Guest Editorial - Special Section on Systems of Power Converters: Design, Modeling, Control, and Implementation

Liu, Wenxin,Guerrero, Josep M.,Kim, Jang-Mok IEEE 2017 IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS - Vol.13 No.5

<P>In this Special Section on Systems of Power Converters: Design, Modeling, Control, and Implementation, we have 11 high-quality papers approved for publication that cover the following three topics. 1) Converter Design and Operation. 2) Subsystem-Level Applications. 3) System-Level Applications. These topics and the corresponding papers are summarized.</P>

A Simplified Control Architecture for Three-Phase Inverters in Modular UPS Application with Shunt Active Power Filter Embedded

Chi Zhang,Josep M. Guerrero,Juan C. Vasquez 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

In this paper, a simplified control architecture, including individual layer control and recover layer control, is proposed for a modular online uninterruptible power supply (UPS) system is presented. The parallel control algorithm of for the DC/AC modules are mainly concentrates on the active power sharing performance due to the existence of the shunt active power filter (APF). APF will deal with the reactive power brought by the nonlinear load to guarantee that all DC/AC modules are faced with a resistive type load. On the other hand, since there is no regulation on the UPS output voltage frequency or phase angle, the recovery layer control is only concerned with the amplitude of the UPS output voltage, which means that the working load of the communication network is reduced by half. Consequently, the reliability of the system is improved. Experimental results are presented in this paper in order to validate the proposed system architecture and control.

A Review of Power Electronics Based Microgrids

Wang, Xiongfei,Guerrero, Josep M.,Blaabjerg, Frede,Chen, Zhe The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.1

The increased penetration of Distributed Energy Resources (DER) is challenging the entire architecture of conventional electrical power system. Microgrid paradigm, featuring higher flexibility and reliability, becomes an attractive candidate for the future power grid. In this paper, an overview of microgrid configurations is given. Then, possible structure options and control methods of DER units are presented, which is followed by the descriptions of system controls and power management strategies for AC microgrids. Finally, future trends of microgrids are discussed pointing out how this concept can be a key to achieve a more intelligent and flexible power system.

Modular Plug’n’Play Control Architectures for Three-phase Inverters in UPS Applications

Chi Zhang,Josep M. Guerrero,Juan C. Vasquez,Carsten Seniger 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

In this paper a control strategy for the parallel operation of three-phase inverters in a modular online uninterruptable power supply (UPS) system is proposed. The UPS system is composed of a number for DC/ACs with LC filter connected to the same AC critical bus and an AC/DC that forms the DC bus. The proposed control is designated in two layers, individual layer and recovery layer. In individual layer, virtual impedance concept is employed in order to achieve active power sharing while individual reactive power is calculated to modify output voltage phases to achieve reactive power sharing among different modules. Recovery layer is mainly responsible for guaranteeing synchronization capability with the utility and voltage recovery. With the proposed control, improved voltage transient performance can be achieved and also DC/AC modules are allowed to be plugged in and out flexibly while controlling the AC critical bus voltage. Detailed control architecture, regarding individual layer and recovery layer, are presented in this paper. Also an experimental setup was built to validate the proposed control approach under several scenarios-case study.

Coordinated Secondary Control for Balanced Discharge Rate of Energy Storage System in Islanded Microgrids

Yajuan Guan,Josep M. Guerrero,Juan C. Vasquez 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

A coordinated secondary control based on a novel autonomous currents sharing control strategy for balanced discharge rate of energy storage systems in islanded microgrid (MG) is proposed in this paper. The coordinated secondary controller is able to regulate the output power of distributed generating (DG) systems according to their state-of-charge by adjusting the virtual resistances of their voltage controlled inverters. This controller can not only provide the faster response and accurate output current sharing control, but also avoid the potential operation failure resulting from the over current and unintentional outage of DGs. Thus, the stability and reliability of islanded MG can be improved. The eigenvalues and root locus with the proposed controller are presented to design the parameters as well as analyzing the system stability. Simulation results based on Matlab/simulink are presented in order to verify the effectiveness of the proposed controller.

A Review of Power Electronics Based Microgrids

Xiongfei Wang,Josep M. Guerrero,Frede Blaabjerg,Zhe Chen 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.1

The increased penetration of Distributed Energy Resources (DER) is challenging the entire architecture of conventional electrical power system. Microgrid paradigm, featuring higher flexibility and reliability, becomes an attractive candidate for the future power grid. In this paper, an overview of microgrid configurations is given. Then, possible structure options and control methods of DER units are presented, which is followed by the descriptions of system controls and power management strategies for AC microgrids. Finally, future trends of microgrids are discussed pointing out how this concept can be a key to achieve a more intelligent and flexible power system.

Modeling, Analysis, and Design of Stationary Reference Frame Droop Controlled Parallel Three-Phase Voltage Source Inverters

Juan C. Vasquez,Josep M. Guerrero,Mehdi Savaghebi,Remus Teodorescu 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

Power electronics based microgrids consist of a number of voltage source inverters (VSIs) operating in parallel. In this paper, the modeling, control design, and stability analysis of three-phase VSIs are derived. The proposed voltage and current inner control loops and the mathematical models of the VSIs were based on the stationary reference frame. A hierarchical control for the paralleled VSI system was developed based on three levels. The primary control includes the droop method and the virtual impedance loops, in order to share active and reactive power. The secondary control restores the frequency and amplitude deviations produced by the primary control. And the tertiary control regulates the power flow between the grid and the microgrid. Also, a synchronization algorithm is presented in order to connect the microgrid to the grid. The evaluation of the hierarchical control is presented and discussed. Experimental results are provided to validate the performance and robustness of the VSIs functionality during Islanded and grid-connected operations, allowing a seamless transition between these modes through control hierarchies by regulating frequency and voltage, main-grid interactivity, and to manage power flows between the main grid and the VSIs.

A New Synchronous Reference Frame-Based Method for Single-Phase Shunt Active Power Filters

Mohammad Monfared,Saeed Golestan,Josep M. Guerrero 전력전자학회 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.4

This paper discusses the design of a novel synchronous reference frame (SRF) method that can extract the reference compensating current for single-phase shunt active power filters (APFs). Unlike previous SRF studies, the proposed method has an innovative feature that does not require a fictitious current signal. Other key features of the proposed strategy include frequency-independent operation, accurate reference current extraction, and relatively fast transient response. The effectiveness of the proposed method is investigated by conducting a detailed mathematical analysis. Results of the analysis confirm the superior performance of the suggested approach. Theoretical evaluations are confirmed by the experimental results.

Dynamics Assessment of Grid-Synchronization Algorithms for Single-Phase Grid-Connected Converters

Yang Han,Mingyu Luo,Josep M. Guerrero 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Several advanced phase-lock-loop (PLL) algorithms have been proposed for single-phase power electronic systems. Among these algorithms, the orthogonal signal generators (OSGs) are widely utilized to generate a set of in-quadrature signals, owing to its benefit of simple digital implementation and low computational burden. Meanwhile, some other techniques have been proposed to enhance system robustness and stability characteristics. In this paper, a comprehensive comparison among the OSG-based PLLs and the advanced single-phase PLLs is presented when the grid voltage undergoes disturbances, and the performance comparison of transient response and disturbance rejection capabilities are presented. Finally, the moving average filter (MAF) is applied to enhance steady state and dynamic response of the delayed-type PLL, derivator-based PLL and the complex-coefficient filter (CCF-PLL) under grid frequency variations, harmonics and white noise contamination scenarios.

Stationary Frame Current Control Evaluations for Three-Phase Grid-Connected Inverters with PVR-based Active Damped LCL Filters

Yang Han,Pan Shen,Josep M. Guerrero 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

Grid-connected inverters (GCIs) with an LCL output filter have the ability of attenuating high-frequency (HF) switching ripples. However, by using only grid-current control, the system is prone to resonances if it is not properly damped, and the current distortion is amplified significantly under highly distorted grid conditions. This paper proposes a synchronous reference frame equivalent proportional-integral (SRF-EPI) controller in the αβ stationary frame using the parallel virtual resistance-based active damping (PVR-AD) strategy for grid-interfaced distributed generation (DG) systems to suppress LCL resonance. Although both a proportional-resonant (PR) controller in the αβ stationary frame and a PI controller in the dq synchronous frame achieve zero steady-state error, the amplitude- and phase-frequency characteristics differ greatly from each other except for the reference tracking at the fundamental frequency. Therefore, an accurate SRF-EPI controller in the αβ stationary frame is established to achieve precise tracking accuracy. Moreover, the robustness, the harmonic rejection capability, and the influence of the control delay are investigated by the Nyquist stability criterion when the PVR-based AD method is adopted. Furthermore, grid voltage feed-forward and multiple PR controllers are integrated into the current loop to mitigate the current distortion introduced by the grid background distortion. In addition, the parameters design guidelines are presented to show the effectiveness of the proposed strategy. Finally, simulation and experimental results are provided to validate the feasibility of the proposed control approach.