Statistical Properties of a Ring Laser with Injected SIgnal and Backscattering

The statistical properties of a homogeneously broadened ring laser with an injected signal are investigated and the normalized two-mode intensity auto- and cross-correlation functions are calculated by a full saturation laser theory with backscattering. The theoretical predictions are in good agreement with the experimental measurements.Further investigation reveals that the backscattering can reduce the fluctuations in the system while the full saturation effect plays a major role when the laser is operated above threshold. It is also quite important to notice that the injected signal can drive the weak mode from incoherent light to coherent light.

Single Phase-to-Ground Fault Line Identification and Section Location Method for Non-Effectively Grounded Distribution Systems Based on Signal Injection

A diagnostic signal current trace detecting based single phase-to-ground fault line identifica- tion and section location method for non-effectively grounded distribution systems is presented in this paper.A special diagnostic signal current is injected into the fault distribution system,and then it is detected at the outlet terminals to identify the fault line and at the sectionalizing or branching point along the fault line to locate the fault section.The method has been put into application in actual distribution network and field experience shows that it can identify the fault line and locate the fault section correctly and effectively.

Adaptive restarting method for LCC-HVDC based on principle of fault location by current injection

The existing LCC-HVDC transmission project adopts the fixed-time delay restarting method.This method has disadvantages such as non-selectivity,long restart process,and high probability of restart failure.These issues cause a secondary impact on equipment and system power fluctuation.To solve this problem,an adaptive restarting method based on the principle of fault location by current injection is proposed.First,an additional control strategy is proposed to inject a current detection signal.Second,the propagation law of the current signal in the line is analyzed based on the distributed parameter model of transmission line.Finally,a method for identifying fault properties based on the principle of fault location is proposed.The method fully considers the influence of the long-distance transmission line with earth capacitance and overcomes the influence of the increasing effect of the opposite terminal.Simulation results show that the proposed method can accurately identify the fault properties under various complex fault conditions and subsequently realize the adaptive restarting process.

Sensorless Control of IPMSM for Last 10 Years and Next 5 Years

This paper presents the developments of sensorless control of interior permanent magnet synchronous machine(IPMSM)for last 10 years,which could be divided into the past and the present for each 5 years.Several popular methods developed for last 10 years would be described and evaluated,and the limitations with the methods are discussed.In the past a concept extended EMF(EEMF)was introduced and it can model IPMSM as a non-salient motor,meaning that the representation of IPMSM in the estimated rotor reference frame would be much simpler and accurate.However,because it still relied on back EMF,standstill operation was impossible.And,the position control of IPMSM could not be achieved with EEMF concept.For sensorless drive,the high-frequency signal injection method exploiting inherent saliency of IPMSM has been continuously developed for last 10 years and applied to various industry fields,where torque control at standstill is essential.Its performance has been improved but there are still many problems to be solved.In the present,the square-wave signal injection at estimated d-axis has improved the control performance conspicuously.However,there are strong demands to improve the control performance of sensorless drive,yet.Based on the problems in the present,in this paper the possible developments of sensorless drive of IPMSM in next 5 years are enlightened as the future of sensorless control.

Research on performance testing of radio fuse based on virtual separation technology

The conception of virtual separation technology about high low frequency of electronic module was put forward based on the analysis of tactical performance testing of radio fuse.By means of the principle of fuse Doppler signal acquisition and injection,the high low frequency of electronic module was virtually separated,and one of important parameters—burst height of radio fuse is tested precisely.

Fault identification scheme for protection and adaptive reclosing in a hybrid multi-terminal HVDC system

A fault identification scheme for protection and adaptive reclosing is proposed for a hybrid multi-terminal HVDC system to increase the reliability of fault isolation and reclosing.By analyzing the"zero passing"characteristic of current at the local end during the converter capacitor discharge stage,the fault identification scheme is proposed.The distributed parameter-based fault location equation,which incorporates fault distance and fault impedance,is developed with the injection signal and the distributed parameter model during the adaptive reclosing stage.The fault distance is determined using a trust region reflection algorithm to identify the permanent fault,and a fault iden-tification scheme for adaptive reclosing is developed.Simulation results show that the proposed scheme is suitable for long-distance transmission lines with strong anti-fault impedance and anti-interference performance.Also,it is less affected by communication delay and DC boundary strength than existing methods.

An MRAS method for sensorless control of induction motor over a wide speed range

This paper addresses the problem of wide speed range sensorless control of induction motor.The proposed method is based on model reference adaptive system (MRAS),in which the current model serves as the adjustable model,and a novel hybrid model integrating the modified voltage model (MVM) and high-frequency signal injection method (HFSIM) are established to serve as the reference model.The HFSIM works together with MVM to improve the performance of the rotor speed and rotor flux position estimation at low speed,whereas at high speed,the MVM acts alone.In addition,a rotor resistance online estimation scheme is proposed to update the rotor resistance contained in the adjustable model and to ensure the estimation accuracy further.Experimental results show that the proposed MRAS method is very effective from low to high speed range,including zero speed.

Sensorless Control of Permanent Magnet Synchronous Motor in Full Speed Range

Aiming at resolving the limitation of the speed regulation range of sensorless control technology,a new composite sensorless control strategy is proposed to realize a control method for a permanent magnet synchronous motor(PMSM)in full speed range.In the medium-and high-speed range,the improved new sliding mode observer method is used to estimate the motor speed and rotor position information.In the zero and low speed range,in order to avoid the defects of the sliding mode method,the rotating high-frequency voltage signal injection method is used.When switching between low,medium,and high speed,the fuzzy control algorithm is adopted to achieve smooth transitions.The simulation experiment results show that the hybrid mode combining the sliding mode observer and rotating high-frequency voltage injection methods,can effectively reduce the jitter in the algorithm switching process,and realize the smooth control of a PMSM in full speed range.

Saliency-Based Position Sensorless Control Methods for PMSM Drives-a Review

Permanent magnet synchronous motor(PMSM)drives are finding expanded use for industrial and domestic drive applications.With the distinguished characteristics such as reduced cost and increased reliability and robustness,position sensorless(self-sensing)control techniques have been good candidates for reliable and costless PMSM drives.The saliency-tracking based techniques further bring the expansion of applications with the extended controllable sensorless operating speed range.This paper presents a review on state of the art techniques for position sensorless drives using the saliency-tracking based methods.The signal injection methods and the future scope of research including the dynamic bandwidth improvement and the acoustic noise reduction are discussed.