Harmonic Impedance Research Articles

Design of High-Efficiency Broadband Rectifier With Harmonic Control for Wireless Power Transfer and Energy Harvesting

In this letter, a novel methodology for designing a broadband rectifier with high efficiency and an extended dynamic range of input power is proposed for wireless power transfer (WPT) and energy harvesting (EH). The proposed structure consists of two main networks. The first one reduces diode impedance variation with only two transmission lines (TLINs). The second network deploys a synthesized three-stage, low-pass matching network (MN) to match the reduced-variation fundamental impedance to the source of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\Omega $ </tex-math></inline-formula> . The harmonic impedances in the stopband of this low-pass MN is manipulated to reshape the diode-across current and voltage following the Class-C or Class-R standard waveforms for power conversion efficiency (PCE) enhancement. For validation, a HSMS2860-based rectifier prototype is tested showing a bandwidth of 43.5% from 1.8 to 2.8 GHz with 72%-above PCE at an input power of 14 dBm. In addition, the PCE of over 70% is achieved across a bandwidth of 48.9% (1.7–2.8 GHz) with the highest of 82.5% at 12 dBm while the measured PCE can remain above 47% within the same bandwidth at a low input power of 0 dBm. Furthermore, the proposed rectifier has a comparative size of 46 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times32$ </tex-math></inline-formula> mm.

Improved Sparse Component Analysis for Multi-Point Harmonic Contribution Evaluation Under Incomplete Measurements

The existing methods for multi-point harmonic contribution evaluation usually require some preconditions, such as the node harmonic current is equivalent to the harmonic emission current and the number of measurements is not less than the number of sources. However, these requirements may not be satisfied in practice. In this context, this paper proposes an improved sparse component analysis (SCA) method to solve the underdetermined blind source separation model, which is used to describe the harmonic state under incomplete measurements. The improved SCA adopts a new two-stage technique. First, the mixing matrix containing harmonic transfer impedances is estimated through the synchrosqueezing S-transform. Then, the source signal vector containing harmonic emission currents is reconstructed through the modified subspace projection. By matching the harmonic impedances and currents, the multi-point harmonic contribution evaluation is further achieved. The efficiency of the proposed method is verified by simulations and field case studies. The results demonstrate that the proposed method outperforms the existing methods in terms of accurately estimating the harmonic emission currents and quantifying the harmonic contributions under incomplete measurements.

Harmonic resonance analysis in high‐renewable‐energy‐penetrated power systems considering frequency coupling

AbstractRenewable energy is a key solution to address the challenges of energy shortages and climate change. Consequently, high‐renewable‐energy‐penetrated power systems (HREPPS) have become a popular trend. This has led to the increasing use of voltage‐source converters (VSCs) as renewable‐energy interfaces. Meanwhile, other VSC‐based applications such as flexible alternating current transmission systems (FACTS) are used for supporting the energy conversion of renewable energy. With the large integration of VSC‐interfaced devices, there is a rising concern regarding their impact on the harmonic resonance of power systems. In this study, a new harmonically coupled impedance model is proposed to inspect the harmonic resonance caused by VSC‐interfaced devices in HREPPS. The model is derived based on the penetration of a multifrequency harmonic, enabling it to fully reveal the frequency coupling effect in the system. Research has shown that frequency coupling plays an important role in harmonic resonance analysis. The correctness of the proposed harmonic impedance model and its effectiveness on harmonic resonance analysis were verified using time‐domain simulations of a real‐life photovoltaic integrated system.

Study on Harmonic Impedance Estimation Based on Gaussian Mixture Regression Using Railway Power Supply Loads

There are a huge number of harmonics in the railway power supply system. Accurately estimating the harmonic impedance of the system is the key to evaluating the harmonic emission level of the power supply system. A harmonic impedance estimation method is proposed in this paper, which takes the Gaussian mixture regression (GMR) as the main idea, and is dedicated to calculating the harmonic impedance when the load changes or the background harmonic changes in the traction power supply system. First, the harmonic voltages and currents are measured at the point of common coupling (PCC); secondly, a Gaussian mixture model (GMM) is established and optimized parameters are obtained through the EM algorithm; finally, a Gaussian mixture regression is performed to obtain the utility side harmonic impedance. In the simulation study, different harmonic impedance estimation models with uniform distribution and Gaussian distribution are established, respectively, and the harmonic impedance changes caused by different system structures in the railway power supply system are simulated. At the same time, the error is compared with the existing method to judge the accuracy and robustness of this method. In the case analysis, the average value, average error, standard deviation and other indicators are used to evaluate this method. Among them, the average error and standard deviation of this method are about one-fifth to one-third of those of the binary linear regression (BLR) method and the independent random vector (IRV) method. At the same time, its index is slightly better than that of the support vector machine (SVM) method.

Propagation Characteristics and Identification of High-Order Harmonics of a Traction Power Supply System

High-order harmonics in the traction power supply show negative effects on the safe and stable operation of the railway transportation system. There is a fixed resonant frequency in the traction network. When the harmonic current frequency produced by the locomotive matches the resonant frequency of the traction network, it will cause high-frequency resonant overvoltage. The propagation path of the high-order harmonics of the traction load is analyzed based on a V/v wiring traction transformer. The propagation characteristics of high-order harmonics on self-used equipment at 380 V low-voltage side and 27.5 kV high-voltage side are expounded. A simulation model for the low-voltage self-consumption power system is established and the singular value decomposition algorithm is proposed to identify the harmonic impedance. The simulation results show that the proposed method can reduce the error to within 0.1%. Under realistic conditions, the overvoltage caused by high-order harmonics is difficult to identify. To solve this problem, an overvoltage identification algorithm for Electric Multiple Units based on a convolutional neural network is proposed. The ShuffleNet neural network model is then used to identify high-order harmonics overvoltage and other types of overvoltage. The overall accuracy of the proposed classification model can be improved from 97.12% to 98.44%. Better recognition and classification performances can also be achieved.

A Class-X Power Amplifier With Finite Number of Harmonics

This article extends the theory of Class-X power amplifiers (PAs) with maximally flat waveforms by considering an arbitrary number of harmonics in the analysis. The proposed theory shows that the maximally flat voltage and current waveforms can be established with a proper fundamental load corresponding to a set of randomly and independently distributed purely reactive harmonic load impedances. It also shows that the efficiency increases with the number of harmonics regardless of the values of the harmonics. The proposed theory of Class-X PA allows for the design of a high-efficiency PA considering the effects of high-order harmonics in the presence of significant parasitic effects. To demonstrate this ability, a 3.5-GHz Class-X PA considering the effects of nine harmonics is designed and fabricated with a packaged 10-W device. The simulated and measured results show a drain efficiency of 84% for an output power of 40.5 dBm.

An Improved Model of Voltage Source Converters for Power System Harmonic Studies

Voltage source converters (VSCs) have been extensively used in power systems for interfacing renewable energies and other modern loads. Because of their nonlinear nature, a proper harmonic model of VSC devices must be established when conducting harmonic analyses in power systems. This is especially true for low-order harmonics, which are routinely encountered in present power systems. To this end, an analytical harmonic model that represents the low-order harmonic characteristics of VSCs is developed in this paper. The new model takes both the control loop and power loop (i.e., DC-link capacitor) of the VSC into account through rigorous mathematical derivations. The final result has shown that the VSC can be represented by a harmonically coupled impedance matrix at harmonic frequencies, which can be easily used for harmonic analyses of large-scale power systems. It also shows that the DC-link capacitor has a more noticeable impact on the harmonic impedance of VSCs with a smaller DC-link capacitance and low-order harmonics. The appropriateness of the new model was verified using EMT simulations and lab experiments. A complete procedure to construct the proposed VSC model is also established based on the research findings.

A new design for mode transfer-based harmonic tuned power amplifier (MHPA)

Available onlineThis paper presents the design, implementation and measurement results for a 0.8–2.1 GHz Mode transfer-based Harmonic tuned Power Amplifier (MHPA). The design based on a new combination of the hybrid modes. The proposed design approach uses the mode transfer technique to combine two harmonic tuned power amplifier modes, i.e., classes F3 and F3-1, in order to obtain a broadband hybrid mode PA. First, theoretical limitations of maximum attainable Fractional Bandwidth (FBW) in a single mode harmonic tuned PA (HTPA) are investigated where we have n harmonic impedances and there is no overlapping between harmonics. Then, mode transfer technique is applied to overcome bandwidth restriction of F3 and F3-1 modes of HTPA. As a result, the maximum FBW in a single mode HTPA with 3 harmonic impedances is improved from 40 % to 66 % (equivalent to one octave) when it being used in a hybrid structure. To evaluate the proposed design approach, a broadband PA, which is working at one octave bandwidth (1–2 GHz), is designed and fabricated. Performance of the designed MHPA is acceptable at the 0.8–2.1 GHz frequency band. Experimental results show that the designed MHPA achieves 89.9 % maximum and 76.3 % average drain efficiency in the 0.8–2.1 GHz frequency band.

Mechanism analysis and suppression method of high frequency harmonic resonance in VSC-HVDC

This paper introduces the basic situation of high frequency harmonic resonance in Guangxi on April 10, 2017, which is based on the Luxi back-to-back voltage source converter based high voltage direct current transmission (VSC-HVDC) project in China. Firstly, the harmonic amplification mechanism and its key links in the event are analyzed in detail and verified by simulation. Secondly, the relationship among high frequency harmonic resonance, voltage feedforward control loop and system harmonic impedance is obtained, and the formulas among voltage feedforward control parameters, system harmonic impedance and high frequency harmonic resonance frequency amplitude are deduced. Then, a method to suppress high frequency harmonic resonance by adding a reasonably filter to the voltage feedforward control loop is proposed. Finally, the effectiveness of the proposed method in this paper is verified by simulation and field operation.

Wideband high‐efficiency extended continuous Class F power amplifier using a new wideband bandstop network

In this letter, we propose a novel methodology for designing high-efficiency broadband harmonic-controlled power amplifiers (PAs) using a new wideband bandstop network. This network consists of many parallel open circuit microstrip lines, each corresponding to a quarter of wavelength for different frequencies. This topology can improve efficiency and bandwidth by controlling harmonic match impedance. The harmonic and the fundamental matching networks can be designed simultaneously to reduce the mutual effect between them. We also design and fabricate a highly efficient PA with more than an octave bandwidth to verify the validity of the proposed network structure. The measured results show that the fractional bandwidth is 82.9% from 1.2 to 2.9 GHz. The drain efficiency that can be achieved is 86.06% and the maximum output power is 42.97 dBm when the input power is 30 dBm between 1.2 and 2.9 GHz.

Impedance-Based Adaptively Reshaping Method for Enhancing Nonlinear Load Sharing and Voltage Quality in Islanded Microgrids With Virtual Synchronous Generator

For the distributed generation units (DGs) using virtual synchronous generator (VSG) control algorithm connected to the islanded microgrid with high penetration of nonlinear load, there is always a trade-off between harmonics sharing accuracy and voltage quality when using conventional harmonics sharing methods. To address this issue, an impedance-based adaptively reshaping method is proposed in this paper, which is based on harmonic current feedforward compensation control and impedance reshaping factor adaptive control, assigning a variable harmonic impedance reshaping factor for each VSG to improve the controllability of VSG harmonic impedance, thus simultaneously enhancing nonlinear load sharing and voltage quality. Moreover, a droop-based methodology for impedance reshaping factor tuning is presented to adaptively reshape harmonic impedance for each VSG without acquiring the line parameters in advance. The proposed method also enjoys the advantage of avoiding introducing additional virtual harmonic impedance, and thus it is immune from the inverter closed-loop gain throughout the dominant harmonic frequencies. Furthermore, the stability analysis and the key control parameter design are discussed in detail. Finally, the effectiveness of the proposed method is verified by simulation and experimental results.

A fully integrated GaAs HBT power amplifier with enhanced efficiency for 5-GHz WLAN applications

An efficiency-enhanced fully integrated power amplifier (PA) for wireless local area networks (WLANs) was implemented based on the GaAs heterojunction bipolar transistor (HBT) process. A harmonic tuning network that can absorb the parasitic inductance of the bonding wires is proposed, which reduces the chip area significantly. The network provides nearly optimum fundamental and second harmonic impedances from 5.0 to 5.5 GHz. Additionally, a novel adaptive bias circuit that corrects the AM-AM and AM-PM distortion and improve thermal stability at high input power was proposed. With a chip dimension of only 1.06 mm2, the PA achieves a gain of 31.1-31.6 dB and saturated power of 29.9-30.3 dBm with a peak power-added efficiency (PAE) of 49.3%-51.8% across 5.0-5.5 GHz. The PA also shows an output power of 22.1 dBm (EVM=-32 dB) with 18.4% PAE under an 802.11ac MCS9 VHT160 test signal. In addition, the PA delivers 17.5 dBm (EVM=-42 dB) output power when tested with the 802.11ax MCS11 VHT160 signal at 5.25 GHz.

Transient overvoltage analysis in the medium voltage substations based on full-wave modeling of two-layer grounding system

In this paper, a comprehensive investigation of substation grounding soil structure effects on switching/lightning transients is presented. The full-wave computational solution Method of Moments (MoM) is adopted to solve Maxwell’s equations. The significant advantage of this technique is its ability to deal effectively with substation grounding systems (SGSs) at high frequency. This evaluation is carried out considering two soil structures: (1) a uniform soil and (2) soil with a layered structure. The impacts of both soil structures on the peak transient overvoltage values are compared. To begin with, the harmonic impedance matrix (HIM) of the layered multi-terminal SGS is computed. Then, a vector fitting approach is employed to incorporate the accurate SGS behavior by relying on the obtained HIM into time domain simulations. Finally, the transient overvoltages and maximum ground potential rise (GPR) are computed. The chief contribution of this paper is the transient assessment of the two-layer multi-terminal soil structure of the large SGS taking into account the frequency dependence model of the electrical parameters of soil, which is not generally investigated and instead, treated simplistically. According to the results of the study, the lack of an exact grounding system models may lead to underestimations/overestimations of the GPR and the overvoltage values. The results demonstrate the need for the grounding modeling of SGS considering layered soil structure to be incorporated into power system transient analysis in a wide range of frequencies.

Design of ultra wideband power amplifier based on a refining of exact harmonic impedance space

SummaryThis paper introduces a new theory which can be applied for the design of over‐octave ultra‐wideband power amplifier (PA). In this methodology, the impedance space of the ultra‐wideband PA can be refined, and the fundamental and various harmonic impedances have the same impedance space. This theory solves the problem that the harmonic impedance is not located in the fundamental impedance space because of its pure reactance form in the traditional hybrid continuous mode. To verify this theory, an ultra‐wideband PA with operating frequency range of 0.5–3.0 GHz (relative bandwidth of 143%) has been designed and fabricated. The experimental results show that the saturated output power over the entire operating band is 38.6–42.4 dBm, the power gain is 10.2–14.6 dB, and the corresponding saturated drain efficiency is between 50.1% and 65.1%.

Identification of harmonic source location in power distribution network

This paper presents the experimental set-up of identification of harmonic source location in the power distribution network using time-frequency analysis, known as S-transform (ST) at the point of common coupling (PCC). S-transform offers high frequency resolution in analyzing the low frequency component and able to represent signal parameters in time-frequency representation (TFR) such as TFR impedance (ZTFR). The proposed method is based on IEEE Std. 1459-2010, ST, and the significant relationship of spectral impedances components (ZS) that been extracted from the ZTFR, consist of the fundamental impedance (Z1) and harmonic impedance (Zh). This experiment was conducted out on an IEEE 4-bus test feeder with a harmonic producing load in numerous different scenarios. The experimental was tested and verified for three consecutive months. The findings of this study reveal that the proposed method provides 100 percent correct identification of harmonic source location.

Design of a broadband high‐efficiency power amplifier through mixed strategy

This letter presents a mixed strategy to design broadband high-efficiency power amplifiers (PAs), where the mixed continuous mode PA provide theoretical impedances. Furthermore, only a single one-stage coupler circuit with appropriate terminals is exploited to satisfy the fundamental and second harmonic impedances requirements necessary for mixed continuous mode PA realization. Combination of mixed modes PAs' desired impedances and the coupler's impedance frequency modulation trajectory, the available design frequency band can be determined. For validation, a broadband high-efficiency PA covering the frequency range 0.4–3.0 GHz is designed and then fabricated using a CGH40010F transistor. Measured results indicate that the implemented PA can deliver saturated output power of 40.2–42.7 dBm across the frequency range 0.4–3.0 GHz, with drain efficiency of between 60.4% and 74.5%.

Study on the estimation of harmonic impedance based on Bayesian optimized Gaussian process regression

System harmonic impedance is a key parameter in the evaluation of harmonic emission level and harmonic responsibility allocation. In order to solve the problem of calculating the harmonic impedance when background harmonics are different, a method of calculating the harmonic impedance based on Bayesian optimized Gaussian process regression (O-GPR) is presented. The harmonic impedance calculation method is based on the harmonic voltage and harmonic current obtained at the point of common coupling (PCC), and the Bayesian optimization of the Gaussian process regression is used to calculate the harmonic impedance of the system. Considering the influence of background harmonics, the harmonic equivalent models with non-Gaussian distribution background harmonics and Gaussian distribution background harmonics are built in the simulation analysis. The accuracy of this method under different background harmonics is analyzed, and its robustness is evaluated by error comparative analysis. Case analysis further verifies the effectiveness of the method. Also, the method is evaluated through indicators such as mean value, standard deviation and root mean square error. It provides ideas for practical engineering applications.

Grey wolf optimization-recurrent neural network based maximum power point tracking for photovoltaic application

To increase the photovoltaic (PV) power-generation conversion, MPPT is the primary concern. This works explains about the grey wolf optimization (GWO - RNN)-based hybrid maximum power point tracking (MPPT) method to get quick and maximum photovoltaic (PV) power with zero oscillation tracking. The GWO – RNN based MPPT method doesn’t need additional sensor for measuring irradiance and temperature variables. The NLT is used for the multi-level inverter (MLI) control strategy to achieve less harmonics distraction and less switching losses with better voltage and current profile. This employed methodology brings remarkable aspects in the PV boosting potential extraction. A GWO – RNN controlled LUO converter is a zero output harmonic agreement impedance matching interface that is MPPT is performed by placing the PV modules between the load regulator power circuit and the load regulator power circuit. To actualize the proposed hybrid GWO – RNN model for the PV system, perturb and observe, RNN, ant colony optimization, and artificial bee colony MPPT techniques are employed. The MATLAB interfaced dSPACE interface is used to finish the hands-on validation of the intended grid-integrated PV system. The obtained results eloquently support the appropriate design of higher-performance control algorithms.

Harmonic impedance estimation considering the correlation between harmonic sources☆

The previous utility harmonic impedance estimation methods are usually based on the assumption that harmonic sources are independent, which will cause large errors when the assumption is not met. To solve this problem, a method to weaken the negative effect of the correlation to impedance estimation is proposed. In the proposed method, the correlation between harmonic sources is reflected by that between constructed background harmonic voltage and measured harmonic current, and the effect of correlation is suppressed by obtaining the weak correlation time interval. First, construct the background harmonic voltage data based on the initial impedance, which changes in the range set according to the value of system short-circuit capacity. And then sort and divide these data into several sub-segments. Further, apply the correlation function to calculate impedance with each sub-segment. Finally, select the optimal impedance from all the initial impedances by comparing the difference between the calculated impedance and the initial impedance. The proposed method is more accurate when the correlation between harmonic sources is strong compared to other methods. Meanwhile, the processing of the background harmonic makes this method resist the significant background harmonic fluctuations. The effectiveness of the method is verified by simulation and field cases

Dual‐band high‐efficiency power amplifier using a D‐CRLH harmonic tuning network

AbstractOne dual‐band high‐efficiency power amplifier (PA) based on a D‐CRLH structure is presented. The D‐CRLH cell is employed to realize one dual‐band second harmonic trapping for the two operation frequency bands. Based on above design strategy, high PA efficiency at two frequency bands can be achieved by transferring the fundamental and second harmonic impedances to appropriate positions on the Smith chart. For demonstration, one prototype is designed at 2.3 and 3.5 GHz by using the proposed design strategy. The results indicate one peak output power of 40 and 40.8 dBm at the measured frequency of 2.2 and 3.2 GHz, respectively, while the maximum power‐added efficiencies (PAE) are 73.9% and 64% at the two frequencies.