Yiru Miao

Inductive position sensors have been widely employed in nuclear reactors for monitoring the control rod position. Accurate control rod position information plays a crucial role in regulating the power of nuclear reactors. However, the inductive sensors currently used for control rod position detection exhibit limited measurement accuracy, which may adversely affect safety and reliability. In response to these issues, a segmented coil structure inductive position sensor based on the resonance principle is proposed in this paper. To improve the sensor sensitivity, a resonant circuit is implemented by connecting capacitors in series with the excitation and sensing coils, and a theoretical model is developed. Furthermore, optimizing the resonant capacitance can reduce the nonlinearity error of the sensor. To enhance the load-driving capability of the excitation source, a single-phase inverter circuit is proposed as the excitation source. Only one excitation signal is used to excite multiple coils. ANSYS simulations and experimental measurements are performed to compare sensors with and without the resonant circuit. The results validate the theoretical analysis and demonstrate that the sensor employing the resonant circuit significantly improves sensitivity and enhances linearity range. The sensor achieves a sensitivity of 0.1909 V/mm and a nonlinearity error of less than 2% over the full-scale span.

Among numerous control schemes for permanent magnet synchronous motor (PMSM), model double-vector model predictive current control (DV-MPCC) can achieve good control effects at a relatively low switching frequency. However, only two vectors are used in a control cycle, which leads to the current harmonic distortion and torque ripple. In this paper, based on the mathematical expression of double-vector modulation voltage error, an analytical model for characteristic harmonics of DV-MPCC is established. Then, the discrete mathematical model of MPCC with DC and periodic voltage disturbances caused by the double-vector modulation is established, the influence from the disturbance on the MPCC system is identified. Besides, a quasi-resonant extended state observer (QR-ESO) is proposed to suppress the current harmonics, the design method for the structure and parameter of QR-ESO is presented. Finally, the experimental verification of the proposed MPCC with QR-ESO is conducted, compared with existing MPCC schemes, due to the significant suppression of the characteristic current harmonic, the steady-state and dynamic performances of the DV-MPCC for PMSM are improved.

In more electric aircraft (MEA), the wide input AC frequency range up to 800 Hz significantly increases reactive power in the AC filter capacitors and reduces the system power factor. This paper proposes a vector-coordinated current control strategy to effectively reduce the filter capacitor current and achieve a high power factor and wide input frequency operation of a three-phase, six-switch buck-type rectifier. First, A control-oriented linear model is established in the synchronous rotating d-q frame using feedforward decoupling to enable independent regulation of d- and q-axis currents. Second, capacitive voltage feedforward active damping is introduced to suppress the filtered capacitive current, and the capacitive current is compensated based on the phasor method. Then, by introducing the q-axis control loop, the i_q tracking of the grid-side current tends to be close to zero, improving the reactive power losses. Moreover, this paper analyzes the control loop and parameter sensitivity using MATLAB, and gives the control loop zero-pole configuration and gain design scheme. Finally, A 1kW SiC-based prototype operating at a typical input frequency is constructed, and the experimental results verify the effectiveness of the proposed control scheme.

Controlling three-phase current source rectifiers presents intricate challenges due to the input LC filters and DC bus capacitors. This paper proposes a multiple-loop-based control strategy for current source PWM rectifiers for low-voltage DC distribution systems to address these challenges. Firstly, the independent control of the active and reactive power is achieved based on the adjustment of the d-axis and q-axis currents on the grid side. Subsequently, a compensation scheme of capacitance current using the phasor method is proposed. Next, as an alternative damping method, the capacitor-voltage feedback is used to suppress the LC resonance, and the influence of the feedback gains on the system's stability is discussed. Furthermore, the dynamic performance is further improved by adopting DC-side inductor-current feedback and a damping factor. Ultimately, the feasibility and efficacy of the proposed approach are confirmed through experiments.

This paper investigates the linearity degradation of inductive displacement sensors subjected to large air-gap conditions and radial offsets of the rod. A novel electromagnetic inductive sensor is proposed to enable simultaneous measurement of axial displacement and radial offset. The sensor consists of circular excitation coils and orthogonally staggered radial saddle-shaped detection coils, effectively decoupling radial offsets along the x- and y-axes. A theoretical model based on radial relative offset coefficients is developed to evaluate the impact of radial offset on the linearity of axial displacement measurements. To improve measurement accuracy, a measurement method integrating a gaussian process regression (GPR) model and two-dimensional (2D) spline interpolation is proposed to estimate radial offset and compensate axial displacement errors. Experimental results demonstrate that the proposed method reduces linearity errors to approximately 1.04% along the x-axis and 0.66% along the y-axis, corresponding to improvements of 79.47% and 82.60%, respectively. The maximum root mean square error (RMSE) for the estimated radial offset distance is limited to 0.44 mm in the offset direction. These findings validate the effectiveness of both the sensor design and the compensation method.

This paper presents a strategy to mitigate electromagnetic noise in induction motors for electric vehicles by optimizing the rotor slot count and skewing distance. Initially, the magnetomotive forces (MMF) of the stator and rotor windings, air-gap permeance, and the predominant radial electromagnetic force waves in the air-gap magnetic field were analytically determined and compiled. A finite element model of the original 36/42 straight-slot configuration was established for simulation validation. Subsequently, a preliminary optimization scheme for rotor slot number was proposed. A systematic analysis was conducted of the circumferential distribution of radial force waves and their harmonic components in both temporal and spatial orders by comparing electromagnetic vibration characteristics across different rotor slot configurations (42 versus 53 slots) using two-dimensional Fourier decomposition. Furthermore, building upon the mechanism of tooth harmonic suppression via rotor skewing, an advanced optimization strategy for skewing distance was developed. Comparative analysis of harmonic content in air-gap flux density under three configurations (straight slot, 1.0× skewing, and 1.2× skewing) revealed the optimal solution. Experimental vibration tests demonstrated significant improvements: the optimized 53-slot rotor with 1.2× skewing reduced vibration amplitudes by 5 dB·Hz at the 2nd-order natural frequency, 5 dB·Hz at the 3rd-order natural frequency, and 18 dB·Hz at the 3rd-order resonance peak compared to the original 42-slot straight-slot design. These results confirm that coordinated optimization of rotor slot number and skewing distance effectively mitigates electromagnetic vibration and noise in traction motors.

Compared to the finite control set model predictive current control (MPCC) for surface-mounted permanent magnet synchronous motor (SPMSM), dual-vector deadbeat MPCC can improve the current tracking accuracy with rarely increasing switching frequency, which can improve the efficiency and performance of SPMSM drive system. However, the voltage error between the reference and synthesizing vectors cannot be eliminated, leading to current harmonic and torque ripple. To improve the control performance for SPMSM, the MPCC scheme with quasi-resonant extended state observer (ESO) is proposed in this paper. First, the mathematical expression of voltage error caused by dual-vector modulation is derived, and its harmonic characteristic is obtained. Then, the transfer functions of MPCC are derived, and the impact of DC and periodic voltage disturbances on speed and current is analyzed. To reduce the current harmonic caused by periodic voltage disturbance, a quasi-resonant ESO is introduced into the MPCC system, its mathematical model and the influence of parameters on stability and dynamic performance are presented. Finally, the feasibility and effectiveness of the proposed dual-vector deadbeat MPCC scheme with quasi-resonant ESO are verified by the experimental results, compared with two existing improved dual-vector MPCC schemes, the best steady-state performance can be obtained with minimum computation burden and no affection of the dynamic performance.

Model predictive current control (MPCC) based on sliding mode disturbance observer (SMDO) effectively addresses the issues arising from parameter mismatches and unmodeled nonlinear elements in Permanent magnet synchronous motor (PMSM). However, conventional sliding mode faces a trade-off between reaching speed and chattering, and their closed-loop transfer functions are often challenging to derive. To overcome these limitations, this paper proposes a model-free predictive current control method based on an adaptive sliding mode disturbance observer (ASMDO-MFPCC). By exploiting a novel decoupled PMSM ultra-local model and a novel sliding mode control law, a discrete-time observer is designed to enhance convergence speed and suppress chattering. The stability of the observer is analyzed, and its parameter ranges are theoretically determined. Moreover, by linearizing the control law near the designed sliding surface, a complex vector linear model is established for the entire system, allowing closed-loop transfer function analysis to confirm that deadbeat performance can be preserved under accurate parameter settings. To further improve the system’s robustness, a simple yet effective inductance identification algorithm is proposed for real-time calibration of the predictive control system. This algorithm operates independently of the observer design. Experimental results validate the effectiveness of the proposed current control scheme.

This article develops a new inductive displacement sensor with a segmented multi-group coil structure, which is suitable for the displacement measurement of control rods in nuclear reactors. Each group coil of the sensor consists of two excitation coils and one sensing coil. The excitation and sensing coils are segmented to extend the linearity range of the displacement sensor. It abandons the traditional sensor’s method of using nonlinear compensation to achieve large-stroke displacement measurement. Providing an alternating current (AC) signal to the excitation coil and processing the induced voltage generated by each sensing coil can directly achieve the high-precision measurement of core displacement. The mathematical model of the variations in the sensing coil voltage caused by the movement of the core is established. The impacts of the excitation coil structure, the number of turns of the excitation coil, and the excitation frequency on the output characteristics of the designed sensor are analyzed by finite element simulation. Based on the analysis and design, a sensor prototype is built and tested in the laboratory. The measurement results show that the linearity error is 0.35% and the maximum measuring error can be limited within 1.5 mm, which is sufficient to meet the practical requirements in a nuclear reactor environment.