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Wind power is an exceptionally clean source of energy; its rational utilization can fundamentally alleviate the energy, environment, and development problems, especially under the goals of 'carbon peak' and 'carbon neutrality'. A combined short‐term wind power prediction based on long short‐term memory (LSTM) artificial neural network has been studied aiming at the non‐linearity and volatility of wind energy. Due to the large amount of historical data required to predict the wind power precisely, the ambient temperature and wind speed, direction, and power are selected as model input. The Complete Ensemble Empirical Mode Decomposition with Adaptive Noise has been introduced as data preprocessing to decompose wind power data and reduce the noise. And the Particle Swarm Optimization is conducted to optimize the LSTM network parameters. The combined prediction model with high accuracy for different sampling intervals has been verified by the wind farm data of Chongli Demonstration Project in Hebei Province. The results illustrate that the algorithm can effectively overcome the abnormal data influence and wind power volatility, thereby providing a theoretical reference for precise short‐term wind power prediction. [ABSTRACT FROM AUTHOR]

Aiming at the shortcomings of feature extraction and fault identification in fault diagnosis of wind power converters, a novel method for open circuit fault diagnosis of wind power converters based on variational mode decomposition (VMD) energy entropy (EE) and time domain feature analysis (TDFA) is proposed. Primarily, the three‐phase output current at the grid side of the wind power converter is collected as the original signal, and the VMD is used to decompose the original signal into a series of intrinsic mode functions (IMF). To reduce noise interference as much as possible, the Pearson correlation coefficient between each mode component and the original signal under different fault states is analyzed, and the IMF component containing the major failure features is selected to calculate the energy entropy of each component; afterward, according to the Pearson correlation coefficient results, the modal components of the first layer are selected for time domain feature analysis; finally, the feature matrix that combines energy entropy and time domain feature analysis is inputted into the long short‐term memory neural network for training and fault identification. The simulation and experimental results show that the open circuit fault diagnosis method proposed in this paper has high accuracy and robustness. [ABSTRACT FROM AUTHOR]

A novel multi-objective robust optimization model of an integrated energy system with hydrogen storage (HIES) considering source–load uncertainty is proposed to promote the low-carbon economy operation of the integrated energy system of a park. Firstly, the lowest total system cost and carbon emissions are selected as the multi-objective optimization functions. The Pareto front solution set of the objective function is applied by compromise planning, and the optimal solution among them is obtained by the maximum–minimum fuzzy method. Furthermore, the robust optimization (RO) approach is introduced to cope with the source–load uncertainty effectively. Finally, it is demonstrated that the illustrated HIES can significantly reduce the total system cost, carbon emissions, and abandoned wind and solar power. Meanwhile, the effectiveness of the proposed model and solution method is verified by analyzing the influence of multi-objective solutions and a robust coefficient on the Chongli Demonstration Project in Hebei Province. [ABSTRACT FROM AUTHOR]

In order to obtain better dynamic response and steady-state accuracy of permanent magnet synchronous linear motor (PMSLM), a hyperlocal model-free position control (LOMFC) method with load disturbance observer was designed to solve the problems of poor control accuracy and stability of traditional PI control methods. The second order hyperlocal model is used to integrate the position controller and the velocity controller to simplify the control structure and optimize the PI control. The double closed-loop model-free position control (MFPC) and triple closed-loop PI control systems were built, and the simulation and experimental comparison of sudden loading and unloading and steady-state operation were carried out respectively. The comparative experiment shows the superiority of this method. [ABSTRACT FROM AUTHOR]

In most of the piezoelectric stacked motors studied, the stator usually adopts two compound modes to drive the rotor to do step motion. This design method not only improves the utilization rate of the stator but also improves the torque output to a certain extent and increases the output displacement. In this study, a new type of multi-degree of freedom piezoelectric actuator is proposed for the utilization of a stator. The actuator realizes three compound vibration modes of bending-longitudinal-bending on a single stator, which changes the two compound modes of longitudinal bending and also changes the single motion mode of the stepper motor along a straight line. The rotor is set as a ball to drive it to rotate. The designed motor presents a different driving signal under which the rotor will no longer be accompanied by a return displacement. The finite element method is used to complete the design analysis, and the experimental analysis of the designed motor is carried out after the prototype is made. The multi-degree-of-freedom piezoelectric actuator can achieve a speed of 8.56 mm/c and a driving load of 1200 g at a voltage of 400 v and a working frequency of 42.7 kHz. [ABSTRACT FROM AUTHOR]

The Deflectable double-stator Switched Reluctance Generator (DSRG) has the advantages of simple structure, small volume and multi-dimensional operation. The DSRG and propeller are combined into the application of underwater power generation. With the help of the deflect ability of the generator, the efficiency is improved. Due to the uncertainty of ocean current direction and the structure of switched reluctance generator, the torque ripple is one of the important factors damaging the underwater generator. In order to effectively suppress the influence of torque ripple caused by generator operation, a method of adding pole shoes on the pole side of outer stator is proposed, so as to reduce the torque ripple. The propulsion structure running at different deflection angles is simulated. The torque and speed obtained before and after pole shoe optimization are input into the propeller model. The pressure and speed characteristics of the corresponding blade structure are simulated to verify the effect of optimization and the effectiveness of the power generation system. [ABSTRACT FROM AUTHOR]

Compared with traditional wired power transmission, wireless power transfer(WPT) has fully exhibited its key advantages of better safety and convenience, stronger reliability and electrical isolation, and less maintenance. Although the phase‐shift modulation strategy has been widely used in various WPT applications, it has certain limitations in terms of high‐frequency hard‐switching, which increases the power loss of the WPT system during voltage regulation. To achieve efficient operation over a wide range of load power, this paper proposes a dual‐frequency modulation strategy for the WPT system. The advantages of the dual‐frequency modulation strategy are the simple modulation logic and the lower switching loss. It maintains the optimal load impedance during constant voltage output and improves the overall efficiency of the system. For validation, we designed the control circuit and wrote the control program and built the experimental prototype of the WPT system to carry out the phase‐shift modulation experiment and the dual‐frequency modulation experiment, respectively. The experimental results show that the soft switching range and efficiency of the WPT system under the dual‐frequency modulation strategy are better. At the rated output power, the efficiency of the WPT system under dual‐frequency modulation strategy is 89.75%. The feasibility of the dual‐frequency modulation strategy has been confirmed. [ABSTRACT FROM AUTHOR]

A phase-shifted full-bridge (PSFB) converter is widely used in various applications due to its soft-switching characteristics. However, one of the recognized shortcomings of the PSFB converter is that it cannot simultaneously have a wide soft switching range and a small secondary-side duty cycle loss. The shortcoming hinders the high frequency and high efficiency of the converter. In this article, the change of the energy demand of the converter on the external series inductor with input voltage and load is analyzed. On this basis, a variable saturation inductor with controllable energy is proposed to meet the energy demand and solve the problem of core heating. The controllable change characteristics of the inductor energy are studied directly instead of the controllable change of the inductance value. By adjusting the inductor energy, the PSFB can not only achieve soft switching under light loads, but also reduce duty cycle loss under heavy loads. Theoretical analysis and experimental verification are carried out on the soft switching and duty cycle loss of the converter. Since the transformer ratio can be increased due to thesmaller duty cycle loss. The efficiency of the converter can be further improved. [ABSTRACT FROM AUTHOR]

A secondary-side semiactive three-phase interleaved (SS-SA3PI) resonant converter employing a multimode modulation scheme for fast EV charger applications is proposed. A multimode modulation scheme is used to widen the output voltage range without dynamic switching problems. By using secondary-side semiactive control, the resonant converter does not need to operate in the fs < fr state to achieve boost operation. The minimum switching frequency of the converter is equal to the resonant frequency, which reduces the size of the magnetic components. Thus, the power density of the converter is improved. Compared with the traditional 3-phase interleaved LLC converter controlled by PFM, this converter widens the output voltage range without adding any circuit components. This article introduces the control mode, working principle and characteristics of the proposed converter in detail. A 10 kW experimental prototype is built to realize the output voltage of 100–1000V, which verifies the feasibility and effectiveness of the scheme. [ABSTRACT FROM AUTHOR]

DC active power filter (DC-APF) can effectively suppress the bus voltage ripple of DC microgrid. In order to solve the problem that DC-APF can not work normally due to the failure of switching devices, a fault-tolerant DC-APF topology based on H-bridge converter was proposed, which could ensure the power quality management function of DC-APF after the device failure by using the topology reconstruction of non fault devices. Aiming at the problem that the topological structure is changed before and after the fault which causes the control parameters to be uncertain, a variable universe adaptive fuzzy PI control was proposed to track and control the compensation current effectively in DC-APF fault-tolerant mode. A DC microgrid system model with fault-tolerant DC-APF was built in Matlab/Simulink simulation environment. The simulation results show that the proposed DC-APF has good compensation performance for DC bus voltage ripple before and after the device failure, and the proposed variable universe adaptive fuzzy PI control has a good characteristic of real-time tuning controller parameters. [ABSTRACT FROM AUTHOR]

High step-up dc–dc converters are widely used in new energy applications such as photovoltaic cell, fuel cell, dc microgrid, etc. Active switched-inductor (ASL) converter has simple operation and low stress on switches. To further increase the voltage gain, some SC (switched-capacitor)/ASL step-up converters have been proposed recently. However, these SC/ASL step-up converters have voltage oscillation on switches, which leads to the voltage stress on switches is higher than the theoretical value. In this article, a novel high step-up SC/ASL converter is proposed. Compared with other SC/ASL step-up converters, the proposed converter has lower voltage stress on the switches, output diodes, and output filter capacitors, and the efficiency is higher. In addition, the proposed converter can achieve self-voltage balancing on switches. This article analyzes the proposed converter from operation principle, continuous conduction mode (CCM) analysis, CCM operation with unbalanced inductors, input current ripple analysis, discontinuous conduction mode and boundary conduction mode analysis, switches self-voltage balancing characteristic, voltage stress, current stress, comparison analysis, and design considerations. Finally, a 200 W, 25–45 V/380 V, 50 kHz experimental prototype has been established in the laboratory to evaluate the proposed converter, which reached a peak efficiency of 97.3%. [ABSTRACT FROM AUTHOR]

Summary: With the rapid development of power electronics technology, modular series‐parallel structures have attracted more and more attention due to high reliability and good redundancy. Especially in the occasion of high input voltage and low output voltage, the input‐series output‐parallel (ISOP) DC–DC converter is applied to reduce the stress of the device. Although this modular approach has many advantages, there is a problem of unbalanced voltage and current caused by component parameter errors in each module. Therefore, this paper proposes an inverse droop control equalization method based on coefficient adaptation. This method can not only keep the input voltage sharing (IVS) of the modules among the ISOP system but also solve the problem of the deviation of the traditional inverse droop control output voltage from the reference value, which increases the dynamic response of the system. This article first introduces the principle and control logic of the method and builds a three‐way module ISOP circuit. The experiment verifies the input voltage equalization effect and dynamic performance of the control method on the ISOP system under various working conditions. [ABSTRACT FROM AUTHOR]

In this paper, a mechanical model of the deflection dual-stator switched reluctance generator (DDSRG) is developed, and the advantages of the dual-stator structure for the deflecting motion are analyzed. Secondly, the spatio-temporal and spatial distribution characteristics of the inhomogeneous electromagnetic force are derived analytically and further verified by fast Fourier transform (FFT).Thirdly, the spatial and temporal distributions of electromagnetic forces of DDSRG are calculated based on finite element software, and the distributions of electromagnetic forces under different motion states are analyzed. By combining the analysis of modal analysis and harmonic response analysis, the free mode and vibration response acceleration variation laws of the internal and external stator are determined. The results show that the order of electromagnetic forces on the stator at rated speed is mainly 8 times the fundamental frequency, and the modal vibration order is more violent in the order of 2–7. Finally, the experimental platform of DDSRG is built, and the vibration characteristics are tested to verify the validity and accuracy of the proposed simulation results. [ABSTRACT FROM AUTHOR]

Switched reluctance generator is widely used in the field of wind power generation. The efficiency of generators was usually related to the deviation angle. Compared with the single stator type switched reluctance motor, these dual-stator type switched reluctance motor models have the advantages of high accuracy, fast response and small size. An optimization method based on fuzzy algorithm and parameter scanning is proposed to improve the low speed performance of high efficiency generator. Taking the maximum output power, system efficiency and torque smoothing coefficient of DDSRG as the optimization goals, the effects of the turn-on angle, turn-off angle and reference current on the optimization goal are analyzed. The multi-objective optimization function is constructed, and the optimal combination value is obtained. The experiment proved that the parameter-controlled multi-objective optimization method could effectively improve the comprehensive performance of DDSRG in low-speed operation state. [ABSTRACT FROM AUTHOR]

With the development of clean technology, inefficient motors that have been used for many years and the recyclable motor with damaged components are facing phase-out and scrap, leaving a large amount of waste resources and serious environmental pollution problems to be solved urgently. The purpose of this paper is to research the remanufacturing technology of obsolete permanent magnet synchronous motor (PMSM) and explore its future development prospects. In this paper, the PMSM is explored through theoretical analysis and finite element simulation, constructing the evaluation system of the remanufacturing of PMSM, and analyze the key problems of the remanufacturing scheme and design of PMSM. Secondly, the finite element model of the damaged PMSM is restored, by combining theory and magnetic thermal coupling simulation, the temperature of the motor is analyzed, and the data comparison of the finite element simulation is carried out with the experimental results, verifying the feasibility of remanufacturing of PMSM. On this basis, a water cooling structure is added to protect the stator winding insulation from high temperature damage and prevent the permanent magnet from demagnetizing due to high temperature., ensure the reliability of the motor under long-term operation, which prolongs the life of the motor, indirectly reduces the consumption of the motor manufacturing industry, reduces pollutants, saves energy and enterprise production costs, and promotes the sound development of motor in manufacturing industry. [ABSTRACT FROM AUTHOR]

To improve the control performance and dynamic response of the permanent magnet linear synchronous motor (PMLSM), a new sensorless control strategy of the PMLSM with the ultra-local model velocity control system is designed in this paper. Firstly, a model-free speed controller (MFSC) is constructed based on the principle of the ultra-local model. Meanwhile, based on the traditional sliding-mode observer (SMO), the back-electromotive force (BEMF) in the SMO is optimized by the model reference adaptive system (MRAS) to improve the observed speed information of the PMLSM. This control strategy improves the dynamic response ability and stability of the PMLSM system. Compared with the traditional motor control strategy, this design gets rid of the dependence on mechanical sensors, improves the dynamic response ability of the PMLSM, and reduces the velocity tracking error. The superiority of the control system is verified by simulation and experiment. Compared with the traditional dual proportional–integral (PI) control system and SMO, the new control strategy can improve the dynamic response performance of the PMLSM, enhance the stability, and track the speed information of the PMLSM with low error to reduce the chatter. [ABSTRACT FROM AUTHOR]

Aiming at the problem of poor tracking performance and chattering in track processing of biaxial permanent magnet linear synchronous motor (PMLSM), a cross-coupling control system based on model prediction was designed. First, according to the motion equation of PMLSM, an integrated controller is designed to predict the speed and current. In order to solve the problem that PMLSM is highly dependent on speed sensor, the actual motor model is designed, the adjustable model is designed by estimating the current model, and the model reference adaptive observer is designed. Second, cross-coupling control algorithm was added to the single axis control system of two PMLSM to improve the contour control accuracy and matching degree of the two motors. Finally, the experimental verification is carried out on the two-dimensional XY-axis experimental platform. Experimental results show that this method not only simplifies the structure of the control system, but also has better control effect than the traditional biaxial control structure. [ABSTRACT FROM AUTHOR]

In this article, a topology based on the single-phase full-bridge is proposed to decouple control of phase current in current source grid-connected inverters. The DC side of this current source inverter topology can operate with a common DC bus or independently, and the AC side can be independently integrated into the three-phase grid or operate in parallel. This topology needs only a simple control logic and phase information to achieve 3-phase current decoupling control, which can accommodate a wide range of voltage fluctuations. Then, dual-carrier driving and hybrid damping correction strategies are designed to achieve flexible combinatorial operation and eliminate the common-mode voltage. Meanwhile, the method is simple and easy to implement in practice. The effectiveness of the proposed algorithm is validated with experiments. [ABSTRACT FROM AUTHOR]

Temperature rise has always been one of the main researchfocusesof the motor. When the temperature is too high, it will have a serious impact on the stability and reliability of motor performance. Due to the special structure of electromagnetic piezoelectric hybrid drive motor (EPHDM), the loss and temperature distribution of electromagnetic drive part and piezoelectric drive part werestudied. By analyzing the operation principle of the motor, the loss of each part wasresearched. On this basis, the loss of the electromagnetic driving part and piezoelectric driving part werecomputed by using the coupling iterative calculation method. The temperature contour map of the motor wasanalyzed by simulation, and the temperature characteristics of each part of the motor werestudied. Finally, the experimental verification of the prototype, the reliability of the theoretical model, and simulation results wereproved. The results showed that the temperature distribution of the motor is reasonable, the winding temperature is relatively high, and the core temperature and piezoelectric stator temperature are relatively low. The analytical and experimental methods are provided for the further study of heat source optimization. [ABSTRACT FROM AUTHOR]

Piezoelectric-driven multi-degree-of-freedom motors can turn off self-lock, withstand high and low temperatures, are small in size and compact in structure, and can easily achieve miniaturization. However, they have a short life cycle and limited applications. In addition, high-intensity operation will result in a decrease in their stability. Electromagnetic-driven multi-degree-of-freedom motors, on the other hand, are simple and highly integrated, but they are large in volume and lack positioning accuracy. Therefore, combining the two drive modes can achieve complementary advantages, such as improving the motor's torque, accuracy, and output performance. Firstly, the structure of the hybrid drive motor is introduced and its working principle is analyzed. The motor can achieve single and hybrid drive control, which is beneficial to improving the performance of the motor. Secondly, the influence of magnetization mode, permanent magnet thickness, slot torque, and stator mode on the motor is analyzed. Thirdly, the structure of the motor is determined to be 6 poles and 15 slots, the thickness of the permanent magnet is 12 mm, and the radial magnetization mode is used. Finally, the mixed torque and speed of the motor in the multi-degree-of-freedom direction are tested by experiments, which indirectly verifies the rationality of the structure design. [ABSTRACT FROM AUTHOR]

Deflection switched reluctance motors (DSRM) are prone to chattering at low speeds, which always affects the output efficiency of the DSRM and the mechanical loss of the motor. Combining the characteristics of a traditional reluctance motor with the strong nonlinear and high coupling of the DSRM, a control system for a DSRM based on a flexible neural network (FNN) is proposed in this paper. Based on the better robustness and fault tolerance of fuzzy PI control, the given speed signal is adjusted and converted into a torque control signal. As a result, the FNN control module possesses the strong self-learning ability and adaptive adjustment ability necessary to obtain the control voltage signal. Through simulations and experiments, it was verified that the control system can run stably on DSRM and shows good dynamic performance and anti-interference ability. [ABSTRACT FROM AUTHOR]

A piezoelectric actuator (PEA) has the characteristics of high control precision and no electromagnetic interference. To improve the degree of freedom (DOF) to adapt to more working scenes, a piezoelectric–electromagnetic hybrid-driven two-DOF actuator is proposed. The PEA adopts the composite structure of the lever amplification mechanism and triangular amplification mechanism. The structure effectively amplifies the output displacement of the piezoelectric stack and increases the clamping force between the driving foot and the mover. The electromagnetic actuator (EMA) adopts a multi-stage fractional slot concentrated winding permanent magnet synchronous actuator, which can better match the characteristics of PEA. The structure and working principle of the actuator are introduced, the dynamic analysis is carried out, and the factors affecting the clamping force are obtained. At the same time, the air gap magnetic field is analyzed, and the structural size of the actuator is optimized. The experiment shows that the maximum driving speed can reach 348 mm/s, the load capacity is 3 kg, the optimal initial rotor angle is 49°, the maximum torque is 2.9 N·m and the maximum speed is 9 rad/s, which proves the stability and feasibility of the actuator. [ABSTRACT FROM AUTHOR]

In allusion to the phenomenon that the extended Kalman filter is easy to diverge in the mover position estimation of permanent magnet synchronous linear motor, a linear motor extended Kalman filter speed estimation method based on attenuation memory is designed. By setting the attenuation factor, α, the extended Kalman filter is introduced to increase the weight of the latest speed data and restrain the divergence of the filter, so as to achieve a better speed tracking effect. In the simulation experiment of the sensorless control of a linear motor, the AMEKF algorithm can significantly improve the speed estimation accuracy of standard EKF, and the speed estimation error is reduced by 0.75%. At the same time, it still maintains a good speed tracking effect and good dynamic performance under variable speed and different load conditions. [ABSTRACT FROM AUTHOR]

In an attempt to solve the problem of the many parameters of the traditional active disturbance rejection controller (ADRC) and to accurately estimate the mover position and speed required by a permanent magnet synchronous linear motor (PMLSM) system, an improved ADRC and a novel nonsingular fast terminal sliding mode observer (NFTSMO) are proposed. Firstly, the traditional first-order ADRC is simplified, the tracking differentiator (TD) module is removed, and the direct error is used to replace the nonlinear function in the extended state observer (ESO) and nonlinear state error feedback (NLSEF) module. Based on the traditional NFTSMO, the smooth back electromotive force (EMF) is obtained by adding the TD to reduce the phase delay caused by the low-pass filter in the traditional sliding mode observer (SMO), and the actuator position and speed information are modulated from the observed back EMF based on the principle of a phase-locked loop (PLL). Simulation and experiments show that this method not only simplifies the system structure of PMLSM but also optimizes many parameters in ADRC while retaining the original excellent performance. Compared with the traditional NFTSMO, the improved NFTSMO enhances the observation accuracy, reduces the chattering phenomenon of the system, and improves the robustness of the system. [ABSTRACT FROM AUTHOR]

To improve the tracking capability and sensorless estimation accuracy of a permanent magnet linear synchronous motor (PMLSM) control system, a sensorless control system based on a continuous terminal sliding mode controller (CT-SMC) and fuzzy super-twisted sliding mode observer (F-ST-SMO) was designed. Compared with a conventional slide mode control, CT-SMC can reach the equilibrium point in limited time to ensure the continuity of control and achieve fast tracking of reference speed. Based on the PMLSM design of F-ST-SMO, a super-twisted sliding mode algorithm is used to replace the traditional first order sliding mode algorithm. Meanwhile, fuzzy rules are introduced to adjust the sliding mode gain adaptively, which replaces the fixed gain of traditional SMO and reduces chattering of the system. Finally, the effectiveness and superiority of the designed control system are proven by simulation and experiment. [ABSTRACT FROM AUTHOR]

Laser detection technology has manypromising applications in the field of motor speed and position measurement. Accurate and fast measurement of position information of spherical rotor is very important for motor control. In this paper, we propose a method for non-contact measurement of the angular velocity of a multi-DOF spherical motor using the Doppler effect of the laser, and further obtain the position information of the motor rotor. The horizontal laser beam from the laser generator is divided into a reference beam I and a measurement beam II through a beam splitter, and the measurement beam II reflects and undergoes Doppler effect after irradiating the rotating motor. The two beams pass through the photoelectric conversion module to obtain the corresponding frequency difference signals to derive the angular velocity and position information of the motor rotor. The correctness of the method is verified experimentally. The results show that the coordinate error of Z and Y axes is less than 2 mm, thatthe error of Z-axes is less than 0.2 mm, and that the method can better measure the spherical rotor position information of the motor. [ABSTRACT FROM AUTHOR]

In this paper, an improved rotor structure with cross-shaped flux-barriers was proposed to improve the torque output capacity and reduce the torque ripple of the synchronous reluctance motor (SynRM). Firstly, an improved rotor structure of synchronous reluctance motor with cross-shaped flux-barriers, which can be described by two main parameters, is presented. Second, the improved motor is qualitatively analyzed by using magnetic equivalent circuit (MEC), and then the effects of the main parameters of the improved flux-barriers on the distribution of air-gap flux density, average torque, and torque ripple were analyzed by using the finite element method. Based on the above analysis, the rotor structure parameters of the proposed cross-shaped flux-barriers were obtained, and the performance was compared with that of the initial motor. The results show that the proposed rotor structure with cross-shaped flux-barriers can significantly reduce the torque ripple and increase the average torque. [ABSTRACT FROM AUTHOR]

LLC half-bridge converters have been extensively studied in low power industrial applications. However, the phase shift angle between the voltage and current of the LLC resonant network makes the converter have power circulation, that is, backflow power. The increase of the backflow power will increase the converter conduction loss, which restricts the improvement of the converter efficiency. The existing literature often improves the backflow power from the control aspect, which greatly increases the control complexity. To solve this problem, this article proposes an LLC half-bridge resonant converter analysis method that takes the backflow power into account. Based on the analysis of operating mode and ac equivalent model of the converter, backflow power is indirectly characterized by the phase-shift angle of the resonant network voltage and current. Based on this, this article analyzes the internal relationship between resonant parameters and backflow power to reduce backflow power by optimizing resonant parameters. Under the setting operating conditions, converter can achieve zero voltage switching (ZVS) switching, voltage gain conditions, and minimum backflow power. Compared with the existing methods, the proposed optimization method avoids additional auxiliary circuits and control complexity, improves the stability of the circuit. Experimental results verify the accuracy and feasibility of the theoretical analysis. [ABSTRACT FROM AUTHOR]

With the wide application of clean energy, the requirements of this vertical axis wind turbine are higher and higher. A new diagonal spiral blade vertical axis wind turbine is designed and studied. The shape of the new type of wind turbine blade is designed based on the diagonal spiral structure that is common in life, considering the situation of different pitch angles and constructing 11 kinds of prototype machine. In‐depth analysis of the aerodynamic performance of these new wind turbines through simulation calculations shows that the prototype with a pitch angle of 110° has the best aerodynamic performance. When the tip speed ratio is 0.4, the maximum wind energy utilization rate can reach 0.29. Besides, the model of this wind turbine is constructed by 3D printing, which is tested, and the performance of the models is compared with that of the traditional S‐type wind turbine in a real environment. There rationality and superiority of the design of the new diagonal spiral blade vertical axis wind turbine are proved, and this apply background of this new diagonal spiral blade wind turbine is demonstrated by comparison. This article also analyzes the wake of the wind turbine and makes reasonable planning of the arrangement spacing that the wake effect has the least effect on the downstream wind turbine, which can increase the power generation efficiency of the group arrangement of turbines. [ABSTRACT FROM AUTHOR]

When the dual-axis linear motor is processing components, its accuracy will be affected by the uncertainty and nonlinearity of the system, and the complexity of the processing curve trajectory. The goal is to improve the machining accuracy and response speed of the XY dual-axis permanent magnet synchronous linear motor two-dimensional platform, improve the anti-interference ability, and reduce the contour error. This paper proposes a coupled control method based on dual closed-loop single-axis high-order terminal sliding mode position control (TSMC). First, an improved mathematical model of equivalent contour error is established. Combine the coordinated controller to get the coupling link. Then, to accelerate error convergence and suppress chattering, a high-order terminal sliding mode controller is designed. The single-axis current controller is designed using high-order sliding mode algorithms. Simulations and experiments show the effectiveness and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

The multidimensional motion ultrasonic motor with a single spherical stator is studied in this paper. It has the characteristics of miniaturization and can be used in precision motion applications. By bonding six identical pieces of piezoelectric ceramic onto the stator and applying the voltage signal of high frequency, the deformation of the inverse piezoelectric effect is used to excite the stator yaw vibration mode. The orthogonal superposition of the modes of the spherical stator on the driving foot produces elliptical trajectory around X, Y, and Z directions by different excitation methods. According to the yaw vibration mode of the spherical stator, 12 driving feet are designed to drive the rotation of the spherical rotor. The structure and mechanical characteristics of the motor are simulated by using simulation software, and the transient response of the stator driving foot was obtained, which proved its feasibility. Finally, the output performance of the motor in actual operation is given through experiments, which provides a new reference scheme in the field of precise multi-degree-of-freedom motion. At a voltage of 100 V and a frequency of 26.7 kHz, the prototype has a no-load speed of 73, 70, and 114 rpm around X, Y, and Z axes, respectively. [ABSTRACT FROM AUTHOR]

In view of the fact that the transmission mode of the multi-DOF motor hinders its further development, the gas bearing is applied to the multi-DOF motor to form a new structure of the multi-DOF motor with air-floation (AMM). AMM not only improves the motor's motion characteristics and transmission performance, but also basically does not cause environmental pollution. AMM uses porous static pressure gas bearing as the support structure, and completes the multi-DOF movement by controlling the energizing strategy of the coils. This paper introduces the structure of AMM, analyzes the basic working principle of AMM, and solves the air gap magnetic field; the kinematics model of the motor is established, the motion of the motor is controlled with the help of virtual simulation software, and the motion trajectory of the motor is obtained through the marked points of the output shaft. Finally, the AMM was verified by experiments, the error of experiment and simulation was controlled at 5%, and the kinematics characteristics of the motor met the design requirements. The research results provide a new idea for the development of multi-DOF motor. [ABSTRACT FROM AUTHOR]

A bipolar DC microgrid shows good performance since it improves the efficiency and system's reliability. To transmit power to the load, several DC-DC converters are required by the conventional bipolar DC microgrid, which results into large weight, volume, and high cost. To integrate bipolar DC microgrid with the photovoltaic (PV) module, a novel bipolar output converter is proposed in this paper. This converter possesses very simple circuit configuration and can achieve a high step-up voltage gain by adopting active-switched-inductor (ASL) network; meanwhile, bipolar output voltage is between positive line (P), negative line (N), and common ground (O), which can offer three voltage classes (Vdc, +0.5 Vdc and -0.5 Vdc). To verify the precision of the analysis of the proposed converter, a prototype has been designed and experiments are performed in the lab. [ABSTRACT FROM AUTHOR]

Nautilus vertical axis wind turbine is a new breed which is being designed and developed through bionics and geometry, this kind of wind turbine is not only novel in appearance, and stable in structure, but also has excellent aerodynamic performance. Based on this type of wind turbine, combined with its structural characteristics, this paper designed 20 prototypes by continuously adjusting the structural parameters of the spiral blades. The performance of these prototypes is compared by simulation, the optimal structure of this kind of wind turbine is selected. This optimized wind turbine has a strong ability to collect wind energy and can obtain higher wind energy utilization in a wider range of wind speed, the maximum wind energy utilization rate reaches 32.842%. Then the wake characteristics are analysed, the reasonable arrangement is designed. This paper also built an equal scale reduced version of the real object using a 3D printer, and assembles it with a small disc type electric machine to construct a vertical axis wind power generation apparatus. Finally, experiments are conducted in a real environment to analyse the rotational speed and voltage waveform of this apparatus under different operating conditions experimentally. [ABSTRACT FROM AUTHOR]

In this paper, a piezoelectric actuator with three symmetrical distributions is designed. Piezoelectric ceramics are polarized in a set manner. The excitation voltage signals of the same amplitude and different phases are applied to the actuator, and an elliptical trajectory is generated on the driving foot to drive the slide rail to move. Its driving principle is different from that of previous drivers of this type. For example, when moving in a certain direction, the horizontal displacement is formed by a mixture of the longitudinal vibration of one sub-actuator and the bending vibration of two sub-actuators, while the vertical displacement is generated by the bending vibration of the actuator. Through the close cooperation of the three sub-actuators, the output efficiency is greatly improved. The actuator is suitable for small high-precision control. First, the overall structure and working principle of the piezoelectric actuator are briefly introduced. Then, through the finite element analysis, the working mode with output performance and the motion track on the driving foot are analyzed. Finally, the output performance of the actuator is analyzed. When the voltage frequency is 200 Hz and the amplitude is 200 V, the maximum output speed is 5.1 mm/s and the maximum load of about 1.2 kg can be applied, which verifies that the actuator has good driving ability. [ABSTRACT FROM AUTHOR]

In view of the uncertainty and volatility of wind power generation and the inability to provide stable and continuous power, this paper proposes a hydrogen storage wind-gas complementary power generation system, using Matlab/Simulink to simulate and model wind generators and gas turbines. Considering the economy and power supply reliability of the wind-gas complementary power generation system, and taking the economic and environmental cost of the system as the objective function, the capacity optimization model of the wind-gas complementary power generation system is established. The brain storming algorithm (BSO) is used to solve the optimization problem, and the BSO algorithm is used to optimize the BP neural network, which improves the accuracy of the BP neural network for load forecasting. Finally, a simulation is carried out with load data in a certain area, and the simulation verification verifies that BSO-BP can improve the accuracy of load forecasting and reduce the error of load forecasting. Multi-objective optimization of system economic cost and environmental cost through BSO algorithm can make the system cost reach the most reasonable level. Through the analysis of the calculation examples, it is verified that gas-fired power generation can effectively alleviate the volatility of wind power generation, showing the role and advantages of energy complementary power generation. Therefore, the wind-gas complementary system can effectively increase energy utilization and reduce wind curtailment. [ABSTRACT FROM AUTHOR]

In this paper, a deflection type dual‐stator switched reluctance wind power generator is proposed. This kind of generator can effectively improve the power generation efficiency and response speed of the generator with development potential. The generator consists of an external generator and an internal generator, which can be coordinated to improve the efficiency of the generator. In this paper, with the goal of reducing the loss of the generator core, Taguchi algorithm is used to screen out the parameter variables that has a great impact on the loss of the generator core. Based on the method of central composite design (CCD), the experimental sample data set is constructed and the rationality of the model is evaluated by analysis of variance and the optimal parameters of the generator are determined. The test results of the prototype verify the correctness of design, core loss calculation and optimization scheme. [ABSTRACT FROM AUTHOR]

For the intermittent nature of renewable resources (such as wind and solar), smooth power fluctuations are required before the energy conversion system can be injected into the grid. The battery system is a typical smoothing control method for photovoltaic power. The long-term overcharge and overdischarge make the battery energy storage scheme unattractive. In this paper, the output power fluctuation of the photovoltaic power generation system is smoothed based on the unscented Kalman filter (UKF) method combined with the fuel cell operating characteristics. This coordination method affects the UKF situation through the feedback of state of charge (SOC) and the power of the battery system. Not only can it better meet the load characteristics, but it can also make the SOC automatically correct the battery system to prevent overcharge and overdischarge. The meteorological load data was used to verify the superiority of the method. [ABSTRACT FROM AUTHOR]

A novel spherical multi-degree-of-freedom ultrasonic motor is designed, which can achieve three-degree-of-freedom motion through the cooperative drive of three built-in traveling wave stators. The novel ultrasonic motor has the characteristics of compact structure and high power density. Additionally, in order to solve the problem of impedance mismatch between the ultrasonic motor and the driving power supply, a semi-analytical method of impedance matching based on parallel resonance is proposed according to the impedance characteristics of ultrasonic motor. Through the combination of theoretical derivation and finite element simulation, the ultrasonic motor impedance matching on the impedance circle is analyzed. By this method, the optimum matching inductor of the motor is determined. After matching, the motor obtains a larger vibration amplitude and higher transmission efficiency. Finally, the reliability of the method is verified by simulation and experiment, which provides a reference for further improving the motor performance. [ABSTRACT FROM AUTHOR]

The hydrogen energy system based on the multi-energy complementary of renewable energy can improve the consumption of renewable energy, reduce the adverse impact on the power grid system, and has the characteristics of green, low carbon, sustainable, etc., which is currently a global research hotspot. Based on the basic principles of hydrogen production technology, this paper introduces the current hydrogen energy system topology, and summarizes the technical advantages of renewable energy complementary hydrogen production and the complementary system energy coordination forms. The problems that have been solved or reached consensus are summarized, and the current status of hydrogen energy system research at home and abroad is introduced in detail. On this basis, the key technologies of multi-energy complementation of hydrogen energy system are elaborated, especially in-depth research and discussion on coordinated control strategies, energy storage and capacity allocation, energy management, and electrolysis water hydrogen production technology. The development trend of the multi-energy complementary system and the hydrogen energy industry chain is also presented, which provides a reference for the development of hydrogen production technology and hydrogen energy utilization of the renewable energy complementary system. [ABSTRACT FROM AUTHOR]

Summary: For uncontrolled power caused by wind conditions and external environmental conditions, battery packs are a type of energy storage system commonly used in wind power generation systems to smooth power fluctuations. The traditional cogeneration scheduling method not only relies on thermal energy storage devices but also frequently starts micro gas turbines, which affects the service life of the equipment. This paper proposes a dispatching method for a wind power system based on cogeneration. The wind power generation system adds an electrolytic cell (EL) and a proton exchange membrane fuel cell (PEMFC) to absorb long‐term fluctuations, and the battery absorbs short‐term fluctuations, and relies on the extended Kalman particle filter algorithm for scheduling. ELs and PEMFCs can not only balance fluctuations from wind and thermal energy systems, eliminate the need for thermal energy storage devices, but also correct the start‐stop frequency of micro gas turbines. The algorithm will also be applied to the state of charge estimation of the battery to improve the accuracy of the estimation. Simulation analysis shows that the grid‐connected active power fluctuation decreases from ±500 to ±200 kW, and the system's correction effect is analyzed to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Feature Application: A novel strategy is proposed to address open-circuit fault diagnosis of grid side full-scale power converters of wind turbines. The power converter is a significant device in a wind power system. The wind turbine will be shut down and off grid immediately with the occurrence of the insulated gate bipolar transistor (IGBT) module open-circuit fault of the power converter, which will seriously impact the stability of grid and even threaten personal safety. However, in the existing diagnosis strategies for the power converter there are few single and double IGBT module open-circuit fault diagnosis methods producing negative results, including erroneous judgment, omissive judgment and low accuracy. In this paper, a novel method to diagnose the single and double IGBT modules open-circuit faults of the permanent magnet synchronous generator (PMSG) wind turbine grid-side converter (GSC) is proposed: Primarily, by collecting the three-phase current varying with a wind speed of 22 states, including a normal state and 21 failure states of PMSG wind turbine GSC as the original signal data. Afterward, the original signal data are decomposed by using variational mode decomposition (VMD) to obtain the mode coefficient series, which are analyzed by the proposed method base on fault trend feature for extracting the trend feature vectors. Finally, the trend feature vectors are utilized as the input of the deep belief network (DBN) for decision-making and obtaining the classification results. The simulation and experimental results show that the proposed method can diagnose the single and double IGBT modules open-circuit faults of GSC, and the accuracy is higher than the benchmark models. [ABSTRACT FROM AUTHOR]

Solar energy is a kind of pollution-free and inexhaustible energy. Photovoltaic power generation is an effective way to use solar energy. The output characteristics of photovoltaic cell are easily affected by illumination intensity, temperature and other factors, so the maximum power point tracking of photovoltaic power generation can effectively improve the power of the system. Firstly, a photovoltaic cell model is established to analyze the non-linear electrical characteristics under different solar intensity and working temperature. Secondly, the MPPT control strategies based on perturbance observation method and conductance increment-fuzzy control method are respectively studied, and the system simulation model including photovoltaic module, boost circuit, MPPT control module, PWM module and so on is built in MATLAB/Simulink. Finally, the operation effects of different MPPT control strategies are analyzed and compared by means of experiments in different scenarios. The conductance increment-fuzzy control method improves the power generation efficiency, reduces the system oscillation and enhances the working stability. [ABSTRACT FROM AUTHOR]

The hydrogen production technology by wind power is an effective mean to improve the utilization of wind energy and alleviate the problem of wind power curtailment. First, the basic principles and technical characteristics of the hydrogen production technology by wind power are briefly introduced. Then the history of the hydrogen production technology is reviewed, and on this basis, the hydrogen production system by wind power is elaborated in detail. In addition, the prospect of the application of the hydrogen production technology by wind power is analyzed and discussed. In the end, the key technology of the hydrogen production by wind power and the problems to be solved are comprehensively reviewed. The development of hydrogen production technology by wind power is analyzed from many aspects, which provides reference for future development of hydrogen production technology by wind power. [ABSTRACT FROM AUTHOR]