Patent TW-202005249-A (TW)
Title: Improved quasi-Z-source inverter including a quasi-Z-source inverter circuit, an inductor-capacitor filter and a digital controller
Inventor: WANG SHUN-ZHONG
IPC: H02M7/48
Filed: 2018-06-01
Abstract: An improved quasi-Z-source inverter includes a quasi-Z-source inverter circuit, an inductor-capacitor filter and a digital controller. The quasi-Z-source inverter circuit has an input terminal, four control terminals and two output terminals. The input terminal is used for coupling with a DC voltage. The four control terminals are used for receiving four control signals to switch four switches for performing a commutation operation on the DC voltage, thereby generating a first AC voltage. The two output terminals are used to output the first AC voltage. The four switches include a first upper arm switch, a second upper arm switch, a first lower arm switch and a second lower arm switch. The inductor-capacitor filter is coupled to the two output terminals for performing a filtering operation on the first AC voltage, thereby generating a second AC voltage for supplying power to a load. The digital controller executes a firmware program including performing an incremental proportional-integral-derivative operation according to the second AC voltage and a desired AC voltage to determine a value of an amplitude modulation coefficient ma, where ma is a positive real number, and an initial value of ma is a preset value; generating a boost factor B according to the voltage of the Z impedance capacitor of the quasi-Z-source inverter circuit, and generating a zero-state conduction factor Bduty according to the boost factor B, where B and Bduty are positive real numbers, and Bduty=(1/2) * (1-1/B); and performing an improved space-vector pulse width modulation operation to generate the four control signals according to the amplitude modulation coefficient ma and the zero-state conduction factor Bduty. The improved space-vector pulse width modulation operation includes: when [theta] is between [0, [pi]], T2=T*ma*sin[theta], Tsh=Bduty*T, and T0=T-T2-Tsh; when [theta] is between [[pi], 2[pi]], T1=T*ma*sin([theta]-[pi]), Tsh=Bduty*T, and T0=T-T1-Tsh, where [theta] is a phase angle of the second AC voltage, T is a switching period of the four control signals; and when [theta] is between [0, [pi]], making (the first upper arm switch, the first lower arm switch, the second upper arm switch, and the second lower arm switch) present in order: continuous T0 / 4 (OFF, ON, OFF, ON) state, continuous Tsh/2 (ON, ON, OFF, ON) state, continuous T2/2 (ON, OFF, OFF, ON) state, continuous T0/2(ON, OFF, ON, OFF) state, continuous T2/2 (ON, OFF, OFF, ON) state, continuous Tsh/2 (ON, ON, OFF, ON) state, and continuous T0/4 (OFF, ON, OFF, ON) state; and when [theta] is between [[pi], 2[pi]], making (the first upper arm switch, the first lower arm switch, the second upper arm switch, and the second lower arm switch) present in order: continuous T0/4 (OFF, ON, OFF, ON) state , continuous Tsh/2 (ON, ON, OFF, ON) state, continuous T1/2 (ON, OFF, OFF, ON) state, continuous T0/2 (ON, OFF, ON, OFF) state, continuous T1/2 (ON, OFF, OFF, ON) state, continuous Tsh/2 (ON, ON, OFF, ON) state, and continuous T0/4 (OFF, ON, OFF, ON) state.