Showing papers on "H bridge published in 2011"

A New High-Efficiency Single-Phase Transformerless PV Inverter Topology

Abstract: There is a strong trend in the photovoltaic inverter technology to use transformerless topologies in order to acquire higher efficiencies combining with very low ground leakage current. In this paper, a new topology, based on the H-bridge with a new ac bypass circuit consisting of a diode rectifier and a switch with clamping to the dc midpoint, is proposed. The topology is simulated and experimentally validated, and a comparison with other existing topologies is performed. High conversion efficiency and low leakage current are demonstrated.

Pwm control of dual active bridge: Comprehensive analysis and experimental verification

Abstract: The dual-active-bridge (DAB) topology is ideally suited for high-power dc-dc conversion, especially when bidirectional power transfer is required. However, it has the drawback of high circulating currents and hard switching at light loads, if wide variation in input and output is expected. To address these issues, this paper presents a comprehensive analysis and experimental results with pulsewidth-modulation (PWM) control of the DAB. The PWM control is in addition to phase-shift modulation between the two H-bridges. The analysis addresses PWM of one bridge at a time and of both bridges simultaneously. In the latter, five distinct modes arise based on the choice of PWM and load condition. The possibilities are analyzed for optimizing power density and efficiency for low-load operation. Finally, a composite scheme combining single and dual PWM is proposed that extends the soft-switching range down to zero-load condition, reduces rms and peak currents, and results in significant size reduction of the transformer. Experimental results are presented with a 10-kW prototype.

A Hybrid Cascade Converter Topology With Series-Connected Symmetrical and Asymmetrical Diode-Clamped H-Bridge Cells

Abstract: A novel H-bridge multilevel pulsewidth modulation converter topology based on a series connection of a high-voltage diode-clamped inverter and a low-voltage conventional inverter is proposed in this paper. A dc link voltage arrangement for the new hybrid and asymmetric solution is presented to have a maximum number of output voltage levels by preserving the adjacent switching vectors between voltage levels. Hence, a 15-level hybrid converter can be attained with a minimum number of power components. A comparative study has been carried out to present high performance of the proposed configuration to approach a very low total harmonic distortion of voltage and current, which leads to the possible elimination of the output filter. Regarding the proposed configuration, a new cascade inverter is verified by cascading an asymmetrical diode-clamped inverter, in which 19 levels can be synthesized in output voltage with the same number of components. To balance the dc link capacitor voltages for the maximum output voltage resolution as well as synthesize asymmetrical dc link combination, a new multi-output boost converter is utilized at the dc link voltage of a seven-level H-bridge diode-clamped inverter. Simulation and hardware results based on different modulations are presented to confirm the validity of the proposed approach to achieve a high-quality output voltage.

Cascaded H-bridge multilevel converter multistring topology for large scale photovoltaic systems

Abstract: Large scale grid connected photovoltaic (PV) energy conversion systems have reached the megawatt level. This imposes new challenges on existing grid interface converter topologies and opens new opportunities to be explored. In this paper a new medium voltage multilevel-multistring configuration is introduced based on a three-phase cascaded H-bridge (CHB) converter and multiple string dc-dc converters. The proposed configuration enables a large increase of the total capacity of the PV system, while improving power quality and efficiency. The converter structure is very flexible and modular since it decouples the grid converter from the PV string converter, which allows to accomplish independent control goals. The main challenge of the proposed configuration is to handle the inherent power imbalances that occur not only between the different cells of one phase of the converter but also between the three phases. The control strategy to deal with these imbalances is also introduced in this paper. Simulation results of a 7-level CHB for a multistring PV system are presented to validate the proposed topology and control method.

10 kV, 120 A SiC half H-bridge power MOSFET modules suitable for high frequency, medium voltage applications

Abstract: The majority carrier domain of power semiconductor devices has been extended to 10 kV with the advent of SiC MOSFETs and Schottky diodes. The devices exhibit excellent static and dynamic properties with encouraging preliminary reliability. Twenty-four MOSFETs and twelve Schottky diodes have been assembled in a 10 kV half H-bridge power module to increase the current handling capability to 120 A per switch without compromising the die-level characteristics. For the first time, a custom designed system (13.8 kV to 465/√3 V solid state power substation) has been successfully demonstrated with these state of the art SiC modules up to 855 kVA operation and 97% efficiency. Soft-switching at 20 kHz, the SiC enabled SSPS represents a 70% reduction in weight and 50% reduction in size when compared to a 60 Hz conventional, analog transformer.

Comparison of Cascaded H-Bridge and Modular Multilevel Converters for BESS application

Abstract: This paper compares the Cascaded H-Bridge (CHB) converter topology with the Modular Multilevel Converter topology (M2LC) for the use in battery energy storage systems (BESS). Standard modules are examined as well as extended modules allowing an increase in output voltage. Semiconductor and capacitor requirements are evaluated by simulation, and practical considerations are discussed. Experimental results from a laboratory setup of a CHB based BESS are presented.

A Comparison of Symmetrical and Asymmetrical Three-Phase H-Bridge Multilevel Inverter for DTC Induction Motor Drives

Abstract: Earlier studies have pointed out the limitations of conventional inverters, especially in high-voltage and high-power applications. In recent years, multilevel inverters are becoming increasingly popular for high-power applications due to their improved harmonic profile and increased power ratings. Several studies have been reported in the literature on multilevel inverters topologies, control techniques, and applications. However, there are few studies that actually discuss or evaluate the performance of induction motor drives associated with three-phase multilevel inverter. This paper presents then a comparison study for a cascaded H-bridge multilevel direct torque control (DTC) induction motor drive. In this case, symmetrical and asymmetrical arrangements of five- and seven-level H-bridge inverters are compared in order to find an optimum arrangement with lower switching losses and optimized output voltage quality. The carried out experiments show that an asymmetrical configuration provides nearly sinusoidal voltages with very low distortion, using less switching devices. Moreover, torque ripples are greatly reduced.

Digital signal processor implementation and performance evaluation of split capacitor, four-leg and three H-bridge-based three-phase four-wire shunt active filters

Abstract: In this paper a comprehensive study on the three-phase four-wire (3P4W) shunt active power filter (APF) is carried out on the basis of three system configurations. These three two-level voltage source inverter topologies are compared for 3P4W shunt APF, namely, split capacitor (2C), four-leg (4L) and three single-phase H-bridges (3HB). The performance of all three topologies, under an unbalanced non-linear load condition, is evaluated with a detailed digital signal processor (DSP)-based experimental investigation. The steady-state as well as dynamic performance of APF is studied to compensate for current harmonics, reactive power, current unbalance and neutral current. The advantages and limitations offered by each of the topologies are also discussed in brief.

Design of Robust Digital PID Controller for H-Bridge Soft-Switching Boost Converter

Abstract: In this paper, a robust digital proportional-integral-derivative (PID) controller is proposed for the H-bridge soft-switching boost converter (HSBC). This digital PID controller is designed to ensure load voltage regulation as well as to give robust performance with step loads and source rejection. The mathematical models of the H-bridge boost converter are formulated, using the system identification tool, and then used in digital PID design. Here, this compensator is designed in the direct digital domain according to a pole placement approach that uses sensitivity function shaping in order to ensure closed-loop converter system stability as well as robust performance against converter parameter uncertainties. To confirm this, design simulations have been carried out on a 60-W 24-42-V HSBC. The experimental results are provided to validate the robust controller design concept.

An Efficient Control Strategy for a Five-Level Inverter Comprising Flying-Capacitor Asymmetric H-Bridge

Abstract: With regard to a five-level inverter comprising flying-capacitor asymmetric H-bridge, the impact on the capacitor voltage under conventional modulation approach is analyzed. Since it is sensitive to the fundamental period and the load current, it may introduce undesired low-order harmonics into the output voltage and may even break down the power switches due to the considerable fluctuation of the flying-capacitor voltage. Thus, this paper proposes a novel pulsewidth-modulation scheme with the positive and negative cross carriers, which controls the flying-capacitor voltage by utilizing the redundant switching states of the output voltages. Three modes of precharging the flying capacitor without extra equipments are presented. Moreover, the capacitance of the flying capacitor and the switching frequency of the power switches can be chosen according to the allowable fluctuation of the flying-capacitor voltage and the load current. In order to remove the overlapping of the level layers, the optimization of the line-to-line voltage waveform is proposed to synthesize the reference vector with the “nearest three-vector” approach. The theory is supported by the experimental results from the prototype.

A Seven-Level Inverter Topology for Induction Motor Drive Using Two-Level Inverters and Floating Capacitor Fed H-Bridges

Abstract: A multilevel inverter topology for seven-level space vector generation is proposed in this paper. In this topology, the seven-level structure is realized using two conventional two-level inverters and six capacitor-fed H-bridge cells. It needs only two isolated dc-voltage sources of voltage rating Vdc/2 where Vdc is the dc voltage magnitude required by the conventional neutral point clamped (NPC) seven-level topology. The proposed topology is capable of maintaining the H-bridge capacitor voltages at the required level of Vdc/6 under all operating conditions, covering the entire linear modulation and overmodulation regions, by making use of the switching state redundancies. In the event of any switch failure in H-bridges, this inverter can operate in three-level mode, a feature that enhances the reliability of the drive system. The two-level inverters, which operate at a higher voltage level of Vdc /2, switch less compared to the H-bridges, which operate at a lower voltage level of Vdc/6, resulting in switching loss reduction. The experimental verification of the proposed topology is carried out for the entire modulation range, under steady state as well as transient conditions.

Single-phase cascaded H-bridge multilevel inverter with nonactive power compensation for grid-connected photovoltaic generators

Abstract: This paper presents a single-phase cascaded H-bridge multilevel inverter for a grid-connected photovoltaic (PV) system with nonactive power compensation. A generalized nonactive power theory is applied to generate the nonactive current reference. Within the inverter's capability, nonactive power required by the local load is provided to improve the grid power quality. To minimize harmonics and achieve zero error tracking, a hybrid controller composed of a proportional controller and a repetitive controller is applied to current control. A single-phase 11-level cascaded multilevel inverter is considered in both simulation and experimental tests. Each H-bridge is connected to a 195 W solar panel. Simulation and experimental results are presented to validate the proposed ideas.

Modeling of switching frequency instabilities in buck-based DC–AC H-bridge inverters

Abstract: In this paper, the dynamical behavior of a full bridge DC–AC buck inverter controlled by fixed frequency and PWM is studied. After showing that the system can undergo both period-doubling and Neimark–Sacker bifurcation at the fast scale (switching period) by using the exact switching model, an exact solution discrete-time model able to predict both instability phenomena is derived. The model is obtained without making the quasi-static approximation and it can be used to obtain the useful operation region in the multi-dimensional design parameter space from time domain simulations in a very fast and accurate manner. Based on the study of the system, some design guidelines are provided. Copyright © 2010 John Wiley & Sons, Ltd.

Design and Analysis of Multistage Multiphase Switched-Capacitor Boost DC–AC Inverter

Abstract: A closed-loop multistage (n -stage) multiphase (p -phase) switched-capacitor boost dc-ac inverter (MPSCI) is proposed by combining a variable-phase control (VPC) and sinusoidal pulsewidth-modulation (SPWM) technique for low-power step-up inversion/regulation. Its power stage contains two parts: an MPSC booster (front) and an H-bridge (rear). An n-stage p-phase MPSC is for an inductor-less boost dc-dc conversion, where n voltage doublers are in series for boosting voltage gain up to 2n at most. For improving efficiency, VPC is suggested to realize a variable multiphase operation by changing phase number p and topological path for more suitable gain level. An H-bridge is employed for dc-ac conversion, where four switches are controlled by SPWM not only for full-wave operation, but also for enhancing output regulation as well as robustness to source/loading variation. The analysis and design include an MPSCI model, steady-state/dynamic analysis, conversion ratio, power efficiency, stability, capacitance selection, total harmonic distortion (THD), filter, and control design. Finally, the closed-loop MPSCI is simulated, and the hardware is implemented and tested. All results are illustrated to show the efficacy of the proposed scheme.

Analysis of cascaded H bridge multilevel inverters with photovoltaic arrays

Abstract: Now-a-days, photovoltaic (PV) power systems are getting more and more widespread with the increase in the energy demand and the concern for the environmental pollution around the world. Multilevel inverters (MLI) have gained much attention in the area of energy distribution and control due to its advantages in high power applications with low harmonics. Out of different structures of MLIs, Cascaded H Bridge (CHB) MLI is more suitable converter for PV applications since each PV panel can act as a separate DC source for each CHB module. The performance of symmetrical and asymmetrical single phase CHB multi level inverter with respect to harmonics content, number of switches and voltage stress across the switch with photovoltaic cell as its input source is simulated by using MATLAB/Simulink. A detailed harmonic analysis is done on the PV fed CHB-MLI by considering up to 23rd harmonics for 7 levels to 15 levels operation. Finally, the effect of change in irradiation and temperature on the performance parameters is also studied.

Cascaded H-bridge with bidirectional boost converters for energy storage

Abstract: This paper presents the design and control of a cascaded H-bridge converter for energy storage with bidirectional boost converter as charge/discharge unit The disadvantage of the second harmonic on the main energy storage unit as well as its voltage variation with the state of charge is solved by this structure The independent phase grid control is proposed for this topology This strategy is able to control the average dc-link voltage for each phase independently and to balance the cells capacitors voltages The balance of the energy storage units is achieved by controlling independently each cell charge/discharge current, together with the capacitors voltage control and balancing Converter cell loss distribution and total loss over a wide battery voltage variation is calculated for charge/discharge operation modes for a 416 kV grid coupling point and 5 MW rated power

H bridge cascade active electric filter DC side capacitance-voltage equalizing controlling method

Abstract: This invention relates to a method for uniformly controlling capacity and voltage at the DC side of a bridge-H cascade active power filter, which first of all takes a harmonic current, a reactive current needed to be compensated by a power net and a load as a compensation current desired by the active power filter, takes the sum of the desired compensation current and a fundamental wave positive sequence active current absorbed from the power net as a reference current of the active power filter to obtain a desired output voltage of the active power filter through a current tracking controller so as to output a current by the active power filter for tracking the reference current; calculates a micro-tune volume of the output voltage of the bridge-H cascade unit through a capacity and voltage balance controller based on a capacity and voltage deviation of the bridge-H cascade unit and the output current of the active power filter, carries out micro-micro adjustment to the desired output voltage to adjust a charge and discharge time of an unit flying capacitor; takes the micro-adjusted desired output voltage as the reference voltage of the unit, after a pulse width modulation to obtain a trigger signal of the output voltage of the bridge-H cascade power device and drive the power device.

Comparison of Cascaded H-Bridge, Neutral Point Clamped and Flying Capacitor multilevel inverters using multicarrier PWM

Abstract: Multilevel Inverters are becoming popular for their high voltage operating capability for high power applications. This paper presents a comparative study of Cascaded H-Bridge, Neutral Point Clamped and Flying Capacitor multilevel voltage source inverters. These five-level inverters are simulated in MATLAB/ Simulink using multi carrier sine pulse width modulation. FFT analyses of output voltages for an RL load is carried out. The advantages of Cascaded H-Bridge inverter over the other two types of inverters are brought out in this paper.

Nine level cascaded H-bridge multilevel DC-link inverter

Abstract: This paper presents the nine level cascaded H-bridge multilevel inverter based on a multilevel DC link (MLDCL) and a bridge inverter to reduce the number of switches. An MLDCL can be a diode-clamped phase leg, a flying-capacitor phase leg, or cascaded half-bridge cells with each cell having its own DC source. Compared to diode clamped & flying capacitor type MLDCL inverters cascaded H-bridge multilevel inverter requires least no of components to achieve same no of voltage levels. Optimized circuit layout is possible because each level have same structure and there is no extra clamping diodes or capacitors. Soft switching techniques can also be used to reduce switching losses and device stresses. The MLDCL provides a DC voltage with the shape of a staircase approximating the rectified shape of a commanded sinusoidal wave to the bridge inverter, which in turn alternates the polarity to produce an AC voltage. Compared with the existing type of cascaded H-bridge multilevel inverter, the MLDCL inverters can significantly reduce the switch count as well as the number of gate drivers as the number of voltage levels increases. For a given number of voltage levels, the required number of active switches is 2 (m−1) for the existing multilevel inverters, but it is m+3 for the MLDCL inverters. Simulation results are presented to verify the performance of the cascaded H-bridge MLDCL inverter supplying induction motor load.

Mono-dual frequency electromagnetic flowmeter excitation control system based on linear power supply

Abstract: The invention relates to a mono-dual frequency electromagnetic flowmeter excitation control system based on linear power supply, comprising a constant current source circuit, a current bypass circuit, an exciting coil driving circuit, an excitation time sequence generating circuit and a galvo circuit. A high voltage power supply is adopted for supplying power, the constant current source is constructed by linear power supply to supplying electricity for the exciting coil driving circuit, the current bypass circuit is jointed in parallel with the input/output end of the linear power supply to solve the problem of energy dissipation, the exciting coil driving circuit is composed of an H bridge and a control circuit thereof, the galvo circuit is bridge-jointed between the lower end of the H bridge and a reference ground, and a digital signal processor (DSP) is used for controlling multiple switches and an electrical level matching device to generate time sequence and control the action of the exciting coil driving circuit. The excitation control system can obviously improve excitation frequency range and excitation frequency preciseness, is suitable for single frequency high frequency square wave excitation or dual frequency square wave excitation, and can simultaneously provide more exact current detection to correct the flow signal processing result.

Fault recovery strategy for hybrid cascaded H-bridge multi-level inverters

Abstract: In the configuration of the multilevel inverter which is used in this study, two cascaded H-bridge cells are connected in series with each phase of a three-phase three-level neutralpoint clamped (NPC) inverter. The NPC inverter is fed by a single DC source; whereas, all of the cascaded H-bridge cells are supplied by capacitors. In this paper, in order to regulate the voltage across the H-bridge capacitors, a small fundamental harmonic is added to or subtracted from the original PWM reference of each H-bridge cell. In addition, the operation of the inverter during a fault in the cascaded H-bridge cells is studied and a method for recovery from fault and compensation of fault using the remaining H-bridge in the corresponding phase is proposed. This method allows acceptable operation of the inverter even when one of H-bridge cells is not functioning. Verification of the method using simulation shows the proper operation of the voltage capacitor regulation and strategy of fault recovery.

Reducing the output harmonics of cascaded H-bridge multilevel inverter for Electric Vehicle applications

Abstract: Both Hybrid Electric Vehicles (HEVs) and Electric Vehicles (EVs) need a traction motor and a power inverter to drive the vehicle motor. The requirements for the power inverter include high peak power, low output harmonics, inexpensive circuit and low continuous power rating. In this paper, reducing the output harmonics of cascade H-bridge multilevel inverter for electric vehicle applications is proposed. Switching angles of switch devices are determined by selective harmonic elimination technique. So, the effect of low order harmonics are reduced, as a result the efficiency of system has improved. Moreover, the number of DC voltage sources that used in the proposed inverter is less than conventional multilevel inverters that leads to reduce the inverter costs. A fundamental frequency switching methods has been used for modulation of inverter and to produce a seven-level phase voltages. Simulation results on various conditions were carried out using PSCAD/EMTDC software.

Direct Torque Control with 5-level cascaded H-bridge multilevel inverter for induction machines

Abstract: This paper presents a Direct Torque Control (DTC) utilizing a 5-level cascaded H-bridge multilevel inverter (CHMI) for induction machines. A multilevel hysteresis controller for flux and torque, with 12-sector stator flux angle detection and a precise look-up table for optimum vector selection is proposed to enhance DTC performances. A theoretical concept of the proposed DTC system in terms of flux and torque control and estimations and optimal voltage vector selection are studied in this work. The simulation results obtained from MATLAB/Simulink software showed that the proposed system significantly improved the DTC drive in terms of dynamic performance, smaller torque and flux ripple and lower THD.

H-bridge multilevel voltage source converter for direct grid connection of renewable energy systems

Abstract: The conventional approach based on low-voltage converter with power frequency transformer is commonly employed for grid connection of offshore renewable power generation systems. Because of the heavy weight and large size of the transformer, the system can be expensive and complex for installation and maintenance. As an alternative approach to achieve a compact and light direct grid connection, a high-voltage converter using series connected H-bridge (SCHB) multilevel converter topology is proposed in this paper. Since the SCHB converter requires a large number of isolated and balanced DC supplies, a high frequency transformer link is employed to couple the SCHB to the single low voltage DC supply. This paper presents the design and simulation of the proposed system.

Model predictive-based control method for cascaded H-Bridge multilevel active rectifiers

Abstract: The cascaded H-Bridge multilevel active rectifier is an emerging converter topology, which offers significant advantages, such as modularity and high flexibility for a wide range of applications, including traction systems, industrial automation plants, uninterruptable power supplies, and battery chargers. However, the need for stable operation of the H-Bridge cells at asymmetrical voltage potentials and unbalanced loads imposes demanding requirements, in terms of an advanced and accurate control strategy. This paper introduces a simple and powerful solution to the mentioned problems, based on constrained Model Predictive Control (MPC). The proposed nonlinear controller achieves low input current harmonic distortion with almost unity power factor, as well as independent regulation of the H-Bridge cells, both under steady state and transient conditions. The effectiveness of the novel control algorithm is demonstrated by means of simulations as well as preliminary experimentation on a single-phase laboratory setup.

United electric energy quality controller based on series multiplex of transformer and chain type construction

Abstract: The invention relates to a unified power energy quality controller based on the serial-connection multiplicity of transformers and a chain structure, which belongs to the technical filed of flexible AC transmission and distribution of an electric power system and the power electronic. The unified power quality controller comprises a single-phase serial-connection multiple transformer bank and a single-phase chain H bridge converter, wherein the transformer bank consists of m single-phase transformers which form the serial-connection multiple transformer bank together with n voltage source converters connected with n secondary windings of m single-phase transformers respectively; the single-phase chain H bridge converter is provided with n chains and is formed by connecting n DC voltage supporting units and n power source converters, and an AC port of the n-chain single-phase chain H bridge converter is directly connected with the electric fence through a reactor, m and n are signless integrals equal to or more than 2, and m is less than or equal to n. The invention can realize accurate current control, has high dynamic responding speed, and can solve the problems of the traction substation of an electrified railway that the three-phase voltage is unstable and fluctuates, the power factor is low and the harmonic pollution exists, and the like.

The comparative analysis of multicarrier control techniques for SPWM controlled cascaded H-bridge multilevel inverter

Abstract: This paper presents a cascaded H-bridge multilevel inverter that can be implemented using symmetrical topology. A multilevel inverter is a power electronic device built to synthesize a desired AC voltage from several levels of DC voltages. Multi level inverters have been an important development in recent years. Owning the capability to increase the power quality delivered to the load for high performance applications. the power quality improvement achieved by reducing the harmonics presented at the output voltage of the inverter. The Total Harmonics Distortion (THD) presented at the output phase voltage of the inverter measured and compared. Here, the comparative analysis of several carrier control techniques used for harmonic mitigation is done.

Harmonic analysis of a modified cascaded multilevel inverter

Abstract: In Multilevel Inverters, Cascaded H bridge converters are considered to be the most preferred form of converters. But in these converters as the number of staircase levels in output voltage increases the dc source requirement also increases, thereby limiting its application. This paper tries to address the above mentioned problem by developing a Modified version of Cascaded Multilevel Converters which require reduced number of dc voltage source for increased levels in output voltage as compared to conventional cascaded converters. The spectral quality analysis of output voltage obtained for different loads is also shown signifying the merits of modified converters. Due to these advantages the drawback in the implementation of conventional cascaded converters in electric vehicles or in industrial applications is overcome by modified cascaded inverters. In this paper, the developed Modified Cascaded Converters are simulated in MATLAB/ SIMULINK and the THD of different output voltage levels are compared for different loads.

Novel H-bridge multi-level inverter with DC-link switches

Abstract: This paper proposed a new multi-level inverter topology based on a H-bridge with two switches and two diodes connected to the DC-link. The output voltage of the proposed topology is quite closer to a sinusoidal waveform compared with a typical single phase inverter. The proposed multi-level inverter is applicable to a power conditioning system for renewable energy sources, and it can be also used as a building block of a cascaded multi-level inverter for a high voltage application. In case of conventional H-bridge type or NPC type multi-level inverter, 8 controllable switches are used to obtain a 5 level output voltage, but the proposed multi-level inverter requires only 6 controllable switches. Thus the circuit configuration is quite simple, reliable and cost-effective implementation is possible. The efficiency can be improved owing to the reduction of the switching loss. A new PWM method based on POD modulation is suggested which requires only one carrier signal. The switching sequence to make the capacitor voltage balanced is also considered. The feasibility is studied through simulation and experiment.