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An average power sharing control strategy for parallel operation of voltage source inverter (VSI) based modular Uninterruptible Power Systems (UPSs) is proposed in this paper. The presented method is based on a modified droop control. The proposed method conquers the drawback of conventional droop plus virtual impedance control, and at the same time some challenges in the real applications have been...
This paper proposes a new Inductive Power Transfer (IPT) transmitter configuration tolerant to displacements in the magnetic coupler and in the resonant capacitors. The new configuration uses a variable inductor in the transmitter side to regulate the power supply impedance and achieve zero voltage switch (ZVS) for different vertical and horizontal displacements in the magnetic coupler. The proposed...
Almost all existing relevant literatures are focused on the multi-inverter system that only contains one type of inverter. Till now, the interactions in multi-inverter system consisting of polytype inverters have been not investigated systematically. To fill this gap, the paper is aimed at the stability study of the generic system containing multiple types of inverters. The mathematic model of interactions...
In cascaded-type microgrid, the synchronization and power sharing of distributed generators (DGs) become two new issues that needs to be addressed urgently. In this paper, a unified droop control is proposed and its stability is analyzed in the islanded mode. The proposed scheme can ensure the system stability and accurate power sharing without communication in four-quadrant operations. Finally, simulation...
Enclosure circulation of Gas Insulated Switchgear (GIS) and Very Fast Transient Overvoltage (VFTO) are harmful to many respects of power system, including system's security, stability and economic. The effective inhibition of GIS enclosure circulation and VFTO has attracted wide attention. In this paper, GIS enclosure circulation and transient ground potential has been modeled and analyzed. Firstly,...
In an islanded microgrid, harmonic current is controlled (or shared) by modifying the effective impedance in the path of harmonic current. This effective impedance includes line impedance and the internal impedance of the generation unit. Reported works consider the aforementioned impedances as separate entities and their combined effect in harmonic current flow has not been discussed so far. This...
This paper describes the design of a control strategy for robotic rehabilitation devices, aimed at recovering the motor skills of patients affected by particular diseases that damage the neuromuscular apparatus of the human body. There are two different but related activities in the project here described. At first, a non-linear parameter identification procedure, based on the Recursive Least Square...
As a basic building block, the phase-locked loop (PLL) has been widely used in the grid-connected voltage source inverter (VSI). But it has been shown recently that PLL has adverse impact on stability of grid-inverter system. In a weak grid, the PLL may cause unexpected harmonic, or even instability. In order to overcome this problem, this paper proposes a q-axis voltage feedforward control method...
Ferrite chokes are often applied to suppress electromagnetic interference (EMI) in power converters. In this paper, an improved ferrite choke RLC model and its parameters determination method are proposed. The improved ferrite choke RLC model can overcome the limitation of the existing RLC model in the low frequency band, and the proposed parameters determination method can calculate the values of...
Wireless power transfer (WPT) via magnetic resonance coupling has gathered attentions because of its high transmitting efficiency and robustness to misalignment. The efficiency characteristics of the WPT system are expressed by kQ product, which is given by coupling coefficient and quality factors of a transmitter and receiver. However, a conventional measuring method of the kQ product is quite burdensome...
In this paper multiple feedback(FB) active filter configurations for DM EMI noise in the input side of AC/DC converters has been analyzed using developed models and then their performance was compared over single FB active filters using measurements. First, a single FB active filter circuit model is developed in the open loop and then based on DM EMI noise model of AC/DC converters, a closed loop...
The compliant control of the robot is widely used in the Human-Machine Interface (HMI) and robot bionics. Because the system and the environment are mutually constrained, when the external environment changes, the control environment of the system will change with it, which deteriorates the control performance of the system. This article solves the problem of how to realize the compliant control with...
Recently, resonant inverters have been employed to generate high voltage high frequency AC power for plasma generator of the semiconductor processing equipment. This inverter is beneficial in low switching loss owing to its natural soft-switching capability under inductive load impedance. Generally, the resonant inverter for plasma generator is designed to have inductive load using an impedance matching...
Harmonic resonances around the intersection frequency is triggered with the stability margin decreasing to zero and the system will be unstable with the stability margin reducing to be negative. For suppressing harmonics, the phase difference between the inverter admittance and grid admittance should be lower than 120° at their intersection. Based on this principle, a phase-reshaping strategy aiming...
Fault current limiters (FCLs) are one class of solutions to cope with the upcoming challenges in microgrid protection. Considering high penetration of distributed generations (DGs) in microgrids, the necessity of designing cheap and effective FCL is getting higher. This paper attempts to fill this gap by proposing an embedded FCL operating based on modifying the secondary control of DGs. As this method...
This paper proposes a novel universal control for multi-bus AC microgrid with the capability to operate in both grid-connected (GC) and islanded (IS) modes. The control scheme is based on distributed manner, and the leader-follower consensus protocol is designed. Only few leader distributed generators (DGs) receive the correction signals from the unified mode controller, which is installed at the...
In this paper, magnetically-coupled impedance source (MCIS) three-phase four-switch inverters are introduced for renewable energy applications. This inverter utilizes two single-phase MCIS inverters to obtain a three-phase output, where less component-count is achieved in order to reduce the inverter volume. On the other hand, as a result of the reduced number of switches, the proposed inverter suffers...
The grid-connected inverter with a LCL filter has the ability of attenuating the high-frequency current harmonics. The current distortion caused by harmonics in the grid voltage is difficult to be eliminated. Applying proportion feedforward of the grid voltage can suppress the effect of grid voltage harmonics. However, weak grid is commonly seemed as a voltage source which contains a grid impedance...
The output power of a magnetic resonant coupling wireless power transfer (WPT) system drastically decreases when the distance of couplings coils changes due to impedance mismatch. A maximum power point occurs at only one optimal distance. These characteristics are caused by limitation in design stage. This paper proposes a new impedance tuning method of tracking, for maximum power point, by adjusting...
Small-signal models of impedances for grid-tied converters have recently attracting researchers' attention and shown of great importance in stability analysis. This paper proposes the impedance model in d-q frame for STATCOMs, including dynamics from synchronization, current and voltage loops and reveals the significant features compared to other types of grid-tied converters that the 1) grid impedance...
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