This paper proposes a new phase current reconstruction scheme without using null switching states for interior permanent magnet synchronous motor (IPMSM) sensorless control. The phase currents are independently reconstructed and no additional test voltage pulses are required. First, the principle of the basic phase current reconstruction for IPMSM drive system is analyzed in detail. Then, an independent phase current reconstruction scheme without using null switching states is proposed. The current reconstruction dead zone is divided into six sectors, and each sector is split into three parts with corresponding vector synthesis methods. Meanwhile, the null switching states, V ₀₀₀ and V ₁₁₁ , are removed from the proposed scheme. In this case, the zero vector is synthesized by the other available vectors. Finally, the reconstructed threephase currents are utilized for high frequency sine-wave voltage injection-based position estimation. The effectiveness of the proposed scheme is verified by experimental results on a 5 kW IPMSM motor prototype, which shows that the reconstructed phase currents track the actual currents accurately under different working conditions.

This paper proposes a sensorless control strategy using sine-wave high-frequency (HF) voltage injection for three-phase four-switch (TPFS) inverter fed interior permanent magnet synchronous motors (IPMSMs) with a single current sensor. Three-phase currents are reconstructed by a single current sensor with modification of the inverter topology. The principle of the phase current reconstruction strategy in TPFS inverter is analyzed and the topology of the proposed drive system is illustrated. Then, the normal areas and dead zones for current reconstruction are investigated in detail, and the vector synthesis method is also explained. Furthermore, the zero vector synthesis strategy and PWM generation method are also presented, where two current sampling points are applied in each PWM cycle for phase current reconstruction. Finally, HF voltage injection-based sensorless control strategy in the proposed drive system is realized by voltage projection on the proposed k-l axis coordinate system. The reconstructed phase currents track the actual ones accurately, and the estimation error of the rotor position by using the reconstructed phase currents is within μ0.1 rad. The effectiveness of the proposed scheme is verified by simulation and experimental results on a 5 kW IPMSM prototype.

This paper proposes a mutual calibration strategy for multiple current sensors in an electric vehicle motor drive. The motor drive usually consists of three current sensors, i.e., a DC-bus current sensor and two phase current sensors. Due to the aging effect and harsh operating environment, the accuracy uncertainty issue is inevitable in these crucial sensors, which results in poor driving performance. In this paper, the detection voltage injection (DV-Injection) method is proposed for mutual calibration of the aforementioned current sensors. Two opposite basic vectors are set together to detect and eliminate the offset error of the DC-bus current sensor. Then, both the directly measured phase-current values by the phase-current sensors and the indirectly measured values by the DC-bus current sensor are sampled. These values are utilized for mutual calibration of the phase-current sensor offset errors and scaling error differences among all the current sensors. Meanwhile, the DV-Injection process is only applied in the period of calibration process, whereas in the remaining intervals the space vector pulse width modulation (SVPWM) technology is utilized. Finally, the effectiveness of the proposed scheme is verified by simulation study in Matlab/Simulink and experimental results on a 5kW IPMSM motor prototype.

The current reconstruction strategies using single current sensor in the motor drives are widely researched. However, the sampled currents do not represent the average values within the modulation period, especially for the asymmetric modulation or asymmetric sampling solutions. This is due to the following two reasons: 1) the detected current values obtained at different sampling points are utilized to calculate the three-phase currents; 2) the detected instantaneous currents are applied to estimate the average current values. In this paper, the current change rates under different action vectors are estimated to compensate these errors in a three-phase four-switch (TPFS) interior permanent magnet synchronous motor (IPMSM) drive with single current sensor. The effectiveness of the proposed strategy is verified by experimental results on a 5kW IPMSM motor prototype, which shows that the current reconstruction errors are reduced after compensation.

Due to the unbalanced three-phase currents and the torque ripples and speed fluctuations to the drive caused by the current sampling errors of three-phase current sensors and corresponding signal processing circuits, the estimation on current sampling errors is of great importance to eliminate these adverse effects. The observer-based methods, however, present two defects: first, they could increase the computational burden to the drives, thus limiting their practical applications; second, their high dependence on the system speed or position feedback information might degrade the estimation accuracy. To solve these problems, this article proposed a fixed-point sampling method of lower branch flows and three phase-currents, which adopts the relations between the measured currents, rather than any complex algorithm, to estimate the current sampling errors. To coordinate with the proposed strategy, a fixed-point sampling scheme was accordingly rolled out. Compared with the observer-based methods, as a fixed-point one, much applicable to actual digital controllers, it could reduce the computational burden of the drive. Meanwhile, its effectiveness was verified by experimental results on a 1.5-kW IPMSM prototype, which showed accurate estimated current sampling errors and the effectively eliminated torque ripples and speed fluctuations.

Phase current reconstruction (PCR) strategy can improve the fault tolerance of permanent magnet synchronous motor (PMSM) drives. The PCR precision is largely affected by the unmeasurable zones and time-sharing sampling errors. The upper limit ( T _limit ) of PCR allowable range can reflect the requirement of different PCR methods for the minimum sampling time ( T _min ). With a longer T _limit , there is sufficient time for sampling, even if T _limit is halved due to the symmetrical waveform. Therefore, the extension of T _limit is the key to eliminate the unmeasurable zones and time-sharing sampling errors. In this article, a method to increase T _limit is proposed, which introduces the suitable auxiliary vectors in different regions to extend the duration time of the sampling vectors. With the help of a longer T _limit (12.5% T _s ), it is possible to eliminate all the unmeasurable zones and time-sharing sampling errors, relieve the pressure on the hardware of current loop, improve the sampling accuracy, and facilitate the reliable operation of the drive. Besides, the switching action times of IGBTs can be reduced by about one-third in the high modulation area. The proposed method is finally proved to accurately reconstruct the phase currents by the experimental results on the PMSM prototype.