In this paper, a generalized droop control (GDC) is proposed for grid-supporting inverter based on comparison between traditional and virtual synchronous generator (VSG) control. Both the VSG have their own advantages, but neither nor can meet demand different dynamic characteristics in grid-connected (GC) stand-alone (SA) modes at same time. Rather than using proportional controller with low-pass filter, as control, or fully mimicking conventional parameters active power loop of GDC be...

The coupling between the active and reactive power of droop-controlled inverter is critical in low-voltage microgrid. conventional virtual power-based control strategy can decouple inverter, whereas load probably not equally shared among parallel inverters To tackle this issue, paper proposes an improved method for with a unified rotation angle transformation. Meanwhile, optimal value rigorously derived through investigating relative stability system by innovatively adopting Routh Stability...

To address the unbalanced and harmonic power sharing issue among parallel inverters caused by feeder impedance mismatch in islanded microgrids, an adaptive virtual control method is proposed based on injection of extra small ac signal (SACS) output voltage each inverter. Similar to principle active power-frequency droop, frequency injected droops with power, while produced SACS detected adjust at fundamental negative sequence selected frequencies, which will tune distribution system. When...

The distributed generation (DG) should supply continuous power to the local critical load, even in condition of utility outage. And many efforts have been made for three-phase inverter DG transfer between islanding mode and grid-tied seamlessly. This paper proposes a strategy based on indirect current control DG, which is composed mainly two cascaded feedback loops, i.e., capacitor voltage loop external grid loop, synchronous reference frame. In mode, controlled by regulating voltage. When...

This paper presents a unified control strategy that enables both islanded and grid-tied operations of three-phase inverter in distributed generation, with no need for switching between two corresponding controllers or critical islanding detection. The proposed composes an inner inductor current loop, novel voltage loop the synchronous reference frame. is regulated as source just by operation, controller automatically activated to regulate load upon occurrence islanding. Furthermore,...

This paper presents a stability criterion for three-phase AC distributed power system (DPS). While the source output impedance and load input admittance under synchronous reference frame are generally investigated to predict of DPS, infinity-norms innovatively adopted in proposed improve computational complexity conservatism. Meanwhile, conservatism analyzed compared with existing ones. Furthermore, terminal characteristics studied DPS composed an LC filter boost rectifier, which cover...

Parallel droop-controlled inverters with renewable energy sources are widely employed in islanded ac microgrids, where dynamic interactions among them may cause small-signal stability issues. Since the active power-frequency droop scheme is applied, exist not only bus voltage and transmitted current, but also variable system fundamental frequency. This paper introduces a novel terminal characteristic model for inverter. Besides conventional impedance admittance, new set of characteristics...

LCL resonance complicates the design of a current control loop and can even threaten its stability. Extensive approaches have been proposed to deal with this resonance, among which active damping (AD) schemes based on feedback single filter variable shown be effective cost-efficient. This paper presents study such AD techniques, where generalized approach developing an controller by relating diagram equivalent circuit is proposed. Based approach, forms any one four commonly used variables...

In an islanded microgrid composed of droop-controlled parallel inverters, the system frequency endures deviations as load changes. To compensate for deviation without involving communication infrastructures among distributed generators (DGs), proportional-integral regulator based secondary control (PI-SFC) method has been proposed in literature. However, PI-SFC may incur real power-sharing errors because integrator accumulates disturbances and noise each DG, leading to different compensation...

The three-phase four-leg inverter is very suitable for the high-power uninterruptible power supply application, and load neutral point voltage (LNPV) should meet requirement. In this paper, two factors influencing LNPV were revealed first, which are switching states ratio of inductance to phase ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> ). Then, 16 can be classified into four groups, ones in first second group come minimum amplitude...

Paralleled inverters are widely employed as the power source in AC distributed system, whose output impedance and stability status required impedance-based analysis of whole system. This paper presents an model well a prediction method for three-phase paralleled with master-slave sharing scheme. While is generally modeled under synchronous reference frame (SRF), terminal characteristics individual operating standalone innovatively adopted proposed model, no need knowledge about inner...

This paper presents a power electronics building block (PEBB) design based on 1.7 kV SiC MOSFET modules. The PEBB stage is an H-bridge circuit that can be cascaded to build modular converters. evolution of architectures introduced at the beginning and specifications are given, followed by considerations solutions critical components. In particular, laminated DC bus, differential-mode inductor, smart gate driver, high noise-immunity digital control system, DC-fed auxiliary supply have been...

A universal controller is proposed in this article to operate parallel inverters both grid-connected (GC) state and standalone (SA) ensure seamless transfer between them without reconfiguring the control structure. The mainly composed of frequency-locked-loop three cascaded loops: a grid current loop, capacitor voltage inductor loop. proportional-integral regulator adopted limiter inserted after integrator. In GC state, accurately regulates an individual inverter. When islanding occurs, can...

Due to the mismatched line impedances in islanded microgrids, distributed generation units with conventional droop tend have barely satisfactory reactive power sharing accuracy. To handle this problem, article proposes a virtual impedance tuning method based on successive approximation accurately compensate mismatch among impedances. First, each (DG) unit, an adaptive regulation error between actual output and its reference is established combined Q-V control. Then, these two control schemes...

Grid impedance information occupies a fundamental and crucial position for the operation of grid-tied converters. Consequently, accurate fast extraction grid is vital. The impulse injection method applied under control loop converter, which commonly used to extract linear online, relatively reasonable in terms device cost, measurement speed, simplicity, design flexibility. However, selection parameters mostly depend on rules thumb, without theoretical guidance, leading insufficient accuracy...

Digital control delay is studied as one of the leading factors causing instability in grid-tied voltage source inverter (VSI) systems. However, how this affects small-signal output impedance VSI and change shape further influences system stability are still not clear. This article, for first time, thoroughly analyzes impact on dq-frame operating both single current loop mode dual-loop mode. It found that when considered, a distinct magnitude drop phase rise always exist at high-frequency...

The multiple second-order generalized integrator (MSOGI), which is composed of parallel integrators (SOGI), widely used in grid synchronization and signal extraction, it usually suffers from dc offset issue. In continuous domain, low-pass filter (LPF) can be added to SOGI eliminate the its quadrature channel. However, digital implementation, directly discretized LPF-based methods may not able ac discretization error simultaneously, where steady-state will also introduced by conventional...

This article derives a small-signal terminal characteristic model for the grid-forming inverter with droop-control in synchronous reference ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -) frame, accurately covering dynamics of power controller, voltage and current control loops, all circuit components, where new set characteristics is proposed to characterize fundamental frequency introduced by frequency-active droop scheme. Based...

Abstract A long time of wind vibration will cause fatigue damage to transmission lines. In order reduce the strength line, it is unusually necessary install anti‐vibration devices such as hammers and damping on line. One most important effective ways hammer, which plays a significant role in widely used field control To solve problems poor performance reduction at low frequencies, an hammer with hinge structure designed this paper. The wire transmitted through structure, effect transverse...

This study describes an efficacious and generally applicable synthetic strategy for the incorporation of biologically physiologically prominent difluoromethyl entity into synthetically crucial hydrazone scaffolds with bench-stable easily accessible difluoromethyltriphenylphosphonium bromide. The broad substrate scope, excellent functional group compatibility, feasibility step atom economical one-pot manipulation, environmentally benign mild reaction conditions rendered this methodology...

Reliability remains an issue for the Si/SiC hybrid switch adopting conventional switching strategy of internal SiC MOSFET that turns on earlier, and off later. Such is attributable to overcurrent stress under heavy load operating condition, which adversely affects during gate delay time. To solve this problem without increasing extra power loss, a novel variable-frequency current-dependent combining variable pattern strategy, pulsewidth modulation (PWM) frequency proposed. Variable can avoid...