Harmonic Suppression Capability Research Articles

Evaluation of Interval Type-2 Fuzzy Neural Super-Twisting Control Applied to Single-Phase Active Power Filters

This research introduces an improved control strategy for an active power filter (APF) system. It utilizes an adaptive super-twisting sliding mode control (STSMC) scheme. The proposed approach integrates an interval type-2 fuzzy neural network with a self-feedback recursive structure (IT2FNN-SFR) to enhance the overall performance of the APF system. The IT2FNN with STSMC proposed here consists of two components, with one being IT2FNN-SFR, which demonstrates robustness for uncertain systems and the ability to utilize historical information. The IT2FNN-SFR estimator is used to approximate the unknown nonlinear function within the APF. Simultaneously, the STSMC component is integrated to reduce system chattering, improving control precision and overall system performance. STSMC combines the robustness and simplicity of traditional sliding mode control, effectively addressing the chattering problem. To mitigate inaccuracies and complexities associated with manual parameter setting, an adaptive law of sliding mode gain is formulated to achieve optimal gain solutions. This adaptive law is designed within the STSMC framework, facilitating parameter optimization. Experimental validation is conducted to verify the harmonic suppression capability of the control strategy. The THD corresponding to the designed control algorithm is 4.16%, which is improved by 1.24% and 0.55% compared to ASMC and STSMC, respectively, which is below the international standard requirement of 5%. Similarly, the designed controller also demonstrates advantages in dynamic performance: when the load decreases, it is 4.72%, outperforming ASMC and STSMC by 1.15% and 0.38%, respectively; when the load increases, it is 3.87%, surpassing ASMC and STSMC by 1.07% and 0.36%, respectively.

Substrate Integrated Waveguide-Based Full-Duplex Antenna With Improved Out-of-Band Suppression

This brief presents a self-diplexing antenna with harmonic-suppression capability. The suggested antenna operates at 7.8 and 9 GHz and maintains a harmonic suppression of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.17f_{1}$ </tex-math></inline-formula> (where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{1}$ </tex-math></inline-formula> is the lower resonant frequency.) The isolation between two ports is more than 22 dB. The substrate-integrated waveguide (SIW) is used in the construction of the cavity-backed planar duplexing antenna. Starting from a microstrip patch antenna with undesirable high-frequency harmonics, a series of vias are used to suppress those harmonics. Finally, a slot (rotated over 45°) is used to bring the higher order mode to lower frequencies. Moreover, the size reduction in this design is achieved using capacitive slots. Consequently, the proposed antenna suppresses the second, third and fourth harmonics by using two pairs of slots and shorting pins. Besides having a low-profile and offering harmonic suppression, it provides independent frequency tuning in the operating frequency bands by means of capacitive slots. The proposed antenna is built and tested, displaying a reasonable match between the simulation and measurement performances, in this way validating the suggested concept.

Improved Configuration Proposal for Axial Reluctance Resolver Using 3-D Magnetic Equivalent Circuit Model and Winding Function Approach

Resolver is a position sensor that is widely employed in motor servo systems under harsh working conditions. In this article, a novel axial flux resolver with a fractional-slot sinusoidal distributed winding configuration is developed, which has the advantages of a simple structure and convenient mass production. Sinusoidal distribution winding expands the optional range of pole–slot combinations, and its harmonic suppression capability is proposed and verified by the winding function approach (WFA). Furthermore, the magnetic equivalent circuit (MEC) model is formulated to analyze the impact of structural parameters on the induced voltage envelope, through which the optimal parameters on the resolver are developed. In terms of computation time and accuracy, the results of the MEC model under healthy and eccentric conditions are compared with the finite-element method (FEM). In addition, the antiaxial offset capability of the half-wave resolver is illustrated and verified. The effectiveness and superiority of the proposed resolver are illustrated and verified based on numerical simulations and experimental tests.

A Control Strategy of LCL-Type Grid-Connected Inverters for Improving the Stability and Harmonic Suppression Capability

The conventional inverter-side current single-loop feedback control scheme is weak in suppressing the grid-side current harmonics, posing a challenge for an inverter to inject high-quality current under distorted grid voltage. With capacitor current compensation added, the control scheme achieves controllability of the grid-side current harmonics so that it can effectively suppress some specific harmonic components. However, due to the stability requirements, only a few low-order harmonic resonance controllers can be applied, which limits the mitigation of high-order harmonics. To tackle this problem, the grid-side current feedback control with inductor–capacitor–inductor (LCL) resonance damping is proposed in this paper. In this case, a higher LCL resonance frequency can be set compared to the inverter-side current single-loop feedback control scheme. Thereby, more resonance controllers can be applied to suppress high-order grid-side current harmonics. The active damping method of capacitor current proportional feedback plus capacitor voltage proportional feedback is adopted because of its high robustness to grid impedance variations. Furthermore, this paper reveals that the applied active damping method has a limitation in that it only considers a single inverter under inductive grid impedance, which cannot eliminate the risk of resonance caused by the interaction of multiple inverters and the grid. To address this issue, a phase lead compensator (PLC) is proposed, eliminating the resonance risk by removing the non-passive region of the inverter output admittance. To retain the advantage of the inverter-side current single-loop feedback control scheme, i.e., only a few measuring devices are required, a digital differentiator is used to calculate the capacitor current from the capacitor voltage. The difference between the measured inverter-side current and the calculated capacitor current is taken to approximate the grid-side current for the feedback control. The control performance is comparable to using the grid-side current for feedback. Simulation and experimental results demonstrate that the proposed control scheme endows the inverter with good stability and current quality without extra measurement devices.

Photonic microwave frequency divider with a tunable division ratio and harmonic suppression capability

A photonic microwave frequency divider that is capable to realise tunable high order frequency division, is presented. It is based on injecting an RF phase modulated optical signal into an off-the-shelf DFB laser operating at period-N state. Optical frequency components with a frequency separation of 1/N times the input RF signal frequency are generated by the DFB laser. An optical bandpass filter can be employed to select two optical frequency components to be detected by a photodetector to obtain a divide-by-N RF signal without harmonic components. The proposed frequency divider can be operated over a wide frequency range and has high reconfigurability as it is free of electrical components. Experimental results demonstrate the realisation of frequency division operation with a tunable 1/2 to 1/5 division ratio for different input RF signal frequencies of 8 to 20 GHz by adjusting the DFB laser forward bias current. Over 35 dB harmonic component suppression is demonstrated. A proof-of-concept experiment is also set up to show the frequency divider based on an optically injected semiconductor laser is capable to operate at a high input RF signal frequency of 50 GHz and has a tunable high order division ratio of 1/2 to 1/8.

A Novel Control Strategy in Grid-Integrated Photovoltaic System for Power Quality Enhancement

The integration of solar photovoltaic (PV) systems and utility grids has gradually gained significant interest in improving the sustainability of clean power supply for society. However, power quality remains a challenge due to partial shading conditions and harmonics. To overcome these drawbacks, a flexible radial movement optimization based on a dynamic safety perimeter maximum power point tracking algorithm is employed to track maximum power out of a PV system and to ensure that the optimum voltage level at the common DC bus is obtained under partial shading conditions using fixed-tilt installation configuration. Furthermore, a novel inverter control loop system with a double second order generalized integrator phase-locked loop (DSOGI-PLL) is also proposed to mitigate harmonics and improve the power quality of the grid interfacing PV system using MATLAB SIMULINK software. The proposed system has several merits, such as better harmonic suppression capability, control adaptivity, rapid tracking speed, low computational burden and phase and grid synchronization.

Wideband Photonic Microwave Frequency Divider With Large Harmonic Suppression Capability

An all-optical photonic microwave frequency divider (PMFD) is presented. It is based on injecting an RF phase modulated optical signal into a semiconductor laser oscillating in the period-two state. New optical frequency components with frequency separation of half of the input RF signal frequency are generated at the laser output. A frequency divided signal can be obtained by the beating of these optical frequency components at a photodetector. Large harmonic suppression can be achieved by using an optical filter to select only two optical frequency components to be detected by the photodetector. The proposed PMFD is free of electrical components and does not suffer from the modulator bias drift problem. It has the potential to operate over a 100 GHz frequency range. System parameters required to realise divide-by-two frequency division operation for different input RF signal frequencies are investigated. Experimental results are presented for the novel PMFD, which demonstrate the generation of a 1/2 frequency component for different input RF signal frequencies by controlling the forward bias current of an off-the-shelf semiconductor laser, and which also show the important advantages of large harmonic suppression and high signal-to-noise ratio performance. Wide input RF signal power range and high output stability performance are also demonstrated experimentally.

Single Current Feedback Control Strategy of an LCL Grid-Connected Inverter Based on GI-ESO and Delay Compensation

This paper presents a new control structure to improve the performance of LCL grid-connected inverters. First, the conventional linear extended state observer (LESO) has difficulty rejecting periodic disturbances, so the proposed method adds an internal model of disturbances into LESO to enhance the harmonic suppression ability. Second, the phase lag caused by the digital delay and LCL resonance make it difficult to ensure the stability of the system. In this paper, the proposed method adds phase compensation for the ESO loop, thus enlarging the stability region of the system with no additional sensors being required. Third, the design of the controller parameters is simplified and the frequency performance analysis of the system is given. Finally, the simulation and experimental results show that the proposed method has good harmonic suppression capability and robust stability.

A high performance grid synchronization method for renewable energy grid-connected applications

Aiming at the problem of insufficient harmonic suppression capability for distributed renewable energy grid-connected application equipments, an efficient grid synchronous phase-locked loop(PLL) which will suppress harmonics is proposed. Firstly, a novel high-order generalized integral (NHOGI) is presented in traditional αβ-frame, and the dual novel high-order generalized integral (DNHOGI) structure is presented. Secondly, to remove interference of harmonic on PLL, a moving average filter(MAF) is added to eliminate the multi-order harmonic components and improve the phase-locked accuracy. Finally, DNHOGI and MAF filters are combined into a cascade filter, and a phase-locked loop used the cascade filter is proposed. The feasibility of the new approach is tested by experimental comparison with traditional methods.

A Spurious Free Dual Band Microstrip Patch Antenna for Radio Frequency Energy Harvesting

Objectives: To design high gain square slots loaded dual-band rectangular microstrip patch antenna having harmonic suppression capability and rectifier circuit (Rectenna (Antenna + Rectifier) for Radio Frequency Energy Harvesting (RFEH). Methods: To achieve the objectives, the square slots are loaded on the four corners of the rectangular microstrip patch in order to enhance the current distribution which resulted in improved impedance matching at desired frequencies with dual isolated bands. The proposed antenna is simulated in Computer Simulation Technology (CST) Studio Suite Three- Dimensional Electromagnetic Simulation (3DEM) software. A rectifier with an LC impedance matching network is designed, simulated, and optimized in Agilent Advanced Design System (ADS) software. Findings: The overall size of the proposed antenna operating at 2.49 GHz and 3.73 GHz (WiMax) is 57482.5 mm3. The proposed antenna is assessed in terms of its simulated performance parameters: Return loss (S1,1), Impedance (Z1,1), Voltage Standing Wave Ratio (VSWR), Gain, Directivity, and Efficiency. The proposed antenna exhibits improved performance over the conventional rectangular patch antenna, in terms of (S1,1), Impedance (Z1,1) and Gain. The results obtained from the simulation indicate -35.47 dB and -37.42 dB of S1,1 at 2.49 GHz and 3.73 GHz respectively with the Gain of 4.74 dBi and 3.62 dBi respectively. Further, a rectifier circuit is proposed at 2.45 GHz. The complete rectenna system is simulated over a range of input power levels (1dBm-10dBm) for 4.7 kOhm load resistance. The simulated rectenna result presents the maximum output voltage of 3.34 V. Novelty and Applications: The proposed rectenna design with its harmonic suppression capability can be used for RFEH to drive the Internet of Things-Sensor Network (IoT-SN) and Wireless Sensor Network (WSN). The novelty of the proposed work is harmonic suppression capability. harmonic suppression capability is achieved by inserting the square slots at the four corners of the conventional square patch. Keywords: Radio Frequency; Energy Harvesting; Efficiency; Gain; Rectifier; Schottky diode

Design of a Patch Power Divider With Simple Structure and Ultra-Broadband Harmonics Suppression

This paper introduces a simple H-shaped patch Wilkinson power divider (WPD), which provides ultra wide harmonics suppression band. The presented WPD designed at 1.8 GHz, and exhibits good performance at the operating bandwidth. In the proposed divider structure, two simple patch low-pass filters (LPFs) are employed at each branch, and three open ended stubs are added at each port. The proposed divider, implemented using the aforementioned structures has a good performance at both higher frequencies, and the operating frequency. In particular, the designed divider provides an ultra wide suppression band from 3 GHz to 20 GHz, which encompasses the 2nd up to the 11th harmonic. The proposed WPD has an operating band from 1.62 GHz to 2.1 GHz, with the operating bandwidth exceeding 480 MHz. Consequently, the fractional bandwidth (FBW) of 25.8 percent is obtained. The results indicate |S11|, |S12|, |S22|, and |S23|, are equal to –17 dB, –3.5 dB, –20 dB, and –17 dB, respectively, at the operating frequency. The simulation results are corroborated through the measurements of the fabricated divider prototype. The superior harmonic suppression capability is also demonstrated through comparisons with state-of-the-art divider circuits from the literature.

Ultrawideband Harmonic Suppression in Microstrip Patch Antenna Using Novel Defected Ground Structures

Suppressing higher-order modes up to sixth harmonics of the fundamental working frequency in a single-layer microstrip line-fed patch antenna has been successfully demonstrated. Higher-order modes of the antenna are suppressed by simultaneously employing a circular head open stub connected to the feed line and a novel defected ground structure (DGS) beneath the feed line. The filtering property of the antenna has been improved by the novel DGS significantly. The role played by the novel DGS is carefully analyzed, and the effect of some key parameters of DGS is further discussed. A microstrip patch antenna with the working frequency 3.13 GHz (fc) is designed and manufactured. The designed antenna possesses an ultrawideband harmonic suppression capability ranging from 2fc to 6fc. More importantly, the area occupied by the novel DGS is decreased by 41% compared to the earlier design.

Wearable dual-band antenna with harmonic suppression for application in medical communication systems

In this paper, a wearable dual-band antenna (WDBA) with harmonic suppression capability is presented for application in wireless medical/communication systems such as industrials, scientific, and medical (ISM) bands (0.9–1 GHz and 2.4–2.48 GHz). For harmonic suppression, 3 pairs of shorted-pins resonators (SPRs) are employed. These resonators, in addition to eliminating unwanted harmonics, also cause the antenna frequency response dual-band. The final dimensions of the proposed antenna are 60 × 60 × 2 mm3 or 0.19 × 0.19 × 0.006 λg3 at 950 MHz. The maximum simulated gain at 1 GHz and 2.4 GHz are equal to 2.23 dB and 2.38 dB, respectively. Finally, to prove the simulations, the proposed WDBA was fabricated and its parameters were measured. The results of the measurement are in good proportion to the results of the simulations.

Leakage Current Suppression in Double Stage SECS Enabling Harmonics Suppression Capabilities

This work deals with a harmonic control strategy for a transformerless double stage solar energy conversion system (SECS) to alleviate the leakage current in the presence of nonlinear loads enabling harmonics suppression capability. In this SECS, the PV module stray capacitance can elicit leakage current, which causes electromagnetic interferences and potential safety problems. To address these issues, the model predictive controller based adaptive harmonic compensation strategy is presented herein, which not only provides leakage current suppression but it also serves manifold ancillary power quality improvement features. The revised IEEE-519-2014 standard is incorporated in adaptive harmonic compensation strategy to achieve harmonics within recommended limits. The comparative response with a conventional control is exhibited to verify the capabilities of harmonic control strategy. Furthermore, a comparative harmonic suppression capability is analyzed herein to validate the competence of voltage controller. Various real-time simulated results are discussed to manifest capabilities of this control. The leakage current is restricted below 300 mA as per desirable safety requirements against leakage current of VDE-00126-01 and IEC-62109-2 standards. The total harmonic distortion (THD) of grid current and voltage, are achieved within permissible limits in compliance with the revised IEEE-519-2014 code.

Low harmonic 12-pulse rectifier with a circulating current shaping circuit

This paper proposes a four-star 12-pulse diode rectifier with a circulating current shaping circuit CCSC on the DC side to decrease the input current harmonics effectively. The type of circulating current that can eliminate the input current harmonics is analysed and its waveform parameters are derived. The effects of triangular circulating current on the harmonics of the input current are analysed, and the harmonic suppression mechanism of the triangular circulating current is revealed. This scheme has excellent harmonic suppression capability, and the capacity of CCSC is only 2.35% of output power of the 12-pulse rectifier. Thus, this scheme is cost effective for high power applications. The experimental results confirm the theoretical analysis and near sinusoidal input current is obtained.

Self-Oscillating Circularly Polarized Active Integrated Monopole Antenna Using Cross-Coupled Pair and Inverted-L Strip

A self-oscillating active integrated antenna (AIA) featuring circular polarization (CP) is presented in this letter. The oscillation is sourced by a cross-coupled pair (XCP) with negative conductance. Microstrip lines with embedded LC resonators are applied to fulfill the feedback loop between the pair of transistors, which functions as the frequency selective element with harmonic suppression capability. A monopole antenna is attached to the output of the XCP for radiating the oscillation power into space; the CP operation, meanwhile, is obtained by introducing a perturbation using an inverted-L strip protruding from the ground plane. A left-handed circularly polarized AIA (CPAIA) was designed at 916 MHz as a potential far-field wireless power charging source in the ultrahigh-frequency ISM (industrial, scientific, medical) band. The experimental validation reveals that, when compared with existing CPAIA designs, the proposed work consumes much less dc power but still keeps acceptable radiation parameters; it also features the smallest size and highest dc-to-RF conversion efficiency. The lowpower consumption makes the direct integration with a small-size solar panel become feasible.

A Luenberger observer-based phase locked loop for single-phase systems under harmonic disturbances

Harmonics in single-phase systems challenge the performance of quadrature signal generator-based phase-locked loops (QSG-PLLs). This paper proposes a Luenberger observer-based PLL (LO-PLL) to address the issue. The proposed method enhances the harmonic suppression capability when estimating the fundamental grid voltage, thus leading to improved system harmonic rejection robustness. In detail, the improvement is enabled by the integrated grid voltage, which is mathematically established in this paper. Subsequently, the observer is adopted to generate the fundamental grid voltage and its quadrature signal. The resultant two signals for synchronization are highly robust against arbitrary-order harmonic disturbances, especially for interharmonics and noises. More importantly, as the poles of the observer can be designed flexibly, fast dynamics and strong harmonic robustness can be ensure for the entire PLL system. Experiments verify the performance of the proposed LO-PLL in terms of high harmonic immunity and fast dynamics.

A Robust Frequency Estimation Method for Aircraft Grids Under Distorted Conditions

In aircraft grids, the voltage frequency is much higher than that in utility power systems and it challenges the dynamics of frequency estimations. In this letter, a fast and robust frequency estimation method is proposed for aircraft grids even when the grid voltage is distorted. In detail, a mathematical model is established based on the relationship among the fundamental grid voltage, harmonics and their time-delay signals. Accordingly, a robust parameter identification method is proposed to achieve grid frequency estimation and harmonic immunity. Compared with the frequency estimations for utility power systems, the proposed method, so-called robust frequency estimation (RFE), has faster dynamics and stronger harmonic suppression capability. Hence, it takes advantages in the applications of aircraft grids. Experimental results also indicate that the proposed RFE has good performance in terms of fast dynamics and strong robustness.

New parameter tuning method for LCC/LCC compensated IPT system with constant voltage output based on LC resonance principles

Compensation topologies with constant current (CC) or constant voltage (CV) play essential roles in inductive power transfer (IPT) systems. This article describes basic LC resonance principles, which can analyse the output characteristics of all the compensation topologies with CC or CV outputs. By combining LC principles, a new parameter tuning method for LCC/LCC topology with CV output is proposed, followed by efficiency analysis and sensitivity analysis as per various configurations. Moreover, comparing with conventional topologies, it indicates that the LCC/LCC topology has three advantages: (i) The output voltage is load-independent, and it can easily achieve zero phase angle (ZPA) or zero voltage switching (ZVS); (ii) This topology can free the design from the restrictions enforced by the loosely coupled transformer parameters; (iii) The topology is equipped with high-order harmonic suppression capability. Finally, a 1300-W laboratory-scale prototype with a 15 cm air gap was built to verify the theoretical analysis. The experimental results demonstrate the feasibility and superiority of the proposed LCC/LCC IPT system with new parameter tuning method.

Low DC voltage PV generation system with power factor correction and harmonic suppression capability in a distribution network

Building-integrated photovoltaics (PVs) is one of the most promising and elegant ways of producing on-site electricity. The compact and cost-effective PV integration system needs to be developed to convert dc voltage into ac compatible with the grid. A single-stage PV inverter is proposed, and its design and control system implementation are focused on. The proposed system is able to transfer active power to the grid with maximum power point tracking. At the same time, the PV inverter can control reactive power and suppress harmonics due to non-linear loads. By coupling to grid via a series LC branch, the proposed system operates on a dc bus voltage much lower than that of the conventional PV inverter, so that less PV panels need to be connected in series. Therefore, the proposed system is a low-cost and multi-functional alternative to PV inverters in building-integrated applications. Simulation and experimental results are provided to validate its effectiveness.