The whole cycle conduction braking, renewable
energy feedback caused by bus voltage pumping, beyond
the scope of security devices to withstand, also larger
charging current may also cause damage to the power
electronic devices, reduce the reliability of the system,
and the application of zero voltage to maintain the
opening of the method can effectively restrain the bus
voltage pump and reduce the peak of the charging current,
although the braking time has increased, but still can
achieve the purpose of rapid braking. and if this method is
used at low speed, the counter electromotive force is
small, so that the braking torque current is small, which
can not generate enough braking torque. Therefore in the
high-speed state, using the angle position control
combined with zero voltage to maintain the three step
method.