A New Control Method for Input-Output Harmonic Elimination of the Pwm Boost-Type Rectifier Under Extreme Unbalanced Operating Conditions

Under severe fault conditions in the distribution system, not only input voltages but also input impedances must be considered as unbalanced. This paper presents a new control method for input-output harmonic elimination of the pulsewidth-modulation (PWM) boost-type rectifier under conditions of both unbalanced input voltages and unbalanced input impedances. The range of imbalance in both input voltages and input impedances, for which the proposed method is valid, is analyzed in detail. An analytical approach for complete harmonic elimination shows that PWM boost-type rectifier can operate at unity power factor under extremely unbalanced operating conditions resulting in a smooth (constant) power flow from ac to dc side. Based on the analyses in open-loop configuration, a feedforward control method is proposed. Elimination of harmonics at ac and dc side of the converter affects the cost of dc link capacitor and ac side filter. The proposed method is very useful when the PWM boost-type rectifier is subject to extreme imbalance due to severe fault conditions in the power system. In addition, by using the proposed method, the PWM boost-type rectifier can be operated from the single-phase supply in cases where three-phase source is not available. Simulation results show excellent response and stable operation of the PWM boost-type rectifier under the proposed control algorithm. Experimental and simulation results are in excellent agreemen

A Novel Discrete Dimming Ballast for Linear Fluorescent Lamps

A novel discrete dimming ballast for linear fluorescent lamps is proposed in this paper. A proposed dimming control circuit is combined with a ballast module for multiple lamps to realize control of three discrete lighting levels. Compared with conventional step dimming or ON-OFF control methods, the proposed discrete dimming method has the following advantages: 1) digital signal is generated by the dimming control circuit to control the lamps\u27 turn- ON and -OFF, which makes the system more reliable and integrated; 2) the proposed discrete dimming system replaces relays, which are necessary in conventional lamp ON-OFF control, and therefore decreases the system cost; 3) the proposed dimming ballast can be installed by keeping the original wiring system. This makes the upgrading of a lighting system more effective and efficient; 4) the dimming control circuit also provides a good isolation for operating the low-voltage wall switches by hand safely. Both theoretical, simulation, and experimental results are in good agreement

A Novel Method for Measuring Induction Machine Magnetizing Inductance

This paper presents a novel method for measuring the magnetizing inductance of an induction machine. The approach uses a static DC excitation technique which can be employed whenever the neutral of the machine is accessible. The proposed method measures only the magnetizing inductance and not the self inductance which normally includes the effect of the stator leakage inductance. Because this test uses a DC excitation, the iron losses in the motor are considerably reduced as well and minimally influence the measurement when compared to the traditional 60-Hz no-load test. By using the proposed method for measuring only the magnetizing inductance, the stator leakage inductance can be later individually determined by performing a separate no-load test. Test results using the method are compared with theoretical values and confirm its feasibility

A Novel Method for Measuring Induction Machine Magnetizing Inductance

This paper presents a novel method for measuring the magnetizing inductance of an induction machine. The approach uses a static DC excitation technique which can be employed whenever the neutral of the machine is accessible. The proposed method measures only the magnetizing inductance and not the self inductance which normally includes the effect of the stator leakage inductance. Because this test uses a DC excitation, the iron losses in the motor are considerably reduced as well and minimally influence the measurement when compared to the traditional 60-Hz no-load test. By using the proposed method for measuring only the magnetizing inductance, the stator leakage inductance can be later individually determined by performing a separate no-load test. Test results using the method are compared with theoretical values and confirm its feasibility

Effect of remote ischaemic conditioning on clinical outcomes in patients with acute myocardial infarction (CONDI-2/ERIC-PPCI): a single-blind randomised controlled trial.

BACKGROUND: Remote ischaemic conditioning with transient ischaemia and reperfusion applied to the arm has been shown to reduce myocardial infarct size in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). We investigated whether remote ischaemic conditioning could reduce the incidence of cardiac death and hospitalisation for heart failure at 12 months. METHODS: We did an international investigator-initiated, prospective, single-blind, randomised controlled trial (CONDI-2/ERIC-PPCI) at 33 centres across the UK, Denmark, Spain, and Serbia. Patients (age >18 years) with suspected STEMI and who were eligible for PPCI were randomly allocated (1:1, stratified by centre with a permuted block method) to receive standard treatment (including a sham simulated remote ischaemic conditioning intervention at UK sites only) or remote ischaemic conditioning treatment (intermittent ischaemia and reperfusion applied to the arm through four cycles of 5-min inflation and 5-min deflation of an automated cuff device) before PPCI. Investigators responsible for data collection and outcome assessment were masked to treatment allocation. The primary combined endpoint was cardiac death or hospitalisation for heart failure at 12 months in the intention-to-treat population. This trial is registered with ClinicalTrials.gov (NCT02342522) and is completed. FINDINGS: Between Nov 6, 2013, and March 31, 2018, 5401 patients were randomly allocated to either the control group (n=2701) or the remote ischaemic conditioning group (n=2700). After exclusion of patients upon hospital arrival or loss to follow-up, 2569 patients in the control group and 2546 in the intervention group were included in the intention-to-treat analysis. At 12 months post-PPCI, the Kaplan-Meier-estimated frequencies of cardiac death or hospitalisation for heart failure (the primary endpoint) were 220 (8·6%) patients in the control group and 239 (9·4%) in the remote ischaemic conditioning group (hazard ratio 1·10 [95% CI 0·91-1·32], p=0·32 for intervention versus control). No important unexpected adverse events or side effects of remote ischaemic conditioning were observed. INTERPRETATION: Remote ischaemic conditioning does not improve clinical outcomes (cardiac death or hospitalisation for heart failure) at 12 months in patients with STEMI undergoing PPCI. FUNDING: British Heart Foundation, University College London Hospitals/University College London Biomedical Research Centre, Danish Innovation Foundation, Novo Nordisk Foundation, TrygFonden

Ride-Through Fault Generalized Control Method for a Wind Turbine Inverter

The growing share of installed wind capacity in transmission systems nowadays require wind turbines to remain connected to the grid during severe network disturbances as well as to provide efficient restoration to the pre-fault conditions. It is know that grid side inverters are sensitive to voltage disturbances which results in appearance of low order harmonics in line currents as well as a huge ripple on a DC link capacitor. This paper presents a generalized method for grid-fault ride-through control for a wind turbine inverter. An analytical approach for complete harmonic elimination in grid currents and DC link voltage with controllable power factor under extreme disturbances in the power system is proposed. To illustrate the proposed method, the simulation results of a variable speed wind turbine system with PM synchronous generator under severe faults are shown and compared to the results obtained by using a standard indirect current control method

A Generalized Method for Wind Inverter Control under Unbalanced Operating Conditions

In this paper, a generalized method for a wind inverter control under unbalanced operating conditions is proposed. The control method presented in this paper provides complete harmonic elimination in line currents and DC link voltage with adjustable power factor. The method is general and can be used for all levels of imbalance in grid voltages and line impedances. Simulation results for a variable speed windturbine system with PM synchronous generator connected to unbalanced grid voltages and line impedances are compared to results obtained by using a standard control of a grid side inverter. In addition, the proposed method has been verified for a grid-fault ride through control of the wind inverter

Ride-Through Fault Generalized Control Method for a Wind Turbine Inverter

The growing share of installed wind capacity in transmission systems nowadays require wind turbines to remain connected to the grid during severe network disturbances as well as to provide efficient restoration to the pre-fault conditions. It is know that grid side inverters are sensitive to voltage disturbances which results in appearance of low order harmonics in line currents as well as a huge ripple on a DC link capacitor. This paper presents a generalized method for grid-fault ride-through control for a wind turbine inverter. An analytical approach for complete harmonic elimination in grid currents and DC link voltage with controllable power factor under extreme disturbances in the power system is proposed. To illustrate the proposed method, the simulation results of a variable speed wind turbine system with PM synchronous generator under severe faults are shown and compared to the results obtained by using a standard indirect current control method

A Universal Programmed Start Dimming Ballast

In this paper, a novel universal programmed start dimming ballast platform for fluorescent lamps is proposed. The proposed platform consists of an independent PWM type filament heating control circuit for filaments preheat and filament heating in dimming condition. Mathematical analysis of the proposed method is discussed in the paper. Experimental results of T8 32watt and T5 28watt lamps are presented to validate the proposed method

A Generalized Method for Wind Inverter Control under Unbalanced Operating Conditions

In this paper, a generalized method for a wind inverter control under unbalanced operating conditions is proposed. The control method presented in this paper provides complete harmonic elimination in line currents and DC link voltage with adjustable power factor. The method is general and can be used for all levels of imbalance in grid voltages and line impedances. Simulation results for a variable speed windturbine system with PM synchronous generator connected to unbalanced grid voltages and line impedances are compared to results obtained by using a standard control of a grid side inverter. In addition, the proposed method has been verified for a grid-fault ride through control of the wind inverter