DC Power Converter Research Articles

Design and implementation of piezoelectric energy harvesting circuit

PurposeThe purpose of this paper is to present the design of a piezoelectric vibration energy generator with a power conditioning circuit to power a wireless sensor node. Frequency and voltage characterization of the piezoelectric energy harvester is performed. A single-stage AC–DC power converter that integrates the rectification and boosting circuit is designed, simulated and implemented in hardware.Design/methodology/approachThe designed power conditioning circuit incorporates bridgeless boost rectification, a lithium ion battery as an energy storage unit and voltage regulation to extract maximum power from PZT-5H and to attain higher efficiency. The sensor node is modelled in active and sleep states on the basis of the power consumption. Dynamic modelling of the lithium ion battery with its state of charging and discharging is analysed.FindingsThe test result shows that the energy harvester produces a maximum power of 65.9 mW at the resonant frequency of 21.4 Hz. The designed circuit will operate even at a minimum input voltage of 0.5 V. The output from the harvester is rectified, boosted to a 7-V DC output and regulated to 3.3 V to the power C_Mote wireless sensor node. The conversion efficiency of the circuit is improved to 70.03 per cent with a reduced loss of 19.76 mW.Originality/valueThe performance of the energy harvester and the single-stage power conditioning circuit is analysed. Further, the design and implementation of the proposed circuit lead to an improved conversion efficiency of 70.03 per cent with a reduced loss of 19.76 mW. The vibration energy harvester is integrated with a power conditioning circuit to power a wireless sensor node C_Mote. The piezoelectric vibration energy harvester is implemented in real time to power C_Mote.

Multilevel Reduced Controlled Switches AC–DC Power Conversion Cells

This paper presents multilevel ac–dc single-phase power conversion cells for applications in which the regenerative operation is either not required or prohibited. The ac primary power source is a single phase from a permanent magnet generator or from an electrical grid. The cells are composed of two h-bridges in cascade: 1) an unidirectional high-voltage h-bridge with two controlled switches; and 2) two power diodes, processing the active power, and a low-voltage h-bridge with four controlled switches and a floating capacitor. These cells can be part of multiphase systems, in which it is required one cell for each phase. Some examples of application for three-phase systems are given, exploring different ways of connection between the single-phase cells. Simulation and experimental results regarding the proposed cells and conventional h-bridge based ac–dc converters are shown for validation and comparison purposes.

Condition Parameter Estimation for Photovoltaic Buck Converters Based on Adaptive Model Observers

DC–DC power converters such as buck converters are susceptible to degradation and failure due to operating under conditions of electrical stress and variable power sources in power conversion applications, such as electric vehicles and renewable energy. Some key components such as electrolytic capacitors degrade over time due to evaporation of the electrolyte. In this paper, a model-observer based scheme is proposed to monitor the states of Buck converters and to estimate their component parameters, such as capacitance and inductance. First, a diagnosis observer is proposed, and the generated residual vectors are applied for fault detection and isolation. Second, component condition parameters, such as capacitance and inductance are reconstructed using another novel observer with adaptive feedback law. Additionally, the observer structures and their theoretical performance are analyzed and proven. In contrast to existing reliability approaches applied in buck converters, the proposed scheme performs online-estimation for key parameters. Finally, buck converters in conventional dc–dc step-down and photovoltaic applications are investigated to test and validate the effectiveness of the proposed scheme in both simulation and laboratory experiments. Results demonstrate the feasibility, performance, and superiority of the proposed component parameter estimation scheme.

Permanent-Magnet Coupled Power Inductor for Multiphase DC–DC Power Converters

Using a coupled power inductor (CPI) in a multiphase dc–dc power converter instead of using multiple single-phase power inductors (PIs) reduces the inductor size and achieves better steady state and transient performances. To further reduce the inductor size and weight used in multiphase power converters, this paper presents a two-phase CPI that utilizes a permanent magnet (PM) to achieve almost doubled saturation current with the same size or equivalently achieve significant size and weight reduction. Operation principle of the presented permanent magnet coupled power inductor (PMCI) and required PM dimensions are derived and used as a design guide. The three-dimensional physical model of the PMCI is developed by using ANSYS/Maxwell software package to “visualize” the saturation current doubling. The fabricated PMCI design, with specifications of 24 A/phase, ∼4.25 μH/phase equivalent steady-state inductance, and ∼2.3 μH equivalent transient inductance, is tested in a 4–8 V two-phase dc–dc boost power converter with up to 50 A input current. Results show that compared to a conventional CPI design with the same size, weight, and inductance, the fabricated PMCI almost doubles the saturation current (from 13 to 24 A/phase). Compared to another CPI with a larger size but with even a smaller saturation current (18 A/phase), the core volume of the PMCI is reduced to 51.9% and the core weight is reduced to 51.2%. In addition, the PMCI achieves ∼76.3% core size and ∼73.4% core weight reductions compared to two separate single-phase PIs with the same steady-state inductance and similar saturation current (∼22 A) due to the dual flux cancelation effect from the coupling and PM realized by the presented PMCI structure.

Simple Resonance Circuit to Improve Electrical Power Conversion in a Two-Sided Planar Permanent Magnet Linear Generator for Wave Energy Converters

Developing simple, economic, and efficient electrical power conversion systems for wave energy converters (WECs) is an on-going research topic. This paper considers a simple resonance circuit to maximise the ac–dc power conversion of a permanent magnet linear generator (PMLG). To implement this circuit, the PMLG model parameters were obtained. In this paper, we developed a procedure for designing a two-sided planar PMLG considering the corresponding physical parameters. For this method, we set the basic parameters and calculated the derived parameters for the PMLG. The resonance circuit was composed of a three-phase rectifier with a shunt connection of capacitors between its diodes. The value of the capacitors was calculated using the resonance principle at a specific dominant frequency obtained from the location of the WEC installation. We compared the performance of the proposed resonance circuit with that of an existing resonance circuit. The proposed circuit generates more power, requires fewer components, and presents fewer harmonics. In addition, a higher-quality damping force was obtained when using the PMLG connected to the proposed resonance circuit and a resistive load.

Harmonic Analysis of Various SPWM Techniques for three Phase Diode Clamped Multi-Level Inverter in MATLAB/Simulink Environment

With advances in solid-state power electronic devices and microprocessors, various pulse-width-modulation (PWM) techniques have been developed for industrial applications. For example, PWM-based three-phase voltage source inverters (VSI) convert DC power to AC power with variable voltage magnitude and variable frequency. This paper discusses the advantages and drawbacks of three different PWM techniques: the sinusoidal PWM(SPWM) technique, the third-harmonic-injection PWM(THIPWM) technique, and the bus-clamped PWM (BCPWM) technique. These three methods are compared by discussing their ease of implementation and by analyzing the output harmonic spectra of various output voltages (poles voltages, line-to-neutral voltages, and line-to-line voltages) and their total harmonic distortion (THD).

Variable Speed Photovoltaic Water Pumping Using Affinity Laws

Photovoltaic (PV) power is most commonly used for water pumping applications. The DC output voltage of PV arrays is connected to a DC-DC converter using a maximum power point tracking (MPPT) controller to maximize their produced energy. Then, that converter is linked to a voltage source inverter (VSI) that converts DC power to AC power. Vector control is used to control the VSI fed three phase induction motor driving the water pump. The Affinity laws are used to change the pump characteristics by changing the pump speed, and consequently, the pump flow rate, head, and power will be varied. In this paper, the Affinity laws are adapted to achieve the pump hydraulic requirements while the power delivered to the pump motor remains unchanged by constructing new pump curves. A Matlab/Simulink model of the PV pumping system is observed over a wide range of weather and loading conditions.

Design of power integrated circuits in full AlGaN/GaN MIS‐HEMT configuration for power conversion

In order to examine the feasibility of full wide‐bandgap GaN‐based converters in aerospace power conversion applications, this paper proposes a monolithic DC–DC buck converter design with integrated high‐side gate driver, over‐current protection, and pulse‐width‐modulation feedback control circuits based on full AlGaN/GaN MIS‐HEMT configuration. After model calibration of the DC and transient behaviors with fabricated normally‐ON and normally‐OFF AlGaN/GaN MIS‐HEMT devices, the DC–DC buck converter is simulated. The circuit converts the input 100 V down to an adjustable range at 1 MHz switching frequency. The over‐current protection function can properly protect the converter at a preset over‐current threshold. The converter can respond to the load current and line input voltage fluctuations due to the integrated feedback control. These results illustrate the performance of proposed all‐GaN DC–DC power converter design.

Modelling and efficiency optimisation of UHF Dickson rectifiers

This paper presents a new time-efficient modelling approach for UHF Dickson rectifiers. Due to the very low computation time, the approach can provide a quick and effective alternative to the standard transient simulations. The presented approach results in better estimation of the generated DC voltage and power conversion efficiency compared with the similar works in the literature. For the first time, an accurate mathematical relationship, including the non-zero reverse current, is expressed for finding the open load voltage of the Dickson rectifier while covering the broad range of RF amplitudes. The model uses the relation between the peak forward current and the load current to develop an input-to-output formula. Unlike the previous works, the channel length modulation is taken into consideration for the first time making the proposed model ideal for UHF Dickson rectifiers implemented with submicron CMOS transistors. Moreover, the proposed model takes secondary effects, such as the body effect and short-channel effects into account resulting in a more accurate estimation of the generated output DC voltage. Using the presented approach, a Dickson rectifier working at 900 MHz is implemented in a 0.18 µm CMOS process. Good agreement between simulation results, predicted results, and measurement results is observed.

Analysis of wind driven self-excited induction generator supplying isolated DC loads

This paper presents the analysis, modelling and simulation of wind-driven self-excited induction generator (SEIG). The three-phase SEIG is driven by a variable-speed prime mover to represent a wind turbine. Also, the paper investigates the dynamic performance of the SEIG during start-up, increasing or decreasing the load or rotor speed. The value of the excitation capacitance required for the SEIG is calculated to give suitable saturation level to assure self-excitation and to avoid heavy saturation levels. Matching of the maximum power available from the wind turbine is performed through varying the load value. The effect of AC–DC power conversion on the generator is investigated. The system simulation is carried out using MATLAB/SIMULINK toolbox program.

A Bidirectional Nonisolated Multi-Input DC–DC Converter for Hybrid Energy Storage Systems in Electric Vehicles

To process the power in hybrid energy systems using a reduced part count, researchers have proposed several multiinput dc–dc power converter topologies to transfer power from different input voltage sources to the output. This paper proposes a novel bidirectional nonisolated multi-input converter (MIC) topology for hybrid systems to be used in electric vehicles composed of energy storage systems (ESSs) with different electrical characteristics. The proposed converter has the ability to control the power of ESSs by allowing active power sharing. The voltage levels of utilized ESSs can be higher or lower than the output voltage. The inductors of the converter are connected to a single switch; therefore, the converter requires only one extra active switch for each input, unlike its counterparts, hence resulting in reduced element count. The proposed MIC topology is compared with its counterparts concerning various parameters. It is analyzed in detail, and then, this analysis is validated by simulation and through a 1-kW prototype based on a battery/ultracapacitor hybrid ESS.

Three‐winding transformer based asymmetrical dual active bridge converter

A three-winding transformer based asymmetrical dual active bridge (TWT-ADAB) isolated dc–dc converter is proposed in this study. The converter comprises of three stages: primary, isolation, and secondary. The primary stage consists of an H-bridge converter, the isolation stage consists of a three-winding transformer with one primary and two secondary windings, and the secondary stage consists of a bridge converter having three legs and six active switches. The load current is shared equally by the secondary windings of the transformer resulting in reduced currents through switches of the secondary converter. Therefore, the turn-off losses of these switches get reduced. Further, zero voltage switching turn-on can be achieved for all switches of the TWT-ADAB converter to reduce the switching losses. A detailed analysis of the modelling and control of the proposed TWT-ADAB converter is presented. The theoretical analysis is verified using the simulation and experimental results. These demonstrated results show that the proposed TWT-ADAB converter offers wider ranges of the output voltages and powers and higher efficiency as compared with the existing dual bridge isolated dc–dc converters. Therefore, it can be an eminent structure for high-power isolated dc–dc power conversion applications.

A Multifunctional Grid-Tied Solar Energy Conversion System With ANF-Based Control Approach

This paper presents a two stage three-phase grid-interfaced solar photovoltaic (SPV) energy conversion system with an adaptive notch filter (ANF)-based control algorithm. The proposed SPV system is a multifunction grid-interfaced SPV energy conversion system, which along with the conversion of dc-power from SPV to ac mains is capable of reactive power compensation, harmonics currents elimination, and load balancing in a three-phase ac distribution system. Compared with multiple devices with different functionalities, a multifunction grid-interfaced SPV energy conversion system is capable of saving substantially capital investment, space, and maintenance cost on behalf of multifunctional features. The ANF successfully extracts a single sinusoid of a possibly nonstationary nature from harmonics corrupted load currents at point of common coupling. The control algorithm is adaptive with respect to the fundamental frequency of the system as compared with other methods, and provides instantaneous values of the fundamental signals. Simulation and experimental results verify the validity of the presented algorithm and confirms its desirable transient and steady state performances. The total harmonics distortion of grid currents is found well under IEEE-519 standard, even under nonlinear loads.

Adaptive Ramp Technique for Controlling Chaos and Subharmonic Oscillations in DC–DC Power Converters

We propose an adaptive ramp control strategy with self-tuning offset and amplitude, as a simple yet effective solution for controlling dc–dc power converters despite load and input voltage variations. It is shown that our control technique is able to suppress chaos and subharmonic oscillations for a wide range of input voltage and loads. Furthermore, a systematic methodology based on bifurcation diagrams for tuning the controller is proposed. Stability and performance analysis have been done together with a proper comparison of our technique, and the classical control strategies often used in the literature. Particularly, $V_{\text{\rm in}}$ feed-forward and adaptive slope compensation controllers have been considered for the buck and boost converters, respectively. Finally, the effectiveness of the control technique is validated for the buck converter via experimental setup.

Experimental Verification of a Front‐to‐Front (FTF) System Consisting of Two Modular Multilevel Cascade Converters Based on Double‐Star Chopper Cells

SUMMARYThis paper presents an experimental discussion on modular multilevel cascade converters based on double‐star chopper cells (MMCC‐DSCC). Hereinafter, a single MMCC‐DSCC is referred to simply as a “DSCC”. A couple of DSCCs are used to form a front‐to‐front (FTF) system capable of dc voltage matching and galvanic isolation between two dc grids. The FTF system can be considered as a dc–ac–dc power conversion system including an ac‐link high‐power transformer. The higher the ac‐link frequency, the smaller and lighter are the ac‐link transformer and dc capacitors. When the so‐called “phase‐shifted‐carrier PWM” is applied to the DSCC, theoretical analysis and computer simulation have confirmed that a ratio of the carrier frequency with respect to the ac‐link frequency can be reduced to 5/2. This paper designs, constructs, and tests a 400‐Vdc 10‐kW downscaled FTF system with a carrier frequency of 450 Hz and an ac‐link frequency of 180 Hz, where their ratio is 5/2. Experimental waveforms obtained from the downscaled system are compared with simulated ones obtained from a software package, PSCAD/EMTDC, under the same operating and circuit conditions. They agree well each other not only under steady states but also under transient states.

Interleaved Digital Power Factor Correction Based on the Sliding-Mode Approach

This study describes a digitally controlled power factor correction (PFC) system based on two interleaved boost converters operating with pulsewidth modulation (PWM). Both converters are independently controlled by an inner control loop based on a discrete-time sliding-mode (SM) approach that imposes loss-free resistor (LFR) behavior on each cell. The switching surface implements an average current-mode controller so that the power factor (PF) is high. The SM-based digital controller is designed to operate at a constant switching frequency so that the interleaving technique, which is recommended for ac–dc power conversion systems higher than 1 kW, can be readily applied. An outer loop regulates the output voltage by means of a discrete-time proportional–integral (PI) compensator directly obtained from a discrete-time small-signal model of the ideal sliding dynamics. The control law proposed has been validated using numerical simulations and experimental results in a 2-kW prototype.

Validation of a Three-Phase Cascaded Multilevel Inverter based on Newton Raphson (N.R.)

Objective: This paper discusses the configuration three-phase Cascaded H-Bridge Multilevel Inverter (CHBMLI) based on Newton Raphson (N.R.) method to produce obtain five-levels of output voltage by reduce Total Harmonic Distortion (THD). Method: The proposed method had been comprised of 5-level multilevel inverter, while the control system was based on the Newton Raphson (N.R.) method. Moreover, the main purpose of the research was to investigate the effectiveness of the proposed method by using NR for harmonic analysis in high voltage electrical distribution system. Besides, the optimization of the controller based on modulation indexes was employed in order to optimize and non-optimize the switching angle of the CHBMLI for different modulation indexes. Findings: An inverter is used to convert DC power generator from the DC supply into AC power. The five-level inverter resulting in increased voltage levels of the output waveform. As the levels of output waveform increase, the percentage of THD reduced and switching losses decreased to improves power quality have been done compared with conventional three phase Dc supply connected PWM cascaded H-bridge multilevel inverter. Based on Newton Raphson (N.R.) five-level of output voltage is produced by the inverter zero, +1/2Vdc, +Vdc, -1/2Vdc and -Vdc. Improvements: Apart from that, the proposed scheme was modelled with MATLAB software and the Simulation results were verified via hardware experimental by using Digital Signal Processing (DSP) TMS320F2812. The experimental results showed that the proposed method had been effective in verifying the NR control in terms of Total Harmonic Distortion (THD).

Optimal PFC corrector of single stage power converter using BC tuned PID controller

In this paper, Bee Colony (BC) algorithm based tuning of the proportional, integral and derivative (PID) controller is proposed. The novelty of the proposed method is enhanced searching ability, reliability and suitable for complex problems. Here, the proposed method is used to optimize the proport ional, integral and derivative gains of the PID controller based on the output power variation from the input power. With the optimized gains, PID controller determines the control output to reduce the error between the actual and reference value of the instantaneous input power. This instantaneous input reference is computed with the aid of Radial Basis Function Network (RBFN). In the presented work, the topology of the AC to DC power converter is modelled and controlled with BC optimized PID controller. The performance of the proposed BC-PID controller for AC to DC converter is analyzed in terms of power factor correction and efficiency. The validation of the proposed control algorithm is performed on MATLAB/Simulink working platform and the effectiveness of the proposed method is analyzed by using the comparison analysis with the existing techniques.

Novel Isolated Multilevel DC–DC Power Converter

An isolated multilevel dc–dc power converter is proposed in this paper. The proposed isolated multilevel dc–dc power converter consists of an isolated power converter, a series/parallel switching circuit, and an output L–C filter. The isolated power converter is composed of a half-bridge inverter, a three-winding transformer, and two full-bridge rectifiers. The half-bridge inverter is switched in constant duty to generate two output dc voltages through two secondary windings of the three-winding transformer and two full-bridge rectifiers, respectively. The series/parallel switching circuit is used to control the two output dc voltages of the isolated power converter connected in series or in parallel, to control the output voltage of isolated multilevel dc–dc power converter. To verify the performance of the proposed isolated multilevel dc–dc power converter, a prototype is developed and tested. The experimental results show that the proposed isolated multilevel dc–dc power converter has the expected performance.

Analytical Switching Loss Model for Superjunction MOSFET With Capacitive Nonlinearities and Displacement Currents for DC–DC Power Converters

A new analytical model is presented in this study to predict power losses and waveforms of high-voltage silicon superjunction MOSFET during hard-switching operation. This model depends on datasheet parameters of the semiconductors, as well as the parasitics obtained from the printed circuit board characterization. It is important to note that it also includes original features accounting for strong capacitive nonlinearities and displacement currents. Moreover, these features demand unusual extraction of electrical characteristics from regular datasheets. A detailed analysis on how to obtain this electrical characteristic is included in this study. Finally, the high accuracy of the model is validated with experimental measurements in a double-pulse buck converter setup by using commercial SJ MOSFET, as well as advanced device prototypes under development.