Input Voltage Regulation Research Articles

Digital Functional Blocks Implementation of PWM and Control for a High-Frequency Interleaved Y-Inverter Motor Drive

This paper is about the development and demonstration of a motor drive for e-transport applications based on an innovative hybrid Si-SiC dual switching frequency interleaved buck–boost Y-inverter and a single-rotor Halbach machine. In particular, the focus is the implementation of the required discontinuous inverter modulation scheme, input voltage feed-forward and motor currents feedback control loops, as well as over-voltage, over-current, and over-temperature protections, using an off-the-shelf commercial hardware platform enabling straightforward Simulink-environment programming of all parts, while ensuring the high switching frequency capability required by wide-band-gap semiconductors. Experimental results showed good inverter efficiency, transient dynamic response to load changes, input voltage regulation, and fully functional protection capability, validating the proposed approach as a powerful option for reducing system development time and cost.

A New Flying Capacitor-Based Buck–Boost Converter for Dual-Purpose Applications

A novel dual-purpose common ground dc–dc/dc–ac power converter is proposed in this article. It is based on the flying capacitor circuit along with a boost circuit, which in turn provides a wide range of input voltage regulation with the capability of stepping up or down the output voltage. The same components are used under both dc–dc and dc–ac modes, which reduces the redundancy of the used devices. Particular attention is dedicated to the working modes of the proposed solution. The special control system is implemented to provide acceptable current and voltage quality in off-grid and grid-connected modes. To underline the pros and cons of the proposed solution, a comprehensive comparison is performed. Finally, the performance of the proposed dual-purpose power converter is investigated through an experimental 3.5-kW/5-kW setup, for dc–ac and dc–dc operating modes, respectively. Main oscillograms along with efficiency analysis are presented and discussed in conclusions.

Novel Resonant Power Feedback DC-DC Converter

In this article, a novel soft-switched isolated dc–dc converter topology is proposed that consists of a main power converter using a standard topology, augmented with a resonant power feedback circuit. The power feedback circuit utilizes a fraction of the output power to regulate the input voltage of the main converter. Input voltage regulation proves to be advantageous in applications where wide range of source voltage variations are experienced, such as in photovoltaic microinverters. The operation of main converter with a regulated input voltage results in a near-constant phase-shift angle and a high-frequency current wave shape with a low root mean square value over the entire range of operating conditions. Moreover, the operation with near constant phase-shift angle and the presence of additional resonant current in the feedback circuit extend the range of soft-switched operation of semiconductor devices in the converter. The proposed converter topology and its theoretical analysis is verified through an experimental prototype.

Transformer‐Based Z‐Source Inverter with MVDC Link

Z‐source inverters have attracted considerable attention in renewable energy systems like photovoltaic (PV) systems due to advantages such as buck–boost power conversion in single stage, shoot-through capability, and wide range of input voltage regulation. Transformer-Based Z-source inverters (TransZSI) based on magnetically coupled inductors and reduced number of passive components can be used to improve the boost capacity of these inverters, and to increase the voltage levels. Medium voltage DC (MVDC) is being used more and more in distribution grids and renewable energy systems. This paper presents a transZ-source inverter with MVDC link where renewable energy systems and energy storage systems can be integrated. The active and reactive powers and DC voltage are controlled by acting on the modulation index and shoot-through duty cycle of the converter. The trans-Z-source inverter is evaluated under different operating conditions to illustrate its suitable operation.

Improved Model Predictive Current Control of the versatile Buck-Boost Converter for a Photovoltaic Application

The digital implementation of all the control loops of a versatile buck-boost (VBB) dc-dc converter used in a stand-alone photovoltaic application is proposed in this paper to improve existing digital-analog sliding-mode-based implementations. All three control loops: maximum power point tracking (MPPT), fast input voltage regulation, and inner high-bandwidth current control, have been programmed in the same digital signal controller (DSC). A Model Predictive Control (MPC) based algorithm has satisfactorily solved the challenge of implementing the nominal 100 kHz switching frequency current loop. The MPC cost function is distributed throughout the algorithm to achieve three specific goals: the tracking of the reference current (G1), a quasi-constant steady-state switching frequency (G2), and the assurance that the duration of an interval is larger than the time required to calculate it (G3). The third goal requires the current control to toggle between peak- and valley-modes depending on the operating point. The correct fulfillment of these control objectives on the proposed MPC-based algorithm has been validated through simulations and experimental tests performed on a purpose built-prototype.

Wide Range Series Resonant DC-DC Converter with a Reduced Component Count and Capacitor Voltage Stress for Distributed Generation

This paper proposes a galvanically isolated dc-dc converter that can regulate the input voltage in a wide range. It is based on the series resonance dc-dc converter (SRC) topology and a novel boost rectifier. The proposed topology has a smaller number of semiconductors than its SRC-based existing topologies employing an ac-switch in the boost rectifier. The proposed dc-dc converter comprises only two diodes and one switch at the output side, while the existing solutions use two switches and two diodes to step up the voltage. The proposed converter boosts the input voltage within a single boosting interval in the positive half-cycle of the switching period. In addition, the resonant current in the negative half-cycle is sinusoidal, which could enhance the converter efficiency. The resonant capacitor voltage is clamped at the level of the output voltage. Therefore, the voltage stress of the capacitor could significantly reduce at various input voltage and power levels. This makes it perfect for distributed generation applications such as photovoltaics with wide variations of input voltage and power. The converter operates at the fixed switching frequency close to the resonance frequency to obtain the maximum efficiency at the nominal input voltage. The zero-voltage switching (ZVS) feature is achieved in the primary semiconductors, while the diodes in the output-side rectifier turn off at nearly zero current switching. The mathematical model and design guidelines of the proposed converter are discussed in the paper. The experimental results confirmed the theoretical analysis based on a 300 W prototype. The maximum efficiency of the converter was 96.8% at the nominal input voltage, and the converter has achieved a wider input voltage regulation range than that with the boosting cell comprising an ac-switch.

Performance Improvement of PWM Control Methods for Voltage Step-Down in Series Resonant DC–DC Converters

The paper is focused on galvanically isolated series resonant DC–DC converters (SRCs) with a low quality factor of the resonant tank. These converters provide input voltage regulation at fixed switching frequency and good power density. Different modulation methods at the fixed switching frequency enable the implementation of the voltage buck functionality in these converters. The SRC under study is considered as a step-up front-end DC–DC converter for the integration of renewable energy sources in DC microgrids. The paper evaluates the voltage buck performance of the SRC achieved by using different pulse-width modulation (PWM) methods including conventional PWM and shifted PWM. Moreover, the new PWM methods, i.e., the hybrid shifted PWM (HSPWM), improved shifted PWM (ISPWM), and hybrid PWM (HPWM), are proposed to overcome the disadvantages of the existing methods. They improve the power conversion efficiency in the buck mode by reducing the power losses in the semiconductor switches and the isolating transformer of the SRC. The proposed and the existing methods are benchmarked in terms of the components stresses and power conversion efficiency. The presented findings have been experimentally validated by the help of a 200 W prototype, which demonstrated the lowest power loss in the case of the HPWM.

Simulation and Implementation of Single Phase Quasi Z-Source Series Resonance DC DC Converter for Photovoltaic Application

The paper presents quasi-Z source series resonant dc–dc converter with high performance for PV applications. Their multimode operation property features wide input voltage and load regulation range. Multimode operation achieved by pulse width modulation and phase shift modulation which gives boost and buck operating modes. Paper includes experimental setup which ensures 13volts ripple free output voltage.

Wide Input Voltage Range Operation of the Series Resonant DC-DC Converter with Bridgeless Boost Rectifier

The series resonant DC-DC converter (SRC) can regulate the input voltage in a wide range at a fixed switching frequency. In this work, the bridgeless rectifier, which is utilized intensively in the applications of the power factor correction, has been integrated into the SRC as a voltage step-up cell at the output-side of the SRC. It is shown that the conventional overlapping pulse-width modulation (PWM) of the two metal oxide semiconductor field-effect transistors MOSFETs in this rectification cell limits the input voltage regulation range of the converter due to excessive power losses in abnormal operating conditions. The abnormal operating conditions occur when the instantaneous voltage across the resonant capacitor is larger than the secondary voltage of the isolation transformer. This happens at high values of the DC voltage gain, i.e., low input voltages and high currents, which causes the resonant current to flow in the reverse direction in the same half-cycle through a parasitic path formed by overlapping PWM of the rectifier MOSFETs. The abnormal operation results in additional conduction loss in the converter as the MOSFETs of the bridgeless boost rectifier turn on at high current at the beginning of each half of the switching period. Accordingly, the overall efficiency of the converter significantly deteriorates. This paper proposes the hybrid PWM aiming to improve the efficiency of the SRC with a bridgeless boost rectifier in a wide input voltage regulation range. The converter swaps between the overlapping and the proposed short-pulse PWM schemes to drive the MOSFETs in the bridgeless boost rectifier. The transition between the two PWM schemes is defined according to the boundary condition that relies upon the operating point of the converter power and the input voltage. The proposed hybrid PWM scheme is analyzed and compared to the overlapping PWM at different levels of the input voltage and the load power. A 300 W prototype was studied in the laboratory to show the feasibility of the proposed hybrid PWM scheme with the closed-loop control system to switch between the two PWM schemes.

Step-Up Series Resonant DC–DC Converter with Bidirectional-Switch-Based Boost Rectifier for Wide Input Voltage Range Photovoltaic Applications

This paper proposes a high gain DC–DC converter based on the series resonant converter (SRC) for photovoltaic (PV) applications. This study considers low power applications, where the resonant inductance is usually relatively small to reduce the cost of the converter realization, which results in low-quality factor values. On the other hand, these SRCs can be controlled at a fixed switching frequency. The proposed topology utilizes a bidirectional switch (AC switch) to regulate the input voltage in a wide range. This study shows that the existing topology with a bidirectional switch has a limited input voltage regulation range. To avoid this issue, the resonant tank is rearranged in the proposed converter to the resonance capacitor before the bidirectional switch. By this rearrangement, the dependence of the DC voltage gain on the duty cycle is changed, so the proposed converter requires a smaller duty cycle than that of the existing counterpart at the same gain. Theoretical analysis shows that the input voltage regulation range is extended to the region of high DC voltage gain values at the maximum input current. Contrary to the existing counterpart, the proposed converter can be realized with a wide range of the resonant inductance values without compromising the input voltage regulation range. Nevertheless, the proposed converter maintains advantages of the SRC, such as zero voltage switching (ZVS) turn-on of the primary-side semiconductor switches. In addition, the output-side diodes are turned off at zero current. The proposed converter is analyzed and compared with the existing counterpart theoretically and experimentally. A 300 W experimental prototype is used to validate the theoretical analysis of the proposed converter. The peak efficiency of the converter is 96.5%.

Impedance Source-based Multilevel Inverter: A State-of-the-Art Review

Impedance source-based multilevel inverters are becoming popular for emerging power generation technologies such as fuel cells, photovoltaic, and wind turbines. It is one of the most promising power electronic interfaces for single stage DC/AC conversion with inherent buck-boost capability. Therefore, in this paper, an extensive review of emerging impedance source-based multilevel inverter (Z-MLI) topologies is presented. These topologies are developed by the combination of impedance source network and multilevel inverter (MLI) with the merits of high voltage gain, enhanced reliability due to shoot-through immunity, improved input voltage regulation, reduced filter size, and better quality of supply. Most of the recent Z-MLI topologies are based on quasi-Z-source network which operates with continuous input current. In order to identify a suitable topology, an exhaustive comparison is made with various configurations of Z-MLIs in terms of component count, boost gain, switching stress, and control complexity.

Dual-Voltage-Rectifier-Based Single-Phase AC–DC Converters With Dual DC Bus and Voltage-Sigma Architecture for Variable DC Output Applications

Novel single-phase ac–dc converters based on dual-voltage-rectifier (DV-rectifier) and voltage-sigma architecture is proposed in this paper. Dual dc-buses, i.e., a constant dc voltage bus and an adjustable dc voltage bus, are provided by the DV-rectifier. Voltages of the two dc-buses are stacked together on the output port through down-stream dc–dc transformers (DCXs). The dc output voltage is controlled by regulating the voltage of the adjustable dc-bus of the DV-rectifier. Therefore, voltage regulation is not required for the DCXs, which can always operate at their optimized operation point to ensure high efficiency. Since the voltage of the adjustable dc-bus is lower than the constant dc-bus, multi voltage-level characteristics can be obtained with the DV-rectifier, which is benefit for reduction of switching losses and improvement of conversion efficiency. In order to achieve current regulation of ac input port and voltage regulation of the two dc-buses simultaneously, multimode operation, and smooth mode transition strategies are proposed for the DV-rectifier. Operation principles, control strategies, and characteristics of the DV-rectifier and DCX-based ac–dc converter are analyzed in detail. Feasibility and effectiveness of the proposed solutions are verified with experimental results.

Multiphase Quasi-Z-Source DC–DC Converters for Residential Distributed Generation Systems

A multiphase quasi-Z-source (qZS) dc–dc converter was proposed for distributed energy generation applications. It contains single-switch qZS isolated dc–dc cells with a voltage doubler rectifier. These cells are connected in parallel at the input side and in series at the output side to increase the dc voltage gain. A dc voltage blocking capacitor in series with the isolation transformer results in resonance that could be utilized for soft-switching. Two design approaches were proposed: considering phase shedding dependent on the input voltage and without it. The former targets wide input voltage range applications, while the latter is better suited for high input current applications. An experimental prototype rated for 300 W was tested with two types of isolation transformers designed according to the two presented approaches. It could be used as a PV module integrated converter with wide input voltage regulation range. The experimental results prove efficiency improvement from the phase shedding. Resonance frequency variations caused by the utilization of the multilayer ceramic capacitors and their possible influence on switching losses are discussed.

Carrier‐overlapping PWM‐based hybrid current control strategy applied to two‐stage grid‐connected PV inverter

For a wide dc input voltage range of photovoltaic (PV) array, a two-stage grid-connected inverter that allows input voltage regulation is required. This study proposes a topology with time-sharing synchronous modulation in which energy transmission paths, wheeling branches and switching losses for high-frequency switches are optimised to achieve efficiency improvement. The small-signal model of proposed topology is analysed in detail. A hybrid current control strategy based on frequency-amplitude domain analysis is presented. To solve further transitional problem on boost–buck mode switching, the controller uses a carrier-overlapping pulse-width modulation (PWM)-based generator. Then, the effectiveness of the proposed topology and the control strategy under different experimental conditions are verified. Experimental results indicate hybrid current control strategy promotes current waveform quality and the burrs and oscillations in transition between buck mode and boost mode can be reduced.

IC Design and Measurement of an Inductorless 48 V DC/DC Converter in Low-Cost CMOS Technology Facing Harsh Environments

With reference to 48-V systems, used in electric and hybrid vehicles and for telecom and networking power supply, this paper presents the circuit/transistor-level design, implementation, and test of an inductorless dc/dc converter. Its architecture is a cascade of three switched-capacitor converters with step-up/down capabilities plus linear converters, working in parallel at the end of the cascade. It provides multiple regulated voltages, which are isolated from input failures. The design also includes on-chip control unit and a serial interface toward an external host. Experimental tests carried out on the chip, fabricated in 0.35- $\mu \text{m}$ CMOS technology, proves that the design is suitable to face harsh operating environments, including the 48-V automotive one. Compared with the state-of-art, the proposed design stands for its wide input voltage regulation range, load/line regulation, power supply rejection ratio, and low electromagnetic interference emissions.

High-Performance Quasi-Z-Source Series Resonant DC–DC Converter for Photovoltaic Module-Level Power Electronics Applications

This paper presents the high-performance quasi-Z-source series resonant dc-dc converter as a candidate topology for the photovoltaic module-level power electronics applications. The converter features a wide input voltage and load regulation range thanks to the multimode operation, i.e., when the shoot-through pulse width modulation and phase-shift modulation are combined in a single switching stage to realize the boost and buck operating modes, respectively. Our experiments confirmed that the proposed converter is capable of ensuring ripple-free 400 V output voltage within the sixfold variation of the input voltage (from 10 to 60 V). The converter prototype assembled achieved a maximum efficiency of 97.4%, which includes the auxiliary power and control system losses.

A Review of Galvanically Isolated Impedance-Source DC–DC Converters

Impedance-source converters, an emerging technology in electric energy conversion, overcome limitations of conventional solutions by the use of specific impedance-source networks. Focus of this paper is on the topologies of galvanically isolated impedance-source dc–dc converters. These converters are particularly appropriate for distributed generation systems with renewable or alternative energy sources, which require input voltage and load regulation in a wide range. We review here the basic topologies for researchers and engineers, and classify all the topologies of the impedance-source galvanically isolated dc–dc converters according to the element that transfers energy from the input to the output: a transformer, a coupled inductor, or their combination. This classification reveals advantages and disadvantages, as well as a wide space for further research. This paper also outlines the most promising research directions in this field.

Design and Implementation of LLC Resonant Converter for Photovoltaic Battery Charging Application

Photovoltaic power conditioning system (PVPCS) requires a high efficiency dc-dc converterstage capable of wide input voltage regulation and have the ease of maximum power point implementation for both stand alone photovoltaic system and grid-connected system. Galvanic isolation at the dc-dc stage can replace the isolation needed in the inverter stage and thus reduce the sizeof isolation transformer and increases overall system efficiency. This paper presents detailed analysis,design and implementation of a LLC resonant converter for photovoltaic battery charging application.The LLC resonant converter operate with zero voltage switching (ZVS) turn on and low current turnoff thus reducing switching losses. The experimental results are given to validate the operation andperformance of the converter.

Minimisations of total harmonic distortion in cascaded transformers multilevel inverter by modifying turn ratios of the transformers and input voltage regulation

A total harmonic distortion (THD) minimisation technique for cascaded transformers multilevel inverters is presented. In the proposed method, turn ratios of the transformers are optimised along with switching angles in order to minimise the THD of the inverter output voltage. Assuming turn ratios of the transformers as variables adds extra degrees of freedom to the equations. To obtain high-quality output voltage with an acceptable THD in lower modulation indices, the input voltage is also regulated. Genetic algorithm is applied to minimise THD as well as satisfy fundamental component of the output voltage. To verify the feasibility of the proposed approach, a nine-level cascaded transformer inverter prototype has been implemented. Simulation and experimental results show the effectiveness of the proposed technique in THD minimisation and generation of the desired fundamental component at output voltage.

Single Phase Single Stage AC/DC Converter with High Input Power Factor and Tight Output Voltage Regulation

A single stage single switch AC/DC converter is an integration of input current shaper and a DC/DC cell with a shared controller and one active switch. The converter is applicable for digital input power supply with high input power factor and tight output voltage regulation. The focus of the topology is to reduce the DC bus voltage at light load without compromising with input power factor and voltage regulation. The concept behind this topology is direct power transfer scheme. Using special configuration of DC/DC cell does reduction of DC bus voltage and DC/DC cell works on the principle of series charging and parallel discharging. The power output of this converter can go up to 200W.