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A novel Ka-band compact parallel-coupled microstrip bandpass filter with harmonic suppression performance has been designed, implemented and tested on GaAs MMIC.

This proposed filter consists of modified coupled-line units with T-shaped open-stubs.

The proposed filter with T-shaped open-stubs is valuable in performance with low loss at fundamental frequency, suppression at harmonic frequencies and small size. The simulation is based on full-wave electromagnetic analysis and the measurement is based on chip test. It shows an insertion loss below 1.2 dB, return loss better than 20 dB in the pass band and high than 28 dB suppression at harmonic frequencies.

This Ka-band MMIC filter with harmonic suppression is attractive for the millimeter-wave system.

As arc suppression coils (ASCs), magnetically controlled reactors (MCRs) are usually operated in the single-phase mode. Due to the lack of a third order harmonic compensation circuit, the current harmonics are high. The purpose of this paper is to propose a novel structure of MCR and a genetic algorithm (GA) to determine the parameters which will result in minimum total harmonics.

This paper proposes the structure and the working principle of the multi-valve controlled saturable reactor (MCSR). There are several sorts of magnetic valves in the iron cores of the MCSR. The saturation degree of each magnetic valve is different when the same direct component of the magnetic flux is generated in the iron core, therefore current harmonics of different phases emerging, i.e. the total harmonics can be reduced. The magnetization characteristics and the mathematical model of the current harmonics of the MCSR are presented by introducing three parameters. The optimal values of the parameters that result in the smallest total harmonic distortion in the output current are calculated by a GA.

The simulation and experimental results are coincident with the theoretical analyses, which prove the effectiveness of the proposed method on harmonic suppression.

The method proposed in this paper can successfully reduce the current harmonics of the conventional MCR, including but not limited to the ASC. A prototype MCSR (540 kVA/10 kV) has been designed and constructed.

In this paper, a MCSR is proposed. The mathematical model of the MCSR for harmonic analysis is developed. The optimal parameters that result in the smallest THD in the output current are calculated. The mathematical model can be also used for the harmonic analysis of conventional MCRs.

This study aims to design a compact filtering monopole antenna for 5G communication. The design is most suited for various applications within the frequency range of 2.2–3.8 GHz. It offers enhanced bandwidth and reasonable gain with wide-stopband performance.

A low-pass filter (LPF) of complementary split ring resonator (CSRR) with short-circuited stub lines is integrated with a compact defected coplanar waveguide fed truncated circular monopole ultrawideband (UWB) antenna. The reference UWB antenna etched on an FR4 substrate was coupled to the designed LPF to transform the UWB antenna into a wideband antenna. The effect of coupling is analyzed based on the real and imaginary responses of the terminal impedance (ZT) curve. Three short-circuited stub lines of asymmetric lengths are added to the CSRR LPF to suppress harmonics, thereby enhancing the stopband performance and impedance matching between the elements. The proposed filtering antenna is fabricated using a photolithography process, and the corresponding results are measured using a network analyzer (N9951A). The radiation parameters of the proposed filtering monopole antenna are tested in the anechoic chamber. The simulated/measured results are compared and are found in agreement with each other.

The proposed design suppresses 6.5f0 harmonics, resulting in wide stopband performance and increased gain selectivity at the transition edge. A peak suppression of −41 dB and an average suppression of −18 dB were attained throughout the stopband. An operating fractional bandwidth of 54.5%/143% with a peak gain of 3 dBi/5 dBi was obtained. The proposed filtering antenna supports 5G applications such as WiMAX, WLAN, n7, n38 IMT-E, n30 WCS, n40 TDD, n41 TDD, n48 TDD, n78 TDD and n90 TDD.

The proposed design is novel and compact and has a wide application in 5G communication. With the filter, the antenna operates in wideband, and without the filter, it operates in UWB. Besides, it offers enhanced stopband performance with high gain selectivity at the transition edge. Comparatively, a 50% improvement in bandwidth, 52% improvement in size reduction and 33% improvement in harmonic suppression are attained.

This study aims to focus on the grid connected inverter.

The grid connected inverter for harmonic suppression was designed, the topological structure of the inverter and the design of LCL filter were analyzed, then a PIR controller was proposed and finally simulation and experiment were carried out.

The simulation results showed that the distortion rates of the 5th, 7th and 11th harmonics under PIR control were 0.14%, 0.13% and 0.06%, respectively, which were significantly lower than that under PI control. The system test results also showed that the current waveform under PI control was rough and total harmonic distortion (THD) content was 3.8%; under PIR control, the grid connected current waveform was relatively smooth, with fewer spikes and burrs, and the THD content was 1.9%, indicating that the harmonics were effectively suppressed.

The experimental results verify that the inverter and PIR controller designed in this study are effective for harmonic suppression. This work makes some contributions to the improvement of the effect of harmonic suppression and promotion of the better application of grid connected inverter.

The purpose of this paper is to solve the reactive power adjustment and the overvoltage suppression problems in the extra high voltage (EHV) long distance grid, which often appears transient overvoltage, light load loss and other issues.

One 800 kV EHV magnetically saturation controllable reactor (MSCR) used self-power supply control system is designed. The structure and the working mechanism of the novel MSCR are analyzed in detail. Then the control and capacity step adjustment characteristics are obtained by experiments. The harmonic characteristic is studied by theoretical analysis and low voltage test.

To solve the problem of harmonics in the working current of nets windings, the fifth and the seventh filers are equipped between the compensation windings and the control system. The effectiveness of the harmonic suppression method is proved by simulation and experiments.

It proves that the 800 kV EHV MSCR design in this paper can achieve the purpose of the reactive power continuous linear adjustment, and the capacity adjustment is sensitive. After filtering, the harmonics level of the working current meets the standard of the EHV grid.

The purpose of this paper is to present a K-band modified hairpin bandpass filter on a planar circuit with harmonic suppression and compact size.

The inter-connect transmission lines of conventional hairpin filter are replayed by T-shaped open stub to achieve transmission zero for second harmonic. This filter is simulated and optimized by using electromagnetic simulation software and tested on-chip.

This proposed filter shows the return loss of better than −10dB, the insertion loss of better than 2 dB in pass-band and suppression of more than 40 dB at second harmonic.

The proposed filter can be designed on monolithic microwave integrated circuit, PCB or LTCC and it is useable for microwave and microwave and millimeter-wave systems.

This study aims to construct a novel maximum power tracking control system for the direct drive permanent magnet synchronous generator (PMSG) of the wind energy conversion system (WECS) to solve the following problems: how to effectively eliminate the system’s model parameter disturbances and speed up the dynamic performance of the system; and how to eliminate harmonics in WECS under different wind speeds.

To obtain the maximum output power of PMSG at WECS under different wind speeds, the following issues should be considered: (1) how to effectively eliminate the system’s model parameter disturbances and speed up the dynamic performance of the system; and (2) how to suppress system harmonics. For Problem 1, adding d–q compensation factors to active disturbance rejection control (ADRC) for the current loop realizes the d–q axis decoupling control, which speeds up the dynamic performance of the system. For Problem 2, the resonant controller is introduced into the ADRC for the current loop to suppress harmonic current in WECS under different wind speeds.

The simulation results demonstrate that the proposed control method is simpler and more reliable than conventional controllers for maximum power tracking.

Compared with traditional controllers, the proposed controller can speed up the dynamic performance of the system and suppress the current harmonic effectively, thus better achieving maximum power tracking.

Electric spring (ES) is a demand response method that can stabilize the voltage of critical loads and improve power quality, especially in a weak power grid with a high proportion of renewable energy sources. Most of existing ESs are implemented by voltage-source inverter (VSI), which has some shortcomings. For example, the DC-link capacitor limits the service life of ES, and the battery is costly and hard to recycle. Besides, conventional VSI cannot boost the voltage, which limits the application of ES in high-voltage occasions. This study aims to propose a novel scheme of ES to solve the above problems.

In this work, an ES topology based on current-source inverter (CSI) without a battery is presented, and a direct current control strategy is proposed. The operating principles, voltage regulation range and parameter design of the proposed ES are discussed in detail.

The proposed ES is applicable to various voltage levels, and the harmonics are effectively suppressed, which have been validated via the experimental results in both ideal and distorted grid conditions.

An ES topology based on battery-less CSI is proposed for the first time, which reduces the cost and prolongs the service time of ES. A novel control strategy is proposed to realize the functions of voltage regulation and harmonic suppression.

Traditional switching harmonic suppressor design methods require domain experts to adjust design parameters due to various complex performance requirements and practical limitations in switching ripple suppressor designs. The purpose of this paper is to present a method for filter parameter design.

An improved non-dominated sorting genetic algorithm II (NSGA II) was used in the inductor-capacitor-inductor (LCL) filter design to find the optimal design parameters, and a method was proposed to handle the constraints by transforming the them into decision variables.

The performance of the proposed algorithm in parameter designing was verified by simulation on MATLAB and experimental results on hardware-in-the-loop plat-form with StarSim software. The results indicate that the optimization algorithm has a better effect than the traditional expert parameters on each optimization index, especially on the switching harmonic suppression.

The paper presents an improved multi-objective optimization algorithm with ingenious constraints handing to obtain better filter parameters and reduces switching harmonics.

Four‐quadrant AC‐DC converters are one kind of the most common and popular AC‐DC converters, which are serious EMI sources. The purpose of this paper is to propose a novel control for four‐quadrant AC‐DC converters to suppress the generated electromagnetic interference (EMI).

A chaotic carrier plays an important role to implement the chaotic PWM control. The relationship between the EMI distribution and carrier frequency is given by deducing and analyzing the harmonic components of the AC‐DC converter. The comparison of chaotic PWM control and random PWM control in suppressing EMI are provided.

The simulation results prove the effectiveness of the proposed chaotic PWM control on EMI reduction.

The effects of EMI suppression under different chaotic carriers will be theoretically analyzed in the future work.

The proposed chaotic PWM control can suppress EMI for converters without adding additional devices or components, therefore, without increasing the volume, weight and cost of converters.

In this paper, a novel chaotic pulse width modulation (PWM) control is proposed and implemented into a four‐quadrant AC‐DC converter for electromagnetic interference (EMI) suppression, moreover, the total harmonic distortion (THD) of the input AC current is also improved under chaotic PWM control.