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The three-phase dual active bridge (3p-DAB) converter is widely addressed in emerging power systems applications such as solid-state transformer and dc microgrids. Its successful integration requires accurate modeling of its small-signal characteristics. Due to its dc–ac–dc structure, the DAB converter brings many challenges to small-signal modeling. The state-space averaging (SSA) has been the first proposed methodology to approximate the control-to-output and line-to-output transfer functions of the 3p-DAB. However, as shown in this paper, SSA is not precise for the stability analysis of 3p-DAB converters. A generalized state-space averaging (GSSA) model based on the dynamic phasor concept is developed in this paper for the Y-Δ 3p-DAB. A hybrid SSA and GSSA model representation is then proposed for the evaluation of all the converter transfer functions. The developed models are validated with detailed time-domain switch-level simulations in an electromagnetic transient-type (EMT-type) program. They are also used for the accelerated stability prediction in an EMT-type program. [ABSTRACT FROM PUBLISHER]

This paper proposes a proportional-integral (inertial) multiresonant (PIMR) type repetitive control (PIMR-type RC) scheme for a grid-tied inverter. The proposed control scheme is composed of a repetitive controller in parallel with a proportional gain for the purpose of replacing lots of parameters of the conventional proportional multiresonant controller, and therefore, only a few parameters need to be designed. The proportional gain not only improves the dynamic response, but also enables repetitive controller (RC) to accommodate a larger RC gain, and hence a faster convergence rate. Theoretical analysis and stability analysis of PIMR-type RC are given, and then a practical step-by-step design tutorial is also provided. The experimental results validate the feasibility and outstanding performance of the proposed control scheme. [ABSTRACT FROM PUBLISHER]

The ITER pulsed power electrical network (PPEN) supplies the superconducting magnets and the heating and current drive systems. During the experimental pulses, about several hundreds of seconds long, active power consumption of 500 MW and reactive one of 950 Mvar are expected. The ITER power supply system is very large and complex, and a careful design is required to assure a safe operation. Stability of ITER PPEN has been already investigated in recent studies by numerical simulation and analytical methods. Now, a new dynamic analytical model of the ITER power supply system is being developed, based on the state-space theoretical approach, which allows the application of the linear control theory to study the stability of the whole system. For each subsystem of the ITER power supply, a state-space model was developed, and in this paper, the ac/dc converter model is presented and validated for six and twelve pulse operation, and circulating current mode. [ABSTRACT FROM AUTHOR]

This paper deals with the design of a speed-adaptive full-order observer for sensorless induction motor (IM) drives. A general stabilizing observer gain matrix, having three free design parameters, is used as a design framework. A gain-scheduled selection of the free design parameters is proposed. Furthermore, the full-order observer is augmented with the stator-resistance adaptation, and the local stability of the augmented observer is analyzed. The performance of the proposed full-order observer design is experimentally compared with a reduced-order observer using a 2.2-kW IM drive. [ABSTRACT FROM AUTHOR]

Open-loop constant voltage/frequency (v/f) adjustable speed drives (ASDs) can often experience undesirablesustained oscillations. Factors affecting these oscillation states include induction machine (IM) parameters, dead time,dc-link capacitor size, IM saturation, output voltage, carrier frequency, and IM speed. Many literatures have discussedthe instabilities in light-load or low-frequency operating conditions. Quite a few methods have been proposed forstabilizing such a system. However, the instability problems, at different power levels, have not been completelydescribed. This paper analyzes the causes of this instability for constant v/f drives as power levels change. The 2.2-and 15-kW low-voltage IMs and the 746-kW medium-voltage IM are evaluated to illustrate how the motor parameters affectthe system stability. Additionally, a new oscillation mitigation method is introduced to demonstrate its effectivenessin solving the instability problems. It is based on the synchronous reference frame dynamic current feedback through itsmagnetic flux current component bandpass filtering and proportional control. In a theoretical stability analysis beforeand after the current feedback compensation, simulation studies are presented and verified through a 15-kW 380-V 50-HzIM ASD experimental system. [ABSTRACT FROM AUTHOR]

The effect of Hf addition on the electrical performance and bias stability of ZnO-based thin-film transistors (TFTs) has been investigated. All channel layers were deposited by atomic layer deposition with various Hf contents. In addition, multilayer oxide channel TFTs consisting of two or three Hf-doped ZnO (HZO) and ZnO layers were developed for the realization of adequate channel mobility and electrical stability. The subthreshold swing and bias stability were improved by the deposition of the thin-HZO layers with amorphous phase as the first and final channel layers. The use of a conductive ZnO layer enhanced the device mobility. The oxide TFTs with a multilayer channel of a-HZO/ZnO/a-HZO exhibited relatively good stability and mobility due to the reduced interface trap density between the channel and dielectric layers, and the suppressed adsorption of negatively charged oxygen on the back channel. The origin of the stability issues and novel channel design are proposed on the basis of the electrical performance of various TFT structures. [ABSTRACT FROM PUBLISHER]

A 3-D finite-difference time-domain (FDTD) scheme with controllable stability beyond the stability limit of FDTD is presented. The key to controlling the FDTD stability limit is a spatial filter applied to the electromagnetic field vectors in order to ensure that unstable spatial harmonics are eliminated. A significant advantage of this approach is the simplicity of its incorporation into existing FDTD codes. Moreover, this method is employed as a means to implement a late-time stable 3-D sub-gridding scheme. Applications include waveguide filters and the analysis of screens for near-field sub-wavelength focusing at microwave frequencies. [ABSTRACT FROM PUBLISHER]