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Multilevel inverters as the best existing solution for high power/ medium voltage applications have been utilized to incorporate renewable energy sources into electric grid. Solar energy, and fuel-cells as two major sources of power can only provide unidirectional power flow. However, utilizing cascaded H-bridge inverters or other inverters with trinary voltage ratios at the input DC links might cause...
This paper presents a boost switched-capacitor nine-level single-phase inverter, which utilizes flying capacitors and an H-bridge. Besides the boosting ability, the inverter is capable of producing redundant switching states that are used as a degree of freedom in controlling the voltage of DC link capacitor. A comprehensive study of the theoretical aspects of the proposed structure and its practical...
400 Hz inverters, known as Ground Power Units (GPUs), are widely used in aviation and marine industry. Due to their approximately eight times higher fundamental frequency, 400 Hz inverters are much more sensitive to practical delays such as sampling delays, when compared to traditional 50–60 Hz inverters. Conventional controllers designed for 50–60 Hz inverters, therefore, must be redesigned to properly...
This paper presents a method for current controller design in a single phase grid-connected inverter (GCI). The proposed controller addresses the following items: transient performance; steady state tracking; output current distortions and dc; active damping; and start-up transient. The proposed controller is based on various extensions of the linear quadratic regulator (LQR) method and it inherits...
In recent years, sensorless techniques based on HF carrier injection have become very popular as they are capable to estimate rotor position in a wide speed range. They can provide precise control over interior PMSMs without the accompanying need for a position sensor. However, in surface-mounted PMSMs, the estimation of rotor position is only reliable at light loads due to the very small saliency...
This paper presents an online estimation scheme for the identification of distribution power system impedance parameters. The proposed scheme is based on an invasive current injection method. The scheme benefits from a fast and accurate adoptive notch filter for the extraction of the ambient voltages and currents and also a frequency domain least squares estimator. The former enhances the scheme by...
This paper introduces an adaptive harmonic current extraction method for use in Active Power Filters (APFs). The method is capable of detecting a selective order of harmonics. This feature is useful where elimination of certain harmonics is of concern. Moreover, the proposed method can successfully detect and track the variations in the frequency of the signal and extract the time-varying harmonics...
This paper reviews different three-phase harmonic detection techniques. These techniques are to extract voltage/current harmonics for use in grid-connected converters. In particular, this paper compares some of the newly developed three-phase harmonics detection techniques in terms of tracking and extracting time-varying harmonics.
A novel soft-switched AC boost converter with an active snubber is proposed and analyzed. It has a bidirectional active power transfer capability, from low voltage to high voltage or reverse. The energy of switch capacitors is retrieved and delivered to the high voltage side. The snubber provides zero voltage switching (ZVS) for all the main switches in all input voltage and current polarities. The...
This paper is concerned with the investigation of common medium-power isolated bidirectional dc-dc converters (IBDC) which are increasingly being used in many applications such as interfacing renewable energy resources to utility grid, hybrid electric vehicles and UPS systems. Although different varieties of IBDCs have been proposed by researchers, they can be conceptually classified into a few families...
The small-signal or steady-state stability analysis of an autonomous Microgrid and the impact of various parameters are investigated in this paper. This subject has drawn a lot of attention as the penetration of distributed generation is rapidly growing. The control system for an autonomous Microgrid with distributed control is described and the small-signal modeling approach is discussed. The model...
This paper introduces the application of an enhanced phase-locked loop (EPLL) system to the estimation of synchrophasors in a phasor measurement unit (PMU). The major concern is accurate estimation within off-nominal frequency operation of the system. The well-known technique based on discrete Fourier transform (DFT) can provide accurate estimation of the phasors in a three-phase balanced system....
This paper presents a method for designing linear controllers to achieve robust tracking and disturbance rejection properties. Wide range of references and disturbances such as step and sinusoid forms are covered. The proposed control structure comprises a combination of state-feedback and output-feedback strategies. The output-feedback structure is selected based on the internal model principle and...
This paper presents a new design of auxiliary circuit branches for a family of zero-voltage switching phase-shift-modulated dc/dc converters initially reported for fuel cell application. The suggested method applies saturable inductors in auxiliary branches and guarantees zero-voltage switching (ZVS) operation with reduced conduction loss for all the input and load conditions. The suggested approach...
This paper presents an active islanding detection method for grid-connected distributed power generation systems. The proposed scheme is based on an invasive current injection. An impedance estimation module in the frequency domain is introduced to estimate the equivalent impedance seen from the point of common coupling. To do so, a fast and accurate adaptive notch filter is used to extract the ambient...
This paper presents a new controller for power system stabilizer (PSS) that, unlike the conventional linear controllers, consists of both a linear and a nonlinear part. The linear part is properly designed to improve the small-signal stability margin and the damping of the local electromechanical modes. The nonlinear part is then designed to improve transient stability margin of the system without...
This paper presents a control algorithm based on feedback linearization technique for grid-connected three-phase non-dispatchable distributed generation (DG) systems such as a wind or a solar based generator. The power electronic interface is a voltage source inverter (VSI) and the output low-pass filter is an inductance (L) or an inductance-capacitance-inductance (LCL) circuit. The control objectives...
This paper presents a new control method for the Hybrid Active Power Filter (HAPF). HAPFs are composed of passive and active elements and proved to be an attractive solution to mitigate harmonic pollution. They are smaller and less expensive than Active Power Filters (APF), and on the other hand, do not have the well-known drawbacks associated with Passive Power Filters (PPF). Among various topologies...
This paper presents a novel H∞ robust controller for a series-parallel resonant converter. The proposed approach employs an accurate MIMO model of the converter to design the robust controller. The controller introduces a new feedback circuit which exhibits very tight output voltage regulation. The system is also robust against the variations of resonant tank components as well as load variations...
This paper introduces a new three-phase adaptive notch filtering approach for the extraction of harmonic and reactive current components for use in grid connected converters. The main function of this PLL-less method is to provide synchronized harmonic and reactive current components for control purposes. Moreover, this method is capable of detecting a selective order of harmonics. This feature is...
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