从高压侧进行电能质量在线监测的需求日益增强。针对此现状,本文研究了各种高压在线监测装置的优缺点,提出了高压在线监测装置的发展方向及其核心技术,并对各种装置及核心元器件的国内外研究现状进行了介绍。

从高压侧进行电能质量在线监测的需求日益增强。针对此现状,本文研究了各种高压在线监测装置的优缺点,提出了高压在线监测装置的发展方向及其核心技术,并对各种装置及核心元器件的国内外研究现状进行了介绍。

The choice of the cut-off frequency reflects a tradeoff between maladjustment and the speed of dynamic response in the conventional detection method based on instantaneous reactive power theory. The paper proposes a novel digital real-time algorithm for detecting harmonic currents. This algorithm adopts a new variable step size least mean square(LMS) adaptive filter as LPF on harmonic detection circuit. The step-size is large when the algorithm is far from the optimum with decreasing as it approaches the optimum. The proposed algorithm allows more flexible control of misadjustment and fast convergence rate without the need to compromise one for the other. Meanwhile approximate theoretical expressions for the behavior of the algorithm are derived. The additional calculation is very little, so the algorithm presented is easy to implement. Simulation and experiment results illustrate that the performance of the proposed approach is satisfactory.

The choice of the cut-off frequency reflects a tradeoff between maladjustment and the speed of dynamic response in the conventional detection method based on instantaneous reactive power theory. The paper proposes a novel digital real-time algorithm for detecting harmonic currents. This algorithm adopts a new variable step size least mean square(LMS) adaptive filter as LPF on harmonic detection circuit. The step-size is large when the algorithm is far from the optimum with decreasing as it approaches the optimum. The proposed algorithm allows more flexible control of misadjustment and fast convergence rate without the need to compromise one for the other. Meanwhile approximate theoretical expressions for the behavior of the algorithm are derived. The additional calculation is very little, so the algorithm presented is easy to implement. Simulation and experiment results illustrate that the performance of the proposed approach is satisfactory.

In synchronous rotating coordinate systems corresponding to various orders of harmonics, the proportion integration (PI) regulators are used to compensate various orders of harmonics by closed-loop control of grid-side current to effectively eliminate the affections of sampling precision, control system delay, dead zone of pulse width modulation (PWM) on compensation effect to implement the control with zero steady-state error. On this basis, in allusion to the stability of active power filter when shunt capacitor is contained in the load, the analysis is performed by equivalent system. By adopting order-based closed-loop control, a solution that is simple and easy to realize is given. Results of digital simulation and physical experiments show that the proposed control method is effective.

In synchronous rotating coordinate systems corresponding to various orders of harmonics, the proportion integration (PI) regulators are used to compensate various orders of harmonics by closed-loop control of grid-side current to effectively eliminate the affections of sampling precision, control system delay, dead zone of pulse width modulation (PWM) on compensation effect to implement the control with zero steady-state error. On this basis, in allusion to the stability of active power filter when shunt capacitor is contained in the load, the analysis is performed by equivalent system. By adopting order-based closed-loop control, a solution that is simple and easy to realize is given. Results of digital simulation and physical experiments show that the proposed control method is effective.

The active power filter based on supply-side current detection is better than load current detection in harmonic compensation, while the application is rare because it has worse stability. The system is a closed-loop system because the feedback is supply-side current, including the transfer function producing resonance in the closed-loop. Using proper correction method can suppress the resonance, and the stability margin can be improved by adding phase lead correction to the system. However, after adding phase lead correction to the system, gain of low frequency band is low while increasing the phase margin, limit the improvement of compensation effect. This paper adds selective filter and proportion link to increase gain of specific frequency, which can increase the gain of low frequency band while increasing the phase margin. Its effectiveness is verified by the experiment results.

The active power filter based on supply-side current detection is better than load current detection in harmonic compensation, while the application is rare because it has worse stability. The system is a closed-loop system because the feedback is supply-side current, including the transfer function producing resonance in the closed-loop. Using proper correction method can suppress the resonance, and the stability margin can be improved by adding phase lead correction to the system. However, after adding phase lead correction to the system, gain of low frequency band is low while increasing the phase margin, limit the improvement of compensation effect. This paper adds selective filter and proportion link to increase gain of specific frequency, which can increase the gain of low frequency band while increasing the phase margin. Its effectiveness is verified by the experiment results.

Perovskite-type oxynitride BaTaO₂N has been attracting attention for its large dielectric constant, which is almost independent of the temperature by measurements on its ceramics. Its dielectric characteristics are attributed to polar nanoregions (PNRs) in the average cubic crystal structure. Polarization saturation to produce a butterfly-like piezoresponse force microscopy (PFM) signal was observed on BaTaO₂N crystals in the present study. Reddish crystallites of BaTaO₂N of up to 3.1 μm in size were grown using a BaCN₂ flux. Grain growth proceeded through the formation of a Ruddlesden-Popper-type oxynitride from the reaction between BaTaO₂N powder and molten BaCN₂. Their electrical property was studied using PFM with special care because of the small size of the crystals. They were found to be much more highly insulating than its ceramics. Ferroelectricity with complete phase inversion was observed on an oxynitride perovskite crystal for the first time. A large coercivity of 50-60 V was observed in the measurement. Such ferroelectricity is ascribed to the PNRs induced by the polar linkages between cis-type TaO₄N₂ octahedra.

Perovskite-type oxynitride BaTaO₂N has been attracting attention for its large dielectric constant, which is almost independent of the temperature by measurements on its ceramics. Its dielectric characteristics are attributed to polar nanoregions (PNRs) in the average cubic crystal structure. Polarization saturation to produce a butterfly-like piezoresponse force microscopy (PFM) signal was observed on BaTaO₂N crystals in the present study. Reddish crystallites of BaTaO₂N of up to 3.1 μm in size were grown using a BaCN₂ flux. Grain growth proceeded through the formation of a Ruddlesden-Popper-type oxynitride from the reaction between BaTaO₂N powder and molten BaCN₂. Their electrical property was studied using PFM with special care because of the small size of the crystals. They were found to be much more highly insulating than its ceramics. Ferroelectricity with complete phase inversion was observed on an oxynitride perovskite crystal for the first time. A large coercivity of 50-60 V was observed in the measurement. Such ferroelectricity is ascribed to the PNRs induced by the polar linkages between cis-type TaO₄N₂ octahedra.