Amplified Spontaneous Emission in Single Frequency Double-Clad Fiber Power Amplifiers

Amplified spontaneous emission （ASE） in diode laser pumped double-clad fiber power amplifiers is studied experimentally, The dependences of ASE on fiber length and cross section of active core are discussed and the variations of ASE power as the function of pumping and signal power are investigated. There are indications that long fibers with large mode area need stronger input signals to suppress ASE. It is shown that a 150 mW input signal can suppress the ASE by 40 dB in a 4 m large mode area fiber, while to efficiently suppress the ASE in a 10 m fiber, stronger input signal is needed. 12.5 W and 16.1 W single frequency CW output power are obtained from 4 m fiber and 10 m fiber respectively. No stimulated Brillouin scattering （SBS） was observed

Two-stage robust power cost minimization in a natural gas compressor station

Optimal operation of a compressor station is important since it accounts for 25%to 50%of a company’s total operating budget.In short-term management of a compressor station,handling demand uncertainty is important yet challenging.Previous studies either require precise information about the distribution of uncertain parameters or greatly simplify the compressor model.We build a two-stage robust optimization framework of power cost minimization in a natural gas compressor station with nonidentical compressors.In the first stage,decision variables are the ON/OFF state of each compressor and discharge pressure.The worst-case cost of the second stage is incorporated in the first stage.Firststage decision variables feasibility is discussed and proper feasibility cuts are also proposed for the first stage.We employ a piece-wise approximation and propose accelerate methods.Our numerical results highlight two advantages of robust approach when managing uncertainty in practical settings:(1)the feasibility of first-stage decision can be increased by up to 45%,and(2)the worst-case cost can be reduced by up to 25%compared with stochastic programming models.Furthermore,our numerical experiments show that the designed accelerate algorithm has time improvements of 1518.9%on average(3785.9%at maximum).

The effects of radiation damage on power VDMOS devices with composite SiO_2-Si_3N_4 films

Total dose effects and single event effects on radiation-hardened power vertical double-diffusion metal oxide semiconductor（VDMOS） devices with composite SiO2-Si3N4 film gates are investigated.The relationships among the important electrical parameters of the samples with different thickness SiO2-Si3N4 films,such as threshold voltage,breakdown voltage,and on-state resistance in accumulated dose,are discussed.The total dose experiment results show that the breakdown voltage and the on-state resistance barely change with the accumulated dose.However,the relationships between the threshold voltages of the samples and the accumulated dose are more complex,and not only positively drift,but also negatively drift.At the end of the total dose experiment,we select the group of samples which have the smaller threshold voltage shift to carry out the single event effect studies.We find that the samples with appropriate thickness ratio SiO2-Si3N4 films have a good radiation-hardening ability.This method may be useful in solving both the SEGR and the total dose problems with the composite SiO2-Si3N4 films.

Robust switched fractional controller for performance improvement of single phase active power filter under unbalanced conditions

A novel controller is proposed to regulate the DC-link voltage of a single phase active power filter （SPAPF）. The proposed switched fractional controller （SFC） consists of a conventional PI controller, a fractional order PI （FO-PI） controller and a decision maker that switches between them. Commonly, the conventional PI controller is used in regulation loops due to its advantages in steady-state but it is limited in transient state. On the other hand, the FO-PI controller overcomes these draw- backs but it causes dramatic degradation in control performances in steady-state because of the fractional calculus theory and the approximation method used to implement this kind of controller. Thus, the purpose of this paper is to switch to the PI controller in steady-state to obtain the best power quality and to switch to the FO-PI controller when external disturbances are detected to guarantee a fast transient state. To investigate the efficiency and accuracy of the SFC considering all robustness tests, an experimental setup has been established. The results of the SFC fulfill the requirements, confirm its high performances in steady and transient states and demon- strate its feasibility and effectiveness. The experiment results have satisfied the limit specified by the IEEE harmonic standard 519.

A speaker driver for a single phase supply class G & I

A speaker driver applied to class G/classⅠwith a single phase power supply is presented.Gain expanding and compressing technology are employed in the signal processing circuit to optimize power dissipation.The circuit is implemented in 0.18μm N-well CMOS.Experimental results show that the speaker driver has a good audio sound quality and power efficiency.Less than 0.006%THD at a low power range and less than 0.4%at a medium power range can be obtained with a 1 kHz sine wave signal.Maximum output power of 360 mW can be gained at a load of 8Ω.The power efficiency is about twice that of a traditional class AB driver at the power range of 80 mW and shows more than 18%improvement at the higher output power range.

Simulation of the sensitive region to SEGR in power MOSFETs

Single event gate rupture（SEGR） is a very important failure mode for power MOSFETs when used in aerospace applications,and the cell regions are widely considered to be the most sensitive to SEGR.However, experimental results show that SEGR can also happen in the gate bus regions.In this paper,we used simulation tools to estimate three structures in power MOSFETs,and found that if certain conditions are met,areas other than cell regions can become sensitive to SEGR.Finally,some proposals are given as to how to reduce SEGR in different regions.

Optimal load frequency control through combined state and control gain estimation for noisy measurements

Combined estimation of state and feed-back gain for optimal load frequency control is proposed.Load frequency control(LFC)addresses the problem of controlling system frequency in response to disturbance,and is one of main research areas in power system operation.A well acknowledged solution to this problem is feedback stabilization,where the Linear Quadratic Regulator(LQR)based controller computes the feedback gain K from the known system parameters and implements the control,assuming the availability of all the state variables.However,this approach restricts control to cases where the state variables are readily available and the system parameters are steady.Alternatively,by estimating the states continuously from available measurements of some of the states,it can accommodate dynamic changes in the system parameters.The paper proposes the technique of augmenting the state variables with controller gains.This introduces a non-linearity to the augmented system and thereby the estimation is performed using an Extended Kalman Filter.This results in producing controller gains that are capable of controlling the system in response to changes in load demand,system parameter variation and measurement noise.