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In distribution network, with the installed of photovoltaic (PV), bought many problems. One of the most concerned problems is the overvoltage in the terminal bus of distribution network. It is caused by the reverse power flow which brought out by the increase of the PV sources penetration. In this paper, an improved PQ-Q (V) control strategy is proposed to alleviate such problem. The economic performance...
In this paper, a 5kW wireless electric vehicles (EV) charger is introduced and modeled in time-frequency domain. Base on the function of the charging current, two current control methods are discussed. It is found that the DC-link voltage control can make the voltage source inverter (VSI) work under soft switching mode but the adjustable range of the charging current is limited. The phase shift control...
This paper proposes a novel seamless transfer method for microgrid connected fuel cell inverters (FCIs) between voltage source and current source modes. In order to protect the fuel cell, the FCI output power should be restricted when the microgrid frequency is greatly disturbed. In this sense, the FCI is transfered from voltage source mode to constant current source mode. Meanwhile, the FCI is transfered...
China Machinery Industry Standard (CMIS) GB/T 12326-2008 prescribed in the islanded operation mode, microgrid inverter (MGI) output voltage dynamic transient range is less than 10% when the resistive load is switched rapidly between 0% and 100%. The three-loop power virtual synchronous generator (VSG) control methods are commonly used in MGI units to share the loads among the parallel MGIs. However,...
With high power Virtual Synchronous Generator (VSG)-based Voltage Source Converter (VSC) and low switching frequency, time delay has become a big issue affecting VSC stability and dynamic response in islanded mode. In this paper, effect of time delay on output impedance is analyzed and a hybrid derivative feedback control is proposed to improve system stability and dynamic response. First step, derivative...
The adoption of virtual synchronous generation (VSG) control can maintain the stability of voltage and frequency in power electronic interfaced mircogrid. In this paper virtual impedance is added to the VSG control strategy in order to improve the system control performance in resistive-inductive line impedance, the influence of virtual impedance on VSG system stability and dynamic performance is...
The three-loop power virtual synchronous generator (VSG) control methods are commonly used in microgrid inverter (MGI) units to share the loads among the parallel MGI units. In order to achieve stable operation of the MGI units under paralleled or grid-connected mode, a droop synchronization controller is designed in this paper. The difference of phase and amplitude between different MGI units is...
Microgrid should be operated in both grid-connected and islanded mode to ensure high voltage quality and reliability. In the case of continuous uninterrupted power supply, seamless transfer is important between the two modes,and synchronization of the voltage of the point of common coupling (PCC) and utility grid should be finished first to achieve the goal. In this paper varies of synchronization...
In micro grid, the voltage and frequency will fluctuate with the switching of large-power electric load. With inverter control of energy storage systems,both active and reactive power pumped into the utility grid can be controlled which could achieve the stabilizing effect of voltage and frequency. This paper addresses active and reactive power control strategies used in energy storage system to eliminate...
Compared to L-type filter, LCL-type filter have resonance frequency point, consequently reduce the reliability of the VSC converter. The general control strategy with passive damping or active damping can improve the stability of the converter, but it will bring extra loss, and need more sensors. This paper compare and analysis the performance of LCL converter controller with different feedback variables...
The single-mode overmodulation strategy of matrix converter is put forward for the lower voltage transfer ratio. Single-mode overmodulation strategy and its effect on increasing voltage transfer ratio are analyzed theoretically, and the simulation model of the strategy is set up. Theoretical analysis and simulation results show that the proposed strategy can make the voltage transfer ratio rise to...
To solve the problem caused by the inherent design of AC motor that 20%~40% energy of traditional escalator goes to waste in vain in the form of heat, this paper puts forward to the best control project of the escalator energy-saving control-adopting instantaneous detect technology, single-chip control, intelligent control system with speed control and voltage control and frequency converter, based...
This paper presents an analysis of a shunt active power filter (SAPF) for harmonic and reactive current compensation. This filter is used in wind energy systems that uses a permanent magnet synchronous generator (PMSG). The system uses supply current measurements instead of load current measurements, therefore, harmonic and reactive current measurements are not required. This simplifies the control...
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