Study on Microcomputer Inverse Time Over-Current Protection Algorithm of Underground Low-Voltage Power-System

2011 ◽  
Vol 143-144 ◽  
pp. 8-13 ◽  
Author(s):  
Jun Ying Zhao ◽  
Xing He Ma ◽  
Li Jia ◽  
Gen Xian Zhang
Keyword(s):  
Mathematical Model ◽  
Power System ◽  
Taylor Expansion ◽  
Low Voltage ◽  
Expansion Method ◽  
Time Algorithm ◽  
Look Up Table ◽  
General Mathematical Model

Analysis of general mathematical model and the traditional anti-time algorithm of over-current protection for microcomputer based on the algorithm proposes look-up table and Taylor expansion. To solve the problem of c=0.02 of general anti-time in microcomputer is difficult to implement directly. This paper chooses the Taylor expansion method and selects the general anti-time and thermal over-load (no storage) anti-time for experiment. The experiment proves that the Taylor expansion method can achieve exactly the characteristics of microprocessor-based inverse time.

scholarly journals A DC-side fault-tolerant bidirectional AC/DC converter for power system in integration of low-voltage DC distribution systems

2021 ◽  
Author(s):  
Nikoo Kouchakipour
Keyword(s):  
Mathematical Model ◽  
Power System ◽  
Power Distribution ◽  
Distribution Systems ◽  
Low Voltage ◽  
Short Circuit ◽  
Power Converter ◽  
Software Environment ◽  
Medium Voltage ◽  
Dc Distribution

With the rising potential for the employment of low- and medium-voltage direct-current (dc) electric power distribution systems, most notably for a more efficient integration of plug-in electric vehicles and such other distributed energy resources as photovoltaic (PV) panels, there is a need for robust ac/dc electronic power converters that can interface such dc distribution systems with the legacy alternating current (ac) power system. Thus, this thesis proposes a new single-stage low-voltage three-phase ac-dc power converter that is simple structurally, en- ables a bidirectional power exchanges between the ac and dc distribution systems, and can handle short-circuit faults at its dc as well as ac sides. The proposed converter consists of three legs, corresponding to the three phases of the host ac grid, each of which hosting two full-bridge submodule (FBSM), in an architecture that can be regarded as a special case of the so-called modular multi-level converter (MMC). Thus, at the dc port each FBSM is connected in parallel with a corresponding capacitor, while the ac voltage of each phase is synthesized by the coordinated sinusoidal pulse-width modulation (SPWM) of the two corresponding FBSMs. This architecture allows the generation of low-distortion ac voltage while it also provides the converter with the very important dc fault current blocking capability since, upon the detection of a short circuit across the converter dc port, the switches of the FBSMs are turned off and disallow the flow of any dc current. The thesis also presents a mathematical model for the converter, for analysis and control design purposes. Thus, the control for the regulation of the overall dc-side voltage, as well as those for the regulation of the dc voltages of the FBSMs are devised based on the aforementioned mathematical model and presented with details. It is further shown that the voltage conversion ratio of the proposed converter is the same as that offered by a conventional voltage-sourced converter (VSC), whereas the VSC is vulnerable to dc- side shorts. The proposed converter can be extended to medium-voltage levels by multi- plying the number of FBSMs in each leg. The effectiveness of the proposed converter and its controls is demonstrated through time-domain simulation studies conducted on a topological model of the converter in PSCAD/EMTDC software environment.

scholarly journals A DC-side fault-tolerant bidirectional AC/DC converter for power system in integration of low-voltage DC distribution systems

2021 ◽  
Author(s):  
Nikoo Kouchakipour
Keyword(s):  
Mathematical Model ◽  
Power System ◽  
Power Distribution ◽  
Distribution Systems ◽  
Low Voltage ◽  
Short Circuit ◽  
Power Converter ◽  
Software Environment ◽  
Medium Voltage ◽  
Dc Distribution

With the rising potential for the employment of low- and medium-voltage direct-current (dc) electric power distribution systems, most notably for a more efficient integration of plug-in electric vehicles and such other distributed energy resources as photovoltaic (PV) panels, there is a need for robust ac/dc electronic power converters that can interface such dc distribution systems with the legacy alternating current (ac) power system. Thus, this thesis proposes a new single-stage low-voltage three-phase ac-dc power converter that is simple structurally, en- ables a bidirectional power exchanges between the ac and dc distribution systems, and can handle short-circuit faults at its dc as well as ac sides. The proposed converter consists of three legs, corresponding to the three phases of the host ac grid, each of which hosting two full-bridge submodule (FBSM), in an architecture that can be regarded as a special case of the so-called modular multi-level converter (MMC). Thus, at the dc port each FBSM is connected in parallel with a corresponding capacitor, while the ac voltage of each phase is synthesized by the coordinated sinusoidal pulse-width modulation (SPWM) of the two corresponding FBSMs. This architecture allows the generation of low-distortion ac voltage while it also provides the converter with the very important dc fault current blocking capability since, upon the detection of a short circuit across the converter dc port, the switches of the FBSMs are turned off and disallow the flow of any dc current. The thesis also presents a mathematical model for the converter, for analysis and control design purposes. Thus, the control for the regulation of the overall dc-side voltage, as well as those for the regulation of the dc voltages of the FBSMs are devised based on the aforementioned mathematical model and presented with details. It is further shown that the voltage conversion ratio of the proposed converter is the same as that offered by a conventional voltage-sourced converter (VSC), whereas the VSC is vulnerable to dc- side shorts. The proposed converter can be extended to medium-voltage levels by multi- plying the number of FBSMs in each leg. The effectiveness of the proposed converter and its controls is demonstrated through time-domain simulation studies conducted on a topological model of the converter in PSCAD/EMTDC software environment.

The Generation Principle and Mathematical Models of Double-Enveloping Internal Gear Pairs

2015 ◽  
Author(s):  
Xuan Li ◽  
Bingkui Chen ◽  
Yawen Wang ◽  
Guohua Sun ◽  
Teik C. Lim
Keyword(s):  
Mathematical Model ◽  
Load Capacity ◽  
Geometrical Shape ◽  
Gear Pair ◽  
Numerical Examples ◽  
Proposed Model ◽  
General Mathematical Model ◽  
Meshing Characteristics ◽  
Internal Gear ◽  
Tooth Pair

In this paper, the planar double-enveloping method is presented for the generation of tooth profiles of the internal gear pair for various applications, such as gerotors and gear reducers. The main characteristic of this method is the existence of double contact between one tooth pair such that the sealing property, the load capacity and the transmission precision can be significantly improved as compared to the conventional configuration by the single-enveloping theory. Firstly, the generation principle of the planar double-enveloping method is introduced. Based on the coordinate transformation and the envelope theory, the general mathematical model of the double-enveloping internal gear pair is presented. By using this model, users can directly design different geometrical shape profiles to obtain a double-enveloping internal gear pair with better meshing characteristics. Secondly, to validate the effectiveness of the proposed model, specific mathematical formulations of three double-enveloping internal gear pairs which apply circular, parabolic and elliptical curves as the generating curves are given. The equations of tooth profiles and meshing are derived and the composition of tooth profiles is analyzed. Finally, numerical examples are provided for an illustration.

An integrated low-voltage rated HTS DC power system with multifunctions to suit smart grids

2015 ◽  
Vol 510 ◽  
pp. 48-53 ◽  
Author(s):  
Jian Xun Jin ◽  
Xiao Yuan Chen ◽  
Ronghai Qu ◽  
Hai Yang Fang ◽  
Ying Xin
Keyword(s):  
Power System ◽  
Smart Grids ◽  
Low Voltage ◽  
Dc Power

Low Voltage Bulk Power System Restoration Simulation

1981 ◽  
Vol PER-1 (11) ◽  
pp. 28-29
Author(s):  
Edward J. Simburger ◽  
Francis J. Hubert
Keyword(s):  
Power System ◽  
Low Voltage ◽  
Power System Restoration ◽  
System Restoration ◽  
Bulk Power

Analytical Study of Hydro-Pneumatic Processes for Gorlov's Power System

1994 ◽  
Vol 208 (1) ◽  
pp. 67-70
Author(s):  
A I Ryazanov
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Power System ◽  
Analytical Study ◽  
Model Tests ◽  
Air Pressure ◽  
Pneumatic Power ◽  
Time Required ◽  
The Mathematical Model

This paper describes the aerohydrodvnamics of processes in chambers of Gorlov's hydro-pneumatic power system. The mathematical model is developed to determine the main parameters of the processes: water and air velocities, air pressure in the chamber, the periods of time required to fill and empty the chambers and the output of energy during the cycle. The results obtained are in agreement with experimental data and model tests.

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