Harmonic Rejection Performance Research Articles

Design of a wideband, highly efficient FPA using an asymmetrical open-circuit coupled-lines-based filtering matching network

This study introduces a novel approach to designing a broadband, highly efficient filtering power amplifier (FPA) characterized by unique integrated filtering capabilities. Central to the proposed technique is the utilization of an asymmetrical open-circuit coupled-lines bandpass filter (BPF), serving dual functions as both an input matching network and an output matching network. Notably, this filter design not only enhances the bandpass filtering response but also significantly improves second harmonic rejection performance. To validate this methodology, a broadband FPA is implemented, employing the Cree 10 W GaN HEMT. The proposed FPA, operating between 2.0–3.0 GHz, achieves a peak drain efficiency of 45.9 %-73.26 %, corresponding to a peak output power of 38.5–41.95 dBm at saturation. This marks a notable efficiency enhancement compared to recent research findings. It is believed that the FPA solution is custom-tailored to meet the demanding requirements of modern base stations, striking the balance between improved power-efficiency and good filtering performance.

UDE-Based Current Controller With Enhanced Grid Frequency Fluctuation Adaptability for LCL-Type Grid-Tied Inverters

The uncertainty and disturbance estimator (UDE) with a time delay filter has been widely used for inverter systems due to its satisfactory harmonic rejection performance. However, the control performance may be affected when the grid frequency fluctuates. In this article, a modified UDE (FUDE) is proposed to improve the grid frequency fluctuation adaptability of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCL$</tex-math></inline-formula> grid-tied inverter systems, which contains a compound filter consisting of time delay, zero-phase low-pass, and high-pass filters. Compared with the traditional time delay UDE, it can offer a wider notch bandwidth at the selected frequencies. A dual-loop controller is built in the separate-structure-type UDE-based controller, containing an outer loop PR controller and an inner loop FUDE. The sufficient conditions for the system stability are obtained by the small-gain theorem. The comparison experiments of the dual-loop controller with the proposed FUDE and the conventional time delay zero-phase low-pass UDE are performed on a 2-kW experimental platform, and the results demonstrate the effectiveness of the proposed FUDE.

A Compact Bandstop Filter Design Using DMS-DGS Technique for Radar Applications

In this study, a novel compact bandstop filter (BSF) by utilizing the defected ground structure (DGS) and defected microstrip structure (DMS) techniques are presented. DGS, DMS, and compensated capacitors are used on both bottom and top layers to obtain sharp transition and wider stopband. The operating frequency bandwidth of the filter can be comfortably regulated by tuning the dimensions of the etched structures. In addition to parametric studies, an equivalent circuit model of the proposed filter is extracted. The BSF has an insertion and return losses better than –1.6 and –17 dB in the passband, respectively. Moreover, the developed filter covers X-band frequency range and has stop bandwidth of 10.8–11.8 GHz with the rejection of better than 20 dB. Furthermore, the measurement and simulation results are in compliance with the suggested method. The proposed BSF has a very small size of 14.28 mm ×× 4 mm ×× 0.508 mm and has the potential to be used for radar applications with its high compactness, low cost, and high harmonic rejection performance.

A 22.7‐ to 44.2‐GHz Darlington dual‐injection injection‐locked frequency tripler with &gt;35dBc harmonic rejection for multiband 5G communication systems

AbstractThis paper presents an ultra‐wideband varactor‐less injection‐locked frequency tripler (ILFT) based on Darlington dual‐injection topology targeting millimeter‐wave multiband fifth generation (5G) communication systems. By utilizing the proposed Darlington dual‐injection injector, the current injection efficiency is improved; thus, the locking range is extended significantly without introducing the varactors. In addition, the Darlington dual‐injection topology enhances the harmonic rejection performance by suppressing undesired harmonics. Implemented in 65‐nm CMOS (Complementary Metal Oxide Semiconductor) technology, the proposed ILFT can operate from 22.7 to 44.2 GHz and consumes 6.2 mA at 1.2 V supply voltage. The harmonics rejection is more than 35 dBc and occupies 0.17 mm2.

Iterative learning control of dispatchable grid-connected distributed energy resources for compensation of grid current harmonic distortions

This paper proposes a power regulation scheme for dispatchable grid-connected distributed energy resource (DER) units based on the iterative learning control (ILC) strategy. The proposed control provides fast and stable control of the real and reactive powers that the DER unit delivers to the grid. In addition, it compensates the harmonic distortion of the grid current caused by the local nonlinear loads and delivers a high quality power to the grid. To this end, the paper presents the mathematical model on which the proposed control is based, as well as the control design methodology. A new MIMO iterative learning control with perfect power tracking and harmonic rejection performance as well as minor measurement requirements is proposed. The performance of the proposed ILC strategy is demonstrated through time-domain simulation of a grid-connected DER unit under various operating scenarios, and it is compared with the performance of the conventional control based on the instantaneous power theory (IPT).

Adaptive Virtual Impedance of Grid-Tied Inverters to Enhance the Stability in a Weak Grid

In a weak grid, especially with a grid-voltage proportional feedforward controller, the grid-tied inverter tends to interact with the grid impedance and thus suffers from poor power quality and even instability. In order to improve the stability, serial-parallel virtual impedance based on the derivative controllers of grid current and voltage is proposed in this paper. With the aim of optimizing the performance of the inverter for a variety of grid impedance, these derivative coefficients are adaptively tuned by the constraint of a minimum leading phase which is determined by the phase margin and the current tracking response. With this proposed adaptive virtual impedance, the grid-tied inverter can operate stably under a wide variety of grid impedance and voltage harmonic rejection performance is also improved. Simulation and experimental results validate the effectiveness of the proposed method and design methodology.

Cooperative Operation of DG Inverters and a RIHAF for Power Quality Improvement in an Integrated Transformer-Structured Grid-Connected Microgrid

Harmonics in microgrids have attracted intensive power quality concern. It is analyzed in this paper that both currents in the voltage-controlled DG inverter side and the main grid side are easily involved in harmonic distortion due to nonlinear loads and background harmonics. To deal with this issue, a cooperative operation strategy for the DG inverters and a reactor-integrated hybrid active power filter (RIHAF) are proposed based on an integrated transformer-structured grid-connected microgrid. First, for the purpose of cost reduction and covering space saving, an integrated transformer based on a reactor integration technique (RIT) is conceived and the principle of the RIT is illustrated. To improve the current quality in the DG inverter side, a harmonic impedance reinforcement control method is employed to enhance the harmonic rejection performance of the voltage-controlled DG inverter. Besides, taking advantage of the integrated transformer, a RIHAF is proposed to suppress the current harmonics in the main grid side. Detailed simulation results show that current harmonics in both the DG inverter side and the main grid side can be simultaneously suppressed with the proposed cooperative operation strategy. Finally, experimental results from a scaled-down integrated transformer-structured microgrid platform are presented to verify the effectiveness of the RIT and the proposed cooperative operation strategy.

Q-based design method for impedance matching network considering load variation and frequency drift

The key step in Q-based design for T or Pi network impedance matching is selecting an appropriate Q-factor. The harmonic rejection performance of impedance matching networks is the main concern of Q selection. However, for applications wherein the impedance to be matched is variable or the frequency is drifty, it is not the harmonic rejection but the stability, which is the main performance consideration. This paper analyzes T network impedance matching. The relationship between reflection coefficient, load variation, and frequency drift is determined, which provides a reference for Q selection. The Q-based design process presented in this paper can strike a balance between stability and harmonic rejection, which can then be applied in other cases involving load variation or frequency drift.

X-ray mirror reflectivities from 3.8 to 50 keV (3.3 to 0.25 Å) Part II—Pt, Si and other materials

A highly polished platinum coated mirror was demonstrated to reflect X-rays with high efficiency up to 38 keV (0.33 Å). For the mirror operating at an angle of incidence of 8 mrad, the mirror reflected 8 keV X-rays with a 70% efficiency while the reflectivity at 16 keV was only 0.6%. The measured reflectivity of the mirror fell off in energy about 30 times faster than predicted by simple Fresnel theory assuming a smooth surface. This implies, for instance, that the harmonic rejection performance of platinum coated X-ray mirrors at synchrotron radiation sources may be significantly better than expected. In other measurements, very imperfect surfaces of unpolished sheet aluminum, copper and stainless steel surprisingly reflected as much as 30–50% of the X-rays incident upon them at small glancing angles.