High Frequency Signal Injection Method Research Articles

High frequency signal injection method for sensorless permanent magnet synchronous motor drives

The objective of this project is to design a high frequency signal injection method for sensorless control of permanent magnet synchronous motor (PMSM) drives. Generally, the PMSM drives control requires the appearance of speed and positon sensor to measure the motor speed hence to feedback the information for variable speed drives operation. The usage of the sensor will increase the size, cost, extra hardwire and feedback devices. Therefore, there is motivation to eliminate this type of sensor by injecting high frequency signal and utilizing the electrical parameter from the motor so that the speed and positon of rotor can be estimated. The proposed position and speed sensorless control method using high frequency signal injection together with all the power electronic circuit are modelled using Simulink. PMSM sensorless driveis simulated and the results are analyzed in terms of speed, torque and stator current response without load disturbance but under the specification of varying speed, forward to reverse operation, reverse to forward operation and step change in reference speed. The results show that the signal injection method performs well during start-up and low speed operation.

Adaptive Pseudorandom High-Frequency Square-Wave Voltage Injection Based Sensorless Control for SynRM Drives

The remarkable inductance nonlinearities of synchronous reluctance motors (SynRMs) could result in operating-point-dependent high-frequency (HF) current responses, and more HF losses with audible noises with conventional constant amplitude high-frequency signal injection (HFSI) methods applied. This article proposes an adaptive pseudorandom high-frequency square-wave voltage injection (AP-HFSVI) based sensorless control method for SynRM drives at low-speed operation. An adaptive HF current control strategy is applied using pseudorandom injection patterns to adapt to the nonlinear characteristic of SynRM inductances. The magnitude of the injected HF voltage signals can be adjusted adaptively with the load variation online via HF current adaptive control scheme, which processes and regulates the HF current components to be constant. Hence, the HF losses and audible noises can be effectively suppressed due to the decreasing magnitude of injected signals. The current power spectra density of the AP-HFSVI method is analyzed and compared with the conventional HFSI method. The effectiveness and superiority of the proposed sensorless control method are verified with experiments on a 3-kW SynRM drive platform.

An I-f Startup Method with Compensation Loops for PMSM with Smooth Transition

The back-EMF based sensorless drive of permanent magnet synchronous machines (PMSMs) is attractive for many industrial applications due to its simplicity and good reliability. For applications such as pumps and fans, in which there is no demand for high dynamic performance in the low-speed range, the I-f method for startup is considered as a much simpler solution than many high-frequency signal injection methods. This paper proposes an I-f startup method that enhances the performance by adopting a frequency compensation loop to improve the system stability and a current vector magnitude compensation loop to obtain a smooth transition to back-EMF based sensorless field-oriented-control (FOC). The experimental results verify the effectiveness of the proposed method and its superior performance compared with the existing I-f starting method.

Design of a Low-Order FIR Filter for a High-Frequency Square-Wave Voltage Injection Method of the PMLSM Used in Maglev Train

In position sensorless control based on a high-frequency pulsating voltage injection method, filters are used to complete the extraction of high-frequency response signals for position observation. A finite impulse response (FIR) filter has the advantages of good stability and linear phase. However, the FIR filter designed by using traditional methods has a high order which will cause a large time delay. This paper proposes a low-order FIR filter design method for a high-frequency signal injection method in the permanent magnet linear synchronous motor. Based on the frequency characteristics of the current signal, the requirement that the FIR filter needs to meet were analyzed. According to the amplitude–frequency characteristic of the FIR filter, these requirements were converted into constraint equations. By solving these equations, the coefficient of the FIR filter could be obtained. The simulation and experiment results showed the effectiveness of this low-order FIR filter.

Research on rotating high-frequency current injection method based on LC resonance network

The high-frequency signal injection method is an effective method to realise the sensorless detection of the rotor position of the permanent magnet synchronous motor (PMSM), which can estimate any position of the rotor in the whole speed range. When the frequency of the injected signal is high, the rotating high-frequency current injection method can obtain more significant signal with rotor position information for PMSM with small salient characteristics, so it can obtain higher position estimation accuracy. However, the traditional method of injecting high-frequency current needs current source inverter or complex control mode, which is difficult to apply in practice. The drive circuit based on LC resonant network can convert the resonant voltage signal into the current signal, thus the driving voltage and rotating high-frequency current signals can be simultaneously provided to the PMSM through the voltage source inverter, which greatly facilitates the extraction and processing of rotor position information and improves the sensorless detection accuracy of rotor position. The experimental results verified the effectiveness of the circuit and method.

Research on rotating high-frequency current injection method based on LC resonance network

The high-frequency signal injection method is an effective method to realise the sensorless detection of the rotor position of the permanent magnet synchronous motor (PMSM), which can estimate any position of the rotor in the whole speed range. When the frequency of the injected signal is high, the rotating high-frequency current injection method can obtain more significant signal with rotor position information for PMSM with small salient characteristics, so it can obtain higher position estimation accuracy. However, the traditional method of injecting high-frequency current needs current source inverter or complex control mode, which is difficult to apply in practice. The drive circuit based on LC resonant network can convert the resonant voltage signal into the current signal, thus the driving voltage and rotating high-frequency current signals can be simultaneously provided to the PMSM through the voltage source inverter, which greatly facilitates the extraction and processing of rotor position information and improves the sensorless detection accuracy of rotor position. The experimental results verified the effectiveness of the circuit and method.

Speed Sensorless Control for Permanent Magnet Synchronous Motors Based on Finite Position Set

This article presents a novel method for the sensorless control of interior permanent-magnet synchronous motors. An iterative search strategy based on dichotomy is proposed to provide a finite number of rotor position angles with good accuracy. These position angles are used to calculate the back electromotive force (EMF) in d -axis. The optimal rotor position angle is the one that yields a back EMF minimizing the defined cost function. With the increase of the iterations, the accuracy of rotor position angle increases geometrically. To effectively extract the back EMF signal under the low-speed condition, the high-frequency signal injection method is used to realize the low-speed operation of the motor. A hybrid control strategy is adopted to achieve the smooth switching from the low-speed to high-speed. The performance of the proposed method has been validated experimentally and compared with that of the conventional phase locked loop under different conditions.

Rotor Position Estimation Method for Brushless Synchronous Machine Based on Second-Order Generated Integrator in the Starting Mode

In this article, a novel rotor position estimation method based on the second-order generated integrator (SOGI) is proposed for sensorless starting control of the brushless synchronous machine (BSM) with the indirect high-frequency signal injection method for the aircraft. The high-frequency signals are injected into the stator field windings of the main exciter, and the response signals coupled to armature windings and the rectifier are indirectly injected into the field windings of the main generator. The envelope demodulation method is proposed for the rotor position estimation, and the unitized filter design for the more accurate rotor position signal extraction is exploited instead of the traditional bandpass filter and low-phase filter based on the optimal parameters of SOGI. Finally, the feasibility and effectiveness of the proposed rotor position estimation method for BSM in the sensorless control are verified by both simulation and experimental results.

Unified Graphical Model of High-Frequency Signal Injection Methods for PMSM Sensorless Control

High-frequency (HF) signal injection methods have proved to be good candidates for permanent magnet synchronous motor sensorless control at zero or low speed. However, conventional methods have some shortcomings, and several improved methods have been put forward by scholars. In order to analyze the essential relationships among these methods, a unified graphical model is proposed in this paper based on the analysis of mechanism of conventional HF signal injection methods. According to the unified graphical model, the signal modulation modes can be categorized into phase-modulated-based HF injection (PMHI) and amplitude-modulated-based HF injection (AMHI), meanwhile the demodulation modes can be classified into open-loop calculation and close-loop convergence. Besides, novel methods are easily deduced from the unified graphical model. Furthermore, the effects of adverse factors, including resistance, digital control delay, inverter nonlinearity, and cross saturation on PMHI and AMHI are analyzed, respectively. Finally, experimental results prove the validity of the theoretical analysis.

Magnet Temperature Estimation in Permanent Magnet Synchronous Machines Using the High Frequency Inductance

Permanent magnet synchronous machines (PMSMs) torque production capability depends on the permanent magnets (PMs) magnetization state, which can be affected by PMs’ temperature and by the current flowing throughout the stator windings; knowledge of the PMs’ temperature can be therefore of great importance both for control and monitoring purposes. PMs’ temperature can be measured or estimated; PM temperature measurement is not easy and is not normally implemented in commercial drives. PM temperature estimation methods can be divided into thermal models based, back electromotive force (BEMF)-based, and signal injection based methods. Existing high frequency (HF) signal injection methods estimate the PM temperature from the measured stator HF resistance. Unfortunately, the resistance is also affected by magnetoresistive effect, which can limit the accuracy of the estimates. This paper proposes the use of the stator d -axis HF inductance for PM temperature estimation. This makes temperature estimation insensitive to magnetoresistive effect. In addition, it allows the use of higher frequencies, reducing the adverse impact of the injected signal on machine performance.

Enhanced Linear ADRC Strategy for HF Pulse Voltage Signal Injection-Based Sensorless IPMSM Drives

High-frequency (HF) signal injection methods have been widely employed in the sensorless control of interior permanent magnet synchronous motor (IPMSM) drives from zero to low speed. However, the control performance will be deteriorated severely when the motor subjects to the disturbance. To cope with this issue, an enhanced linear active disturbance rejection control (LADRC)-based HF pulse voltage signal injection method is proposed in this paper. The cascaded extended state observer is established to guarantee relatively timely and accurate estimation of the total disturbance. The linear control law is generated to compensate for the total disturbance in a feedforward way, which reduces the plant to approximate a canonical first-order integral. The tracking performance and the stability of the enhanced LADRC are analyzed theoretically. Maximum torque per ampere control is adopted to reduce the estimation burden by making full use of the reluctance torque, which helps to further improve the tracking performance of the enhanced LADRC. Finally, the validity of the proposed sensorless control scheme is verified on a 2.2-kW IPMSM drive platform.

Rotor Position Estimation of PMSM in Low-Speed Region and Standstill Using Zero-Voltage Vector Injection

High-frequency signal injection methods have been widely used in sensorless control of permanent-magnet synchronous motor (PMSM) drives. However, the acoustic noise and torque ripples caused by the injected high-frequency signal limit the application of the methods. To avoid these drawbacks, this paper proposes a position estimation method that combines derivative calculations of current and zero-voltage-vector (ZVV) injection, which is especially effective for zero- and low-speed operation of sensorless PMSM drives. This investigation mainly focuses on the extraction of rotor position from ZVV period and the improvements of the accuracy of estimated position. The PMSM equation is developed in the stationary frame when ZVV is applied. The proposed $d$ -axis current allocation scheme ensures the application of the proposed method from no load to rated load. A modified space vector pulse width modulation (SVPWM) control strategy and a ZVV extension scheme are employed to improve the accuracy of estimated position, which also makes the method more realizable. Further, a novel current sampling method that selects two suitable phase currents for derivative calculation according to the voltage sector location is proposed, which can help reduce current derivative ripples and decrease position estimation errors. Finally, the effectiveness of the proposed position estimation strategy is verified on a 1.0-kW interior PMSM (IPMSM) drive platform.

Influence of PM Coating on PM Magnetization State Estimation Methods Based on Magnetoresistive Effect

Variable flux permanent magnet synchronous machine (PMSMs) (VF-PMSMs) are gaining importance, especially in automotive applications. The use of such machines will require the development of methods to estimate the permanent-magnet (PM) magnetization state. PM magnetization state estimation methods reported in literature include back-electromagnetic (EMF) compatibility and high-frequency signal injection. One advantage of high-frequency signal injection methods is that they can operate over the whole speed range, with practically no interference with the regular operation of the machine. Magnetization estimation using high-frequency injection relies on the variation of the d- axis high-frequency inductance with the saturation produced by the magnets. Alternatively, the changes of the magnet electrical resistance due to the magnetoresistive effect can also be used for this purpose. These methods have been tested with different materials, including NdFeB, AlNiCo, and SmCo magnets. NdFeB magnets are usually protected from oxidation using NiCuNi coating. However, NiCuNi also shows magnetoresistance effect and can therefore affect the performance of the method when used with magnets having NiCuNi coating. This paper studies the effects of PM coating on the performance of methods, which estimate the magnetization state of the magnet using the magnetoresistance effect by means of high-frequency signal injection. The analysis will include NdFeB, AlNiCo, and SmCo magnets.

An improved rotating HF signal injection method based on FIR filters for state estimation of BPMSM sensorless control

An improved rotating high-frequency signal injection method based on a finite impulse-response filter for state estimation of bearingless permanent magnet synchronous motor sensorless control is developed in this article. A novel equiripple optimal approximation finite impulse-response filter, which can achieve that the maximum error of pass-band and stop-band is minimum than other finite impulse-response filter under the conditions of the same-order magnitude, is introduced to extract the high-frequency current signal and realize minimum extraction error. The rotor position error signal can be extracted using heterodyning processing to the high-frequency current. The proposed method can effectively eliminate the synchronous shaft filter and reduce the complexity of the system. Linear-phase compensation is used in the finite impulse-response filter to achieve minimum delay of rotor speed and position estimation. The BPMSM sensorless vector control system is set up based on this estimation approach. Simulation results indicate that the proposed method integrated off-line optimization of a finite impulse-response filter and linear-phase compensation can accurately estimate the rotor position and speed in the full-speed range.

An Accurate Virtual Signal Injection Control of MTPA for an IPMSM With Fast Dynamic Response

A maximum torque per ampere (MTPA) control based on virtual signal injection for an interior permanent magnet synchronous motor with fast dynamic response is proposed in this paper. A small square wave signal is mathematically injected into the current angle for accurately tracking MTPA points. The extracted derivative of electromagnetic torque is utilized to compensate the initially set current angle to the real MTPA operation current angle. Due to the absence of bandpass and low-pass filters, which are essential in the sinusoidal injected signal scheme, this method shows good dynamic response. By incorporating a modified equation for the torque after signal injection, the steady-state accuracy is also enhanced. The $d$ - and $q$ -axis current references are obtained through the current vector magnitude and optimal current angle instead of using the torque equation with nominal motor parameters, which guarantees the accuracy of the output torque. The proposed scheme is parameter independent, and no real signal is injected to the current or voltage command. Thus, the problems of the high-frequency signal injection method are avoided. A prototype is set up, and experiments are carried out to verify effectiveness and robustness of the proposed control scheme.

Passive Islanding Detection Using Inverter Nonlinear Effects

This paper analyzes the use of the voltage distortions in pulse width modulation voltage-source inverters caused by the inverter switching for islanding detection purposes. The nonideal characteristics of the inverters, mainly due to the dead time needed to have safe commutations, produce fundamental frequency-dependent harmonics (−5th, 7th, …) in the output voltage. These harmonic order are, in principle, an unwanted effect, as they reduce the power quality. However, they can potentially be used for islanding detection purposes. The physical principles of the method would be the same as for high-frequency signal injection methods that have already been proposed, but without the need of injecting a high-frequency signal, behaving, therefore, as a passive islanding detection technique.

High-Frequency Signal Injection Method Based on Duty Cycle Shifting Without Maximum Fundamental Voltage Magnitude Loss

High-frequency signal injection (HFSI) method is widely used in machine sensorless control in low speed operation range. The conventional HFSI methods are to superimpose high-frequency voltage signals onto the commanded stator voltage vector. Thus, the magnitude of the voltage used for machine torque production is sacrificed and these methods are not applicable for high-speed operation range. In this paper, a new HFSI method, in which high-frequency signal is generated by shifting the duty cycles between two neighboring switching periods, is proposed. This method allows injecting a high-frequency signal at half of the switching frequency without the necessity to sacrifice the machine fundamental voltage amplitude. This may be utilized to develop a new position estimation algorithm without involving the machine inductance in the medium- to high-speed range. As an application example, a new position estimation algorithm using the proposed HFSI method is developed and applied to a synchronous reluctance machine drive system. The proposed algorithm focuses on the medium- to high-speed range with the advantage of no filter needed for position information extraction and a machine-inductance-independent sensorless control implementation scheme is achieved. Experimental results are given to support the proposed new approaches.

Comparative Analysis of BEMF and Pulsating High-Frequency Current Injection Methods for PM Temperature Estimation in PMSMs

Permanent magnet synchronous machines performance is highly dependent on the permanent magnets (PMs) temperature. However, PM temperature measurement is not easy and is not normally implemented in standard machines. Alternatively, PM temperature can be estimated. PM temperature estimation methods can be divided into three major groups: thermal model-based methods, BEMF-based methods, and methods based on the injection of some form of high-frequency signal into the stator terminals of the machine. One concern for thermal model-based methods is that the model often needs to be adjusted for each machine design and application, knowledge of the machine geometry, materials, and cooling system being, therefore, required. On the contrary, BEMF methods and methods based on high-frequency signal injection estimate the magnet temperature from measurable electrical variables, knowledge of the geometry or cooling system not being required. Though they use the same type of signals, BEMF and high-frequency signal injection methods present relevant differences. This paper realizes a comparative analysis of both methods. Physical principles, performance, and implementation will be addressed.

On the Proprieties of the Differential Cross-Saturation Inductance in Synchronous Machines

The cross-saturation inductance is a mutual inductance due to the saturation of portions of the magnetic circuit of one axis caused by the current of the other axis. In sensorless drives, the differential cross-saturation inductance causes an error in the estimation of the rotor position when it is performed by means of the high frequency signal injection methods. The knowledge of the properties of cross-saturation inductance is therefore essential to minimize any distortion effect on the position estimation. This paper aims to describe the properties of the cross-saturation inductance for different types of synchronous machine, such as reluctance, interior permanent-magnet, and surface-mounted permanent-magnet machines. Information is also given to predict the error in the estimated position for any stator currents, useful for implementing an error compensation technique or to detect the feasible operating regions using the high frequency voltage injection technique. The analysis is supported by finite element simulations and experimental measurements.

Sensorless control of IPMSM for last 10 years and next 5 years

This paper presents the developments of sensorless control of interior permanent magnet synchronous machine (IPMSM) for last 10 years, which could be divided into the past and the present for each 5 years. Several popular methods developed for last 10 years would be described and evaluated, and the limitations with the methods are discussed. In the past a concept extended EMF (EEMF) was introduced and it can model IPMSM as a non-salient motor, meaning that the representation of IPMSM in the estimated rotor reference frame would be much simpler and accurate. However, because it still relied on back EMF, standstill operation was impossible. And, the position control of IPMSM could not be achieved with EEMF concept. For sensorless drive, the high-frequency signal injection method exploiting inherent saliency of IPMSM has been continuously developed for last 10 years and applied to various industry fields, where torque control at standstill is essential. Its performance has been improved but there are still many problems to be solved. In the present, the square-wave signal injection at estimated d-axis has improved the control performance conspicuously. However, there are strong demands to improve the control performance of sensorless drive, yet. Based on the problems in the present, in this paper the possible developments of sensorless drive of IPMSM in next 5 years are enlightened as the future of sensorless control.