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The electrochemical impedance spectroscopy (EIS) measurement is a method used for offline battery impedance spectrum measurement, which usually requires a specialized and costly equipment. Recent work presented an online method to measure the AC impedance of batteries by utilizing the DC-DC power converter that usually follows the battery for regulation purposes. In this method, the duty cycle of...
The ever-increasing number of data centers requires huge amounts of electrical energy and the amount of renewable energy, of which only a fraction is renewable energy, requiring a considerable amount of additional combustion or nuclear power plants. To minimize the waste of energy and further reduce the energy costs of a modern data center, high conversion efficiencies are sought. This paper proposes...
In this paper, a new DSC-PLL (Delayed Signal Cancellation Phase Locked Loop) with FLL (Frequency Locked Loop) based on RDFT(recursive discrete fourier transform) method is proposed for coping with frequency variation. This method shows significant performance improvement for detection of fundamental positive sequence component voltage when the grid voltage is polluted by grid harmonics and frequency...
Harmonic Quasi Resonant (HQR) control is widely adopted to suppress the harmonic currents for LCL-filtered inverters in stiff grid. However, inverters with HQR control may observe instability when the point of the common coupling (PCC) behaves uncertain impedance or the HQR control frequency is out of the bandwidth of the system control loop. Besides, it could not effectively eliminate the harmonics...
An advanced service provided by the Smart Transformer (ST) is the decoupling between the Medium Voltage (MV) and Low Voltage (LV) grids. In the LV side, the ST can modify the waveform's frequency in order to interact with the droop controllers of the local generators to control the power demand among the sources without affecting the MV grid. However, most of the existing controllers for power converters...
In this paper we present a distributed control method for minimizing the operation cost in DC microgrid based on multiagent system. Each agent is autonomous and controls the local converter in a hierarchical way through droop control, voltage scheduling and collective decision making. The collective decision for the whole system is made by proposed incremental cost consensus, and only nearest-neighbor...
With the increasing adoption of renewable energy sources into power grids, the issue of voltage and frequency fluctuation of the network becomes a more critical problem that needs to be resolved urgently. The so-called demand-side management (DSM) of power system provides the opportunity for the prospective grids to intelligently balance the power supply and consumption. As one of the crucial roles...
Nowadays unbalanced voltage and harmonic distortion are in the majority of the power quality problems in wind energy conversion systems (WECS). To alleviate the impact registered by unbalanced and harmonic distortion, a new circuit topology comprising a dynamic voltage restorer (DVR) and an active power filter (APF) is presented. A frequency shifting technique based on coordinate transformation is...
The topology of parallel three-phase voltage source inverters (VSIs) has been widely utilized to raise system power rating, but zero-sequence circulating currents (ZSCCs) are generated by control effect and hardware parameter differences. ZSCCs could lead to current distortion and impact the system stability. The model predictive control (MPC) method has been applied to the inverters to get high robustness,...
The three-level T-type inverter has outstanding performances and better in the switching device selection than a two-level inverter. However, the problem of common-mode voltages and neutral-point potential (NP) unbalance is generated. This paper proposes a model predictive control method for reducing the common mode voltage and balancing the neutral-point potential (NP). Based on the relationship...
Safe start-up procedure is critical for reliable operation of power converters. The challenges in start-up schemes of high-frequency (HF) transformer link inverters involve pre-charge of the capacitors without significant inrush currents and over-voltages. The pre-charge is normally followed by enabling of the closed-loop control. The over-voltage or inrush current problems in conventional start-up...
The instantaneous output power of the two-stage single inverter pulsates at twice the output voltage frequency, generating second harmonic current (SHC) in the input dc voltage source and the front-end dc-dc converter. To eliminate the SHC, a second harmonic current compensator (SHCC), whose input current is controlled by the improved one-cycle-control (OCC) proposed in this paper, is applied to compensate...
For photovoltaic inverters in islanded microgrids, droop control is a preferable strategy due to its attractive ability in bus voltage regulation and load sharing without additional communication system. However, in islanded microgrids without redundant storages, further realization of power balance between droop controlled PV sources and dynamic loads, which is beneficial to enhance PV sources penetration...
This paper proposes a topology based on bus clamping modulation and zero-voltage-transition (ZVT) technique to realize zero-voltage-switching (ZVS) for all the main switches of the full bridge inverters, and inherent ZVS and/or ZCS for the auxiliary switches. The advantages of the strategy include significant reduction in the turn-on loss of the ZVT auxiliary switches which typically account for a...
Many T8 LED tubes are currently available in the market; however, the majority of commercial products are passive converters, so the lamp current is not well controlled. This paper presents a low voltage, current-fed Buck converter for a T8 LED tube application. A very simple control method with zero-crossing synchronization is proposed; the operation of the circuit is described, and the performance...
In this paper, a method of maintaining high power conversion efficiency across the entire load range of a three-phase micro-inverter is proposed. The proposed control method substantially increases the conversion efficiency at light loads by minimizing switching losses of semiconductor devices as well as core losses of magnetic components. This is accomplished by entering a phase skipping operating...
The paper proposed a multi-port active bridge (MAB) converter applied to household energy router (ER), where a multi-winding high-frequency transformer is used for the isolation and energy redistribution. The ER can provide both DC and AC ports with adjustable voltages, thus can be used for various distributed renewable generations and energy storage access. This work also provides simplified equivalent...
DC microgrids are becoming popular in distribution systems based on its higher reliability and system efficiency. DC bus signal (DBS) control as a common control strategy was widely used in dc microgrids, in which, control mode of each power electronic converter is triggered by monitoring the dc voltage variation to keep the power balance of the dc microgrid. Most of the dc microgrid stability analysis...
Voltage-controlled inverters have been widely used in distributed generation due to their flexibility and smooth transition between grid-connected and islanded modes. However, in the grid-tied mode, the inherent coupling between active and reactive power will challenge the independent control of active power and reactive power, and therefore deteriorate system performance. To deal with this issue,...
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