Common-mode Voltage Reduction for Inverters Connected in Parallel Using an MPC Method with Subdivided Voltage Vectors

Joon Young Park,Jiook Sin,Yeongsu Bak,Sung-Min Park,Kyo-Beum Lee 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.3

This paper presents a model predictive control (MPC) method to reduce the common-mode voltage (CMV) for inverters connected in parallel, which increase the capacity of energy storage systems (ESSs). The proposed method is based on subdivided voltage vectors, and the resulting algorithm can be applied to control the inverters. Furthermore, we use more voltage vectors than the conventional MPC algorithm; consequently, the quality of grid currents is improved. Several methods were proposed in order to reduce the CMV appearing during operation and its adverse effects. However, those methods have shown to increase the total harmonic distortion of the grid currents. Our method, however, aims to both avoid this drawback and effectively reduce the CMV. By employing phase difference in the carrier signals to control each inverter, we successfully reduced the CMV for inverters connected in parallel, thus outperforming similar methods. In fact, the validity of the proposed method was verified by simulations and experimental results.

ZSCC suppression method for parallel three‑level inverters based on model predictive control with virtual location vector

Ling Mao,Yuankai Li,Chao Pan,Jianlin Yang,Qin Hu,Yuncong Zheng,Jinbin Zhao 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.4

Parallel three-level neutral point clamped (3L-NPC) inverters are widely used in power conversion applications, such as new energy generation and high voltage inverters. However, the zero-sequence circulating current (ZSCC) between two inverters degrades the whole performance of the system. To suppress the ZSCC in parallel inverters and improve the quality of output current, this study proposes an MPC strategy based on the virtual location vector. First, to reduce the computational burden of MPC, the virtual location vector is constructed by the output current of two inverters so that the control of the parallel inverters is similar to that of a single inverter. Then, the virtual location vector is obtained by using the direct power control method. Finally, the sets of candidate voltage vectors for MPC are determined on the basis of this reference voltage vector and the magnitude of ZSCC. Moreover, the optimal vectors calculated by MPC are assigned to the two inverters. Compared with the traditional MPC strategy, the MPC strategy proposed in this study has better steady state and transient performance with less computational burden. The proposed method is validated in simulation and experimental platforms.

공통 직류 전원을 사용하는 병렬 단일 션트 인버터에서상호 스위칭에 의한 전류 측정 잡음을 저감하는 스위칭 기법

김주안,조용규,최현규 전력전자학회 2024 전력전자학회 논문지 Vol.29 No.1

This study proposes a switching technique to reduce current measurement noise in parallel single-shunt inverters with a common DC link. In typical single-shunt inverters, the current is measured once current ringing is stabilized to minimize the impact of switching noise. However, switching ripples may result in current measurement error of other inverters in parallel inverter systems that share a common DC link. Therefore, inverter switching transition should not be conducted on the sensing duration of both inverters. For this reason, this paper proposes the modification of the switching timing of three-phase inverters by adding offset voltage. The main contribution of this paper is that it eliminates the current measurement noises coming from the switching transition. The performance of the proposed method is validated by the simulation and experimental results.

연료 전지 시스템을 위한 Z-소스 인버터로 구성된 병렬 운전 시스템

김윤호,문현욱,정은진 전력전자학회 2005 전력전자학회 논문지 Vol.10 No.5

본 논문에서는 연료 전지 시스템을 위한 Z-소스 인버터로 구성된 병렬 운전 시스템을 제시 하였다. PWM 방식으로는 Carrier phase shifted SPWM을 적용하였으며 이 방식은 출력 전류의 고조파 성분을 줄일 수 있는 장점을 갖는다. 그러나 이 기법을 Z-소스 인버터로 구성된 병렬 운전 시스템에 적용하는 경우 추가적으로 순환 전류를 발생한다. Z-소스 인버터로 구성된 병렬 운전 시스템이 동작 시 발생하는 순환 전류를 분석하고 순환 전류를 감소시키며, 부하전류에 낮은 고조파 성분을 가질 수 있도록 순환 전류 리액터를 사용하였다. 이에 대한 적합성을 시뮬레이션과 실험을 통해 입증하였다. In this paper, parallel operation systems with Z-source inverters for the fuel cell systems are discussed. The carrier phase shifted SPWM(Sinusoidal Pulse Width Modulation) has an advantage in reducing harmonics of output current. However when this technique applies in parallel operation of Z-source inverters, it additionally produces circulating currents. The circulating current is analyzed and a method to prevent the circulating current is applied to the parallel operation systems of Z-source inverters. To maintain high performance with reduced circulating current in inverter output and low harmonic components in load current, circulating current reactors are used. The proposed approach is verified through simulation and experiment.

Review of Methods for Reducing Circulating Currents in Parallel Connected Modular Inverters

Choi Hye-Won,Lee Kyo-Beum 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.2

Parallel-connected modular inverters are widely used in high-power applications to increase the power capacity of the system. These modular inverters offer convenient maintenance and an adjustable power rating. However, when the inverters share a common DC source and AC bus, a circulating current is generated, which causes output current distortion and system power losses. These harmonic components of circulating current influence the inverter life cycle, and it can limit the power rating of the total parallel-connected inverter. This study analyzes the circulating current according to its causes and reviews the reduction methods. The reduction methods for modular inverters are compared in terms of efficiency, performance, and reliability. The possible approaches for circulating current reduction are categorized into three groups–hardware, control, and modulation. Each reduction method is discussed according to the category. Finally, the performance of the methods is analyzed, and their advantages, disadvantages, and prominent features are highlighted.

Parallel Operation of Trans-Z-Source Inverter

Dongsul Shin,Honnyong Cha,Jong-Pil Lee,Dong-Wook Yoo,Fang Z. Peng,Heung-Geun Kim 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

Recently, there is a strong demand for high power conversion system in power electronics area especially in photovoltaic (PV) power conditioning system (PCS), wind power generation, and fuel cell power generation system. However, there is a limit in increasing power level mainly due to the limitations in switching device’s voltage and current rating. One way to solve this problem is to connect power converters in parallel. Parallel operation of inverter has many advantages such as modularity, ease of maintenance, (n+1) redundancy, high reliability, etc. This paper presents parallel operation of voltage-fed-trans-Z-source inverter. A 2.6 ㎾ prototype inverter is built and tested to verify performances of the proposed inverter.

대전력 3상 유도전동기의 고정자권선을 이용한 전압원 인버터의 병렬운전

김인동,노의철,전성즙 한국정보통신학회 2004 한국정보통신학회논문지 Vol.8 No.4

본 논문에서는 고압 대전력 3상 유도전동기의 고정자 권선을 이용한 전압원 인버터의 병렬운전 방식을 제안한다. 현재 사용되고 있는 대부분의 4극 이상 대전력 유도전동기는 각 상의 권선이 외부에서 접근이 가능하도록 외부단자가 설치되어 있으며, 이들 외부 단자를 이용하여 복수대의 전압원 인버터를 병렬운전 하여 대전력 유도전동기를 구동할 수 있다. 이와 같이 고압 대전력 유도전동기를 복수 개의 전압원 인버터를 병렬 운전하여 구동할 경우, 특정 인버터의 고장발생 시 비록 구동 토오크는 감소될지라도, 나머지 인버터로 시스템을 계속 구동할 수 있어 시스템의 고장대처능력을 향상시킬 수 있다. 또한 병렬 운전되고 있는 각 인버터의 스위칭 동작에 대해 서로 위상차를 갖게 함으로서, 등가 스위칭 주파수를 증가시켜 출력 토오크 리플 감소와 입력 전류 리플 감소, DC Link 커패시터의 크기 감소와 같은 좋은 특성을 얻을 수 있다. 또한 각 인버터로의 전력의 분산에 의해 시스템에서 발생하는 EMI영향을 감소시킬 수 있다. 본 논문에서는 제안한 방식을 컴퓨터 시뮬레이션을 통해 특성을 증명하였다. The parallel operation of voltage source inverters using stator windings of high power three-phase induction motors was proposed in this paper. Most current high power induction motors with more than 4 electric poles have their external terminals installed so that windings of each phase can be approached from the outside. High power induction motors can be driven by parallel-operating several voltage source inverters through these external terminals. This way, in case a certain inverter breaks down, the operation torque will get decreased but the system can maintain its operation with the other inverters, so it can cope more effectively with breakdowns. Moreover, by providing phase difference to the switching movements of each inverter, it can increase equivalent switching frequency, which helps achieve good characteristics such as the reduction in the ripple of output torque, the reduction in the ripple of input current, and the reduction in the size of DC capacitors. Besides, since power is divided into each inverter, it can also decrease the ifluence of EMI occurring in the system. The characteristics of the proposed method were proved through computer simulations in this paper.

Model Predictive Control of Circulating Current Suppression in Parallel-Connected Inverter-fed Motor Drive Systems

Kang, Shin-Won,Soh, Jae-Hwan,Kim, Rae-Young The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.3

Parallel three-phase voltage source inverters in a direct connection configuration are widely used to increase system power ratings. A zero-sequence circulating current can be generated according to the switching method; however, the zero-sequence circulating current not only distorts current, but also reduces the system reliability and efficiency. In this paper, a model predictive control scheme is proposed for parallel inverters to drive an interior permanent magnet synchronous motor with zero-sequence circulating current suppression. The voltage vector of the parallel inverters is derived to predict and control the torque and stator flux components. In addition, the zero-sequence circulating current is suppressed by designing the cost function without an additional current sensor and high-impedance inductor. Simulation and experimental results are presented to verify the proposed control scheme.

An Improved PWM Method of Zero-Sequence Circulating Current Control in Parallel Inverters

Yu. Li,Jianbo Gao,Zhenbin Zhang,Qiwu Wang,Zhongqing Jia,Xintao Li 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

Inverters with a parallel structure are an effective solution to increase the systems power capacity. However, low-frequency zero-sequence circulating current (ZSCC), which degrades the output current quality and increases the power losses, might arise due to the unequal zero-sequence voltages generated by parallel inverters. To overcome this issue, this paper presents an improved pulse width modulation (PWM) method to suppress the zero-sequence circulating current in parallel three-phase inverters. The proposed modulation method can be simply and flexibly embedded into the classical voltage-oriented control (VOC) architecture with minimum modification, and ZSCC can be effectively regulated around zero. The proposed solution removes the zero-sequence loop controller, simplifying the control structure and making it very friendly to implement from the engineering perspective. In the end, experimental results validate the effectiveness of the proposed method.

Model Predictive Control of Circulating Current Suppression in Parallel-Connected Inverter-fed Motor Drive Systems

Shin-Won Kang,Jae-Hwan Soh,Rae-Young Kim 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.3

Parallel three-phase voltage source inverters in a direct connection configuration are widely used to increase system power ratings. A zero-sequence circulating current can be generated according to the switching method; however, the zero-sequence circulating current not only distorts current, but also reduces the system reliability and efficiency. In this paper, a model predictive control scheme is proposed for parallel inverters to drive an interior permanent magnet synchronous motor with zero-sequence circulating current suppression. The voltage vector of the parallel inverters is derived to predict and control the torque and stator flux components. In addition, the zero-sequence circulating current is suppressed by designing the cost function without an additional current sensor and high-impedance inductor. Simulation and experimental results are presented to verify the proposed control scheme.