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.

Economic Power Dispatch of Distributed Generators in a Grid-Connected Microgrid

Adriana C. Luna,Nelson L. Diaz,Fabio Andrade,Moises Graells,Josep M. Guerrero,Juan C. Vasquez 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Grid-connected microgrids with storage systems are reliable configurations for critical loads which can not tolerate interruptions of energy supply. In such cases, some of the energy resources should be scheduled in order to coordinate optimally the power generation according to a defined objective function. This paper defines a generationside power scheduling and economic dispatch of a gridconnected microgrid that supplies a fixed load and then, the scheduling is enhanced by including penalties in order to increase the use of the renewable energy sources and guarantee a high state of charge in the storage system for the next day. Linear models are proposed for the scheduling which are implemented in GAMS. The microgrid model is obtained deploying MATLAB/Simulink toolbox and then downloaded into dSPACE 1006 platform based on real-time simulation to test the economic dispatch. A compromise between cost and use of renewable energy is achieved.

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.

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.

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.

Fuzzy Droop Control Loops Adjustment for Stored Energy Balance in Distributed Energy Storage System

Nelson L. Diaz,Dan Wu,Tomislav Dragi?evi?,Juan C. Vasquez,Josep M. Guerrero 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

The study of isolated AC microgrid has been under high interest due to the integration of renewable energy resources especially for remote areas, or to improve the local energy reliability. The current trend is oriented to distributed renewable energy sources and their corresponding energy storage system, in order to smooth the variations at the prime energy generator. In this paper, a decentralized strategy based on fuzzy logic is proposed in order to balance the state of charge of distributed energy storage systems in lowvoltage three phase AC microgrid. The proposed method weights the action of conventional droop control loops for battery based distributed energy storage systems, in order to equalize their stored energy. The units are selfcontrolled by using local variables, hence, the microgrid can operate without communication systems. Frequency and voltage bus signaling are used in order to coordinate the operation of the microgrid under different stages for charging batteries. Simulation results show the feasibility of the proposed method.

Improved Direct Power Control for Grid-Connected Voltage Source Converters

Gui, Yonghao,Kim, Chunghun,Chung, Chung Choo,Guerrero, Josep M.,Guan, Yajuan,Vasquez, Juan C. Institute of Electrical and Electronics Engineers 2018 IEEE transactions on industrial electronics Vol.65 No.10

<P>A novel grid voltage modulated direct power control (GVM-DPC) strategy for a grid-connected voltage source converter is proposed to control the instantaneous active and reactive powers directly. The GVM-DPC method consists of a nonlinear GVM controller, a conventional controller (feedforward and PI feedback), and nonlinear damping. The proposed control strategy shows a relationship between DPC and voltage-oriented control methods designed in <TEX>$d$</TEX>-<TEX>$q$</TEX> frame. The main advantage is that the proposed method makes the system be a linear time-invariant system, which enables us to apply various control methods easily. The GVM-DPC guarantees not only the convergence rate but also the steady-state performance of the system. Moreover, it is ensured that the closed-loop system is exponentially stable. Finally, simulation and experimental results using a 2.2-kVA VSC are provided to validate the tracking performance and robustness of the proposed control architecture. In addition, the total harmonic distortion of the current is 1.9<TEX>$\%$</TEX> which is much less than the requirement for grid operation.</P>