Two-level Three-phase Inverter Research Articles

Expanded virtual vector-based model forecastable control strategy for three-phase two-level inverters

Abstract A three-phase, two-level inverter based on model forecastable control has good transient performance but poor steady-state performance. Considering the limitation of a limited number of discrete voltage vectors in a two-level inverter topology, this paper proposes a virtual vector model prediction method based on the analysis of a time-stepped forecasting model for a three-phase grid-connected inverter. First, three fixed virtual voltage vectors are constructed in each sector, and the action time of the required fundamental vector is found. Then, the cost function is constructed, and the optimum is selected among the virtual and fundamental voltage vectors in each sector. Finally, a hardware-in-the-loop experiment was carried out based on the PE-Expert4 experimental platform developed by Myway Co., LTD. The results show that the proposed virtual vector model forecastable control strategy can effectively improve the transient and steady-state performance of three-phase two-level inverters.

Advanced detection and localization of open circuit faults in two-level three-phase IGBT-based inverters using machine learning approaches and discrete wavelet transform

Advanced detection and localization of open circuit faults in two-level three-phase IGBT-based inverters using machine learning approaches and discrete wavelet transform

Real-time of a two-level three-phase inverter controlled by PWM and full wave techniques

Sustainability in power generation is readily available and must be able to adapt to a variety of energy needs or integrate seamlessly into alternative distribution networks. This research aims to bridge the gap between continuous energy production and efficient energy utilization by advancing the understanding and application of three-phase dual-level voltage inverters. This study focuses on two main objectives: firstly, to develop a comprehensive model and secondly, to validate the functionality of a three-phase two-level voltage inverter. The control strategy employed for this inverter involves the full-wave method and pulse-width modulation (PWM). The results obtained from the hardware implementation of these control methods show impressive levels of success, closely matching the expected performance of the three-phase inverter. This success underlines the robustness and effectiveness of both full-wave and PWM control strategies. To further underline their practical applicability, experimental validation of PWM and Full Wave control methods is demonstrated in a controlled research laboratory environment.

Design and implementation of pulse width modulation gate control signals for two-level three-phase inverters

The switching control circuit in a DC to AC inverter is the critical part that is applied to control the power transistors insulated-gate bipolar transistor (IGBTs) and metal-oxide semiconductor field-effect transistor (MOSFETs). This paper proposes a high-performance and low-cost pulse width modulation (PWM) control signal with a 120º phase shift circuit for a two-level three-phase inverter. Typically, a PWM signal with a 120º phase shift for three-phase inverters is generated with the help of analogue components with more complicated designs and power losses or by using a microcontroller with necessary programming or coding. The proposed solution is to design a 120° three-phase shift circuit based on D flip-flops and the 555-timer to generate the clock signal for the flip-flop input in addition to the dead-time control circuit. The proposed circuit is controlled by one square wave signal as an input signal to generate six output PWM control signals at 50 Hz to operate six MOSFETs in the three-phase inverter. Simulation results in power simulation software PSIM and PROTEUS simulation tools are used to verify the proposed circuit. Hardware implementation of the proposed circuit and three-phase inverter is carried out to validate the performance of the proposed design.

Autonomous Gate Drivers Tailored for Triangular Current Mode-Based Zero-Voltage Switching Two-Level Three-Phase Inverters for Electric Vehicle Drive Systems

The demand for highly efficient and dynamic electric vehicles (EVs) has increased dramatically. The traction inverter, a pivotal component in an EV powertrain, plays a crucial role. This study is dedicated to designing a traction inverter with focus on achieving high efficiency and elevated power density and mitigating electromagnetic interference (EMI) issues. To realize these objectives, autonomous gate drivers (AGDs) are proposed and designed using LTspice simulation software. The aim is to achieve zero voltage switching (ZVS) at both turn-on and turn-off through the utilization of triangular current mode (TCM) control on the gate driver. The AGDs implement a current modulation scheme by sensing the current and voltage and generating gate-source voltage signals with minimal delays. The implemented current modulation scheme by the AGDs results in an efficiency exceeding 99% for a 10 kW power rating. The sinusoidal output waveforms not only contribute to extending the motor lifespan by mitigating sharp-edge voltages but also bring advantages such as reduced switch stress, decreased EMI, and simplified thermal management.

Theoretical Design and Experimental Implementation of a Three-Phase Two-Level Inverter with an Adapted Gate Driver Based on Bootstrap Circuit for Grid-Connected Renewable Energy Systems

Theoretical Design and Experimental Implementation of a Three-Phase Two-Level Inverter with an Adapted Gate Driver Based on Bootstrap Circuit for Grid-Connected Renewable Energy Systems

Output voltage control of the OVT inverter

The paper presents the possibility of the output voltage control of an OVT inverter. The idea of the OVT inverter construction is based on the orthogonal space vectors theory. The OVT inverter is built of two components two-level three-phase inverters: the main inverter (MI) and the auxiliary one (AI). The output voltage of the OVT inverter takes the shape of a stepped voltage analogous to the voltage generated by multilevel inverters. The paper demonstrates possible control methods of the output voltage frequency and amplitude. The results obtained during simulation studies prove that the output voltage essential parameters may be a function of the DC voltage and the control circuitry permits easy defining a selection of voltage/frequency characteristics.

Detailed Modeling and In-Situ Calorimetric Verification of Three-Phase Sparse NPC Converter Power Semiconductor Losses

The three-phase three-level (3-L) Sparse Neutral Point Clamped Converter (SNPCC) combines a 3-L matrix stage and a three-phase two-level inverter stage to generate 3-L switched output voltages with a reduced transistor count (10 instead of 12 or 18) compared to the classical 3-L NPCC or 3-L active NPCC structure, targeting variable-speed drive systems with low ripple of the motor phase currents or bidirectional three-phase PFC rectifier systems with reduced boost inductor volume. This paper analyzes and experimentally characterizes the performance of an IGBT-based three-phase 3-L SNPCC converter, and describes for the first time a hybrid current commutation effect between inverter-stage diodes and matrix-stage IGBTs that occurs when operating with lower modulation indices and leads to increased switching losses (up to 20%). The proposed new semiconductor loss modeling approach accounts for this effect successfully, which is verified (< 10% error) on an 800V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> , 7.5kW SNPCC hardware demonstrator using a new in-situ calorimetric method that facilitates accurate stage-level semiconductor loss measurements. Heat spreading effects caused by the asymmetrical losses injection and thermal decoupling between two in-situ loss measurement blocks are carefully checked with FEM simulations. Further, an experimental evaluation of common-mode and differential-mode high-frequency voltage-time area ripples (as a generic measure for the required filtering effort) for three typical symmetrical and asymmetrical modulation switching state sequences is provided together with the semiconductor loss characterization. Utilizing a low-switching-loss asymmetric modulation scheme that operates the 3-L matrix stage and the 2-L inverter stage with effective switching frequencies of 16kHz and 5.3kHz, respectively, the 3-L SNPCC demonstrator finally achieves a high rated-power (7.5kW, load current phase shift ϕ = 0) semiconductor efficiency of 98.8%.

A Direct Model Predictive Control Strategy With an Implicit Modulator for Six-Phase PMSMs

This article proposes a direct model predictive control (MPC) scheme for asymmetric six-phase permanent magnet synchronous machines (PMSMs), which combines control and modulation in one computation stage. By emulating the switching pattern of space vector modulation (SVM), the MPC problem is formulated as a 4-D current control problem where the switching sequences and instants are computed and directly applied to the inverters. This implicit modulation addresses the issue of a variable switching frequency and spread harmonic spectra of conventional direct MPC methods. Moreover, the effect of the modulation constraints and controller bandwidth on the system performance is investigated as well. To verify the effectiveness of the proposed control strategy, experiments are carried out with an asymmetric six-phase PMSM driven by two three-phase two-level inverters.

Direct Speed Control Based on Finite Control Set Model Predictive Control With Voltage Smoother

A direct speed control strategy based on finite control set model predictive control (FCS–MPC) with a voltage smoother is presented herein. In the proposed concept, a finite set of smoothed voltage vectors characterized by an adjustable amplitude and a movable origin is introduced as voltage candidates in the FCS–MPC scheme. The controller predicts the future current and speed and outputs the optimal smoothed voltage using pulse-width modulation. Owing to this control scheme, an abrupt change in the output voltage, which causes a large current ripple, is avoided without additional computational costs. Simulation and experimental results obtained using a permanent magnet synchronous motor fed by a two-level three-phase inverter show that the proposed method effectively reduces the current ripple while achieving a high dynamic drive compared with the conventional FCS–MPC scheme.

THD Minimization under Low Switching Frequency for Superior Two Level Three Phase Inverter Performance

The total number of switching pulses permitted in one-quarter of the fundamental-cycle of an inverter is restricted due to the restrictions of switching losses in high-power inverter devices. The elimination of major low-order dominating harmonics using SHEPWM (Selective Harmonic Elimination) is suggested in this research paper. The positive or negative voltage transition at the instant where fundamental voltage has the greatest positive slope distinguishes the various types of waveforms. Due to the switching loss limitations, two forms of the pole voltage PWM waveforms i.e., type A, type B, were studied in this research at lower pulse number (P = 5). For a two-level three-phase inverter, an ideal Pulse Width Modulated (PWM) waveform is developed for whole modulation index range in terms of least total harmonic distortion (THD). MATLAB simulation and practical experiments are performed for a two-level inverter to support the theoretical analysis and results.

Comparison of Interleaved Boost Converter and Two-Phase Boost Converter Characteristics for Three-Level Inverters

A boost converter is used in various applications to obtain a higher voltage than the input voltage. One of the current main circuit systems for hybrid electric vehicles (HEVs) is a combination of a two-phase boost converter (parallel circuit) and a three-phase two-level inverter. In this study, we focus on the boost converter to achieve even higher efficiency and propose an interleaving scheme for a boost converter suitable for a three-level inverter (series circuit). The series circuit has two capacitors connected in series and makes it suitable as a power supply for a three-level inverter. We analyze the input current ripple of the series and parallel circuit in order to show the superiority of the series circuit. Furthermore, we propose a novel output voltage control strategy using an optimal regulator, namely a Linear Quadratic Regulator (LQR), for the series circuit. As a result, we found the input current ripple of the series circuit is smaller than the parallel circuit and demonstrated the superiority of the series circuit. The simulation and experimental results show the effectiveness of the proposed interleaving scheme and optimal regulator.

A Generalized Current Trajectory Based Fault Diagnostic Method for Three-Phase Two-Level Inverters

Inverters play a vital role in the distributed generated energy systems. Hence, the reliability of the entire distributed energy system depends on the consistent and continuous operation of the inverter. Consequently, to maintain a reliable operation, effective condition monitoring and fault diagnostic schemes have to be incorporated. In this paper, a method based on current trajectory is analyzed for the fault detection and diagnosis of open-switch faults in three-phase two-level voltage source inverters (VSI). The current trajectory-based method of fault diagnosis has been already presented literature for the identification and localization of open-switch fault in the three-phase two-level VSI. The main drawback of the existing current trajectory method is that the fault diagnosis and detection is dependent on the phase currents selected to plot the current trajectories. Therefore, in this paper, a generalization is proposed for the fault diagnosis and diagnosis based on the current trajectory, which make the method independent of the selection of the phase current used to plot the current trajectory. The validity and effectiveness of the proposed generalization is verified by simulation and experiments in a laboratory prototype of three-phase two-level VSI.

A Real-Time Digital Twin and Neural Net Cluster-Based Framework for Faults Identification in Power Converters of Microgrids, Self Organized Map Neural Network

In developing distribution networks, the deployment of alternative generation sources is heavily motivated by the growing energy demand, as by environmental and political motives. Consequently, microgrids are implemented to coordinate the operation of these energy generation assets. Microgrids are systems that rely on power conversion technologies based on high-frequency switching devices to generate a stable distribution network. However, disrupting scenarios can occur in deployed systems, causing faults at the sub-component and the system level of microgrids where its identification is an economical and technological challenge. This paradigm can be addressed by having a digital twin of the low-level components to monitor and analyze their response and identify faults to take preventive or corrective actions. Nonetheless, accurate execution of digital twins of low-level components in traditional simulation systems is a difficult task to achieve due to the fast dynamics of the power converter devices, leading to inaccurate results and false identification of system faults. Therefore, this work proposes a fault identification framework for low-level components that includes the combination of Real-Time systems with the Digital Twin concept to guarantee the dynamic consistency of the low-level components. The proposed framework includes an offline trained Self Organized Map Neural Network in a hexagonal topology to identify such faults within a Real-Time system. As a case study, the proposed framework is applied to a three-phase two-level inverter connected to its digital model in a Real-Time simulator for open circuit faults identification.

Inverter Nonlinearity Compensation for Open-Winding Machine With Dual Switching Modes

In this article, a novel inverter nonlinearity compensation method is proposed for open-winding (OW) machines fed by isolated dc-bus dual two-level three-phase inverters with dual switching modes. Inverter nonlinearity of dual inverters is analyzed in both balanced and unbalanced switching modes, and the different voltage distortions are utilized for a closed-loop inverter nonlinearity compensation by alternately applying the two switching modes. The proposed strategy needs no off-line measurement for the parameters of dual inverters and the electrical machine, and can also deal with the variation of inverter parameters in different operation conditions. Furthermore, the proposed strategy can overcome issues in conventional current harmonic-based methods, such as the need for accurate rotor position and preset compensation voltage curves. Experimental results verify the performance of the proposed inverter nonlinearity compensation method.

Thermal Management of IGBT Module in the Wind Power Converter Based on the ROI

Insulated gate bipolar transistor (IGBT) module is one of the most prone-to-fail components in the wind power converter (WPC). The reduction of the junction temperature swing by thermal management can improve the reliability of a WPC. Due to the lack of an applicable selection criterion, not many studies on the control target of junction temperature swing were reported. This article proposes a thermal management strategy to find the control target of junction temperature swing. The proposed strategy considers the return on investment (ROI) of thermal management as a quantitative indicator to guide the control target selection. The selected control target enables optimal benefit of the thermal management. Results show that a 1% increase in the total harmonic distortion would extend the lifetime of IGBT module by 0.144 years. Success of the proposed scheme lies in the efficient regulation of the junction temperature swing. Case studies with different mission profiles and experimental tests on a three-phase two-level inverter are presented to validate the proposed method.

Novel Three-Phase H10 Inverter Topology With Zero or Constant Common-Mode Voltage for Three-Phase Induction Motor Drive Applications

A traditional two-level 3-φ voltage source inverter topology operated with remote state pulsewidth modulation (RSPWM) can achieve constant common-mode voltage (CMV) without using additional passive components. However, apart from the poor harmonic performance, this topology suffers from the drawbacks of reduced dc bus utilization, increased semiconductor requirement, and higher losses. To address these issues, this letter presents a new H10 inverter topology for two-level three-phase inverter applications. The proposed topology can achieve constant CMV or zero CMV without requiring additional passive components. Compared with the RSPWM approach, the proposed H10 topology has 50% higher dc bus utilization, superior harmonic performance, reduced semiconductor requirement, and lower losses. A comparison of the proposed topology with the existing two-level solutions for CMV reduction reveals that the proposed H10 has the lowest total switch voltage rating and phase current total harmonic distortion (THD), considering zero CMV performance. Various experimental results obtained from a laboratory prototype are presented to validate the theoretical claims.

A Study of Inverter Open-Circuit Fault in Grid Connected Photovoltaic Systems: Influence on Output Power and Detection Method

The paper presents an investigation of single switch open-circuit fault in the inverter of photovoltaic (PV) systems. An IGBT two-level three-phase inverter which is used to connect the photovoltaic system to the main grid is considered in this application. First, the fault is created by modifying the control gate signal sent to the inverter. Second, the operation of a PV system is simulated under various levels of the irradiation under both healthy state and the condition of single switch open-circuit fault. The output powers generated by the system are then compared to show the influence of fault occurrence. Based on the DC current of the inverter, fault detection method is recommended. Investigation results show that the fault strongly affects the output power and that can be detected by judging the amplitude of three first orders of the AC side fundamental frequency.

Topology Review of Three-Phase Two-Level Transformerless Photovoltaic Inverters for Common-Mode Voltage Reduction

In grid-connected photovoltaic (PV) systems, a transformer is needed to achieve the galvanic isolation and voltage ratio transformations. Nevertheless, these traditional configurations of transformers increase the weight, size, and cost of the inverter while decreasing the efficiency and power density. The transformerless topologies have become a good solution. However, the problem is that commode-mode voltage and leakage current can occur via the stray capacitors between the PV array and the ground of the inverter. Various transformerless inverters have been introduced with different techniques, such as reducing the common-mode voltage or eliminating the leakage current. Furthermore, to introduce the development of transformerless PV inverters, especially in three-phase two-level inverter systems, this paper provides a comprehensive review of various common-mode voltage reduction three-phase two-level inverters.

Low Switching Frequency SPWM Strategies for Open-Winding Machine With Low Current Harmonics

In this article, two novel sinusoidal pulsewidth modulation (SPWM) strategies with simple implementation are proposed for an open-winding machine fed by isolated dc-bus dual two-level three-phase inverters to reduce switching frequency and current harmonics. The proposed strategies utilize zero sequence voltage injection and unbalanced reference voltage distribution to generate discontinuous PWM with low current harmonics and less switching action. Two different zero sequence voltages are introduced in this article corresponding to two proposed PWM strategies with different switching actions in a PWM cycle. The novelty of this article is low current harmonics and less switching actions in a PWM cycle compared with the conventional SPWM strategy. Moreover, compared with the subhexagonal center PWM strategy, the proposed SPWM strategies have advantages of easy implementation and half switching commutations with the same current harmonic characteristics. The superiority of the proposed SPWM strategies is validated by simulation and experiment results.