Signal Injection Method Research Articles

A faulty feeder selection method for SLG faults based on active injection approach in non-effectively grounded DC distribution networks

Identifying single-line-to-ground faults in non-effectively grounded DC distribution networks is challenging because the fault current is fleeting in the transient stage and negligible in the fault steady stage. First, an active signal injection method is proposed to inject signals into the DC network after the fault occurs. And the fault characteristics of the zero-mode fault circuit including the injected signal are analyzed. Second, a zero-mode parameter identification algorithm is proposed to calculate the length of each feeder based on the injected signal in the fault steady stage. It is found that the calculated length of the healthy feeder corresponds to its actual length, but the calculated result of the faulty feeder is the opposite of the total length of all healthy feeders. Finally, a faulty feeder selection method based on the polarity of the calculated length is proposed. The simulation results shown that the method can select faulty feeders under conditions of up to 5000 Ω transient resistance and 20 dB noise.

Optimization Design of Variable Reluctance Resolver Based on Three-phase Symmetrical Winding

Optimization Design of Variable Reluctance Resolver Based on Three-phase Symmetrical Winding

MTPA Control for DC-Biased Hybrid Excitation Machine Using MTPA Control Law and Virtual Signal Injection

This paper proposes an overall maximum torque per ampere (MTPA) control for dc-biased hybrid excitation machine (dc-biased HEM) using MTPA control law and virtual signal injection. The mathematical model of the machine is first analyzed in synchronous rotating reference frame. According to the characteristic of the mathematical model, a control strategy is proposed and consists of two parts, i.e., an MTPA control law and a virtual dc-biased signal injection. The MTPA control law is employed to calculate the dominant current references while ensuring the rapid dynamic performance. The virtual dc-biased signal injection method is a correction scheme for MTPA current deviation caused by parameter variations. Unlike conventional signal injection techniques, this signal injection method considers the nonlinearity of inductance and does not involve any filters. Thus, it can extract MTPA criterion more accurately and easily. In general, simulation and experimental results validate that the control strategy combined with MTPA control law and virtual signal injection can achieve accurate MTPA operation and rapid dynamic magnetization capability for the dc-biased HEM in real time.

Measurement of impedance angle for anti-islanding protection in multi-source distribution network

With the increase of the proportion of distributed generators (DGs) access in the distribution network, it transforms from a traditional radial network to a multi-terminal active network, which brings many challenges to relay protection. If part of the distribution network is disconnected from all upstream networks, it can create unplanned islands that can compromise personal safety, power quality, and out-of-phase reclosing. As a result, it is essential to equip DGs with anti-islanding protection. Currently, anti-islanding protection based on impedance measurement is of great interest because it has the lowest risk of rejection and misoperation. However, in multi-source distribution networks, signal interference can lead to protection failure. In light of this, we proposed an impedance angle measurement anti-islanding protection based on voltage synchronous injection, where each DG uses the bus voltage as a reference to achieve synchronous injection of the islanding detection signal. The measured impedance angle was then used to identify the state of islanding operation. Combining the analyses of line impedance, injected signal frequency and other relevant factors, an impedance angle based islanding identification criterion is proposed. Furthermore, the realization method of signal injection and impedance angle detection in combination with the DG control strategy was presented. Finally, real-time digital simulation (RTDS) experiments show that the proposed method can accurately identify islands under zero power mismatch conditions and independent of grid disturbances.

Improved Sensorless Control Strategy for IPMSM Using an ePLL Approach With High-Frequency Injection

This paper proposes an improved sensorless control strategy for interior permanent magnet synchronous motor (IPMSM) using high-frequency (HF) rotating signal injection method in the stationary reference frame. Conventional HF rotating signal injection methods face the problems of long convergence time and poor stability, due to the filters used in signal demodulation process. Therefore, an improved signal demodulation algorithm based on an enhanced phase-locked loop (ePLL) is proposed in this paper. This method improves the stability and dynamic response of the system by eliminating additional filters and reducing the resulting delays. This ePLL, in addition to estimating the phase angle of sinusoidal signal, which contains the rotor position inside it, estimates its amplitude. It is shown that the proposed method has a high robustness against the uncertainties of the motor inductances. The proposed sensorless control method is verified by experiments on a 1.8-kW IPMSM drive platform.

Variable-Angle Random High-Frequency Voltage Injection Strategy with Cross-Saturation Effect Compensation for Sensorless Synchronous Reluctance Motor Drives

There are usually noise problems when the position sensorless control of a synchronous reluctance motor (SynRM) is carried out by high-frequency (HF) signal injection method. Due to the special structure, the cross-saturation effect of the SynRM is particularly serious, resulting in reduced position observation accuracy. In this paper, a variable-angle random HF voltage injection strategy with cross-saturation effect compensation is proposed for position sensorless SynRM drives. Random number generation based on the chaotic mapping method is used to generate random HF voltage signals with different frequencies for injection; the current power spectral density (PSD) distribution is extended and the HF noise can be reduced. A control strategy based on variable-angle square-wave injection is proposed to suppress the cross-saturation effect. By measuring the position error curves of different loads off-line and polynomial fitting the curves, the position error is achieved by combining with the corresponding signal demodulation algorithm. The proposed method does not require additional hardware resources and can maintain high control accuracy and robustness. Finally, the effectiveness of the proposed sensorless control strategy is verified on a 3 kW SynRM experimental platform.

An Incorporated Power and Data Synchronous Transmission Method for SRG Integrated Wind Power Generation Systems

Reliable communication places important roles in renewable generation for operating status monitoring, fault alarming, cooperative control and so on. For existing power and data synchronous transmission strategies applied to switched reluctance generator (SRG) systems, the communication rate is limited by very low power switching frequencies. Hence, in this paper, a new PDST strategy is proposed and implemented in an SRG integrated wind generation system by incorporating power and data composite modulation method with signal injection method. For lower signal band, the data is modulated together with power by regulating the lower power switch of each phase in a fixed interval with given frequency, and for the higher signal band, the data in form of voltage ripple is injected into the bus by a coupling circuit. Therefore, specific voltage ripples with different given frequencies can be embedded into the power line for carrying signals, and the frequency band of signal bus can be well exploited. On signal receiver end, the voltage ripples are sampled and analyzed by fast Fourier transform method for demodulating the transmitted data. The feasibility of the proposed incorporated data transmission method is verified by experimental testing.

Speed Estimation of Induction Motor at Low and Zero Speed using High Frequency Signal Injection for Rotor Slot Harmonics Detection

Rotor position estimation based on high frequency signal injection method represents the interesting way to provide the high performances of the AC drives sensorless controlled at low or near zero speed range. So, this method requires the existence of saliencies inside the IM particularly the presence of the slots where their design constitutes the main advantageous to exploit its effect for rotor speed monitoring. First, the present paper exposes a model of the induction machine including slotting effects which it can be exploited in order to extract the harmonic saliency created by rotor slotting. Second, the high frequency signal injection method is used in order to allow tracking the characteristic harmonic saliency due to rotor slotting from which the rotor position and speed may be estimated. A High frequency voltage signal injection creates a high frequency current modulated by the saliencies presented inside the machine. To extract information about rotor position, the resulting stator current treads to heterodyning process to eliminate the disturbance components and subsequently the rotor position may be extracted by a closed-loop observer. Simulation results are shown in order to verify the validity of the proposal and to confirm the effectiveness of estimation method at zero frequency.

Displacement sensorless control of a bearingless induction motor based on modified high-frequency signal injection

ABSTRACT To enhance the rotor radial displacement identification accuracy of a bearingless induction motor (BIM) in displacement sensorless control, a displacement sensorless control strategy based on modified high-frequency signal injection is proposed. Firstly, a BIM flux linkage equation is analyzed, and by integrating the principle of the conventional high-frequency signal injection method, a self-detection model for the BIM rotor radial displacement is established. Secondly, a cascade notch filter and a low-pass filter are used in the signal demodulation process of the modified high-frequency signal injection. This strategy enables the DC component relevant to rotor displacement to be extracted from the high-frequency current，and obtains the rotor radial displacement equations. Finally, compared with the conventional high-frequency signal injection control, the proposed BIM displacement sensorless control system based on the modified high-frequency signal injection has higher displacement identification accuracy under different operation conditions, such as no-load, sudden load, and radial displacement mutation, as shown in simulation and experimental results. Overall, the motor performs well in terms of speed and suspension.

An Amplitude-Adaption High-Frequency Signal Injection Method for SynRMs at Zero-Low Speed

An Amplitude-Adaption High-Frequency Signal Injection Method for SynRMs at Zero-Low Speed

The Analysis of Capacitance Current Testing Method

The accuracy of capacitance current measurement is directly related to the choice of arc suppression coil. In this paper, the capacitance current test of 10 kV and 66 kV substations in Shenyang and Dalian is carried out by using a capacitance current tester produced by different manufacturers. The measurement mainly uses the 10 kV PT open triangle signal injection method (for 3PT), 10 kV 4PT secondary signal injection method (for 4PT), and 66/10 kV transformer neutral signal injection method. The test data are compared with the test data of laboratory standard equipment. Through comparative analysis, it can be seen that some manufacturers failed to measure capacitive current or the deviation of test results is large, and the test results of each test method of other manufacturers are closer to the measured values in the laboratory.

Improved Parameter Identification of SPMSM Using High-Frequency Signal Injection Methods at Standstill

Improved Parameter Identification of SPMSM Using High-Frequency Signal Injection Methods at Standstill

Rotor Position Estimation Based on Low-Frequency Signal Injection and Estimated Main Field Current for Wound-Field Synchronous Starter/Generator in the Low-Speed Region

Due to reliability problems of mechanical position sensor, rotor position estimation technology is an alternative for the starting control of aircraft wound-field synchronous starter/generator. Reversible saliency and high frequency attenuation characteristics of main machine (MM) may lead to the failure of existing high-frequency signal-based estimation methods. In this paper, low-frequency signal (LFS) injection and novel signal extraction method are combined to estimate rotor position. Firstly, LFS is injected in MM's stator winding, and response signal containing rotor position information is induced in its rotor field winding. Then, the response signal can be extracted from the estimated main field current (EMFC) by band-pass filter. Further, the phase of extracted signal and injected LFS are obtained by two single-phase phase-locked loops (PLL) respectively. Then, the increment of rotor position can be obtained by the two PLLs. Meanwhile, by injecting a specific low frequency square wave, initial rotor position can also be extracted from EMFC, requiring no extra pole identification and phase compensation. Finally, combining initial rotor position and position increment, continuous rotor position of MM can be obtained. Effectiveness of the proposed method are verified by experiments.

Enhanced Linear ADRC Strategy for Sensorless Control of IPMSM Considering Cross-Coupling Factors

Estimation of rotor coordinate system by high-frequency (HF) signal injection is an effective sensorless control strategy, which can solve the decoupling problem of position information of interior permanent magnet synchronous motor (IPMSM) in the low-speed range. However, the inductance cross-coupling phenomenon caused by magnetic saturation will lead to a decline in the accuracy of rotor angle extraction, resulting in a serious deterioration of the sensorless control performance. To solve this problem, an HF signal injection method considering <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d-q</i> axis coupling inductance is proposed to estimate HF inductance and the rotor angle. The estimated HF inductor combined with the current loop enhanced linear active disturbance rejection control (ELADRC) is used in the current loop control to estimate the disturbance and improve the current regulation quality of the current control system. Furthermore, the stability and the tracking performance of the enhanced LADRC are analyzed theoretically. Finally, the stability of a closed-loop IPMSM drives system based on ELADRC considering HF inductance is analyzed. The experimental results of a salient pole IPMSMs driver verify the effectiveness and practicability of the scheme.

Speed Regulation and Optimization of Sensorless System of Permanent Magnet Synchronous Motor

Aiming at the problems of speed overshoot, slow convergence and poor anti-interference in the control of permanent-magnet synchronous motors (PMSMs) without a position sensor, a pulse vibration high-frequency signal injection method for a permanent-magnet synchronous motor with an improved sliding mode control was designed. Firstly, the improved approach rate function is combined with the improved non-singular fast terminal sliding mode surface to design the non-singular fast terminal sliding mode controller (NFTSMC), which is used in the speed loop to improve the speed convergence ability and reduce its overshoot. Secondly, in order to eliminate the influence of the band-pass filter on the system bandwidth in the traditional high-frequency injection method, a pulse vibration high-frequency signal injection method that injects high-frequency voltage signals and synchronous current signals into the d^ axis of the estimated two-phase rotation coordinate system d^q^ and the αβ axis of the two-phase stationary coordinate system αβ was designed to estimate the motor position and speed to achieve sensorless control. Finally, the above control strategy was compared with the speed loop PI and the traditional sliding mode controller (SMC) of the speed loop, respectively. The simulation and experimental results show that whether it is a no-load variable speed or fixed speed loading, the above control strategy can effectively reduce the speed overshoot, accelerate the speed convergence and improve the load capacity of the system.

Position Detection and Speed Recording Method for Power-Off IPMSM in Full-Speed Range Based on Ultrahigh Frequency Signal Injection

For the sensorless interior permanent magnet synchronous motor (IPMSM), this letter proposes a rotor position and speed recording method applied in full-speed range after the main power supply (MPS) is OFF. The proposed method injects ultrahigh-frequency (UHF) sinusoidal voltage into the motor windings after the motor is powered off, and then calculates the motor rotor position and speed in real time by detecting the RMS value of the UHF sinusoidal signals. Based on the UHF signal injection method designed for the low-speed region, this letter improves the injection and detection timing and optimizes the online calculation method of rotor position and speed. The proposed method can work only when there is no power supplied to the motor, and it is used solely for the purpose of recording. This letter implements the first inductance-based full-speed motor power-off rotor position detection and speed calculation. It breaks the cognitive limitation that the inductance-based rotor position detection method is only applicable to the low-speed region.

Comparative Study of Magnet Temperature Estimation at Low Speeds Based on High-Frequency Resistance and Inductance

Interior permanent magnet synchronous motors have been widely used in electric vehicles. These motors employ Nd-Fe-B as the permanent magnet, which is vulnerable to temperature variations. Moreover, some features of Nd-Fe-B magnets are related to temperature, which can affect motor characteristics. Therefore, magnet temperature is an important parameter and methods for estimating it have been developed. In particular, a signal injection method has been developed for low-speed regions. In this method, two parameters are employed: high-frequency resistance and high-frequency inductance. In this paper, these two methods are compared to determine which parameter is more appropriate for estimations at low speeds and to reveal whether signal injection methods can be applied to the standstill condition. The comparison indicated that the high-frequency inductance-based method has a stronger correlation with the magnet temperature at low speed and standstill conditions than the high-frequency resistance-based method.

An Online Monitoring Method for Low-Frequency Dielectric Loss Angle of Mining Cables.

The dielectric loss angle can better reflect the overall insulation level of mining cables, so it is necessary to implement reliable and effective online monitoring of the dielectric loss angle of mining cables. In order to improve the monitoring accuracy of the dielectric loss angle tan δ of mining cables, a low-frequency dielectric loss angle online monitoring method combining signal injection method and double-end synchronous measurement method is proposed in this paper. Firstly, the superiority of the low-frequency signal in improving the detection accuracy of dielectric loss angle is explained, and the feasibility of the low-frequency signal injection method is analyzed. Secondly, the cable leakage is calculated using the double-terminal synchronous measurement method to measure the core current at the first and last ends of the cable, and the phase sum of the voltage at the first and last ends is selected as the reference phase quantity to realize the effective calculation of the dielectric loss angle tan δ of the cable. Then, the simulation model for online monitoring of dielectric loss angle of mining cable is built, and the feasibility of the online monitoring method proposed in this paper is verified by combining the simulation results. Finally, the theoretical and simulation analysis of the monitoring error of dielectric loss angle of mining cable is carried out.

Implementation of a new flux rotor based on model reference adaptive system for sensorless direct torque control modified for induction motor

Introduction. In order to realize an efficient speed control of induction motor, speed sensors, such as encoder, resolver or tachometer may be utilized. However, some problems appear such as, need of shaft extension, which decreases the mechanical robustness of the drive, reduce the reliability, and increase in cost. Purpose. In order to eliminate of speed sensors without losing. Several solutions to solve this problem have been suggested. Based on the motor fundamental excitation model, high frequency signal injection methods. The necessity of external hardware for signal injection and the adverse influence of injecting signal on the motor performance do not constitute an advantage for this technique. Fundamental model-based strategies method using instantaneous values of stator voltages and currents to estimate the rotor speed has been investigate. Several other methods have been proposed, such as model reference adaptive system, sliding mode observers, Luenberger observer and Kalman filter. The novelty of the proposed work consists in presenting a model reference adaptive system based speed estimator for sensorless direct torque control modified for induction motor drive. The model reference adaptive system is formed with flux rotor and the estimated stator current vector. Methods. The reference model utilizes measured current vector. On the other hand, the adjustable model uses the estimated stator current vector. The current is estimated through the solution of machine state equations. Practical value. The merits of the proposed estimator are demonstrated experimentally through a test-rig realized via the dSPACE DS1104 card in various operating conditions. The experimental results show the efficiency of the proposed speed estimation technique. Experimental results show the effectiveness of the proposed speed estimation method at nominal speed regions and speed reversal, and good results with respect to measurement speed estimation errors obtained.

Multi-Optimization Objective Online Tracking-Based Parameter Self-Tuning Method for Sensorless PMSM Drives

It is important to optimize control parameters for the high-performance operation of position sensorless permanent magnet synchronous motor (PMSM) drives. In this article, a multi-optimization objective online tracking (MOOT)-based parameter self-tuning method is proposed to improve the sensorless control performance when the high-frequency signal injection (HFSI) method is used, which involves both offline and online stages. By the parameter self-learning and the model analysis, the injection signal, the position observer, the speed, and current regulators are preliminarily designed offline to ensure that the system can start smoothly. Based on the parameter characteristics analysis, an adaptive law with the speed ripple and torque ripple as the optimization index is designed to realize the online tracking of control and observation parameters. To solve the issues of tuning delay and mistuning, a moving window-based error detection strategy is investigated, which improves the parameter self-tuning speed and accuracy. The proposed method can improve the steady- and transient-state performance and realize the sensorless debug-free operation for HFSI-based method. The effectiveness is verified by experiments on a 2.2-kW PMSM drive platform.