TL;DR: In this article, an active rectifier and voltage regulator are modeled in nonlinear state-space form, linearized around an operating point, and joined to network and inverter models, and participation analysis of the combined system identified that the low-frequency modes are associated with the voltage controller of the active rectifiers and the droop controllers of the inverters.
Abstract: Rectifiers and voltage regulators acting as constant power loads form an important part of a microgrid’s total load. In simplified form, they present a negative incremental resistance and beyond that, they have control loop dynamics in a similar frequency range to the inverters that may supply a microgrid. Either of these features may lead to a degradation of small-signal damping. It is known that droop control constants need to be chosen with regard to damping, even with simple impedance loads. Actively controlled rectifiers have been modeled in nonlinear state-space form, linearized around an operating point, and joined to network and inverter models. Participation analysis of the eigenvalues of the combined system identified that the low-frequency modes are associated with the voltage controller of the active rectifier and the droop controllers of the inverters. The analysis also reveals that when the active load dc voltage controller is designed with large gains, the voltage controller of the inverter becomes unstable. This dependence has been verified by observing the response of an experimental microgrid to step changes in power demand. Achieving a well-damped response with a conservative stability margin does not compromise normal active rectifier design, but notice should be taken of the inverter–rectifier interaction identified.
TL;DR: In this article, an electronic current control circuit is provided, consisting of a power-supply, an H-bridge module connected to a load, and a current sensor connected between the H-Bridge module and the power supply.
Abstract: An electronic current control circuit is provided. This electronic circuit comprises a power-supply, an H-Bridge module connected to a load, and a current sensor connected between the H-Bridge module and the power-supply and adapted to sense load current characteristics. A computerized controller is connected to the current sensor and the H-Bridge module, includes at least a module for operating load current analysis algorithm for analyzing the load current characteristics to determine current control parameters that provide over-current protection and load current control. A load current control module controls the H-Bridge module based upon the current control parameters.
TL;DR: In this article, the authors present design criteria for qubit drive lines, flux lines, and output lines used in typical experiments with superconducting circuits and describe each type of line in detail.
Abstract: A robust cryogenic infrastructure in form of a wired, thermally optimized dilution refrigerator is essential for solid-state based quantum processors. Here, we engineer a cryogenic setup, which minimizes passive and active heat loads, while guaranteeing rapid qubit control and readout. We review design criteria for qubit drive lines, flux lines, and output lines used in typical experiments with superconducting circuits and describe each type of line in detail. The passive heat load of stainless steel and NbTi coaxial cables and the active load due to signal dissipation are measured, validating our robust and extensible concept for thermal anchoring of attenuators, cables, and other microwave components. Our results are important for managing the heat budget of future large-scale quantum computers based on superconducting circuits.
TL;DR: Load Modulated Balanced Amplitude Adjustment (LMBA) as discussed by the authors is a power amplifier architecture that allows the load seen by the active devices can be modulated upward or downwards, both resistively and reactively, with minimal loss of power combination efficiency.
Abstract: A novel power amplifier (PA) architecture, the Load Modulated Balanced PA (LMBA), is presented. The LMBA is able to modulate the impedance seen by a pair of RF power transistors in a quadrature balanced configuration, by varying the amplitude and phase of an external control signal. This enables power and efficiency to be optimized dynamically at specific power backoff levels and frequencies. Unlike the Doherty PA, the load seen by the active devices can be modulated upwards or downwards, both resistively and reactively, with minimal loss of power combination efficiency. The LMBA is presented as a potentially disruptive technique which enables any specific amplifier characteristic to be controlled dynamically over wide signal amplitude and frequency ranges.
TL;DR: It is concluded that the combination of the voltage-droop control strategy with the presented demand dispatch allows reliable power supply without interunit communication for the primary control, leads to a more efficient usage of the renewable energy and can even lead to an increased share of renewables in the islanded microgrid.
Abstract: In the islanded operating condition, the microgrid has to maintain the power balance independently of a main grid. Because of the specific characteristics of the microgrid, such as the resistive lines and the high degree of power-electronically interfaced generators, new power control methods for the generators have been introduced. For the active power control in this paper, a variant of the conventional droop P/f control strategy is used, namely the voltage-droop controller. However, because of the small size of the microgrid and the high share of renewables with an intermittent character, new means of flexibility in power balancing are required to ensure stable operation. Therefore, a novel active load control strategy is presented in this paper. The aim is to render a proof of concept for this control strategy in an islanded microgrid. The active load control is triggered by the microgrid voltage level. The latter is enabled by using the voltage-droop control strategy and its specific properties. It is concluded that the combination of the voltage-droop control strategy with the presented demand dispatch allows reliable power supply without interunit communication for the primary control, leads to a more efficient usage of the renewable energy and can even lead to an increased share of renewables in the islanded microgrid.