Power Factor

Nowadays, the number of sensitive loads connected to the utility line increases fast. These loads need a highly reliable power supply. One way to provide this kind of energy is using an uninterruptible power supply (UPS). Basically, a UPS providing input power factor correction (PFC) is a three stage system: PFC stage, DC-DC converter stage and inverter stage. The approach proposed eliminates the DC-DC converter stage and removes the bulk capacitor of the PFC stage to use the natural output waveform of the converter before filtering: a semisinusoidal waveform. This allows the inverter stage working at low frequency with high efficiency. The PFC stage is based on a flyback topology operating in DCM to have a simple control loop.

ABSTRACT This paper is concerned with the design and implementation of current control of three-phase PWM rectifier based on predictive control strategy. The proposed predictive current control technique operates with constant switching frequency, using space-vector modulation (SVM). The main goal of the designed current control scheme is to maintain the dc-bus voltage at the required level and to achieve the unity power factor (UPF) operation of the converter. For this purpose, two predictive current control algorithms, in the sense of deadbeat control, are developed for direct controlling input current vector of the converter in the stationary α–β and rotating d–q reference frame, respectively. For both predictive current control algorithms, at the beginning of each switching period, the required rectifier average voltage vector allowing the cancellation of both tracking errors of current vector components at the end of the switching period, is computed and applied during a predefined switching period by means of SVM. The main advantages of the proposed predictive current control are that no need to use hysteresis comparators or PI controllers in current control loops, and constant switching frequency. Finally, the developed predictive current control algorithms were tested both in simulations and experimentally, and illustrative results are presented here. Results have proven excellent performance in steady and transient states, and verify the validity of the proposed predictive current control which is compared to other control strategies.

Single-phase and three-phase unity power factor converters are nowadays becoming one of the most important requirements for power electronic rectifiers. In this paper, the idea of using a VSS control strategy in the sliding mode is described. A new discrete time control algorithm has been developed by combining VSS and Lyapunov designs. It possesses all the good properties of the

... Laura Bocher a , Rosa Robert a , Myriam H. Aguirre a , Sylvie Malo b , Sylvie Hébert b , Antoine Maignan b and Anke Weidenkaff a , Corresponding ... [1] In: DM Rowe, Editor, Thermoelectrics Handbook – Macro to Nano, CRC Press/Taylor & Francis Group, Boca Raton (2006), p ...

... this output instanta-neous power becomes oscillating when the converter operates under ... to understand the characteristics of the instantaneous power flow under unbalanced operating conditions. ... WU et al.: ANALYSIS OF THE INSTANTANEOUS POWER FLOW FOR THREE ...

Recently, the evolutionary development in power electronics (PE) technologies onboard shipboard micro-grids (SMs) has been receiving significant attention. Indeed, this evolution added enormous advantages such as enhanced maneuverability and controllability. However, the installation of PE converters onboard SMs results in serious power quality issues. The application of the fixed capacitors-thyristor controlled reactors (FCs-TCRs) is largely used to improve some of the power quality issues. However, the non-linearity of the firing angle equation increases the complexity of controlling this sophisticated technology. In this paper, three simple and yet effective numerical algorithms are proposed to estimate the firing angle of the FC-TCR compensator. These algorithms that are based on Newton-Raphson, Bisection, and false position methods have proved their reliability and efficacy in estimating the firing angle under load and frequency variation. The effectiveness and robustness of the proposed methods are demonstrated via modeling an electrical power system of a practical hybrid ferry under MATLAB/Simulink environment, then the results are compared with the traditional technique.

Many induction motors are installed in ship electric power systems, where a poor power factor is often overlooked. Power factor compensation that is usually achieved by adding capacitive load to offset the inductive load present in the system can have many benefits. As a ship power system, fuel oil costs and air pollution emissions for power generation remain low. This paper aims to establish a set of energy-savings evaluation model for benefit-cost analysis for automatic power factor compensators (APFCs) applied in marine vessels. The active power, reactive power, power factor, and diesel electric engine's oil consumption for a practical commercial vessel power system during different operating conditions were measured and analyzed. Base on the actual measurements, an APFC for marine use is designed and the possible benefits after installing the APFC are quantified to justify the investment by using two standard cost-benefit analysis methods. Sensitivity analysis is also performed to reduce effects of input parameters on the analysis results and determine the critical parameters. Analysis results can assist shipbuilding corporations and ship owners in managing energy efficiency of similar systems and building business cases for determining return on investment (ROI).

In recent years, the significant revolution of shipboard micro-grids (SMs) towards all-electric ships offered several advantages such as high efficiency, better maneuverability, and controllability. However, the application of power electronics onboard SMs, particularly for DC and hybrid ships leads to serious power quality issues. The application of passive power filters (PPFs) has been largely used to solve some of the power quality issues, such as harmonics contamination, power factor compensation, and voltage drop enhancement. However, analyzing some crucial factors such as the harmonic attenuation factor (HAF) and filters sensitivity factor (FSF) of these filters have not been attracted much attention. In this paper, a more in-depth mathematical analysis of the HAF and FSF of these filters is conducted with details. Moreover, some developed solutions to improve these factors are suggested. Based on intensive simulation studies of a practical hybrid ferry, which are carried out under MATLAB/Simulink environment, it has been demonstrated that the conducted analysis and proposed solutions can enhance the filtering performance of the PPFs.

... The labo-ratory tests show that the size of the dc link capacitor can be lowered from 24 mF inSection IV to 0.95 ... [13] J. W. Dixon, AB Kulkami, M. Nishimoto, and B. T. Ooi, “Char-acteristics of a controlled-current PWM rectifier-inverter link,” pre-sented at the IEEE IAS Annu ...

Abstract— This paper proposes a novel linear permanent magnet machine for direct drive applications in which a magnetic gear is ingeniously integrated with a tubular linear machine, aiming at improving the thrust force density and enhancing the machine efficiency. The operating principle of ...

Through the theoretical, simulation and experimental analyses, the study in this article indicates that the turn-on angle, turn-off angle, DC link capacitor, duty cycle, and the chopping modes of PWM as well as the motor speed all have significant effects upon the power factor. However, the input voltage has virtually no effect upon the power factor. The novel strategies are proposed to improve the operating power factor using the analytical findings being reported. This study is valuable for designers searching for good controllers having high operating power factors.