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A tomato automatic detection method based on an improved YOLOv8s model is proposed to address the low automation level in tomato harvesting in agriculture. The proposed method provides technical support for the automatic harvesting and classification of tomatoes in agricultural production activities. The proposed method has three key components. Firstly, the depthwise separable convolution (DSConv) technique replaces the ordinary convolution, which reduces the computational complexity by generating a large number of feature maps with a small amount of calculation. Secondly, the dual-path attention gate module (DPAG) is designed to improve the model’s detection precision in complex environments by enhancing the network’s ability to distinguish between tomatoes and the background. Thirdly, the feature enhancement module (FEM) is added to highlight the target details, prevent the loss of effective features, and improve detection precision. We built, trained, and tested the tomato dataset, which included 3098 images and 3 classes. The proposed algorithm’s performance was evaluated by comparison with the SSD, faster R-CNN, YOLOv4, YOLOv5, and YOLOv7 algorithms. Precision, recall rate, and mAP (mean average precision) were used for evaluation. The test results show that the improved YOLOv8s network has a lower loss and 93.4% mAP on this dataset. This improvement is a 1.5% increase compared to before the improvement. The precision increased by 2%, and the recall rate increased by 0.8%. Moreover, the proposed algorithm significantly reduced the model size from 22 M to 16 M, while achieving a detection speed of 138.8 FPS, which satisfies the real-time detection requirement. The proposed method strikes a balance between model size and detection precision, enabling it to meet agriculture’s tomato detection requirements. The research model in this paper will provide technical support for a tomato picking robot to ensure the fast and accurate operation of the picking robot.

Current responses based self-sensing control estimates rotor position by detecting magnetic saliency of a machine. However, the estimation error can be resulted from several nonideal factors, especially magnetic cross-saturation, as effects of these factors show up in current responses. This article applies image registration technique to improve the accuracy of a self-sensing estimation for model predictive control (MPC) interior permanent magnet synchronous machines (IPMSM) drives by minimizing impacts of nonideal factors on measured current responses. In commissioning process, two images are generated. The inverter voltage vectors in MPC excite current responses, represented by a set of vectors that generate a response image. Nonideal factors that result in estimation errors also deform the response image. A primitive image based on resolver output can be considered as a template. An image registration technique is investigated to register deformed images with corresponding primitive images, and transformations contain operations of rotation, scale, translation, and shear can be derived. During the drive, the deformed pixel points are online mapped to new pixel points by applying these operations. The current responses after transformation are less subject to nonideal factors. As a result, impacts of these deformation factors that contribute to estimation errors can be reduced. Finally, the application of image registration technique to the self-sensing estimation is verified on a 3.7-kW IPMSM drive.

Spike voltage generated during the turn‐off transient is one of the key threats to IGBT. When the traditional RCD snubber is applied in the five‐level active neutral point clamped (5L‐ANPC) inverter to clamp the spike voltage, a transient large current caused by the charging of the snubber capacitor will increase power losses and current stresses of IGBTs. This study proposes a LRCD snubber for the 5L‐ANPC inverter. It can effectively suppress the spike voltages and the transient large currents of IGBTs, thus reducing the power loss. For the 5L‐ANPC inverter, the traditional commutation method also poses a threat to IGBTs. Near the zero‐crossing point of the output voltage, the traditional commutation method will cause the IGBTs that operate at the carrier frequency to withstand three times of the rated voltage. This study proposes a safe commutation strategy based on the LRCD snubber. When the output voltage passes through zero‐crossing point, the proposed commutation strategy uses four transition switching states to avoid the breakdown of IGBTs induced by overvoltage. It can ensure that all the IGBTs operate in the safe operating area (SOA). Experimental results are presented to verify the validity of the proposed method.

To deal with the uncertain relationship between random variables and harmonic spectrum in existing random pulsewidth modulation (PWM), this article links the uniformly distributed random carrier sequence probabilistic parameters with harmonic distributed in the frequency domain, offers an approach to selecting a random carrier sequence. Based on random slope PWM, the formula for 3-dB bandwidth of harmonic power spectrum is deduced. Then, some useful conclusions are also drawn under random carrier sequence obeying uniform distribution. The 3-dB bandwidth formula leads to a method of selecting the main probability statistical parameters. The method has laid a theoretical foundation for the design and selection of random variables in random PWM, provided a scientific reference for the study of random PWM technology, which is used to reduce electromagnetic interference and mechanical vibration.

For the five-level active neutral point clamped (5L-ANPC) converter, the coupling problem between the DC-link capacitor voltages and flying-capacitor (FC) voltages will increase the capacitor voltage fluctuations. The capacitor voltage fluctuations and current harmonics of the space vector pulse width modulation (SVPWM) are less than those of the sinusoidal pulse width modulation (SPWM), because the maximum linear modulation index of the SVPWM is higher than that of the SPWM. However, SVPWM has difficulty in realizing the decoupling control of the capacitor voltages, and the computation complexity of SVPWM is much higher than that of SPWM. This paper proposes a third harmonic injection modulation algorithm for the 5L-ANPC converter. The proposed algorithm injects the third harmonic into the modulation waves of SPWM, which makes the maximum linear modulation index of SPWM the same as that of SVPWM, to reduce the capacitor voltage fluctuations and current harmonics. The calculation of the third harmonic only requires a standard sorting algorithm and a simple linear operation; thus, it is easy to implement. Based on the third harmonic injection modulation algorithm, two variables are introduced to control the neutral point (NP) current and the FC current. And the two variables are used to feedforward compensate the modulation waves, realizing the decoupling control of the capacitor voltages. The proposed decoupling control method can further reduce the capacitor voltage fluctuations. Experimental results are presented to verify the validity of the proposed algorithm.

In this study, a short primary six-phase linear induction motor (LIM) operating in high-speed non-periodic transient conditions is used as an object of study. In consideration of the coupling terms related to the dynamic end effect, the motor model is simplified and the vector control equation is deduced. A vector control strategy for the real-time modification of slip-frequency and torque current is proposed for dynamic thrust compensation. On this basis, considering the problems of thrust decay caused by dynamic end effect and dc-link voltage drop, this study puts forward a field-weakening control method to keep thrust constant before its decrease in the field-weakening region. The method makes it possible for the LIM to overcome the thrust decay and the narrowing of voltage limits under the high-speed operating conditions. The simulation and experimental results show that the proposed control strategies are useful for optimising the thrust in the transient process thus to realise the high-speed operation of the motor.

This study investigates a short primary double-side six-phase linear induction motor (LIM) operating in non-periodic transient conditions. The main purpose is to solve the problems arising from the dynamic end effect. The equivalent circuit method is used for intensively studying the transient time-varying law of eddy current and excitation inductance, and the finite element method is adopted for verification. The calculation of eddy current loss leads to an expression of secondary equivalent resistance. Then, a mathematical model is established for the six-phase LIM involving the dynamic end effect. Furthermore, the matrix reconstruction method is adopted for the coupling of windings. Based on the time-varying characteristics of the model, an improved vector control method that can update the velocity-related correction coefficients through on-line calculation is proposed. During the transient process, the slip frequency and the torque current are modified in real-time to achieve the maximum output thrust of the motor. This approach can compensate for the thrust drop caused by the dynamic end effect, thereby improving the control precision. Simulations and experiments show that the related theory and the proposed control method are feasible and effective.

This study proposes a speed sensorless vector control strategy for the six-phase linear induction motor (SPLIM) based on the dual reduced-dimensional serial extended Kalman filters (DRDSEKFs). Firstly, the low-order mathematical model of SPLIM is obtained according to the equivalent transformation of primary voltage, current and flux components in the stationary coordinate system. Then, the state equation is derived and the speed estimation based on the five-dimensional extended Kalman filter (EKF) is realised. To reduce the computation cost and improve the accuracy of speed estimation, a DRDSEKFs algorithm is proposed, with one two-dimensional EKF and one three-dimensional EKF operating serially in every control period. As the real-time performance of the algorithm is guaranteed, it is possible to overcome the hysteretic nature of the traditional EKF and improve the dynamic estimation performance. Simulations and experiments show that the proposed sensorless control strategy is feasible and effective.

Aiming at the application of all-SiC power module in double-12-slot winding permanent magnet propulsion systems, the key characteristics of all-SiC power module, such as temperature rise and conversion efficiency, are compared and analyzed. Compared with similar Si IGBT power module, the overall efficiency of all-SiC power module is increased by about 1.5%, which is more in line with the application requirements of double-12-slot winding permanent magnet propulsion systems. The double-12-slot winding permanent magnet propulsion systems are introduced in detail, which includes basic composition, topology and control system architecture. The synchronous operation conditions of double power windings are analyzed. Under the conditions of the same driving pulse, the same line delay and the same switching characteristics, the pulse time difference of double power windings is less than 30 ns. Finally, the mean phase errors between windings with the same slot are measured within 0.1 degrees, and the phase consistency is high. Experiments on the speed regulation performance of the propulsion module in full speed range under no-load/load conditions are completed. The results show that the all-SiC power module has good load capacity. Load current synchronization can be better realized to avoid the pulse induced current between the same slot windings.

This Letter has proposed a synchronous control strategy of dual five-level converters based on the improved space vector pulse-width modulation (SVPWM). Firstly, the main topology of the neutral point clamped (NPC) five-level converter was introduced and its operational principle was analysed. Then, the space voltage vector diagram was offered. Considering the reduction of switching loss, the optimisation of the synthesis method of target voltage vectors and the addition of the neutral-point potential balancing algorithm can lead to an improved SVPWM strategy for the five-level converter. The analysis of the switching rules proves that the improved SVPWM has an advantage over the traditional three-segment SVPWM due to its fewer times of switching. On the basis of the improved SVPWM, a synchronous control method of dual single-phase five-level converters is proposed to carry out a real-time control of the dual five-level converters through the combinational-encoding transmission of output pulses. Thus, the synchronous control method can, to a great extent, solve the problems caused by the traditional dual five-level independent control method, such as high hardware cost, the complexity of control, and poor synchronous performance. Simulations and experiments show that the proposed synchronous control method is feasible and effective.

Since the carrier sequence is not reproducible in a period of the random carrier pulse width modulation (RCPWM) and a higher harmonic spectrum amplitude is likely to affect the quality of the power supply. In addition, electromagnetic interference (EMI) and mechanical vibration will appear. To solve these problems, this paper has proposed an optimal RCPWM based on a genetic algorithm (GA). In the optimal modulation, the range of the random carrier frequency is taken as a constraint and the reciprocal of the maximum harmonic spectrum amplitude is used as a fitness function to decrease the EMI and mechanical vibration caused by the harmonics concentrated at the carrier frequency and its multiples. Since the problems of the hardware make it difficult to use in practical engineering, this paper has presented a hardware system. Simulations and experiments show that the RCPWM is effective. Studies show that the harmonic spectrum is distributed more uniformly in the frequency domain and that there is no obvious peak in the wave spectra. The proposed method is of great value to research on RCPWM and integrated power systems (IPS).

The fundamental frequency of the 400Hz power supply system is 8 times 50 Hz one, so the line voltage drop becomes a severe problem that affects the output voltage quality of the medium frequency power supply system. In a power supply system with single power source and multiple loads, as different lines between loads and power source are different in length, series dynamic voltage restorers (DVR) are set at the loads side to keep loads voltage constant in this paper. By means of analyzing impedance of transmission line and the voltage drop on it, a capacity calculation model of dynamic voltage restorer under normal working conditions is found. The series dynamic voltage restorer based on proportional-resonant (PR) control is used to guarantee a satisfactory output quality of the system. Simulation and experiment results verify that the series dynamic voltage restorer based on PR control effectively solves the problems of source voltage perturbation and line voltage drop in the medium frequency power supply system.

Sampling points in one cycle of 400 Hz inverter are 8 times less than that of 50 Hz inverter, resulting in lower control accuracy and larger static error in 400 Hz power supply system. This paper set up a mathematical model for single-phase solid-static power supply system. The transformer leakage inductance and load can be regarded as uncertainties. A robust controller based on the principle of mixed sensitivity method is proposed to reduce the impact of the uncertainties on output voltage. Simulation and experimental results verify that the robust controller has a superior dynamic performance and robustness.

As aviation power supply is developing to be increasingly integrated, by sharing the same main circuit, AC and DC dual output can be achieved through the same power supply to greatly improve power integration and power density. However, transformation ratio and transformer leakage in AC conversion can cause voltage drop in DC output and thus fail to meet the rated voltage of aviation DC power. To solve this problem, this paper describes the working principles of AC and DC transformation sharing the same main circuit and its control strategies, elaborates the relationship between transformation ratio and Total Harmonic Distortion (THD) of AC output voltage through comprehensive analysis, and confirms the effects of switching frequency and leakage inductance of transformer on DC output through experiments before arriving at the conclusion that reducing the leakage inductance of transformer can balance both THD of AC output voltage and DC output voltage and thus achieve dual output in the same power supply.

The sampling points in one cycle of 400 Hz inverter is 8 times less than that of 50 Hz inverter, resulting in lower control accuracy and larger static error in 400 Hz power supply system. According to the characteristics of the 400 Hz inverter, this paper establishes a mathematical model for single-phase solid-static power supply system. The changes in line impedance and load can be considered as uncertainties. A robust controller based on the principle of μ analysis and synthesis is proposed to reduce the impact of the uncertainties on output voltage. Instead of utilizing traditional double-loop, this paper uses single-loop robust controller to realize the stability and robust performance of the whole system. Simulation and experimental results verify that the robust controller has a superior dynamic performance and robustness.

The short-circuit fault will affect the continuity and reliability of the DC system seriously, so it must be detected and isolated quickly. DC circuit breaker can be used to break the system fault circuit more effectively. However, different from the AC system, the DC current has no natural zero crossing. If the mechanical circuit breaker is used for short circuit fault protection, it will bring an arc, which will require total time few milliseconds or even larger for complete interruption. As a result, the DC system voltage will drop during this period. In this paper, a new scheme will make use of impendence source to design a new type of DC circuit breaker: T-source DC solid-state breaker, which can break the short circuit fault more quickly so as to improve the continuity and power quality of the system. The main topological structure is presented and mathematical model is derived through comprehensive analysis. The simulation and laboratory results are shown to verify the theoretical analysis.

The dual active bridge (DAB)-based isolated bidirectional converter has been used to realize bidirectional energy flow while offering needed isolation between the primary and secondary side: for example, the battery side and grid side of one plug-in hybrid electric vehicle (PHEV). Even though the operation of a DAB-based DC–DC converter is straightforward, various transient processes exist, such as the dead-band effect, which deeply affects the dynamic performance of the converter in real world applications. Compensation of this effect is not easy because of the strong nonlinearity of the entire system. This paper quantitatively analyzed the dead-band effect at different output powers, and presented a model-based controller to realize the nonlinear dead-band compensation strategy, which can effectively mitigate demerits of the traditional PI-based control strategy. The proposed control algorithm is validated through theoretical simulation and experimental results. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Three different control algorithms, traditional single-phase-shift control, dual-phase-shift control (DPSC), and model-based phase-shift control (MPSC), are implemented in a hardware setup and compared for a full-bridge-based isolated bidirectional dc-dc converter. The differences among their dynamic performance and steady-state operations are quantitatively analyzed. Experimental results showed good agreement with theoretical analysis. MPSC showed the best dynamic performance, while DPSC can eliminate reactive power under light-load conditions.

The traditional pulse-width modulation has been widely applied to the electronic and electric device in power system. However, the unexpected harmonics produce much electromagnetic noise which causes torque ripple, mechanical resonance and acoustic noise. By analyzing the harmonics theory of the traditional pulse-width modulation (PWM), a random switching frequency pulse-width modulation (RSFPWM) based on uniform distribution is designed in this paper. The simulation of the random switching frequency pulse-width modulation shows that the peaks of harmonics spectrum lines reduced and is more flattened than the traditional pulse-width modulation. And the simulations verified the validity and feasibility of the random switching frequency pulse-width modulation. The random switching frequency pulse-width modulation proposed in this paper elaborates the basic theory that is suitable for both AC and DC power supply.

In order to improve the stability of Matrix Converter-Permanent Magnet Synchronous Motor (MC-PMSM) system, on the basis of considering nonlinear and parametervariable factors of PMSM, this paper proposes pseudo-derivative feedback (PDF) control. The impacts of PDF control on dynamic performance, static performance, anti-jamming performance and robustness of the MC-PMSM control system are analyzed detailedly. Analysis and simulation results verify that compared with traditional PI and PD control, PDF control effectively improves these performances of the system.

As the traditional methods cannot be effectively used to suppress harmonics in the 400Hz solid-static power supply, a special studying of harmonic analysis and suppression has been made in this paper. The analysis of the topological structure of 400 Hz solid-static power supply leads to the equation of PWM voltage, which makes it possible to summarize the laws of both the distribution of sideband harmonics and the transformation of total harmonic distortion (THD) in this kind of power supply. This paper presents a new design of LC filter for higher harmonics suppression and a novel multi-ply dual-loop proportional-resonant (MDLPR) controller for lower harmonics suppression. They are given experimented verification by means of prototype of 300 kVA 400Hz solid-static power supply which has been developed. The results show that the theoretical analysis is correct and that the method of sectional suppression is effective.

As the fundamental frequency in the medium-frequency power system is 8 times 50Hz, the voltage drop has become such a problem as to affect the waveform quality of medium-frequency power supply. The medium-frequency Dynamic Voltage Restorer (DVR) can be used to eliminate the impact. In this paper, the DVR adopts the independently-controlled three H-bridge, and a precise model of one phase is established. Considering that the traditional PI control strategy cannot be applied to easily achieving a non-static error output and harmonics suppression, this paper adopts the PR controller capable of dealing with the zero steady-state error by controlling the AC signals directly. The simulation and experiment results show that the PR control strategy can effectively compensate the required voltage drop, function well in dynamic response and facilitate the adjustment of a wider bandwidth margin and that it is capable of selective compensation for low harmonic.

In the medium frequency voltage source paralleled inverters, the paralleled diodes in IGBTs run as rectifier before the inverter starts, and the DC capacitor could be damaged by over voltage because of the transient of the circuit. This paper analyzed the characteristics of medium-frequency inverter in parallel operation, compared to the 50Hz inverter. The simplified system model is setup, and the impact of parallel inductor, the use age of DC voltage and filter capacitor on the safety of DC capacitor is analyzed theoretically. The Simulink model is established to verify the theoretical analysis. Finally, measures are proposed to protect DC capacitor.

Due to total harmonic distortion and the time delay of the digital controller in the condition of a single-phase 400 Hz power supply, the traditional proportional-integral-differential controller cannot track the sinusoidal waveforms with zero static error. To improve the performance, the deadbeat control and the proportional-resonant control have been analyzed and contrasted in this paper. The results show that deadbeat control has rapid response but sensitivity to the accuracy of the model and parameters. On this basis, a Dual-Loop Proportional-Resonant control is proposed, which is exercised with the high switching frequency to provide sufficient control bandwidth to reduce the 3rd, 5th and 7th order harmonic. Further, the experiments have been performed on a single-phase 400 Hz power supply prototype. The results show that the Dual-Loop Proportional-Resonant control feeding linear/nonlinear and disturbance loads are satisfactory.

Due to the requirement of total harmonic distortion and the time delay of the digital controller in a single-phase 400 Hz power supply, the traditional proportional integral differential controller cannot track sinusoidal waveforms with zero static error. To improve the performance, proportional-resonant control has been analyzed and contrasted in this paper. On this basis, a Dual-Loop Proportional-Resonant control is proposed, which is implemented with the high switching frequency to provide sufficient control bandwidth to reduce the 3rd, 5th and 7th order harmonic. Finally, experiments on a single-phase 400 Hz power supply prototype show satisfactory results of the Dual-Loop Proportional-Resonant control feeding linear/nonlinear and disturbance loads.

A novel power converter for battery used in the Plug-in Hybrid Electric Vehicle (PHEV) is proposed, which could charge and discharge the battery effectively. The system is composed of two parts: a three phase full bridge PWM rectifier and a DC/DC converter. The PWM rectifier is utilized to rectify the three phase AC to DC voltage, which should be higher than the battery terminal voltage. The DC/DC converter is constructed by a buck-boost circuit, which is a buck circuit under charge mode and a boost circuit under discharge mode. The direct current control (DCC) algorithm is responsible for rectifying the AC output and diminishing the total harmonics distortion. The proportional-integral (PI) controller and bangbang controller is to control the charging current and voltage. The simulation and experiment results validate the effectiveness of proposed algorithm and the feasibility of system.

Battery systems in plug-in hybrid electric vehicles (PHEV) suffer from voltage imbalance. This imbalance reduces the available capacity of certain charge/discharge cycles and shortens the battery life cycle. A new topology and smart balancing strategy for PHEV battery systems are proposed in this paper, which uses a bidirectional DC-DC converter to reduce balancing time and the number of switches needed. The simulation on a ten series connected battery cell is compared to a traditional switched capacitor equalizer.