Showing papers by "Pragasen Pillay published in 1990"

Control characteristics and speed controller design for a high performance permanent magnet synchronous motor drive

Abstract: The theory of vector control is applied to the nonlinear model of a permanent magnet synchronous motor to develop a linear model for controller design purposes. The operation and relevant mathematics of a pseudo-derivative feedback controller are presented. Controller designs for three different speeds are then considered, and a comparative evaluation is made on the basis of their large and small-signal behavior. In order to test the large-signal response, the detailed nonlinear model of the machine and a real-time model of the inverter switches are used. Results indicate that a critically damped design done so as to ensure that all control and power signals never saturate gives an extremely poor result. Much better small and large-signal responses are achieved by avoiding this constraint and using Zener diodes instead to limit the commanded input into the inverter. Two designs using this technique are presented, an underdamped design with low speed overshoot and an overdamped design with no speed overshoot. The response of the underdamped design was much quicker than that of the overdamped. However the overdamped design has application when speed overshoot is intolerable. >

A computer program to predict the performance of slip energy recovery induction motor drives

Abstract: Details are provided, in the form of a flowchart, to permit the reconstruction of a computer program to predict the transient and steady-state performance of slip energy recovery induction motor (IM) drives. Slip energy recovery IM drives are different from most other drives in that the inverter is generally connected only after the machine has reached a predetermined speed. The initial conditions of the inverter are therefore nonzero and difficult to obtain. Three techniques that can be used to calculate the initial conditions are discussed. Theoretical predictions are supported by practical results. >

Design and evaluation of current controllers for PMSM drives

Abstract: PM synchronous motors (PMSMs) can achieve the servo performance characteristics of DC machines. This requires the PMSM to be vector controlled with additional tight current control. An experimental evaluation of hysteresis, delta comparison ramp comparison, and space vector current controllers is made, for which circuits are given. >

DSP-based vector and current controllers for a permanent magnet synchronous motor drive

Abstract: The design of DSP-based vector and current controllers for a permanent magnet synchronous motor (PMSM) drive is presented. Several different implementations of the vector controller are evaluated, and the consequent effect on the maximum motor speed is examined. A careful choice of the cosine look-up table which is used in the vector controller is presented. The possibility of implementing a hysteresis current controller algorithm using the DSP is also evaluated. The layout of a PC board including the DSP the DSP chip, latches, and PAL chips to decode the I/O ports is included as well. Experimental results are provided. >

Speed controller design for a vector-controlled permanent magnet synchronous motor drive with parameter variations

Abstract: When classical techniques are used for designing fixed-structure speed controllers for AC drives, the design is normally done around a nominal value of the controlled plant. Generally, a sensitivity analysis is subsequently done to ensure that the design specifications are met when the plant parameters change. An alternative is proposed where the parameter variations are included at the outset of the design task. The Nichols chart lends itself rather well to this application since it represents both magnitude and phase information on a single diagram. By using this alternative, it may be possible to reduce the overall time needed to complete the design. The particular technique, quantitative feedback theory (QFT), is used in conjunction with the Nichols chart. The basics of QFT are presented, and it is shown how it can be used for the design of fixed-structure controllers for parameter-sensitive plants. A design is presented and verified experimentally. >

Induction motor performance when fed from single to three phase converters

Abstract: The most popular single-to-three-phase converter consists of a capacitor connected between the motor's third phase and either the live or neutral of the single-phase supply. Proper voltage balance at any one given operating point is obtainable with the autotransformer-capacitor converter (ACC), while proper balance over the entire operating range is obtainable with a variable-inductor-variable-capacitor converter (LCC). The appropriate vector diagrams of the above-mentioned converters are developed to provide insight into their operation. An assessment of the derating necessary in the presence of unbalanced voltages and currents is presented. A technique for the measurement of the negative sequence voltage is discussed. Measured results for the case when an induction machine starts directly off a three-phase supply and off the above converters are included. >

Systematic design of a permanent magnet synchronous motor drive

Abstract: Permanent magnet synchronous motors (PMSMs) operate at a high power factor, efficiency, and reliability. To achieve the performance of DC machines, the PMSM drive is vector controlled. Such a drive is described. The instantaneous position of the rotor is used to determine the required currents which the controller forces into the motor. The actual current is compared to the required or commanded current, and hysteresis or ramp comparison current controllers are used to force the actual current to follow the commanded. Detailed circuits and experimental results are provided. Operation in the flux weakening region is also shown. >

Start-up torque improvement of permanent magnet synchronous motors

Abstract: The transient behavior of a permanent magnet synchronous motor is analyzed, and a method is proposed to improve its starting performance. Three banks of capacitors are connected in series between the three-phase source and the motor. A stability analysis is performed to demonstrate that a range of capacitance exists that is useful for improving the motor dynamics. Motor line starting is analyzed using the calculated value of capacitance, and several simulation and experimental runs are discussed. >