Single-stage Power Conversion Research Articles

A Multiport Current-Fed IIOS Dual-Half-Bridge Converter for Distributed Photovoltaic MVDC Integration System

The input-independent output-series (IIOS) dc-dc converter structure possesses the capability to achieve high voltage gain, single-stage power conversion and multiport independent control, which is suitable for distributed photovoltaic (PV) power collection system. However, if the multiport input powers are different, the output voltage of each submodule (SM) will be uneven, which might lead to power degradation and device damage. In order to address SM output voltage imbalance problem, a voltage self-balancing output-series dual-half- bridge (OSDHB) converter based on multi-winding coupled-inductor (MWCI) is developed in this paper. By multiplexing the SM secondary side switches in OSDHB, the unbalanced power between SMs can be directly transmitted to the target SM, without the requisition for transmission one by one. And all power switches possess zero-voltage switching characteristic. Therefore, the proposed IIOS-DHB features high efficiency, low cost, simple control and more adaptive to distributed PV power generation system. The topological configuration, operating principle and self-balancing performance are presented. Finally, the full-scale simulations and three submodules down-scale experiment hardware platform have been conducted to verify the theoretical analysis of the proposed IIOS-DHB.

Control of PV power plants with quasi-Z-source cascaded H-bridge multilevel inverters under failure

At the present time, quasi-Z-source cascaded H-bridge multilevel inverters (qZS-CHBMLI) have gained attention in photovoltaic (PV) applications, due to their advantages over traditional multilevel inverters. They allow single-stage power conversion of a PV power plant by independently adjusting the DC voltage in each module; thus, each PV array operates at the maximum power. This advantage permits dispensing with a DC/DC boost converter and reduces the number of modules required. This paper develops a novel control strategy for a qZS-CHBMLI connected to a single-phase system that guarantees proper operation when a fault occurs in a quasi-impedance source inverter (qZSI). The control strategy is employed in a grid-connected qZS-CHBMLI with three modules, each one with a quasi-impedance network, a 4.8 kW PV array and a voltage source inverter (VSI), with H-bridge topology. The purpose of the control system is to deliver a suitable DC voltage at the input of the VSI and ensure the grid power requirements after a fault in a module. The proposed control system is evaluated through a 40 s simulation in MATLAB/Simulink® in two cases: A) analysis of the system behaviour when there is a variation in the operation limit equation; and B) evaluation of the control strategy under dissimilar operating conditions. In addition, an experimental setup based on an OPAL RT-4510 unit and a dSPACE MicroLabBox prototyping unit is employed to validate the results. The results confirmed the correct response of the applied strategy with the failure of a single module.

Real-Time Implementation for the Robust Controller of the Switched Boost Inverter within an Autonomous Modified Nanogrid

SBI stands for switched-boost inverter and is a single-stage power converter used to connect low-power sources, such as solar photovoltaic (PV) arrays within a modified nanogrid, to loads. Despite its many benefits, such as the fact that it does not require expensive sophisticated dead-time circuitry, its duty ratio is limited to between 0 and 0.5. As a result, this publication is a contribution towards improving the SBI's performance for use in a modified nanogrid. Furthermore, it also presents a revolutionary strategy for a simple closed-loop control technique that overcomes the majority of inverter shortcomings and system nonlinearity. The suggested robust controller uses a metaheuristic optimization technique, called gorilla troops optimization (GTO), to optimize the performance of this controller. The robustness of the suggested controller is tested against the sudden change of the nanogrid input voltage (i.e., PV-voltage), modulation index of the inverter, and the step-change in DC-link output voltage of the inverter. The test results obtained from Matlab/Simulink software are compared with particle swarm optimization (PSO) – as another optimization algorithm. Furthermore, the proposed system is experimentally implemented with OPAL RT-4510v real-time hardware in the loop (HIL), rapid control prototyping, OP-8660 HIL controller and data acquisition platform.

Improved Dual Active Bridge DC–DC Converter With Symmetric Bipolar Output by Utilizing a Switched-Capacitor Circuit for Bipolar DC Distribution System

The bipolar dc distribution system is a promising solution due to its advantages in efficiency and reliability, but there are also challenges of pole voltage imbalance. By using a simple switched-capacitor circuit, this paper presents a semi-dual active bridge converter with symmetrical bipolar output characteristics. The converter is capable of single-stage power conversion, offering the advantages of low cost and high-power conversion efficiency. Moreover, the symmetrical bipolar output voltage can be achieved without an additional voltage balancer and feedback control under unbalanced load conditions, which reduces system cost and control system complexity. In addition, the proposed converter also has a significant advantage over existing solutions in terms of the number of semiconductor devices and magnetic components. A detailed analysis of the proposed converter is presented, including the operation principle, steady-state performance, soft-switching performance, voltage gain, voltage/current stresses, efficiency and loss analysis, and control method. Finally, a 1-kW prototype is developed and tested to verify the performance of the proposed converter.

Linearized Minimum Current Stress Modulation Scheme of Single-Phase Bidirectional DAB AC–DC Converters

In this paper, the detailed steps for the derivation of linearized minimum current stress (LMCS) modulation scheme for single-phase bidirectional and isolated dual active bridge (DAB) ac-dc converters is presented. In order to reduce the current stress of the converter, a Lagrange multiplier method (LMM) scheme is designed to obtain the control coordinates constraint on the minimum value of the current stress. Compared with the conventional minimum current stress (MCS) control scheme, the proposed scheme realizes the linearization of power control, which significantly reduces the complexity of the controller algorithm. Moreover, the synchronous inverter control applied to the back-stage full-bridge is designed. Thus, the single stage power conversion is realized and the converter topology is electrolytic capacitorless, which promote the improvement of system reliability and power density. The impact of the ZVS scheme is analyzed in detail, and the adaptive-ZVS scheme for less system loss is selected. Finally, experimental results confirm the validity and feasibility of the proposed control scheme.

A Novel Integrated Electronic Lighting Driver Circuit for Supplying an LED Projection Lamp with High Power Factor and Soft Switching Characteristics

The traditional light source of projection lamps adopts a halogen lamp, which has the advantages of high brightness, but its luminous efficiency is not good and consumes energy. A light-emitting diode (LED) has the characteristics of high luminous efficiency and energy savings and can be used as a new light source for projection lamps. The conventional two-stage electronic lighting driver circuit for supplying an LED projection lamp is composed of an AC-DC converter with power factor correction (PFC) as the first stage and a DC-DC converter for providing rated lamp voltage and current as the second stage. The conventional LED projection lamp driver circuit has more circuit components, a higher cost and limited efficiency. Therefore, this paper proposes a novel electronic lighting driver circuit for supplying an LED projection lamp with PFC function, which integrates a modified stacked dual boost converter and a half-bridge LLC resonant converter into a single-stage power-conversion circuit. The inductor inside the modified stacked boost converter is designed to operate at discontinuous conduction mode (DCM) for the driver circuit achieving PFC. Wide bandgap semiconductor devices silicon carbide (SiC)-based Schottky diodes are utilized to reduce power diode losses, and soft switching is implemented in the proposed LED projector lamp driver circuit to reduce the switching losses of the power switches and thus improve circuit efficiency. This paper has completed a single-stage prototype driver circuit for an LED projection lamp with PFC function, and the prototype circuit has a high power factor (PF > 0.98), low input current total-harmonic-distortion (THD < 6%) and high efficiency (>89%) in the case of an AC input power supply with an RMS value of 110 volts, and both power switches have the characteristics of soft switching.

A Forward-Type Single-Stage Multi-Input Inverter With Series-Time-Overlapping Power Supply

A Forward type single-stage multi-input inverter with series-time-overlapping power supply is proposed. The circuit structure and topological family, energy management control strategy (EMCS), high frequency (HF) switching process analysis, the relationship between multiple duty cycles and power decoupling, common mode interference suppression between multiple inputs are fully studied. The circuit structure is composed of multi-input selection switches in series and an isolated bidirectional Forward type single input single output inverter. This topological family includes 6 circuits such as full-bridge type. A master-slave energy management SPWM compound control strategy with independent control of input source power based on input voltage feedforward and output voltage feedback is proposed. It realizes the energy management of the input source by controlling the instantaneous value of the output voltage and the output power ratio of the multiple inputs and achieves the smooth switching between the two power supply modes. The designed and developed 3kVA inverter prototype has excellent performances such as single-stage power conversion, HF electrical isolation, high conversion efficiency, small size and weight, wide duty cycle adjustment range, high output waveform quality, and strong load adaptability.

Reduced sensor based single stage charger with four quadrant capabilities using predictive control

Single stage battery chargers eliminate the DC link capacitor stage between two stage power conversion. In this work, a reduced sensor based four quadrant charger with single stage power conversion is realized with AC–DC matrix converter topology. Although, a small capacitor filter on DC side is used in this configuration, it is only required to supply or absorb high frequency ripple component of the battery current, to prevent the battery from being damaged. The grid current estimation is done using the converter switching model and AC side filter model, leading to the elimination of grid current sensor. The simple model predictive control used here in conjunction with instantaneous reactive power theory, avoids the use of any proportional integral controller, thus making the control scheme simpler. The single stage design increases power density, and the charger’s dependability is increased by the absence of a large electrolytic capacitor. While the battery charges and receives power from the grid, the AC–DC matrix converter used here, performs a voltage bucking function. The simulation results and experimental findings from a lab-developed hardware prototype are used to validate the design and control of the proposed charger.

An AC-DC LED Integrated Streetlight Driver with Power Factor Correction and Soft-Switching Functions

The use of light-emitting diodes (LEDs) in street lighting applications has been greatly welcomed with the current trends of energy saving, environmental protection, carbon reduction, and sustainable development. This paper presents a novel AC-DC LED integrated streetlight driver that combines an interleaved buck converter with a coupled inductor and a half-bridge series resonant converter with a full-bridge rectifier into a single-stage power conversion topology with power factor correction (PFC) and soft switching capabilities. The PFC is achieved by designing the coupling inductor in the interleaved buck converter sub-circuit in discontinuous conduction mode. In addition, the resonant tank in the half-bridge series resonant converter sub-circuit is designed to be similar to an inductive load, thus giving the power switch a zero-voltage switching (ZVS) function, decreasing switching losses and increasing the overall efficiency of the proposed circuit. A prototype circuit of the proposed LED integrated streetlight driver with a power rating of 165 W (235 V/0.7 A) and 110 V input utility voltage has been developed and tested. According to the measurement results, a power factor greater than 0.98, a total harmonic distortion coefficient of the input current less than 3%, and an efficiency greater than 89% were obtained in the AC-DC LED integrated streetlight driver. Therefore, the experimental results are satisfactory and demonstrate the functionality of the proposed AC-DC LED integrated streetlight driver.

A Family of Symmetrical Bipolar Output Converters Based on Voltage-Multiplying Rectifiers for Interfacing Renewable Energy With Bipolar DC Microgrid

The bipolar dc microgrid system is considered a greatly promising solution to interface various renewable energy sources and emerging loads due to its advantages in efficiency and reliability. However, pole voltage imbalance and lack of superior bipolar power conversion topologies limit the development and application of bipolar DC microgrid systems. In this context, this paper proposes a family of multi-port converters based on voltage-multiplying rectifiers to achieve symmetrical bipolar output voltage and power conversion between renewable energy sources and bipolar buses. In the proposed topologies, single-stage power conversion, without voltage balance feedback control, and a low number of components are obtained. Furthermore, the bulky balancing inductor is eliminated to improve conversion efficiency and reduce the volume of the system. Moreover, the higher voltage gain, smaller input current ripple, and lower voltage stress of semiconductor devices make it ideal for interfacing renewable energy sources with bipolar DC microgrids. The derivation method for the proposed topology family is first introduced. Then, a typical topology in the proposed converter family is analyzed in detail as an example, including the operation principle, steady-state performance, parasitic parameter effects, design considerations, efficiency analysis, control method, loop designing, etc. Finally, a 1-kW prototype is developed and tested to verify the performance of the proposed converter.

Deadbeat Power Distribution Control of Single-Stage Multiport Inverter-Fed PMSM Drive for Hybrid Electric Vehicles

Single-stage multiport inverter (SSMI)-fed motor drives are promising solutions for multisource hybrid electric vehicles (HEVs) since the dc-dc converter is removed and all the active power is delivered within a single power conversion stage. However, this topology presents inherent coupled issues in controller design because power distribution should be achieved simultaneously in addition to stator current control. To address this issue, an equivalent two-level model is proposed to achieve decoupled control of the SSMI, where stator current control is achieved by regulating the active vectors, and power distribution is achieved by regulating the zero vectors. A deadbeat power distribution scheme is developed under the equivalent two-level model. The proposed scheme provides these advantageous features: fewer computational burdens without complicated sector selection and dwell time calculation under the unevenly distributed voltage vector diagram, fewer adjusted parameters, and fast dynamic response. Moreover, the power distribution capability of the SSMI with the proposed scheme is also analytically revealed. A series of experimental results demonstrate the excellent performance of the proposed deadbeat power distribution control scheme.

H5-CFDAB: A Current-Fed Dual-Active-Bridge Converter for Application in Modular DC Solid-State Transformer

Isolated DC-DC converters in DC Solid-State Transformers (DCSSTs) must conform to stringent requirements such as high voltage conversion ratio, high efficiency, and reliable operation with grid fault handling capabilities. This paper proposes a novel current-fed Dual-Active-Bridge (CFDAB) converter, named H5-CFDAB, for modular DCSST application. Compared to the existing topologies, the proposed converter provides a single-stage power conversion with reduced component count and semiconductor Volt-Ampere (VA) rating. The proposed modulation scheme makes the pulse widths of the transformer winding voltages independent of the duty ratio. This allows further optimization of the high-frequency-link (HFL) characteristics like minimized HFL conduction losses and full range Zero-Voltage-Switching (ZVS) at turn ON for the switches, further increasing the converter efficiency. Several modules of the proposed H5-CFDAB converter connected in Input-Series-Output-Parallel (ISOP) configuration makes the system suitable for Medium-Voltage (MV) high-power applications. The operation of the proposed converter is analyzed in detail, including the HFL characteristics and derivation of the ZVS conditions for the switches. In addition, a closed-loop control scheme is proposed for achieving tight regulation of the converter outputs during transients. A 1.2 kW laboratory prototype is built to verify the effectiveness of the proposed converter, along with the control scheme.

Zero-Vector-Regulation-Based Closed-Loop Power Distribution Strategy for Dual-DC-Port DC–AC Converter-Connected PV–Battery Hybrid Systems

The dual-dc-port dc-ac converter-connected photovoltaic (PV)-battery hybrid systems present high-efficiency and low-cost features with single-stage power conversion as PV and battery are connected to the grid directly. However, it is challenging to achieve flexible power distribution in this configuration due to its coupled features in grid-side current tracking and power distribution. To deal with this issue, this paper proposes a zero vector regulation-based closed-loop power distribution strategy for the dual-dc-port dc-ac converter-connected PV-battery hybrid systems. By modeling the dual-dc-port dc-ac converter as an equivalent two-level one, an extra control freedom for power regulation is accessible and a closed-loop power control is adopted for flexible power distribution by zero vector regulation. With the proposed power distribution strategy, the desirable quality of the grid-side current is achieved without complicated voltage vector synthesis, along with good adaptivity to different modes/voltages and flexible power control. Besides, detailed power distribution discussion and analysis with different proportions of zero vector are carried out. Finally, the islanded microgrid experimental tests are conducted to verify its effectiveness and feasibility.

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.

New MPPT Control Methods for Grid Connected PV System to Produce Green Hydrogen

In this document, we used Matlab 2022 software to design a 50 kW PV array and connect it to the grid with a single stage power converter. The power control strategy uses a combination of MPPT (P&O) and inverter control algorithms. For this reason, we changed the power control algorithm for current control. The next work is to connect this system to electrolyzers and fuel cells and find new optimization methods for grid-connected systems to produce green hydrogen.

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.

Performance Analysis of Z-Network Plus Switched-Capacitor Boost DC-DC Converter

A multi-stage conversion is necessary when a basic DC-DC boost converter (BBC) raises the low voltage of PV panels to a high voltage, which is then used as the dc-link voltage of the inverter. The aim can be achieved with this multi-stage power electronic conversion, but more intermediate converters are needed. Additional converters increase the number of components while also lowering overall efficiency, which lowers reliability. The Z-Source Inverter (ZSI) is a practical alternative that not only carries out single-stage power conversion (boosting plus DC-AC conversion), but also successfully gets rid of the drawbacks of the traditional voltage-source and current-source inverters. Switching Inductor (SL) cells are used in place of the Z-Source Inverter (ZSI) inductors to maximize voltage gain. This device replaces one of the inductors of the QZSI with an SL cell (QZSI). The Z-network combined with Switched-Capacitor Boost DC-DC Converter (ZSCBC) with ANFIS Controller is suggested in this project to achieve high gain for a range of duty ratios. The Z-network plus Switched-Capacitor DC-DC Boost Converters with ANFIS controller developed in MATLAB Simulink and also with PI controller. The dynamic performance of the Z-network plus Switched-Capacitor DC-DC Boost Converters with ANFIS controller is compared with that of PI controller. Keywords: Boost converter, Switched-Capacitor, Quasi-Z Source DC-DC Converter, Z-source Inverter.

A Flexible Non-Isolated Multiport Converter to Integrate Battery and Ultracapacitor for Electric Vehicle Applications

In order to maximize the utilization of battery and ultracapacitor (UC) in a hybrid energy storage system (HESS) for electric vehicle (EV) applications, a DC-DC power electronic interface with proper management of power flow is very crucial. Aiming at this, a non-isolated two input and one output multiport converter configuration, which is capable of achieving dynamic flexibility in power flow while meeting fluctuating load demands of an EV is proposed. The converter provides dedicated power flow paths for high and low currents, which can be flexibly reallocated according to the load current and voltage level of the energy sources. This eventually facilitates in maneuvering the flow of power by dynamically allocating the desired energy source with the appropriate current flow path. Moreover, the proposed converter offers bidirectional power transfer capability for all the ports and allows single stage power conversion in every possible power flow combinations. The converter configuration along with different operating modes and control strategy are discussed and the performance is validated through experimentation using a laboratory scale hardware prototype.

Dynamic Control of Traction Motor for EV Fed via Dual Source Inverter with a Two Battery System

An electric vehicle uses multiple energy-storage systems to power the traction motor. Dual-source inverters (DSIs) are used for single-stage power conversion by skipping the dc/dc boost converter stage; therefore, eliminating the passive magnetic storing element which improves the overall efficiency of the drive; moreover, multiple energy-storage systems improve the power density of the system. This article discusses the fine control of a traction motor from zero speed to rated speed supplied through a dual-source inverter. Field-oriented control with space vector modulation technique is applied to achieve closed-loop control. Two dc sources are used, one having a higher-voltage battery and one a lower-voltage battery. The higher-voltage battery is the main battery which supplies power to the traction motor, whereas the lower-voltage battery supplies power to supplementary loads of the EV. This article presents improved dynamic behaviour of an induction-motor-driven EV fed from a dual-source inverter using modified closed-loop field-oriented control with space vector modulation. The improvement includes reduced control complexity due to space vector modulation and achieving the option of EV operation in an emergent situation using the same converter and control system. The simulated performance of the presented system is obtained in MATLAB/Simulink. A step-down experimental prototype is used for verification of effective control of the induction motor as the EV is under constant torque variable speed operation with real-time parameters such as power, power factor, current harmonics, and voltage/current stresses across the switch using two batteries individually.

A hysteresis current control PWM for PV tied Z-source NPC-MLI fed induction motor with neutral point balancing

Photo-voltaic (PV) tied Z-source Neutral-point clamped NPC-MLI (Z-NPC-MLI) is used in solar grid connected applications due to its improved performance related to conservative inverters due to its single stage power conversion. Though the Z source inverters adaptation is accepted in grid connected technology, the need for appropriate controller to meet out the grid/standalone requirements is becoming necessary. The space vector pulse width modulation (SVPWM) strategy is a prominent modulation technique for Z-source NPC-MLIs due to their appropriate voltage vector selection opportunity. The current controller (CC) based SVPWM is not attempted, which is the most essential consideration for the grid connected inverter to provide a low harmonic distortion, high quality current. With all this aim, the paper presents a PV tied Z-NPC-MLI grid connected system with a unique hysteresis current control SVPWM (HSVM) strategy with neutral point (NP) balancing control. The simulation results are confirmed the feasibility and reliability of the proposed CC for the PV tie grid connected Z- Source MLI.