Active Compensation Device Research Articles

Research on improved Harmonic current detection method based on SOGI-PLL instantaneous reactive Power

In view of the traditional instantaneous reactive power detection has low anti-harmonic interference ability, poor real-time performance, and insufficient accuracy when the power grid frequency fluctuates, this paper improved the detection link. The working principle of single-phase harmonic detection is analyzed, and the improved second-order generalized integrator is added to make the phase-locked loop detect the voltage phase accurately and efficiently. Based on the comparison and compensation simulation results of the active compensation device, the quality of grid-connected current of the inverter is improved effectively, and the precision of phase locking is increased.

Large-Scale 3D Baseline Measurement Based on Phase-Stabilized GNSS-Over-Fiber System

Multi-antenna GNSS-over-fiber system is considered an effective solution for three-dimension (3D) baseline measurement. By precisely determining the transmission time delays between the antennas and the receiver, the vertical precision can be improved based on the single difference (SD) model. This method, however, would encounter problems if the baseline is too long, since a high precision measurement of the time delay of a long fiber link is usually time-consuming. Here, we propose and demonstrate a high-speed phase-stabilized GNSS-over-fiber system for large-scale 3D baseline measurement. A relatively slow but accurate time delay measurement module is used to calibrate the link delay, then a fast active compensation device is employed to keep the time delay constant. If the delay variation exceeds the compensation range, the time delay measurement module would measure the link delay again and bias the active compensation device at a new operating state. In a proof-of-concept experiment, the precision of the 3D baseline measurement obtained by the proposed system with a 20-km optical fiber is around 2.82 mm thanks to the rigid active compensation and the high-precision time delay measurement. If the active compensation device is disabled, the vertical precision of the baseline measurement obtained would be degraded from 2.82 mm to 16.46 mm in 10 minutes.

General average model of T-type three-level converter for active compensation circuit of distribution network

The active compensation device, between the distribution network’s neutral point and the ground, compensates for the single-phase short-circuit current. And the T-type three-level circuit is a possible scheme for compensation devices. This paper proposes the T-type average model based on the above topology, with a controlled voltage/current source, regardless of modulation or control methods. Compared with the two-level converter topology, the three-level converter topology improves the rated voltage stress, with few switching devices’ requirements. The modeling and simulation indicate that the T-type’s average model is identical to its switch model. And the T-type three-level converter can achieve the desired active compensation.

YN/VD connected balance transformer-based hybrid power quality compensator for harmonic suppression and reactive power compensation of electrical railway power systems

In this study, YN/VD connected balance transformer-based hybrid power quality compensator (HPQC) is proposed for harmonic suppression and reactive power compensation in electrified railways. The HPQC is composed of a balance transformer in YN/VD connection, a controllable three-phase voltage source inverter (VSI), as well as fully-tuned passive power filters (PPFs). It is able to integrate the active compensation device with the main transformer, without using auxiliary step-down transformer. This circuit configuration enables one to adopt VSI with low power rating, so that merits such as easy for system integration and low operation losses can be achieved. In this paper, the equivalent circuit model and the corresponding mathematical model of the HPQC in the harmonic domain are established to reveal its mechanism on harmonic suppression. And then, the working principle and control strategy of such a new topology are elaborated in detail. Finally, simulation and experimental results are provided to verify the feasibility and effectiveness of the above-mentioned structure and control strategy.

Study of optical design of Blu-ray pickup head system with a liquid crystal element.

This paper proposes a newly developed optical design and an active compensation method for a Blu-ray pickup head system with a liquid crystal (LC) element. Different from traditional pickup lens design, this new optical design delivers performance as good as the conventional one but has more room for tolerance control, which plays a role in antishaking devices, such as portable Blu-ray players. A hole-pattern electrode and LC optics with external voltage input were employed to generate a symmetric nonuniform electrical field in the LC layer that directs LC molecules into the appropriate gradient refractive index distribution, resulting in the convergence or divergence of specific light beams. LC optics deliver fast and, most importantly, active compensation through optical design when errors occur. Simulations and tolerance analysis were conducted using Code V software, including various tolerance analyses, such as defocus, tilt, and decenter, and their related compensations. Two distinct Blu-ray pickup head system designs were examined in this study. In traditional Blu-ray pickup head system designs, the aperture stop is always set on objective lenses. In the study, the aperture stop is on the LC lens as a newly developed lens. The results revealed that an optical design with aperture stop set on the LC lens as an active compensation device successfully eliminated up to 57% of coma aberration compared with traditional optical designs so that this pickup head lens design will have more space for tolerance control.

A General Space Vector PWM Scheme for Multilevel Inverter

This paper introduces a simple space vector PWM algorithm for a cascaded multilevel inverter. The scheme determines the location of the reference vector easily. It uses space state equation to get the value of vector. A cascaded thirteen-level inverter is used to explain the scheme. The scheme can be easily extended to n-level inverter. It is applicable to cascaded multilevel high voltage inverter and cascaded active compensation device. The result of simulation verifies that the scheme is useful in improving utilization of the direct current (dc) link voltage and reducing THD.

An Improved Active Common-Mode Voltage Compensation Device for Induction Motor Drives

This paper presents a new device for the compensation of common-mode (CM) disturbance in induction motor drives, based on the active cancellation approach. The detailed design and the experimental implementation issues of the new active compensation device for a 380-V/50-Hz pulsewidth-modulation (PWM) induction motor drive are discussed. Starting from the idea of the active common-noise canceller, the proposed active compensation device is suitably improved in order to overcome the limitations of similar previously proposed circuits. In fact, it can be successfully used within a drive system with a rated voltage of 380 V or higher by employing an improved active circuit with a dedicated dc power supply derived from the ac power supply line. In addition, the design follows the criteria of compactness and minimum cost. The performance of the realized active compensation device is verified through experimental measurements of the CM voltage, the CM current, and the motor shaft voltage. The effectiveness of the proposed solution is demonstrated by experimental results.

Some considerations on active compensation devices

AbstractThe knowledge of the methodologies and devices bothtavoiding the disturbing injections in electrical networks and limiting the effects of disturbances existing before is a well‐known problem. In the present paper the results expected by using some active apparatuses for disturbances compensation are examined. The limits of different solutions are detected and some design elements are provided as well.