Impact of Reduced Share of Rotary Frequency Converters in a Low Frequency Synchronous Railway Grid: A Transient Stability Study

2019 ◽  
Author(s):  
John Laury ◽  
Lars Abrahamsson ◽  
Math Bollen
Keyword(s):  
Transient Stability ◽  
Single Phase ◽  
Low Frequency ◽  
Oscillatory Behavior ◽  
Rotational Inertia ◽  
Electrical Machine ◽  
Frequency Converters ◽  
Railway Traffic ◽  
Ac Power ◽  
Three Phase

Most low-frequency AC single-phase railway grids have both power-electronic based Static Frequency Converters (SFCs) and electrical-machine based Rotary Frequency Converters (RFCs) connecting them to the three-phase public grid. Already today, in some such grids, a majority of the power conversion is from SFCs. As railway traffic (and thus power demand) increases, more SFCs are installed for capacity increase, while the number of RFCs remains (almost) constant. Thus, the share of SFCs is expected to increase, and the ratio of installed rotational inertia over installed power to decrease. This paper investigates how different shares of SFCs affect the transient stability of low-frequency AC railway grids when having a mix of RFCs and SFCs converting three-phase AC power to single-phase AC power. Results from numerical simulations of the interactions that occur between converters when and after the grid is subject to a fault are presented. The numerical studies show that with an increased share of SFCs there is an increased oscillatory behavior, for example in the voltage magnitude and active power after fault clearance.

Electromagnetic Property of La0.7Sr0.3MnO3/Ag Composite at High Frequency

2015 ◽  
Vol 655 ◽  
pp. 182-185
Author(s):  
Ke Lan Yan ◽  
Run Hua Fan ◽  
Min Chen ◽  
Kai Sun ◽  
Xu Ai Wang ◽  
...  
Keyword(s):  
High Frequency ◽  
Single Phase ◽  
Low Frequency ◽  
Electromagnetic Property ◽  
High Frequency Range ◽  
Frequency Range ◽  
Free Electron Concentration ◽  
Theoretical Simulation ◽  
Electrical And Magnetic Properties ◽  
Three Phase

The phase structure, and electrical and magnetic properties of La0.7Sr0.3MnO3(LSMO)-xAg (xis the mole ratio,x=0, 0.3, 0.5) composite were investigated. It is found that the sample withx=0 is single phase; the samples withx=0.3 and 0.5 present three phase composite structure of the manganese oxide and Ag. With the increasing of Ag content, the grain size of the samples increases and the grain boundaries transition from fully faceted to partially faceted. The permittivity of spectrum (10 MHz - 1 GHz) and the theoretical simulation reveal that the plasma frequencyfpincrease with Ag content, due to the increasing of free electron concentration, which is further supported by the enhancement of conductivity. While for the permeability (μr'), theμr'decrease with the increasing of Ag content at low frequency range (f< 20 MHz), while at the relative high frequency range (f> 300 MHz), theμr'increased with Ag content. Therefore, the introduction of elemental Ag resulted in a higherμr'at the relative high frequency range.

A Single-Phase / Three-Phase Transformer Designed for Voltage Detection Unit of 400Hz Converter Excitation Regulator

2014 ◽  
Vol 1006-1007 ◽  
pp. 967-971
Author(s):  
Yang Lv ◽  
Jun Hong Zhang ◽  
Jing Hong Zhao
Keyword(s):  
Single Phase ◽  
Response Speed ◽  
Obvious Effect ◽  
Ac Motor ◽  
Ac Power ◽  
Three Phase ◽  
Detection Circuit ◽  
Excitation Regulator ◽  
Filter Capacitor ◽  
Detection Unit

Design a single-phase / three-phase transformer designed for voltage detection unit of 400Hz frequency ship converter excitation regulator. Transformer has asimilar structure to AC motor, but the rotor is fixed, a single-phase AC power pass into the rotor and three-phase alternating current generated in the stator side. The transformer is used to the detection circuit of voltage regulator , so that the filter capacitor can be reduced, thereby reducing the latency of signal feedback and improve the response speed of the excitation regulator. The experimental results show that, the transformer has obvious effect on improving the response speed of the circuit.

scholarly journals Design and Experimental Research of Agricultural Low Power Singlephase Frequency Conversion Control System Based on SPWM

2015 ◽  
Vol 9 (1) ◽  
pp. 490-495
Author(s):  
Chuanlai Yuan ◽  
Lingshuang Kong ◽  
Can Hu ◽  
Weilong Zhou
Keyword(s):  
Low Power ◽  
Power Supply ◽  
Rational Design ◽  
Single Phase ◽  
Frequency Conversion ◽  
Frequency Converter ◽  
Ac Motor ◽  
Ac Power ◽  
Three Phase ◽  
Power Frequency

In the countryside of China, the main power supply mode is 220V single-phase power, which affects the widely application of three-phase agricultural appliances. What’s more, it means a block to the development of modern agriculture. However, frequency converter technique research is focused on three-phase high power frequency conversion technology at present, and there are very few achievements on the agricultural low power single-phrase frequency conversion research. In this paper, considering the difficulty of widely application of agricultural low power three-phase AC motor because it is not easy to obtain the three-phase power supply, a three-phase AC frequency conversion system under the condition of agricultural 220V single-phase AC power is designed, which can achieve the stepless regulation of the voltage amplitude and guarantee the widely use of the three-phase AC motor under the condition of agricultural 220V singlephase AC power. The experimental results show that the system can output the controlled three-phase AC power when the input is 220V single-phase AC power. And the rational design of the system hardware also provides the technical support for the application of agricultural low power frequency conversion.

scholarly journals A Novel Structure of a Power System Stabilizer for Microgrids

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 905
Author(s):  
Jong Ju Kim ◽  
June Ho Park
Keyword(s):  
Power System ◽  
Transient Stability ◽  
Low Frequency ◽  
Pso Algorithm ◽  
Power System Stabilizer ◽  
Response Analysis ◽  
Rotational Inertia ◽  
Small Signal Stability ◽  
Novel Structure ◽  
System Stabilizer

This paper proposes a novel structure of a power system stabilizer (PSS) to improve the stability of synchronous generators (SGs) in microgrids. Microgrids are relatively vulnerable in terms of stability due to their small size and low inertia. The rotational inertia and voltage support of SGs are highly suitable for getting over the vulnerabilities of microgrids, but there exist weaknesses in low-frequency oscillations (LFOs) and limitations of synchronization due to electromagnetic characteristics. Therefore, we study how to accommodate the features of microgrids in the PSS of SGs and further enhance present advantages. The PSS proposed in this paper not only damps out LFOs by conventional lead-lag compensation but also provides additional damping torque according to the magnitude of the perturbation using a synchronous impedance characteristic (SIC). The proposed Lyapunov energy-function-based control strategy can also increase the synchronizing power of the SG to improve transient stability. For performance verification, we use parameters obtained by the particle swarm optimization (PSO) algorithm to compare the existing PSS with the proposed one and analyze them. The effect of the proposed micro-power system stabilizer (μPSS) is analyzed through frequency response analysis, and finally, small-signal stability analysis and the performance of transient stability are verified by time-domain simulation (TDS) on MATLAB/Simulink.

scholarly journals Cascade frequency converters control features

2020 ◽  
Vol 241 ◽  
pp. 37
Author(s):  
A. Vorontsov ◽  
V. Glushakov ◽  
M. Pronin ◽  
Yu. Sychev
Keyword(s):  
High Voltage ◽  
Single Phase ◽  
Power Converters ◽  
Low Voltage ◽  
Frequency Converter ◽  
Frequency Converters ◽  
Three Phase ◽  
In Series ◽  
Load Characteristics ◽  
Active Rectifiers

The structures of systems with high-voltage cascade frequency converters containing multi-winding transformers and low-voltage low-power converters connected in series at each output phase of the load are considered. Low-voltage blocks contain three-phase diode or active rectifiers, DC capacitor filters, single-phase stand-alone voltage inverters and block disconnecting devices in partial modes (in case of failure when part of the blocks are disconnected). The possibilities of operation of cascade converters are determined, equations for correcting tasks to units in partial modes are given, tables of correction of tasks with estimates of achievable load characteristics are proposed. The results of experiments on the model of a powerful installation with a cascade frequency converter are presented, confirming the possibility of ensuring the symmetry of the load currents when disconnecting part of the blocks and the asymmetry of the circuit.  

scholarly journals A Review on Flicker-Free AC–DC LED Drivers for Single-Phase and Three-Phase AC Power Grids

2019 ◽  
Vol 34 (10) ◽  
pp. 10035-10057 ◽  
Author(s):  
Ignacio Castro ◽  
Aitor Vazquez ◽  
Manuel Arias ◽  
Diego G. Lamar ◽  
Marta M. Hernando ◽  
...  
Keyword(s):  
Single Phase ◽  
Power Grids ◽  
Ac Power ◽  
Three Phase ◽  
Led Drivers
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