Harmonic Detection System Research Articles

Torque Ripple Reduction of PMSM Based on Modified DBN-DNN Surrogate Model

Due to the nonlinearity and dead time of the inverter, a great number of harmonic components is introduced into the motor input current, causing the torque ripple of the motor. The paper aims to suppress the torque ripple of a low-speed and high-torque permanent magnet synchronous motor (PMSM) with a two-step stator voltage optimization method, including a high precision harmonic voltage injection (HPHVC) method and a deep belief network (DBN)-deep neural network (DNN) voltage prediction model. Firstly, a closed-loop harmonic current detection system with Type-II Chebyshev filter is adopted to enhance the harmonic current extraction accuracy. Secondly, a harmonic voltage algorithm is designed considering the dq-axis current coupling relationship, which improves the accuracy of harmonic voltage calculation. Thirdly, a dq-axis voltage prediction model is constructed using DBN-DNN algorithm as the surrogate model, which further reduces the current harmonic components caused by the harmonic injection structure and the PI control algorithm, reduces the torque pulsation of the motor, and boosts the dynamic performance of the motor. Finally, the experimental platform is constructed by embedding the proposed strategy into the field oriented control system for reducing the torque pulsation. The experimental results verify the proposed strategy.

Analysis and Technology Realization of Power Grid Harmonic Detection System Based on ARM Embedded System

In our industrial production, ideally what we get from the grid should be a single power frequency. However, the actual situation is that with the generation, transformation, transmission, distribution and power consumption of the entire power system, as long as the current flows through the nonlinear load, harmonics are likely to be generated. So the detection of these harmonics and effective governance has become one of the requirements of China's power protection. Based on this situation, this paper discusses the analysis and technical implementation of ARM embedded harmonic detection system.

Harmonic Detection System and Identification Algorithm for Steel Pipeline Defects

Aiming at the problem of defects detection of steel pipeline, a harmonic detection system was developed based on electromagnetic principle, and the target signal identification algorithm was studied. The Advanced RISC Machine (ARM) Cortex-M3 was adopted to design digital adjustable harmonic excitation source, and its effective output power can up to 70 W. The Field Programmable Gate Arrays (FPGA) and ARM Cortex-M4 were introduced to design 15 channels high speed data collector, which parallel local-storage rate of each channel can reach 4.7 kHz. The electromagnetic focusing excitation array and Tunnel Magneto Resistance (TMR) sensors array were constructed to improve the spatial resolution of the detection system. Meanwhile, the system also integrated GPS positioning and LCD real-time display functions. Furthermore, the algorithm combining Empirical Mode Decomposition (EMD) and variable-scale Stochastic Resonance (SR) was proposed to process signal and enhance the targets. The effectiveness of the instrument and algorithm are well verified in both simulation and experiment. The results show that this method has higher integration and better detection effect, which provides a novel method for non-contact detection of metal material defects and is suitable for engineering applications.

Research on Harmonic Detection System Based on Wavelet Packet Transform

This paper introduces the basic concepts of harmonics in power system, and expounds the basic principles of harmonic detection algorithms such as Fourier transform, short wavelet transform and wavelet packet transform. The effectiveness of the proposed algorithm is verified by simulation, which shows that the improved wavelet packet algorithm can achieve the uniform division of the harmonic signal frequency band, and improve the detection accuracy of the harmonic signal. Wavelet packet transform could detect the fundamental and harmonic components of the original signal, which is most suitable for the detection of harmonic signals.

Active Harmonic Filtering Using Current-Controlled, Grid-Connected DG Units With Closed-Loop Power Control

The increasing application of nonlinear loads may cause distribution system power quality issues. In order to utilize distributed generation (DG) unit interfacing converters to actively compensate harmonics, this paper proposes an enhanced current control approach, which seamlessly integrates system harmonic mitigation capabilities with the primary DG power generation function. As the proposed current controller has two well-decoupled control branches to independently control fundamental and harmonic DG currents, local nonlinear load harmonic current detection and distribution system harmonic voltage detection are not necessary for the proposed harmonic compensation method. Moreover, a closed-loop power control scheme is employed to directly derive the fundamental current reference without using any phase-locked loops (PLL). The proposed power control scheme effectively eliminates the impacts of steady-state fundamental current tracking errors in the DG units. Thus, an accurate power control is realized even when the harmonic compensation functions are activated. In addition, this paper also briefly discusses the performance of the proposed method when DG unit is connected to a grid with frequency deviation. Simulated and experimental results from a single-phase DG unit validate the correctness of the proposed methods.

Three-Phase Cascaded Delayed Signal Cancellation PLL for Fast Selective Harmonic Detection

Fast and accurate selective harmonic detection has crucial value for many power system harmonic compensation systems. The existing detection methods are known to have a few drawbacks, such as long delay time, sensitivity to grid frequency variation, and difficulty to achieve zero steady-state error. In order to overcome these drawbacks, this paper proposes a selective harmonic detection system based on the three-phase cascaded delayed signal cancellation phase-locked loop. The system can be flexibly configured to detect any individual harmonic from the source with various background harmonics. It also features very short transient and excellent adaptability under small and considerable frequency variations, as verified by comprehensive experimental results. Finally, this paper provides guidance on how to tailor the detection system for different applications and a solution to address the practical implementation issues.

Harmonic Detection Instrument Based on Embedded System

With large scale application of the power electronic devices and frequency conversion devices, the harmonic pollution in the grid becomes more and more serious. It has brought serious harm to the electrical equipment and the safe and stable operation of the power system. In view of this, this paper built a harmonic detection system based on Ethernet. MCU C8051F040 is used as the field detection instrument, and ARM9 processor is used to build the Ethernet gateway. Field data can be sent to the gateway from MCU by RS485 bus. By writing the related web server code and CGI code, the remote monitoring data can be achieved through the IE browser.

Detection of Second-Harmonic Components of Lamb Waves Generated from Fatigue Plate Using a Double-Layered Piezoelectric Transducer

Detections of second harmonic components generated from closed cracks created by fatigue tests using finite amplitude Lamb wave were carried out using double-layered piezoelectric transducer (DLPT) with pulse-echo method. Three pure magnesium (Mg) plates applied to fatigue test were used in this experiment. In a received waveform from the plate had fatigue test of 2 × 105 cycles, second harmonic component was increased by 6 dB compared with in the plate had 0 cycles. Thus, it was confirmed that second harmonic components detection system using DLPT was effective for detecting dislocations and closed cracks in the plates.

Multiple Harmonic Source Detection and Equipment Identification With Cascade Correlation Network

This paper presents the design of a harmonic source detection system with a cascade correlation network (CCN). Current-injection-based harmonic power flow was used to calculate bus voltages and total harmonic distortion (THD). THD of voltages is used as indices for meter placement in the power network. At metering buses, it shows that the harmonic components of voltages under various loads would form particular patterns in the frequency domain, and can be used to create training examples for CCN. Good meter planning is helpful to reduce the number of meters and training examples. With an IEEE 14-bus power system, computer simulations were conducted to show the effectiveness of the proposed system.

A Method of Harmonics Current Detection for an Active Power Filter Using pq-Theory and Moving Average High-Pass Filter

In a harmonic detection system of active power filters, the pq-theory can be used for the calculation of harmonic current detection. A high pass filter of the first order is usually used for the detection of the ac component of instantaneous real power (p) and instantaneous imaginary power (q). But, in that system transient response for a load change is not high enough. We propose a new detection system in which ac components are derived from p and q using a moving average high-pass filter. By the proposed system, control response and accuracy are very good even in the case of an abrupt load change. The operating performance of the proposed system is confirmed by laboratory model test.

Low Level Second Harmonic Detection System

A second harmonic detection system suitable for detailed study of current-voltage characteristics, particularly tunneling characteristics of superconductor and semiconductor junctions, is described. The system is capable of detecting second harmonic voltage changes as low as 10−9 V which allows the fundamental signal level to be ≤kT at a junction temperature of 1°K. A selection-rejection impedance transformation reactance network which is the heart of the system is described. The quantitative relationships between second harmonic voltage and second derivative of current with respect to voltage are given. The capabilities of the system are illustrated by a photograph of an X-Y recorder tracing of second harmonic voltage vs dc bias voltage for an Al-I-Pb tunnel junction.