Phase Current Measurement Method of Dual Inverter-Motor Drive System Using a Single DC Link Current Sensor

In recent years, electric propulsion systems have become widely, used and these systems have strict limits in volume and weight. Therefore, it is necessary to reduce the weight of the inverter-motor drive system. In a typical n inverter-motor drive system, at least 2n phase current sensors are required. In order to reduce the number of phase current sensors, this paper proposes a method for measuring phase current using n DC link current sensors in a 2n inverter-motor drive system. Two phase currents per inverter-motor system are measured during one period of the switching frequency using the pulse width modulation (PWM) shift method. However, since the measured phase current contains an error component in the average current, the error component was compensated for in order to obtain a current similar to the actual phase current by using the slope and dwell time of the phase current. The effectiveness of the proposed method is verified through experiments

Phase Current Measurement Method of Dual Inverter-Motor Drive System Using a Single DC Link Current Sensor

In recent years, electric propulsion systems have become widely, used and these systems have strict limits in volume and weight. Therefore, it is necessary to reduce the weight of the inverter-motor drive system. In a typical n inverter-motor drive system, at least 2n phase current sensors are required. In order to reduce the number of phase current sensors, this paper proposes a method for measuring phase current using n DC link current sensors in a 2n inverter-motor drive system. Two phase currents per inverter-motor system are measured during one period of the switching frequency using the pulse width modulation (PWM) shift method. However, since the measured phase current contains an error component in the average current, the error component was compensated for in order to obtain a current similar to the actual phase current by using the slope and dwell time of the phase current. The effectiveness of the proposed method is verified through experiments

Opposite Triangle Carrier with SVPWM for Common-Mode Voltage Reduction in Dual Three Phase Motor Drives

The common-mode voltage (CMV) generated by the switching operation of the pulse width modulation (PWM) inverter leads to bearing failure and electromagnetic interference (EMI) noises. To reduce the CMV, it is necessary to reduce the magnitude of dv/dt and change the frequency of the CMV. In this paper, the range of the CMV is reduced by using opposite triangle carrier for ABC and XYZ winding group, and the change in frequency in the CMV is reduced by equalizing the dwell time of the zero voltage vector on ABC and XYZ winding group of dual three phase motor

A Vector-Controlled Distributed Generator Model for a Power Flow Based on a Three-Phase Current Injection Method

This paper proposes a vector-controlled distributed generator (DG) model for a power flow based on a three-phase current injection method (TCIM). In order to represent the DG models in the power flow, steady-state phase current output equations are formulated. Using these equations, the TCIM power flow formulation is modified to include the DG models. In the proposed power flow, a DG-connected bus is modeled as either a load bus (PQ bus) or a voltage-controlled bus (PV bus), depending on the control mode of the reactive power. However, unlike conventional bus models, the values of the DG-connected bus models are represented by three-phase quantities: three-phase active and reactive power output for a PQ bus, and three-phase active power and positive-sequence voltage for a PV bus. In addition, a method is proposed for representing the reactive power limit of a voltage-control-mode DG by using the q-axis current limit. Utilizing a modified IEEE 13-bus test system, the accuracy of the proposed method is verified by comparison to the power systems computer aided design (PSCAD) model. Furthermore, the effect of the number of DGs on the convergence rate is analyzed, using the IEEE 123-bus test system

A Conservation Voltage Reduction Scheme for a Distribution Systems with Intermittent Distributed Generators

In this paper, a conservation voltage reduction (CVR) scheme is proposed for a distribution system with intermittent distributed generators (DGs), such as photovoltaics and wind turbines. The CVR is a scheme designed to reduce energy consumption by lowering the voltages supplied to customers. Therefore, an unexpected under-voltage violation can occur due to the variation of active power output from the intermittent DGs. In order to prevent the under-voltage violation and improve the CVR effect, a new reactive power controller which complies with the IEEE Std. 1547TM, and a parameter determination method for the controller are proposed. In addition, an optimal power flow (OPF) problem to determine references for the resources of CVR is formulated with consideration of the intermittent DGs. The proposed method is validated using a modified IEEE 123-node test feeder. With the proposed method, the voltages of the test system are maintained to be greater than the lower bound, even though the active power outputs of the DGs are varied. Moreover, the CVR effect is improved compared to that used with the conventional reactive power control methods

The Clinical Efficacy of Silicone Stents for Endoscopic Dacryocystorhinostomy: A Meta-Analysis

We evaluated the effect of silicone stent use during endoscopic dacryocystorhinostomy on postoperative morbidities in comparison with versus without a silicone stent. Two authors independently searched six databases (PubMed, Embase, Scopus, the Web of Science, the Cochrane library, and Google Scholar) from inception of article collection to July 2017. The analysis included prospective randomized studies that compared intraoperative silicone stent insertion (silicone group) with no application of a silicone stent (control group), in which the outcomes of interest were success rate (lacrimal passage patent check with syringing, symptom relief, or endoscopic confirmation of fluorescein dye from the opening of Hasner’s valve) and morbidities (e.g., postoperative bleeding, rhinostomy closure, granulation tissue, synechia, and eyelid problems) after certain follow-up periods (over 10 weeks). Nine studies involving a total of 587 participants were included. Functional success rates tended to be higher in the silicone group than in the control, but there was no statistically significant difference in success rates (odds ratio, 1.45; 95% confidence interval, 0.77 to 2.73). According to the surgical type such as mucosal removal and mucosal flap surgery, the results from types didn’t demonstrate any significant effect, but the mucosal flap technique seemed to be more beneficial. Regarding postoperative morbidities, although the outcomes of the groups did not present any statistically significant difference, eyelid problems and postoperative bleeding tended to occur more frequently in the silicone group, but rhinostomy closure tended to occur more frequently in the control group. Success and morbidity rates showed no difference between the silicone stent group and control group in the meta-analysis. However, additional analyses revealed that the success rate of endonasal dacryocystorhinostomy using silicone intubation with mucosal flap has shown an improving trend, and morbidities such as granulation and synechia showed decreasing trends compared with the group without silicone intubation

Coordinated Control of a DG and Voltage Control Devices Using a Dynamic Programming Algorithm

This paper presents a new control method, in which a distributed generator (DG) actively participates in steady-state voltage control, together with an under-load tap changer (ULTC) and shunt capacitors (Sh.Cs). In the conventional DG control method, the integration of DGs into a distribution power system increases the number of switching operations of the ULTC and the Sh.Cs. To solve this problem, this paper proposes that the DG output voltage be dispatched cooperatively with the operation of the ULTC and the Sh.Cs, based on load forecasts for one day in advance. The objective of the proposed method is to decrease the number of switching device operations, as well as to reduce the power loss in the distribution lines, while maintaining the grid voltage within the allowed range. The proposed method is designed and implemented with MATLAB, using two different dynamic programming algorithms for a dispatchable and a nondispatchable DG, respectively. Simulation studies demonstrate that the objective can be achieved under various grid conditions, determined by factors such as the DG output power characteristics, the location of the DG-connected bus on the feeder, and the load profile of the feeder containing the DG.11Nsciescopu