The precise information of initial rotor position is very important to high performance Interior Permanent Magnet Synchronous Machine (IPMSM) adopting incremental encoder, which can normally be obtained by the high-frequency (HF) rotating or pulsating voltage injection methods. However, the demodulation procedure may confront with the challenge of constrained stability and limited accuracy. For improving estimation accuracy, an improved impulse injection method with merits of simple and fast is proposed. It is carried out by generating a series of phase-axial injections to calculate the probable rotor position, then injecting two reciprocal voltage pulses to obtain the rotor polarity, and finally injecting iterative voltage vectors to obtain the real position rapidly. During the estimation process, the filters to extract the high frequency current signals are not needed. The method effectiveness is validated by the measured results of IPMSM test platform. In the same time, its application limitation is deduced by comparison with the measured results between IPMSM and surface-mounted PMSM (SPMSM). It is shown that the estimation algorithm is compatible with motor parameter differences and can reduce the influence of inductance saturation and nonlinear voltage error. Therefore, the proposed method not only improves the accuracy and robustness of the PMSM sensorless startup control, but also ensures the fast response.

The in-wheel electric vehicle with distributed drive units has better stability and flexibility than traditional centralized drives, but may encounter a higher failure rate due to additional actuators and sensors, especially that the faults of the wheel-side position sensor make motor torque out of control. To overcome this problem, a fault-tolerant control strategy with a multi-states switching method is proposed. The strategy judges the sensor failure by verifying redundant speed information, realizes sensorless control schemes by flux-observer based algorithm in high-speed range and I-F control algorithm in low-speed range with low acoustic noise, and applies adaptive transition process between different control schemes. To pursuit high stability, the signal-to-noise analysis for fault judgment due to sensorless estimation accuracy is discussed. Meanwhile, the principle of I-F resonant oscillations during the transition process is initially deduced in detail, and the conclusion of stability condition is obtained. Finally, the influence of system parameters on resonance performance is analyzed by simulation, and the effectiveness and reliability of the proposed strategy for the risk-controlling process are verified by experiments.

The unified power quality conditioner (UPQC) is an effective solution for addressing power quality issues in modern power systems, with its ability to regulate both voltage and current. However, existing UPQC operational strategies lack sufficient adaptability and flexibility in managing load-side phase, especially when dealing with complex grid disturbances. This article proposes a unified framework for adaptive and flexible phase angle regulation, primarily based on two novel algorithms: the practical optimized-VA-loading operational strategy (POOS) and the universal flexible control method (UFCM). First, the proposed POOS method, utilizing phase angle control, enables online VA loading optimization within the UPQC's safe operating range according to real-time grid conditions. A comprehensive discussion of the method is presented, including the working principles, operational boundaries, and iterative computation process. Second, the proposed UFCM ensures smooth phase control of the load voltage throughout complex grid events. A dual-speed phase-locked loop is introduced to decouple the target and real-time phase, with parameter design guidelines and a discretization process provided. Furthermore, the unified framework is thoroughly explained, which balances the steady-state optimization requirements of the UPQC with the dynamic load-side power quality. Finally, experimental results validate the effectiveness of the unified framework under complex grid disturbance scenarios.

When the electromagnetic (EM) force ${F}_{\mathrm{M}}$ is used to balance the dynamical axial gas separation force ${F}_{\text{gas}}$ of scroll compressors, the control effect, system complexity, reliability, and cost are severely restricted by the dynamic force sensor systems. For this consideration, a scroll compressor without online force sensors is designed, and an innovative EM force control method based on “EM force-current ( ${F}_{\mathrm{M}}{\rm{ - }}{i}_{\mathrm{M}}$ )” nonlinear model is proposed. The “ ${F}_{\mathrm{M}}{\rm{ - }}{i}_{\mathrm{M}}$ ” nonlinear relationship changes with frequency and EM gap, so it is difficult to determine the relationship online. Even when the target EM force is precise, it is difficult to obtain the corresponding control current to generate the actual EM force. Given this difficulty and challenge, this article creatively puts forward a method. When the target EM force is always kept as the final target curve, the “ ${F}_{\mathrm{M}}{\rm{ - }}{i}_{\mathrm{M}}$ ” relationship, used to decode the control current, is adjusted by adjusting the estimated value of the EM gap to control the actual EM force. The best dynamic contact seal and high-quality steady-state operation can be realized by optimizing the estimated EM gap value. This method consists of two stages: set up an offline database and carry out online control. At the offline stage, the “ ${F}_{\mathrm{M}}{\rm{ - }}{i}_{\mathrm{M}}$ ” nonlinear relations with different frequencies and EM gaps are sampled with force sensors and then stored using Prandtl–Ishlinskii (PI) model. At the online stage, no online feedback force sensors are needed. The current needed to produce exact F _M is decoded from the chosen “ ${F}_{\mathrm{M}}{\rm{ - }}{i}_{\mathrm{M}}$ ” PI model established at the offline stage. The creative “ ${F}_{\mathrm{M}}{\rm{ - }}{i}_{\mathrm{M}}$ ” model choosing method is proposed, which relies on the iterative estimations of EM gap value. The results of the quasi-prototype experiment show that the aforesaid control method is feasible.

High reliability and fault-tolerant operation are critical for the safety of distributed electric vehicles (EVs). To mitigate surge current, torque imbalance and vehicle instability during protective braking, an enhanced transient switching method for power switches in the motor driver is proposed. By utilizing the electrical angle of the stator current and a step delay control associated with motor parameters, the stepwise active short-circuit method facilitates smooth transitions between normal operation state and the ASC braking state, minimizing reliance on rotor position detections. Simulations and experiments on a light EV with Mecanum wheels demonstrate its effectiveness in improving safety and stability. Comparing the stepwise proposed method with conventional direct ASC braking processes, the impulse current was reduced and the vehicle’s yaw rate decreased significantly. The study contributes to the advancement of fault protection techniques for distributed drive EVs, offering insights into mitigating transient short-circuit currents and torque jerks during protective braking controls.