Join Date: Aug 2018
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 199 Post(s)
A six-step control  is implemented in order to provide theThe behavior of the drive electronics timing could cause unexpected and quite possibly disappointing results even (or perhaps especially) when told a lie about RPM. But it's sure tempting to find out.
maximum efficiency and performance under the voltage constraint at
high speed operating conditions. Based on the torque demand (Te*)
and the operating condition (motor speed Nr* and inverter input
voltage Vdc) as shown in Fig. 14, the control command look-up table
(LUT) determines the operating current command vector Is**. Also
the same information is used to look up the control mode (SVPWM
vs six-step) and the modulation index reference MI* from the table.
The outputs are fed to the voltage controller along with the feedback
modulation index MI from the voltage output of the current
controller. The voltage controller is to limit the fundamental output
voltage of the inverter, and adjusts the reference current vector for the
current control via ΔIs, which results in the final current command
vector Is* for the current controller core. The output of the current
controller is the output voltage vector Vs**, which is later limited by
the Voltage Limit, to output voltage vector Vs*. The difference
between the unlimited and limited voltage is multiplied by the
anti-windup gain Ka. For space vector pulse width modulation
(SVPWM) mode, Ka is set such way that the integrator windup is
avoided. When the control mode is set to the six-step control mode,
Ka is set to zero to induce the windup phenomenon of the integrators.
This allows the output voltage magnitude to be saturated in the
integrator, and provides the natural transition of the current control
from the normal field-weakening control to the six-step control
without a need for the separate controls. The output voltage vector
Vs* is fed to the pulse width modulation module, which selects the
actual modulation method based on the modulation index and the
control mode commands from the current and voltage control.