scholarly journals A Five-Level Current-Source Inverter for Grid-Connected or High-Power Three-Phase Wound-Field Synchronous Motor Drives

2016 ◽  
Vol 6 (5) ◽  
pp. 1139-1148
Author(s):  
S. Mohamadian ◽  
M. H. Khanzade
Keyword(s):  
Power Factor ◽  
High Power ◽  
Power Plants ◽  
Short Circuit ◽  
Current Source ◽  
Harmonic Distortion ◽  
Operating Conditions ◽  
Hydro Power ◽  
Torque Pulsations ◽  
Voltage Clamping

Simple converter structure, inherent short-circuit protection and regenerative capability are the most important advantages of current-source inverters (CSI’s) which have made them suitable for medium-voltage high-power drives. Usually in grid-connected gas turbine generators or pumped storage hydro power plants, efficient and reliable current-source load-commutated inverters (LCI’s) with thyristor switches are employed. Also, this type of CSI is widely used in very large drives with power ratings of tens of megawatts to supply wound-field synchronous motors (WFSM’s). However, LCI’s suffer from some disadvantages such as large torque pulsations, poor power factor, and start-up criticalities. In this paper, a novel multilevel-based CSI is proposed. The proposed converter consists of one LCI and one CSI bridge with self-turn-off switches along with a voltage clamping circuit. The CSI switches are forced commutated; hence, a voltage clamping circuit is employed to limit voltage spikes caused by current variations in inductive paths during commutation transients. Drastic reduction in harmonic distortion of stator current and improved fundamental power factor are achieved by the proposed topology. In addition, torque pulsations are reduced remarkably for normal and starting operating conditions. Comprehensive analysis of the proposed structure is presented and the design of converter components is elaborated.

scholarly journals Effect of Symmetrically Switched Rectifier Topologies on the Frequency Regulation of Standalone Micro-Hydro Power Plants

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3201
Author(s):  
Henry Bory ◽  
Jose L. Martin ◽  
Iñigo Martinez de Alegria ◽  
Luis Vazquez
Keyword(s):  
Power Factor ◽  
Power Plants ◽  
Reactive Power ◽  
Alternating Current ◽  
Frequency Regulation ◽  
Hydro Power ◽  
Major Energy Source ◽  
Hydro Power Plants ◽  
Electronic Load ◽  
Ac Converters

Micro-hydro power plants (μHPPs) are a major energy source in grid-isolated zones because they do not require reservoirs and dams to be built. μHPPs operate in a standalone mode, but a continuously varying load generates voltage unbalances and frequency fluctuations which can cause long-term damage to plant components. One method of frequency regulation is the use of alternating current-alternating current (AC-AC) converters as an electronic load controller (ELC). The disadvantage of AC-AC converters is reactive power consumption with the associated decrease in both the power factor and the capacity of the alternator to deliver current. To avoid this disadvantage, we proposed two rectifier topologies combined with symmetrical switching. However, the performance of the frequency regulation loop with each topology remains unknown. Therefore, the objective of this work was to evaluate the performance of the frequency regulation loop when each topology, with a symmetrical switching form, was inserted. A MATLAB® model was implemented to simulate the frequency loop. The results from a μHPP case study in a small Cuban rural community called ‘Los Gallegos’ showed that the performance of the frequency regulation loop using the proposed topologies satisfied the standard frequency regulation and increased both the power factor and current delivery capabilities of the alternator.

scholarly journals A Novel Single-Switch Single-Stage LED Driver with Power Factor Correction and Current Balancing Capability

Electronics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1340
Author(s):  
Yih-Her Yan ◽  
Hung-Liang Cheng ◽  
Chun-An Cheng ◽  
Yong-Nong Chang ◽  
Zong-Xun Wu
Keyword(s):  
Power Factor ◽  
High Power ◽  
Pulse Width Modulation ◽  
Power Factor Correction ◽  
Harmonic Distortion ◽  
Boost Converter ◽  
Single Stage ◽  
Led Driver ◽  
Flyback Converter ◽  
High Power Factor

A novel single-switch single-stage high power factor LED driver is proposed by integrating a flyback converter, a buck–boost converter and a current balance circuit. Only an active switch and a corresponding control circuit are used. The LED power can be adjusted by the control scheme of pulse–width modulation (PWM). The flyback converter performs the function of power factor correction (PFC), which is operated at discontinuous-current mode (DCM) to achieve unity power factor and low total current harmonic distortion (THDi). The buck–boost converter regulates the dc-link voltage to obtain smooth dc voltage for the LED. The current–balance circuit applies the principle of ampere-second balance of capacitors to obtain equal current in each LED string. The steady-state analyses for different operation modes is provided, and the mathematical equations for designing component parameters are conducted. Finally, a 90-W prototype circuit with three LED strings was built and tested. Experimental results show that the current in each LED string is indeed consistent. High power factor and low THDi can be achieved. LED power is regulated from 100% to 25% rated power. Satisfactory performance has proved the feasibility of this circuit.

Design of EMI Filters Having Low Harmonic Distortion in High-Power-Factor Converters

2014 ◽  
Vol 29 (7) ◽  
pp. 3403-3413 ◽  
Author(s):  
Yoash Levron ◽  
Hyeokjin Kim ◽  
Robert W. Erickson
Keyword(s):  
Power Factor ◽  
High Power ◽  
Harmonic Distortion ◽  
High Power Factor ◽  
Emi Filters

Modeling and Analysis of the Dynamic Response of an Off-Grid Synchronous Generator Driven Micro Hydro Power System

2021 ◽  
Vol 10 (2) ◽  
pp. 373-384
Author(s):  
Waqas Ali ◽  
Haroon Farooq ◽  
Akhtar Rasool ◽  
Intisar Ali Sajjad ◽  
Cui Zhenhua ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Power System ◽  
Power Factor ◽  
Synchronous Generator ◽  
Operating Conditions ◽  
System Stability ◽  
Hydro Power ◽  
Modeling And Analysis ◽  
Full Load ◽  
Generator Voltage

This paper models and analyses the dynamic response of a synchronous generator driven off-grid micro hydro power system using Simulink tool of MATLAB software. The results are assessed from various perspectives including regulation through no load to full load and overload scenarios under normal and abnormal operating conditions. The investigation under the normal conditions of no load, linearly changing load and full load divulges that the system operates in a satisfactory manner as generator voltage and frequency remain approximately constant at 1 pu. However, at full load generator voltage and frequency drop 3% and 0.5% respectively from its nominal values but remain within prescribed standard IEC limits. The results also expose that the abnormal conditions produced by abrupt changes in load, system faults and severe overload, cause the unwonted variations in the magnitude of generator parameters. Moreover, the study reveals that the system stability significantly enhances when the system is run at full load because the regulation time to fix the variations in the generator parameters; except input mechanical power; decreases, e.g. from 4.1 sec to 0.8 sec for generator voltage, with the increase in the loading from quarter to full load respectively at unity power factor. Further, it is also observed that the regulation time rises, e.g. from 0.8 sec to 1.3 sec for generator voltage, with the reduction in load power factor from unity to 0.8, respectively. Thus, proper protection, to cater for increased fault current at full load and power factor correction must be provided to improve the system stability and protection. Furthermore, it is also concluded that the over loading in any case should be strongly avoided in this type of system and it should never be allowed to exceed 20% of the full load value to avoid system failure 

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