Single-stage Dc Research Articles

Grid-Connected Single-Stage DC–AC Converter for Solar PV Applications

Photovoltaic (PV) has become an important alternative because of the increased demand for electricity and the limited supply of traditional energy sources. Harmonic distortion (HD) on the grid-connected PV can lead to several undesirable outcomes, including overheating of connected equipment, frequent grid interruptions, reduced accuracy of electrical meters, and an increase in the required current. This manuscript proposes the novel use of the Sunflower Optimization (SFO) Algorithm in grid-connected single-stage DC–AC converter with minimizing Total HD (THD) and enhancing the efficiency of the system as its primary objective. The SFO algorithm is used to maximize the system's features and control the switched inductor boost converter. The proposed technique is then simulated using MATLAB and its performance is contrasted with other existing technologies Recurrent Neural Network (RNN), Garra-Rufa Fish Optimization-Student Psychology Optimization Algorithm (GRFO-SPOA), and Fuzzy Logic Control (FLC). The proposed method attains an efficiency of 97% with a low THD of 3.1%. The findings suggest that the proposed method outperforms the existing approaches.

Conduction Loss Minimized Modulation and Design of a DAB-based Single-stage DC to Single-Phase AC Converter for EV Charger Application

Conduction Loss Minimized Modulation and Design of a DAB-based Single-stage DC to Single-Phase AC Converter for EV Charger Application

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.

Modular battery-integrated bidirectional single-stage DC–DC converter for solar PV based DC Nano-grid application

Attributed to the growing focus on energy savings and eco-friendliness, the solar PV-based DC Nano-grids for residential and commercial buildings are becoming more popular. On the other hand, solar photovoltaic systems (SPV) are intermittent and unreliable due to their dependency on external factors such as solar irradiance, ambient temperature, and unpredictable shadows. In addition, the power degradation occurs in SPV systems due to module mismatch losses caused by various factors like partial shading (PS), dissimilar aging effect, different power ratings, etc. The conventional PV system cannot handle all these issues, so it is essential to address them. This paper proposes a bidirectional modular PV battery system (BMPBS) that uses non-isolated buck and boost converter combinations. This system is capable of self-sustained generation, storage, and bidirectional power flow within the Nano-grid. The proposed BMPBS can handle losses due to module mismatch and intermittency in SPV with the help of battery storage system (BSS), making the overall SPV system reliable. It requires single-stage power conversion to extract maximum power from each PV module and BSS charging and discharging. Its modular design allows it to function across various voltage, power, and BSS choices. This paper discusses the operation, steady-state analysis, and dynamic analysis of the proposed BMPBS. The performance of the proposed BMPBS is validated using a state-of-the-art experimental setup with two PV modules, each having a rating of 90WP.

Software-Reconfigurable Multistage Constant Current Wireless Battery Charging Based on Multiharmonic Power Transmission

Wireless power transfer (WPT) technology has been widely applied in electric vehicle battery chargers because of its convenience, reliability, and safety. A typical battery charging profile consists of a constant current (CC) charging process followed by a constant voltage charging process. Recently, a multistage constant current (MSCC) charging profile is proposed to increase the charging speed, flexibility, and other performances. MSCC charging profile consists of multiple CC charging processes, which are applied to the battery in turn. This article proposes a low-cost software-reconfigurable MSCC charging technique for a typical single-stage dc–dc series–series compensated WPT converter using multiple high-order harmonics power transmission approach. Such a technique does not require any additional component and it can achieve inherent load-independent CC output and zero phase angle input characteristics. Moreover, it provides a precharge process for deeply discharged batteries to increase their lifetime. A scaled-down design example and the corresponding laboratory prototype are implemented to verify the proposed method.

A Common-Ground-Type Five-Level Inverter with Dynamic Voltage Boost

Today, transformerless inverters (TIs) are widely applicable in different solar photovoltaic (PV) grid-connected applications owing to their promising features, such as higher efficiency and power density. However, high-frequency common-mode voltage (CMV) in these topologies can result in high leakage current, electromagnetic interference, and lack of safety, reducing the whole system’s reliability. To resolve the problems associated with TIs, this paper proposes a novel hybrid switched capacitor (SC)-based common-ground (CG) transformerless inverter (TI) topology, which can be applied in grid-connected photovoltaic (PV) applications. The boost inductor is integrated to achieve continuous input current and dynamic voltage gain. In addition, the proposed circuit comprises nine switches and two SCs with a single input DC source. It can generate five-level AC voltage with voltage boosting within a single-stage DC–AC power conversion. The working principles of the proposed topology, circuit description, and control technique are presented. Furthermore, the proposed inverter is comprehensively compared with other five-level TIs to show its superiority. Finally, a laboratory prototype is developed and tested to validate the practical viability of the proposed configuration.

A Novel Integrated Matrix Magnetics for Isolated Single-Stage DC–DC Converter

With the development of data center, promotion for efficiency and power density of the voltage regulator module (VRM) is paid considerable attention. Isolated VRM is suitable for the high-conversion-ratio dc–dc application. However, isolated VRM has many magnetic components, which take up a large proportion of the total volume. In this article, a novel integrated matrix magnetics structure is proposed, which integrates two elemental transformers and four output inductors into a single core. By integrating several discrete magnetic components, the volume of passive components, and high-current interconnections are reduced, leading to high power density and high efficiency. The integrated matrix magnetics is employed in an isolated single-stage converter, which can provide high output current. In addition, primary switches can achieve zero-voltage-switching (ZVS), and synchronous rectifiers of secondary side can achieve ZVS and zero-current-switching, so efficiency can be further improved. Besides, equivalent output inductance, voltage conversion ratio and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> calculation are derived to design the integrated matrix magnetics. Finally, a 48 V/1.8 V 144 W prototype of the isolated single-stage converter with integrated matrix magnetics is made and tested to verify the analysis.

A transformerless three‐level three‐phase boost PWM inverter for PV applications

Multilevel converters have seen rising demands in the past decades, due to their increased power ratings, enhanced power quality, low switching losses and reduced electromagnetic interference. Prominent among them are the three-level (3L) neutral point clamped and the flying capacitor inverter topologies along with their derivatives. Nevertheless, the main drawback of these topologies is the requirement of a front-end boost DC–DC converter to compensate the high dc-link voltage demand, which is usually twice the grid peak voltage. This multi-stage power conversion further pulls down the overall system efficiency. A single-stage dc–ac power converter with boost capability offer an interesting alternative compared to the two stage approach. Considering this aspect, a novel three-level three-phase boost type inverter is introduced in this paper for general-purpose applications (prominently grid-connected renewable energy). The proposed inverter would reduce the DC-link voltage requirement to half using the same or even less number of active and passive components, compared to the conventional three-level neutral point clamped and flying capacitor family. The principle of operation and theoretical analysis are discussed in detail. The design methodology along with simulation and experimental waveforms for a 5 kVA inverter are presented to prove the concept of the proposed inverter topology for practical applications.

Dual-Path Series-Resonant Single-Stage DC–AC Converter Operating in Hybrid Mode

This article proposes a dual-path series-resonant single-stage dc–ac converter operating in hybrid mode. The proposed circuit provides dual power transfer paths regardless of the switching state; secondary diodes of the proposed converter are integrated into one of the two complementary pairs of the secondary-side switches, thereby contributing to the reduced circuit complexity and cost. The proposed dc–ac converter operates in below resonance mode (BRM) above the computed instantaneous power level and in above resonance mode (ARM) below this level. During BRM, it can achieve a step-up function with high power conversion efficiency. Since BRM is devoid of step-down capability, ARM is developed and used in the region where the step-down operation is required. We also identify the boundary of operation modes in the hybrid-mode single-stage dc–ac converter and provide guidelines to design the circuit parameters. Finally, we implemented a 300-W prototype to validate the analysis and benefits of the proposed converter.

A Novel Single-Stage Five-Level Common-Ground-Boost-Type Active Neutral-Point-Clamped (5L-CGBT-ANPC) Inverter

The conventional active neutral-point-clamped (ANPC) inverter inherits excellent high-frequency common mode voltage (CMV) mitigation ability but with a restricted voltage gain. This letter proposes a novel five-level ANPC inverter that is able to accomplish voltage-boosting within a single-stage dc–ac power conversion. A common ground in the proposed topology not only mitigates the high-frequency CMV but also enhances the dc-link voltage utilization. The proposed topology exhibits lower voltage stresses and higher compactness when compared with a conventional two-stage five-level ANPC inverter. The proposed inverter saves three power switches and one capacitor while enhancing the overall efficiency. Simulations and experimental tests have validated the overall operation, efficacy, and practicality of the proposed ANPC inverter.

A New Approach for Impedance Tracking of Piezoelectric Vibration Energy Harvesters Based on a Zeta Converter.

Piezoelectric energy harvesters (PEHs) are a reduced, but fundamental, source of power for embedded, remote, and no-grid connected electrical systems. Some key limits, such as low power density, poor conversion efficiency, high internal impedance, and AC output, can be partially overcome by matching their internal electrical impedance to that of the applied resistance load. However, the applied resistance load can vary significantly in time, since it depends on the vibration frequency and the working temperature. Hence, a real-time tracking of the applied impedance load should be done to always harvest the maximum energy from the PEH. This paper faces the above problem by presenting an active control able to track and follow in time the optimal working point of a PEH. It exploits a non-conventional AC–DC converter, which integrates a single-stage DC–DC Zeta converter and a full-bridge active rectifier, controlled by a dedicated algorithm based on pulse-width modulation (PWM) with maximum power point tracking (MPPT). A prototype of the proposed converter, based on discrete components, was created and experimentally tested by applying a sudden variation of the resistance load, aimed to emulate a change in the excitation frequency from 30 to 70 Hz and a change in the operating temperature from 25 to 50 °C. Results showed the effectiveness of the proposed approach, which allowed to match the optimal load after 0.38 s for a ΔR of 47 kΩ and after 0.15 s for a ΔR of 18 kΩ.

Single-Stage Regulated Resonant WPT Receiver With Low Input Harmonic Distortion

Resonant rectifier topologies would be a promising candidate for achieving simple, compact, and reliable single-stage wireless power transfer (WPT) receiver if not for the lack of good DC regulation capability. This paper investigates the problems that prevent the feasibility of single-stage DC regulation in resonant rectifier topologies. A possible solution is the proposed differential resonant rectifier topology, of which the rectifier is designed to have a relatively constant AC voltage, and that phase shift control is used to achieve relatively good output regulation. Design considerations on the reactive component sizing, magnetic component design, frequency and phase synchronization, small signal modelling, and closed-loop feedback control design, are discussed. Experimental results verified that the proposed WPT receiver system can achieve single-stage AC rectification and DC regulation while attaining the key features of low harmonic distortion in its AC output voltage, continuous DC current, and zero-voltage-switching (ZVS) operation over a wide operating range.

Novel Active-Neutral-Point-Clamped Inverters With Improved Voltage-Boosting Capability

Conventional active-neutral-point-clamped (ANPC) inverters exhibit low voltage gain that inherently leads to a high dc-link voltage requirement. An improved ANPC inverter that is capable of generating five voltage levels has recently reduced the dc-link voltage twofold to achieve unity gain. This led to the development of a single-stage dc–ac power converter with no frontend boost dc–dc converter. This article proposes novel ANPC inverters capable of unity or boosted voltage gain while generating higher voltage levels. The first topology can provide a voltage gain of 1.5 and extends the number of levels to seven by incorporating only one additional switch. The topology can also be extended by adding three switches and one floating capacitor to generate nine levels with unity voltage gain, or 11 levels with a voltage gain of 2.5. The proposed ANPC inverters and their operations are comprehensively discussed. Experimental results are provided to validate the feasibility of the proposed ANPC inverters.

An Improved PWM Strategy for Z-Source Inverter With Maximum Boost Capability and Minimum Switching Frequency

Z-source inverter provides a competitive single-stage dc–ac power conversion with the capability of both buck and boost voltage regulation. In order to maximize voltage gain and to increase efficiency, this paper proposes an improved pulse-width modulation (PWM) strategy. By adjusting the shoot-through duty ratio of one-phase leg, it regulates the average value of intermediate dc-link voltage, which is the same as the instantaneous maximum of three-phase line voltage in one switching time period $(T_{s})$ . And the other two-phase legs maintain the fixed switching states. Thus, the equivalent switching frequency of power devices in the inverter bridge is reduced to $1/ 3f_{s}$ ( $f_{s}$ is the frequency corresponding to $T_{s}$ ). The operating principles and closed-loop controller design are analyzed and verified by simulation and experiments. Compared with the existing PWM strategies, the improved PWM (IPWM) strategy demonstrates higher efficiency under full operation range of low voltage gain (1.27-2) application. However, with the IPWM strategy, the inductor current and capacitor voltage contain six-time-line-frequency ripples, which consequently require large size of the passive components when the output frequency is very low. Thus, it is also suitable for 400–800-Hz medium frequency aircraft and vessel power supply system due to a relatively high output line frequency. Furthermore, the idea of IPWM strategy can be extended to other kinds of three-phase impedance network-based inverters.

Novel High-Power Nonresonant Multichannel LED Driver

This paper reports a multichannel high-power light-emitting diode (LED) driver employing a single-stage dc–dc power conversion and control technique with dimming capability. A half-bridge nonresonant converter with symmetrical quadrupler rectifier output is implemented to convert available dc power to multiple current regulated dc outputs for driving LED loads. The dc–dc power conversion efficiency of about 98% is obtained from advantageous operation of the converter with complete soft switching of all semiconductor devices and reduction in power conversion stages. The driver possesses inherent protection against LED failures due to its topology for both electrically open and short-circuit conditions of the LEDs. This patented converter is applicable for high-power LED lighting.

Three-Phase Three-Level Flying Capacitors Split-Source Inverters: Analysis and Modulation

Single-stage dc–ac power converters with boost capabilities offer an interesting alternative compared to two-stage architecture. One of the recently proposed single-stage dc–ac power converters is the split-source inverter (SSI). This paper extends the SSI topology from the two-level operation to the three-level one using the flying capacitors (FCs) configuration. Among the diode-clamped SSI (DC-SSI) and FC-SSI, the second one is proposed in order to avoid the need of two isolated dc sources. This paper shows that the FC-SSI provides additional merits compared to the two-level SSI in terms of input inductance requirements using the same switching frequency, voltage stresses across the active switches, and total harmonic distortion of the output voltage. Such results are obtained by discussing the analysis and the modulation of this topology, considering some simulation results, and comparing it to some other existing topologies to show its properties and limitations. Finally, a reduced-scale 1.5-kVA three-level FC-SSI is implemented experimentally to validate its functionality and verify the proposed analysis and modulation properties.

An Isolated Bidirectional Single-Stage DC–AC Converter Using Wide-Band-Gap Devices With a Novel Carrier-Based Unipolar Modulation Technique Under Synchronous Rectification

A novel carrier-based unipolar-sinusoidal pulse width modulation (SPWM)-oriented modulation technique with synchronous rectification for isolated bidirectional single-stage high-frequency-ac link dc–ac converters using SiC MOSFET is presented in this paper. The dc–ac converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. A carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification is proposed to realize zero-voltage-switching (ZVS) for the FB inverter and zero-current or zero-voltage-switching (ZVS/ZCS) for the cycloconverter in all load ranges, and to suppress the voltage spikes introduced by the transformer leakage inductance as well. In order to increase the switching frequency, efficiency, and power density, this paper proposes to utilize SiC MOSFETs for the converter. Synchronous rectification is implemented to further increase the converter efficiency. With the novel modulation technique, there are two switches in the cycloconverter that are continuously on at each interval, which eliminates on-fourth of the switching loss. A simulation model and a 400 VDC–240 VAC, 1.2=kW prototype have been developed to validate the effectiveness and performance of the proposed unipolar soft-switching modulation technique and SiC converter.

A Single-Stage DC Uninterruptible Power Supply

A single-stage DC uninterruptible power supply (UPS) is proposed in this paper. Basically, the proposed converter is an integration result of a power factor correction circuit with a dc-to-dc converter to achieve simple hardware circuit, high efficiency, and low cost for extra UPS function. Under normal operation, a novel two-switch SEPIC converter operates as an ac to dc converter with sinusoidal input current, unity power factor, and low ripple dc output voltage, and as a battery charger if a battery is added. Since both the input boost supply and the output supply can be controlled independently, a fast transient response can be maintained at both the input for active current wave shaping and at the output for good output regulation. When the ac source is in an outage condition, the proposed converter functions as a dc-to-dc buck-boost converter; therefore, the desired dc output voltage can be provided. Finally, some experimental results are presented for verification.