Novel Control Strategy for Multi-Level Active Power Filter without Phase-Locked-Loop

Active power filter (APF) using novel virtual line-flux-linkage oriented control strategy can not only realizes no phase-locked-loop (PLL) control, but also achieves a good inhibitory effect to interfere. However, there are some problems in the conventional method, such as the error of amplitude, the shift of phase angle and the non-determinacy of initial oriented angle. In this paper, two one-order low-pass filters are adopted instead of the pure integrator in the virtual line-flux-linkage observer, which can steady the phase and amplitude. Furthermore, an original scheme of harmonics detection under the rotating coordinate is advanced based on the simplified space vector pulse width modulation (SVPWM) strategy. Meanwhile, by using the new SVPWM algorithm, the voltage space vector diagram of the three-level inverter can be simplified and applied into that of two-level inverter, and this makes the control for Neutral Point potential easier.

Possible Approach to Improve Sensitivity of a Michelson Interferometer

We propose a possible approach to achieve a 1/N sensitivity of Michelson interferometer by using a properly designed random phase modulation. Different from other approaches, the sensitivity improvement does not depend on increasing optical powers or utilizing the quantum properties of light. Moreover the requirements for optical losses and the quantum efficiencies of photodetection systems may be lower than the quantum approaches and the sensitivity improvement is independent of frequency in all the detection bands.

Impacts of PLL on the DFIG-based WTG’s Electromechanical Response Under Transient Conditions:Analysis and Modeling

Increased penetration of wind energy in the electric grid has necessitated studying the impact of wind integration on the transient stability of the power system,with urgency to develop appropriate electromechanical models of the wind turbine generator(WTG).The representation and control of the WTG’s electric signals are typically in a rotational dq coordinate system whose reference angle is provided by a phase-lockedloop(PLL).The PLL is commonly considered as a measurement device and is often absent in existing WTG electromechanical models.This paper studies the impact of PLL on the DFIG-based WTG electromechanical response by theoretical and simulation analyses.The dynamics of the PLL are found to greatly influence the WTG electromechanical response,suggesting that PLL should be regarded as an indispensable control loop rather than a measurement device,and its impact should be modeled when establishing the WTG electromechanical model.

A single-event-hardened phase-locked loop using the radiation-hardened-by-design technique

A radiation-hardened-by-design phase-locked loop（PLL） with a frequency range of 200 to 1000 MHz is proposed.By presenting a novel charge compensation circuit,composed by a lock detector circuit,two operational amplifiers,and four MOS devices,the proposed PLL significantly reduces the recovery time after the presence of a single event transient（SET）.Comparing with many traditional hardened methods,most of which endeavor to enhance the immunity of the charge pump output node to an SET,the novel PLL can also decrease its susceptibility in the presence of an SET in other blocks.A novel system model is presented to describe immunity of a PLL to an SET and used to compare the sensitivity of traditional and hardened PLLs to an SET.An SET is simulated on Sentaurus TCAD simulation workbench to model the induced pulse current.Post simulation with a 130 nm CMOS process model shows that the recovery time of the proposed PLL reduces by up to 93.5%compared with the traditional one,at the same time,the charge compensation circuit adds no complexity to the systemic parameter design.