This paper proposes a novel pulse-width-amplitude modulation (PWAM) method for three-phase quasi-Z source inverter system in motor drive application. It is demonstrated that it operates at only 1/3 switching frequency of traditional PWM methods, with less harmonic distortion. As a result, switching actions and losses are also reduced significantly. With the proposed modulation, the required capacitance is reduced greatly, which makes a system of smaller volume and lighter weight. Compared to traditional PWM methods, the higher efficiency and better reliability are confirmed in PWAM controlled motor drive system. The motor drive with the proposed hybrid PWAM modulation method presents good performance in simulation. Theoretical analysis is provided to verify the inverter efficiency and design improvements.
1. Quasi-Z-source inverter
2. Pulse-width-amplitude modulation
3. Motor drive
Fig. 1. Quasi-Z source inverter based motor drive .
Fig. 2. Topology in the second sector.
EXPECTED SIMULATION RESULTS:
Fig. 3. Outcomes of rotation speed r, current ia and torque Tm of motor (f=30 Hz).
Fig. 4. Simulation results of three-phase qZSI when using PWAM method. (a) qZS capacitor voltages vc1and vc2; (b) qZS inductor currents iL1 and iL2; (c) qZSI’s dc-link voltage vpn; (d) qZSI’s output line to line voltage vab(f=30 Hz).
Fig. 5. Simulation results of three-phase qZSI when using PWAM method. (a) qZS capacitor voltages vc1and vc2 ; (b) qZS inductor currents iL1 and iL2; (c) qZSI’s dc-link voltage vpn; (d) qZSI’s output line to line voltage vab(f=50 Hz).
Fig. 6. Outcomes of rotation speed r, current ia and torque Tm of motor (f=50 Hz).
In this paper, a novel modulation method for three-phase qZSI motor drive was introduced. The qZSI allows dc-link 6ɷ voltage ripples, as a result that the required qZS inductance and capacitance are reduced significantly. Besides, compared to traditional SPWM, only one third of the switches are doing switching actions, which reduced the number of switching time and loss significantly. By using the proposed PWAM modulation method, the motor drive operates well and efficiently.
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