Sensorless Control of IPMSM Using Sliding Observer Based on Model for Realizing MTPA Control

Rotating high frequency (HF) carrier signal injection method is commonly used in interior permanent magnet synchronous machines’ (IPMSMs) sensorless control due to its simple principle. However, the accuracy of the rotor position estimation will decrease because of some adverse impacts, such as system delays, stator resistance, cross coupling effect, and inverter nonlinearities. In order to solve these problems, a strategy to inject bidirectional rotating HF carrier signals into the machine is proposed in this paper. Differing from those conventional methods, the proposed method injects simultaneously two HF carrier voltages with different rotational frequencies and directions. Four independent equations are constructed and obtained by demodulating every frequency components in the response currents. By solving these four equations, the rotor position can be calculated directly, which effectively minimizes the effects of the stator resistance, system delays, and inverter nonlinearities. In addition, the compensation of the cross coupling effect on the rotor position estimation is analyzed and deduced in detail to improve the estimation accuracy. Finally, the experimental results on an IPMSM demonstrate that the rotor position with good steady-state and dynamic performance can be obtained accurately by using the proposed sensorless control strategy.

With the aim of controlling interior permanent magnet synchronous machine (IPMSM) throughout the whole speed range, a combined sensorless control approach is proposed to get beyond the limitations of a single sensorless control method. As the speed increases, an advanced sliding mode observer (SMO) technique is applied to accurately determine the location of the rotor. This approach effectively addresses the issue of frequent high frequency disturbances encountered with conventional SMO methods. At lower speeds, a high frequency square wave injection method (HFSWI) is utilized for rotor site estimation. This method boasts improved system dynamics and requires less reliance on low pass filters when compared to traditional high frequency injection methods (HFI). Additionally, a weighted average switching algorithm is applied in the combined control area to ensure a seamless transition between control strategies.

In this paper, a simpler but more effective sensorless control scheme is proposed for an interior permanent-magnet synchronous motor drives at very low speed. Compared to the commonly method using three filter to extract rotor position signal, the new method uses only one low pass filter, leads to a lower implementation processing time, the simulations have proved the correctness and validity of this method.

A position sensorless control of interior permanent synchronous motor (IPMSM) equipped with LC sinusoidal filter based on the full-order sliding mode observer (FOSMO) and feedforward quadrature phase-locked loop (FQPLL) is proposed in this paper. The FOSMO is designed to estimate stator currents, stator voltages, and extended back electromotive forces (EEMFs) of IPMSM. To enhance the rapidity of the convergence and accuracy of the estimation of the FOSMO, an adaptive gain matrix is designed by adopting equivalent control theory and Lyapunov stability theory. In order to suppress the DC deviation in the position estimation error under acceleration or deceleration operations, a robust and anti-interference feedforward loop without differentiator and motor parameters is added to the conventional quadrature phase-locked loop. The parameter design method of the proposed FQPLL is studied by analysis of the frequency characteristics. The experimental results verify the effectiveness of the proposed strategy.

Sliding mode observer(SMO) is an effective extended back-EMF (EEMF)-based sensorless strategy for Interior permanent magnet synchronous motor drives in middle- or high-speed region. When the switching frequency is low, the rich low harmonics limit the use of this method. Especially, when the carrier ratio(CR) is less than or equal to 21, the carrier-based synchronous modulation is used to guarantee the symmetry of the output waveform. In order to further reduce interference harmonics and improve the performance of SMO in synchronous modulation region, an optimized asymmetric space vector modulation (OASVM) method is proposed, in the switching cycles that voltage reference vector is located at 17th and 19th vectors, the switching frequency is doubled. Compared with conventional ASVM, OASVM can significantly reduce the signal overlaps. As a result, in the process of position estimation with a phase-lock loop (PLL), the estimation error is reduced. The results are also verified on a 3.7kW IPMSM platform.

Filtering method exerts direct effects on extracting high frequency current signal in carrier injection based sensorless control for IPMSM drives, and further affects the position estimation accuracy. A wavelet based filtering approach superior to conventional Butterworth band-pass filter is proposed and verified on a 2.2-kW IPMSM sensorless drives.

Injecting high-frequency (HF) square-wave voltage signals into the estimated d-axis serves as an effective strategy for achieving zero and low-speed position sensorless control in interior permanent magnet synchronous motor (IPMSM) drives. However, the application of this method in diverse fields is circumscribed. The root cause lies in the fact that the injection of high - frequency voltage engenders noise that is not only perceptible but also causes discomfort, thereby impeding the extensive adoption of this method in practical applications. To reduce unnecessary audible noise, this paper proposes an improved low-noise random voltage injection method adapting Markov chain and frequency adaptive complex coefficient filter (FACCF). For the estimated d - axis, two square - wave voltage signals with randomly varying frequencies and amplitudes are injected. Subsequently, the position information is extracted using a corresponding decoupled signal. The power spectrum density (PSD) of the induced HF currents is contrasted and anatomized with respect to the fixed - frequency injection approach and the optimized methodology. Comparing with fixed frequency injection method, the simulation and experiment demonstrates that the Markov chain based random signal switching can further reduce the audible noise, and FACCF based position information extraction method can solve the phase delay problem caused by using low-pass filter (LPF).

The MTPA control is a simple and practical method to achieve high-efficiency operation of IPMSM. Recently, many MTPA control methods have been investigated to guarantee the minimum copper loss of IPMSM [1–6]. In most commercial drives, the MTPA control is achieved with the lookup tables or the polynomial fitting. The conventional MTPA control method is parameter dependent, and the effectiveness relies on the knowledge of the accurate motor parameters. The online parameter identification or offline parameter testing is necessary to achieve the robust MTPA operation [4–6]. Recently, the test signals injection method has been proposed, which can allow the MTPA trajectory to be learned online; however the signal injection method looks somewhat complex [1–3]. In most literatures, the online MTPA control methods used in IPMSM drive system should be installed with a position sensor for the control. Some key issues including the current ripple and torque transient should be carefully considered for the sensorless IPMSM drive.

This work presents a sensorless Maximum Torque per Ampere (MTPA) for the synchronous reluctance motor (SynRM) based on speed and torque observer. From the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\alpha \beta$</tex> mathematical model alongside with extended back-EMF model from the literature, a current and back-EMF observer is applied, allowing to estimation of the speed and position. Furthermore, a second speed observer is proposed allowing for a torque disturbance observer, generating the torque reference for MTPA algorithm. Moreover, the MTPA provides the synchronous reference currents which are controlled via Field Oriented Control. Simulation results demonstrate the effectiveness of the proposed scheme. Simulation results demonstrate the effectiveness of the proposed scheme.