PWM Converter Research Articles

Practical Approximation of Sheet Losses Taking into Account the Guillotine and Laser Cutting Effect

Reducing losses in electrical devices is essential for reducing global energy consumption. Losses in the core of electrical machines constitute a significant part of the overall losses—their share increases with the number of machines powered by PWM converters, especially for high-speed machines. Limiting core losses requires precise determination at the design stage of the device. Achieving this goal is possible thanks to numerical or analytical simulation. A necessary input for this process is the correct determination of the properties of the core material. The sheet loss, however, changes due to the machining process, primarily punching. The subject of the work is to develop a sufficiently accurate approximation of electrical steel sheet-specific loss, taking into account the effects of cutting and the width of a given machine element for a wide range of induction and frequency. The method also enables the extrapolation of losses for higher frequencies relevant from the point of view of generating losses in the machine. The developed loss approximation can be used in the finite element simulation and in applying analytical methods. The technique can be successfully used for many grades of non-oriented sheet metal, provided that the requirements specified in the work are met. The proposed approximation allows us to determine the loss of a sample of a certain width in a wide range of magnetic induction magnitude and frequency with an accuracy not worse than 4%.

Reluctance Network Model of IPM Motor Representing Dynamic Hysteresis Characteristics for High-Accuracy Iron Loss Calculation Considering Carrier Harmonics

It is essential to establish a simple and practical method for quantitatively estimating the iron loss considering the dynamic hysteresis behavior to further improve the efficiency of electric machines. In a previous study, a novel simple magnetic circuit model representing the dynamic hysteresis characteristics was presented by incorporating a play model, one of the phenomenological dc hysteresis models, and a Cauer circuit, which can consider the skin effect. It was demonstrated that this magnetic circuit model could accurately calculate the hysteresis loops and iron loss even under PMW excitation for magnetic reactors made of several types of core materials in a short time. However, this method can only be used for an object with a simple shape, such as a ring core. Hence, this paper describes that the previously proposed magnetic circuit model is extended to a reluctance network analysis (RNA) to expand the application range. Furthermore, the proposed method was experimentally validated using an interior permanent magnet (IPM) synchronous motor driven by a PWM converter as the examination target.

Partially Isolated Multiport Converter With Automatic Current Balancing Interleaved PWM Converter and Improved Transformer Utilization for EV Batteries

Multiport converters (MPCs) that can regulate multiple input/output ports have been proposed to reduce the converter count in electric vehicle battery systems consisting of multiple batteries (12-V, 48-V, and high-voltage batteries). Conventional MPCs consist of an interleaved PWM converter and DAB converter, and an active current balancing control is indispensable for the interleaved converter. Furthermore, the transformer utilization unavoidably decreases because switches are driven with a nominal duty cycle of 0.75 for 48-/12-V batteries. This article proposes a novel MPC with an automatic current balancing capability and improved transformer utilization. A flying capacitor (FC) is added to the interleaved PWM converter to automatically balance inductor currents. The added FC also allows operations with a nominal duty cycle of 0.5 for 48-/12-V batteries, improving the transformer utilization. The experimental verification tests using a 1-kW prototype demonstrated the automatic current balancing capability, improved transformer utilization, and flexible power exchange among three batteries.

An Improved Zero-Voltage and Zero-Current- Switching Phase-Shift Full-Bridge PWM Converter With Low Output Current Ripple

In order to improve the performance of traditional phase-shifted full-bridge converters and reduce the output current ripple, an improved zero voltage and zero current switching phase-shifted full-bridge PWM converter is proposed in this article. By adding a simple auxiliary circuit, the leading-leg switches realize zero voltage switching and the lagging-leg switches realize zero current switching. The primary current is reset during the freewheeling period, so the efficiency of the converter is improved. What is more, the improved converter can effectively reduce the output current ripple. The added auxiliary circuit does not include any lossy components or saturable reactors. The improved phase-shifted full-bridge converter has many advantages, including simple circuit topology, easy implementation of soft switching, high efficiency, and low output current ripple. The operational principle and analysis of the proposed converter are presented in this article. An 800 W experimental prototype is built for experimental verification.

3상 PWM 컨버터의 계통 리액터 위치에 무관한 상전압 측정 PLL 제어 알고리즘

This paper presents various control methods to improve the quality of recently developed power conversion equipment. Compared to diode rectifier, voltage-source PWM converter controls input current in an actively manner and is widely used as a stable power conversion device. A control operation characteristic of a conventional PWM converter is identified. The conventional voltage sensing position to derive the control angle of the PWM converter required for system control is complexly installed in the hardware and the weight increases as the capacity increases because the system includes the L filter. In order to compensate for these drawbacks, the proposed system is configured to have the flexibility of the system by changing the voltage sensing position to the input terminal of the converter. At this time, since the existing control angle and phase voltage must be estimated, the phase voltage at the changed position was followed by the power source side using LPF and DSOGI-PLL, and this was compared and confirmed through a simulation.

A Robust Duty‐Cycle‐Comparison‐Based Overload Detector for DC‐DC Converter

A novel duty‐cycle‐sensing overload detector for DC‐DC converter is proposed in this paper. Firstly, the theoretical analysis is conducted to reveal the susceptibility of the conventional overload detectors to temperature variation and the input/output‐voltage change of the DC‐DC converter. Then, the schematic of the novel duty‐cycle‐sensing overload detector is presented and its operation principle is analyzed. Thanks to the time register, the proposed detector generates a theoretically voltage‐and‐temperature‐insensitive threshold duty cycle, compares it with the real‐time duty cycle of the converter's PWM signal, and announces an overload event if the real‐time duty cycle exceeds the threshold. Finally, a prototype of a BUCK DC‐DC converter including the proposed detector and a conventional current‐sensing overload detector is constructed and measured. As the measurement results show, the threshold duty cycle only varies by about 2.4% as the temperature changes from 0 to 90 °C while the threshold voltage of the conventional current‐sensing detector changes by about 4.6%. The proposed detector can keep effective even the temperature rises to 90 °C while the conventional current‐sensing detector can work at a temperature no higher than 85 °C. Without circuitry modification, the proposed detector correctly senses the overload event as the DC‐DC converter's output voltage changes in a range of 2.1–2.9 V while the conventional one loses its effectiveness if the output voltage is set higher than 2.54 V. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Disturbance auto-encoder generation model: Few-shot learning method for IGBT open-circuit fault diagnosis in three-phase converters

With the rapid development of converters in a variety of industrial fields, the fault diagnosis of power switching devices has become an important factor in ensuring the safe and reliable operation of related systems. In recent years, machine learning has performed well in many fault diagnosis tasks. The success of these advanced methods depends on sufficient marked samples for each fault type. However, in most industrial applications, it is expensive and difficult to collect fault samples, and the fault diagnosis model trained under the limited samples cannot meet the requirements of fault diagnosis accuracy. In order to solve this problem, this study proposes a few-shot learning method based on fault sample generation to realize the open-circuit fault diagnosis of IGBT in a three-phase PWM converter. This method is the deformation of the auto-encoder called the disturbance auto-encoder generation model. By designing the model structure and training algorithm constraints, the encoder learns the nonlinear transferable disturbance from the normal operating sample pairs. Then, the disturbance is applied to the decoder to synthesize new fault samples to realize the training of the fault diagnosis model with limited samples. The biggest advantage of this method is that it can achieve 95.90% fault diagnosis accuracy by only collecting the samples in the normal operating conditions of the target system. Finally, the feasibility and advantages of the proposed method are verified by comparative experiments.

Design of new robust backstepping control for three-phase grid-connected fourleg source voltage PWM converters

Design of new robust backstepping control for three-phase grid-connected fourleg source voltage PWM converters

Direct Deadbeat Control of a Buck PWM Converter

The paper explains the shortcomings of the well-known modal control strategy, which prevent its practical application to achieve the highest possible dynamic performance of switching semiconductor converters. A method for eliminating these shortcomings is suggested as applied to a self-contained modal control version with specifying zero roots of the characteristic polynomial and obtaining a nilpotent system matrix. A technique for synthesizing direct deadbeat control with a nilpotent system matrix is described in detail to implement a finite transient that terminates within a number of cycles not exceeding the order of the difference equation with which a discrete system is described. The control object is a well-known circuit of a DC-DC buck converter with an inductive-capacitive filter and a proportional input-output characteristic provided by an integral link in the feedback loop. The efficiency of the proposed deadbeat controller version is confirmed through mathematically simulating the operation of a PWM converter controlling the load current. The dynamic operation modes are studied for the case of a step change in the load resistance and input voltage relative to their nominal values for a control system with I-, PI- and deadbeat controllers. A comparison of the obtained results shows that the transients in the system equipped with a deadbeat controller terminate most quickly: within three cycles without an overshoot. This corresponds to the maximum convergence rate to the equilibrium state for a third-order system.

Synthesis of PWM Converters From Conversion Ratios Using Flux- or Charge-Balance Equations

To cater to the heterogeneity in emerging applications, researchers have constantly been driven to invent novel dc–dc converter topologies. A review of prior art in dc–dc converter synthesis methods shows that many converter choices are available for a given input and output specification. This article quantifies the number of these choices using the flux balance equation (FBE). As the number of state variables that can be used to derive the FBE is limited, it is possible to find out the total number of possible FBEs available for a given voltage conversion ratio. Once the FBEs are known, synthesizing a converter is carried out as an inverse problem. Three different strategies to solve this inverse problem of converter synthesis and some critical synthesis results are summarized in this article. The dual synthesis of current-fed topologies with given current conversion ratios based on the charge balance equation (CBE) is also demonstrated. Four novel topologies were synthesized to illustrate the effectiveness of the CBE-based synthesis method. The mathematical formulation of the CBE-based inverse problem and the quantification of complexities in solving it are also reported.

Analysis and Improved Control Strategy for New Generation Poloidal Field Power Supply

To improve the performance and dynamic response ability of poloidal field power supply (PFPS), the three-phase PWM converter-cascaded H-bridge inverter structure is adopted in the new generation PFPS. However, the load power of PFPS changes violently since the load characteristic is superconducting large inductance, which has a serious impact on the stability of the three-phase PWM converter control system. In this article, an improved dual closed-loop control strategy based on linear active disturbance rejection control (ADRC) is proposed to suppress the influence of load power disturbance, which is combined with the load power feedforward method and adding a decoupling link. Compared with the traditional control strategy based on PI controller, the simulation results show that the proposed control strategy has strong robustness to the change of load power, reduces the bus voltage fluctuation on the dc side, and improves the anti-interference ability and dynamic performance of the system.

Power quality improvement in single-phase transformerless semi-quasi-Z-source inverters for off-grid photovoltaic systems

The transformerless single-phase semi-quasi-Z-source inverter (SqZSI) provides several advantages over classical PWM converters. Reduced or eliminated leakage current, high power density, and low cost are important features making this topology an attractive choice for PV micro-inverter applications. Two drawbacks of this topology are DC and second harmonic injection in the output AC port, which in some cases prevent the fulfillment of standard requirements. To alleviate this power quality issue, four novel harmonic mitigation algorithms based on PI and PR controllers are proposed, analyzed, and experimentally verified with the 90 W SqZSI in this paper. Moreover, a modified modulation reference waveform strategy is introduced. Consequently, the converter performance, in terms of total harmonic distortion (THDV) is achieved at about 1.27% under full power load. Also, in this paper, the non-ideal state-space model of the SqZSI with the effect of the equivalent series resistance of inductors is developed and the generation origin of DC and second harmonic component is analyzed based on the obtained model. The achieved results confirms the significant THD reduction by more than 75%, the DC component suppression, the second harmonic mitigation, and the power quality improvement.

Experimental study on the influence of high frequency PWM harmonics on the losses of induction motor

For the purpose of studying the influence of high frequency PWM harmonics on the losses of induction motor, this paper first introduces the latest international standard IEC/TS 60034-2-3 for the separation of the losses and the measurement of the efficiency of induction motor under PWM power supply. Then, considering that the skin effect of windings in induction motors under the condition of PWM power supply more apparent, this paper uses the stator AC resistance to replace the stator DC resistance in the IEC/TS 60034-2-3 standard to obtain more accurate separation results. On this basis, an improved method of loss separation for converter-fed induction motor is proposed by using the accurate time-step finite element method to calculate the rotor copper loss under no-load condition which cannot be considered in IEC/TS 60034-2-3 standard. Finally, this method is used to measure and separate the losses of a 5.5 kW converter-fed motor under different operating conditions. The results show that the loss of induction motor which is driven by PWM converter is obviously greater than that of sinusoidal drive, especially under light load or no load condition. The whole no-load losses of the motor driven by PWM converter increases by more than 20.0% compared with that of the sinusoidal driving condition.

Research on Space Vector Overmodulation Technology of Two-Level PWM Converters

In this paper, the characteristics of the voltage transfer ratio (VTR) and low-order harmonics of the major modern space vector overmodulation strategies for two-level PWM converters are discussed under different VTRs, and the complexity of the modulation algorithm is subsequently elaborated. First, the principles of these overmodulation strategies are summarized. After that, the accuracy and linearization of the VTR are obtained using the Fourier transform analysis, and the relationship between the main low harmonic components and the VTR is obtained in the same way. All the analysis results are verified through experiments. In addition, the merits and demerits of these overmodulation strategies and applications are revealed by comparing the simplicity of their modulation algorithm, digitization, and other characteristics. Finally, this paper reveals the essence of space vector overmodulation strategies. The results facilitate the design, performance prediction, and development of high-performance overmodulation strategies, as well as the transplantation of space vector overmodulation strategies into different converter topologies.

An Interleaved Two Switch Soft-Switching Forward PWM Power Converter with Current Doubler Rectifier

Forward converters have been broadly used in the power supply industry due to their simplicity, worthy efficiency, and low cost. A novel prototype soft-switched zero-voltage and zero-current ZVZC PWM DC-DC power converter with low voltage/current stresses is introduced for telecommunication power feeding in this paper. A new two-switch interleaved forward converter circuit is introduced to minimalize current circulation with no supplementary auxiliary snubber circuits. This converter circuit includes some outstanding benefits such as reduced components, improved efficiency, high power density and economic circuit configurations for high power conditioning applications. The simple operation principle is demonstrated on the basis of steady-state analysis. Furthermore, the effective feasibility of the proposed circuit topology is evaluated and verified practically for a 500 W–100 kHz prototype breadboard. The operation principle and steady-state characteristics are demonstrated from a theoretical point of view. To verify the practical effectiveness of the proposed power converter, a 500 W–100 kHz prototype converter using ultrafast IGBTs is implemented for a distributed telecommunication energy plant. The studied soft-switching converter is evaluated in comparison with the previously-proposed PWM converters in terms of voltage, current stresses, and operating efficiency.

An Improved Trapezoidal Voltage Method for Dead-Time Compensation in Three-Phase Voltage Source Converter

The dead-time between the switches in the upper and the lower bridge of voltage source PWM converters produces input current distortion, called as dead-time distortion. The dead-time distortion can be compensated by trapezoidal voltage. The conventional trapezoidal voltage compensation method (TVCM) only controls the angle of the trapezoidal voltage. By the control of the angle and amplitude of the trapezoidal voltage simultaneously, an improved TVCM is proposed to further reduce the dead-time distortion. The experimental results are provided to verify the analysis results.

Design and real-time validation of PI and Fuzzy Logic tuned photovoltaic integrated DSTATCOM to improve power quality.

Power loss and malfunctioning of equipment due to current and voltage harmonics produced by nonlinear loads are major concerns for both power suppliers and consumers. This paper employs DSTATCOM to mitigate these harmonic distortions in distribution systems. DSTATCOM is a current controlled voltage source PWM converter with passive components. It supplies compensating current that eliminates current harmonics and provides reactive power compensation thereby providing a smooth source current. The performance of DSTATCOM is controlled using proportional integral and fuzzy logic-based control (FLC) schemes to improve power quality at dynamic loading. As the penetration of photovoltaic (PV) systems in energy production is significant, the power quality issues for PV-integrated systems have also been investigated. The maximum power point for a PV array is tracked using perturb and observe and FLC methods. The complete system is simulated in MATLAB and extensively investigated for a large range of balanced and unbalanced nonlinear load conditions. The simulation results are validated in real time through the hardware in loop (HIL) test bench using Opal-RT controller. The proposed PV-integrated DSTATCOM with FLC yields better performance in terms of DC link voltage settling time, total harmonics distortion, and smooth source current as compared to other schemes.

Active power decoupling method for single-phase PWM converters without LC branch sensors

Active power decoupling method for single-phase PWM converters without LC branch sensors

Dynamic Analysis and Fractional-Order Terminal Sliding Mode Control of a Fractional-Order Buck Converter Operating in Discontinuous Conduction Mode

Fractional calculus provides a new tool for designing the control scheme of a PWM converter. However, in most studies of fractional-order converters, one has used the fractional orders of the converters to construct the controllers. Essentially, this controller does not add any additional fractional-order parameters, which will affect its flexibility. Taking the fractional-order Buck converter operating under discontinuous conduction mode (DCM) as well as the chaotic state as an example, this study proposes a novel fractional-order terminal sliding mode control strategy utilizing additional fractional orders. In order to analyze the nonlinear behaviors attributed to load changes, the discrete iterated mapping model of the voltage-controlled fractional-order Buck converter is proposed and built. According to the discrete iterated map, the bifurcation diagrams and Lyapunov exponent spectrums following different fractional orders are generated, indicating a process attributable to chaos. To suppress the undesirable nonlinear behaviors, a novel fractional-order terminal sliding surface is formed, and the corresponding controller is established. Moreover, the hyperbolic tangent function is introduced to solve the chattering problem. The proposed controller provides greater flexibilities to further improve the control capability. Furthermore, to verify the robustness of the proposed control method, the Mittag–Leffler stability condition of fractional-order systems is adopted. The effects of fractional orders on control performance are also discussed. Finally, circuit simulations with the approximate fractal structures of fractional-order components are implemented and compared so as to further verify the feasibility of the proposed controller.

Experimental Verification of Wind Power Generation System Using Diode Bridge Rectifier Circuit with Wind Turbine Simulator

This paper presents Wind Power Generation System using Diode Bridge Rectifier (WPGS-DBR method). Experimental results have been obtained by Wind Turbine Simulator (WTS). The WTS emulates wind turbine behavior using a servo motor as a drive system. Mechanical torque references used to drive the motor are calculated using wind turbine data such as wing blade, wind velocity, and wind turbine rotation speed. DBR method has three-mode control for three ranges of wind speed: low, medium, and high, respectively. In low and medium mode, the control system adjusts the armature current of a generator and DC link voltage with a Vector-Controlled Inverter (VCI) to control wind turbine speed. In high mode, the control system modulates the pitch angle of the wind turbine using a pitch angle control system for controlling wind turbine rotational speed. The DBR simplifies the maintenance of WPGS while improving reliability. In addition, the DBR method costs less compared with the WPGS using a PWM converter.