Hybrid PWM Research Articles

Current Source Mode Bidirectional DC/DC Converter With Multiple-Level Output Conversion Ratios Based on the Hybrid PWM Control of the Switched-Capacitor Structure

The current source (CS) mode bidirectional dc/dc converter (Bi-DCC) with multiple-level output current ratios is presented. Using the hybrid pulsewidth modulation (PWM) method to control the conversion selection mechanism realizes the multiple-level conversion options in both bidirectional energy flows. It is suitable for future all-electrical driving and braking systems in electric vehicles, supplying power to adjust the motor dynamics control during vehicle driving and collecting the energy generated during braking, especially on different road conditions. Moreover, the function that one single converter provides multiple-level conversion ratios, makes the design highly suitable for smart manufacturing as it can simplify the design by type and configuration variations. This design mainly focuses on dealing with applications directly powered by the CS, for example, the connection of photovoltaic (PV) units, CS mode motor controller, current-based power systems, and CS mode light-emitting diodes. A 300 W prototype with a conversion selection structure (CSS), which contains three switching orders and ten levels of current options, has been established. It validated multiple conversion ratio selections for step-down and step-up operation modes, high stability, and low power cost through the simulation and experiment results.

Performance Analysis of Diode-Assisted Switched LC qZSI Network-Based Multioutput Series-Parallel Topologies in Microgrid Application

In this paper, two (series and parallel versions) quasi Z source inverter (qZSI)-based multioutput series-parallel topologies capable of supplying multiple three-phase AC and single boost DC outputs simultaneously are presented. The proposed parallel version topology can supply n number of AC outputs along with one boost DC with constant voltage and variable current. Similarly, the series version topology can give n number of AC including one boost DC output with constant current and variable voltage. The outputs of the proposed topologies can feed directly to DC/AC microgrids and multiple residential loads simultaneously without using any extra adapter/regulator and thereby avoiding local power conversion to meet the load demand. A hybrid pulse width modulation technique with constant frequency is used to operate the proposed topologies. The performance of the proposed topologies is verified by developing the prototypes of 2.18 kW (for parallel version) and 2.02 kW (for series version) for two three-phase AC outputs and one boost DC output. The developed prototypes show measured efficiency of 90.01% for the parallel and 89.95% for the series version topology.

Neural Network and Fuzzy Control Based 11-Level Cascaded Inverter Operation

This paper presents a combined control and modulation technique to enhance the power quality (PQ) and power reliability (PR) of a hybrid energy system (HES) through a single-phase 11-level cascaded H-bridge inverter (11-CHBI). The controller and inverter specifically regulate the HES and meet the load demand. To track optimum power, a Modified Perturb and Observe (MP&O) technique is used for HES. Ultra-capacitor (UCAP) based energy storage device and a novel current control strategy are proposed to provide additional active power support during both voltage sag and swell conditions. For an improved PQ and PR, a two-way current control strategy such as the main controller (MC) and auxiliary controller (AC) is suggested for the 11-CHBI operation. MC is used to regulate the active current component through the fuzzy controller (FC), and AC is used to regulate the dc-link voltage of CHBI through a neural network-based PI controller (ANN-PI). By tracking the reference signals from MC and AC, a novel hybrid pulse width modulation (HPWM) technique is proposed for the 11-CHBI operation. To justify and analyze the MATLAB/Simulink software-based designed model, the robust controller performance is tested through numerous steady-state and dynamic state case studies.

Hybrid PWM Techniques for a DCM-232 Three-Phase Transformerless Inverter with Reduced Leakage Ground Current.

Pulse Width Modulation (PWM) strategies are crucial for controlling DC–AC power converters. In particular, transformerless inverters require specific PWM techniques to improve efficiency and to deal with leakage ground current issues. In this paper, three hybrid PWM methods are proposed for a DCM-232 three-phase topology. These methods are based on the concepts of carrier-based PWM and space vector modulation. Calculations of time intervals for active and null vectors are performed in a conventional way, and the resulting waveforms are compared with a carrier signal. The digital signals obtained are processed using Boolean functions, generating ten signals to control the DCM-232 three-phase inverter. The performance of the three proposed PWM methods is evaluated considering the reduction in leakage ground current and efficiency. The proposed modulation techniques have relevant performances complying with international standards, which make them suitable for transformerless three-phase photovoltaic (PV) inverter markets. To validate the proposed hybrid PWM strategies, numerical simulations and experimental tests were performed.

Space Vector-Based Hybrid Pulse Width Modulation for Voltage Source Inverters Using Novel Euclidean Distance Mapping Technique

In this article, a novel Euclidean distance mapping (EDM) technique for space vector pulse width modulated (SVPWM) voltage source inverter (VSI) is presented. The EDM technique processes space vector diagram (SVD) as an image, which simplifies execution of SVPWM. In the proposed technique, Euclidean distance calculation between all eight switching vectors and the tip of the revolving reference voltage vector for every subcycle is carried out. The identification of nearest three voltage vectors (NTV) and switching sequence designs are done on the basis of these Euclidean distances. The EDM-SVPWM technique achieves improvement in the inverter performance in the context of the factors like stator flux ripple over a subcycle, distortion factor (DF), total harmonics distortion (THD) of line voltage, and line current ripple of the inverter. The performance of EDM-SVPWM technique is verified analytically and confirmed experimentally by hardware implementation over the wide range of fundamental frequencies and modulation indices.

Air‐gap flux‐oriented vector control of dual stator induction generator used in wind energy conversion system with novel 13‐zone time optimized space vector‐based hybrid bus clamping PWM

This work presents a novel speed sensor less air-gap flux-oriented vector control of dual stator induction generator (DSIG) used for grid connected, variable speed wind energy generation system. The DSIG consists of two stator windings electrically separated by an angle of 30° with dissimilar pole numbers, which are in the ratio of 1:3. This arrangement offers reduced magnetic core saturation and less harmonics in stator currents, which results into reduced stator winding losses. Moreover, presence of two stator windings makes DSIG suitable to be used in high power application. In conventional rotor-flux-oriented control, the rotor flux is oriented along the d-axis of the rotor winding. But the rotor flux is not easily accessible. Air-gap flux-oriented vector control (AGFOVC) is advantageous as compared to conventional vector control because the air-gap flux is easily accessible and does not require any special arrangement for the measurement of variables. Moreover incorporation of this novel speed sensor less air-gap flux-oriented vector control also eliminates the use of speed encoder as the rotor speed is estimated from the machine terminal variables. Elimination of speed encoder not only reduces the cost of the overall system but also nullifies the error due to mismeasurement of speed and enhances control flexibility and robustness. As a result of which robustness of the system increases. Here, two separate converters are used for the two stator windings of the machine. And the converter switching's are being performed by space vector-based novel dwell time optimized 13-zone hybrid PWM. This special PWM results in better harmonic performance, reduced torque pulsation, and minimal switching loss. The simulation of the overall system is performed in MATLAB environment and the simulated results are validated experimentally using dSPACE controller board DS1104. Close proximity in simulated and experimental waveforms justifies the effectiveness of the proposed work.

Symmetrical Cascaded Switched-Capacitor Multilevel Inverter Based on Hybrid Pulse Width Modulation

Multilevel inverters have been widely used in various industrial applications such as renewable energy generation and electric vehicles. An improved circuit of symmetrical cascaded switched-capacitor multilevel inverter is proposed so that the reactive power is absorbed by its power supply instead of capacitors. Then, a special hybrid pulse width modulation strategy combing level-shifted pulse width modulation (LS-PWM) and phase-shifted pulse width modulation (PS-PWM) was developed for the inverter. With this modulation algorithm, the power between cascaded units is automatically balanced, and the voltage of the capacitor in each unit is also automatically balanced to the dc input voltage. In addition, the optimized capacitor voltage ripple makes it possible to use a smaller capacitor to produce a better output voltage waveform. Theoretical analysis, simulation and experimental results show that the equivalent switching frequency of the cascaded multilevel inverter is twice the original frequency so that the output voltage harmonics are only distributed near even multiples of the carrier frequency.

An Optimized Hybrid SOVM Modulation Based on MDAVT for OEWIM

This paper presents a new optimized hybrid space opposite vectors modulation (SOVM) strategy based on the multiple division of active vector time (MDAVT) for a dual inverter fed open end winding induction motor (OEWIM) to reduce the common mode voltage (CMV) as well as line current harmonic distortion. Ordinarily, to drive all ac drives at variable voltage and frequencies voltage source inverters (VSIs) need to be employed. In this regard various PWM strategies came into existence to provide gating signals to VSIs. Mostly all the PWM converters yields CMV across the load terminals which in turn results common mode currents. These common mode currents lead to the electromagnetic interference and explicitly responsible for the failure of bearings in case of motor loads. In order to reduce this CMV in this paper, a SOVM strategy is adapted. The concept of an optimized MDAVT is also introduced along with the SOVM to obtain the less current ripple. Finally these adaptions lead to an optimized hybrid PWM strategy and is employed for dual two level inverter fed OEWIM. In the present work in order to evaluate the optimistic performance of proposed switching strategy for OEWIM MATLAB software is chosen. And to validate the proposed strategy experimentally dSPACE 1104 is employed for digital implementation of PWM signals. Finally the superiority of the proposed PWM scheme in terms of CMV is presented with the detailed analysis. Whereas, the superiority in terms of current THD is shown with the help of the simulation and experimental results.

A Hybrid PWM Scheme for Stator Loss Reduction of Two Parallel Interleaved Inverter-Fed PMSM Drive with a Minimized Switching Loss

A Hybrid PWM Scheme for Stator Loss Reduction of Two Parallel Interleaved Inverter-Fed PMSM Drive with a Minimized Switching Loss

H5-ZVR Single-Phase Grid-Tied Inverters for Photovoltaic Application

The majority of companies are shifting to renewable energy sources as non-renewable fuels are increasingly depleting. Solar energy is a dependable form of green energy. The solar energy after converting to AC through an inverter it is possible to inject into the grid to support distributed power generation system. Transformerless grid-tied inverters have become popular due to their lightweight and reduced cost. The leakage current does exist in this kind of inverter that deteriorate the performance of the inverter. This paper presents a novel H5-ZVR, H5-ZVRD and H5-ZVRS topologies to address the leakage current issue. These inverters take the benefit of hybrid technology, where H5 inverters are integrated with HB-ZVR topologies. To operate the inverter at its highest performance an appropriate hybrid pulse width modulation is also presented. The inverters are simulated in MATLAB to verify the operation and it is found that the leakage current of the inverters is considerably reduced as compared to HB-ZVR topologies. The leakage current of H5-ZVR, H5-ZVRD and H5-ZVRS are found to be 10 mA, 7.3 mA and 7.3 mA respectively and THD of these modules are 1.03%, 0.91% and 0.91% respectively. Also, the topologies present good common mode and differential mode characteristics.

Vector decomposition and model predictive control based hybrid PWM algorithm for 5L-ANPC inverter

ABSTRACT This paper proposes a novel modulation algorithm based on vector decomposition and model predictive control for 5-level active neutral-point-clamped (5 L-ANPC) inverter. Firstly, the control of 5-level inverter is transformed into that of 3-level inverter by vector decomposition, which reduces the control complexity. Secondly, based on the framework of 3-level inverter, the optimal zero sequence voltage and switch state sequence are selected by multi-objective optimisation of model predictive control to balance the neutral point voltage and floating capacitors voltages simultaneously. Finally, according to the optimal choice, single-carrier comparison is used to generate the drive signal, which does not require traditional dual-carrier or vector synthesis, and is relatively easy to implement. Experimental results verify the validity of the method.

Efficiency optimization strategy of LLC resonant converter based on Hybrid PWM and PFM digital control mode

There is a problem that the overall efficiency of LLC resonant converter decreases due to large switching loss under light load, in order to solve it, an efficiency optimization strategy based on hybrid PWM and PFM digital control mode was proposed to improve the efficiency of LLC Resonant Converter in the full load range. In order to adapt to different loads, Boost LLC converter circuit topology was proposed. The former Boost circuit was controlled by pulse width modulation (PWM), and the latter LLC was controlled by pulse frequency modulation (PFM). Pulse width modulation (PWM) control of the front Boost circuit can improve the bus voltage of the rear LLC circuit and adapt to different loads. Under the pulse frequency modulation (PFM), the efficiency of the rear LLC resonant converter under light load can be further improved by adjusting the resonant frequency. The experimental results showed that the proposed digital control efficiency optimization method could enable the Boost LLC converter to achieve high efficiency in the whole load range, and the overall conversion efficiency was not less than 94%.

An Optimized Hybrid PWM Strategy for Five Level NPC VSI With Unequal DC-Links in a PV System

This article presents an optimized hybrid pulsewidth modulation (PWM) strategy for five-level neutral point clamped (5L-NPC) inverter with unequal dc-link capacitor voltages fed by differential power processing (DPP)-based photovoltaic (PV) system. The generation of balanced output from the 5L-NPC inverter with the unequal dc-link capacitor voltages becomes necessary in a PV system. The unequal dc-link capacitor voltages cause low order harmonics in inverter output voltage. A hybrid PWM strategy combining the advantages of space-vector PWM (SVPWM) and the nearest level modulation (NLM) methods is proposed to address the issues associated with unequal dc-link capacitor voltages in a five-level NPC inverter. The proposed hybrid PWM is optimized to achieve balanced output voltage with less total harmonic distortion at fundamental frequency. In-depth theoretical analysis of sector identification algorithm and dwell time computation for the proposed optimized hybrid PWM method are described. Simulation and experimental results are illustrated for several combinations of unequal dc-link capacitor voltages to validate the functionality and performance of the proposed optimized hybrid PWM method.

Analysis of a Wide Voltage Hybrid Soft Switching Converter

A hybrid PWM converter is proposed and investigated to realize the benefits of wide zero-voltage switching (ZVS) operation, wide voltage input operation, and low circulating current for direct current (DC) wind power conversion and solar PV power conversion applications. Compared to the drawbacks of high freewheeling current and hard switching operation of active devices at the lagging-leg of conventional full bridge PWM converter, a three-leg PWM converter is studied to have wide input-voltage operation (120–600 V). For low input-voltage condition (120–270 V), two-leg full bridge converter with lower transformer turns ratio is activated to control load voltage. For high input-voltage case (270–600 V), PWM converter with higher transformer turns ratio is operated to regulate load voltage. The LLC resonant converter is connecting to the lagging-leg switches in order to achieve wide load range of soft switching turn-on operation. The high conduction losses at the freewheeling state on conventional full bridge converter are overcome by connecting the output voltage of resonant converter to the output rectified terminal of full bridge converter. Hence, a 5:1 (600–120 V) hybrid converter is realized to have less circulating current loss, wide input-voltage operation and wide soft switching characteristics. An 800 W prototype is set up and tested to validate the converter effectiveness.

A Voltage Balancing Scheme for Modular Multilevel Converter Based on Charge Variation in Each Cycle

This article presents a voltage balancing scheme for a modular multilevel converter (MMC) based on capacitor charge variation in each fundamental cycle. An in-depth theoretical analysis of stored charge variation for the concept is described. A new hybrid pulsewidth modulation (PWM) sequence is proposed based on a rotation strategy to achieve capacitor voltage balancing without sensing the capacitor voltages or arm currents. The rotation strategy provides the freedom of finding the best possible sequence to achieve capacitor voltage balancing. This reduces hardware, software burden and overall cost of the design implementation. The functionality and performance of the balancing strategy with new hybrid PWM sequence are carried out over wide range of modulation index (M) for three-phase five-level MMC in MATLAB/Simulink. A hardware prototype of single-phase five-level MMC is designed for experimental validation. The proposed hybrid PWM sequence is implemented on an Altera/Cyclone I series (EP1C12Q240C8N) field-programmable gate array using alternate phase opposition disposition PWM method. Simulation and experimental results are presented.

Self-Balanced Switched-Capacitor Thirteen-Level Inverters With Reduced Capacitors Count

This letter describes two improved 13-level inverters based on switched-capacitor. Compared with their original structure, which is published recently, one less high-voltage capacitor is required in the proposed inverters and the blocking voltage of their inverting half-bridge is reduced by half. In addition, the new inverters inherit various advantages of the original structure, such as a high boost factor of 6, self-balanced capacitor voltages, and reduced voltage ripples. Circuit description, operation principle, hybrid PWM modulation, and capacitor voltage ripples are analyzed and the feasibility of the proposed inverters is finally verified by experimental results.

Ground Current Suppression for Grid Connected Transformerless Photovoltaic Inverter with Filter Capacitor

The full-bridge inverter with unipolar PWM (UPWM) or hybrid PWM (HPWM) has higher efficiency and lower filtering requirement. However, when it is used for grid-connected transformerless photovoltaic system, the ground current may be high due to the parasitic capacitors and high frequency common-mode voltage. In this paper, the output filter capacitor is proposed to suppress the ground current. In this method, the output filter capacitor is parallelled with the parasitic capacitors. The analytical method is established to calculate the ground current. The effect of the novel method under different modulation technique is studied. Efficiency estimation is done for comparison of different topologies. Finally, the validity of the proposed method is verified by simulation and experimental results.

Design and implementation of solar docking station for smartphones/laptops

Presently the innovation has developed to a momentous level that a student’s learning process happens through smart phones and laptops called Mobile e-leaning. Experiencing the outdoor and open spaces can benefit a student’s emotional, social and physical improvement. The difficulty in extending multiple power chords in open spaces and in locations where the access to electrical power outlet is arduous has prompted the idea of photovoltaic based solar charging/Docking station for charging mobile phones and Laptops. A remarkable impedance source inverter is implemented for the solar docking station and its performance is enhanced by implementing hybrid pulse width modulation technique. The components such as solar panels, rechargeable batteries, and charge controller pertaining to the installation of solar docking station are designed by analysing the load applied through AC and USB charging ports and the backup time requirement. A solar docking station is successfully installed in the college campus with the proposed inverter for charging the laptops and mobile phones.

Hybrid PWM modulated cross switched asymmetrical multilevel inverter with reduced number of conducting devices

Hybrid PWM modulated cross switched asymmetrical multilevel inverter with reduced number of conducting devices

An Overview and Comprehensive Comparative Evaluation of Constant-Frequency Voltage Buck Control Methods for Series Resonant DC–DC Converters

The paper focuses on galvanically isolated series-resonant dc-dc converters with a low quality factor of a magnetically integrated resonant tank. These converters can be controlled at a constant switching frequency to achieve the input voltage buck regulation. The paper compares various buck control methods, such as conventional pulse-width modulation, hybrid pulse-width modulation, shifted pulse-width modulation, hybrid shifted pulse-width modulation, improved shifted pulse-width modulation, asymmetrical pulse-width modulation, pulse-width modulation, and hybrid pulse-width modulation applied to the series-resonant dc-dc converter. The study considers step-up implementation of the series-resonant dc-dc converter topology with the voltage doubler rectifier, which makes it suitable as a front-end dc-dc converter for the integration of renewable energy sources in dc microgrids. The voltage buck control methods considered were compared analytically in terms of the cumulative power losses calculated theoretically. The theoretical results were compared with the experimental measurements to confirm the calculations and benchmark the voltage buck control methods. The experimental validation was performed using a 250 W prototype that demonstrated the hybrid PSM achieves the best performance. The experimental results were found in good agreement with analytically predicted values of the power loss.