conjunction with pulsewidth modulation (PWM) to implement
an effective braking control. However, with the low speed of the
BLDC motor, the winding back EMF cannot reach the voltage
across the battery.Moreover, the recovery of energy also cannot
be achieved. Due to the presence of inductances in motor windings,
these inductances in the motor can constitute the boost circuit.
In order to achieve the recovery of energy, we have to raise
the voltage on the dc bus through the inductor accumulator. We
turn off all MOSFET on the high arms of H-bridge and control
the low arms of H-bridge with PWM. Fig. 5 shows the phase relation
among the back EMF, the armature current of the BLDC
motor, and the switching signals for the bidirectional dc/ac
converter, in which there is only one power switch operated
within each commutation state. By controlling MOSFET, the
whole circuit constitutes a boost circuit. The equivalent circuit
of each commutation state [7], [17] is shown in Fig. 6.
According to the principle of the volt-second balance, one
can conclude that the net change in the equivalent inductor
voltage vL is zero over one electric cycle, i.e.,