GVD compensation schemes with considering PMD

Three group velocity dispersion (GVD) compensation schemes, i.e., the post-compensation, pre-compensation and hybrid-compensation schemes, are discussed with considering polarization mode dispersion (PMD). In the 10- and 40-Gbit/s non-return-zero (NRZ) on-off-key (OOK) systems, three physical factors, Kerr effect, GVD and PMD are considered. The numerical results show that, when the impact of PMD is taken into account, the GVD pre-compensation scheme performs best with more than 1 dB better of average eye-opening penalty (EOP) when input power is up to 10 dBm in the 10-Gbit/s system. However the GVD post-compensation scheme performs best for the case of 40 Gbit/s with input power less than 13 dBm, and GVD pre-compensation will be better if the input power increased beyond this range. The results are different from those already reported under the assumption that the impact of PMD is neglected. Therefore, the research in this paper provide a different insight into the system optimization when PMD, Kerr effect and GVD are considered.

A Scheme of Dynamic Voltage Restorer to Improve Power Quality in Large Scale Industrial Enterprises

Loads in large scale industrial enterprises are always various and complex, causing insecure power quality. Meanwhile, some sensitive loads or precise instruments demand for high power quality. When voltage flicker or harmonics occurs, dynamic voltage restorer (DVR) can be used to stabilize the load-side voltage, which is a good manner of improving power quality. The paper explains the load demand in large scale industrial enterprises, analyzes several common voltage compensation scheme of DVR, and comes up with another voltage compensation scheme of DVR applied for double power supply with double load. A Simulink model according to the new scheme is also built in MATLAB/Simulink to test its performance. Simulation results show that the proposed scheme can guarantee the load-side voltage stability, which is an effective scheme for managing power quality.

Inertia compensation scheme for wind turbine simulator based on deviation mitigation

Wind turbine simulator(WTS) is an important test rig for validating the control strategies of wind turbines(WT). Since the inertia of WTSs is much smaller than that of WTs, the inertia compensation scheme is usually employed in WTSs for replicating the slow mechanical behavior of WTs. In this paper, it is found that the instability of WTSs applying the inertia compensation scheme,characterized by the oscillation of compensation torque, is caused by the one-step time delay produced in the acceleration observation. Hence, a linear discrete model of WTS considering the time delay of acceleration observation is developed and its stability is analyzed. Moreover, in order to stably simulate WTs with large inertia, an improved inertia compensation scheme, applying a first-order digitalfilter to mitigate deviation response induced by the time delay, is proposed. And, the criterion for selecting the filter coefficients is established based on the stability condition analysis. Finally, the WTS with the proposed scheme is validated by simulations and experiments.

Zero-Loss Broadband Dispersion Compensation Scheme for G.652 Fibers

We have evaluated the gain characteristics of an erbium-doped broadband dual-core dispersion compensating fiber (DCF) to achieve a loss-less dispersion compensating module for long-haul G.652 fiber links.

Optimum Control Scheme of Output Voltage Based on Cascaded H-bridge DVR

This study presents an optimum control scheme to maximize the output voltage level number of the cascaded Hbridge dynamic voltage restorer(CHB–DVR).The relationship between the modulation index and the output voltage level number is analyzed in detail.The compensation reference voltage value is adjusted with the voltage drop depth to obtain high-quality output voltage with an acceptable total harmonic distortion.Thus,the modulation index remains within a certain range and thus meets the requirements of the maximum level number technique(MLNT).In addition,an improvement method based on the MLNT is proposed to achieve minimum active power absorption from a direct current link of the CHB–DVR.The traditional in-phase compensation and optimum control strategies are implemented to analyze the output voltage quality for verifying the feasibility of the proposed approach.Simulation and experimental results show the effectiveness of the proposed control scheme.