AC Output Research Articles

All‐SiC 99.4%‐efficient three‐phase T‐type inverter with DC‐side common‐mode filter

AbstractThis letter presents a hardware demonstrator of an all‐SiC three‐level T‐type (3LTT) inverter with the common‐mode (CM) EMI filter stages placed on the DC input instead of the AC output side, targeting, for example, high‐efficiency PV applications. The extensive experimental characterization shows that state‐of‐the‐art SiC transistors and a DC‐side CM filter enable an unprecedented peak/full‐load efficiency of 99.4% (calorimetric measurement) at 12.5 kW and a power density of 2.4 kW/dm3(39 W/in3). The demonstrator fulfills CISPR 11 Class A EMI regulations as well as upcoming EMI standards for the frequency range of 9–150 kHz. Compared to other high‐efficiency converters, which often employ bridge legs with more output voltage levels, the described 3LTT concept thus offers a very favorable trade‐off between complexity and performance.

Fuzzy logic control based maximum power point tracking technique in standalone photovoltaic system

This study describes the development of a smart technique for tracking the highest power point on a standalone photovoltaic (SAPV) system when temperature and irradiance conditions are changing using fuzzy logic control (FLC). The PV systems comprises of a PV array, a boost converter, a controller for tracking the maximum power point, and an inverter to power the AC loads. The FLC-based maximum power point tracking (MPPT) is proposed because the technique is not complex and does not need a deep comprehension of the particular model of the system. Furthermore, the technique is efficient and fast response in tracking maximum power (MP) from the PV array. The technique overcame the limitation of the conventional MPPT technique that resulted in slow tracking of the MP and was not accurate on the optimal position of the PV array output power. The SAPV system is integrated with the sealed lead acid (SLA) battery bank as an alternative power source and makes up for power shortages by supplying energy to the load without interruption during power shortages. A system for managing the battery has been included in the system to preserve the battery's longevity by controlling the battery's charging process. The PV system is able to supply single-phase output AC voltage of 230 Vrms and has low total harmonic distortion (THD) that is suitable for home appliances. The achieved simulation results demonstrate the effectiveness of the suggested fuzzy logic controller in tracking the MPP.

Single-Stage Isolated DC/AC Converter With Continuous Dynamic Model and Controller Design

This article proposes an analysis and controller design of a bidirectional bridgeless single-stage DC/AC converter with high frequency-link and low part count. Dual phase-shift control is proposed to control and modulate the AC power and to minimize the Root Mean Square (RMS) of the transformer current. Furthermore, the phase shift angle is chosen to assure wide range of ZVS turn-on of all the switching devices. The proposed controller has a reduced THD at the output AC current without zero-crossing spikes. A continuous-time average model, that well predicts both transient and steady-state relations between the high-frequency AC link and the DC side, is needed to simplify the controller design. Since complex discrete-time models were used in previous literatures, simple and powerful continuous-time tools were not used to design the closed-loop system. In this paper, a novel continuous-time Generalized Average Model (GAM) is proposed. The derived model precisely predicts the high-frequency state variables of the converter, including a simple formula for the transformer current RMS value. The formula is used to minimize the transformer current to reduce the losses. Moreover, the transient analysis and the closed-loop control design are presented. A prototype circuit is tested to verify the performance of the proposed control scheme with the proposed isolated single-stage DC/AC converter.

Build a DC to AC Inverter Circuit with IOT Based Load Monitoring

Abstract: The boost inverter or boost DC-AC converter is a new voltage source inverter (VSI) that is suggested in this research. The novel inverter topology's key feature is that, depending on the instantaneous duty cycle, it produces an AC output voltage that is greater than the DC input voltage. This characteristic is not present in the conventional VSI, which consistently generates an AC output instantaneous voltage lower than the DC input voltage. A sliding mode controller is suggested to optimize the boost inverter dynamics while guaranteeing proper functioning under any working circumstance. The primary benefit of sliding mode control over traditional control strategies is its resistance to changes in plant parameters, which results in invariant dynamics and steady-state response in in the best scenario. This study covers operation, analysis, control technique, and experimental outcomes. When an AC voltage greater than the DC link voltage is required, the new inverter is designed to be employed in UPS and AC driver systems without the requirement for a second power conversion stage

Analysis of Transformer Using Flyback Converter Circuit

This paper discusses two types of transformers 3 A and 5 A with the addition of a flyback converter circuit. The transformer 3 A is only able to lower the DC output voltage and cannot produce an AC output voltage. So that the addition of a flyback converter circuit is proposed to change the AC output voltage and increase the voltage based on the desired load. The results of the 3 A transformer test obtained an increased output voltage from 12.21 Vdc to 18.04 Vdc with a constant time period of 1 minute. While testing the 5 A transformer shows that the increase in output voltage is obtained by adding a flyback converter circuit. The result of the output voltage with the addition of a flyback converter circuit reaches 221 Vac to 252.2 Vac. The increase in output voltage is directly proportional to a constant time period of one minute.

Submodule Capacitor Voltage Ripple Reduction of Full-Bridge Submodule-Based MMC (FBSM-MMC) with Non-Sinusoidal Voltage Injection

The full-bridge submodule (FBSM)-based modular multilevel converter (FBSM-MMC) offers promising performance due to its ability to output negative FBSM voltage. This paper studies this ability of the FBSM-MMC under zero-sequence voltage injection (ZSVI) and second-order harmonic current injection (SHCI). The focus of the research is to redistribute the FBSM powers by injecting an additional power degree of freedom, resulting in a smaller FBSM capacitor voltage ripple, while keeping the maximum AC output voltage for a given fundamental frequency component of the arm voltage reference. Accordingly, a control strategy was developed, based on non-sinusoidal ZSVI, and SHCI is proposed for further improving the performance of the FBSM-MMC. The proposed non-sinusoidal ZSVI contains a higher sinusoidal third-order harmonic component than that of pure sinusoidal third-order voltage injection (THVI) when operating under the same maximum AC output voltage. By implementing this solution, a smaller amplitude of the injected second-order harmonic current can be achieved, producing a lower power loss in the FBSM-MMC. Considering the proposed solution, the relationship of the arm powers and FBSM capacitor voltages are also discussed. Finally, the simulation results and experimental results are presented to verify the effectiveness of the theoretical analysis of the proposed method.

Space Vector Modulation technique implementation for the control of a Three-Phase Matrix Converter

The Three-Phase Matrix Converter (3ph-MC) is a direct AC-AC converter that employs controlled semiconductor switches to enable a direct connection between the three-phase source and load. This setup enables an unlimited output frequency, thanks to the use of semiconductor switches with controlled turn-off capability. However, the 3ph-MC suffers from the simultaneous commutation of bidirectional switches, which has limited its popularity. Fortunately, several control techniques have been developed to overcome this issue and ensure safe switch operation. Among these strategies, Roy, Venturi, and the Space Vector Modulation (SVM) Techniques are the moste widely used. In this context, the present paper investigates the implementation under Matlab / Simulink of a 3ph-MC using SVM. Unlike conventional PWM converters, the 3ph-MC does not cause switching common mode voltage across the load system terminals, which can lead to common mode current and bearing failure in load drive. The use of SVM can rectify these issues and minimize the effect of harmonic fluctuation in AC output voltage. The paper includes simulation results to validate the proposed system.

Enhanced performance of hysteresis controlled single phase Ac/Dc buck converter system using cubic boron arsenide semiconductor material

This paper presents a single phase AC-DC buck converter using Hysteresis controller in order to provide superior response. As an alternative to the DC grid, the single phase AC/DC buck converter is getting prominence. The rectifier's AC output is fed into a Buck converter (BC) and then filtered with a filter. Higher order harmonic components are present in the power drawn by nonlinearandunbalancedloads,whichinturn raises the supply current’s totalharmonicdistortionlevel. In comparison to other controllers, hysteresis current controllers are well known for their robustness, faster error tracking, greater dynamic response and simplicity of implementation. In this study, a single phase buck converter system with a Proportional Integral controller (PIC) and a Hysteresis controller is modelled and simulated (HC). The findings of comparing the performance of buck converters with PIC and HC are presented. The outcomes show that an HC controlled Buck Converter responds more quickly. Because of improvements in material science and a desire for higher performance, wide band-gap semiconductors are used in switching circuits. This paper also discusses the cubic boron arsenide semiconductor material, which is used to create the power electronic switches used in AC-DC converters and has good thermal conductivity and high manoeuvrability for electrons and holes.

Topology and Space Vector Modulation Method for the Reduced Switch Count Quasi-Z-Source Three-Level Inverter

This paper proposes the topology and space vector modulation (SVM) method of a reduced switch count (RSC) quasi-Z-source (QZS) three-level inverter, which can realize voltage buck-boost operation by adopting ten power switches. Compared with the QZS three-level T-type inverter, the presented inverter can further reduce the number of power switches. The SVM method for the proposed topology is designed, which introduces a distribution factor to balance the neutral-point voltage (NPV) actively. In addition, the up-shoot-through (UST) and down-shoot-through (DST) states are inserted within the durations of redundant small vectors to boost the dc input voltage, while the normal ac output voltage is not affected. Detailed comparisons of the RSC QZS three-level inverter and the existing impedance-source-based three-level inverters are conducted, and design guidelines and recommendations for selecting different components are given as well. Simulated tests based on MATLAB software and experimental tests based on a hardware-based test rig are conducted to validate the operating performance of the proposed topology and modulation method, which reveal that single-stage power conversion is achieved. Moreover, the NPV balance is actively controlled by using the proposed method.

A Novel High-Efficiency Three-Phase Multilevel PV Inverter With Reduced DC-Link Capacitance

We present a novel three-phase multilevel inverter (MLI) design for PV applications that does not require large DC-link capacitors to buffer the 120 Hz power ripple and allows individual inverter module to process trapezoidal power instead of sinusoidal power. This new design features two inverters connected in parallel to each DC source and N inverters connected in series to each grid phase to support the grid voltage. The trapezoidal operation improves the overall system&#x2019;s efficiency by allowing the inverter module to output peak or zero power for most of the AC cycle. We present the controller design and simulate the proposed MLI system in PLECS. We demonstrate an experimental 110<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> DC input, 208 <inline-formula><tex-math notation="LaTeX">$V_{rms}$</tex-math></inline-formula> three-phase AC output, 1kW 5-level prototype with <inline-formula><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula>&#x00A0;95&#x0025; efficiency. With the same inverter module, we compare the efficiency of the proposed design to the conventional MLI design, where all modules share phase power evenly. We demonstrate that the proposed design consistently outperforms the conventional design in efficiency, with <inline-formula><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula>&#x00A0;20&#x0025; loss reduction at light load conditions.

A single‐source switched‐capacitor based 13‐level sextuple boost inverter with reduced component count and low THD

AbstractA switched‐capacitor‐based 13‐level inverter with a lesser number of components is presented in this article. The 13‐level single‐phase AC output voltage is achieved with a voltage gain of 6 by including a single DC source, 11 switches, 4 capacitors, and 3 diodes in the proposed converter. The self‐voltage balancing is achieved for various types of load without the need for complex control schemes and auxiliary circuits. The proposed topology does not require a back‐end H‐bridge to generate negative polarity. This leads to a reduction in voltage stresses across the switches. Thus, total standing voltage (TSV) and the overall cost of the proposed topology are reduced as compared to the state‐of‐the‐art topologies reported in the literature. Furthermore, an Improved Nearest Level Modulation (INLM) scheme is used to improve the power quality of the output voltage. Using the proposed scheme, the Total Harmonic Distortion (THD) of the output voltage is reduced to 5.08%. The power loss analysis for various elements of the proposed converter is also included. A comparison with recent topologies in reference to various performance parameters is carried out. In addition to the simulation study, a laboratory prototype is prepared to validate the efficacy of the proposed converter.

Comparison between a Cascaded H-Bridge and a Conventional H-Bridge for a 5-kW Grid-Tied Solar Inverter

This paper compares the cost and efficiency of two inverter topologies for a 5-kW grid-connected solar inverter application: the Conventional H-Bridge Inverter (CHB) and the Cascaded H-Bridge Multilevel Inverter (CHBMLI). Emphasis is put on power switches and passive elements with a detailed study of the losses. Both designs respect the same constraints (cost, efficiency, and junction temperature of the transistors) to ensure a fair comparison between both topologies. The work highlights the important parameters when choosing the components (MOSFETs, capacitors, and magnetic cores for the inductors). The DC-link voltage ripple and the output AC current ripple are the key parameters for the design of the passive elements (capacitors and inductors). On top of that, the transistors MOSFETs are chosen, in both topologies, to limit the conduction losses (by selecting the Rdson) and the switching losses (by selecting the Qrr and dv/dt). Real components are picked in order to make the comparison as complete as possible. Numerical simulations are performed using the MATLAB platform. All equations and parameters are provided. A CHBMLI prototype was built with eight independent H-Bridges to validate the proposed design with thermal and efficiency measurements.

Over &amp; Under Voltage &amp; Short Circuit Protection of Electrical Appliance

Abstract-The aim of this project sudden fluctuation in supply is a very big problem in industries and domestic applications. It causes a major loss for industries, offices and homes. This project gives a low cost and powerful solution for this problem. This Circuit protects refrigerators ACs, Microwave ovens as well as other appliances from over and under voltage fluctuations. Operational amplifier IC LM324 is used here as a comparator. The preset is adjusted such that for the normal supply of 180V to 240V, the voltage at non-inverting terminal of op-amp is less than 6.8V. The same unregulated supply is given to the second comparator through a 5.6V zener diode. 12V SPDT relay is used to control the Load. An NPN transistor is used to drive the relay. This project uses regulated 12V, 500mA power supply. 7812 three terminal voltage regulator is used for supply voltages and reference voltages for LM324 comparator circuit. Bridge type full wave rectifier is used to rectify the ac output of secondary of 230/12V step down transformer. Index Terms- short circuit protection, saving energy, home appliance protection.

Designing a Multi-Output Power Supply for Multi-Electrode Arc Welding

Multi-output power converters using different architectures can have significant efficiency advantages. This paper proposes a multi-output welding power supply that is based on the middle DC converter distributed architecture. This machine includes two converter groups, and each group comprises a three-phase rectifier unit, a full-bridge converter unit, a HF (high frequency) transformer, a rectifier unit, and a chopper converter unit. Among these units, the three-phase rectifier unit, full-bridge converter unit, HF transformer, and rectifier unit convert three-phase AC voltage into a low voltage, and the chopper converter unit converts the low voltage into the required current. The welding power supply can output four DC and two AC currents. This paper also analyzes the stability of the welding power supply. Finally, a prototype is designed and verified through experiments, and the maximum output of the prototype is 300 A. The experimental results show that the converter can output different DC and AC currents according to the requirement, the multiple outputs are independent of the others, and the output phase and value are independently adjustable. After verification, the proposed multi-output welding power supply can output steady current according to the requirement.

Transmission of Digital Data to Cascaded H-Bridge Converters Through the Power Line

Power line communication (PLC) technologies enable the point-to-point linking between distributed power production and consumption units, thus overlaying enhanced monitoring and control capabilities to the overall power system. A novel PLC method for cascaded H-bridge converters is presented in this article, which enables the transmission of digital data by a remote terminal computer to the individual power modules synthesizing a cascaded H-bridge power converter through their power circuits. The proposed PLC method comprises an integrated framework of a digital data transmitter, receiver, and communication protocol, without using additional coupling circuits, which is suitable for cascaded H-bridge power converters with either a dc or an ac output. Its operation was tested using an experimental prototype consisting of a two-module cascaded H-bridge inverter and a field-programmable gate array device hosting the digital transmitter and receiver units. The experimental results verified the successful transmission of digital parameterization commands from a central terminal computer to the individual power modules of the cascaded H-bridge converter, along with the simultaneous transmission of ac or dc power to the load over the common power cable.

태양광 발전 시스템의 인버터 단락사고 발생 대응을 위한 레그 절체 방안의 적용 및 검증

In this paper, we propose a countermeasure technique by leg transfer switch in case of an inverter short-circuit fault for application to a PV generation system. In general, inverters operating in a 3-leg manner are used to obtain output AC power from input DC voltage. However, if a short-circuit fault occurs in an inverter operating in a 3-leg method, a problem occurs in power supply. As a countermeasure against this, we propose a leg transfer switch method that changes the 3-leg method to a 2-leg method without replacing the power semiconductor. If the leg transfer switch method is used, power can be supplied normally by switching the legs of the inverter. In addition, it was verified through simulation to verify the leg transfer switch method. As a result, when a short-circuit fault occurred in the inverter operating in the 3-leg mode, it was possible to transfer power normally by converting to the 2-leg method using the leg transfer switch method.

A performance assessment of nine-stage ternary DC source mli through various PWM topologies

ABSTRACT In modern days, MLIs comprise a lot of concentrations in academia and industry. As they are altering interest in a feasible technology in supporting frequent applications of renewable energy conversion systems and drives, these huge power and medium/higher voltage applications and MLIs are extensively used as one of the sophisticated powers converter topography. The MLIs are divided into two types such as asymmetric and symmetric. MLIs of the asymmetric kind have more amount of output AC voltage stage with fewer DC input source voltage and switching components. In this research paper, asymmetric single-phase cascade full-bridge MLI is developed with carrier-based unipolar PWM techniques. This MLI can generate nine-stage of output AC voltage through eight switches and two input DC sources. It is tested through a variety of multicarrier unipolar PWM control combinations. The Phase Disposition (PD), Alternating Phase Opposition Disposition (APOD), Carrier Overlapping (COP) and Variable Frequency (VF) are all PWM control which included in support of preference of single-phase nine-stage ternary cascade multilevel inverters. With various modulation indices (ma), the harmonic substance of output AC voltage for each approach is observed and tabulated. The proposed design for generating nine-stage output AC voltage is demonstrated using MATLAB-SIMULINK and confirmed using a laboratory-based prototype model. The results show that the unipolar Alternating Phase Opposition Disposition PWM technique that provides a high-quality output voltage with less harmonic distortion. Besides, the performance of Carrier Overlapping PWM techniques is greater since it produces a superior fundamental RMS output AC voltage.

Decoupled Control for Double-T Dc-Dc MMC Topology for MT-HVdc/MVdc Grids

This paper proposes a decoupled control of a dc-dc modular multilevel converter (MMC) based on a double-T topology intended for multi-terminal high voltage direct current (MT-HVdc) transmission systems or emerging distribution systems operating in medium voltage direct current (MVdc). The aim of the proposed control strategy is to obtain an input current with reduced harmonic content and to eliminate the output ac common-mode voltage, which is not allowed in MT-HVdc systems. The control strategy consists of injecting two circulating ac currents and two dc currents that allow the energy balance between the arms of the converter and the general energy balance of the topology. The dc and ac currents are decoupled and allow control over load variations and reference changes in the dc-links. The proposed topology is mathematically modeled and the control method is then derived. Simulation results are presented to validate the proposed system.

Internal Energy Balance of a Modular Multilevel Cascade Converter Based on Chopper-Cells With Distributed Energy Resources for Grid-Connected Photovoltaic Systems

This article presents a methodology to control the internal energy balance of a modular multilevel cascade converter (MMCC) with distributed energy resources. The converter is characterized by a high voltage multi-terminal DC link connected to a three-phase MMCC with distributed photovoltaic arrays. Each modular arm structure is composed of bidirectional cascaded chopper cells with floating capacitors connected to the photovoltaic array through a DC/DC converter. Based on the power flow equations developed for the individual cells, a control methodology is applied to maintain the internal energy balance of the MMCC under power imbalance between the cells. The operation at different levels of irradiance is discussed to allow the operation with individual cells with zero energy generated from the photovoltaic array. Zero power cells are used to maintain three-phase output voltage and stable MMCC operation. Power balance between the arms is achieved through of the AC circulating currents in the MMCC arms without affecting the DC link and AC output currents. This converter topology and control methodology is suitable for hybrid renewable energy systems such as wind-solar power systems. Comprehensive experimental results are presented to validate operating principles and control methodology.

Cascaded Modular Multilevel Converter and Cycloconverter Based Machine Drive System

Low-speed drive is one of the challenges for modular multilevel converters (MMCs) due to large capacitor voltage fluctuation. In this article, a cascaded MMC and cycloconverter (CCV) based machine drive system is proposed to ensure stable operation of medium-voltage and low-speed machine. The MMC provides medium-frequency ac voltage for the CCV, and the CCV converts the medium-frequency ac input to low-frequency ac output required by the machine. Detailed analysis about MMC's operation frequency, device current stress, and submodule (SM) capacitance are given in this article. Proposed drive system can operate at zero/low frequency under rated load torque, while the SM capacitance is much smaller than that in existing methods. Simulation and experimental studies are conducted, and the results verify the effectiveness of the proposed system.