Advanced Functions Control Loops; Current Loop; Speed Loop - Siemens SINAMICS PERFECT HARMONY GH180 Function Manual

NXGPro+ Control Description

4.8 Advanced Functions Control Loops

4.8 Advanced Functions Control Loops
The control includes three main control loops that are defined in the following sections.
4.8.1

Current Loop

The current loops form the innermost loop of the control system. It is essential that these loops
are stable for correct operation of the drive. When the current loop gains are very low, then the
drive output currents do not have a sinusoidal waveshape, i.e., dead-bands can be seen around
the zero-crossings, and the peaks are not smooth but appear flat. On the other hand, when
current loop gains are too high, then a high frequency ringing appears on the sinusoidal current
waveform. IOC trips can also occur if this is the case.
Default values of the current loop gains are sufficient for most applications. Tuning may be
required for high performance applications and when output filters are used. Refer to Section
Output Filters in Chapter Advanced Operating Functions for more information. Lower current
loop gains are recommended in synchronous transfer applications when the drive output
voltage capability is only a couple of percent higher than the utility or line voltage. This capability
is displayed as "Safe Voltage" on the debug screen.
4.8.2

Speed Loop

Control of motor speed is accomplished with the speed regulator. The output of the speed loop
forms the torque current command (I
motor and the load have similar inertia. Speed loop gains require tuning when its output shows
significant oscillations during small changes in speed command. In general, when this occurs,
reduce the integral gain first and then reduce the proportional gain.
Default values for the double speed Kf gain and the speed loop filter time constant are
sufficient. A value closer to 0.5 for the double speed gain allows reduced overshoot, while a
value closer to 1.0 makes the speed regulator a traditional PI regulator and could have more
overshoot.
For applications where the motor and load do not have similar inertia, adjustment of the default
settings is necessary, as in the following examples:
• ESP applications have motors with very low inertia. In such applications, the speed loop
proportional and integral gains can be safely reduced by a factor of 5 or more from their
default settings.
• Fan applications have motors with very high inertia. In such applications, the speed loop
proportional and integral gains are typically reduced by a factor of 2 to 5 from their default
settings. These applications, in general, do not require fast speed regulator response, and a
reduction in speed loop gains prevents large or sudden changes in the torque current
command.
60
). The default speed loop gains work well when the
qs,ref
NXGPro+ Control Manual
Operating Manual, A5E50491925A