A novel high precision Doppler frequency estimation method based on the third-order phase-locked loop

In deep space exploration,many engineering and scientific requirements require the accuracy of the measured Doppler frequency to be as high as possible.In our paper,we analyze the possible frequency measurement points of the third-order phase-locked loop(PLL)and find a new Doppler measurement strategy.Based on this finding,a Doppler frequency measurement algorithm with significantly higher measurement accuracy is obtained.In the actual data processing,compared with the existing engineering software,the accuracy of frequency of 1 second integration is about 5.5 times higher when using the new algorithm.The improved algorithm is simple and easy to implement.This improvement can be easily combined with other improvement methods of PLL,so that the performance of PLL can be further improved.

A novel Doppler frequency measurement method based on the closed-loop signal correlation for deep space exploration

In deep space exploration,it is necessary to improve the accuracy of frequency measurement to meet the requirements of precise orbit determination and various scientific studies.A phase detector is one of the key modules that restricts the tracking performance of phase-locked loop(PLL).Based on the phase relationship between adjacent signals in the time domain,a novel phase detector is presented to replace the arctangent phase detector.The new PLL,which is a closed loop signal correlation algorithm,shows good performance in tracking signals with high precision and the tracking accuracy of frequency of1 second integration is close to Cramer-Rao lower bound(CRLB)when setting proper parameters.Actual data processing results further illustrate the excellent performance of the novel PLL.

Principle and Implementation of an MC4044-Based Phase Locked Loop for Constant Speed Control

An inexpensive MC4044-based phase locked loop for constant speed control of a DC motor is discussed. It operates on a principle similar to that of a frequency synthesizer. The paper introduces the system configuration with a detailed description of its operating principle, some practical design considerations are discussed with an experimental study to test the control performance of the newly designed system. The experimental result shows that the phase locked control system can regulate the speed of a DC torque motor with a precision up to 0.0022%(1).[

Dual-Delay-Path Ring Oscillator with Self-Biased Delay Cells for Clock Generation

This work summarizes the structure and operating features of a high-performance 3-stage dual-delay-path (DDP) voltage-controlled ring oscillator (VCRO) with self-biased delay cells for Phase-Locked Loop (PLL) structurebased clock generation and digital system driving. For a voltage supply VDD = 1.8 V, the resulting set of performance parameters include power consumption PDC = 4.68 mW and phase noise PN@1MHz = -107.8 dBc/Hz. From the trade-off involving PDC and PN, a system level high performance is obtained considering a reference figure-of-merit ( FoM = -224 dBc/Hz ). Implemented at schematic level by applying CMOS-based technology (UMC L180), the proposed VCRO was designed at Cadence environment and optimized at MunEDA WiCkeD tool.

Simple and robust method for rapid cooling of 87Rb to quantum degeneracy

We demonstrate a simple and fast way to produce 87Rb Bose–Einstein condensates. A digital optical phase lock loop(OPLL) board is introduced to lock and adjust the frequency of the trap laser, which simplifies the optical design and improves the experimental efficiency. We collect atoms in a magneto-optical trap, then compress the cloud and cut off hot atoms by rf knife in a magnetic quadrupole trap. The atom clouds are then transferred into a spatially mode-matched optical dipole trap by lowering the quadrupole field gradient. Our system reliably produces a condensate with 2 × 106 atoms every7.5 s. The compact optical design and rapid preparation speed of our system will open the gate for mobile quantum sensing.

High-FM-linearity wideband chirp generator

An S-band wideband chirp generator using specially designed fast lock phase lock loop(FL-PLL) was demonstrated.To realize high linearity,structure of direct digital synthesizer(DDS) plus FL-PLL was used.DDS gives ideal linearity while FL-PLL retains the linearity and provides radio frequency.The system block diagrams were showed and the timing relationships of the components were provided.Two important considerations of the system,wideband loop and wideband voltage control oscillator(VCO),were discussed;meanwhile,after analyzing the considerations,corresponding solutions were presented.Measurement results show that the generated 2560MHz to 2960MHz chirp reaches a high FM linearity of 0.003%.

Fixed Point Iteration Chaos Controlled ZCDPLL

The stable operation of first and second order Zero Crossing Digital Phase Locked Loop (ZCDPLL) is extended by using a Fixed Point Iteration (FPI) method with relaxation. The non-linear components of ZCDPLL such as sampler phase detector and Digital Controlled Oscillator (DCO) lead to unstable and chaotic operation when the filter gains are high. FPI will be used to stabilize the chaotic operation and consequently extend the lock range of the loop. The proposed stabilized loop can work in higher filter gains which are needed for faster signal acquisition.

Improved PLL Tuning of Shunt Active Power Filter for Grid Connected Photo Voltaic Energy System

This research work brings out the unique predictive current control method for attaining an efficient grid connected Photo Voltaic (PV) system by Shunt Active Power Filter (SAPF) as grid connected converter. The major objective of the research work is to address the presence of Direct Current (DC) component, frequency improvement, quicker theta response, voltage magnitude estimation in the input signal of the Phase Locked Loop (PLL) which is challenging. This work focuses on tuning the PLL block (Kp, Ki, Kv and Ko) through Artificial Bee Colony (ABC) optimization algorithm. The proposed ABC based modified three-phase PLL method is based on adding a new loop inside the PLL structure. In power converters, ABC algorithm is used to select the optimal switching states. The voltage vector which minimizes a cost optimization function is selected. Simulation is carried out for both balanced and unbalanced system and the results validate that the performance of the proposed approach is better in terms of harmonic compensation as per the IEEE standards within ±5%, power factor improvement of the system, quicker theta tracking and suppression of frequency jump with the interconnection of PV system.

Coordinated Control of DFIG Converters to Comply with Reactive Current Requirements in Emerging Grid Codes

The doubly-fed induction generator(DFIG)is considered to provide a low-reactance path in the negative-sequence system and naturally comply with requirements on the negative-sequence reactive current in emerging grid codes.This paper shows otherwise and how the control strategy of converters plays a key role in the formation of the active and reactive current components.After investigating the existing control strategies from the perspective of grid code compliance and showing how they fail in addressing emerging requirements on the negative-sequence reactive current,we propose a new coordinated control strategy that complies with reactive current requirements in grid codes in the positive-and negative-sequence systems.The proposed method fully takes advantage of the current and voltage capacities of both the rotor-side converter(RSC)and grid-side converter(GSC),which enables the grid code compliance of the DFIG under unbalanced three-phase voltages due to asymmetrical faults.The mathematical investigations and proposed strategy are validated with detailed simulation models using the Electric Power Research Institute(EPRI)benchmark system.The derived mathematical expressions provide analytical clarifications on the response of the DFIG in the negative-sequence system from the grid perspective.

Design of Power System Stabilizer for DFIG-based Wind Energy Integrated Power Systems Under Combined Influence of PLL and Virtual Inertia Controller

Wind energy systems (WESs) based on doubly-fed induction generators (DFIGs) have enormous potential for meeting the future demands related to clean energy. Due to the low inertia and intermittency of power injection, a WES is equipped with a virtual inertial controller (VIC) to support the system during a frequency deviation event. The frequency deviation measured by a phase locked loop (PLL) installed on a point of common coupling (PCC) bus is the input signal to the VIC. However, a VIC with an improper inertial gain could deteriorate the damping of the power system, which may lead to instability. To address this issue, a mathematical formulation for calculating the synchronizing and damping torque coefficients of a WES-integrated single-machine infinite bus (SMIB) system while considering PLL and VIC dynamics is proposed in this paper. In addition, a power system stabilizer (PSS) is designed for wind energy integrated power systems to enhance electromechanical oscillation damping. A small-signal stability assessment is performed using the infinite bus connected to a synchronous generator of higher-order dynamics integrated with a VIC-equipped WES. Finally, the performance and robustness of the proposed PSS is demonstrated through time-domain simulation in SMIB and nine-bus test systems integrated with WES under several case studies.