source converter (MCSC) topologies using the duality principle. Three circuit cells for MCSCs are derived from the applications of the duality on the three common leg circuit cells of multilevel voltage source converters (MVSCs). Based on the presented three cells, three families of MCSC topologies, which are also corresponding to three families of MVSCs, are constructed. Analytical results show that these derived MCSCs and their corresponding MVSCs present analogous features such as the ac side currents/voltages and inductor/capacitor currents/voltages, though they are not direct dual structures. Some experimental results are given to verify the presented MCSC structures.

Current-Source Converter and Cycloconverter Topologies for Industrial Medium-Voltage Drives

This paper, along with an earlier published paper as Part 1, provides a comprehensive review of the state of the art of high-power converters (above 1 MW) for adjustable-speed ac drives. In this highly active area, different converter topologies have been developed for various drive applications in the industry. Due to its extensive coverage, the subject is divided into two parts: multilevel voltage source and current source converter topologies. This paper is focused on the second part and covers the current source converter technologies, including pulsewidth-modulated current-source inverters (CSIs) and load-commutated inverters. In addition, this paper also addresses the present status of the direct converter, which is also known as cycloconverter (CCV). This paper focuses on the latest CSI and CCV technologies and an overview of the commonly used modulation schemes. It also provides the latest technological advances and future trends in CSI- and CCV-fed large drives. This paper serves as a useful reference for academic researchers and practicing engineers in the field of power converters and adjustable-speed drives.

Low-cost current-fed PMSM drive system with sinusoidal input currents

Standard low- and medium-power drives are based on the voltage-source converter topology. There has been less research work on dual topology drives, based on a current-fed inverter structure. Although energy storage is more efficient in capacitors than in inductors, due to some inherent advantages of current-source converter topology, and at the first place, the absence of a dc-link electrolytic capacitor, a current-source drive system made with a considerably reduced dc link inductor could be better low-cost solution with improved reliability, lifetime, and transient response than conventional drive. This paper is about a new current-fed drive topology with sinusoidal input currents, which is applied to a permanent-magnet synchronous machine in low-cost applications. A three-switch front-end pulsewidth modulator buck rectifier with an appropriate control technique, a simple thyristor inverter at the output, together with a small dc choke (which can be embedded in the machine), virtually offers an inductorless integrated drive system solution and could challenge standard industry solutions. System description, analysis, design guidelines, simulated results, and measured experimental results will be presented.

Current-Source Converter Based STATCOM: Modeling and Control

STATCOM is a FACTS controller that is used in power systems to regulate the line voltage, enhance the power transmission capacity and extend the transient stability margin. STATCOM is conventionally realized by a voltage-source converter; however, being a current injection device, its performance can be improved when realized by a current-source converter (CSC) that can generate a controllable current directly at its output terminals. In this paper, a STATCOM based on the current-source converter topology is proposed. The nonlinear model of the current-source converter, which is the source of the difficulties in the controller design, has been modified to a linear model through a novel modeling technique. The proposed modeling technique is not based on the linearization of a set of nonlinear equations around an operating point. Instead, the power balance equation and a nonlinear input transformation are used to derive a linear model independent of the operating point. This model acts as the basis for the design of a decoupled state-feedback controller. The proposed STATCOM has been simulated using the PSCAD/EMTDC package. The simulation results show that a CSC-based STATCOM can result in excellent current and voltage waveforms as well as very short response time while operating at a low switching frequency. This makes the proposed scheme suitable for high power applications.

Artificial Intelligent Controller for Current Source Converter-Based Modular Active Power Filters

The control methodology of the active power-line filter is the key element for its successful performance in mitigating the line current harmonics. The control system processes the distorted line current signal and forces the converter to inject the proper compensating current. At the same time, it regulates the dc term, i.e., the dc current in the current source converter topology and the dc voltage in the voltage source converter topology. In this paper, a new intelligent control scheme for a modular single-phase active power filter based on the current source converter (CSC) topology is proposed. The intelligent controller utilizes two adaptive linear neurons (ADALINEs) to process the signals obtained from the power-line. The first ADALINE (the Current ADALINE) extracts the harmonic components of the distorted line current signal and the second ADALINE (the Voltage ADALINE) estimates the fundamental component of the line voltage signal. The outputs of the two ADALINEs are used to construct the modulating signals of a number of CSC modules, each dedicated to eliminate a specific harmonic. The proposed controller is also responsible for activating selected CSC filter module(s) to the electric grid. The automated activation of the corresponding filter module(s) is based on the decision-making rules in accordance with the current total harmonic distortion (THD/sub i/) and the harmonic factor (HF) levels set by the IEEE 519-1992 standard. A special 3-level PWM switching strategy is proposed for the filter modules which results in a 50% reduction in the overall switching losses compared with the 2-level method. The proposed controller adjusts the I/sub dc/ in each CSC module based on the present magnitude of the corresponding harmonic current which results in optimum dc-side current value and minimal converter losses. The high speed, accuracy, efficiency and flexibility offered by the proposed controller, combined with the fast response and low dc energy storage requirement of CSC topology, are the main advantages of the proposed active filter system. The analytical expectations are verified by digital simulation using EMTDC simulation package.

A dual GTO current-source converter topology with sinusoidal inputs for high-power applications

A dual gate-turn-off thyristor current-source converter topology with sinusoidal inputs is proposed for high-power applications. The sinusoidal input current is realized by using pulsewidth modulation techniques to eliminate 11th and 13th harmonics and a transformer to cancel 5th, 7th, 17th, and 19th harmonics. Three switching patterns are proposed with a switching frequency of 360 or 420 Hz. The combination of these switching patterns provides a full-range control over the DC output current. Resonant modes of the proposed system are identified, and the criterion for the line capacitor design is provided. Simulation and experimental results are given to verify the theoretical analysis.