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The high R/X ratio of distributed lines in low voltage microgrid causes the coupling between the active and reactive power control. Forcing the output impedance to achieve the decoupling through additional virtual inductor impedance loop heavily causes the voltage amplitude drop at the point of common coupling. Such voltage drop deteriorates the microgrid voltage stability. To avoid the problem of...
In order to offer a good power quality for end users in islanded microgrids, the power sharing between distributed generators (DGs) is the first challenge that must be ensured. In this paper, a droop control method based primary control for two parallel single-phase VSIs forming an islanded microgrid is presented. The proposed control consists of two DGs local controllers, where each controller includes...
In this paper, a kind of networked control of power-sharing for inverter parallel operation is presented. To increase the participation of communication and improve the system performance, both autonomous mode and master-slave of communication mode in networked control are investigated. Nevertheless, communication actions may bring some unpredictable outcome due to the negative factors such as time-delay...
This paper presents an approach for upgrading droop control aimed to improve its performance when used for two parallel inverters. The proposed control ensures equal voltage for the two inverters when different power flowing through them which guarantee zero current circulation. To fulfill the voltage regulation, the second inverter (slave) regulates its voltage to follow the master inverter reference...
In this paper, the relationship between real and reactive power sharing in islanded microgrid considering the complex impedance effect is analyzed. It is determined that traditional droop control has drawbacks in achieving accurate power sharing caused by the mismatched feeder line effect. In order to enhance the power sharing accuracy, an adaptive droop control using virtual impedance for islanded...
Presented in this paper is grid current observer-based compensation control for a single-phase grid-connected inverter that is connected to a weak grid. Traditional single-loop PI current control performance suffers in the presence of the grid voltage distortion and grid impedance uncertainty. To compensate for disturbances from the grid side, two different compensation control structures are proposed...
The power decoupling strategies of single-phase Z-source/quasi-Z-source inverter (ZSI/qZSI) to handle the inherent double-line-frequency (2ω) power are overviewed. They are categorized as passive and active power decoupling methods. The former suppresses the 2ω ripple by the impedance network, modified modulation methods, or closed-loop damping control. The latter diverts the 2ω ripple to the compensation...
This paper presents a family of cost-effective magnetically-coupled impedance source inverters for renewable energy systems. The inverters are derived from magnetically-coupled impedance source networks, featuring low cost and no ground leakage current when used in PV system. The numbers of required semi-conductor switches is reduced. More important, the elimination of leakage currents makes it particularly...
The virtual synchronous generator (VSG) is the interface between distribute generator and power grid, which has the inertia and damping characteristics of the synchronous generator. This strategy can effectively control influence of inverters on power grid. In order to reduce the circulating current and power oscillation, this paper proposed a pre-synchronization control strategy which adds the pre-synchronization...
This paper deals with the implementation of a Maximum Constant Boost Control (MCBC) for a 9-Switch z-source power inverter supplying two induction motors. This topology allows greatly reducing the number of power switches, the switching-losses, the volume, and therefore the system cost. In Electric Vehicle (EV) application, a 9-switch power inverter requires a DC-DC converter to boost batteries output...
A photovoltaic inverter control strategy based on the virtual impedance method is proposed, which makes the inverter compensate the harmonic of power grid to achieve the purpose of harmonic suppression while the inverter transmit the active power to the grid. An algorithm of finding the best virtual impedance is designed. The search range of the virtual impedance is determined by estimating the equivalent...
Distributed generation (DG) is connected through three-phase inverter to the microgrid. The virtual power based droop control can guarantee the pure decoupling between active and reactive power irrespective of low-voltage or high-voltage microgrid application if the line-impedance information is known in advance. However, unbalances are commonly existent in practice so that this conventional control...
EMI noise could bring electromechanical damages to the motors as well as reduce the stability of AC traction system. Since the high frequency noises propagate paths are quite complicated compared with fundamental frequency components, the high frequency EMI noise coupled through system's parasitic parameters is difficult to analyze and eliminated. In this paper, a common-mode equivalent circuit as...
This paper presents a new shoot-through control method applicable for an impedance source galvanically isolated DC/DC converter. In impedance source converters, the introduction of shoot-through states increases the switching speed of H-bridge switches about two to three times the switching frequency. This approach reduces the switching transient of all switches of inverters by commutating them once...
This paper introduces a very-high-power-transfer-density GaN-based capacitive wireless power transfer (WPT) system, suitable as one module of a multi-modular WPT system for charging of electric forklifts. This capacitive WPT system achieves very high power transfer density by operating at a high switching frequency (6.78 MHz) using a GaN-based inverter, and by utilizing innovatively designed L-section...
This paper proposed an adaptive impedance control method in multi-bus distributed islanded micrigrid to share reactive power accurately and suppress circulating current. The multi-bus distributed microgrid is more complicated than one-bus because of its different bus voltages and variable structure. To deal with the power sharing problem in multi-bus distributed islanded micrigrid, two methods have...
This paper presents an approach to the implementation of slow-wave transmission lines with high potential for miniaturization. The unit cell of the structure is a symmetric network consisting of a (host) transmission line section loaded with a shunt capacitor at the central plane and two series inductors at the extremes. Due to the presence of two reactive elements in the unit cell (inductor and capacitor),...
Nonlinear loads connected to the microgrid distort the voltage of the Point of Common Coupling (PCC) and the grid current. Therefore, A droop control based harmonic voltage compensation strategy of voltage controlled inverter in islanded/grid-connected mode is proposed in this paper. To compensate the PCC voltage distortion, fundamental and harmonic voltage components are controlled separately in...
The focus of this paper presents a distributed control method based on the gossip communication mechanism that will regulate the voltage of active loads in islanded microgrids. The proposed distributed voltage control (DVC) strategy based on the gossip protocols is fully distributed and by the way of the discrete-time communication; moreover, each active load unit only requires the local voltage and...
This paper presents the limitations of classical controllers in discrete time in reducing the output impedance of a single-phase inverter voltage source for UPS. The controller design methodology for a topology with the feedback of the inductor current and the capacitor voltage of the output L-C filter is proposed. This proposal considers the performance requirements for UPS, established in the standards...
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