Power Converter Topologies Research Articles

Current-Fed Power Processing-Ride Through Robustness [Expert View

Selecting the best power converter topology for a specific application can be somewhat overwhelming considering the advances made in the past 20 years. Many of these advances were accomplished with better semiconductor switches providing faster switching rates, lower on-state voltages, lower power loss, lower power driver requirements, and so on. Selecting the best power converter topology must balance the application's demands with priorities of cost, size/packaging, efficiency, and robustness. Magna-Power Electronics (Magna -Power), a programmable dc power product manufacturer in Flemington, New Jersey, United States, prioritized robustness in its topology selection. The topology choice was driven by the customers' need for high reliability in demanding industrial environments.

Modular Multilevel Converters

The papers in this special section focus on the latest achievements on MMCs regarding the development of new circuit topologies, modeling, operation, and fault analysis. Modular multilevel converters (MMCs) have emerged as an attractive solution for high-voltage high-power applications, such as high-voltage direct current (HVdc) transmission systems, due to their attractive features such as modularity, reliability, high voltage capability, and small footprint. However, new power converter topologies and recent advances in terms of control have expanded the application of the MMC to power conditioning and machine drives, among others.

Mitigation of DC Current Injection in Transformer-Less Grid-Connected Inverters Using a Voltage Filtering DC Extraction Approach

Transformer-less grid-connected PV inverters are an attractive technology choice due to their high-efficiency performance and relatively small volume. However, in the absence of galvanic isolation, dc current can potentially flow into the grid and adversely affect the grid performance. In addition, as the sinusoidal ac output is significantly larger than the dc injection component, accurate dc current sensing at the inverter output remains a technical challenge. As a result, this paper proposes a two-stage dc voltage detection technique that employs an isolated RC attenuation circuit and a software dc-component filtering algorithm. The principle of the proposed technique can be applied in many switch-mode power converter topologies. The simple and cost-effective combination facilitates dc component extraction within the accuracy of 1 mV; moreover, this can be further used as digital dc feedback for active current control purposes. Experimental results from a laboratory prototype demonstrate the high performance of the proposed dc extraction and suppression approach.

Investigation of Fault-Tolerant Capabilities in an Advanced Three-Level Active T-Type Converter

A novel fault-tolerant three-level power converter topology, named advanced three-level active T-Type (A3L-ATT) converter, is introduced to increase the reliability of multilevel power converters used in safety-critical applications. This new fault-tolerant multilevel power converter is derived from the conventional T-Type converter topology. The topology has significantly improved the fault-tolerant capability under any open circuit or certain short-circuit faults in the semiconductor devices. In addition, under healthy condition, the redundant phase leg can be utilized to share overload current with other main legs, which enhances the overload capability of the converter. The conduction losses in the original outer devices can be reduced by sharing the load current with the redundant leg. Moreover, unlike other existing fault-tolerant power converters in the literature, full output voltages can be always obtained in this proposed A3L-ATT converter during fault-tolerant operation. A 13.5-kW ATT-A3L converter prototype was developed and constructed using silicon carbide MOSFETs. Simulation and experimental results were obtained to substantiate the theoretical claims of this new fault-tolerant power converter.

Full-size converter operation of hydro power generators: a state-of-the-art review of motivations, solutions, and design implications

This paper reviews motivations and solutions for variable-speed operation in large hydro power plants with a special emphasis on full-size converter operated synchronous generators. First, the established concepts of conventional pumped storage power plants are briefly described. Then, the implemented applications with use of power converters and synchronous machines in hydro power plants, their power ratings, power converter topologies used, and the experiences obtained during operation are reviewed. Concerning its state-of-the-art position in variable-speed pumped storage power plants, the variable-speed capability offered by doubly-fed induction machines is also briefly described, including the power range that can be achieved in pumping mode as well as the power converter ratings of existing power plants. Following this comprehensive analysis, this paper identifies the requirements of today’s power converters and synchronous machines for utilization in large pumped storage power plants as full-size converter operated synchronous generators. It analyzes the design implications on the electric machines driven by such converters, and investigates the advantages of the additional possibilities given by the full-size converter operation that may outweigh the added cost, system complexity, and power loss.

Pareto-based modulated model predictive control strategy for power converter applications

Modulated model predictive control (M2PC) allows fixed switching frequency operation of power converters, producing lower ripple and lower total harmonic distortion (THD) in the output signals than those obtained using regular model predictive control (MPC) algorithms. However, the design of the M2PC algorithm and its performance depend on, among other factors, the tuning of weighting factors, which are required by the cost functions typically used in predictive control algorithms. In this paper, a novel Pareto-based multi-objective M2PC (MO-M2PC) strategy is proposed. In this case, the use of weighting factors is not required, and the optimization problem is solved using a multi-objective approach. The aim of the proposed MO-M2PC strategy is to consider practical rules, such as satisfaction of soft constraints, to calculate the control actions. The proposed Pareto-based MO-M2PC strategy can be applied to any power converter topology. In this paper, experimental validation of the proposed methodology is pursued using a 3-phase 3 kW power converter operating as a shunt active power filter (SAPF). The proposed control is implemented in a control platform based on the dSPACE ds1103 system. The simulation and experimental results demonstrate the advantages and flexibility achieved by the proposed Pareto-based MO-M2PC.

Recently Developed Reduced Switch Multilevel Inverter for Renewable Energy Integration and Drives Application: Topologies, Comprehensive Analysis and Comparative Evaluation

Recently, multilevel inverters (MLIs) have gained lots of interest in industry and academia, as they are changing into a viable technology for numerous applications, such as renewable power conversion system and drives. For these high power and high/medium voltage applications, MLIs are widely used as one of the advanced power converter topologies. To produce high-quality output without the need for a large number of switches, development of reduced switch MLI (RS MLI) topologies has been a major focus of current research. Therefore, this review paper focuses on a number of recently developed MLIs used in various applications. To assist with advanced current research in this field and in the selection of suitable inverter for various applications, significant understanding on these topologies is clearly summarized based on the three categories, i.e., symmetrical, asymmetrical, and modified topologies. This review paper also includes a comparison based on important performance parameters, detailed technical challenges, current focus, and future development trends. By a suitable combination of switches, the MLI produces a staircase output with low harmonic distortion. For a better understanding of the working principle, a single-phase RS MLI topology is experimentally illustrated for different level generation using both fundamental and high switching frequency techniques which will help the readers to gain the utmost knowledge for advance research.

Hybrid energy storage system for microgrids applications: A review

Abstract Energy storages introduce many advantages such as balancing generation and demand, power quality improvement, smoothing the renewable resource’s intermittency, and enabling ancillary services like frequency and voltage regulation in microgrid (MG) operation. Hybrid energy storage systems (HESSs) characterized by coupling of two or more energy storage technologies are emerged as a solution to achieve the desired performance by combining the appropriate features of different technologies. A single ESS technology cannot fulfill the desired operation due to its limited capability and potency in terms of lifespan, cost, energy and power density, and dynamic response. Hence, different configurations of HESSs considering storage type, interface, control method, and the provided service have been proposed in the literature. This paper comprehensively reviews the state of the art of HESSs system for MG applications and presents a general outlook of developing HESS industry. Important aspects of HESS utilization in MGs including capacity sizing methods, power converter topologies for HESS interface, architecture, controlling, and energy management of HESS in MGs are reviewed and classified. An economic analysis along with design methodology is also included to point out the HESS from investor and distribution systems engineers view. Regarding literature review and available shortcomings, future trends of HESS in MGs are proposed.

Control of Single Stage Grid Tied Photovoltaic Inverter Using Incremental Conductance Method

In this investigation, a study on grid-connected Photovoltaic (PV) system with single stage power conversion (SSPC) is proposed. Double Stage Power Conversion (DSPC) topology contains two power conversion stages namely DC-DC conversion and DC-AC conversion, but the SSPC system converts DC power to high-quality AC power supply for grid connected PV system. The SSPC system has several advantages over DSPC, such as better use of the PV arrays, higher efficiency, low cost and compact size. Present work proposes a Sinusoidal Pulse Width Modulation (SPWM) along with incremental conductance Maximum Power Point Tracking (IC-MPPT) for inverter switching. The PV voltage and Grid Voltages verifies under normal and change of atmospheric conditions using MATLAB / SIMULINK.

Three-Level Two-Stage Decoupled Active NPC Converter With Si IGBT and SiC MOSFET

This paper presents the operation principle and benefits of a novel power converter topology named three-level two-stage decoupled active neutral point clamped (3L-TDANPC) converter, which is implemented based on a hybrid utilization of silicon (Si) insulated gate bipolar transistors (IGBTs) and silicon carbide (SiC) metal-oxide semiconductor field-effect transistors (mosfets). The 3L-TDANPC converter can achieve high efficiency with limited number of SiC mosfet modules while keeping balanced loss distribution among the switching devices, which helps increase the converter power ratings. In addition, in this 3L-TDANPC converter, the SiC mosfet has a potential to ride through short-circuit fault because of the presence of Si IGBTs. The key challenges that are associated with system resonant current are investigated and the methods to damp such resonant current are proposed and explained in detail. The simulation and experimental results based on a 1-MW 3L-TDANPC converter prototype confirm the expected benefits of this proposed converter and the effectiveness of the proposed resonant current damping methods.

Five-Level E-Type Inverter for Grid-Connected Applications

Nowadays, a multilevel converter represents a good idea for commercial and industrial applications, where small size and cost, low maintenance, reliability in a wide range of environments, and good efficiency are required. Furthermore, the multilevel converter can provide control for both maximum power tracking and output power factor reducing the filter weight and volume. The proposed power converter topology, called five-level E-type inverter (5L E-Type Inverter), for grid-connected applications is presented and analyzed in this paper. The performance of the three-phase 5L E-Type Inverter has been theoretically investigated. The thermal models of the power semiconductor have been created taking into account the parameters provided by the manufactures and employing multidimensional lookup tables in the Plexim/PLECS environment. The design and selection of passive components have been described in order to obtain amazing performances in terms of weight, volume, and efficiency and power quality. New control strategy, named concurrent control, for 5L E-Type Inverter has been implemented and validated in the LabVIEW development environment. The peak efficiency of the converter above 98.3% and the total harmonic total harmonic distortion current ( THDi ) less than 3% have been achieved.

Transformer Isolated SCALDO Based High Current DC Power Supply

With increasing component count inside the microprocessor, computer has become a power hungry device and powering IT equipment is one of the largest operating expenses and challenge for data centre in USA. According to the data published by Electric Power Research Institute (EPRI), USA global data centres cloud power market is expanding at over 10 percent annually to reach 200 billion kilowatt-hour energy consumption by 2020. Reducing power loss by 1% inside a server power supplies could result in 2 billion kilowatt-hour energy saving.SCALDO is a patented technique developed by the power electronics research group, University of Waikato which improves the efficiency of low drop-out regulators. This technique can be used inside silver box power supplies to enhance the quality of the output power. Practically realising some SCALDO configuration is challenging due to its large switch count. Novel power converter topology presents in this paper helps SCALDO to be used efficiently inside silver box power supplies with electrical isolation and reduced number of switches.

Discrete Model-Predictive-Control-Based Maximum Power Point Tracking for PV Systems: Overview and Evaluation

The main objective of this work is to provide an overview and evaluation of discrete model-predictive control (MPC)-based maximum power point tracking (MPPT) for photovoltaic systems. A large number of MPC-based MPPT methods have been recently introduced in the literature with very promising performance; however, an in-depth investigation and comparison of these methods has not been carried out yet. Therefore, this paper has set out to provide an in-depth analysis and evaluation of MPC-based MPPT methods applied to various common power converter topologies. The performance of MPC-based MPPT is directly linked with the converter topology, and it is also affected by the accurate determination of the converter parameters; sensitivity to converter parameter variations is also investigated. The static and dynamic performance of the trackers is assessed according to the EN 50530 standard, using detailed simulation models, and validated by experimental tests. The analysis in this work aims to present useful insight for practicing engineers and academic researchers when selecting the maximum power point tracker for their application.

An Advanced Three-Level Active Neutral-Point-Clamped Converter With Improved Fault-Tolerant Capabilities

A resilient fault-tolerant silicon carbide (SiC) three-level power converter topology is introduced based on the traditional active neutral-point-clamped converter. This novel converter topology incorporates a redundant leg to provide fault tolerance during switch open-circuit faults and short-circuit faults. Additionally, the topology is capable of maintaining full output voltage and maximum modulation index in the presence of switch open and short-circuit faults. Moreover, the redundant leg can be employed to share load current with other phase legs to balance thermal stress among semiconductor switches during normal operation. A 25-kW prototype of the novel topology was designed and constructed utilizing 1.2-kV SiC metal–oxide–semiconductor field-effect transistors. Experimental results confirm the anticipated theoretical capabilities of this new three-level converter topology.

An improved topology for high power soft-switched power converters

The push to higher switching frequencies and a desire for lower losses in high power converters requires that switching losses be significantly reduced. Resonant, soft-switching technologies such as the ARCP (Auxiliary Resonant Commutated Pole) attempt to minimize power converter losses by switching the semiconductors at zero voltage or zero current. Deficiencies, however, exist in current ARCP topologies. A novel configuration has been demonstrated that achieves better performance than a conventional ARCP while maintaining essentially the same efficiency and nearly the same power density. This paper describes our new approach and gives simulation and experimental results. A 10 kW, 3-phase inverter, used primarily for driving induction motors, has been constructed and used to experimentally verify the concept.

A New Inductive Power Transfer Topology Using Direct AC–AC Converter With Active Source Current Waveshaping

Generally, in wireless inductive power transfer (IPT) system, the power is processed through multiple power transfer stages and this leads to lower efficiency and higher cost of the system. Recent research shows that the use of a direct ac–ac converter in an IPT system compensates these limitations significantly. However, one of the major challenges of the IPT circuit with direct ac–ac converter is to achieve multiple control goals through a single converter. These include load power requirement, maintaining high-quality source current and achieving soft switching of inverter switches, etc. In the existing literatures, the research is more focused on meeting load power requirement and soft switching of inverter switches. The major focus of this paper is to propose, analyze, and control a new IPT power converter topology using current-fed direct ac–ac converter. Compare with existing buck derived, i.e., voltage source ac–ac converter topologies, the proposed topology is boost derived; therefore, active source current waveshaping is easily obtained. The complete control is carried out through two loops, where the outer output current loop ensures load requirements and inner loop maintains the high-quality grid current. The detail of steady-state and dynamic analysis and design procedure of the converter is presented. Experimental results obtained from a 1.2-kW lab-build prototype are included to verify the analysis and proposed control.

A Building Block IC for Designing Emerging Hybrid and Multilevel Converters

This paper introduces a practical power management integrated circuit (IC) building block, i.e., IC module, which enables the implementation of various emerging hybrid and multilevel power converter topologies in low-power high-frequency applications, operating at switching frequencies up to 10 MHz. Compared to conventional buck- and boost-based topologies, the emerging multilevel and hybrid converters offer significant volume reduction and power processing efficiency improvements. These key factors are significant contributions for modern portable and/or small footprint electronics devices, where size is of great concern. The IC building block (ICBB) consists of two segmented half bridges as well as all the elements needed for implementing mixed-signal current programmed mode (CPM) control. Mixed-signal CPM compatibility coupled with a segmented power stage not only provide inherent current protection and simple controller implementation but also allows for dynamic efficiency optimization. Operation at high-switching frequencies and simple modular design with ICBB are enabled through the development of novel architectures for key functional blocks of the ICBB and a cost-effective solution for level shifting, providing communication between external control signals and module inputs. For example, solutions for high-frequency low-power current sensing and fast digital-to-analog conversion are introduced as well as a capacitive coupling and coding schemes for data transfer. Several identical custom-designed ICBB modules are fabricated in the 0.13- $\mu \text{m}$ CMOS process, each providing up to 2 W of output power, while operating at a switching frequency of up to 10 MHz. The versatility and proper functionality of these modules are verified through simulation and experimental results.

Emerging energy sources for electric vehicle charging station

The fossil fuels which are the source of energy for the traditional vehicles have their reserves on the verge of extension. Also, exhaust gases from these vehicles are degrading the environment by increasing the content of greenhouse gases. To combat these issues, the electric vehicles (EVs) are emerging as a new mode of transportation. In recent research articles, the EV charging stations (EVCSs) are consuming power from either the grid or a solar grid system. If the EV is charged from grid, then it should not be considered environment-friendly as grid power is mostly generated by burning coal. In the long run, if EVs come in bulk grids, they would get overloaded, thus affecting the power quality. The efficient energy management of sources available for charging is mandatory for the persistence of these vehicles. The paper aims to rectify energy crisis by suggesting alternative sources for energising the EVCS. A new hybrid system consisting of PV, WTG and fuel cells is proposed. This system is independent of the grid supply. Hence, even with increasing inrush of EVs, the power quality of grid will not suffer. In this paper, an exhaustive review of different topologies of power converters for EVCS and their comparison are carried out. Furthermore, envisaging the future of RES for the charging station to ensure sustainable development.

An Interleaved-Stage AC–DC Modular Cascaded Multilevel Converter as a Solution for MV Railway Applications

This paper proposes an interleaved-stage ac–dc bidirectional power converter topology feasible to medium-voltage railway systems. It is based on an arrangement that uses input-series-output-parallel configuration with identical power modules. Each module consists of two interleaved legs employing coupled windings so that it is possible to connect a medium-frequency transformer. The topology conception is presented, followed by the adopted control and modulation technique. An estimation of semiconductor losses is also discussed, while a comparative analysis by means of simulation results validates the improved performance of the introduced approach if compared with similar solutions. The topology results are obtainedt through a medium-voltage high-power railway application, demonstrating the converter functionalities and performance under both steady-state and dynamic conditions. It is then possible to state that good performance in terms of efficiency is achieved even though the power stage presents higher component count if compared with the topology that presents the best result, thus making it suitable to high-power ac–dc machine drive applications.

A novel hybrid boost converter with extended duty cycles range for tracking the maximum power point in photovoltaic system applications

Nowadays, a large number of power conversion applications is commonly based on DC/DC converters with high voltage boost capability. Different voltage-boosting techniques have been reported in the literature. Each technique has its own merits and demerits depending on the application, cost, complexity, power density, reliability and efficiency. To meet the growing demand for such applications, new power converter topologies are continuously being proposed. This paper focuses on a novel hybrid boost converter, which combines the conventional boost (CB) and the quadratic boost (QB). This new topology allows the extension of the output voltage gain and the duty cycle range regarding to the original topologies. Thus, it ensures high conversion voltage ratio for almost duty cycle values. Consequently, it has two working modes, one as QB mode and the other one as CB mode. In order to verify the performance of the proposed topology, several simulations have been carried out under Matlab/Simulink environment for both QB and CB modes. The well-known P&O algorithm was implemented into a FPGA (Field Programmable Gate Array) board in order to verify experimentally the designed hybrid boost. Experimental results confirm the convenience of the proposed topology for tracking the maximum power point in photovoltaic systems.