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There has recently been a significant interest directed towards residential battery storage systems mainly motivated by high penetration of renewables, the low cost and high efficiency of power electronic devices, and the advancements in the safety and energy density of the batteries, especially Lithium-Ion (Li-Ion) batteries. Furthermore, the possibility for the end user to become a utility-independent...
Static Synchronous Compensators (STATCOMs) are being applied for offshore wind power plants to satisfy the grid codes under both normal operation and grid fault conditions. This paper investigates the performances of Modular Multilevel Cascade Converters (MMCC) for the STATCOM application, with special focus is on asymmetrical Low-Voltage-Ride-Through (LVRT) operation under grid faults. The design...
In order to achieve high efficiency, IPT systems must work under resonance conditions. Since, the coupling coefficient is low (k<0.5) compared to a transformer, the compensation is done separately in the primary and the secondary sides. However, depending on the system, both systems can alter each other, creating pole-splitting or bifurcations. This paper presents a design criterion to ensure that...
Droop control is a widely used technique for load sharing in DC microgrids (MGs). However, it has its limitations due to the MG voltage deviating from its rated level and, more importantly, it suffers from possible poor current sharing accuracy. Voltage drops across coupling line impedances is the main factor that causes these limitations, which is further deteriorated by the virtual impedance introduced...
Capacitor-current-feedback active damping method is commonly used in LCL-filtered grid-connected inverters, which attenuates the resonance peak by emulating a virtual resistor in parallel with the filter capacitor. Taking the digital control delay into account, the emulation component becomes frequency-dependent, and it will turn negative when the filter resonance frequency becomes higher than one-sixth...
Frequency domain passivity theory is used to evaluate harmonic resonance instabilities in a system with multiple grid-tied voltage source converters (VSCs), and subsequently, a stabilizing controller using predictive current control (PCC) method is proposed to prevent such instabilities. The input admittance of VSCs using PCC can achieve passivity almost up to the Nyquist frequency. This research...
An electromagnetic interference (EMI) filter design method for electric vehicle (EV) application is proposed in this paper. By transforming the design problem to an optimization problem, the filter volume, system disturbance level, inverter touch current and filter leakage current are taken into account simultaneously. A topology and order evolution approach is merged into the optimization algorithm...
With rapid increase of photovoltaic (PV) penetration in distribution system, and the fact that distributed generators may involve in voltage regulation according to IEEE standard 1547, it is necessary to check the stability of PV generator integration, especially utility PV farms. To apply generalized Nyquist Criteria (GNC) based on impedances on D-Q frame, output impedances of PV farm is derived...
Because of the differences in line impedances, parallel inverters with conventional droop control will have huge circulating current, which does not flow through the loads. To mitigate the circulating current, the research in this paper finds out that parallel-operated inverters should have the impedance in inverse proportion to their capacities, which is difficult to realize in practice. To meet...
This paper presents the design and experimental demonstration of a method for photovoltaic condition monitoring and hot-spot detection using a real-time adaptive parameter identification approach. The identification algorithm tracks parameters in an equivalent ac circuit model of a PV panel, and uses these parameter estimates to predict when the PV panel is partially shaded or in a hot-spot condition...
To avoid the stability problem of grid connected inverter caused by the conventional phase locked loop (PLL), the direct power control of voltage source inverter in virtual synchronous reference frame without PLL is investigated considering grid voltage disturbance in the paper. Based on the small signal analysis methods, comparison between conventional PLL and no PLL is made. It can be found that...
Instabilities due to mutual interactions among inverters in a grid system are sometimes observed. This paper proposes a stabilization method which adds feed-forward (FF) loop characteristics to improve output frequency impedance characteristics which satisfy the Nyquist stability criterion. The principle is that the output impedance is compulsively made passive with the FF loop characteristics and...
There is an increasing need to model large networks of inverter-based distributed generation due to the limits of existing simulation tools. A deliberate enforcement of intra-feeder coherency between adjacent droop-controlled inverters is a worthwhile objective, as phase angle coherency will allow for a deliberate partitioning of fast and slow dynamics within the network. This partitioning, in turn,...
This paper presents a sinusoidal ripple current (SRC) emulator which superimposes an ac ripple current frequency into a dc charging current in order to produce a sinusoidal ripple current without a ripple current controller. It can be used for several purposes: 1) to analyze the impact of ac ripple current magnitude and frequency on the battery internal characteristics; 2) to determine the parameters...
This paper proposes an algorithm for QRS-complex onset detection in single channel ECG signals based on the first differential of the ECG signal and an adaptive baseline estimation. The proposed algorithm was developed and tested using the Physionet QT Database. A 100% detection rate on the onset of the QRS complex, with a mean error±(standard deviation) of −0.48±(11.26) ms was achieved against the...
Depending on the application, power and energy requirements may differ significantly and, most likely, a single lithium-ion cell will not suffice. Battery packs offer cell interconnections that allow to obtain several possible voltage and discharge current ratings. Typically, the battery packs are designed to meet the specifications of the application within a certain range, and sometimes they are...
A miniaturized independently tuning dual-band multi-mode antenna using postwall slotline (PWS) is proposed and simulated in this work. The antenna consists a stepped impedance slot and a patch on the other side of the substrate, and the patch is attached at the edge of the slot by shorting pins. The stepped impedance slot based on the postwall slotline is actually a dual-mode slotline antenna working...
In this paper, a transmission line (TL) resonator based composite right/left-handed (CRLH) leaky-wave antenna (LWA) is investigated. In order to enhance input impedance bandwidth, bandpass filter synthesis technique is utilized to design matching sections. An example LWA with a fractional bandwidth of 0.4 is designed and fabricated, and the measured results agree well with numerical results.
This paper presents the miniaturization of a three-port power divider for microwave frequency. The size reduction is achieved by the use of a quarter-wave-like transformer (QWLT) implemented by a properly designed conjugately characteristic-impedance transmission line (CCITL). The QWLT has a significantly shorter physical length than the conventional quarter-wave transformer (QWT). A novel condition...
The shift towards modern Power Distribution Systems is by taking advantage of the innovations of modern power systems, under the terms of smart grids, distributed generation, microgrids, and active distribution networks. This paper presents the novel solution in power flow management for smart grid. By combining load flow algorithm and existing Geographic Information Sysstem (GIS) in distribution...
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