Inverter Switching Losses Research Articles

SVPWM‐Based Algorithm for Reduced THD and Switching Losses Under Varying Fundamental Frequency and Load in a VSI

ABSTRACTThe present study explores the influence exerted by various pulse width modulation (PWM) techniques upon harmonic distortion and switching losses of a voltage source inverter. In the context of this inquiry, a generalized algorithm for variable frequency operations, inspired by continuous and discontinuous PWM is outlined in this article. The algorithm is explicitly formulated as a function of fundamental frequency and the load power factor angle with the objective of minimizing total harmonic distortion (THD) and switching losses within a specified frequency range. The algorithm is segmented into various regions of frequency, guided by the theory that each region corresponds to a distinct PWM technique that yields reduced harmonic distortion. In this article, a minimum switching loss algorithm is introduced and implemented using both BCPWM and ABCPWM techniques. The algorithm is specifically designed to minimize switching losses across the entire range of load power factor angles. The integration of switching loss algorithm with the selection of the optimal PWM technique across different frequency ranges results in reduced switching losses and harmonic distortion. This leads to a comprehensive PWM algorithm that efficiently reduces both THD and switching losses during dynamic frequency and load changes. Experimental and theoretical evidences demonstrate the efficacy of the proposed algorithm in attaining minimum harmonic distortion and reduced switching loss operation during variations in fundamental frequency and load.

Implementation and Analysis of an Efficient Soft-Switching Battery Wireless Charger with Re-Configurable Rectifier

To significantly reduce switching loss of the high frequency inverter in battery wireless charger (BWC), improve the soft-switching stability and system reliability, a novel soft-switching BWC with low loss auxiliary network and re-configurable rectifier is presented. The presented soft-switching BWC can implement the smooth switching between constant current mode (CCM) and constant voltage mode (CVM) without frequency switching and relays, which is beneficial to enhancing the system stability. With the help of a novel low energy consumption auxiliary circuit, the power switch tubes in the H-bridge inverter can implement zero-voltage soft switch-ON and zero-current soft switch-OFF in the full range, completely eliminating switching loss of the inverter. The proposed scheme can enhance the system efficiency while refraining from the soft-switching range limitation and soft-switching failure caused by the system parameter perturbation. Finally, a 1-kW soft-switching BWC principle prototype is developed to validate the effectiveness and correctness of the proposed scheme.

A Hybrid PWM Strategy for Switching Loss Reduction in Three-Level Inverters

The advanced bus-clamping PWM (ABCPWM) sequences are well known to reduce line current THD in a three-level neutral point-clamped inverter. This paper deals with ABCPWM sequences employed optimally to achieve minimum switching loss throughout the linear operating region in a three-level inverter. The work extensively analyzes the performance of these sequences in terms of inverter switching loss and compares them with centered space vector modulation PWM (CSVPWM). Based on the analysis, a hybrid PWM scheme termed as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">switching loss reduction</i> is proposed by optimally employing ABCPWM sequences in conjunction with variation in power factors. At a given average switching frequency, the proposed hybrid scheme reduces inverter switching loss compared to CSVPWM and the recently proposed discontinuous PWM-based optimization strategy at all power factors and modulation indices. With this scheme, switching loss reduces to 22% to 36% compared to CSVPWM and a maximum of 12% reduction than the existing optimization strategy. Furthermore, the scheme gives lower harmonic distortion compared to these two existing PWM schemes near high modulation indices and near unity power factor load. The theoretical, simulated, and real-time simulation results are presented with experimental results using TMS320F28335 DSP controller for validating the proposed work.

Neural network based variable DC-link voltage control of electric vehicle driveline

ABSTRACT The variable DC link direct torque control (DTC) for induction motors was proposed in this paper utilizing an artificial neural network (ANN). Variable DC-link voltage is utilized as the inverter’s controlling input to improve the induction motor’s performance. By injecting the dynamically variable dc-link voltage, inverter switching losses are decreased and inverter efficiency is increased. Two significant limitations are the torque ripple in DTC and the speed regulation of induction motors at low speeds. The driveline of an electric vehicle is modeled, and the suggested control is put into practice to enhance low-speed speed regulation, high dynamic performance, and minimal torque ripple. With variable DC-link voltage based on ANN, an improvement in torque and speed is made possible. Additionally, the suggested strategy minimizes the current ripples. To verify the improved efficacy of the electric driveline under various operating scenarios, a proposed control of the electric driveline is implemented using MATLAB SIMULINK, and the results are compared with the conventional scheme. The recommended speeds for the three speed ranges are as follows: 300 rpm for low speed, 900 rpm for medium speed, and 1275 rpm for high speed. The torque ripples decreased from 0.39 to 0.24 in the low-speed region, 0.38 to 0.24 in the medium-speed region, and 0.36 to 0.24 in the high-speed region while the motor was operated at a constant load torque of 2 N-m. The torque ripples decreased from 0.4 to 0.274 in the low speed region, 0.4 to 0.274 in the medium speed zone, and 0.2 to 0.274 in the medium speed region when the motor operated at various speed regions with a constant load. The main effect of running the motor at different load torques, such as 1.5 N-m, 2.5 N-m, and 2.0 N-m, is shown in Table 9 and numerical data of torque ripples is presented in Table 9.

COMPARATIVE STUDY OF TRADITIONAL PWM INVERTERS AND MULTILEVELS INVERTERS

The need of higher powers in electrical drives has forced the researchers to develop new power source possibilities. Multilevel inverters have been presented as a cost effective solution for various high voltage and high power applications including power quality and motor drive problems. The traditional pulse width modulated (PWM) Inverter does not completely eliminate the unwanted harmonics in the output waveform. Using the multilevel inverter as an alternative to traditional PWM inverters for electric motor drive applications is investigated. The concept of the Optimized Harmonic Elimination Stepped-Waveform (OHESW) technique for a multilevel inverter is presented. The effectiveness of this technique in minimizing the inverter switching losses and its output voltage harmonic content which cause reducing harmonic losses and torque pulsations of an induction motor fed form is investigated analytically. Comparison between the Selective Harmonic Eliminated PWM (SHEPWM) as a traditional PWM technique for three-level inverter and the OHESW technique for multilevel inverter with regard to the switching losses, harmonic distortion, additional harmonic losses in the motor and the pulsating torques is also presented.

An Application of Neural Network-based Sliding Mode Control for Multilevel Inverters

Multi-level 3-phase inverters using cascaded H-bridges are becoming prominent in the electric drive and renewable energy sectors due to their high capacity and ability to withstand high voltage shocks. Therefore, the modulation and control techniques used in these multilevel inverters have a crucial influence on the quality of the output voltage they produce. The significantly high common-mode voltage amplitude they generate is one of their disadvantages, causing leakage currents and harmonics. This article proposes a new technique using sliding mode control combined with neural networks to manage a three-phase multi-level inverter. The research objective of this innovative technique is to eliminate the need for current controllers and conventional modulation that relies on carrier signals, reducing hardware calculations and enhancing dynamic response. In addition, it demonstrates the ability to minimize harmonics, common mode voltage, and the number of switching counts, thereby limiting the inverter switching losses and increasing device performance. Simulation results performed on a 5-level 3-phase inverter using cascaded H-bridges have confirmed the effectiveness of the proposed method.

Comparison of 2L + 2M and 6L SVPWM for Five-Phase Inverter to Reduce Common Mode Voltage

Multiphase drives have received a lot of interest because of their several features over traditional three-phase systems for high-power applications. Pulse-width modulation (PWM) approaches are necessary to regulate the supply for multiphase ac drives. As a result, it is vital to continually improve the modulation and control approaches used to upgrade output power converters’ quality. This paper offers a comparative analysis of the 2L + 2M and 6L space vector pulse-width modulation (SVPWM) techniques applied to a five-phase two-level voltage source inverter (VSI) fed an inductive (R-L) load. The comparative evaluation is based on measuring the inverter switching losses, the total harmonic distortion (THD) values, and the common mode voltage (CMV) under different operation scenarios. A system model is carried out by MATLAB/Simulink. An experimental prototype is constructed in the lab to validate the theoretical analysis. Simulation results for the system based on the two SVPWM techniques are obtained at different modulation indices and different output frequencies and are confirmed by the experimental results. It has been found that the peak-to-peak CMV of the 6L method is 80% lower than that of the 2L + 2M method. Moreover, 6L SVPWM offers better DC-link utilization compared to 2L + 2M SVPWM.

Comparisons of Loss Reduction Techniques Based on Pulsewidth Modulation and Model Predictive Control for Three-Phase Voltage Source Inverters

Due to the lack of comparative studies between discontinuous pulse-width modulation and model predictive control methods for reducing switching losses in two-level three-phase voltage source inverter, a comparative analysis of a generalized discontinuous pulse-width modulation and two model predictive control approaches for reducing switching losses is studied in this paper. Both generalized discontinuous pulse-width modulation and two model predictive control approaches are described and conducted in the simulation and experiment. The output performance is obtained by these methods after conducting in various conditions, including switching frequency, output power, and load conditions. It is validated that the generalized discontinuous pulse-width modulation control scheme achieves a better control performance at steady-state, while two model predictive control schemes have better transient-state performance with a superior dynamic. Additionally, the generalized discontinuous pulse-width modulation approach achieves better reducing switching losses performance and has slightly higher efficiency than that of two model predictive control approaches.

POWER SPECTRAL DENSITY OF DUAL RANDOMIZED DISCONTINUOUS PULSE WIDTH MODULATION

This paper addresses the spectral characteristics of a carrier-based dual randomized discontinuous pulse width modulation (DRDPWM) technique for reducing conducted EMI and switching losses in three-phase voltage source inverters. It combines two simple random schemes, random carrier frequency modulation (RCF-DPWM) and random pulse position modulation (RPP-DPWM). First, the modulating principle of the DRDPWM is presented. Then, the analytical expressions of power spectral density (PSD) that characterize the output voltage of the three-phase inverter are derived. Analytical and simulation results show the effectiveness of PSD spreading of the DRDPWM. Finally, experimental results verify the analytical and simulation results and prove the effectiveness of the DRDPWM scheme in spreading the spectrum compared to simple schemes (RPP-DPWM and RCF-DPWM) and conventional scheme DPWM.

Reduction of common mode voltage for grid-connected multilevel inverters using fuzzy logic controller

Cascaded multilevel three-phase inverters are increasing in industries of electric drives and renewable energy because of their large capacity and suffering from high voltage shock. However, the high magnitude of common mode voltage is one of the drawbacks. Thus, the techniques of modulation and control in these multilevel inverters significantly affect the power quality of the output voltage of inverters. This paper presents a technique using fuzzy logic technique for grid-connected cascaded multilevel 3-phase inverters. This technique has completely removed the current controllers and the conventional modulation using carriers. It also helps reduce the magnitude of common mode voltage and increase the dynamic response. Moreover, the ability to reduce harmonics and switching count also helps decrease the switching loss of inverter. The simulation results on a grid-connected cascaded 5-level 3-phase inverter have validated the effectiveness of the presented technique compared with that of the conventional method using phase opposition disposition (POD) and PI current controllers.

Simple Discontinuous Pulse-Width Modulation Scheme for the Loss Reduction of a Dual Inverter Fed an Open-End Winding Induction Motor

This paper presents a simple discontinuous pulse width modulation (DPWM) switching scheme to reduce the switching loss of a single DC-link dual two-level inverter fed an open-end winding (OW) induction motor (IM). The dual inverter system is attractive in many applications due to higher DC-link voltage utilization. Additionally, the OW motor has the potential fault-tolerant capability. However, the use of the dual inverter results in reduced system efficiency due to increased power losses in the inverter. Moreover, an OW motor inherently suffers from a zero-sequence current (ZSC) issue because the open neutral point of the stator windings provides the ZSC path. The ZSC causes negative effects in the system, such as an additional power loss and total harmonic distortion (THD). Thus, this work proposes an optimal DPWM scheme to reduce the inverter loss while suppressing the ZSC. Additionally, this work proposes a strategy to make the average power loss of each inverter equal. The performance of the proposed method is discussed in terms of switching power loss reduction and ZSC suppression. Simulation and experimental results are provided to verify the effectiveness of the proposed DPWM scheme.

Fixed Switching Frequency Hybrid Modulation With ZVS for Single-Phase Inverter

Soft switching technology is an effective way to reduce the switching loss of the single-phase inverter to improve efficiency. Because of the ease of implementing soft switching, inverter works in boundary conduction mode (BCM) is widely used. On the contrary, BCM causes wide variation in switching frequency and large inductor current ripple. In this article, a fixed switching frequency hybrid modulation method for the inverter is proposed, which can achieve zero-voltage switching without changing the switching frequency and reduce the peak value of inductor current. The modulation achieves good tracking of the output current with different loads by switching mode between the triangular mode and the trapezoidal mode accurately. For implementing modulation, the operation states of the inverter with different conditions are analyzed in detail, the number of operation states is deduced and the state machine about mode switching is summarized. In addition, a single-phase inverter prototype is designed to verify the feasibility and effectiveness of the proposed modulation. Compared with BCM, the efficiency of the inverter at both light load and full load is increased.

Coil-to-Coil Efficiency Optimization of Double-Sided LCC Topology for Electric Vehicle Inductive Chargers

This article presents an efficiency optimization of double-sided <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> compensation network for inductive power transfer systems. Compensation factors of the primary and secondary <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> circuit are defined and optimized analytically. The investigation shows that the secondary compensation factor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k_{rx}$</tex-math></inline-formula> highly influences the copper loss of the wireless coupler, whereas the primary compensation factor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k_{tx}$</tex-math></inline-formula> should not be large in order to reduce the switching loss and conduction loss of the input inverter. With a proper selection of these compensation factors, it is possible to achieve a high and sustained efficiency over a wide range of load and misalignment. In order to demonstrate the feasibility and validity of the proposed method, a scaled-down prototype has been implemented with the operating frequency of 85 kHz, transfer gap of 170 mm, and misalignment of up to 100 mm. Experimental results show a good agreement with the theoretical analysis. The peak efficiency of the proposed system is 91.6% under the perfect alignment at the coupling coefficient of 0.172. The efficiency still remains at 86.37% even under 100-mm misalignment with the coupling coefficient of 0.123.

Research and Development of Adjustable Discontinuous Pulse Width Modulation Method for Three-Phase Voltage Source Inverter

Continuous pulse width modulation (CPWM) and discontinuous pulse width modulation (DPWM) strategies are used to control voltage source inverter operation. CPWM strategies allow for the reduction of total harmonic distortion values, while DPWM strategies provide a more effective reduction in inverter switching losses. The paper is devoted to the problem of improving the three-phase voltage source inverter efficiency by a controlled transition from CPWM to DPWM. The article proposes an adjustable discontinuous pulse width modulation (ADPWM) method, which means a transition from space vector PWM (refers to CPWM strategies) to DPWM in all inverter phases when the switches’ temperatures exceed the allowable value in at least one of the inverter phases. The method flowchart is presented and an algorithm for modifying the envelope curve within one sector is given. In order to test the ADPWM method a Simulink-model of a three-phase voltage source inverter and its control system were developed. A study of the proposed ADPWM method’s efficiency in comparison with CPWM, PCDPWM and NCDPWM methods was carried out using a Simulink-model. It was established that the proposed ADPWM method provides dynamic losses reduction in the inverter switches by 2.86 times compared to CPWM and by 1.89 times compared to PCDPWM and NCDPWM methods. Power supply systems for medium and high-power AC motors provide a promising area for application of the proposed ADPWM method.

DC-Link voltage control of a multifunctional PV-GCVSI to reduce VSI switching losses

ABSTRACT The reference input dc voltage of grid connected voltage source inverter (GCVSI) is altered in this article based on power (both active and reactive) injection from GCVSI for minimising inverter switching losses, and total harmonic distortion (THD) of grid current. If the GCVSI is exclusively used for actual power injection from the photo-voltaic (PV) system to the utility grid, the needed input dc voltage of GCVSI is twice the utility grid phase peak voltage. According to the literature, GCVSI is also used to compensate for power quality issues, and in these circumstances, the dc-link voltage value is determined by the maximum power injection of GCVSI. Under reduced load, and reduced power generation from the PV system, keeping maximum GCVSI input dc voltage reference causes extra voltage stress at GCVSI switches, and the grid current THD is worse due to high ripple current in filter inductance. Therefore, to reduce the inverter switching losses and to improve the grid current THD, the relationship between the GCVSI input dc voltage reference and the power flow from GCVSI has been formulated. The proposed work is verified using simulation studies, as well as hardware studies, and the results are compared with existing methods for validation.

Analysis of torque ripples and switching losses of a diode clamped inverter fed permanent magnet synchronous motor drive

Analysis of torque ripples and switching losses of a diode clamped inverter fed permanent magnet synchronous motor drive

Analysis of torque ripples and switching losses of a diode clamped inverter fed permanent magnet synchronous motor drive

The modern-day electric vehicles use brush less DC motors (BLDC) and Permanent Magnet Synchronous Motors (PMSM) as the main driving units. The traction systems also have tried PMSM machine as the driving unit. The variable frequency power source is required to control the speed and torque of the motor to meet the load requirements. The Inverter – power modulator is causing the production of ripples in source current and flux components, hence the torque. This paper presents the effect of inverter on the flux and torque ripples. Also, the simulation results of inverter switching losses are discussed.

Modular Single-Stage Three-Phase Flyback Differential Inverter for Medium/High-Power Grid Integrated Applications.

This paper proposes a single-stage three-phase modular flyback differential inverter (MFBDI) for medium/high power solar PV grid-integrated applications. The proposed inverter structure consists of parallel modules of flyback DC-DC converters based on the required power level. The MFBDI offers many features for renewable energy applications, such as reduced components, single-stage power processing, high-power density, voltage-boosting property, improved footprint, flexibility with modular extension capability, and galvanic isolation. The proposed inverter has been modelled, designed, and scaled up to the required application rating. A new mathematical model of the proposed MFBDI is presented and analyzed with a time-varying duty-cycle, wide-range of frequency variation, and power balancing in order to display its grid current harmonic orders for grid-tied applications. In addition, an LPF-based harmonic compensation strategy is used for second-order harmonic component (SOHC) compensation. With the help of the compensation technique, the grid current THD is reduced from 36% to 4.6% by diminishing the SOHC from 51% to 0.8%. Moreover, the SOHC compensation technique eliminates third-order harmonic components from the DC input current. In addition, a 15% parameters mismatch has been applied between the flyback parallel modules to confirm the modular operation of the proposed MFBDI under modules divergence. In addition, SiC MOSFETs are used for inverter switches implementation, which decrease the inverter switching losses at high-switching frequency. The proposed MFBDI is verified by using three flyback parallel modules/phase using PSIM/Simulink software, with a rating of 5 kW, 200 V, and 50 kHz switching frequency, as well as experimental environments.

240$^\circ$-Clamped PWM Applied to Transformerless Grid Connected PV Converters With Reduced Common Mode Voltage and Superior Performance Metrics

Transformerless voltage source inverters (VSIs) are one of the popular topologies for photovoltaic (PV) grid-connected applications due to the lowest component count and simple design. Because of the absence of galvanic isolation in such systems, problem of electromagnetic interference (EMI) due to high leakage current is highly pronounced. Recently various reduced common mode voltage (CMV) PWM (RCMV-PWM) methods which address these issues of CMV, and leakage current have been proposed. These schemes typically function at the expense of increased total harmonic distortion (THD), higher switching loss, high DC link current stress along with limited modulation index range. In this work, 240<inline-formula><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> clamped PWM (240CPWM) is selected as an ideal candidate for grid connected VSIs in terms of all round performance of switching loss, THD, DC link current stress, CMV and leakage current. 240CPWM is a relatively new space vector based PWM method which can attain much superior performance by avoiding the zero states. After a brief overview of the 240CPWM concept, the paper provides a detailed comparison of 240CPWM with conventional space vector PWM (CSVPWM) and discontinuous PWM (DPWM1) methods in terms of each of the above metrics. A 3-phase 208 V 3 kW silicon IGBT based hardware prototype is built to validate the performance of 240CPWM and compared with other popular schemes under grid-connected mode. Experimental results show a 66.7&#x0025; reduction in the peak CMV and 50&#x0025; reduction in leakage current with the proposed scheme as compared to CSVPWM. Also, THD, DC link current stress and inverter switching loss are greatly reduced as an added advantage using the proposed method. A new, combined performance index is proposed to compare the performance of different PWM schemes, and it is shown that the 240CPWM achieves the best value for this index among the PWM methods studied.

Faster Convergence Controller With Distorted Grid Conditions for Photovoltaic Grid Following Inverter System

The hysteresis current controller (HCC) for grid following inverter (GFI) system with <inline-formula> <tex-math notation="LaTeX">$LCL$ </tex-math></inline-formula>-filter is a well-known controller for its robustness, fast reference tracking, better dynamics, and easier implementation compared to other controllers. However, HCC behaves differently while integrating such a system with solar photovoltaics (PV). The PV-based GFI system requires fast convergence while transferring maximum power from PV to the grid at minimum converter losses through GFI. This paper therefore proposes a modified double-band HCC (MDBHCC) with proportional resonant (PR) controller for single-phase PV integrated GFI system with LCL-filter. The proposed algorithm implements a unipolar symmetrical PWM strategy for reducing inverter switching losses through a sequential logic with an adaptive clock. It improves the variation in switching frequency and limits the maximum switching frequency of HCC while enhancing the total harmonic distortion (THD) of the injected current into the grid at the point of common coupling. To alleviate the power quality problem and achieve zero steady state error, the proposed MDBHCC with PR control operates at lesser &#x0025; THD. Simulation and experimental results are presented, with a significant decrease in switching frequency and an improvement in grid current harmonics at both steady-state and dynamic conditions.