Dual-buck Full-bridge Inverter Research Articles

The DC-side active filter with dual-buck full-bridge inverter for wind generators

The DC-side active filter with dual-buck full-bridge inverter for wind generators

Control por histéresis para un inversor buck-dual conectado a la red

Single-phase inverters are widely used in different renewable energy applications. Although the full-bridge inverter istypically used, dual-buck inverters provide an important advantage, since they eliminate the shoot-through problems. However, solutions proposed in the literature require additional inductors, use linear controllersdesigned around an operation point, or cannot be used in grid-connected applications. This paper presents a hysteresis current control of a single-phase dual-buck full-bridge inverter for grid-connected active power injection. Includes the dynamical modelin state variables, as well as analytical conditions to guarantee the evolution of the error dynamics in a set with boundaries defined by the designer. Moreover, the paper provides guidelines for the design of the dead band required for the transitions between the positive and negative semi-cycles (and vice-versa) of the grid voltage. Finally, simulation results validate the main features of the controller as well as the design of the dead band

Dual-Buck Full-Bridge Converter With Soft-Switching Characteristics for High-Precision Applications

The output distortion of conventional full-bridge inverter is present due to the required switch blanking time. Dual-buck full-bridge inverter (DBFBI) does not experience blanking time problems but requires a bias current to make the inductors operate in continuous conduction mode (CCM) for better output waveform with interleaved switching. The existence of bias current will cause dc-biased magnetization of the inductors and make them easy to saturate. To overcome this problem, the volume of inductors must be sufficiently large to ensure that there is no saturation in CCM of inductors’ operation. This article proposes extra snubber cells to realize soft-switching operation of the converter. The extra snubber cell DBFBI (ESCDBFBI) topology has the advantages of high-precision current output and much lower total inductor volume. The basic operation and properties of the ESCDBFBI topology are explained. Finally, an 800-W prototype of the proposed inverter is built and the experimental results agree with the theoretical analysis.

Switching and Conduction Loss Reduction of Dual-Buck Full-Bridge Inverter Through ZVT Soft-Switching Under Full-Cycle Modulation

Based on the no blanking time characteristic, voltage error does not occur in the pulsewidth modulated output stage of dual-buck full-bridge inverter (DBFBI), resulting in lower total harmonic distortion (THD) of the output current. The two main modulations applied in the topology are half-cycle modulation and full-cycle modulation. Compared with the half-cycle modulation, the full-cycle modulation does not have the zero-crossing problem, but the inverter requires a bias current to guarantee better output waveform. The circulation current loop caused by bias current has a great influence on inverter efficiency. This article proposes a novel zero voltage transition (ZVT) soft-switching topology to increase efficiency by reducing the switching losses and conduction losses resulting from low bias current. The advantages of the DBFBI are included in the proposed inverter. The soft-switching condition is achieved by the snubber cells, and the energy stored in the passive snubber capacitors can be transferred effectively. The topology deduction, operating principles, and design guidelines are presented in detail. An 800-W experimental prototype operating with a 100-kHz switching frequency is implemented to verify the theoretical result.

Research on transformerless dual‐buck full‐bridge grid‐connected inverter with H5‐type for PV systems

To eliminate the common-mode leakage current in the transformerless grid-connected photovoltaic (PV) system, inspired by the newly-developed embedded-switch H5 topology and dual-buck full-bridge grid-connected inverter (GCI), a novel transformerless dual-buck full-bridge GCI with H5-type (TDFGI-H5) topology for PV systems is firstly presented. Then, the operating modes and common-mode leakage current of TDFGI-H5 modulated by unipolar sinusoidal pulse-width modulation are analysed. The analysis result shows that TDFGI-H5 has the advantages of the three-level output, no shoot-through problem, high reliability, and can completely meet the condition of eliminating common-mode leakage current. Aim at the problem of the common-mode leakage affected by the switches' junction capacitances, the effect of switch's junction capacitance is explored in detail when TDFGI-H5 is in the transient process that converts from non-decoupling states to decoupling states. Finally, the results of experiment verify the correctness of the theoretical analysis.

Real Time Harmonic Mitigation Using Fuzzy Based Highly Reliable Three Dual-Buck Full-Bridge APF for Dynamic Unbalanced Load

Abstract This study presents a highly reliable 3-phase 4-wire, three dual-buck full-bridge shunt active power filter (3 DB FB APF) for distribution system. The proposed topology uses three single phase dual buck full bridge inverter sharing the same dc-link capacitor with high utilization of dc-bus voltage. The dual buck inverter circuit composed of one power switch and one diode leg instead of two power switches conventional inverter leg effectually eliminate the undesirable “shoot-through” phenomenon occurs in conventional inverter circuit. The fuzzy and adaptive hysteresis current controller based id-iq control strategy has been adopted to generate optimized switching frequency. For validation, the proposed topology is implemented in the OPAL-RT LAB using OP5142-Spartan 3 FPGA. The dynamic performance of the proposed 3 DB FB APF is assessed for sinusoidal, unbalanced and non-sinusoidal voltage source condition with unbalanced non-linear load that is when both three-phase and single-phase loads are present in the system. Besides, the results with proportional-integral (PI) controller are compared with FLC in terms of harmonic compensation. Furthermore, a comparison has been made between split capacitor dual buck half bridge active power filter (2C DB HB APF) and proposed 3 DB FB APF based on switch power rating.

Dual‐buck full‐bridge grid‐connected inverter with common‐mode leakage current elimination

The dual-buck full-bridge grid-connected inverter (DFGI) is well known as its no shoot-through problem, high efficiency and high reliability, but the common-mode leakage current exists in the positive half cycle. To solve the problems of common-mode leakage current of the conventional DFGI, a new DFGI topology is proposed. The corresponding modulation strategy is presented. Meanwhile, on the basis of the theoretical analysis, it can eliminate the common-mode leakage current of conventional DFGI. The experimental results prove the validity of the theoretical analysis.

High Frequency Dual-Buck Full-Bridge Inverter Utilizing a Dual-Core MCU and Parallel Algorithm for Renewable Energy Applications

A high frequency dual-buck full-bridge inverter for small power renewable energy applications is proposed in this paper. The implementation of the wide band gap SiC (Silicon Carbide) power device contributes to the high switching frequency of 400 kHz. This high frequency contributes to reduced converter volume as well as improved power density, which greatly strengthens its portability and application range. For the control strategy, a voltage-current dual loop controller is employed. A three-pole-three-zero (3P3Z) compensator is applied in the current loop in order to track the current reference without static error. A voltage loop two-pole two-zero (2P2Z) compensator is used to generate the current reference for stabilizing the DC bus voltage. Not only is the inner current loop analyzed in detail, which includes the modeling of the equivalent inductor-capacitor-inductor (LCL)-type inverter and the design of the 3P3Z compensator, but also the outer voltage loop is discussed, the model of which is established based on the energy balance. Furthermore, a feedback linearization method is adopted to simplify the duty cycle calculation and helps to accelerate the control speed. A second-order generalized integrator software phase lock loop (SOGI-SPLL) is employed to obtain the phase angle and to synchronize the inverter output current with the grid voltage. A parallel structure algorithm is conducted based on a dual-core microcontroller unit (MCU) for the first time to control the high frequency inverter. This approach avoids the contradiction between the high frequency operation and the limited computing capacity of the conventional single-core MCUs. The software structure, time-consuming distribution, and interactive communication method are analyzed in detailed. Finally, this paper verifies the feasibility of the theoretical analyses through simulation and experiments based on a 1 kW prototype.

Analysis of Power Loss and Improved Simulation Method of a High Frequency Dual-Buck Full-Bridge Inverter

A high frequency dual-buck full-bridge inverter for small power renewable energy application is proposed in this paper. A switching frequency of 400 kHz is achieved with the adoption of the SiC power device. A two-pole two-zero (2P2Z) compensator is employed in the outer voltage loop to generate the current reference for inner current loop. A 3P3Z compensator is adopted in the inner current loop to track the current reference. A systematic way for calculating the losses of high frequency inverter is presented, and the losses of the components are thoroughly analyzed. The turn-on and turn-off procedures of the inverter are discussed in detail. The losses caused by high frequency are calculated accurately, and the loss distribution is established as well. The procedure of the loss analysis gives a practical example for calculating the loss of similar type inverters. Moreover, deviation between pulse width modulation (PWM) control signal and switching response in high frequency switching is thoroughly analyzed. The influence of deviation is verified by designed experiment. Hence, a compensation method is proposed in order to minimize the influence. The compensation effect is validated by experiment and simulation. Finally, a 1-kW prototype is built to verify the feasibility of the theoretical analyses. The grid-connected maximum output power experiment is completed at 1 kW with the efficiency of 96.1% and the total harmonic distortion (THD) of 1.8%. The comparison experiments of power loss between Si and SiC power devices are carried out. The experiment results confirm the loss calculation method to be valid.

Interleaved Dual Buck Full-Bridge Three-Level Inverter

A novel interleaved dual buck full-bridge three-level inverter (IDBFTI) is proposed for the grid-connected system in this paper. It retains the advantages of interleaved parallel technology for inverter as follows: reducing the output ripple current and the total harmonic distortion of the output current, increasing the power density of system, and reducing the current stress and thermal stress of power devices. Besides, it can solve the problem of zero sequence circulation current (ZSCC) in interleaved inverter system by the circuit structure, and it also has the advantages of no shoot-through problem, no reverse recovery of the body diode, and three-level output. The interleaved inverter circuits share two power-frequency switches, which are resized for each specific application, and it is easier to extend the system by improving current capability of the two switches. The working principle of this system is introduced in detail, and a 2-kW experimental prototype has been established and tested. Test results verify the principle and the excellent performance of IDBFTI.

Single Inductor Dual Buck Full-Bridge Inverter

A new single inductor dual buck full-bridge inverter is proposed in this paper. The inverter is improved on the basis of a dual buck inverter, and it retains the advantage of a no reverse recovery of body diode. The dc voltage utilization rate can be increased by adopting the voltage commutation bridge instead of the voltage-dividing capacitors in the inverter. In addition, comparing with other dual buck inverters, the inverter has just one filter inductor, which can make the volume and weight of the system decreased observably and improve the integration. The controlling method, combining the high- and low-frequency modulation, is adopted to weaken the complexity of control and improve the reliability and stability of the system. The operating principle, characteristic analysis, simulation and experiment are provided in this paper. A 1-kW prototype is established and tested, and the results of simulation and experiment verify the correctness of the theoretical analysis.

Study on nonlinear phenomena in dual buck full-bridge inverter

Dual buck full-bridge inverter has the following advantages: it has no shoot-through problem, but receives high-utilization of DC input voltage, high efficiency and optimum selection of the freewheeling diodes, hence it attracts more and more attention in high power applications. In this paper, the bifurcation and chaos in the dual buck full-bridge inverter is studied. The two-dimensional discrete iterated mapping model under proportional control is established and stroboscopic maps in different periods of time are obtained. Effects of the proportional coefficient k on system performance are analyzed by using bifurcation diagram and folded diagram. A simulation model of dual buck full-bridge inverter is established based on Matlab/Simulink and the time domain waveforms and phase-space portraits for different proportional coefficient k are obtained. Besides, the effects of the bifurcation and chaos on the spectrum of the system are analyzed. Finally, the nonlinear behavior in the inverter caused by the variation of other circuit parameters such as input voltage E, inductance L, and the switching period of carrier wave T is discussed through bifurcation diagrams. Results show that the correct choice of circuit parameters of dual buck full-bridge inverter is very important for its stable operation.

Control of Single-Phase Grid-Connected Inverters With Nonlinear Loads

This paper presents a control of single-phase grid-interactive inverters with nonlinear loads. The utility-connected inverter should operate at both stand-alone and grid-connected modes. However, the waveform qualities of the grid current in grid-connected mode and the output voltage in stand-alone mode are poor under the nonlinear critical load with the conventional control. The impact of the nonlinear load on the grid current is analyzed. The proposed control is illustrated in detail. By adding the load current into the filter inductor current loop, the influence of the nonlinear load on the grid current can be eliminated, and the waveform quality of the output voltage in stand-alone mode can be improved. The control method is simple and easy to be achieved. The grid-connected inverter is stable at both modes. The filter inductor is chosen. Simulation and experimental results from a 1-kW dual-buck full-bridge grid-interactive inverter with a diode rectifier load verify the theoretical analysis.

Dual-Buck Full-Bridge Inverter With Hysteresis Current Control

This paper presents a dual-buck full-bridge inverter (DBFBI) to solve the shoot-through problem in conventional bridge-type inverters and reduce the voltage stress of the power device in the dual-buck half-bridge inverter (DBHBI). Hysteresis current control is used in the DBFBI. All switches and diodes operate at each half line cycle, and the freewheeling current flows through the independent freewheeling diodes instead of the body diodes of the switches, so the efficiency can be increased potentially. As the shoot-through problem does not exist in the DBFBI, dead time between the switches need not be set. The input-voltage utilization rate of the DBFBI is twice that of the DBHBI under the same output-voltage condition, i.e., the voltage stress of the power device in DBFBI is half that in the DBHBI. The operating principle, stability and relative stability analyses, and design guidelines and example are provided. Experimental results of a 1-kVA DBFBI verify the theoretical analysis. The comparisons among other inverters and the DBFBI show that the proposed inverter is very promising in 220-240-V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> output-voltage and high-reliability applications, such as uninterruptible power supplies and grid-connected inverters.