http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Novel tricarbazole compounds are provided. By appropriately selecting the nature of the tricarbazole substituents, compounds with appropriate HOMO and LUMO energies can be obtained for use as materials in a secondary hole transport layer.

Organic Electroluminescent Materials and Devices

The installed capacity of photovoltaic (PV) systems globally reached 177 GW at the end of 2014 The annual rate of installations, 387 GW in 2014, continues to increase A large part of this is installed as residential systems connected to low voltage (LV) networks The majority of the LV distribution networks are radial, unbalanced with respect to loads and feeder structures and have high R/X ratios The large scale deployment of PV within the LV distribution networks is limited by voltage quality problems, particularly over voltages and unbalance Development of proper mitigation techniques is essential to effectively and efficiently manage high penetration of PV within the LV distribution networks A number of techniques have already been developed and implemented in LV distribution networks to alleviate those problems This paper provides an extensive review of the present status, impacts and technical challenges of PV penetration in LV distribution networks In addition, the review comprehensively examines the commercially available and emerging mitigation methods and provides a framework that systematically explores the full range of technical methods and limitations for PV impact mitigation These will provide a useful framework and strong point of reference for the researchers working further in this field

A review of high PV penetrations in LV distribution networks: Present status, impacts and mitigation measures

To achieve instantaneous control of induction motor torque using field-orientation techniques, it is necessary that the phase currents be controlled to maintain precise instantaneous relationships. Failure to do so results in a noticeable degradation in torque response. Most of the currently used approaches to achieve this control employ classical control strategies which are only correct for steady-state conditions. A modern control theory approach which circumvents these limitations is developed. The approach uses a state-variable feedback control model of the field-oriented induction machine. This state-variable controller is shown to be intrinsically more robust than PI regulators. Experimental verification of the performance of this state-variable control strategy in achieving current-loop performance and torque control at high operating speeds is included.

https://ieeexplore.ieee.org/iel5/28/4504948/04504956.pdf

Performanceof FeedforwardCurrentRegulators forField-Oriented Induction Machine Controllers

A light-emitting element with high emission efficiency which includes fluorescent materials is provided. The light-emitting element includes a first light-emitting layer and a second light-emitting layer. The first light-emitting layer includes a first fluorescent material and a first host material, and the second light-emitting layer includes a second fluorescent material and a second host material. The second host material includes a first organic compound and a second organic compound. The first organic compound and the second organic compound form an exciplex. A singlet excited energy level of the first host material is higher than a singlet excited energy level of the first fluorescent material, and a triplet excited energy level of the first host material is lower than a triplet excited energy level of the first fluorescent material.

Light-emitting element, display device, electronic device, and lighting device

If a small dc-link capacitor is used in the dc link fed by a single-phase ac source, then the dc-link voltage severely fluctuates at twice of the source frequency. To handle this fluctuation, the concept of “average voltage constraint” is proposed in this study. On the basis of this concept, a flux-weakening scheme, generating the d-axis current reference (idsr*) for the interior permanent-magnet synchronous machine, is devised. The q-axis current reference (iqsr*) is modified for the unity power factor operation in the viewpoint of an ac source without an additional sensor. The proposed scheme has been applied to the inverter-driven 1-kW compressor of an air conditioner. From the experimental results, it has been verified that the compressor operates well at the required operating condition, regardless of the severe fluctuation of dc-link voltage, because of the reduced dc-link capacitance. The frequency spectrum of the ac source current reveals that the harmonics of the source current meet the regulation of IEC 61000-3-2 Class A and that the overall power factor is above 96% without any additional circuit, such as an input filter and a power factor correction circuit.

Control of Three-Phase Inverter for AC Motor Drive With Small DC-Link Capacitor Fed by Single-Phase AC Source

The design of novel exciplex-forming co-host materials provides new opportunities to achieve high device performance of organic light emitting diodes (OLEDs), including high efficiency, low driving voltage and low efficiency roll-off. Here, we report a comprehensive study of exciplex-forming co-host system in OLEDs including the change of co-host materials, mixing composition of exciplex in the device to improve the performance. We investigate various exciplex systems using 5-(3–4,6-diphenyl-1,3,5-triazin-2-yl)phenyl-3,9-diphenyl-9H-carbazole, 5-(3–4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9-phenyl-9H-3,9′-bicarbazole, and 2-(3-(6,9-diphenyl-9H-carbazol-4-yl)phenyl)-4-phenylbenzo[4,5]thieno[3,2-d]pyrimidine, as electron transporting (ET: electron acceptor) hosts and 9,9′-dipenyl-9H, 9′H-3,3′-bicarbazole and 9-([1,1′-biphenyl]-4-yl)-9′-phenyl-9H,9′H-3,3′-bicarbazole as hole transporting (HT: electron donor) hosts. As a result, a very high current efficiency of 105.1 cd/A at 103 cd/m2 and an extremely long device lifetime of 739 hrs (t95: time after 5% decrease of luminance) are achieved which is one of the best performance in OLEDs. Systematic approach, controlling mixing ratio of HT to ET host materials is suggested to select the component of two host system using energy band matching and charge balance optimization method. Furthermore, our analysis on exciton stability also reveal that lifetime of OLEDs have close relationship with two parameters; singlet energy level difference of HT and ET host and difference of singlet and triplet energy level in exciplex.

/pdf/the-role-of-charge-balance-and-excited-state-levels-on-1j7jw2xej4.pdf

The Role of Charge Balance and Excited State Levels on Device Performance of Exciplex-based Phosphorescent Organic Light Emitting Diodes

An inverter control apparatus and a control method thereof are provided. The inverter control apparatus and a control method thereof stably operate a three-phase motor using a capacitor having a small capacitance for a DC link. The inverter control apparatus includes a current sensor to sense an output current of the inverter, a voltage sensor to sense a DC-link voltage of the inverter, and a controller to generate an average of a periodically varying rotor based q-axis current boundary value based on the output current and the DC-link voltage to generate a current reference on the basis of the average of the rotor based q-axis current boundary value, and to drive a three-phase motor based on the current reference. Stabilized variable speed control of a motor by using a small-capacitance capacitor for a DC link of an inverter is performed and reliability of an inverter circuit improved.

Inverter control apparatus and control method thereof

A control apparatus for a cleaning robot comprises: a user interface unit which receives an input of a user command for controlling the cleaning robot; a control unit for, on the basis of the user command, generating a control signal so as to receive a map of a cleaning region; and a communications unit for, on the basis of the control signal, receiving the map of the cleaning region from an external server or the cleaning robot. The cleaning robot, and the control apparatus, the control system and the control method for the cleaning robot allow a map of a cleaning region to be downloaded or generated, and to be editable by a user. In addition, attributes such as priority of the cleaning region, cleaning time and cleaning period of a cleaning schedule can be set up and edited. When a cleaning schedule is set up, a function of recommending a cleaning schedule on the basis of cleaning history data can be provided. Further, during the cleaning process by the cleaning robot, the cleaning robot can automatically determine environment changes or whether cleaning is possible and actively deal therewith. Moreover, since a user interface is provided, user convenience of the cleaning robot can be improved.

Cleaning robot, and control apparatus, control system and control method for cleaning robot

A method of estimating inductance of a permanent magnet synchronous motor (PMSM) includes injecting a signal having a frequency differing from an operating frequency of the PMSM into the PMSM during sensorless operation, sensing magnitudes of current responses to the injected signal, and estimating an inductance value at which the magnitude of the sensed current response is minimal to be an actual inductance value of the PMSM, thereby estimating inductance used in the PMSM regardless of position estimation error of the PMSM and thus more accurately and reliably estimating inductance of the PMSM.

Young-Jae Park

Papers

Control of Three-Phase Inverter for AC Motor Drive With Small DC-Link Capacitor Fed by Single-Phase AC Source

The Role of Charge Balance and Excited State Levels on Device Performance of Exciplex-based Phosphorescent Organic Light Emitting Diodes

Inverter control apparatus and control method thereof

Cleaning robot, and control apparatus, control system and control method for cleaning robot

Apparatus and method of estimating inductance of permanent magnet synchronous motor