AC and dc microgrids (MGs) are key elements for integrating renewable distributed energy resources as well energy-storage systems. In the last several years, efforts toward standardization of these MGs have been made. this sense, paper presents hierarchical control derived from ISA-95 electrical dispatching standards to endow smartness flexibility MGs. The proposed consists three levels: 1) primary is based on droop method, including an output-impedance virtual loop; 2) secondary allows...

This paper deals with the design of output impedance uninterruptible power system (UPS) inverters parallel-connection capability. In order to avoid need for any communication among modules, power-sharing control loops are based on P/Q droop method. Since in these systems accuracy is highly sensitive impedance, novel achieve both stable and proper balance proposed. this sense, a wireless controller designed by using three nested loops: 1) inner loop performed feedback linearization...

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, a novel wireless load-sharing controller for islanding parallel inverters in an ac-distributed system is proposed. This paper explores the resistive output impedance of parallel-connected island microgrid. The control loops are devised and analyzed, taking into account special nature low-voltage microgrid, which line mainly distance between makes intercommunication them difficult....

This paper presents a novel control strategy for parallel inverters of distributed generation units in an AC distribution system. The proposed technique, based on the droop method, uses only locally measurable feedback signals. method is usually applied to achieve good active and reactive power sharing when communication between difficult due its physical location. However, conventional voltage frequency methods achieving load have slow oscillating transient response. Moreover, there no...

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, the control strategy for a flexible microgrid is presented. The presented here consists of several line-interactive uninterruptible power supply (UPS) systems connected in parallel. technique based on droop method to avoid critical communications among UPS units. Thus, obtained operate either grid-connected or islanded mode. A small-signal analysis order analyze system stability,...

In this paper, a method for the parallel operation of inverters in an ac-distributed system is proposed. This paper explores control active and reactive power flow through analysis output impedance its impact on sharing. As result, adaptive virtual proposed order to achieve proper sharing, regardless line-impedance unbalances. A soft-start also included, avoiding initial current peak, which results seamless hot-swap operation. Active sharing achieved by adjusting frequency load transient...

Worldwide, electrical grids are expected to become smarter in the near future. In this sense, there is an increasing interest intelligent and flexible microgrids, i.e., able operate island or grid-connected modes. Black start operation, frequency voltage stability, active reactive power flow control, filter capabilities, storage energy management functionalities for these small grids. This way, can be generated stored consumption points, thus reliability reducing losses produced by large...

Distributed generation inverters have become a key element to improve grid efficiency and reliability, especially during faults.Under these severe perturbations, inverterbased power sources should accomplish low-voltage ride-through requirements in order keep feeding the support voltage.Also, rated current can be required better utilize reactive provisions.This paper presents reference generator capable two objectives: injected currents within safety values, compute references for...

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The injection of low-harmonic current to the electrical grid is nowadays regulated by international standards. In order accomplish these standards, selective harmonic compensation carried out in grid-connected photovoltaic inverters means resonant compensators. This paper gives a systematic design procedure for selecting gains and parameters Other factors considered process include frequency...

Nowadays, the majority of photovoltaic (PV) power sources are connected to public grid. One main connection problems occurs when voltage sags appear in grid due short circuits, lightning, etc. International standards regulate PV systems, forcing source remain during short-time grid-voltage faults. As a consequence, sag, should operate with increasing converter currents maintain injection generated power. This abnormal operation may result nondesired system disconnections overcurrents. paper...

This paper deals with the improvement of transient response and harmonic, subharmonic, dc-offset voltage rejection capability a grid sequence detection scheme based on second-order generalized integrator (SOGI). To perform that, SOGI structure is first analyzed in deep, emphasizing both its tradeoff limits between settling time harmonic attenuation sensitivity to subharmonics voltage. Then, study effect harmonics SOGI-FLL MSOGI-FLL structures introduced. Hence, overcome these problems, new...

This paper explores the impact of output impedance on active and reactive power flows between parallelized inverters operating with droop method. In these systems, a virtual is usually added to control loop each inverter improve sharing, regardless line-impedance unbalances sharing nonlinear loads. The implemented as time derivative current, which makes system highly sensitive current noise loads high slew rate. To solve this, second-order general-integrator (SOGI) scheme proposed implement...

Nowadays, uninterruptible power supply (UPS) systems are in use throughout the world, helping to a wide variety of critical loads, situations outage or anomalies mains. This article describes most common line problems and relationship between these different existing kinds UPS, showing their operation modes as well existent energy storage systems. It also addresses an overview control schemes applied distributed UPS configurations. Finally, it points out applicability such generation,...

The power quality of a three-phase photovoltaic (PV) inverter drastically deteriorates in the presence grid faults with unbalanced voltages. A ripple injected and an increase current harmonic distortion are main noticeable adverse effects produced by this abnormal situation. Several grid-fault control schemes nowadays available for operating under voltage. These usually have extreme characteristics. Some them been conceived to completely avoid during voltage sags, but at expense high...

The resonant current control has been extensively employed to reduce the harmonic distortion in a wide range of grid-connected distributed generation applications, including photovoltaic (PV) inverters, wind and water turbines, fuel-cell inverters. However, performance these systems is deteriorated when utility grid voltage experiences abnormal conditions such as harmonics imbalances. Several advanced solutions have recently introduced cope with this problem but at cost significant increase...

The aim of this work is the application feedback linearization theory to a single-phase shunt active power filter, since technique has been successfully applied other areas electronic. filter linearized by means nonlinear transformation system model, deduced from Tellegen's theorem system. After that, sliding mode controller proposed impose desired dynamic behavior on system, giving robustness and insensitivity parameter variations. Moreover, ensures proper tracking reference signals...

Voltage sags are one of the main problems in transmission and distribution grids with high penetration distributed generation. This paper proposes a voltage support control scheme for grid-connected power sources under sags. The is based on injection reactive current variable ratio between positive negative sequences. controller determines, also, amount needed to restore dropped magnitudes new reference values confined within continuous operation limits required grid codes. These chosen...

Static synchronous compensators have been broadly employed for the provision of electrical ac network services, which include voltage regulation, balance, and stability improvement. Several studies such also conducted to improve operation during unbalanced sags. This paper presents a complete control scheme intended operating under these abnormal conditions. In particular, this introduces two contributions: novel reactive current reference generator new support loop. The has as main feature...

Grid faults are one of the most severe perturbations in power systems. During these extreme disturbances, reliability grid is compromised and risk a outage increased. To prevent this issue, distributed generation inverters can help by supporting voltages. Voltage support mainly depends on two constraints: amount injected current impedance. This paper proposes voltage control scheme that joins features. Hence, strategy injects maximum rated inverter. Thus, inverter takes advantage capacities...

Inverter-based distributed generation plays a vital role in the stability and reliability of new power systems. Under voltage sags, these systems must remain connected to electrical network according stringent requirements grid codes (GCs). Low-voltage ride-through (LVRT) control strategies are becoming common trend electronics research. However, previous studies have not dealt with different possible scenarios presented by GCs, many them focus on very limited number objectives. In this...

This paper presents a robust model-based control in natural frame for three-phase shunt active power filter. For the proposed method, linear converter model is deduced. Then, this used Kalman filter (KF) to estimate system state-space variables. Even though states estimation do not match variables of real system, it has allowed design three sliding-mode controllers providing following features closed-loop system: 1) robustness due fact that specifications are met independently any variation...

This paper presents a continuous control set model-predictive with receding horizon for three-phase voltage-source inverter an LCL filter. In this proposal, reduced model of the converter embedded integrator and Kalman filter are used to obtain inverter-side currents without oscillation. Then, cost function makes use these generate optimum duty cycles space vector modulator. With proposed method, active damping performances, zero state error, reduction computational burden achieved. Compared...

This paper presents an improved variable hysteresis-band current-control in natural frame for a three-phase unity power rectifier. The proposed control algorithm is based on three decoupled sliding-mode controllers combined with independent Kalman filters. use of filters instead nonadaptive state observer improves the quality estimated signals presence noise, increasing immunity loop noisy environments. To reduce drastically computational load algorithm, reduced bilinear model derived which...

This paper presents a new concept in active damping techniques using reduced model of an LCLfiltered grid-connected inverter. The presence the LCL filter complicates design inverter control scheme, particularly when uncertainties system parameters, especially grid inductance, are considered. proposed algorithm is addressed to overcome such difficulties state observer. In this proposal, two three variables obviated from physical model, and only inverter-side current Therefore, can be...