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This paper proposes a fixed frequency based sliding mode (SM) controller for transformer-less single phase inverter for photovoltaic (PV) application with active power decoupling minimizing the capacitance requirement. Unlike conventional power decoupling techniques in full bridge converters, the proposed technique incorporates a large sinusoidal swing of the half-bridge capacitor voltages and a limited...
This paper deals with the AC and DC dynamic voltage control in a hybrid DC/AC Microgrid (MG) with central and distributed Battery Energy Storage Systems (BESSs), applying a power sharing mechanism between the different devices in the MG. The MG is composed by a multiport transformation center and two fixed frequency 3 phase AC Nanogrids (NGs) coupled to a DC bus through 3-phase Power Electronic Converters...
The appearance of harmonics in the grid voltage is an issue for the generation systems and grid connected consumers. This paper presents the basic control strategy to be implemented in Synchronous Power Control (SPC) based power converters, which contributes to reduce the harmonic content in the voltage by means of injecting different harmonic current to the grid using a separated virtual admittance...
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...
Nowadays, the Modular Multilevel Converter (MMC) based HVDC has been considered as a promising technology to meet the increasing electric power demand. However, constructing new transmission lines becomes more and more difficult because of environmental issues. Consequently, the newly constructed DC lines have to share the right of way with existing AC transmission in close proximity. Meanwhile, as...
In this paper, a three loop control strategy (TLCS) based on decoupled zero voltage switching angle (ZVSA) loop is proposed for a series-series (SS) compensated wireless power transmission (WPT) system. To realize constant current charging for EVs and ZVS operation of primary inverter, variable frequency and phase shift control strategy (VF-PSC) is adopted. However, the control variables that are...
A control scheme using space vector modulation for the modular multilevel matrix converter (MMMxC) without circulating current control is investigated. The circulating current flows spontaneously among all the nine arms to balance capacitor voltage of cells. A small arm inductor is inserted into each arm to suppress the di/dt and peak value of transient arm current at the moment of switching the cells...
Electric Vehicles (EV) have become increasingly popular in recent years and are regarded as an important means to alleviate air pollution problems. The broad connection of EV batteries to the grid along with household scale renewable energy sources penetration creates the need for local unified control systems to support the future smart grid. In this paper, an Energy Storage Management System was...
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...
Frequency control is significant to maintain the stability and reliability of islanded microgrids. Generation side controls, e.g., virtual synchronous generator control and droop control, have been widely adopted to stabilize the frequency of islanded microgrid. However, this is not ideal method due to the capacity limitation and power fluctuation of distributed generation(DG). Meanwhile, energy storage...
Penetration levels of solar photovoltaic (PV) generation on the electric grid have increased in recent years. In the past, most PV installations have not included grid-support functionalities. But today, standards such as the upcoming revisions to IEEE 1547 recommend grid support and anti-islanding functions-including volt-var, frequency-watt, volt-watt, frequency/voltage ride-through, and other inverter...
Modular multilevel converters (MMCs), with the filter-less and transformer-less features, are considered as a promising topology for high-efficiency medium voltage (MV) high voltage (HV) drive systems. However, at low frequencies (< 30 Hz), a large current ripple flowing through the capacitors of each submodule will cause significant capacitor voltage fluctuation. This paper proposes an optimal...
This paper focuses on the control of three-phase brushless asynchronous excitation system (TBAES) of the aircraft wound-field synchronous starter-generator system. Since the closed-loop control of the field current of synchronous starter-generator is hard to achieve, generally, the TBAES is powered by the onboard three-phase power system during the low speed region and cut off one phase of the onboard...
This paper presents a new control strategy for Modular Multilevel Matrix converters where the output frequency is higher then the input frequency. In operating points when ωout ≥ ωin the energy pulsation in the converter cells are dominated by the second harmonic of the input frequency. These energy pulsations can be identified and compensated by inducing additional currents. The results are verified...
This paper presents an isolated DB LLC resonant converter with frequency adaptive phase-shift modulation control which overcomes the unity gain problem of conventional DB converter. The proposed control maintains the Zero Voltage Switching (ZVS) to all switches under all operating voltage and load variations. The control proposed for this circuit based on two control variables: switching frequency...
The four-level Hybrid Clamped Converter (4L-HCC) is emerging as a promising DC/AC converter topology for high-efficiency medium-voltage drives. However, without proper control, the voltage fluctuation of the DC-link capacitors will be excessive, resulting in distorted AC current and stability issue in low frequency operation. In reality, the distorted current makes it impractical for motor drive during...
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...
Grid-connected Voltage Source Inverters (VSIs) equipped with LCL filters are attractive in utility applications for their better power quality features, while the inherent LCL resonance may limit the current control loop bandwidth or even threaten system stability. Simple but effective single-loop current control strategies have been studied for obtaining a stable system, where either the inverter-side...
This paper presents a novel hybrid adaptive droop controller to simultaneously regulate both the AC-side and DC-side parameters for power electronic converters in single-phase Microgrids. The main contribution of this paper is to integrate the AC-side and DC-side controllers. Unlike previously presented control schemes, where the DC-bus is considered as an infinite bus or constant voltage bus, the...
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...
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