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15 pages, 6329 KiB

Open AccessArticle

Predictive Torque Control Based on Discrete Space Vector Modulation of PMSM without Flux Error-Sign and Voltage-Vector Lookup Table

by Ibrahim Mohd Alsofyani and Kyo-Beum Lee

Electronics 2020, 9(9), 1542; https://doi.org/10.3390/electronics9091542 - 21 Sep 2020

Cited by 10 | Viewed by 3024

Abstract

The conventional finite set–predictive torque control of permanent magnet synchronous motors (PMSMs) suffers from large flux and torque ripples, as well as high current harmonic distortions. Introducing the discrete space vector modulation (DSVM) into the predictive torque control (PTC-DSVM) can improve its steady-state [...] Read more.

The conventional finite set–predictive torque control of permanent magnet synchronous motors (PMSMs) suffers from large flux and torque ripples, as well as high current harmonic distortions. Introducing the discrete space vector modulation (DSVM) into the predictive torque control (PTC-DSVM) can improve its steady-state performance; however, the control complexity is further increased owing to the large voltage–vector lookup table that increases the burden of memory. A simplified PTC-DSVM with 73 synthesized voltage vectors (VVs) is proposed herein, for further improving the steady-state performance of the PMSM drives with a significantly lower complexity and without requiring a VV lookup table. The proposed scheme for reducing the computation burden is designed to select an optimal zone of space vector diagram (SVD) in the utilized DSVM based on the torque demand. Hence, only 10 out of 73 admissible VVs will be initiated online upon the optimal SVD zone selection. Additionally, with the proposed algorithm, no flux error is required to control the flux demand. The proposed PTC-DSVM exhibits high performance features, such as low complexity with less memory utilization, reduced torque and flux ripples, and less redundant VVs in the prediction process. The simulation and experimental results for the 11 kW PMSM drive are presented to prove the effectiveness of the proposed control strategy. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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23 pages, 6515 KiB

Open AccessArticle

Open-Circuit Fault Tolerance Method for Three-Level Hybrid Active Neutral Point Clamped Converters

by Laith M. Halabi, Ibrahim Mohd Alsofyani and Kyo-Beum Lee

Electronics 2020, 9(9), 1535; https://doi.org/10.3390/electronics9091535 - 19 Sep 2020

Cited by 10 | Viewed by 2806

Abstract

Three-level converters are the most important technologies used in high power applications. Among these technologies, active neutral point clamped (ANPC) converters are mainly used for industrial applications. Meanwhile, recent developments have reduced losses and increased efficiency by using a hybrid combination of Si-IGBT [...] Read more.

Three-level converters are the most important technologies used in high power applications. Among these technologies, active neutral point clamped (ANPC) converters are mainly used for industrial applications. Meanwhile, recent developments have reduced losses and increased efficiency by using a hybrid combination of Si-IGBT and SiC-MOSFET switches to achieve hybrid ANPC (HANPC) converters. Open-circuit failure is regarded as a common and serious problem that affects the operational performance. In this paper, an effective fault-tolerant method is proposed for HANPC converters to safely re-utilize normal operation and increase the reliability of the system under fault conditions. Sequentially, regarding different topologies with reference to earlier fault tolerance methods which could not be applied to the HANPC, the proposed strategy enables continuous operation under faulty conditions effectively without using any additional devices by creating new voltage references, voltage offset, and switching sequences under the faulty conditions. Consequently, no additional costs or changes are associated with the inverter. A detailed analysis of the proposed strategy is presented highlighting the effects on the voltage, currents, and the corresponding total harmonic distortion (THD). The simulation and experimental results demonstrate the capability and effectiveness of the proposed method to maintain normal operation and eliminate the output distortion. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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21 pages, 8645 KiB

Open AccessArticle

Switch Open-Fault Detection for a Three-Phase Hybrid Active Neutral-Point-Clamped Rectifier

by Sang-Hun Kim, Seok-Min Kim, Sungmin Park and Kyo-Beum Lee

Electronics 2020, 9(9), 1437; https://doi.org/10.3390/electronics9091437 - 3 Sep 2020

Cited by 14 | Viewed by 2998

Abstract

This paper proposes a fault-detection method for open-switch failures in hybrid active neutral-point-clamped (HANPC) rectifiers. The basic HANPC topology comprises two SiC-based metal-oxide-semiconductor field-effect transistors (MOSFETs) and four Si insulated-gate bipolar transistors (IGBTs). A three-phase rectifier system using the HANPC topology can produce [...] Read more.

This paper proposes a fault-detection method for open-switch failures in hybrid active neutral-point-clamped (HANPC) rectifiers. The basic HANPC topology comprises two SiC-based metal-oxide-semiconductor field-effect transistors (MOSFETs) and four Si insulated-gate bipolar transistors (IGBTs). A three-phase rectifier system using the HANPC topology can produce higher efficiency and lower current harmonics. An open-switch fault in a HANPC rectifier can be a MOSFET or IGBT fault. In this work, faulty cases of six different switches are analyzed based on the current distortion in the stationary reference frame. Open faults in MOSFET switches cause immediate and remarkable current distortions, whereas, open faults in IGBT switches are difficult to detect using conventional methods. To detect an IGBT fault, the proposed detection method utilizes some of the reactive power in a certain period to make an important difference, using the direct-quadrant (dq)-axis current information derived from the three-phase current. Thus, the proposed detection method is based on three-phase current measurements and does not use additional hardware. By analyzing the individual characteristics of each switch failure, the failed switch can be located exactly. The effectiveness and feasibility of the proposed fault-detection method are verified through PSIM simulations and experimental results. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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31 pages, 15725 KiB

Open AccessArticle

Experimental Comparisons and Evaluations of Different Types of DC-link Capacitors for VSI-Based Electric Compressors in Battery Electric Vehicle Systems

by Namhun Kim, Changju Park, Sangshin Kwak and Jeihoon Baek

Electronics 2020, 9(8), 1276; https://doi.org/10.3390/electronics9081276 - 8 Aug 2020

Cited by 9 | Viewed by 4417

Abstract

Electric compressor systems for air conditioning operations are an essential part in battery electric vehicle systems, which are not applicable to conventional belt-driven compressors due to no combustion engines. Three-phase voltage source inverters (VSI) and interior permanent magnet (IPM) motors are generally used [...] Read more.

Electric compressor systems for air conditioning operations are an essential part in battery electric vehicle systems, which are not applicable to conventional belt-driven compressors due to no combustion engines. Three-phase voltage source inverters (VSI) and interior permanent magnet (IPM) motors are generally used for electric compressor systems in battery electric vehicles. Direct current (DC)-link capacitors are a critical component in the power converter systems, which affect the cost, size, performances and scale. Metallized polypropylene film capacitors are considered more reliable than conventional electrolytic capacitors for high temperature environments such as electric vehicle applications. This paper presents comprehensive comparisons and evaluations of electric compressors with two types of DC-link capacitors. Based on a 5 kW IPM motor drives and a VSI with a nominal DC voltage of 360 V for electric compressors, performances with electrolytic and film capacitors have been evaluated by experimental tests. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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17 pages, 7782 KiB

Open AccessFeature PaperArticle

A Novel Power Decoupling Control Method to Eliminate the Double Line Frequency Ripple of Two Stage Single-Phase DC-AC Power Conversion Systems

by Saghir Amin, Hyun-Hwa Lee and Woojin Choi

Electronics 2020, 9(6), 931; https://doi.org/10.3390/electronics9060931 - 3 Jun 2020

Cited by 6 | Viewed by 4689

Abstract

In two-stage single-phase inverters, inherent double line frequency ripple is present at both the input and output of the front-end converter. Generally, large electrolytic capacitors are used to eliminate this double line frequency ripple. It is well known that low frequency ripple shortens [...] Read more.

In two-stage single-phase inverters, inherent double line frequency ripple is present at both the input and output of the front-end converter. Generally, large electrolytic capacitors are used to eliminate this double line frequency ripple. It is well known that low frequency ripple shortens the lifespan of capacitors. Hence, the system reliability can get worse. In order to eliminate the double line frequency ripple, additional hardware combined with an energy storage device is required in most of the methods developed so far. In this paper, a novel power-decoupling control method is proposed to eliminate the double line frequency ripple at the front-end converter of two-stage single phase DC/AC power conversion systems. The proposed control algorithm is composed of two loops, a ripple compensation loop and an average voltage control loop, and no extra hardware is required. Since the proposed method does not require information from the phase-locked-loop (PLL) of the inverter, it is independent of inverter control. In order to verify the validity and feasibility of the proposed algorithm a 5 kW Dual Active Bridge (DAB) DC/DC converter and a single-phase inverter are implemented. The effectiveness of the proposed method is verified through the simulation and experimental results. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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21 pages, 10232 KiB

Open AccessArticle

Development of Real-Time Implementation of a Wind Power Generation System with Modular Multilevel Converters for Hardware in the Loop Simulation Using MATLAB/Simulink

by Dong-Cheol Shin and Dong-Myung Lee

Electronics 2020, 9(4), 606; https://doi.org/10.3390/electronics9040606 - 2 Apr 2020

Cited by 10 | Viewed by 4780

Abstract

In this study, we propose a wind power generation system model for operating modular multilevel converter (MMC) in a hardware-in-the-loop simulation (HILS) application. The application of the MMC is a system that connects wind power to a grid through high-voltage direct current (HVDC) [...] Read more.

In this study, we propose a wind power generation system model for operating modular multilevel converter (MMC) in a hardware-in-the-loop simulation (HILS) application. The application of the MMC is a system that connects wind power to a grid through high-voltage direct current (HVDC) in the form of back-to-back connected MMCs, whereas a HILS is a system used to test or develop hardware or a software algorithm with real time. A real-time operation model of the MMC is required to conduct a HILS experiment. Although some studies have introduced the HILS model of MMCs for grid connection using PSCAD/EMTDC, it is difficult to find a study in the literature on the model using Matlab/Simulink, which is widely used for power electronic simulation. Hence, in this paper, we propose a real-time implementation model employing a detailed equivalent model (DEM) using MATLAB/Simulink. The equivalent model of both wind power generation system and MMC are presented in this paper. In addition, we describe how to implement components such as a variable resistor that is not provided in the Simulink’s library. The feasibility of the proposed model is demonstrated with real-time operation of a wind power generation system. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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16 pages, 5449 KiB

Open AccessArticle

Remote-State PWM with Minimum RMS Torque Ripple and Reduced Common-Mode Voltage for Three-Phase VSI-Fed BLAC Motor Drives

by Jaehyuk Baik, Sangwon Yun, Dongsik Kim, Chunki Kwon and Jiyoon Yoo

Electronics 2020, 9(4), 586; https://doi.org/10.3390/electronics9040586 - 30 Mar 2020

Cited by 10 | Viewed by 4265

Abstract

A minimum root mean square (RMS) torque ripple-remote-state pulse-width modulation (MTR-RSPWM) technique is proposed for minimizing the RMS torque ripple under reduced common-mode voltage (CMV) condition of three-phase voltage source inverters (VSI)-fed brushless alternating current (BLAC) motor drives. The q-axis current ripple due [...] Read more.

A minimum root mean square (RMS) torque ripple-remote-state pulse-width modulation (MTR-RSPWM) technique is proposed for minimizing the RMS torque ripple under reduced common-mode voltage (CMV) condition of three-phase voltage source inverters (VSI)-fed brushless alternating current (BLAC) motor drives. The q-axis current ripple due to an error voltage vector generated between the reference voltage vector and applied voltage vector is analyzed for all pulse patterns with reduced CMV of the RSPWM. From the analysis result, in the MTR-RSPWM, a sector is divided into five zones, and within each zone, pulse patterns with the lowest RMS torque ripple and reduced CMV are employed. To verify the validity of the MTR-RSPWM, theorical analysis, simulation, and experiments are performed, where the MTR-RSPWM is thoroughly compared with RSPWM3 that generates the minimum RMS current ripple. From the analytical, simulation, and experimental results, it is shown that the MTR-RSPWM significantly reduces the RMS torque ripple under a reduced CMV condition at the expense of an increase in the RMS current ripple, compared to the RSPWM3. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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18 pages, 8209 KiB

Open AccessFeature PaperArticle

Fault Diagnosis of Open-Switch Failure in a Grid-Connected Three-Level Si/SiC Hybrid ANPC Inverter

by Bong Hyun Kwon, Sang-Hun Kim, Seok-Min Kim and Kyo-Beum Lee

Electronics 2020, 9(3), 399; https://doi.org/10.3390/electronics9030399 - 28 Feb 2020

Cited by 21 | Viewed by 3909

Abstract

A diagnostic method for an open-circuit switch failure in a hybrid active neutral-point clamped (HANPC) inverter is proposed in this paper. The switching leg of the HANPC inverter consists of four silicon insulated gate bipolar transistors and two silicon carbide metal-oxide-semiconductor field-effect transistors [...] Read more.

A diagnostic method for an open-circuit switch failure in a hybrid active neutral-point clamped (HANPC) inverter is proposed in this paper. The switching leg of the HANPC inverter consists of four silicon insulated gate bipolar transistors and two silicon carbide metal-oxide-semiconductor field-effect transistors to achieve higher efficiency and power density compared to conventional neutral-point clamped inverters. When an open-circuit failure occurs in a switching device, the output current is severely distorted, causing damage to the inverter and the connected loads. The proposed diagnostic method aims to detect the open-switch failure and protect the related devices without additional sensors or circuits. The faulty conditions of six different switches are investigated based on the current distortion in the stationary reference frame. By analyzing the individual characteristic of each switch failure, it is possible to detect the exact location of the failed switch in a short period. The effectiveness and feasibility of the proposed fault-diagnostic method are verified using simulation and experimental results. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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12 pages, 4405 KiB

Open AccessArticle

Hardware-Simulator Development and Implementation for Hydraulic Turbine Generation Systems in a District Heating System

by Sung-Soo Jeon, Young Jae Lee, Yeongsu Bak and Kyo-Beum Lee

Electronics 2020, 9(2), 368; https://doi.org/10.3390/electronics9020368 - 21 Feb 2020

Cited by 3 | Viewed by 2897

Abstract

This paper presents not only a hardware-simulator development for hydraulic turbine generation systems (HTGS) in a district heating system (DHS) but also its control strategies and sequence. Generally, a DHS uses a differential pressure control valve (DPCV) to supply high-pressure–high-temperature fluids for customers [...] Read more.

This paper presents not only a hardware-simulator development for hydraulic turbine generation systems (HTGS) in a district heating system (DHS) but also its control strategies and sequence. Generally, a DHS uses a differential pressure control valve (DPCV) to supply high-pressure–high-temperature fluids for customers depending on distance. However, long-term exposure of the DPCV to fluids increases the probability of cavitation and leads to heat loss in an event of cavitation. Therefore, a HTGS was introduced to solve this problem. It performs differential pressure control of the fluids, replaces the DPCV, and converts excess energy wasted by the DPCV to electrical energy. In this paper, the development of a hardware-simulator for HTGSs with a back-to-back converter, which uses two-level topologies, is proposed; moreover, control strategies and sequence used in this design are presented. The performance and validity of the proposed hardware-simulator and its control strategies are demonstrated by experimental results. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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13 pages, 3501 KiB

Open AccessArticle

A Low Cost and Fast Cell-to-Cell Balancing Circuit for Lithium-Ion Battery Strings

by Van-Long Pham, Van-Tinh Duong and Woojin Choi

Electronics 2020, 9(2), 248; https://doi.org/10.3390/electronics9020248 - 3 Feb 2020

Cited by 39 | Viewed by 9737

Abstract

This paper proposes a fast cell-to-cell balancing circuit for lithium-ion battery strings. The proposed method uses only one push-pull converter to transfer energy between high- and low-voltage cells directly for a fast balancing speed. The switch network for selecting a certain pair of [...] Read more.

This paper proposes a fast cell-to-cell balancing circuit for lithium-ion battery strings. The proposed method uses only one push-pull converter to transfer energy between high- and low-voltage cells directly for a fast balancing speed. The switch network for selecting a certain pair of cells is implemented using relays to achieve a low cost. The control circuit is composed of a battery-monitoring IC and a digital signal processor (DSP) to monitor the cell voltage and to protect the batteries. In order to prove the validity of the proposed method, a prototype circuit is built with twelve lithium-ion batteries in a string. The experimental results show that it takes only 50 min to balance twelve lithium-ion batteries during the charge with 89.5% maximum efficiency. The outstanding performance of the proposed cell balancing circuit is verified through its comparison with other methods in terms of several factors, such as the balancing time and the implementation cost. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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16 pages, 7035 KiB

Open AccessArticle

Flux Weakening Control Technique without Look-Up Tables for SynRMs Based on Flux Saturation Models

by Tae-Gyeom Woo, Sang-Hoon Lee, Hak-Jun Lee and Young-Doo Yoon

Electronics 2020, 9(2), 218; https://doi.org/10.3390/electronics9020218 - 27 Jan 2020

Cited by 6 | Viewed by 5902

Abstract

This paper presents a flux weakening algorithm for synchronous reluctance motors (SynRMs) based on parameters estimated at standstill. Recently, flux saturated motors have been studied. Flux saturation models were identified and look-up tables were generated based on the saturation model for maximum torque [...] Read more.

This paper presents a flux weakening algorithm for synchronous reluctance motors (SynRMs) based on parameters estimated at standstill. Recently, flux saturated motors have been studied. Flux saturation models were identified and look-up tables were generated based on the saturation model for maximum torque per ampere (MTPA) and flux weakening operations. The operation with tables would degrade the accuracy of operating points when the table size is not enough. The proposed method implements a flux weakening operation without tables, and the operating points are determined with voltages and currents on operating points. Therefore, the accuracy can be maintained. In addition, the computation time to generate the tables is not needed, so the initial commissioning process can be reduced. The proposed method consists of two parts: the determination of a flux weakening region and the modification of current references. The flux weakening region is determined by the angle between direction vectors along the constant torque and voltage decreasing directions in the d-q axis current plane. After identifying the flux weakening region, the current references are modified for flux weakening according to the direction vector and appropriate magnitude. The direction and magnitude are determined by the operating point of the currents and magnitude of the output voltage, respectively. Using the flux saturation model for SynRMs, the flux weakening direction can be determined accurately. As a result, flux weakening can be performed precisely. The experimental results prove the validity of the proposed method. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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14 pages, 10153 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Low-Speed Performance Improvement of Direct Torque Control for Induction Motor Drives Fed by Three-Level NPC Inverter

by Samer Saleh Hakami, Ibrahim Mohd Alsofyani and Kyo-Beum Lee

Electronics 2020, 9(1), 77; https://doi.org/10.3390/electronics9010077 - 1 Jan 2020

Cited by 11 | Viewed by 3665

Abstract

Classical direct torque control (DTC) is considered one of the simplest and fastest control algorithms in motor drives. However, it produces high torque and flux ripples due to the implementation of the three-level hysteresis torque regulator (HTR). Although, increasing the level of HTR [...] Read more.

Classical direct torque control (DTC) is considered one of the simplest and fastest control algorithms in motor drives. However, it produces high torque and flux ripples due to the implementation of the three-level hysteresis torque regulator (HTR). Although, increasing the level of HTR and utilizing multilevel inverters has a great contribution in torque and flux ripples reduction, stator flux magnitude of induction motor (IM) droops at every switching sector transition, particularly at low-speed operation. This problem occurs due to the utilization of a zero voltage vector, where the domination of stator resistance is very high. A simple flux regulation strategy (SFRS) is applied for low-speed operation for DTC of IM. The proposed DTC-SFRS modifies the output status of the five-level HTR depending on the flux error, torque error, and stator flux position. This method regulates the stator flux for both forward and reverse rotational directions of IM with retaining the basic structure of classical DTC. By using the proposed algorithm, the stator flux is regulated, hence pure sinusoidal current waveform is achieved, which results in lower total harmonics distortion (THD). The effectiveness of the proposed DTC-SFRS is verified through simulation and experimental results. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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15 pages, 4767 KiB

Open AccessArticle

Unified Power Flow Controller Based on Autotransformer Structure

by Hyun-Jun Lee, Dae-Shik Lee and Young-Doo Yoon

Electronics 2019, 8(12), 1542; https://doi.org/10.3390/electronics8121542 - 13 Dec 2019

Cited by 8 | Viewed by 4264

Abstract

This paper proposes a new unified power flow controller (UPFC) topology. A single phase of them system with the proposed topology consists of an N:2 transformer with a center tap at the low-voltage side and a power converter module comprising full- and half-bridge [...] Read more.

This paper proposes a new unified power flow controller (UPFC) topology. A single phase of them system with the proposed topology consists of an N:2 transformer with a center tap at the low-voltage side and a power converter module comprising full- and half-bridge converters. A three-phase system can be implemented with three devices. While the conventional UPFC topology uses two three-phase transformers, which are called series and parallel transformers, the proposed topology utilizes three single-phase transformers to implement a three-phase UPFC system. By using an autotransformer structure, the power rating of the transformers and the voltage rating of switches in the power converter module can be significantly decreased. As a result, it is possible to reduce the installation spaces and costs compared with the conventional UPFC topology. In addition, by adopting a full- and half-bridge converter structure, the proposed topology can be easily implemented with conventional power devices and control techniques. The techniques used to control the proposed topology are described in this paper. The results obtained from simulations and experiments verify the effectiveness of the proposed UPFC topology. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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19 pages, 7323 KiB

Open AccessArticle

Predictive Control Method Based on Adjacent Vector Confinement Technique for a Three-Phase AC-DC Matrix Converter with High Efficiency

by Eun-Su Jun, Hoang-Long Dang and Sangshin Kwak

Electronics 2019, 8(12), 1535; https://doi.org/10.3390/electronics8121535 - 12 Dec 2019

Cited by 1 | Viewed by 2739

Abstract

A model predictive current control method is proposed to reduce switching losses in an AC-DC matrix converter. In the proposed control strategy, several vectors are selected from among all possible switching vectors for a given location of the input current reference. The switching [...] Read more.

A model predictive current control method is proposed to reduce switching losses in an AC-DC matrix converter. In the proposed control strategy, several vectors are selected from among all possible switching vectors for a given location of the input current reference. The switching vector that minimizes the cost function is applied to the converter in the next sampling period. The principle of the proposed method involves clamping the selected switches to stop performing the switching operation to minimize the number of switchings in every sampling cycle. The total efficiency of the AC-DC matrix converter under the proposed strategy is 91.2% whereas that of the conventional strategy is 89.7%. In addition, unity-power-factor operation is guaranteed and smooth and sinusoidal waveforms are achieved. Finally, simulation and experimental results are demonstrated to confirm the validity of the proposed control strategy. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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18 pages, 3790 KiB

Open AccessArticle

A Compromising Approach to Switching Losses and Waveform Quality in Three-phase Voltage Source Converters with Double-vector based Predictive Control Method

by Eun-Su Jun and Sangshin Kwak

Electronics 2019, 8(11), 1372; https://doi.org/10.3390/electronics8111372 - 19 Nov 2019

Cited by 3 | Viewed by 2713

Abstract

A switching losses reduction technique for the model predictive control (MPC) algorithm, which uses double-vector in the three-phase rectifier, is presented. The proposed method controls the output voltage of the rectifier by using reference rectifier input voltages with the offset voltage injection to [...] Read more.

A switching losses reduction technique for the model predictive control (MPC) algorithm, which uses double-vector in the three-phase rectifier, is presented. The proposed method controls the output voltage of the rectifier by using reference rectifier input voltages with the offset voltage injection to reduce the switching losses. One leg with the largest source current among the three legs in the rectifier is clamped to either the positive or negative output voltage in the proposed method. The proposed method calculates the offset voltage on the basis of the future rectifier input voltages obtained by the reference rectifier input voltage, output voltage, and the source currents in every sampling period, so the clamping region in the leg conducting the largest input current is optimally varied depending on the reference rectifier input voltages and the source currents. Therefore, the proposed method can reduce the switching losses of the rectifier regardless of the different source power factor angle. Due to the effects of clamped legs, the quality of the input current waveform inevitably deteriorated. Thus, in the proposed method, double vectors were utilized to avoid degradation of current qualities and achieved compromised performance by reducing switching losses and keeping the current waveform quality. A performance comparison between the conventional method and the proposed method was made to show performance differences. Additionally, the simulation and experiment were conducted to verify the effectiveness of the proposed method. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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21 pages, 9367 KiB

Open AccessFeature PaperArticle

Performance Improvement of a Grid-Connected Inverter under Distorted Grid Voltage Using a Harmonic Extractor

by Sungjoon Cho, Ho-Sung Kang, Kyo-Beum Lee and Ji-Yoon Yoo

Electronics 2019, 8(9), 1038; https://doi.org/10.3390/electronics8091038 - 16 Sep 2019

Cited by 9 | Viewed by 3963

Abstract

This paper introduces an improved current control strategy for a grid-connected inverter system operating under distorted grid voltage conditions. Although existing current controllers for grid-connected inverters have proportional integral gains with suitable bandwidth, low-order harmonic components can be generated by distorted grid voltages. [...] Read more.

This paper introduces an improved current control strategy for a grid-connected inverter system operating under distorted grid voltage conditions. Although existing current controllers for grid-connected inverters have proportional integral gains with suitable bandwidth, low-order harmonic components can be generated by distorted grid voltages. The proposed improved current controller is established in a synchronous reference frame that rotates at harmonic frequency. The input signals for the harmonic current controller should contain only the specific harmonic components requiring suppression. Therefore, the proposed current controller uses a harmonic extractor to distinguish current signals from fundamental and specific harmonic components. The harmonic extractor retains only the relevant harmonic components for individual current controllers with high harmonic signal ratios. This paper introduces two different strategies to extract specific harmonic components for the current controller. The proposed control strategy does not require any additional hardware filter circuits and can be implemented easily by designing a suitable digital filter. When using the proposed method, grid current quality is significantly improved compared to conventional methods that do not include harmonic extractors. The effectiveness of the proposed method is verified through simulations and practical experiments. Full article

(This article belongs to the Special Issue High Power Electric Traction Systems)

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