Active Neutral Point Research Articles

Low-complexity model predictive control of a four-level active neutral point clamped inverter without weighting factors

Abstract The four-level active neutral point clamped (ANPC) inverter has become increasingly widely used in the renewable energy industry since it offers one more voltage level without increasing the total number of active switches compared to the three-level ANPC inverter. The model predictive current control (MPCC) is a promising control method for multi-level inverters. However, the conventional MPCC suffers from high computational complexity and tedious weighting factor tuning in multi-level inverter applications. A low-complexity MPCC without weighting factors for a four-level ANPC inverter is proposed in this paper. The computational burden and voltage vector candidate set are reduced according to the relationship between voltage vector and neutral point voltage balance. The proposed MPCC shows excellent steady-state and dynamics performances while ensuring the neutral point voltage balancing. The efficacy of the proposed MPCC is verified by simulation and experimental results.

Model Predictive Torque Control-Based Induction Motor Drive with Remote Control and Monitoring Interface for Electric Vehicles

While the increased use of internal combustion engine vehicles raises carbon emissions, electric vehicles (EVs) are becoming more important for reducing air pollution. EV production costs are decreasing as technology advances since they are typically powered by alternating current induction machines (ACIM). In EV configurations that are propelled with ACIM, an inverter is required to obtain appropriate voltage levels to drive the IM. Multilevel inverters are widely preferred in the industry for DC–AC voltage conversion due to their high-power quality. In this study, the ACIM is supplied with the appropriate voltage using an active neutral point clamped (ANPC) inverter. The ANPC inverter acting as ACIM driver is controlled with model predictive torque control. The simulation of the proposed ACIM drive has been performed with torque and speed control features to determine the operational features of the experimental test bench. Furthermore, the designed ACIM drive includes remote control and monitoring functions via an Internet of Things-based module. This allows for instant monitoring of the input, output, and current values of the ANPC inverter. The graphical monitoring function is used to track the speed and torque values of ACIM while the speed can be changed remotely via the web interface.

Fault analysis in the 5-level multilevel NCA DC–AC converter

The existing neutral clamped active inverter has common mode voltage with the high frequency which can reduce the severity with less voltage gain. The traditional active neutral point clamped (APC) DC–AC converter maintains great common mode voltage with high-frequency (CMV-HF) reduction capability so, it has limited voltage gain. The paper presents a new 5-level active neutral point clamped DC–AC converter that can change voltage step-up in a single-stage inversion. In the suggested design, a common ground not only reduces the CMV-HF but also improves DC link voltage use. Compared with the traditional two-stage 5-level APC DC–AC converter, the proposed design has lower voltage stresses and greater uniformity. While improving the overall efficiency, the suggested clamped DC–AC converter saves three power switches and a capacitor. Modelling and actual tests have proven the suggested active neutral point clamped inverter’s overall operation, efficacy and achievability. The proposed circuit is finally tested with fault clearance capability.

Dual-Carrier-Based PWM Method for DC-Link Capacitor Lifetime Extension in Three-Level Hybrid ANPC Inverters

Power converters operate at varying low-, medium-, and high-voltage levels. Large electrolytic capacitors are usually used to sustain the associated dc-link current and stabilize the dc-link voltage. However, owing to different power converter applications, capacitors are affected by large ripples in the dc-link current, which increase heat exchange and reduce system reliability and lifespan. In this regard, this article proposes an innovative control technique for suppressing the ripple in the dc-link current and common-mode voltage (CMV) in hybrid active neutral point clamped inverters. The proposed control technique uses an improved dual-carrier-based pulsewidth modulation technique to create a new switching scheme by selecting the voltage vectors that contribute to the smallest ripples in the dc-link current according to each sector. Applying the proposed control technique significantly reduces the ripples in the dc-link current and CMV, which increases the reliability of the system and extends the lifetime of dc-link capacitors. The simulation and experimental results demonstrate the effectiveness of the proposed control strategy.

Low-Complexity Dual-Vector Model Predictive Control for Single-Phase Nine-Level ANPC-Based Converter

This article proposes a dual-vector finite-control-set model predictive control (FCS-MPC) with reduced complexity for a novel nine-level active neutral point clamped (ANPC) converter. This topology considerably reduces the used number of power switches compared to other topologies. Only nine power switches and two flying capacitors (FCs) are used to generate nine voltage levels. The proposed MPC scheme notably reduces the computational burden by directly locating the best two vectors without the need for multiple evaluations of the cost function as in the conventional method. Using one weighting factor in the cost function, three objectives are considered, namely, current tracking, FCs voltage control, and dc-link stabilization, reducing the heavy effort of coordinating weighting factors. Mathematical analyzes were carried out to determine the optimal duration of the selected voltage vectors. While the sequence of the two voltage vectors is identified based on the total harmonic distortion (THD) definition to minimize its value. Compared with standard FCS-MPC, lower steady-state errors, lower THDs, better harmonic distribution, and shorter execution times are achieved. The proposed MPC method is validated and compared with other prior-art control methods through experimental implementation.

Performance analysis and control of a novel 7‐level active neutral point clamped (ANPC) topology

AbstractThis paper introduces a novel 7‐level active neutral‐point clamped (ANPC) switched capacitor multilevel inverter (SCMLI) with voltage‐boosting capabilities. The proposed converter can produce seven levels and a voltage boosting of 1.5 times with a single dc source. For boosting the voltage, two self‐balanced switched capacitors and two dc link capacitors with active neutral point are used with nine switches. For controlling the output voltage, the level‐shifted modulation technique and modified nearest level control technique is used. The performance of the converter is evaluated with both modulation techniques. The operation of the proposed SCMLI and the design of capacitors for the proposed circuit is discussed in detail. The proposed topology can eliminate the leakage current and has reduced voltage stress across switches which makes it suitable for solar photovoltaic applications. The proposed converter is compared with some other recently introduced converters in terms of voltage gain, the number of components used, and the voltage stress across the switches. For verifying the performance of the proposed circuit, the experimental and simulation results are presented in the paper. The experimental results closely agree with the simulation and theoretical studies. The total harmonic distortion (THD) in the output voltage and efficiency is compared with both modulation techniques.

Low-Complexity Finite Set Model Predictive Control for Split-Capacitor ANPC Inverter With Different Levels Modes and Online Model Update

In this article, an improved finite-control-set model predictive control (FCS-MPC) is presented for an active neutral point clamped (ANPC) topology. The considered converter significantly reduces the required power electronics components compared with other common dc-link converters, where only seven active switches, one bidirectional switch, and two floating capacitors (FCs) are employed to produce nine levels in the phase voltage. The developed FCS-MPC handles three control objectives with only one weighting factor, namely, current control, FC balancing, and NP potential stabilization, which reduces the cumbersome effort required for weighting factors coordination. In addition, the number of iterations required to identify the optimal vector is significantly reduced, which, in turn, reduces the execution time of the algorithm. The proposed control method empowers the considered converter to operate in different modes under the faulty condition of the bidirectional switch without any structure modification, which guarantees continuous operation of the converter while ensuring the balancing of FCs and dc-link capacitors in all operating modes. The sensitivity of the proposed FCS-MPC to parameter mismatch, which is a basic issue of MPC-based techniques, is tackled by employing an extended Kalman filter (EKF) to online estimate the system parameters. The proposed FCS-MPC algorithm is experimentally validated and compared with the conventional FCS-MPC method under different operating conditions.

Five-Level Switched-Capacitor ANPC Inverter With Output Voltage Boosting Capability

This article proposes a three-phase five-level switched-capacitor active neutral point clamped converter, which can be characterized by voltage boost ability, low-voltage stress across semiconductor devices, and balance of floating capacitor voltage without any auxiliary circuits and/or sensors. Operating principles and modulation scheme of the proposed converter, as well as a comparative analysis with similar topologies are included. Simulation and experimental results for a three-phase prototype are given to demonstrate the feasibility of the proposed five-level converter.

Modulation Strategy for Suppressing Peak Voltage Spikes of SiC-MOSFETs During ANPC Commutation

After active neutral point clamped(ANPC) adopts SiC-MOSFETs, SiC-MOSFETs are easily damaged due to the excessive peak voltage. This paper establishes a single-phase parasitic inductance model of ANPC based on the SiC-MOSFET half-bridge modules. Then, based on this model, the cause of peak voltage on SiC-MOSFETs during ANPC commutation is analyzed. Finally, a short-loop commutation modulation strategy is proposed under the full working conditions of ANPC. The modulation strategy considers the influence of modulation carriers selection and dead time on ANPC commutation and optimizes the ANPC commutation loop to suppress the overvoltage on SiC-MOSFETs during ANPC commutation.

An intelligent technique for fault detection and localization of three-level ANPC inverter with NP connection for electric vehicles

An intelligent technique for detecting and localizing an inverter switch fault or phase fault of a Three-Level Active Neutral Point Clamped (ANPC) inverter is proposed in this research. Moreover, a 3L-ANPC inverter can gain the controllability of EV's power train and not need to be stalled even after the occurrence of the fault. Hence, an efficient fault diagnosis methodology is required to identify the type of phase fault by a Support Vector Machine (SVM), a machine learning model consisting of sets of labeled training data with regression and classification challenges. Finally, when the fault occurs, the location of the switch fault can be identified by a Deep Neural Network (DNN), which consists of layers of neurons between the input and output layers which fuses the feature extraction process with increased accuracy. Thus, the detection and localization of the open-circuit fault of the switches in the ANPC inverter help overcome all single faults, hence gaining its current controllability without stopping the vehicle. The accuracy of fault detection is improved in a precise manner. Finally, the performance of the proposed work is evaluated over other conventional models concerning varied metrics like the accuracy of identification and localization.

A new design of active NPC converter topology with higher voltage gain for solar PV applications

In the low voltage applications, the high gain multilevel inverters has seen more visibility due to the improved harmonic profile with multilevel voltage as well as boosting feature. A boost active neutral point clamped (ANPC) multilevel inverter (MLI) configuration with reduced resource count has been proposed in this paper. The proposed MLI produces 11 levels (11L) voltage with the help of 12 switches of blocking voltage ratings lesser than the peak value of output voltages. For attaining the boosting of 2.5 in output voltage, 4 capacitors are used in the proposed MLI which are inherently self-balanced. The capacitors charging as well as discharging are done by implementing the simple logic of parallel/series connection with the active power DC source. The proposed MLI is implemented and tested in the laboratory at various operating conditions, and the corresponding results and discussion are presented.

A Common-Mode Voltage Elimination Method With Active Neutral Point Voltage Balancing Control for Three-Level T-Type Inverter

Nowadays, the three-level T-type inverters (3LT2Is) are widely employed in applications with high-performance requirements. The 3LT2Is commonly suffer from neutral point voltage (NPV) unbalance and common-mode voltage (CMV) variation. The medium vector pulse width modulation (MVPWM), which generates the reference voltage using medium and V0[OOO] zero voltage vectors, eliminates the CMV variation in 3LT2Is. However, it cannot keep the NPV balance, negatively affecting power quality. This article proposes a hybrid method to simultaneously eliminate CMV variation and guarantee the NPV balance without topological change or extra hardware. The proposed method uses MVPWM when NPV is balanced, eliminating CMV variation. If NPV goes unbalanced, it utilizes novel high/low triangle PWM (H/LPWM) and MVPWM in a hybrid manner to balance the NPV. The H/LPWM, similar to MVPWM, synthesizes voltage using medium and V0[OOO] voltage vectors to maintain the CMV elimination advantage during the NPV balancing process. However, the difference between H/LPWMs and MVPWM switching patterns adjusts the average neutral point current to balance the NPV. Noteworthy that the proposed method provides NPV balancing ability for the entire power factor range. As a result, it is usable for various applications of 3LT2I, such as photovoltaic inverters and motor drives. The proposed method is carrier-based, which reduces the execution time and simplifies the practical implementation. The simulation study and experimental evaluation have been accomplished, and their results demonstrate the effectiveness of the proposed method.

Closed-loop control of six-switch five-level active neutral point clamped inverter for photovoltaic application

Closed-loop control of six-switch five-level active neutral point clamped inverter for photovoltaic application

Common-Mode Current Analysis and Cancellation Technique for Dual Active Bridge Converter Based DC System

This article presents an active neutral point clamped (ANPC)-based parallel dual-active bridge (DAB) architecture which combines <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> cancellation and power sharing in order to reduce electromagnetic interference (EMI) caused by common-mode (CM) current. High <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> associated with wide bandgap devices causes high CM current mainly due to parasitic capacitances. The corresponding conducted EMI can remarkably reduce the reliability of power converters and other onboard systems. This issue becomes worse due to higher dc bus voltage trend in electric vehicles (EV) and other dc systems. Conventional techniques struggle to provide attenuation in a wide frequency range. The problem can also be severe in soft-switched DAB converters as they operate at relatively higher frequencies. In this article, initially, an in-depth theoretical analysis is provided to understand the complimentary <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> events. Various factors causing nonideal <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> cancellation are discussed in detail together with possible solutions. Detailed experimental results are obtained from a 1100 V–150 V parallel DAB system including both the high and low voltage sides at different <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> rates. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> cancellation at lowered <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> rates facilitated by power sharing and small snubbers provide up to 25 dBuA reduction in CM conducted EMI. A comparison with CM chokes is also presented to validate improved attenuation in a wide frequency range.

Brushless Synchronous Generator-Unidirectional Rectifier for Offshore Wind Energy Conversion System

This paper presents the variable speed applications of a recently developed generator named Brushless Induction Excited Synchronous Generator (BINSYG) for offshore wind power applications. The machine is basically a Synchronous generator (SG) with its excitation fed from a three-phase Induction Machine (IM). Both the machines are embedded in the same machine frame and share the same magnetic core. The SG feeds power to the dc grid via a five-level Unidirectional Dual Flying Capacitor Active Neutral Point Converter. The converter is controlled such that the Total Harmonic Distortion (THD) of the current flowing through the stator of SG is below 5% and at unity power factor at SG terminal. The excitation developed by IM-type exciter is adjusted using a new control strategy that is proposed for Voltage Source Inverter, such that BINSYG can operate at wide speed range necessary for Wind Energy Systems (WES). The complete system is controlled without using ac voltage sensors and speed encoders. The proposed WES with its control algorithm is first modelled in MATLAB/Simulink. Further, rapid control prototyping verification in the form of real-time results using OPAL-RT is presented for a small scale (5.5 kVA) BINSYG feeding power to a 750 V dc grid.

Design Procedure and Efficiency Analysis of a 99.3% Efficient 10 kW Three-Phase Three-Level Hybrid GaN/Si Active Neutral Point Clamped Converter

High-efficient and power-dense ac–dc power electronic converters are demanded for a wide range of applications, such as motor drives and active rectifiers. The utilization of wide bandgap devices, such as gallium-nitride (GaN) transistors, is a key feature to improve both the efficiency and the power density of power electronic converters. Owing to the superiority of GaN switches, this article achieves a high-efficiency three-level active-neutral-point-clamped converter. However, using GaN transistors is critically dependent on the layout configuration to achieve smooth switching transient and, as equally important, efficient cooling. Therefore, this article presents layout optimization and considers different layout configurations to achieve a low power loop inductance and as efficient heatsink assembly/performance. Two configurations of the switch boards are built by GaN/Si <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s, and a power loop inductance comparison is presented. Furthermore, a comprehensive loss model is performed to fine-tune the switching frequency from the efficiency and the size point of view. A 10 kW laboratory prototype voltage source converter, including an electromagnetic interference (EMI) filter, is built with the switching frequency of 140 kHz. The efficiency measurement is performed and confirmed the full load efficiency of 99% and peak efficiency of 99.34%. Moreover, the CISPR11 Class A conducted EMI standard is fulfilled.

A new seven‐level ANPC inverter structure with semiconductor device reduction

AbstractAn active neutral point clamped‐type multilevel inverter (ANPC‐MLI) with self‐voltage balancing capability is being suggested for this study. A new switched capacitor cell with eight switches is used for seven‐level generation in the proposed topology. The topology proposed has decreased the power element count with the ability to self‐balancing of capacitor voltages and boosting ability. The distinguishing characteristics of the proposed topology are emphasized and compared with other recent 7L‐SCMLI topologies. Experimental testing on a prototype hardware is conducted to validate the feasibility of the proposed topology.

Detection of Open-Circuit Faults in Multi-Level Hybrid Active Neutral Point Clamped Inverters

Detection of Open-Circuit Faults in Multi-Level Hybrid Active Neutral Point Clamped Inverters

An enhanced implementation of SRF and DDSRF-PLL for three-phase converters in weak grid

Abstract Renewable energy generation systems connected to utility grid require perfect synchronization to grid which is one of the most important issues that needs to be taken into consideration. This paper proposed a hardware-accelerated implementation for the decoupled double synchronous reference frame phase-locked loop (DDSFR-PLL) for grid synchronization in grid-connected converters in weak grid that suffers from phase voltage-unbalance, variable phase and frequency conditions. Since the transformations and filtering of this method is computationally intensive and needs to be executed as fast as possible by the microcontroller unit (MCU) and Due to the presence of other current and voltage regulation loops in the same interrupt service routine (ISR) with high frequency rate, a hardware-based acceleration using the STM32G4x4 MCU built-in filter, filter math accelerator (FMAC) and coordinate rotation digital computer (CORDIC) is used to speed the execution time. This study addresses the description, derivation and implementation of the both DQ-PLL and DDSRF-PLL algorithms. The performance of both pure-software and accelerated implementation is demonstrated, compared and run on a three-level active neutral point clamped (ANPC) converter board. In proposed method, CPU load dropped from 80.5% by using the conventional software implementation to 23.6% (70% load reduction).This reduction in CPU load enables the addition of more features and more advanced current and voltage control algorithms.

Operation and Efficiency Analysis of a Five-Level Single-Phase Hybrid Si/SiC Active Neutral Point Clamped Converter

The ability to improve both the size and efficiency of multilevel single-phase converters is a key to uplift them as an attractive solution for industries, while the high number of switches and complex modulation techniques understandably make them unattractive. Five-level active neutral point clamped (ANPC) converter, due to its inherent advantages such as employing different switching frequencies and using different switch technologies, presents an ideal candidate for study. This article performs a comprehensive analysis of the converter to highlight the advantages of it. This analysis results in a modified hybrid modulation that effectively regulates the neutral point (NP) of the dc link. Consequently, the combination of the topology and the modified modulation make the converter ideal to utilize two different switch technologies—in this article, silicon carbide (SiC) and Si MOSFET. To evaluate the analysis and the effectiveness of modulation, a 2-kW hybrid five-level ANPC is built. The converter current behavior is analyzed to determine the power loss in the filter and switches. The efficiency measurement is performed and compared with the calculated efficiency. There is a close coherency between the measurement and the calculated results and a peak efficiency of 98.4% is achieved.