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Fusion of Neural Networks, Fuzzy Systems and Genetic Algorithms: Industrial Applications
by Lakhmi C. Jain; N.M. Martin CRC Press, CRC Press LLC ISBN: 0849398045 Pub Date: 11/01/98 |
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With these space vectors, the XSVM can be realized. Basically, the converter state is selected applying the following set of rules.
where,
Figure 10 a) Complex plane zones defined by the converter. b) Space vectors Vx and Vy during commutation instant, i.e., Il is out of Irefs error zone.
This controller is in charge of the converters input line currents. It has a single objective which is to reduce the input currents harmonic distortion. To accomplish this goal it must keep the magnitude of the input harmonic currents restrained to a specified maximum. This is done by appropriately choosing the next converter state using the XSVM technique presented in Section 4.
The controller acts, just as the loads line current controller, upon reception of the order coming from the fuzzy controller. Once that this controller has decided that the input port has higher priority, it will pass command of the converter to the inputs line current control. After the decision has been made, the input controller will select the converter state that will reduce the converters input current distortion, which also improves the converters power factor.
The input current control requires measurement of the input and output line currents, and the input voltages in order to select the next converter state according to the controls objective. The output line currents and input phase voltages are already measured by the loads line current control, thus leaving only the input line currents Iin unknown. These are obtained by software waveform reconstruction, using the converters current transfer function Hi for this purpose. The actual operation is shown in (31).
The converter input currents are also pulse-like waveforms, just like the output line voltages of the converter, therefore, they require filtering in order to produce a space vector with constant magnitude when transformed using Parks matrix. Taking advantage of the design characteristics of digital filters, two digital IIR filters are employed, a low pass filter and a band pass filter tuned to pass from the 3rd to 19th harmonic currents. With them the input line currents Iin are filtered, obtaining the filtered input line currents Iinf and Ih of the converter. The filtered waveforms are then used to obtain two current space vectors (17) and (32).
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