Standard Dq Research Articles

An αβ-Frame Moving Average Filter to Improve the Dynamic Performance of Phase-Locked Loop

The moving average filter (MAF) is one of the most widely used methods to block harmonics in a phase-locked loop (PLL). This paper proposes a simple structure for MAF to work directly in the $\alpha \beta $ -frame (called $\alpha \beta $ MAF). Compared with the standard dq -frame MAF ( dq MAF) used as an in-loop filter, $\alpha \beta $ MAF acts as a prefilter and significantly improves the PLL dynamic response. Its derivation process and implementation is described in detail in both continuous and discrete time domains. In an adaptive prefilter-based PLL, a frequency feedback loop (FFL) is indispensable, but it is not easy to design. Therefore, nonadaptive $\alpha \beta $ MAF is suggested, and a corrector is added to eliminate the phase error at off-nominal frequencies. In this paper, the small signal model of the proposed PLL is carried out through the perspective of frequency shift, which simplifies the derivation process. The effectiveness of the proposed technique is confirmed through simulation and experimental results.

Detailed Analytical Modeling of Fractional-Slot Concentrated-Wound Interior Permanent Magnet Machines for Prediction of Torque Ripple

Electromagnetic torque in interior permanent magnet machines is a function of their inductances and permanent magnet (PM) flux linkages, which are assumed sinusoidal in the standard dq model of the machine. This assumption is flawed when a fractional-slot concentrated-wound stator is utilized, because its nonsinusoidal winding function leads to harmonics in the machine parameters. In order to address this deficiency, the nonsinusoidal machine parameters are modeled in this paper, based on which, a modified extended dq model is proposed. The harmonics in the machine parameters are included in the proposed modified extended dq model and their effects on the machine operational characteristics are accounted for. Detailed equations for the average torque and torque ripple are then derived based on the proposed modified extended dq model. Experimental tests are also described for the measurement of the proposed modified extended dq model parameters. The estimated torque and torque ripple by the proposed model are validated through experimental tests on a prototype fractional-slot concentrated-wound interior permanent magnet machine.

Joint Identification of Stepper Motor Parameters and of Initial Encoder Offset

The paper presents a new procedure to identify at the same time the electrical parameters of a permanent magnet stepper motor (PMSM) and the initial offset of an incremental encoder. The model considers effects due to the permanent magnet and to variable reluctance, and the resulting theory is applicable to cases where both or only one of these terms is present. The standard DQ model of PMSM's assumes that the permanent magnet is lined up with a winding when the position is zero. When an incremental encoder is used, an initialization procedure is required to zero the initial offset. In contrast, this paper computes a transformed model that accounts for the initial offset. then develops a least-squares identification algorithm that estimates the machine's electrical parameters together with the offset angle. Experiments show that the estimation procedure and a closed-control method using the estimated offset perform similarly compared to when the offset is reset to zero using an initilization procedure.

Sliding Mode Control of a Stand-Alone Wound Rotor Synchronous Generator

This paper presents a sliding mode control for a wound rotor synchronous machine acting as an isolated generator. The standard dq model of the machine is connected to a resistive load. A switching function is defined in order to fulfill control objectives, and the ideal sliding dynamics is proved to be stable. From the desired surface, the standard sliding methodology is applied to obtain a robust and very simple controller. Numerical simulations and experimental results validate the control law and show good performance and a fast response to load and reference changes.

Online cage rotor fault detection using air-gap torque spectra

This paper discusses use of air-gap torque spectra as a means of identifying faults in cage rotors. Being dependent on both stator and rotor currents, the torque is very sensitive to faults in the rotor. Through a comparative study using a detailed machine model and the standard dq model, the paper shows that the characteristic frequencies generated by a particular fault are preserved even if the standard dq model is used for estimation of air-gap torque. This is validated through a practical hardware implementation for online spectrum estimation of air-gap torque using TMS320C31, where several faulted cage rotors were used for study.

Online Cage Rotor Fault Detection Using Air-Gap Torque Spectra

This paper discusses use of air-gap torque spectra as a means of identifying faults in cage rotors. Being dependent on both stator and rotor currents, the torque is very sensitive to faults in the rotor. Through a comparative study using a detailed machine model and the standard dq model, the paper shows that the characteristic frequencies generated by a particular fault are preserved even if the standard dq model is used for estimation of air-gap torque. This is validated through a practical hardware implementation for online spectrum estimation of air-gap torque using TMS320C31, where several faulted cage rotors were used for study.