Switching Legs Research Articles

Design and Comparison of a 10-kW Interleaved Boost Converter for PV Application Using Si and SiC Devices

Grid-connected photovoltaic (PV) inverters have a dc/dc converter connected to the PV for executing the maximum power point tracking. The design of an interleaved boost converter (IBC) with three switching legs for a 10-kW PV inverter is presented in this paper. This paper shows how the use of silicon carbide (SiC) switches and powdered iron core inductors enables the operation of the converter at a higher switching frequency and when increasing the converter power density. The IBC is designed using a 1.2-kV SiC MOSFET and Schottky diodes and Kool Mμ powdered iron inductors. The design is compared with an IBC built with a silicon (Si) IGBT, fast recovery Si diodes, and ferrite cores. The use of SiC devices reduces the switching loses drastically and there are no reverse recovery losses, resulting in improved efficiency. The higher frequency and higher saturation flux density of the powdered iron core enable the reduction in core size by three times. A 10-kW prototype is built and tested for both the Si and SiC designs and compared with theoretical estimations.

The Reaction Mass Biped: Geometric Mechanics and Control

Inverted Pendulum based reduced order models offer many valuable insights into the much harder problem of bipedal locomotion. While they help in understanding leg behavior during walking, they fail to capture the natural balancing ability of humans that stems from the variable rotational inertia on the torso. In an attempt to overcome this limitation, the proposed work introduces a Reaction Mass Biped (RMB). It is a generalization of the previously introduced Reaction Mass Pendulum (RMP), which is a multi-body inverted pendulum model with an extensible leg and a variable rotational inertia torso. The dynamical model for the RMB is hybrid in nature, with the roles of stance leg and swing leg switching after each cycle. It is derived using a variational mechanics approach, and is therefore coordinate-free. The RMB model has thirteen degrees of freedom, all of which are considered to be actuated. A set of desired state trajectories that can enable bipedal walking in straight and curved paths are generated. A control scheme is then designed for asymptotically tracking this set of trajectories with an almost global domain-of-attraction. Numerical simulation results confirm the stability of this tracking control scheme for different walking paths of the RMB. Additionally, a discrete dynamical model is also provided along-with an appropriate Geometric Variational Integrator (GVI). In contrast to non-variational integrators, GVIs can better preserve energy terms for conservative mechanical systems and stability properties (achieved through energy-like lyapunov functions) for actuated systems.

Dual-buck residential photovoltaic inverter with a high-accuracy repetitive current controller

This paper describes a dual-buck inverter (DBI) for residential photovoltaic power conversion systems. The DBI consists of unidirectional and bidirectional switching legs, which are operated at different frequencies to attain high efficiency. The operation modes of the DBI are analyzed and a third- order control model is derived based on the analysis. Since the third-order model cannot be easily handled by the current controller design, a simple first order-model is obtained with proper assumptions and manipulations. After this, a repetitive current controller using the first-order model is designed to improve the accuracy of the current regulation in both continuous and discontinuous conduction modes. Due to the universal operation of the designed repetitive controller, the tracking accuracy for a low power reference is drastically enhanced, and this significantly improves the maximum power point tracking (MPPT) ability of the PV system. In order to verify the performance of the proposed scheme, a 3-kW DBI prototype was built and tested. The experimental results demonstrate that the proposed scheme not only reduces the total harmonic distortion of the output current, but also achieves highly accurate power tracking performance with high efficiency.

Analysis on Load-Adaptive Phase-Shift Control for High Efficiency Full-Bridge LLC Resonant Converter Under Light-Load Conditions

Recently, the full-bridge (FB) LLC resonant converter is getting more attention due to its zero-voltage switching of the primary switches, zero-current switching of rectifier diodes, and high power capability. However, the conversion efficiency is degraded under light-load conditions due to the core loss in magnetic components and the switching loss in semiconductor devices. In this paper, a new control method is proposed for the FB LLC resonant converter. In the proposed method, the frequency control is basically used to regulate the output voltage over entire load conditions. Moreover, the proposed method utilizes phase-shifted gate signals between switch legs, based on predetermined optimal duty ratio under light-load conditions. At this point, the optimal duty ratio is determined to get minimum power loss under each light-load condition through the loss analysis of all components. Therefore, the proposed method makes high efficiency under light-load conditions. To confirm the validity of this paper, the prototype of the network power supply with 320-385 V dc input and 48 V/720 W dc output is tested.

A ZVS Pulsewidth Modulation Full-Bridge Converter With a Low-RMS-Current Resonant Auxiliary Circuit

This paper presents the description and analysis of a phase-shift-modulated full-bridge converter with a novel robust passive low-rms-current resonant auxiliary circuit for zero-voltage switching (ZVS) operation of both the leading and lagging switch legs. Detailed time-domain analysis describes the steady-state behavior of the auxiliary circuit in different operating conditions. An in-depth comparative study between a fully specified baseline converter and the equivalent converter using the proposed resonant auxiliary circuit is presented. For a similar peak auxiliary current to ensure ZVS operation, a minimum of 20% reduction in rms current is obtained, which decreases the conduction losses. Key characteristics and design considerations are also fully discussed. Experimental results from a 750-W prototype confirm the predicted enhancements using the proposed resonant auxiliary circuit.

Single pole switch leg based multi‐port converter with an energy storage

This study presents a new multi-functional control system for a multi-port energy converter that interfaces one bi-directional battery port, one dc input port, and three output ports. Only one single-leg active switching element (a module type can be used) is employed in the system, and hence the single leg requires digital switching signals for a multi-functional operation to regulate output voltages and to simultaneously manage the battery port. The proposed system has buck-boost conversion capabilities to accommodate wide range, various input sources and output loads. In addition, the single leg requires no dead time due to an integrated impedance network, which will improve the system reliability and performance. Furthermore, the proposed structure can charge a battery even when the input and capacitor voltages are much lower than the battery voltage and hence it significantly improves charging behaviours. The proposed multi-functional control strategy and the converter structure are explained in detail. Then the feasibility and performance of the converter are verified both by computer simulations and experiments based on the Texas Instruments TMS320F28335 digital signal processor.

A State Machine Decoder for Phase Disposition Pulsewidth Modulation of Three-Phase Coupled-Inductor Semi-Bridge Converters

Coupled-inductor semi-bridge converters, assembled from magnetically linked pairs of complementary unidirectional phase legs, can achieve a substantially improved harmonic output voltage performance with the same number of silicon devices as traditional converters. However, they must be operated so as to ensure that a continuous common-mode current always flows through each coupled inductor, to ensure each phase leg can always produce the required switched output voltage. This is particularly challenging for a three-phase coupled-inductor bridge controlled by phase disposition (PD) modulation, since there is no direct correlation between the modulator output and the individual phase leg switching device commands. This paper presents a novel strategy to control each phase leg’s common-mode inductor current under PD modulation, by introducing a square wave offset signal into the modulator reference command, and feeding the modulator output through a postprocessing state machine to correctly switch each semi-bridge phase leg to maintain the required dc common-mode current. The strategy has been verified by detailed simulation studies and matching experimental results.

Control Strategy for Single-Phase Transformerless Three-Leg Unified Power Quality Conditioner Based on Space Vector Modulation

The unified power quality conditioner (UPQC) is known as an effective compensation device to improve PQ for sensitive end-users. This paper investigates the operation and control of a single-phase three-leg UPQC (TL-UPQC), where a novel space vector modulation method is proposed for naturally solving the coupling problem introduced by the common switching leg. The modulation method is similar to the well-known space vector modulation widely used with three-phase voltage source converters, which thus brings extra flexibility to the TL-UPQC system. Two optimized modulation modes with either reduced switching loss or harmonic distortion are derived, evaluated, and discussed, in order to demonstrate the flexibility brought by the space vector modulated TL-UPQC. Simulations and experimental results are presented to verify the feasibility and effectiveness of the proposed space vector modulation approach as well as two mentioned modulation modes.

Two‐level three‐phase voltage source inverter fed low‐power AC induction motor based on unipolar pulse‐width modulation method

Space vector modulation is a well-established theory. Generally, a three-phase voltage source inverter generates eight switching states, including six active and two zero states, by the bipolar method. This study proposes a novel way to synthesise the output voltage vector by turning off both switches in a leg. Accordingly, new leg switching states are defined. A unipolar method is used to achieve discontinuous pulse-width modulation. The complex reference vector is located by one active vector and two newly defined leg switching states. The most notable features of the proposed method are that it completely overcomes the problem of dead time without current polarity detection. These features make it very attractive for low-cost, low-power constant volts per hertz (V/f), open-loop, three-phase AC induction motor applications.

Design and Implementation of Modified Buck Boost Converter Fed B4 Inverter for Brushless Dc motor Drive using Low Cost DSPIC Controller

The Research deals with the speed control of Brushless DC Motor drive by low cost dsPIC controller and B4 Inverter with new converter design (Four Switch Inverter) rather than conventional inverter (Six Switch Inverter) is proposed. The conventional Six switch Inverter is modified into B4 Inverter in order to reduce the switch leg failure, and Total Harmonic Distortion. This facilitates the operation of voltage source Inverter at fundamental frequency switching by using the Electronic commutation technique rather than Mechanical commutation. In addition we propose single phase Rectifier and Three phase voltage source Inverter, dsPIC controller to generate the multiple carrier PWM pulses for B4 Inverter which is fed to the Permanent Magnet Brushless DC Motor to obtain the desired motor speed. The proposed Research mainly focused on the new topology of Buck boost converter design for B4 inverter, By this new modified buck boost Enhancement converter design motor speed are controlled and voltage imbalance in the capacitors are avoided the capacitor voltage is similar voltage level is obtained during the buck and the boost mode operation of the converter side, So results with improved quality of Boosted up output DC Power is obtained. Simulation Modeling Results are carried out by Matlab/Simulink environment and Portable Experimental Hardware is developed Results are carried out Sucessfully and Validated for various operating parameter conditions.

PWM Plus Secondary-Side Phase-Shift Controlled Soft-Switching Full-Bridge Three-Port Converter for Renewable Power Systems

In this paper, a pulsewidth modulation (PWM) plus secondary-side phase-shift (SSPS) controlled full-bridge three-port converter (FB-TPC) is proposed for a renewable power system, which is derived by integrating two interleaved buck/boost circuits (IBBC) and a SSPS full-bridge converter (FBC), to interface the energy source, energy storage element, and output load simultaneously. The two switching legs are shared by the IBBC and FBC, which improves the active devices sharing ratio and power density. With PWM plus SSPS control scheme, decoupled power control can be realized and the converter can achieve wide input voltage range power conversion. In addition, zero-voltage switching (ZVS) of both the primary and secondary switches are achieved in a wide range. Furthermore, the circulating current can be greatly eliminated, which helps to reduce conduction losses. Moreover, the voltage stresses on the secondary rectifier are effectively suppressed since the power switches and diodes are clamped to output voltage. The operation principles, output characteristics, ZVS performances, and control strategy are analyzed in detail. Experimental results of a 600-W prototype are provided to verify the effectiveness and the advantages of the proposed converter.

A Novel Three-Level Hysteresis Current Regulation Strategy for Three-Phase Three-Level Inverters

This paper presents a new hysteresis current regulation strategy for the neutral point clamped and flying capacitor (FC) three-level inverters. The strategy uses the measured average of the switched phase leg output voltage to adjust the controller hysteresis band as the load back EMF varies to maintain a near constant phase leg switching frequency. The phase leg switchings are then fine tuned to a fixed frequency clock to further improve frequency regulation. Next, the zero-crossings of the measured phase leg average voltages are used to select between positive and negative switched output voltage levels, so that only one hysteresis current regulator is required for the full inverter switched output voltage range. For the FC inverter, a state machine is then added to select between redundant switching states to maintain balanced capacitor voltages. Finally, the controller is extended to a three-phase system by subtracting the common mode interacting current from the total phase leg current error before making any switching decision. The resulting controller achieves a line-to-line harmonic performance that is very close to open-loop phase disposition pulse width modulation, while retaining all of the dynamic benefits of hysteresis current regulation.

Cascaded three‐phase pulse‐width modulated switched voltage source inverter

A cascaded three-phase pulse-width modulated (PWM) switched voltage source inverter topology is proposed. Each of the two cascaded units in a phase-leg is an H-bridge, whose switch legs are separated by a switched capacitor and a diode. Three upper H-bridges in this inverter configuration have separate dc inputs; whereas the lower three H-bridges share a common dc input. A single-carrier, multilevel PWM scheme is employed to generate the gating signals for the power switches. The implemented modulation scheme is hybridised to enable the output voltage of the proposed inverter configuration inherit the features of switching-loss reduction from fundamental PWM, and good harmonic performance from multiple sinusoidal PWM. A sequential switching scheme is embedded with the already employed hybrid modulation in order to overcome unequal switching losses. Furthermore, a simple base PWM circulation scheme is also introduced to get a resultant sequential switching hybrid PWM circulation that balances power dissipation among the two cascaded power modules. The proposed inverter configuration was subjected to an R–L load. Fast Fourier transform analyses of the output voltage waveforms gave total harmonic distortion value of 12.64%. Simulations and experiments are carried out on a 4.89 kW rated prototype of the proposed inverter.

Resonance based zero‐voltage zero‐current switching full bridge converter

A zero-voltage and zero-current switching full bridge converter with series resonance tank is presented in this study. This converter is based on standard full bridge topology and a series capacitor is added in the primary side to reset the leakage inductance current without any additional auxiliary circuit. Leakage inductance of the transformer is used as the resonance inductance. Using series resonance tank and applying control pulses with fix frequency, zero-voltage switching for leading leg and zero-current switching for lagging leg is achieved. The output power is controlled using phase shift technique. In the proposed converter, soft-switching condition is attained for wide range of load variation. Due to its high performance and minimum additional components with respect to regular converter, this converter can be applied for medium to high-power applications. Topology and operating modes are discussed and the validity of theoretical analysis is verified by prototype experimental results.

Multiport Converters Based on Integration of Full-Bridge and Bidirectional DC–DC Topologies for Renewable Generation Systems

A systematic method for deriving multiport converters (MPCs) from the full bridge (FB) converter (FBC) and bidirectional dc-dc converters (BDCs) is proposed in this paper through sharing the parasitized switching legs by the BDCs and the FBC. By employing the proposed method, families of FB and BDC-based MPCs (FB-BDC-MPCs), including some existing ones, are developed for renewable generation systems with the merits of simple topology, reduced devices, and single-stage power conversion. Voltage regulations between any two ports can be achieved by employing pulsewidth modulation and phase-angle-shift control scheme. Furthermore, zero-voltage switching for all the switches can be realized in the proposed FB-BDC-MPCs. A typical four-port converter developed by the proposed method, named buck/boost four-port converter (BB-FPC), is analyzed in detail as an example in terms of operation principles, design considerations, and control strategy. Experiments have been carried out on a 500-W prototype of BB-FPC, which demonstrate the feasibility and effectiveness of the proposed topology derivation method.

Thermal and Efficiency Analysis of Five-Level Multilevel-Clamped Multilevel Converter Considering Grid Codes

In this paper, a five-level multilevel-clamped multilevel converter (5L- MLC <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) topology is analyzed based on a typical grid integration application for renewable energy system. The loss and thermal distributions of the power devices in different switching legs are investigated and illustrated under rated condition. Afterward, a loss and efficiency evaluation method is proposed and applied which takes into account various injected reactive power ranges regulated by the grid codes. It is concluded that the loss and thermal distributions of the 5L- MLC <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> multilevel topology are unequal between the clamping switching legs and the main switching legs; it also shows a good and consistent efficiency characteristic under different output power ranges when complying with the grid codes.

Series-Input Interleaved Forward Converter With a Shared Switching Leg for Wide Input Voltage Range Applications

A method for extending the duty cycle range of series-input interleaved forward converter (SII-FC) is proposed in this paper. A family of novel SII-FC topologies is derived by integrating two switching legs, which belong to two forward cells, into one switching leg shared by both the two forward cells in the SII-FC. By employing the proposed method, the derived topologies have the advantages of extended duty cycle, reduced components, and conduction losses, which help to achieve high power density and high efficiency. These advantages make the SII-FC topologies suitable for such applications with wide input voltage range. A series-input interleaved two-switch forward converter (SII-TS-FC) is analyzed in detail, which is a typical SII-FC topology developed by the proposed method. It is composed of two low-voltage switching legs and a high-voltage switching leg. Detailed analysis indicates that the maximum duty cycle of the SII-TS-FC can reach 2/3, which is 1.33 times of that of the two-switch forward converter. The switches of the high-voltage leg can be soft-switched when duty cycle is less than 0.5, while the switches of the low-voltage legs can be soft-switched when duty cycle is larger than 0.5. As a result, high efficiency is achieved over a wide voltage range. In addition, the output filter can be reduced due to the interleaving operation of the two forward cells. The operational principles, characteristics, and design considerations for the proposed SII-FC are presented. Experimental results on the SII-TS-FC prototype with 200-400 V input 48 V/12 A output verify the proposed method and analysis.

Low-Common Mode Voltage H-Bridge Converter with Additional Switch Legs

H-bridge converter with additional switch legs (HA converter) and its offspring circuit are proposed in this paper with the intent to reduce the common mode noise. The proposed topology connects grounds of the input and output terminals, which gives zero common mode current in the ideal case. The operation of the proposed circuit is flexible and allows for the circuit to be capable of both ac–dc and dc–ac conversions. The proposed topology is especially advantageous when it is applied to the photovoltaic power conditioning system in dc distribution system or stand-alone power system because they include large stray capacitances and are prone to common mode EMI. In this paper, a 4-switch HA (HA4S) converter for both ac–dc rectification and dc–ac inversion is derived from the proposed HA converter as the implementation example. The experimental results based on the proposed and the conventional prototype circuits prove that the HA4S converter outperforms the conventional counterparts.

A Simplified Power Conditioner Based on Half-Bridge Converter for High-Speed Railway System

With the rapid development of high-speed and high-power railway system in China, power quality such as the negative sequence current and harmonic current caused by electric locomotives becomes more and more critical. This paper proposes a half-bridge-converter-based railway static power conditioner (RPC) (HBRPC) which consists of two half-bridge converters connected by two capacitors in series. Compared with the traditional RPC, the HBRPC requires only a pair of power switch legs and two capacitors. Under the premise of accomplishing the same function of RPC, the proposed conditioner can reduce half of the power switches, which can make it with lower cost and hardware complexity. A double-loop control is proposed for HBRPC to keep the dc-link voltage stable and achieve the dynamic tracking of the current reference signals, while a balanced voltage control is proposed to eliminate the error of two capacitor voltages and maintain the normal operation of HBRPC. Finally, simulation and experiment results have verified the proposed structure and its control method effectively.

New topology for management of bi-directional power flow between vehicle and grid with reduced ripple current at unity power factor

In this paper, a new topology of single-phase pulse width modulated (PWM) AC-DC converter is proposed for bidirectional power flow between plug-in hybrid electric vehicle (PHEV) and the grid. This converter consists of a PWM voltage source converter (VSC) and a ripple reduction circuit. The ripple reduction circuit consists of a switching leg and an inductor. The inductor is connected between the midpoints of the second and third legs of VSC. An AC voltage of 230 V, 50 Hz is converted into 400 V DC using a single-phase VSC with ripple compensation circuit. A buck-boost DC-DC converter charges and discharges the battery of the electric vehicle (EV) or PHEV with this 400 V DC. While in discharging mode, it feeds energy back to the grid. The zero voltage regulation (ZVR) and power factor correction (PFC) modes of operation at PCC are also achieved with reactive power compensation and harmonics elimination of other connected loads at PCC with modified control in order to improve the power quality at the grid.