Page 361 - Power Electronics Handbook
P. 361

Inverter control circuits   35 1

                    Frequency   Harmonic   Voltage
                    control    mntrol     control

                      Pulse      Delay    pulsewidth   Sequencer   Drive   lnvyler   Load
                      generator --+   3  control   -+      + circuit  --.  swtches  3




                                                      Voltage and current

                    Figure 13.66 Control system for obtaining selected harmonic reduction in the output voltage
                    of an inverter

                    varied so  as to produce a series of  pulses spaced at the required distances
                    apart, to eliminate a given harmonic in the output voltage. The magnitude
                    of the fundamental voltage in the output is altered by controlling the width
                    of  the pulses. As before, sequencing is needed to drive the correct power
                    switches in  the inverter and drive circuits to  provide  the drive power.
                    Voltage  and  current  feedback  can  be  used  to  sense  and  adjust  the
                   magnitude of  the load voltage and therefore the current.
                      Figure  13.67 shows a  high-frequency pulse-width modulation  control
                    system, which gives the waveforms illustrated in Figures 13.37, 13.40 or







                    Frequency 4 mr          I


                    control   and     Wwok         Voltape and current

                    Figure 13.67 Control system for high-frequency pulse-width modulation of an inverter output
                    voltage


                                                          Sequencer   We.   Inverter
                                                                   circuit  1 switches
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