Page 235 - Modern Control of DC-Based Power Systems

Control Approaches for Parallel Source Converter Systems 199

Figure 5.64 Impact of measurement noise on V bus with H N control.

limited white noise source is low pass filtered to create the said pink
noise. Different noise sources are used for each primary controller and
then the bus voltage is observed. Remember that our control design has
good noise suppression abilities as seen from R. The noise sources of all
primary controllers are turned on simultaneously at time t 5 0.5 s. The
individual primary controllers are able to filter out the noisy inputs as
observed in Fig. 5.64. The blue waveform shows the corrupted bus volt-
age measurement of the first converter.

5.8 SLIDING MODE CONTROL
Sliding Mode (SM) controllers switch back and forth between two
control laws as a function of the state vector. Due to this switching sliding
states occur which have as an advantage the robustness of the control in
relation to parameter fluctuations of the plant. A disadvantage is the high-
frequency switching of the control element, which on mechanical
switches leads to additional wear and tear.
SM control provides an approach that complies with the nonlinear
nature of the switching-mode source power converters. In practice, the
converter switches are driven as a function of the instantaneous values of
the state variables in a way that forces the system trajectory to stay on a
suitable selected surface in the state-space known as the sliding surface or
manifold. SM was originally designed for linear plants where afterwards