Output impedance

About: Output impedance is a research topic. Over the lifetime, 11185 publications have been published within this topic receiving 134949 citations.

Small-Signal Impedance Measurement of Power-Electronics-Based AC Power Systems Using Line-to-Line Current Injection

Abstract: Naval ships as well as aerospace power systems are incorporating a greater degree of power electronic switching sources and loads. Although these components provide exceptional performance, they are prone to instability due to their high efficiency and constant power characteristics that can exhibit negative impedance nature at certain frequencies. When designing these systems, integrators must consider the impedance versus frequency at an interface (which designates source and load). Stability criteria have been developed in terms of source and load impedances for both dc and ac systems, and it is often helpful to have techniques for impedance measurement. For dc systems, the measurement techniques have been well established. This paper introduces a new method of impedance measurement for three-phase ac systems. By injecting an unbalanced line-to-line current between two lines of the ac system, all impedance information in the traditional synchronous reference frame d-q model can be determined. For medium-voltage systems, the proposed technique is simpler and less costly than having an injection circuit for each phase. Since the current injection is between only two phase lines, the proposed measurement device can be used for both ac and dc interfaces. Simulation and laboratory measurements demonstrate the effectiveness of this new technique.

Load impedance decision device, wireless power transmission device, and wireless power transmission method

Abstract: A load impedance decision device, a wireless power transmission device, and a wireless power transmission method are provided. At least one of a distance and an angle between two resonators may be measured. A load impedance may be determined based on at least one of the measured distance and the measured angle. When the distance between the two resonators changes, a high power transfer efficiency may be maintained without using a separate matching circuit. Where the load impedance is determined, a test power may be transmitted. Depending on a power transfer efficiency of the test power, the load impedance may be controlled and power may be wirelessly transmitted from the source resonator to the target resonator.

Linear Active Stabilization of Converter-Dominated DC Microgrids

Abstract: DC microgrids are gaining high momentum under the smart grid environment. DC microgrid stability can be an issue under high penetration of tightly regulated power converters used to interface distributed resources and loads. This paper addresses dc microgrid stability under high penetration of tightly regulated power electronic converters; and proposes three simple and computationally efficient active damping solutions that can be implemented to stabilize a controlled voltage-source converter (VSC) interfacing a dc- microgrid to an ac system. The proposed active damping methods depend on reshaping the VSC impedance by injecting internal-model-based active damping signal at the outer, intermediate and inner control loops of the voltage-oriented VSC interface. Small signal analysis is conducted to assess the system stability under different compensation schemes. Moreover, the reshaped source impedance of the VSC interface and the modified voltage-tracking dynamics are derived under different compensation schemes. Sensitivity and robustness analyses are provided to assess the dynamic coupling among active damping and voltage tracking controllers. Evaluation results, based on a detailed model of a dc microgrid with multiple tightly regulated converter-interfaced loads, are provided to validate the developed models and demonstrate the effectiveness and robustness of proposed techniques.

Semiconductor integrated circuit device having hierarchical power source arrangement

Abstract: A variable impedance power supply line and a variable impedance ground line supplying voltages VCL1 and VSL1, respectively, are set to a low impedance state in a stand-by cycle and in a row related signal set period, and to a high impedance state in a column circuitry valid time period. Variable impedance power supply line and variable impedance ground line supplying voltages VCL2 and VSL2, respectively, are set to a high impedance state in the stand-by cycle, and low impedance state in the active cycle and in the row related signal reset time period. Inverters operate as operating power supply voltage of voltages VCL1 and VSL2 or voltages VCL2 and VSL1, in accordance with a logic level of an output signal in the stand-by cycle and in the active cycle. Thus a semiconductor memory device is provided in which subthreshold current in the stand-by cycle and active DC current in the active cycle can be reduced.

Control topology options for single-phase UPS inverters

Abstract: Several control topologies for single-phase UPS inverters are presented and compared, with the common objective of providing a dynamically stiff, low THD, sinusoidal output voltage. Full state feedback, full state command controllers are shown utilizing both filter inductor current and filter capacitor current feedback to augment output voltage control. All controllers presented include output voltage decoupling in a manner analogous to "back-EMF" decoupling in DC motor drives. Disturbance input decoupling of the load current and its derivative is presented. An observer-based controller is additionally considered, and is shown to be a technically viable, economically attractive option. The accuracy transfer function of the observer estimate is used to evaluate its measurement performance. Comparative disturbance rejection is evaluated by overlaying the dynamic stiffness (inverse of output impedance) frequency response of each controller on a single plot. Experimental results for one controller are presented.