Pulse Width Modulation Converter Research Articles

Design and Implementation of Robust H∞ Control for Improving Disturbance Rejection of Grid-Connected Three-Phase PWM Rectifiers

In response to the high performance requirements of pulse width modulation (PWM) converters in grid-connected power systems, H-Infinity (H∞) control has attracted significant research interest due to its robustness against parameter variations and external disturbances. In this work, an advanced robust H∞ control is proposed for a grid-connected three-phase PWM rectifier. A two-level control strategy is adopted, where cascaded H∞ controllers are designed to simultaneously regulate the DC bus voltage and input currents even under load disturbances and non-ideal grid conditions. As a result, unit power factor, stable DC bus voltage, and sinusoidal input currents with lower harmonics can be accurately achieved. The design methodology and stability of the proposed controller are verified through a comprehensive analysis. Simulation tests and experimental implementation on a dSPACE 1103 board demonstrate that the proposed control scheme can effectively enhance disturbance rejection performance under various operating conditions.

Neural Network Quadrature Signal Generator-Based Virtual Flux Estimation for Predictive Control of PWM Converters

In this paper, a frequency-adaptive neural network-based virtual flux (FANN-VF) estimator is developed for sensorless control of a pulse-width modulation converter under unbalanced and distorted grid conditions. This method exploits two parallel FANNs configured as quadrature signal generators. The VF fundamental positive and negative sequence components (PNSCs) are inherently separated in the estimator without employing any cascaded filters. A frequency-locked loop is introduced to accurately track the frequency variations. The estimated VF PNSCs are directly exploited to compute the power references in VF-based predictive direct power control scheme. The developed strategy ensures constant active power and sinusoidal current waveforms under nonideal grid conditions. Simulation and experimental tests are performed to verify the effectiveness of the proposed method.

Active Fault-Tolerant and Attack-Resilient Control for a Renewable Microgrid Against Power-Loss Faults and Data Integrity Attacks.

The next-generation power grid evolves from the development of fundamental cyber-physical energy systems called smart microgrids. In order to improve the reliability, safety, and security of smart microgrids and achieve a more cost-effective operation, innovative approaches for physical fault diagnosis and fault-tolerant control (FTC) as well as intrusion detection and attack-resilient control (ARC) should be investigated. Given that, this article considers a smart hybrid renewable-based microgrid with different types of distributed generation units, including solar photovoltaic (PV) array, wind turbines, and battery energy storage system. Novel active FTC and ARC strategies are designed for pulse-width modulation (PWM) converters at microgrid level. The proposed fault-tolerant controller is based on an optimal fuzzy gain-scheduling technique that is used to accommodate the adverse impacts of PV power-loss faults. Also, the proposed attack-resilient controller relies on the estimated values of sensor measurements during the occurrence of data integrity cyber-attacks. To access and evaluate the microgrid's real-time health status, both FTC and ARC strategies employ an integrated model-based intrusion detection and fault diagnosis (IDFD) system that is designed using a fuzzy modeling and identification technique. Finally, the effectiveness of the proposed solutions is demonstrated via a series of simulations in MATLAB/Simulink using an advanced microgrid benchmark.

Design of a novel control hysteresis algorithm for photovoltaic systems for harmonic compensation

Solar photovoltaic (PV) system design and integration with an existing AC grid is growing very fast in recent years and used by many of them as they are pollution-free, structure is limited and maintenance free. From the factors considering, the performance of PV system depends upon the inverter output voltage tested for linear, non-linear, with harmonic, and without harmonic loads. Generated due to the nonlinear loads. Better inverter control techniques are developed to maintain grid power quality. This article discusses the analysis and comparison of pulse width modulation (PWM) converters with unique and state of the art nonlinear control schemes and various modulation approaches. The primary objective of this research is controlling an active filtering hysteresis PWM converter with no sensors. A simple structure with hysteresis current control method total harmonic distortion (THD) is lower when compared with the sinusoidal pulse width modulation (SPWM) method. The said claims are supported by employing computer simulations using MATLAB/Simulink and different control approaches, such as proportional plus integral and artificial neural network controllers.

Coupled-Inductor-Based Bidirectional Resonant Converter With Reduced Component Count and Load-Independent Voltage Gain

The bidirectional DC/DC converter (BDC) is a critical part to interface the DC-bus with energy storage system (ESS) in DC microgrid. This paper proposes a coupled-inductor based bidirectional resonant converter with center-aligned pulse width modulation (PWM) modulation method and reduced component count. The structure of dual half-bridges with coupled inductor makes the current analysis more complex than the full-bridge PWM resonant converter. Hence, a method of performance analysis based on the symmetrical pi model is proposed and the corresponding parameter design process is introduced. In addition, fixed switching frequency operation, load-independent voltage gain, full-load range zero-voltage-switching (ZVS), automatic bidirectional power transfer and bidirectional power limitation can be realized in the proposed PWM converter. An experimental prototype with rated power of 1000W is built to demonstrate the operation and performance of the proposed converter.

Nonisolated High Step-Up DC–DC Converters: Comparative Review and Metrics Applicability

Due to the extensive role of non-isolated high step-up DC-DC converters (NHSDC)s in industrial applications and academic research, many of these pulse width modulation converters have been presented in recent years. For each of these NHSDCs, some claims are introduced to verify its capabilities and features, which has been investigated in some review papers with different frameworks. Dissimilar to previous review papers, which have focused on the classification and derivation of voltage boosting techniques, this paper aims to evaluate the converters from various topological and operational points of view, and determine the superiority of each technique and converter according to applications. Some of these metrics are voltage gain, stresses, ripple, cost, power density, weight, size, control complexity and components count which lead to a comprehensive comparative study. Then, as the main purpose of this paper, effectiveness of these metrics is assessed to show how well they can lead us to the fair comparison results. Moreover, some new figures of merit are proposed in this paper to provide a helpful guideline in power electronic converters comparison studies. Finally, the feasibility discussion of single- and multi-objective figures of merit is followed by general practical conclusion and outlook about the NHSDC structures.

Dynamic Performance Improvement of Wound Rotor Synchronous Starter/Generator System Based on PWM Rectifier

This paper proposes an active field current tracking (AFCT) control strategy for pulse width modulation (PWM) rectifier, which can remarkably enhance the system’s dynamic performance of wound rotor synchronous starter/generator (WRSSG) system when the load changes. WRSSG system uses a PWM converter in the aero-engine starting process and can reuse the power circuit as a PWM rectifier for high-voltage direct current (HVDC) power generation, thus simplifying the system structure, volume, and weight. The mathematic model of WRSSG system with PWM rectifier is introduced. Based on the system model, the PI controller of armature current loop is designed. The nonlinear PI controller of excitation voltage loop is also illustrated. A 15kW WRSSG system based on PWM rectifier is implemented. The AFCT control strategy and its high dynamic performance are verified by experiments. The simple system structure and distinguished dynamic performance of PWM rectifier with AFCT control can make the WRSSG system more competitive in aircraft applications.

Suppression Strategy of Differential Mode Circulating Current in Parallel Three-Phase PWM Converter

Parallel three-phase pulse width modulation (PWM) converter is a useful technique for increasing the capacity of a power system, but it also introduces the issue of circulating current, which can cause an increase in the loss of power electronics (PE) switches and even lead to over-current, which can affect the overall performance of the system. In this paper, a strategy is proposed for suppressing the differential mode circulating current (DMCC) in each phase of the parallel converter, which is less dependent on system parameters. Based on the mathematical model of the parallel converter, the relationship between the PWM duty cycle and circulating current is derived, which provides a basis for adjusting the switching operation of PE switches. This method requires no additional hardware and is simple to implement with a fast dynamic response. The simulation results verify the correctness of the theoretical analysis, and it can effectively achieve the balanced suppression of DMCC in each phase, which indicates that the method is suitable for the application scenario of parallel current sharing of multiple converters.

A new lossless passive snubber with simple structure for pulse width modulation DC-DC converters

A new lossless passive snubber for pulse width modulation converters is introduced in this paper. This snubber is established zero current switching condition for main switch in the converters for turning on distance. This snubber does not impose any additional current stress on the switch. The snubber can be applied to all single-switch DC-DC converters. A boost converter with the proposed snubber is analyzed and to verify theoretical analysis a 200 W sample is implemented and tested, also the experimental results are presented. In order to investigate the effect of snubber circuit in the converter in terms of efficiency, the boost converter with the proposed snubber has been compared in terms of efficiency with the conventional boost converter and the results show that the efficiency has increased by about 7% despite the snubber.

Averaged Behavior Model of Current-Mode Buck Converters for Transient Power Noise Analysis

Accurate evaluation and simulation of power noise is critical in the development of modern electronic devices. However, the widely used target impedance fails to predict the low-frequency noise generated in a device due to the existence of the dc–dc converter, whose output impedance can change under different loading conditions. A physical circuit model is then desired to replicate the behavior of a voltage regulator module, and the average technique is an efficient method to estimate the noise of a pulsewidth-modulated (PWM) converter. With the emergence of converters with adaptive on-time (AOT) controllers, more complex averaging methods are required, but none of them supports transient simulation. A general, efficient, and accurate modeling technique is presented in this article, whose framework supports both current-mode PWM and AOT controllers. In addition, a novel two-step parameter extraction method is proposed, which can be used to evaluate the equivalent values of internal feedback parameters of an encrypted simulation model or from measurement. The modeling method is validated by both simulation and measurement.

Parallel Distributed Compensation for Three-Phase pulse width modulation converter

In applications such as industrial drive systems and power supply systems, the use of a three-phase voltage-source Rectifier pulse width modulation converter is becoming increasingly common. Examples of these types of applications include: Power Factor Corrections and the reduction of harmonics. The critical control requirements of an application involving a three-phase voltage-source Rectifier pulse width modulation converter are to achieve a unity power factor and to regulate the dc voltage. The unity power factor guarantees the highest possible efficiency, while the dc voltage regulation guarantees that the converter will operate as desired. In this study, a novel control method for stabilizing a Rectifier-Inverter pulse width modulation converter is designed and simulated to reach higher levels of stability while also improving dynamic performances. In the first step, the nonlinear equation system of the converter is transformed into a polytopic form. This is done with the help of the sector nonlinearity transformation. After that, a Takagi-Sugeno fuzzy controller that uses the parallel distributed compensation operating concept is applied. The design of the control system takes into account practical control requirements, such as a fast voltage tracking strategy and line-currents regulation. In order to obtain the controller gain, a series of linear matrix inequalities must be resolved. Simulations performed using Matlab/Simulink make it abundantly evident that the proposed method possesses excellent performance in terms of both voltage tracking control and unity power factor regulation.

Single-phase energy-fed AC electronic load based on DQ current decoupling

The single-phase pulse width modulation (PWM) converter is the main research object to realize single-phase AC electronic load. To achieve high-quality energy feedback, this paper studies the topology of the PWM rectifier, the mathematical model of DQ current decoupling control, SOGI-PLL phase-locked model analysis, and the energy feedback unit with bipolar SPWM inversion to 50 Hz sinusoidal AC. The scheme is simulated and validated by Matlab/Simulink. The simulated characteristic unit can simulate resistive, inductance, and capacitive loads. The energy feedback unit can verify the stability, high efficiency, and practicability of the scheme with 50 Hz sinusoidal AC feedback.

Stability Analysis of Active Front End and Permanent Magnet Synchronous Generator With Back EMF-Based Sensorless Control for DC Marine Vessels

This article studies the influence of sensorless control on the permanent magnet synchronous generator (PMSG) and pulsewidth modulation (PWM) converter (active front end rectifier, AFE) system for dc marine vessels. Back EMF-based sensorless control is adopted in this article because the minimum speed of PMSG in a dc marine vessel is enough for obtaining a sufficient back EMF signal. First, the output impedance of “PMSG+AFE” system with a typical topology and controller is deduced by small-signal analysis. The stability analysis with constant power load (CPL) is analyzed, including the influence of sensorless control bandwidth on PMSG with a significant per-unit impedance value. Since the inductance parameter affects both the current control and sensorless control, the influence of error in the estimated inductance parameter on the stability of “PMSG+AFE” system is analyzed. To verify the proposed impedance model, output impedance is measured in the simulation and experiment. The stability analysis with the proposed impedance model and load impedance of CPL is provided in MATLAB, and simulation results and experimental measurements are given to verify the analysis.

Transformer-Less Soft-Switching High-Gain PWM Boost Converter With Reduced Components and Increased Effective Duty Cycle

A transformer-less soft-switching high-gain pulsewidth-modulation (PWM) converter is proposed in this article. The proposed converter is derived from a single-switch dual-inductor transformer-less boost converter by replacing the complementary diode connected to the switch with a synchronous rectifier switch. Moreover, the peak value of the reverse current of the rear-end inductor in continuous bidirectional conduction mode (CBCM) is regulated to exceed the input inductor valley current. Based on these two measures, the zero-voltage switching (ZVS) for all switches and the natural turn-off for the output diode are realized, and the effective duty cycle is enhanced. Besides, the proposed ZVS converter has the merits of fewer power components count, reduced voltage stress, and lower cost. Furthermore, the ringing issue in the original topology under light load or high input voltage conditions is eliminated. The operation principle, steady-state characteristics, dynamic model, soft-switching operation, and realization conditions are analyzed in detail, and subsequently, the parameter design method is elaborated. The proposed topology demonstrates an enhanced efficiency performance over wide operating operations with a maximum efficiency of 97.1%.

Butterfly Interleaving Winding Arrangements for Multiphase Coupled Inductors

Multiphase coupled inductors in pulse-width modulated (PWM) converters benefit from the reduced steady-state current ripple and fast transient performance. This article proposes a magnetic core geometry together with a butterfly interleaving winding arrangement to integrate the four-phase negative coupled inductors. It adopts the interleaving winding strategy usually used in planar transformers to reduce the proximity effect. Basically, each winding has two overlapped areas with other two windings. The two currents in the overlapped area are in opposite directions. The proximity effect is, therefore, reduced. Compared with the conventional nonoverlapped winding arrangement, finite element analysis simulation indicates more than 60% ac resistance reduction and almost 30% footprint minimization. Both design considerations and design guidelines for the multiphase buck converter with coupled inductors are presented. The magnetic core and winding structure are demonstrated in a 36–75 V (nominal at 48 V) to 30 V four-phase negative coupled buck converter as a front stage for datacenter applications. It is implemented on a six-layer printed circuit board (PCB) without any parallel winding connections, and can operate up to 1165 W. The experiment shows the prototype achieves 99.3% peak efficiency with 912 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> power density.

High Efficiency and High Power Density Partial Power Regulation Topology With Wide Input Range

Data centers require high efficiency and high power-density dc–dc converter with wide input range and galvanic isolation. To overcome the drawbacks of traditional single-stage <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> and two-stage solutions, a novel partial power regulation topology with wide input range is proposed in this article. The proposed topology delivers the load power through a three-ports <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> -based dc transformer regulated DCX (DCX). A pulsewidth modulation (PWM) converter is cascaded with one of the input ports of the DCX and then in series with the other input port to regulate the output voltage. Since a single transformer and a partial power PWM converter are employed, high power density can be achieved. Furthermore, only a portion of the load power is transferred by the PWM converter, the efficiency sacrifice is reduced. By introducing an appropriate negative current, the zero voltage switching of the PWM is also achieved. Furthermore, when the input voltage approaches the lower or the upper limit, the switching frequency of the PWM regulator can be ultralow. As a result, switching losses and core losses are further reduced. Finally, a prototype with 190—475 V input and 12 V/500 W output is demonstrated, which achieves a peak efficiency of up to 97.2% and a power density of 153 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Open-Switch Fault Diagnosis of Three-Phase PWM Converter Systems for Magnet Power Supply on EAST

The three-phase two-level pulsewidth modulation (PWM) converter operates in rectification state or active inverter state according to the corresponding experimental requirements of Experimental Advanced Superconducting Tokamak. However, the current fault diagnosis methods proposed for PWM converters usually deal with only the rectification state or inverter state. To solve this problem, this article proposes a diagnosis method to detect single and double open-circuit faults under both the rectification state and active inverter state. First, an inception-based neural network diagnosis model is proposed, in which 1 × 1, 3 × 3, 5 × 5, and 7 × 7 convolution and 3 × 3 max-pooling processes are conducted in parallel at the input and the output and stacked together to generate the final output. Second, the model is trained using three-phase alternating current current signals to determine the location of open-switch faults with a large number of simulation data samples and fewer experimental data samples. Finally, the experimental result shows that the proposed model can accurately detect approximately 99.14% of the open-switch faults within 12.83 ms (<3/4 cycle) without an additional sensor. Furthermore, the result shows that the proposed model is robust to load voltage transient conditions and nonunity power factor conditions.

An Online Identification Method of Thermal Dissipation State for Forced Air-Cooled System of Power Converters

Thermal stress is the primary cause of malfunction and failure in power modules. As the main heat dissipation component, the heatsink plays a significant role in improving the reliability of power converters. However, due to the continuous accumulation of dust and impurities on the heatsink’s air inlet side, the thermal dissipation performance of the cooling system constantly declines, which influences the reliable operation of power modules. In this article, a computational fluid dynamics (CFD)-based simulation analyzes the declining mechanism of the heatsinks’ thermal transfer performance. Moreover, a novel online method is proposed for the cooling system’s thermal dissipation state identification. This method regards the steady-state thermal resistance as the feature parameter of the thermal dissipation state evaluation. And a parameter identification method is employed to identify the steady-state thermal resistance due to the difficulty of obtaining it in the transient thermal process. In addition, an ac/dc/ac pulsewidth modulation (PWM) converter is built for verification. The experimental results demonstrate that the proposed method enables accurate and fast identification of the cooling systems’ thermal dissipation state. It can be one of a solution for replacing the existing off-line manual periodic detection method, which helps improve detection efficiency and decrease maintenance costs.

A 28 nm 81 Kb 59–95.3 TOPS/W 4T2R ReRAM Computing-in-Memory Accelerator With Voltage-to-Time-to-Digital Based Output

Computing-in-memory (CIM) based on Resistive RAM (ReRAM) can effectively improve the energy efficiency and throughput of artificial intelligence (AI) edge devices. However, due to the complex hardware structure and the non-ideal factors of the circuit, improving the processing precision will sharply reduce the energy efficiency and reliability of AI computing. In this work, a high-performance ReRAM-based CIM accelerator is presented to solve the above problems using: 1) a 4T2R cell to replace the traditional 2T2R cell for weight storage with higher on/off ratio and smaller computing current; 2) a pulse width modulation converter to realize linear input with lower performance cost; 3) a voltage-to-time-to-digital based converter to reduce the power consumption and area of the output circuit. An 81Kb ReRAM based accelerator was designed using 28nm process with 1-4b input/weight/output. To verify the reliability of the accelerator, non-ideal factors are added in training and testing. For evaluation, a network is built for CIFAR-10 based on the proposed accelerator. The proposed accelerator achieves a high processing frequency of 167-500 MHz and an energy efficiency of 95.3-59 TOPS/W for 1-4b precision operation with an FoM (input-precision × weight-precision × energy efficiency) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.6\times $ </tex-math></inline-formula> higher than prior work.

A Parallel-Connected 24-Pulse Rectifier Using Hybrid Harmonic Reduction Method at DC Side

This letter proposes a parallel-connected 24-pulse rectifier using a hybrid harmonic reduction method at the dc side. The proposed rectifier contains an unconventional interphase reactor (UIPR) with a double-tapped primary winding and secondary winding connected pulsewidth modulation converter. The proposed method is a combination of the passive and active harmonic method. From the viewpoint of total harmonic distortion (THD) of the input line current, ripple load voltage, and kilovoltampere rating of the active auxiliary circuit, the UIPR and active injecting current are optimally designed. An experimental prototype is developed to verify the theoretical analysis. The experimental THD is about 2.87%, which shows good performance of harmonic reduction.