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New energy and multiple loads, such as distributed wind-solar storage and charging, are connected to the distribution network through power electronic converters, which increases the harmonic content in the distribution network and causes operational safety risks. In this paper, the mathematical model of harmonic current and harmonic power content in a distribution network is constructed by an equivalent circuit and vector diagram. The distributed power flow controller is proposed for harmonic control of the distribution network. The mathematical expressions of the harmonic current and harmonic power based on a distributed power flow controller are constructed, and the control strategy of the distributed power flow controller for harmonic control is proposed. The simulation results show that the proposed method can effectively suppress the fifth and seventh harmonics of the distribution network. [ABSTRACT FROM AUTHOR]

To solve the problem of the large size of traditional industrial frequency phase-shift transformers and the harmonic distortion of multi-pulse wave rectifier systems, this paper proposes a three-stage shunt zigzag power electronic phase-shift transformer based on a double-tap multi-pulse wave rectifier, which combines the power factor correction (PFC) converter with the voltage-type SPWM inverter circuit to form a power electronic converter to realize the frequency boost and power factor correction. Through AC–DC–AC conversion, the frequency of the three-phase AC input voltage is increased, the number of core and coil turns in the transformer is reduced to reduce the size of the phase-shifter transformer, a zigzag structure of the phase-shifter transformer is used to solve the unbalanced distribution of current between the diode bridges, and a passive harmonic suppression method on the DC side is used to generate a loop current by using a group of single-phase rectifier bridges to regulate the input line current of the phase-shifter transformer. The phase-shifted voltage is input into two three-phase diode rectifier bridges to rectify and supply power to the load. Simulation and semi-physical test results show that the proposed method reduces the total harmonic distortion (THD) value of the input current of the phase-shifted transformer to 7.17%, and the THD value of the grid-side input current is further reduced to 2.49%, which meets the harmonic standard and realizes the purpose of power factor correction as well as being more suitable for high-power applications. [ABSTRACT FROM AUTHOR]

The single-phase three-leg unified power quality conditioner (UPQC) can achieve the functions of voltage compensation, reactive power compensation, and harmonic compensation. However, traditional control algorithms require a phase-locked loop to obtain the real-time phase angle of the grid voltage, which undoubtedly increases algorithm complexity. To simplify the phase-locked calculation, this paper proposes a control method without the phase-locked loop for the single-phase three-leg UPQC. In the proposed scheme, the instantaneous value of the grid voltage is employed to realize the grid integration control. Then, the load voltage reference is calculated in real time using a second-order generalized integrator. Moreover, a simple algorithm for reactive power and harmonic compensation is discussed, further simplifying the control algorithm. Finally, a small-scale experimental platform is built, and the effectiveness of the proposed method is verified by the experimental results. [ABSTRACT FROM AUTHOR]

For traction substation (TS), the harmonic current spectrum distribution of the left and right power supply sections has a large difference under different EMU operating conditions. This phenomenon will further affect the harmonic distribution of the entire traction power supply system and has the risk of harmonic distortion. At the same time, it may also cause interference to the communication line. In this paper, the transient direct current control technology is used to realize the converter of EMU, and then the TS side harmonic model under regenerative braking condition is realized. The harmonic problem, control process, and negative sequence problem caused by locomotive traction braking on the TS side under various working conditions are analyzed in detail. After connecting the C-type filter to the traction network side of the system, the THD (total harmonic distortion) is within the standard range, while the negative sequence problem of the system has worsened. Therefore, the parameters of the filter were optimized to improve both harmonics and negative sequence problems by combining the negative sequence characteristics under various operating conditions. The results show that the improved treatment can effectively control the harmonic problem. [ABSTRACT FROM AUTHOR]

It is difficult to achieve low-order harmonic tracking control without static difference when PI control is used in unified power quality conditioner (UPQC). What is more, the traditional PI parameter trial method has the problems such as low accuracy and anti-interference to meet the needs of real time control. Aiming at this issue, this paper proposes a UPQC harmonic control method based on the beetle antennae search (BAS) algorithm to optimize the parameters of quasi-proportional integral resonance (QPIR) controller. The harmonic current is detected by the i p – i q method based on the instantaneous power theory, and the detected signal is input to the QPIR controller. The controller parameters are optimized by the BAS algorithm to improve the dynamic response performance and control accuracy of the UPQC. Then, the MATLAB/Simulink software platform is used to build UPQC simulation models for PV and wind microgrids. Finally, the simulation comparison is verified between the optimized QPIR controller strategy based on by BAS method and PI control strategy based on neural network algorithm, respectively. The results show that using QPIR controller optimized through the beetle antennae search (BAS) method is more accurate and resistant to interference. So, the proposed UPQC control strategy has innovation and feasibility, and it can be applied in the practical engineering. [ABSTRACT FROM AUTHOR]

This paper proposes a 3.2–3.8-GHz Doherty power amplifier with simultaneous harmonic control, dual impedance matching, and wideband operation using a multi-state integrated matching network (MIMN). The MIMN controls the second harmonic open and third harmonic short at the center frequency of the carrier amplifier, enabling the carrier amplifier to perform inverse F operation. Similarly, it regulates the second harmonic short in the upper and lower sidebands, resulting in a hybrid harmonic operation. The proposed DPA, based on Cree's two HEMT devices, achieves a saturation efficiency of 62.6–69.9%, a 6 dB back-off efficiency of 47.3–61.1%, and a maximum output power of 43.63 dBm over the entire frequency range of 3.2–3.8 GHz. [ABSTRACT FROM AUTHOR]

With the deepening of electricity market reform in China, the competition in the electricity retail market becomes increasingly intense. Electricity retailers (ERs) need to explore new business models to enhance their competitiveness in the retail market. Meanwhile, with the improvement of industrial production and people's living standards, more and more nonlinear electrical equipment have been put into use, leading to severe harmonic pollution problems. Harmonic pollution causes loss of electricity, resulting in the economic loss of customers, especially for large industrial customers. In the above contexts, this paper proposes a novel business model that incorporates harmonic control as a value-added service into electricity retail contracts for utility-owned ERs. Both utility-owned ERs and customers can benefit from the designed business model. For customers, it helps them to improve the power quality while saving the electricity cost. For ERs, it helps them to cultivate the customer loyalty and improve the customer satisfaction. A case study is performed to demonstrate the effectiveness of the proposed business model. [ABSTRACT FROM AUTHOR]

This paper proposes a novel Class‐F broadband power amplifier design method. A Class‐F power amplifier for 1.3–2.5 GHz is fabricated by step‐matching, combining a harmonic control structure and a parasitic compensation circuit. A bandwidth expansion structure is established based on microstrip lines and capacitor. The proposed structure resolves the low efficiency caused by the coincidence of the fundamental frequency band and second harmonic frequency band, which allows the power amplifier to function properly from 1.1 to 2.5 GHz. A high‐efficiency broadband power amplifier is tested to find that the saturated output power with the proposed device is between 40.1 and 41.7 dBm, the gain is from 9.3 to 14.4 dB, and the drain efficiency is 60.8%–84.2% at 1.1–2.5 GHz frequency. [ABSTRACT FROM AUTHOR]

Active control systems are always restricted in one form or another. One of the restrictions is the lack of sensors or actuators for control implementation. This restricted control problem in the form of partial sensing and actuation thus poses a challenging problem for active controls, since most of the existing approaches make the implicit assumption that such information is readily available. This paper discusses the possibility of controlling structural vibration using restricted sensing and actuation control methodology. This opens a new avenue that, although counter to the current development in active control system designs through smart materials and smart structures, is readily applicable in practice. A number of fundamental results are derived concerning the active restricted controller properties, while algorithms are presented for the implementation. A case study is also provided, which demonstrates the feasibility of active restricted vibration control solutions. [ABSTRACT FROM AUTHOR]

This paper intensely studies the impact of the input nonlinearity caused by the transistor's feedback on the hybrid continuous class‐F power amplifier. The research extends the influence of input harmonics on class‐F power amplifiers to a more general form. Through waveform engineering, the impact of feedback is analyzed. By analyzing the change in cutoff angle caused by input nonlinearity, the change of the drain voltage and current waveforms of the hybrid continuous class‐F power amplifier can be obtained. The new drain voltage and current waveforms obtained from the analysis redefine the design space of source impedance and load impedance for the hybrid continuous class‐F power amplifier. By designing the corresponding input and output matching network, the second harmonic is suppressed, and finally, the hybrid continuous class‐F power amplifier achieves a high‐efficiency state. The research reveals that input harmonics also play an essential role in the design process of power amplifiers. A comparative experiment is designed to verify the theory. Simultaneously, a 1.6–2.8 GHz broadband hybrid continuous class‐F power amplifier is designed using this theory, with a saturation efficiency of more than 61.2% and a saturation power of more than 40.4 dBm. [ABSTRACT FROM AUTHOR]

In this paper, a new design method of induction filter distribution transformer suitable for low voltage distribution network system is proposed, and it is applied to the teaching case of comprehensive innovation experiment. In the design of induction filtering distribution transformer, the induction filtering technology is applied to the distribution transformer with Ddy connection group. By establishing the circuit mathematical model, the relationship between the harmonic current generated by the valve side and grid side current is deduced, and the filtering characteristics of induction filter distribution transformer are revealed. ANSYS/Maxwell software is used to establish a 3D model of the new transformer. On the model, the short-circuit impedance between the windings of the transformer is verified to meet the technical requirements by comparing the simulation energy method with the engineering magnetic circuit method. The filter branch is added through magnetic circuit coupling to monitor the grid side current of the transformer, and it is verified that it can effectively filter the harmonic pollution of the power grid. Finally, the correctness and effectiveness of the designed transformer are verified by experiments, which further stimulates students' learning interest and enthusiasm for innovation. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a novel Vector Control topology for stator current harmonic mitigation, due to the grid voltage harmonic content, focusing on mitigating the torque undulations in the Doubly Fed Induction Generator. The Proposed Controller referred here as to HVC - Harmonic Vector Control, is capable of mitigating any desired current harmonic. Voltage grid fifth, seventh, eleventh and thirteenth harmonic components causes current harmonic components of the same order (5th, 7th, 11th and 13th) in the generator but of higher relative amplitudes, due to the low stator series impedance. Therefore, the HVC has been tested for the control of such current harmonic components. As an advantage, the proposed control does not require a harmonic filter to estimate the harmonic content present in the stator current due to the power grid, which are the main disadvantages found in literature for the existing controllers. Firstly, the control topology is described and explained in detail. Next, simulation and experimental data are shown and compared to prove the suitability and efficacy of the proposed control. In the cases studied, the steady state error of the proposed controller is close to zero. Furthermore, the HVC can be used as a harmonic filter in DFIG and the harmonics can be chosen according to the application requirements. [ABSTRACT FROM AUTHOR]

This paper presents a novel structure of Hybrid Power Amplifier (HPA) to operate in two arbitrary classes of operation at two desirable frequencies. The proposed HPA is designed in concurrent F&F−1 classes, simultaneously for 5G application. Presented HPA can solve the harmonics interference problem for concurrent F and F−1 classes and also for any arbitrary class of operation in desired frequencies. The designed HPA operates at 1.5 GHz frequency in the F class mode, while operates at 2.1 GHz frequency in the F−1 class mode. A new method is presented by using two diplexers to provide two paths for signal in different frequencies. Two parallel paths are used at the output of the HPA circuit, so the proposed HPA can operate at two classes. Two diplexers are used in the HPA to make proper isolation between the designed paths. In design of the proposed HPA, according to the utilized diplexers, the amplifier can operate between two arbitrary classes of operation at desired frequencies without any specific switch. The measured drain efficiency (DE) and power added efficiency (PAE) parameters are 57 and 51%, respectively at 2.1 GHz, while measured DE and PAE are 64 and 54%, respectively at 1.5 GHz. [ABSTRACT FROM AUTHOR]

Smart grids aim to dramatically change residential area energy systems by creating active grid interaction. Specifically, renewable energies will play a key role when it comes to handling energy storage systems (ESS) at houses within a Smart Community. This paper presents a novel global control strategy for distributed micro-storage energy system. Each home receives the active and reactive power set- points from the Smart Community Energy Management System (SCEMS), providing energy resources to the community in function of the expected demand and production. Once SCEMS requirements are fulfilled, harmonic current components demanded by the household circuitry are injected according to the ESS available capacity. The proposed approach not only causes a local improvement in the power quality of the demanded current, but also contributes to the global power quality consumption of the community. Experimental tests are conducted using a prototype of the proposed ESS charger, validating the control strategies. [ABSTRACT FROM PUBLISHER]

Cascaded converters are generally used for medium-voltage (MV) grid-connected applications due to the limitation in the voltage rating of available silicon (Si) power devices. These converters find application in active power filters, STATCOM or as the active front end converters for solid state transformers at the distribution voltage levels. The high voltage wide bandgap semiconductor devices have enabled the grid connected operation of noncascaded converters. This results in high power density, less number of switching devices, and high efficiency for three-phase MV grid interface. This also results in control simplicity without the need for complex dc bus balancing algorithms otherwise needed for cascaded converters. However, such noncascaded, grid-connected converters introduce challenges in maintaining power quality at low currents. This paper investigates the harmonic performance and current distortion of the grid-connected, three-level neutral point clamped converter using 15 kV silicon carbide Insulated Gate Bipolar Transistor (IGBTs). A suitable control scheme for stable harmonic compensation is proposed. The challenges and control performance are explained through frequency domain analysis, simulations, and experimental validation on a developed prototype of the three-phase converter up to 4.16 kV, three-phase MV grid-connected operation. [ABSTRACT FROM AUTHOR]

In many engineering systems there is a common requirement to isolate the supporting foundation from low frequency periodic machinery vibration sources. In such cases the vibration is mainly transmitted at the fundamental excitation frequency and its multiple harmonics. It is well known that passive approaches have poor performance at low frequencies and for this reason a number of active control technologies have been developed. For discrete frequencies disturbance rejection Harmonic Control (HC) techniques provide excellent performance. In the general case of variable speed engines or motors, the disturbance frequency changes with time, following the rotational speed of the engine or motor. For such applications, an important requirement for the control system is to converge to the optimal solution as rapidly as possible for all variations without altering the system's stability. For a variety of applications this may be difficult to achieve, especially when the disturbance frequency is close to a resonance peak and a small value of convergence gain is usually preferred to ensure closed-loop stability. This can lead to poor vibration isolation performance and long convergence times. In this paper, the performance of two recently developed HC algorithms are compared (in terms of both closed-loop stability and speed of convergence) in a vibration control application and for the case when the disturbance frequency is close to a resonant frequency. In earlier work it has been shown that both frequency domain HC algorithms can be represented by Linear Time Invariant (LTI) feedback compensators each designed to operate at the disturbance frequency. As a result, the convergence and stability analysis can be performed using the LTI representations with any suitable method from the LTI framework. For the example mentioned above, the speed of convergence provided by each algorithm is compared by determining the locations of the dominant closed-loop poles and stability analysis is performed using the open-loop frequency responses and the Nyquist criterion. The theoretical findings are validated through simulations and experimental analysis. [ABSTRACT FROM AUTHOR]

This paper aims to provide control strategies for distributed micro-storage energy systems at the residential level to contribute to smart grid goals. A simulation model of an energy storage system (ESS) charger has been implemented to test these proposed control strategies. The smart community energy management system (SCEMS), acting as an aggregator of resources in the community according to the expected demand and production, sends to each individual home the active and reactive power set-points. Besides, in case the ESS has available capacity, once the SCEMS requirements are satisfied, it is used to absorb the harmonic current components demanded by the household circuitry. It allows a local improvement in the power quality of the demanded current, and thus contributes to the global power quality consumption of the community. Simulation results showing the operation of a local ESS at a home in a Smart Community are presented to validate the proposed control strategies. [ABSTRACT FROM AUTHOR]

The increasing penetration of photovoltaic (PV) systems, consisting of PV panel and PV inverter, may introduce power quality issues to the distribution power system. One critical concern is the harmonic distortion. This paper proposes an analytical harmonic model of PV inverters to assess its harmonic impacts on the distribution systems. The model is also verified by both simulation and laboratory experimental results. The proposed model indicates that the PV inverter has both harmonic source characteristic and harmonic impedance characteristic. Furthermore, the harmonic emission of PV inverters is affected by two grid operating conditions, namely the grid impedance and background harmonic voltage. The case studies demonstrate that the harmonic emission of a PV inverter without special harmonic control function can comply with the IEC standard under the normal grid operating conditions. It is verified that harmonic impacts of PVs are not a big concern. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract For traction substation (TS), the harmonic current spectrum distribution of the left and right power supply sections has a large difference under different EMU operating conditions. This phenomenon will further affect the harmonic distribution of the entire traction power supply system and has the risk of harmonic distortion. At the same time, it may also cause interference to the communication line. In this paper, the transient direct current control technology is used to realize the converter of EMU, and then the TS side harmonic model under regenerative braking condition is realized. The harmonic problem, control process, and negative sequence problem caused by locomotive traction braking on the TS side under various working conditions are analyzed in detail. After connecting the C-type filter to the traction network side of the system, the THD (total harmonic distortion) is within the standard range, while the negative sequence problem of the system has worsened. Therefore, the parameters of the filter were optimized to improve both harmonics and negative sequence problems by combining the negative sequence characteristics under various operating conditions. The results show that the improved treatment can effectively control the harmonic problem.

To solve the problem of the large size of traditional industrial frequency phase-shift transformers and the harmonic distortion of multi-pulse wave rectifier systems, this paper proposes a three-stage shunt zigzag power electronic phase-shift transformer based on a double-tap multi-pulse wave rectifier, which combines the power factor correction (PFC) converter with the voltage-type SPWM inverter circuit to form a power electronic converter to realize the frequency boost and power factor correction. Through AC–DC–AC conversion, the frequency of the three-phase AC input voltage is increased, the number of core and coil turns in the transformer is reduced to reduce the size of the phase-shifter transformer, a zigzag structure of the phase-shifter transformer is used to solve the unbalanced distribution of current between the diode bridges, and a passive harmonic suppression method on the DC side is used to generate a loop current by using a group of single-phase rectifier bridges to regulate the input line current of the phase-shifter transformer. The phase-shifted voltage is input into two three-phase diode rectifier bridges to rectify and supply power to the load. Simulation and semi-physical test results show that the proposed method reduces the total harmonic distortion (THD) value of the input current of the phase-shifted transformer to 7.17%, and the THD value of the grid-side input current is further reduced to 2.49%, which meets the harmonic standard and realizes the purpose of power factor correction as well as being more suitable for high-power applications.

In this paper, a frequency adaptive selective harmonic control (FA-SHC) scheme is proposed. The FA-SHC method is developed from a hybrid SHC scheme based on the internal model principle, which can be designed for grid-connected inverters to optimally mitigate feed-in current harmonics. The hybrid SHC scheme consists of multiple parallel recursive (nk ±m)-order (κ=0, 1, 2, . . ., and m ⩽ n/2) harmonic control modules with independent control gains, which can be optimally weighted in accordance with the harmonic distribution. The hybrid SHC, thus, offers an optimal tradeoff among cost, complexity, and also performance in terms of high accuracy, fast response, easy implementation, and compatible design. The analysis and synthesis of the hybrid SHC are addressed. More important, in order to deal with the harmonics in the presence of grid frequency variations, the hybrid SHC is transformed into the FA-SHC, being the proposed fractional-order controller, when it is implemented with a fixed sampling rate. The FA-SHC is implemented by substituting the fractional-order elements with the Lagrange-polynomial-based interpolation filters. The proposed FA-SHC scheme provides fast on-line computation and frequency adaptability to compensate harmonics in grid-connected applications, where the grid frequency is usually varying within a certain range (e.g., 50 ± 0.5 Hz). Experimental tests have demonstrated the effectiveness of the proposed FA-SHC scheme in terms of accurate frequency adaptability and also fast transient response. [ABSTRACT FROM AUTHOR]

Copyright of International Architecture is the property of Omniscient Pte. Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Parallel operation of current source converters (CSCs) is an attractive approach for medium-voltage high-power conversion applications. In order to achieve proper dc rail current balancing of parallel CSCs while maintaining a good control of ac line current quality at low switching frequency (typically at a few hundred hertz), an improved quasi-selective harmonic elimination (Q-SHE) modulation method with online delay angle and bypass band adjustment is proposed. At first, each CSC positive rail dc current is regulated by tuning the delay angle of the corresponding line reference current with respect to the grid voltage. At the same time, the negative rail dc currents balancing errors are compensated by injecting small bypass pulses into the conventional SHE pattern. By the coordinated control of the aforementioned methods, an accurate dc rail currents balancing and an enhanced line current quality can be achieved at both the steady and the transient states. [ABSTRACT FROM AUTHOR]

In this paper, we apply the heuristic method for determination of control functions for controllability analysis of nonlinear power systems. The problem of control of quasi-linear systems under proper assumptions on the nonlinear term is considered in the general statement. Making use of the Green's function solution of nonlinear systems, the exact and approximate controllability conditions are expressed in terms of unknown controls in an explicit form. The way of resolving controls determination is discussed. As a particular application, a one-machine infinite-bus system is considered described by a coupled system of three first order ordinary differential equations. Two heuristic forms of admissible controls are considered providing approximate controllability within the same amount of time having different intensities. Results of numerical simulations are presented and discussed. [ABSTRACT FROM AUTHOR]

Abstract This paper, presents a methodology for designing concurrent dual-band power amplifier (DB-PA) that operates in Class-F−1 at one band and Class-J or Class-J−1 at the other band. It is shown that the second harmonic engineering of Class-F−1 and Class-J or Class-J−1 makes these classes of operation compatible in terms of dual-band realization without introducing higher complexity in realizing the harmonic control network. The design methodology is well illustrated and is validated by implementing a Class F−1/J concurrent dual-band PA operating at 1842 and 2655 MHz bands. Experimental results exhibit output powers of 40 and 41 dBm and efficiencies of 76% and 70% at the lower and upper bands, respectively. The AM-AM, AM-PM and two-tone third-order inter-modulation distortion results imply a good linearity behaviour of the designed PA. Furthermore, the linearity of the designed DB-PA is also verified with a single carrier WCDMA signal, where the PA shows better than −20 dBc adjacent channel power ratio in saturation region at both of the operating bands. [ABSTRACT FROM AUTHOR]

The single-phase three-leg unified power quality conditioner (UPQC) can achieve the functions of voltage compensation, reactive power compensation, and harmonic compensation. However, traditional control algorithms require a phase-locked loop to obtain the real-time phase angle of the grid voltage, which undoubtedly increases algorithm complexity. To simplify the phase-locked calculation, this paper proposes a control method without the phase-locked loop for the single-phase three-leg UPQC. In the proposed scheme, the instantaneous value of the grid voltage is employed to realize the grid integration control. Then, the load voltage reference is calculated in real time using a second-order generalized integrator. Moreover, a simple algorithm for reactive power and harmonic compensation is discussed, further simplifying the control algorithm. Finally, a small-scale experimental platform is built, and the effectiveness of the proposed method is verified by the experimental results.

Summary: We propose a broadband high‐efficiency power amplifier (PA) with output power between 42.6 and 44.7 dBm, drain efficiency (DE) over 62%, and power additional efficiency (PAE) over 52% in the 2.3–3.5GHz frequency band. This PA effectively combines the high‐efficiency characteristics of class‐F PAs with the advantages of controlling the second harmonic for obtaining high efficiency at large bandwidth. The Dual Band Harmonic Control and Matching Network (DBHCN) realizes the conversion from 50 Ω to high‐efficiency impedance space (HEIS) while controlling the high‐order harmonics in different frequency bands. The proposed PA can be used for the fifth‐generation mobile communication technology (5G) base stations and broadband radars. [ABSTRACT FROM AUTHOR]

Modern industries face increasing demands to improve the precision and workability of equipment, leading to stringent requirements for hydraulic servo systems in terms of flow, accuracy, and output power. High‐flow servo valves and multi‐valve synchronous control methods have seen more applications in the industry to meet these demands. However, high‐flow servo valves are expensive and have unsatisfactory performance, and synchronous control methods require servo valves to have the same hydraulic characteristics, resulting in higher cost and lower accuracy of high‐flow hydraulic servo systems. Also, very little has been conducted on controlling single actuators using multiple valves. In this study, we design a novel dual‐valve hydraulic servo system structure with a high‐flow proportional directional valve that is connected in parallel with a low‐flow servo valve and further develop the mathematical model of this dual‐valve system. Next, a harmonic control scheme was proposed, which included a flow allocation layer and trajectory tracking layer. Thereby, we achieved optimal control of two valves, and robust performance was guaranteed. Finally, we investigate the relationships between the flows of two valves, the deadband of the proportional directional valve, and trajectory tracking errors. Experimental results show that the proposed control scheme can effectively adjust the output flow of each valve dynamically according to the tracking trajectory and the hydraulic characteristics of the two valves, and the tracking performance of the servo system is significantly improved. This method is promised to enable the realization of an economical, high‐flow, high‐precision hydraulic servo system that can be generally used in various fields, such as marine engineering and construction. [ABSTRACT FROM AUTHOR]

This paper proposes a novel online solution, i.e. Modified-Equilibrium Optimizer-Levenberg-Marquardt (M-EO-LM) algorithm, for the symmetric and asymmetric harmonic elimination pulse width modulation (HEPWM) methods of the modular multilevel cascaded converters. A detailed comparison of the proposed M-EO-LM algorithm with nine state-of-the-art algorithms is also presented for twenty-nine unimodal, multimodal and composite benchmark test functions. M-EO-LM has proven its effectiveness by outperforming these algorithms. EO algorithm is first introduced for the solution of HEPWM method. Its comparison with several state-of-the-art algorithms depicts its superiority; but it gets stuck in the local minima. Modified-EO (M-EO) solves the problem by enhancing its exploration ability, and is then attached to a rapid calculus-based LM method to form the novel M-EO-LM algorithm. M-EO-LM algorithm initiates the solution process by solving the HEPWM equations for nine angles ( $N=9$ and $0.78\leq M\leq 6.86$ ) offline in only two iterations, depicting its remarkable convergence ability. Solution angles are then divided into several groups, serving as the search space for the online M-EO-LM algorithm. A comparison between HEPWM and nearest level modulation methods based on the output voltage THD values is provided to report the maximum number of solvable HEPWM angles for a complete online solution. These angles ( $N=8$ and $0.78\leq M< 5.18$ ) are then solved online using the M-EO-LM algorithm. Comparing the computational times of the proposed online algorithm with differential evolution-Newton Raphson algorithm proves the rapid solution behavior of the M-EO-LM algorithm, validated through the simulation and real-time experimental results.

In this brief, a dual-band complex impedance transformer is proposed and applied to design a concurrent high-efficiency power amplifier (PA) with a widely spaced frequency. The transmission line parameters of the PA, including dual-band harmonic control network, and dual-band fundamental matching network, are obtained using the derived analytical design formula, which avoids the time-consuming numerical optimization. In addition, the proposed transformer can reduce the probability to use the transmission line with extremely high or low impedance. Simulation and measurement verified that the fabricated dual-band PA achieves the peak power-added efficiency (PAE) of 78.8% and 73.1% with the output power of 42.5 and 40.2 dBm at 0.88 and 2.4 GHz, respectively. [ABSTRACT FROM AUTHOR]

With wind power，photovoltaic power generation and other large distributed power connected to the grid，and the increasing of the user demand for electricity，higher requirements will be put forward for power quality. Building power quality comprehensive experimental platform can make students studying connect with the development trend of smart grid. Firstly，this paper presented the structure and working principle of power quality experimental platform. Besides，it explained the function and implementation of tiie platform in detail. Finally，it introduced the application in experimental teaching combining the experimental content based on the platform. [ABSTRACT FROM AUTHOR]

A design methodology of a $C$ -band high-efficiency Doherty power amplifier (DPA) with harmonic control is presented in this letter. The equivalent parasitic network (EPN) of the packaged device is constructed by a deembedding technique. The phase delay caused by the transistor parasitics is calculated using the scattering matrix of the EPN. Besides, the influence of the phase delay on DPA design is analyzed. To improve the efficiency at output back-off (OBO) power level, postmatching network (PMN) is used to control the second harmonic. A high-efficiency DPA working over 6.4–7.1 GHz is implemented, fabricated, and measured. The DPA delivers a saturation output power ($P_{\text {sat}}$) of 39.6–41.6 dBm. Meanwhile, the drain efficiencies in the interested frequency band are 45.1%–53.2% and 34.5%–43.1% at the $P_{\text {sat}}$ and 6-dB OBO power levels, respectively. [ABSTRACT FROM AUTHOR]

This article proposes an improved odd-harmonic repetitive controller (IORC) for a Ćuk-derived inverter. The IORC is composed of a modified structure of an odd-harmonic repetitive controller (ORC) combined with a proportional-integral (PI) controller and a feedforward controller to achieve a zero steady-state error in the Ćuk-derived inverter. The IORC features much larger gains at odd-harmonic frequencies by modification of an existing ORC, so both its convergence rate and transient response become much faster. The added benefit of using the IORC is that it has wider bandwidth at odd-harmonic frequencies, so it is more insensitive to the grid frequency fluctuation. The IORC also adopts a linear phase-lead compensator to compensate for the phase lag of the Ćuk-derived inverter. Hence, the IORC can effectively eliminate the odd-harmonic components in the output current of the grid-connected Ćuk-derived inverter while using less memory space. However, the distinctive structure of the IORC makes it difficult to guarantee the stability of the overall control system. Thus, in this article, a new stability analysis method is developed for the IORC system, and then a practical design guideline is also provided to obtain the optimal control parameters. Experimental results are presented to validate the proposed controller in the 300-W Ćuk-derived inverter prototype. [ABSTRACT FROM AUTHOR]

While continuous-mode Doherty power amplifier (CM-DPA) can achieve high efficiency at output back-off (OBO) power levels, their achievable bandwidth and load modulation have not yet been fully investigated. This brief reveals that the bandwidth of CM-DPA is limited by the impedance trajectories of the peaking transistors. In particular, the peaking transistor degrades the bandwidth in the high power region and limits the fractional bandwidth (FBW) of the CM-DPA. Moreover, based on post-matching Doherty architecture, an analytical method for harmonic control in CM-DPAs is presented. A broadband CM-DPA with harmonic control is implemented, fabricated and measured. The CM-DPA delivers a saturation output power (Psat) of 42.6–44.4 dBm from 1.50 to 2.55 GHz, i.e., FBW of 51.8%. The drain efficiencies in the interested frequency band are 50.7%–69.7% and 43.3%–57% at the Psat and 6-dB OBO power levels, respectively. [ABSTRACT FROM AUTHOR]

In this letter, a distributed element‐based load network is proposed for designing a high‐efficiency dual‐band (DB) 5‐W Class‐E power amplifier (PA), at two widely spaced frequencies of 2.4 and 5.8 GHz. This network consists of two different stages. The first stage deploys a flexible network configuration with crossed transmission lines (TLINs) to provide concurrent DB fundamental matching in a closed‐form derivation, which transforms the standard resistance of 50 Ω directly to the optimal complex impedances. By tolerating the combination of the up‐side and down‐side TLINs, the size of the overall circuit as well as the implementation complexity are reduced. The second stage uses a DB TLIN‐based resonator preceded by a series 50 Ω stub to control the harmonic impedances without altering the fundamental impedances, ensuring high efficiency at the fundamental frequencies. The measured prototype shows highest power added efficiency (PAE) of around 62.9% and 61.7% with output power of about 39 and 35 dBm at 2.45 and 5.76 GHz, respectively. [ABSTRACT FROM AUTHOR]

As the amount of decentralised generation is continuously increasing, the control and maintenance of grid stability become more complex. This is mainly caused by a change of production capacities from the high‐voltage area to the distribution network. As most renewable energy sources in the distribution network are nowadays connected to power electronic converters, harmonic distortion as well as asymmetries (electric vehicle chargers, household photovoltaic systems) are increased. To ensure stability, reliability, and efficiency of the energy distribution network, a grid regulator including asymmetrical and harmonic control is introduced. This grid regulator consists of two inverter systems, where one is connected by a series booster transformer in line, while the other is connected in parallel to the line, capable of decoupling network segments from each other. After a successful verification in simulation, the control structure is implemented in a real hardware setup. The results show that the introduced system is able to decouple network elements in case of an unbalanced situation as well as harmonic current and voltage distortion. To simplify inverter hardware a silicon carbide hardware topology is introduced with a reduced number of switches. Lower switching losses result in higher overall system efficiency. [ABSTRACT FROM AUTHOR]

In this paper, a design approach for a high-efficiency concurrent dual-band power amplifier (PA) with precise harmonic control up to third order is proposed. With the precise harmonic control approach, the high-efficiency performance of the PA can be improved at two arbitrary wide interval frequencies. Based on the inherent impedance matching flexibility of the continuous Class-F (CCF) operating mode, the design spaces of fundamental and harmonic impedances of the PA are largely expanded. The optimal impedances of a CCF PA mode at the internal current-generator (I-gen) plane and package plane are investigated, respectively, and a novel dual-band matching network topology is designed to simultaneously present required load impedances at the fundamental and harmonic impedances of both operation frequencies. First, a harmonic control network is designed to control the harmonic impedances precisely for CCF operation. Then, the fundamental impedances are synthesized using the real frequency technique. To verify the validity of proposed methodology, a dual-band CCF PA operating at 2.6 and 3.5 GHz is designed, fabricated, and measured. The measurement results show that the peak drain efficiency is 76.7% with an output power 42.4 dBm at the lower band and 72.8% with an output power 41.1 dBm at the upper band.