POLITECHNIKA WARSZAWSKA

4. ANN based Current Controllers (CC)
AC power supply/UPS:
narrow range of output frequency (UPS), reduced harmonic content (output filter),
fault protection.
- VS PWM line rectifiers and active filters:
constant AC side (line power) frequency 50/60Hz nearly constant amplitude and
waveform of AC side voltage, poorly damped AC side network, variable DC link
voltage (power filter).
The evaluation of CC may be done according to performance criteria which
include static and dynamic performance. Table 4.1 presents the static criteria in two
groups:
- those valid also for open loop voltage PWM (see e.g. [1,8,9,16])
- those specific for CC-PWM converters based on current error definition (denoted •).
The following parameters of the CC system dynamic response can be considered:
dead time, settling time, rise time, time of the first maximum and overshoot factor.
The foregoing features result both from the PWM process and from the response of
the control loop. For example, for dead time the major contributions arise from signal
processing (conversion and calculation times), and may be appreciable especially if
the control is of the digital type.
Table 4.1
Performance Criteria
CRITERIA DEFINITION
RMS = [1/T∫(ε α
2 + εβ 2 )dt] 1/2
J = 1/T∫[(ε α
2 + εβ 2 )] 1/2 dt
N = Σ imp⎪t ∈ 〈0,T〉
I hrms = [1/T∫(i (t) - i 1(t) ) 2 dt] 1/2
COMMENTS
the r.m.s. vector error
the vector error integral
number of switchings
(also for nonperiodical)
the r.m.s harmonic current
d = I hrms / I hrms six-step the distortion factor
d = [Σ h 2 i (k⋅f1 )] 1/2 k≠1 synchronised PWM case
d = [∫ h d
2 (f) df] 1/2 f≠f 1
nonsynchronised PWM case
h i (k⋅f 1 )- discrete current spectra
h d (f) - density current spectra
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