Proposed Converter Topology Research Articles

Modular multilevel converter with DHB energy‐balancing channels for medium‐voltage adjustable‐speed drives

This paper presents a modular multilevel converter (MMC) configuration that utilises energy exchange between submodules (SMs) of upper and lower arms, for energy rebalancing. The configuration is applicable to mediumvoltage high-power variable-speed drives with any number of motor phases, where the traditional MMC topology experiences challenging shortcomings. With the out-of-phase alternation of the fundamental ripple power in upper and lower arms, the proposed MMC configuration decouples this ripple power by employing dual half-bridge modules linking opposite SMs in upper and lower arms of the same MMC-leg. This counter-balances arm ripple-power through bidirectional power transfer between opposite SMs, resulting in a reduction in the SM capacitance and the MMC system stored energy. The proposed MMC configuration solves the problem of wide SM capacitor voltage fluctuation, especially at low operating frequencies, where the SM capacitor voltage ripple profile is almost constant, independent of the operating frequency. Therefore, the configuration is able to drive multi-megawatt machines from stand-still to the rated speed, at rated torque. The operation of the proposed converter topology is elucidated in detail, and its effectiveness is verified through simulation and experimentation.

Quasi-Z-source based bidirectional DC-DC converter and its control strategy

This paper presents a quasi-Z-source based isolated bidirectional DC-DC converter (qZIBDC) for renewable energy applications. The converter utilizes a dual active bridge circuit with a quasi-Z-source network on both sides, so the converter works as buck/boost converter from either side. It has a wider input/output voltage operating range, soft-switching capabilities without additional devices, and higher boost capability than a traditional dual active bridge circuit. Apart from that, shoot-through states are incorporated in its operating cycle to boost the input voltage resulting in high reliability of the proposed converter. Due to the symmetrical structure of the circuit, there is no defined high voltage or low voltage side as in traditional isolated bidirectional DC-DC converter. The operating principle and control strategy of the proposed converter are presented. Simulation and experimental results are provided to verify the effectiveness of the proposed converter topology and its control strategy.

Non-isolated Modified Quadratic Boost Converter with Midpoint Output for Solar Photovoltaic Applications

This paper presents a boost DC-DC converter topology with non - isolated high gain and output midpoint, to boost the voltage obtained from solar photovoltaic panels. The three-level boost converter is coupled to the output port of the single-switch quadratic boost converter to derive the proposed converter topology. The voltage gain of the proposed converter is greater than that of the classical boost converter. The voltage stress on the switches of the proposed converter is equal to half of the converter output voltage. Static analysis, operating modes, experimental waveforms in continuous current conduction and discontinuous current conduction modes are shown. A 520 W prototype converter was implemented in the laboratory and its results are presented.

Dual-Switch Boost DC–DC Converter for Use in Fuel-Cell-Powered Vehicles

To facilitate voltage matching between the cell stack and power batteries in fuel-cell-powered vehicles, an implementation of a simple dual-switch boost DC–DC converter topology has been proposed in this paper. Compared with existing boost topologies, the one proposed herein reduces the number of components required and stress induced whilst maintaining a high-gain ratio. The results of experiments performed in this paper reveal that the corresponding to a duty ratio of 0.8, the proposed converter topology demonstrates the realization of a boost ratio of 6, thereby exceeding that the realized by conventional boost converters by nearly 73%. In addition, at an output voltage of 50 V, a maximum operating efficiency of 91% was achieved. These results demonstrate the effectiveness and feasibility of the proposed DC–DC converter topology for use in fuel-cell-powered vehicles.

Constant Frequency Operation of the Parallel Loaded Resonant DC/DC Converter for Power LED Lighting

A DC/DC resonant converter for power LED lighting, controlled with constant frequency by means of the control of the auxiliary transistors' conduction time is presented in the paper. The proposed converter topology allows to relatively high range of its output power changes in comparison to the conventional parallel resonant converter. Comparison between average power losses in semiconductor elements in the converter controlled with a constant frequency and in equivalent converter controlled with a variable frequency is presented to emphasize attractiveness of proposed converter.

Series Active Filter Design Based on Asymmetric Hybrid Modular Multilevel Converter for Traction System

This paper presents a comparative analysis of a new topology based on an asymmetric hybrid modular multilevel converter (AHMMC) with recently proposed multilevel converter topologies. The analysis is based on various parameters for medium voltage-high power electric traction system. Among recently proposed topologies, few converters have been analysed through simulation results. In addition, the study investigates AHMMC converter which is a cascade arrangement of H-bridge with five-level cascaded converter module (FCCM) in more detail. The key features of the proposed AHMMC includes: reduced switch losses by minimizing the switching frequency as well as the components count, and improved power factor with minimum harmonic distortion. Extensive simulation results and low voltage laboratory prototype validates the working principle of the proposed converter topology. Furthermore, the paper concludes with the comparison factors evaluation of the discussed converter topologies for medium voltage traction applications.

Step-Up Partial Power DC-DC Converters for Two-Stage PV Systems with Interleaved Current Performance

This work presents a partial power converter allowing us to obtain, with a single DC-DC converter, the same feature as the classical interleaved operation of two converters. More precisely, the proposed topology performs similarly as the input-parallel output-series (IPOS) configuration reducing the current ripple at the input of the system and dividing the individual converters power rating, compared to a single converter. The proposed topology consists of a partial DC-DC converter processing only a fraction of the total power, thus allowing high efficiency. Experimental results are provided to validate the proposed converter topology with a Flyback-based 100 W test bench with a transformer turns ratio n 1 = n 2 . Experimental results show high performances reducing the input current ripple around 30 % , further increasing the conversion efficiency.

A Reduced Switch Count Three-Phase AC/AC Converter With Six Power Switches: Modeling, Analysis, and Control

Reducing the number of semiconductor switches in power electronics converters has been a continuing effort in recent years as a measure to enhance the system reliability and to decrease its size, weight, and component cost. For these reasons, a new reduced switch count three-phase ac/ac converter is being proposed. Being realized by only six active switches and antiparallel diodes, the proposed converter topology employs the minimum number of semiconductor devices amongst the converters of its kind. It also features unity power factor, regenerative operation, pulsewidth-modulated output voltage, and sinusoidal input current. The reduced number of switches results in a simplified associated gate drive circuit as well as cooling system which, in turn, may reduce the overall manufacturing cost and increase the reliability, especially in low-voltage and low-power applications. The modulation scheme of the new converter is developed, and a control algorithm is proposed for the converter’s rectifier side. Moreover, an analysis is performed on the dc-link capacitor sizing for the purposes of reducing the dc-link voltage ripple, and balancing the input current and lowering its total harmonic distortion. The simulation and experimental results corroborate the transient and steady-state performance of the proposed converter topology.

Power Control With Z-Source Converter Based Unified Power Flow Controller

In this paper, we propose a Z-source converter (ZSC)-based unified power flow controller (ZSC-UPFC) to enhance power control for long transmission lines. As a multifunctional controller, the UPFC has been adopted to regulate both the active and reactive power flows in transmission lines and to control the AC bus voltage. A recently proposed converter topology, ZSC, uses a Z-network on its DC side to support the desired AC output voltage. The proposed ZSC-UPFC configuration places a Z-network between the dc-link capacitor and the series converter to boost the series converter DC voltage. The integration of Z-network provides the desired converter voltage even with reduced dc-link capacitor voltage setting. We develop a detailed three-phase model for the proposed ZSC-UPFC by modeling the converter operation with switching functions, which are generated by the space vector pulse width modulation (SVPWM) technique. We conduct linear analysis on the D-Q model as well as extensive transient simulation (based on a detailed nonlinear three-phase model) to evaluate the performance of the overall system with the proposed ZSC-UPFC configuration. Our simulation results demonstrate the effectiveness of ZSC-UPFC: 1) The series converter provides the series compensation in a long transmission line with Z-network, and 2) the shunt converter maintains a constant dc-link capacitor voltage and provides reactive power support for the AC bus.

A New Family of Multilevel Grid Connected Inverters Based on Packed U Cell Topology

In this paper a novel packed U cell (PUC) based multilevel grid connected inverter is proposed. Unlike the U cell arrangement which consists of two power switches and one capacitor, in the proposed converter topology a lower DC power supply from renewable energy resources such as photovoltaic arrays (PV) is used as a base power source. The proposed topology offers higher efficiency and lower cost using a small number of power switches and a lower DC power source which is supplied from renewable energy resources. Other capacitor voltages are extracted from the base lower DC power source using isolated DC-DC power converters. The operation principle of proposed transformerless multilevel grid connected inverter is analyzed theoretically. Operation of the proposed multilevel grid connected inverter is verified through simulation studies. An experimental prototype using STM32F407 discovery controller board is performed to verify the simulation results.

Series‐connected multi‐half‐bridge modules converter for integrating multi‐megawatt wind multi‐phase permanent magnet synchronous generator with dc grid

In this study, a new transformerless wind energy conversion system to integrate high-power multi-phase permanent magnet wind generators to medium-voltage local grids is presented. The proposed converter topology consists of multi-half-bridge modules with a high ac-direct current (dc) boosting capability. Each phase of an open winding multi-phase generator is connected to the ac side of a half-bridge module, whereas the dc sides of the half-bridge modules are connected in series forming the high-voltage dc-link output. The proposed architecture facilitates the employment of semiconductor switches with a relatively low-voltage rating, which equals the dc-link voltage divided by the number of generator phases. A detailed analysis of the proposed architecture along with the required closed-loop control is presented. The proposed architecture is simulated under different operating conditions using a typical 2 MW system, while the experimental validation is carried out using a low-scale prototype converter.

A Multistage DC-DC Step-Up Self-Balanced and Magnetic Component-Free Converter for Photovoltaic Applications: Hardware Implementation

This article presents a self-balanced multistage DC-DC step-up converter for photovoltaic applications. The proposed converter topology is designed for unidirectional power transfer and provides a doable solution for photovoltaic applications where voltage is required to be stepped up without magnetic components (transformer-less and inductor-less). The output voltage obtained from renewable sources will be low and must be stepped up by using a DC-DC converter for photovoltaic applications. 2 K diodes and 2 K capacitors along with two semiconductor control switch are used in the K-stage proposed converter to obtain an output voltage which is (K + 1) times the input voltage. The conspicuous features of proposed topology are: (i) magnetic component free (transformer-less and inductor-less); (ii) continuous input current; (iii) low voltage rating semiconductor devices and capacitors; (iv) modularity; (v) easy to add a higher number of levels to increase voltage gain; (vi) only two control switches with alternating operation and simple control. The proposed converter is compared with recently described existing transformer-less and inductor-less power converters in term of voltage gain, number of devices and cost. The application of the proposed circuit is discussed in detail. The proposed converter has been designed with a rated power of 60 W, input voltage is 24 V, output voltage is 100 V and switching frequency is 100 kHz. The performance of the converter is verified through experimental and simulation results.

Interleaved Flyback DC-DC Converter Design with 350 W Power Output Using LT 3757 in LT Spice

DC-DC converter becomes one important part in micro-inverter used in solar panel application. Its function is to convert output voltage level of solar panel 42-48 Vdc to a voltage level of 350 Vdc before being converted into an AC voltage at the inverter. The proposed converter topology is a flyback because the number of components used is not too much which can suppress the production cost. In this paper, simulation of flyback converter on the interleaved operating mode with a maximum output power of 350 W using software Ltspicewas conducted. From the simulation results, obtained that by applying a switching frequency of 100 kHz, the obtained value of the components of the primary inductor (LP) 3.3 μH, the secondary inductor (LS) 27 μH, the output capacitor (Cout) 47μF and ripple voltage (Vr) 212.65 mV.

Dyna-C: A Minimal Topology for Bidirectional Solid-State Transformers

This paper presents a topology for bidirectional solid-state transformers with a minimal device count. The topology, referenced as dynamic-current or Dyna-C, has two current-source inverter stages with a high-frequency galvanic isolation, requiring 12 switches for four-quadrant three-phase ac/ac power conversion. The topology has voltage step-up/down capability, and the input and output can have arbitrary power factors and frequencies. Further, the Dyna-C can be configured as isolated power converters for single- or multiterminal dc, and single- or multiphase ac systems. The modular nature of the Dyna-C lends itself to be connected in series and/or parallel for high-voltage high-power applications. The proposed converter topology can find a broad range of applications such as isolated battery chargers, uninterruptible power supplies, renewable energy integration, smart grid, and power conversion for space-critical applications including aviation, locomotives, and ships. This paper outlines various configurations of the Dyna-C, as well as the relative operation and controls. The converter functionality is validated through simulations and experimental measurements of a 50-kVA prototype.

FPGA controlled five level soft switching full bridge DC-DC converter for high power applications

AbstractThe objective of the paper is to develop soft switching for the novel five level full bridge DC-DC converter for high power applications. The use of conventional DC-DC converter is likely to decrease the efficiency because of the hard switching, which generates losses during the switch on/off. This paper mainly deals with the development of zero voltage and zero current switching for five level full bridge DC-DC converter. The proposed topology will provide five level DC-DC output voltage, thereby the size of filter in both input and out sides will get reduced as compared to the existing topologies. By increasing the voltage levels, the stress across each switch and DC filter in the rectifier side will get reduced. Only eight switches are used for generating five levels in the proposed converter topology which reduces cost and also total switching losses, thus improves the overall efficiency of a system and it is very much suitable for high power DC-DC applications. The control signals for the pro...

New Integrated Multilevel Converter for Switched Reluctance Motor Drives in Plug-in Hybrid Electric Vehicles With Flexible Energy Conversion

This paper presents an integrated multilevel converter of switched reluctance motors (SRMs) fed by a modular front-end circuit for plug-in hybrid electric vehicle (PHEV) applications. Several operating modes can be achieved by changing the on-off states of the switches in the front-end circuit. In generator driving mode, the battery bank is employed to elevate the phase voltage for fast excitation and demagnetization. In battery driving mode, the converter is reconfigured as a four-level converter, and the capacitor is used as an additional charge capacitor to produce multilevel voltage outputs, which enhances the torque capability. The operating modes of the proposed drive are explained and the phase current and voltage are analyzed in details. The battery charging is naturally achieved by the demagnetization current in motoring mode and by the regenerative current in braking mode. Moreover, the battery can be charged by the external AC source or generator through the proposed converter when the vehicle is in standstill condition. The SRM-based PHEV can operate at different speeds by coordinating the power flow between the generator and battery. Simulation in MATLAB/Simulink and experiments on a three-phase 12/8 SRM confirm the effectiveness of the proposed converter topology.

Multilevel converter with capacitor voltage actively balanced using reduced number of voltage sensors for high power applications

Capacitor voltage balance control has attracted increasing attention in the studies of cascaded multilevel converters and modular multilevel converters. This study proposes a novel multilevel converter topology based on diode clamped half-bridge cascaded converter for medium/high voltage and high power applications. In this converter, capacitor voltage balancing using clamping diodes is achieved. Thus very little capacitor voltage control code has to be executed by the digital controller. Furthermore, only two voltage sensors are required for the capacitor voltage control, and the control scheme can be designed as simple as that of a two-level converter. The phase shifted pulse width modulation (PWM) method is employed for the converter, and a control strategy for the converter utilised as a static Var generator is presented. The proposed converter and control strategy were simulated with PSIM. Experiments were also carried out with a laboratory prototype. Results showed that the proposed converter topology with capacitor voltage balancing could work effectively. The applied PWM and control method were also validated.

High-Order Resonant Converter Topology With Extremely Low-Coupling Contactless Transformers

Although a large number of typical resonant converter topologies have been developed for use in contactless power transfer applications, these topologies need to be precisely optimized to obtain maximum efficiency and maximum power transferring capacity. High-order resonant power converters with flexible designs are invariably required to develop energy-efficient and cost-effective converter systems. An ideal converter topology can contribute toward realizing efficient converter systems if it is capable of providing an optimized output that is insensitive to load variations, coupling coefficient, type of the wireless transformer used, and other operating conditions. This paper presents a new contactless power converter topology for a low-coupling (0.14) ferrite-core transformer that has low cost, small size, high efficiency, and a wide gap (20 mm). In addition, the merits and demerits of conventional converter topologies are studied herein, and results for these topologies are compared with those for the proposed converter topology.

Centralized Solar PV Systems for Static Loads Using Constant Voltage Control Method

The alternative energy resources, like solar, are always complementary due to environmental changes. Energy generation with the sources such as solar and wind is gaining importance and of that photovoltaic conversion is the main focus of researches due to its promising potential as the electrical source. This paper presents the constant voltage method of control where the output of the converter is maintained constant irrespective of the variations in the irradiance with the high step-up isolated efficient single switch DC-DC converter for the solar PV systems. Constant voltage method of control uses the array of photovoltaic systems as its energy source. The output of the Solar PV systems is nonlinear and has its dependency on temperature and irradiance by which the panel voltage and current varies with the variation in irradiance. Constant voltage control method always operates in such a way that the converter voltage is tried to be maintained constantly to the reference voltage which is set by the user. The system used here utilizes high step single switch isolated DC-DC converter and monitors the voltage continuously by varying the duty cycle to maintain the converter voltage always constant. As a way of improving the performance, both the open and closed loop analysis is done where the closed loop analysis uses the PI controller for its performance. The model is implemented in MATLAB and it accepts the irradiance as the input and outputs the constant voltage from the converter and the feasibility of the proposed converter topology is confirmed with experimental results of the prototype model.

A New Single Phase Single Stage High Frequency AC-DC Converter with Complex Programmable Logic Devices (CPLD) Controller

A new single phase single stage high frequency AC-DC converter with Complex Programmable Logic Devices (CPLD) controller is presented. The digital controller is developed using CPLD. The proposed system utilizes a single-phase AC input supply. The power switching devices in the controlled bridge are controlled by the multiple-pulse Pulse Width Modulation (PWM) switching technique to minimize the low order harmonics present on the AC side of the converter. A low pass filter is incorporated in the circuit to filter out unwanted harmonics and provide a sinusoidal AC supply current. A high frequency transformer with 1:1 ratio is used in the design to provide galvanic isolation for better circuit performance and protection. The optimum operation of transformer core in four quadrant of B-H curve is also considered in the proposed converter topology. A laboratory prototype of the converter is developed and tested. Experimental results are compared with the simulation results to illustrate the effectiveness of the proposed technique.