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A dual-mode NRZ/PAM-4 differential low-swing voltage-mode transmitter employs a quarter-rate output multiplexing architecture for low-power operation. In NRZ mode, 2-tap feedforward equalization is realized with analog replica-bias tap control that is configurable in high-performance controlled-impedance or energy-efficient impedance-modulated settings. This analog control also allows for efficient...
This paper proposes a grid code for photovoltaic (PV) integration to mitigate overvoltage and voltage variation problems caused by a large amount of PV generation in distribution circuits. According to the simulation results, PV generation causes overvoltage and voltage variation problems in distribution circuits. To mitigate the overvoltage and voltage variation problems due to the high penetration...
This paper addresses the stability challenges that exist in a bidirectional grid connected electric vehicle (EV) charger. The EV charger under consideration comprises of an ac-dc single phase active rectifier stage followed by a dc-dc dual active bridge (DAB) stage. small-signal models suited for stability analysis of this charger are derived. Controller design considerations are discussed in order...
The role of inertia emulation and voltage control is fundamental to support the integration of distributed generation in weak power grids and Virtual Synchronous Machines (VSMs) represent an attractive solution to assume both of these roles. However, VSMs act as voltage sources and this makes it difficult to address power quality issues. Virtual impedances are commonly applied in the literature to...
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 concept of two-terminal active capacitor implemented by power semiconductor switches and passive elements. The active capacitor has the same level of convenience as a passive one with two power terminals only. A control strategy that does not require any external feedback signal is proposed and a self-power scheme for gate drivers and the controller is applied to achieve the...
Microgrid research and development in the past decades have been one of the most popular topics. Similarly, the photovoltaic generation has been surging among renewable generation in the past few years, thanks to the availability, affordability, technology maturity of the PV panels and the PV inverter in the general market. Unfortunately, quite often, the PV installations are connected to weak grids...
The objective of this research is to analyze and evaluate the performance of the proposed shunt-series switched multi-functional grid-connected inverter (SSS-MFGCI) for mitigating unbalanced voltage sag and swell problem in distributed generation system or microgrid. Three quantitative performance evaluation factors, namely fault level factor, rating factor, and grid stiffness factor, are proposed...
Solid state transformers (SSTs) can be interconnected with each other through a distribution feeder to form a smart grid. When the main grid is disconnected, SSTs form an islanded microgrid. With available communications, master-slave microgrid control structure can be adopted. The system-level stability analysis can be simplified by considering only the grid interface stage of the SST. The loop feeder...
This paper introduces a closed-loop control architecture for an impedance control network (ICN) resonant dc-dc converter that regulates the converter's output voltage while achieving soft-switching across wide operating ranges. This architecture is based on enhanced phase-shift control of the ICN converter, in which the inverter and rectifier phase-shifts are simultaneously controlled to regulate...
The droop control technology, which can achieve an autonomous power sharing among distributed resources interface converters, provides the advantages of enhanced system reliability and reduced complexity. However, the reactive power sharing accuracy of the conventional Q — V droop method can be degraded due to its dependence on the line impedances. The Q — V droop control method was proposed to reduce...
Grid-tied Photovoltaic (PV) inverters are required to have harmonics mitigation control to reduce harmonics distortion on the output current caused by the impact of grid background harmonics. In this paper, a decentralized control strategy for reduction of the impact of distorted grid voltage on the AC-stacked PV inverter architecture is proposed. Two control schemes with the selective harmonics mitigation...
Recently, the medium frequency power electronic traction transformer (PETT) has received increased attention in the rail transit applications due to its small size, light weight, more space availability for passengers, multiple interfaces and other additional functionalities. However, the switching frequency is limited by the thermal tolerance of semiconductors which deteriorate as the switching frequency...
One of the major feature of DC microgrids is its high penetration of power electronic converters, as a result, the system inertia becomes a problem. In this paper, an admittance-type droop control with additional capability of introducing virtual inertia to the system. With the proposed method, each energy source will also contribute virtual inertia to the system, thus improving transient response...
This paper presents a proportional harmonic power sharing (PHPS) control scheme to improve the voltage quality at point of common coupling (PCC) and share harmonic power simultaneously for an islanded microgrid. The proposed control strategy employs P+ multiple resonant controller, and P+ plus Q+-based improved droop control scheme to improve the voltage quality at the load bus. Additionally, the...
Harmonic power can be shared by controlling the equivalent harmonic impedance of distributed generation (DG) units in islanded microgrids. This paper firstly reviews several methods for controlling the equivalent harmonic impedance of DGs and adopts the method based on resistive active power filter (R-APF). Then, a droop relationship between the equivalent harmonic impedance of DGs and their remaining...
Single stage power factor corrected (SSPFC) AC-DC converters are attractive in particular applications because they are less expensive than conventional two-stage converters. One of the main drawbacks of SSPFC converters, however, is that their intermediate DC bus voltage varies considerably when used in universal voltage range applications. A new method for reducing the DC bus voltage variation for...
In DC microgrids, constant power loads (CPLs) would lead to a destabilizing effect that may cause the main bus voltage oscillation. Hence, most researcher are exploring the stabilization methods for DC/DC buck converters feeding CPLs. In practical applications, buck converters are always cascaded with LC input filters to prevent the switching harmonics from returning into the source. With the addition...
The proportional power sharing has been identified as an important issue to guarantee reliability on the operation of low voltage AC-Microgrids. However, inaccurate reactive power sharing in scenarios with line impedance mismatches, and slow transient response remain important limitations of most of the conventional power sharing controllers. In this context, an improved method for power sharing control...
Voltage-sensorless control has been investigated for Voltage Source Inverters (VSIs) for many years due to the reduced system cost and potentially improved system reliability. The VSI based Resistive Active Power Filters (R-APFs) are now widely used to prevent the harmonic resonance in power distribution network, for which the voltage sensors are needed in order to obtain the current reference. In...
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