The third stator current signal is inferred, since all three stator currents sum to zero. When QA is turned off the winding current "free wheels" through lower inverter diode, DAP, and connects the winding "a" to the -V bus power rail. However, the advent of low cost microcomputers has increasingly led to the implementation of the control and user interface functions by digital means.
The control loops in these systems were first implemented Dsp based ac dc converter analog components. The ac motor control system calculates the two quadrature voltages, Vd and Vq, required to force the Iq current to directly follow the torque demand and the Id current to maintain a constant rotor field.
The resultant active low PWM signals, shown in figure 4 care complementary timing wave forms with a short "dead" time between the active portions. An embedded control sequencer decodes the chip-select line, Read- and Write lines, and 4 address lines and maps these data registers directly into the DSP memory address space.
The ADMC motion coprocessor has three principal functional blocks: The end of Dsp based ac dc converter can be programmed to generate an interrupt pulse for the DSP, which can read the results registers in any order.
Figure 4 The ac servo system described above can be built using three principal control components. The Vd and Vq outputs of the calculation are then transformed in the vector-transformation block to digital equivalents of the three-phase stator voltages, Va, Vb and Vc, for driving the motor.
The ADMC provides the required interface functions between a DSP controller and the three phase inverter; it is suitable for use in controlling both permanent-magnet ac motors and ac induction motors.
The output of this loop is a demand for an increase or decrease in motor torque, which is fed to the inner current loop. A high Start-of-Conversion pulse acquires all four input channels and starts a conversion sequence for 2, 3 or 4 channels, depending on the control-register settings.
There are two current loops, a torque loop and a field loop, with proportional and integral compensation PI. The first instruction is to read the ADMC system status register, using a data-memory read instruction.
However, the current loop varies very much in sophistication depending on the motor type. But to control the torque in ac motors, the currents must be synchronized to the position of the rotating rotor field. Figure 2 Figure 3 shows an all-digital implementation of a control scheme for a permanent magnet ac servo motor.
The signals, described in Figure 5, are center based active-low signals so that the On low periods are symmetrical about the midpoint between timing pulses. The Analog Devices Motion Control Group has been the leading supplier of resolver-to-digital conversion products to the ac servo motor market for the last ten years.
Motor velocity is calculated from position measurements, using an estimation algorithm. The ADMC starts the reverse vector rotation, while the DSP may perform protection functions, such as overload detection or bus-voltage monitoring.
The control algorithm consists of a number of control laws and some reads and writes to ADMC data registers. An inverse transformation is then used to transform the "dc-motor" Vd and Vq voltages back to the stator reference frame to give the required winding voltages.
The device has 25 internal memory-mapped registers for storing the peripheral input and output data. The reverse transformation converts three-phase stator currents signals, Ia, Ib and Ic, to two orthogonal rotor referenced currents, Id and Iq.
The average stator winding voltage, VA, is proportional to the conduction period, tA, of power transistor, QA, and is given by: In dc motors the torque is directly proportional to the dc current in the armature windings.
The current loop generates signals for the power converter which supplies suitable motor currents to produce the desired output torque. This process Figure 2 results in two equivalent dc motor current quantities: The captured current signals represent the average winding current value since the sampling is at the mid-point of the current waveform.
In order to make the applied stator voltage independent of the stator current sense, the power transistor, QAP, is turned on when QA is turned off. The ADMC provides the analog acquisition system to capture the motor current or voltage signals, the vector processing functions which condition these signals, and the pulse width modulator required to control the power converter.
They can also be configured as interrupt sources for system-protection functions. Typically, op amps were used in the feedback compensation circuits, and comparators were used to generate the control signals for the switching power converter.
The 12 bit PWM block produces three pairs of constant-frequency variable-duty-cycle wave forms for the power converter switches, with a frequency ranging from 1. In this case, the winding voltage is a function of the conduction period of the diode DA.
The converted values are in a twos-complement format to match the fixed-point DSP processor. A companion oscillator IC, the AD2S99is used for resolver excitation and provides loss-of-signal detection.DSP-Based Modified SPWM Switching Technique with Two-Degrees-of-Freedom Voltage Control for Three-Phase AC–DC Buck Converter.
A DSP Based Controller for High Power Dual-Phase DC-DC Converters. Xin Guo, Xuhui Wen and Ermin Qiao Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China e-mail: [email protected] DSP and motor-control chips simplify DSP-based AC motor control hardware.
The A/D converter, based on a CMOS-compatible switched-capacitor technique, is an bit successive approximation device with a 4-channel simultaneous-sampling track-and-hold amplifier as its front end.
(ac currents and voltages) and the rotor (dc machine. A DSP-based probabilistic fuzzy neural network (PFNN) controller to control a two-stage ac–dc charger is proposed in this study. The charger is composed of an ac–dc boost converter with power.
DEVELOPMENT OF A TMSC30 DSP BASED CONTROLLER FOR A POWER CONVERTER S.A. Chickamenahalli, Rutledge Ellis interest in courses in digital signal processing in engineering technology curricula.
The The input bridge is an ac to dc pulse width modulated (PWM) rectifier. The. A DSP-based interleaved boost DC–DC converter for fuel cell applications.
this DSP-based DC–DC converter can be further improved by adding online fault diagnosis capabilities for reliability and durability of the stack. A. BakhshaiA new control approach based on the differential flatness theory for an AC/DC converter used in.Download