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The continuous integration of renewable energy sources into power systems has led to the construction of large power plants based on power electronics, with power ratings up to hundreds of megawatts, in order to accomodate technologies like solar PV and wind energy. Due to the size of these plants, they must provide support services for the grid and it is necessary to analyze the impact they have...
Hybrid electromagnetic interference (EMI) filters (HEFs) which are composed of an active filter and a passive filter, have been proposed to reduce the size and weight of conventional passive EMI filters. However, accurate models that can be used to predict the stability and performance of HEFs have not been developed. To cope with this, this paper presents a modeling technique for a hybrid common-mode...
This paper presents the analysis of mixed mode noise in an H-bridge PWM converter. Based on the definition of differential mode (DM) and common mode (CM) noise voltage source and noise current and the time domain voltage and current relationship, noise prediction models are proposed in frequency domain for CM, DM and mixed mode (MM) noise with the consideration of system symmetry regarding the noise...
This paper proposes a new control algorithm to tune the input current of the AC-DC converter in an inductive energy harvester, in order to achieve maximum power transfer to a load. The conventional phase regulating method normally achieves maximum power transfer by using the input voltage as the reference. However, in a harvester the internal inductance makes measurement of input voltage inaccessible...
This research proposes a bridgeless rectification circuit for impedance matching and voltage boosting of a Wi-Fi energy harvesting system. The impedance matching is achieved by an LCL T-network in parallel with an inductive branch, and such an arrangement can boost the voltage by combined effect of T-network and bipolarity charging of the output capacitor. The return loss equation and an estimated...
Photovoltaic power plants (PV) are equipped with anti-islanding algorithms, embedded in the converters controller, to avoid the island operation. However, the current trends in the development of the future electrical networks evidence that it is technically feasible and economically advantageous to keep feeding islanded systems under these situations, without cutting the power supply to the loads...
In this paper, an improvement in power sharing for Autonomous Microgrid is well established. All previous studies were based on voltage and frequency droop control to share power between distributed generators. This paper develops a new robust voltage and angle droop control to share power, where its advantage over the common frequency droop is in less frequency variation. The synchronization of Power...
The grid-feeding voltage controlled inverter (GF-VCI) based on droop control is vulnerable to the harmonic voltages of the utility grid. Because of the equivalent impedance of system is small, the slight distorted grid voltage will result in the harmonic component increasing of GF-VCI output currents. Therefore, the reason of generation of distorted grid-feeding current of GF-VCI under the distorted...
In this paper, we introduce a step-down resonant dc-dc converter architecture based on the newly-proposed concept of an Impedance Control Network (ICN). The ICN architecture is designed to provide zero-voltage and near-zero-current switching of the power devices, and the proposed approach further uses inverter stacking techniques to reduce the voltages of individual devices. The proposed architecture...
This paper presents the design procedures of an unity-power-factor AC-DC power converter for wireless power transfer application. This newly proposed AC-DC converter consists of two stages: the PFC front stage uses LC series resonant circuit to perform power factor conditioning and the second stage uses a DC-DC converter to regulate the output voltage. New equations to describe the input impedance...
In this paper, a control scheme to improve load sharing among inverters of different power ratings in an ac microgrid is proposed. The proposed control scheme shapes the output impedance of the inverters independent of the voltage controller parameters and minimizes the requirement of the virtual impedance for proper load sharing. Results show that system stability improves. Simulation and experimental...
The use of the virtual admittance concept for harmonic and/or unbalance compensation in microgrids when multiple inverters operate in parallel is proposed in this paper. The virtual impedance concept has been traditionally used for these purposes. However, one drawback of the virtual impedance is that it can only be applied to distributed generation (DG) units operating in voltage control mode (VSI-VCM),...
Power converter operation on high-impedance grids can result in oscillatory behavior as a result of “self-synchronization” of an inverter's phase detection unit (PDU). This phenomenon is particularly of concern in renewable energy applications and it occurs when the converter's injected current changes the voltage angle at the point-of-common coupling (PCC) and synchronizes to itself through its PDU...
In this work, different current limiting methods for grid forming inverters are presented and theoretically analyzed. A transient non-linear virtual impedance is introduced and compared with the standard current limiting methods in synchronous rotating reference frame. Their performance is evaluated by means of real time simulation for standalone and parallel operation of an inverter with a synchronous...
This paper discusses and analyzes the parallel operation of uninterruptible power supplies (UPS) with instantaneous average current sharing control strategy. The analysis demonstrate that the control method introduces a virtual impedance between the inverters. If the impedance configured as resistive, it will simplify the control strategy, the paper analyzes the stability of the control system by...
An adaptive current-sharing control strategy with virtual circulating impedance for single-phase parallel connected UPS is proposed in this paper. The current-sharing scheme of the paralleled system is developed and the theoretical analysis of the virtual circulating impedance is studied. The impact of the virtual circulating impedance on the stability of the paralleled system is also discussed. Moreover,...
In this paper, a novel design method based on high-order harmonics analysis is proposed to help realize an efficient LCL resonant inverter in IPT systems. The newly derived method takes high-order harmonics into consideration to give accurate description for switching transient, which facilitates the implementation of both ZVS and optimal power factor. In the analysis, the optimal switching current...
In the DC power systems of More Electric Aircraft, the closed-loop controlled electrical motor drives and power electronic converters can be generally regarded as constant power loads (CPLs), and usually lead to negative impedance-related instability. Depending on Brayton-Moser's mixed potential theory, this paper adopts R parallel damping filters to stabilize the CPLs systems, and derives large signal...
A system to emulate railway DC systems is presented in this paper. The emulator is designed to simulate the behavior of railway systems in terms of stray currents and touch voltages. Power electronics circuits are used as variable resistors to simulate the train motion. The emulator provides a test-bed to not only study and analyze the effects of stray currents and touch voltages, but to also evaluate...
In an electrically controlled pneumatic(ECP) brake system, The locomotives of heavy-haul train communicate with cars and supply power for them through the lonworks bus. To guarantee the proper level of uninterrupted power supply for each car, as well as reliable communication between them, a dedicated LiFePO4 battery management system(BMS) is proposed in this paper. Compared with the conventional...
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