Harmonic Detection Algorithm Research Articles

Performance and harmonic detection algorithm of phase locked Loop for parallel APF

As the boost of power electronics technology, the harmonic problem in the power system is becoming increasingly prominent. Fourier decomposition is performed on the load current in the power system, and components with a frequency that is an integer multiple of the fundamental wave are referred to as harmonic components. Harmonic control is essential to establish a safe and reliable power grid environment and provide high-quality and clean electricity to power users. The study focused on parallel active power filters, proposed a specific harmonic detection method on the grounds of synchronous harmonic rotating coordinate system, and developed a phase-locked loop design on the grounds of order generalized integrator. Meanwhile, a compensation current control method on the grounds of space vector pulse width modulation was introduced. The results showed that in the full compensation simulation experiment, the compensated A-phase grid side current waveform was significantly improved and presented a sinusoidal shape. After 0.05 s, the actual output compensation current closely followed the command current. Meanwhile, after compensation, the total harmonic distortion rate decreased from 26.58 to 3.06%. In specific harmonic compensation simulation experiments, when the sum of 5th, 7th, and 11th harmonic components was used as the command current for compensation, the distortion of the current waveform was improved after the load undergoes a sudden change. After compensation, the 5th, 7th, and 11th harmonic content significantly decreased, and the total harmonic distortion rate decreased to 4.08%. This indicated that the proposed phase-locked loop design and harmonic detection method for active power filters had high stability and effectiveness. The study’s primary contribution is to enhance the utilization efficiency of DC voltage and improve the dynamic response ability of current. Additionally, it offers a new method for reducing the impact of harmonics on the power grid and improving power quality. It provided an effective method reference for technological progress in related fields such as power electronics and control engineering.

Harmonic oscillation analysis and stabilization method comparison of shunt active power filter in full compensation mode

AbstractThe harmonic compensation of SAPF (shunt active power filter) may trigger harmonic oscillation due to the interaction with grid impedance and non‐linear loads, which distorts the power quality. In previous research, the relevant mechanism has been studied. However, the SAPF generally employs complex harmonic detection algorithm, which significantly increases the computational demands. The SAPF in full compensation mode can effectively solve this problem. But the modification of harmonic detection link may change the oscillation mechanism and previous stabilization methods need to be re‐evaluated. Therefore, this paper establishes the small signal model of the SAPF system in full compensation mode and investigates its oscillation mechanism. It is revealed that harmonic compensation and passive resonance collectively induce the harmonic oscillation. Based on the model, the working mechanism and application performance of the main stabilization methods proposed in the past (harmonic virtual admittance and harmonic compensation canceling) are analyzed and compared. However, neither of them can achieve effective stabilization without sacrificing the performance of compensation. Consequently, the harmonic phase compensation method is proposed to achieve the stabilization of the SAPF system in full compensation mode without affecting normal compensation. Finally, simulations and experiments are performed to verify the mechanism analysis and proposed methods.

Voltage Detection-Based Selective Harmonic Current Compensation Strategies for Photovoltaic Inverters

Voltage and current detection-based harmonic current compensation (VDB-HCC and CDB-HCC, respectively) strategies allow the use of photovoltaic (PV) inverters to enhance the grid power quality. CDB-HCC strategies require converter hardware retrofit by inserting an extra current sensor to measure load or downstream grid currents. On the other hand, VDB-HCC strategies are straightforward solutions employing only embedded measurements used for protection, control, and synchronization purposes. This paper provides a comprehensive comparison of three VDB-HCC strategies: VDB-HCC based on a single current loop (SCL); VDB-HCC based on dual parallel current control loops (DCL); and VDB-HCC based on parallel voltage and current control loops (VCL). The comparison includes the requirement of harmonic detection algorithms, PV array maximum power point tracking (MPPT) performance, stability over grid impedance variations and inverter power rating, steady-state harmonic compensation, enabling transient response, and computational burden. Experimental results using a 1.5-kW commercial PV inverter are conducted. Based on distributed HCC applications by PV systems, VCL has shown the best performance in terms of voltage distortion reduction under weak grids.

Research on Harmonic Detection Algorithm Based on apFFT

With the improvement of train speed of high-speed railway, the traction power and traction current are increasing. In order to evaluate the influence of traction current harmonic and inter-harmonic on train signal system, accurate detection of harmonic and inter-harmonic is urgently needed. This paper proposed an algorithm based on the all-phase fast Fourier transform method (apFFT) to realize accurate detection of harmonic and inter-harmonic. Firstly, the harmonic and inter-harmonic steady-state model are constructed, and the continuous and discrete time characteristics of the signal are analysed. Secondly, on the basis of theoretical analysis, the apFFT method has the characteristics of high amplitude accuracy and phase invariance by comparing with the traditional FFT method. Finally, the detection results of harmonic signal and inter-harmonic signal show that the apFFT method is significantly improved in frequency accuracy, amplitude accuracy and phase accuracy comparing with other FFT algorithms.

NCAFI: Nuttall convolution window all-phase FFT interpolation-based harmonic detection algorithm for infrared imaging detection

Harmonic problems seriously restrict the development of power electronics technology. This condition may provoke multiple results, as follows: (i) reduced efficiency of electric energy production, transmission, and utilization; (ii) overheating; (iii) possible failure of electrical equipment; (iv) confusion in electric energy measuring. In this study, we propose a novel harmonic detection method for the increasingly severe harmonic problem by Nuttall convolution window all-phase FFT interpolation in infrared imaging condition. This method selects a convolution window with four terms of third-order Nuttall and four terms of fifth-order Nuttall, with a lower sidelobe level and faster decay speed. Our method derives the correction formulae for frequency domain and amplitude, using four adjacent spectral lines, combined with the polynomial fitting method. Simulated and real experiments demonstrate that the proposed method achieves a significant improvement in calculation accuracy. Furthermore, our algorithm can better suppress spectral leakage, which is suitable for parameter estimation of low harmonic components. Finally, the feasibility and effectiveness of our algorithm are validated.

Harmonic detection technology based on ant colony optimization BP neural network

At present, ip-iq algorithm based on instantaneous reactive power theory is the most widely used in the field of harmonic detection.However, the ip-iq algorithm based on instantaneous reactive power has coordinate transformation and inverse transformation, which leads to cumbersome calculation.the existence of low-pass filter leads to delay and poor dynamic performance of the algorithm.The harmonic detection based on BP neural network has the advantages of simple calculation, fast detection speed, strong adaptive ability and good dynamic performance.However, the initial weights and thresholds are random, so it is easy for the network to fall into local optimal solution during training, resulting in low detection accuracy. This paper presents a harmonic detection method based on ant colony algorithm optimized BP neural network. ACO-BP, BP and ip-iq algorithms are compared by Simulink simulation. The results show that ACO-BP harmonic detection algorithm is feasible and superior

Analysis of Rotor Position Detection Performance According to the Frequency of Square Waveform Voltage in the Harmonic Injection Sensorless Method through HILS

In this paper, the rotor position estimation performance of the sensorless scheme for permanent magnet synchronous motors (PMSMs) implemented through the injection of high-frequency square-wave voltage according to the frequency of the square-wave voltage is presented through HILS (Hardware In the Loop Simulation) experiments. An inverter using an IGBT device usually has a switching frequency of around 15 kHz. On the other hand, GaN devices that can be switched on and off at frequencies higher than 100 kHz have been recently developed, and research is being actively conducted to apply GaNs to a variable speed system. The purpose of this study is to conduct HILS experiments to analysis the rotor position estimation ability of the sensorless technique in cases where a high switching frequency was applied, such as GaN devices, with that of a system having a usual switching frequency, such as IGBT. In the HILS system used in this study, an inverter and motor model implemented with Simulink are located in a real-time simulator. A sensorless motor control method was implemented with an FPGA control board, which includes a PWM interrupt service routine of 100 kHz frequency and a harmonic injection and position detection algorithm. The HILS experiments show rotor position detection errors according to the various frequency of the harmonic voltage injected for estimating the rotor position with a PWM frequency of 100 kHz cases. According to the experimental results, good position estimation was possible not only when the harmonic of 10 kHz corresponding to 1/10 of the PWM frequency was injected, but also when the harmonic of 1 kHz corresponding to 1/100 of the PWM frequency was injected. The experiments suggest that position estimation errors decrease as the frequency of the harmonic voltage increases, and, based on the foregoing, it is thought that the application of a GaN device capable of realizing a high switching frequency in a variable speed drive system can be another advantage.

Harmonic detection algorithm based on Nuttall double-window all-phase Fast Fourier Transform trispectral interpolation

In harmonic detection of power grid, spectrum leakage of traditional FFT algorithm affects the accuracy of detection results. In this paper, a Nuttall double-window all-phase FFT trispectral interpolation algorithm is proposed. The phase of the spectral line with the maximum amplitude at the sampling point is taken as the initial phase of the signal, and the position of the main harmonic line is determined by using the amplitudes of the three spectral lines near the harmonic peak frequency point. Simulation results show that this algorithm can reduce the error of harmonic parameter detection more effectively and reduce the influence of white noise.

Design of voltage Sag and Harmonic detection algorithm for distribution network dynamic voltage restorer

Design of voltage Sag and Harmonic detection algorithm for distribution network dynamic voltage restorer

A rapid harmonic detection method for grid-connected photovoltaic when three-phase voltage is unbalanced

Abstract By using power electronic devices, photovoltaic grid-connected power generation may inject harmonics into the power system. As the photovoltaic grid-connected inverter has the same basic structure as the active power filter, so the unified control of the photovoltaic grid and active filtering can be achieved. When the current unified control system compensates harmonics of the grid side, it mainly uses ip-iq harmonic detection method, which is based on instantaneous reactive power theory. When the three-phase voltage is unbalanced, the method has a large voltage phase angle detection error and the signal of the low-pass filter tracking system is long, detection time delay and even failure occur. This paper proposes an improved fast harmonic detection method. When phase deviation or amplitude change occurs to the three-phase voltage, the positive and negative-sequence voltages are simultaneously park transformed. The negative-sequence component is filtered by the current average module to obtain the fundamental amount of the voltage, then the phase angle of the positive-sequence voltage is accurately calculated to improve the harmonic current detection accuracy. Through the study of the integral method, it is found that the least common multiple of each harmonic period can be used as the integral interval, and the integral value is also zero, so the detection delay time is reduced by replacing the low-pass filter with an integration module. The simulation results show that the proposed harmonic detection algorithm can accurately detect harmonics when the three-phase voltage is unbalanced, and about 0.057 s improve the harmonic detection speed compared with the commonly used ip-iq method.

Direct prediction compensation strategy of unified power quality conditioner based on FCS–MPC

The finite control set model predictive control (FCS–MPC) has drawn considerable attention in the integrated control of the unified power quality conditioner (UPQC) due to the characteristics of high dynamic response, internal decoupling and multiple constraints. In this study, a new direct prediction compensation strategy (DPCS) based on FCS–MPC is proposed, which eliminates the harmonic detection algorithm, simplifies the UPQC controller structure and reduces the steady-state errors. By compensating for the time delay of FCS–MPC, the UPQC can mitigate the power quality problems more accurately and timely. The FCS–MPC value function can be with various constraints, which makes the UPQC suitable for more situations. Compared with the indirect prediction compensation strategy, the designed DPCS has better time-delay compensation effects, which can reduce the harmonic components of the user-side under transient disturbances. The simulation results show that the proposed compensation strategy can achieve better dynamic and steady-state performance on power quality problems such as voltage sags, swells, interruptions and harmonics.

Research on three-phase four-wire active power filter based on LCLCL coupling structure

In this paper, the main circuit topology of the three-phase four-wire active power filter (APF) and its harmonic current detection and control algorithm are studied. An active power filter system combining LCLCL filter and a three-phase H-bridge structure is proposed. This paper has applied harmonic detection algorithm based on an improved synchronous phase-locked loop (SRF-PLL) and recursive discrete Fourier transform (RDFT) while using triangular carrier modulation control based on PI adjustment to realize the harmonic compensation of the power filter to the grid current. The system has a notch effect on the harmonic at the switching frequency. It can detect the fundamental component and each harmonic component of the load current separately with a small amount of calculation, good real-time performance. Finally, a 5KVA single-phase APF prototype was built to test the superiority of the main circuit topology and the algorithm of current detection and control.

Research on improved harmonic detection method based on instantaneous reactive power theory

In this paper, the problem of the low pass filter is difficult to achieve the response speed and the accuracy balance of the test based on the ip – iq traditional harmonic current detection algorithm based on the instantaneous reactive power theory, and the method of improving the method of the low pass filter based on Sa-function characteristics is proposed. Then, according to the model, the filter is optimized by combining the ratio integral. Finally, the simulation is carried out. The simulation results show that the low pass filter based on the Sa-function characteristics can improve the real-time and accuracy of the harmonic detection.

Multiple Harmonic Current Injection System for Audible Noise Analysis of AC Filter Capacitors in Converter Stations

The audible noise of AC filter capacitors is one of the major noise sources in High Voltage Direct Current (HVDC) converter stations. In order to avoid the sharp noise of AC filter capacitors, it is necessary to design a Multiple Harmonic Current Injection System (MHCIS) for power capacitors to analyze their audible noise characteristics. Simulating effectively the noise of AC filter capacitors under their actual working conditions in converter stations is the primary target of this proposed MHCIS. To ensure the accuracy of the harmonic currents injected into the power capacitors, each harmonic current is detected and controlled separately. On the basis of the instantaneous reactive power theory, a selective harmonic current detection algorithm is proposed in this paper for the single-phase MHCIS. The amplitude of the selected harmonic current can be tracked timely and exactly in d-q synchronous rotational coordinate system, such that a Proportional Integral (PI) controller can be directly operated to eliminate the steady-state errors. The experimental parameters are usually invariable in this system, the phase deviation of the selected harmonic current is also fixed. Thus the phase angle offset of the corresponding harmonic current can be detected and calculated to compensate the system inherent delay. Owing to the accurate detection and control of multiple harmonic currents, the actual working conditions of AC filter capacitors can be accurately simulated, and the reliable noise analysis results of power capacitors can be obtained. Finally, the proposed selective harmonic current detection and control algorithm is verified by the theoretical analysis, simulation and experimental results.

Harmonic Multiple Loop Detection (HMLD) Algorithm for Not-Contact Vital Sign Monitoring Based on Ultra-Wideband (UWB) Radar

In this paper, the harmonic multiple loop detection (HMLD) algorithm for heart rate (HR) and respiration rate (RR) estimation with impulse radio ultrawideband (IR-UWB) radar is introduced. The algorithm includes two parts: one is the harmonic multiple discriminant principle and the other is the cyclic spectrum updating process. The harmonic multiple discriminant principle is used to detect whether the peak point in the fundamental frequency band is the true vital sign signal. The cyclic spectrum updating process can remove the error peak point according to the results obtained from the part one. In this algorithm, threshold setting is not needed and the estimation error caused by the erroneous threshold can be reduced. Only the fundamental and second harmonic frequencies are needed for HR and RR estimation, so the algorithm has strong environmental robustness and low requirement of radar hardwares. Compared with other algorithms, HMLD algorithm provides reasonable average error rates (4.95% and 5.06%) compared to real data from the oximeter in RR and HR detection. The real-time vital signs detection experiment shows that HMLD algorithm can not only detect the vital signs rate and record the historical curve in real time, but also detect the location information, which proves the validity of HMLD algorithm in real-time vital signs detection.

Improved Ip-Iq Harmonic Detection Algorithm Based on Mixed Second-and Third-Order Generalized Integrator

Aiming at the influence of DC component and high-order harmonics on harmonic current detection accuracy, an improved ip-iq harmonic detection algorithm based on mixed second-and third-order generalized integrator is proposed in this paper. The MSTOGI filter is added to the traditional ip-iq structure, which effectively filters the DC component of the input signal and suppresses the high-order harmonics. The phase-locked loop of MSTOGI can provide a stable grid voltage frequency when the grid voltage contains high-order harmonics and DC components, so that the harmonic current can be detected more accurately. The traditional ip-iq method and the general SOGI-based ip-iq method are compared and analyzed by simulation examples, which verifies the effectiveness and reliability of the proposed harmonic detection method when the power grid contains DC component and high-order harmonic.

A Novel Strategy Based on Linear Active Disturbance Rejection Control for Harmonic Detection and Compensation in Low Voltage AC Microgrid

In an AC microgrid, harmonic distortion is mainly caused by power electronic equipment and nonlinear loads. In this paper, linear active disturbance rejection control (LADRC) is used to control the fundamental current at the point of common coupling (PCC). Meanwhile, an active power filter (APF) is added to eliminate the harmonic current generated by the nonlinear loads. The tracking differentiator (TD) in active disturbance rejection control (ADRC) serves as a low-pass filter (LPF) in the harmonic detection algorithm of APF. Compared to traditional harmonic detection algorithms, the improved strategy solves the contradiction between rapidity, accuracy, and overshoot of filtering. LADRC has good performance of disturbance rejection, internal decoupling, and accessible parameters tuning. It can observe the internal uncertainty and external disturbance of the system as the total disturbance through the extended state observer (ESO), and compensate it in time through state feedback to make the system achieve the desired performance. The abilities of resonance suppression for LCL-type filter and internal decoupling of LADRC demonstrates its advantages through frequency domain analysis and simulation. The proposed strategy was simulated in MATLAB/SIMULINK and realized in the experimental hardware platform, and the effectiveness of the proposed strategy is approved.

Research on APF Improved Control Strategy Under Three-phase Voltage Distortion

At present, the most commonly used harmonic current detection algorithms are the p-q algorithm and the ip-iq algorithm based on the instantaneous reactive power theory. The premise of using the above algorithms is that the three-phase voltage is the ideal sinusoidal voltage. However, harmonic pollution distorts the voltage of the power grid to different degrees, which will affect the detection accuracy and compensation effect of APF. This paper presents a current detection algorithm based on positive sequence fundamental wave extractor, which can avoid the detection of positive sequence fundamental wave voltage of power grid, and can effectively avoid the shortcomings of p-q algorithm and ip-iq algorithm without using PLL, complex coordinate transformation and low-pass filter. In the current control algorithm, according to the characteristic that the gain of the generalized integrator is infinite when resonance occurs, the sinusoidal and cosine instructions can be tracked without static difference, this paper which is based on the generalized integrator adaptively adjusts the coefficients of the generalized integrator to improve the robustness of the current controller. Finally, the simulation model is established by MATLAB, and the simulation results show that the improved harmonic current detection algorithm and control algorithm are advanced and effective.

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.

Research on Harmonic Analysis and Detection Based on Improved Wavelet Packet Inverter

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.