Talking about the principle of driving DC motor with Z source inverter
The Z-Source Inverter (ZSI) is a DC-AC converter that performs buck and boost functions in a single stage. A unique advantage of ZSI is its through state, in which the two switches of the same bridge can be turned on at the same instant. No dead time is required, output distortion is greatly reduced, and higher output can be provided without using an LC filter. ZSI overcomes the conceptual and theoretical limitations of traditional systems and can boost the DC input voltage without the use of DC/DC boost converters or step-up transformers. In this paper, a ZSI driver with smart random pulse width modulation (RPWM) technology is proposed for the sensorless BLDC motor, which aims to improve the performance of the BLDC motor drive system.
ZSI overcomes the conceptual and theoretical barriers and limitations of traditional systems and can also boost the DC input voltage without the help of a DC-DC boost converter or step-up transformer.
Permanent magnet brushless DC (BLDC) motors are used in a variety of applications due to their higher efficiency, greater power-to-weight ratio, and lower maintenance costs. The trapezoidal electromotive force (EMF) BLDC motor requires rotor position information to order the drive drive. This positional information is typically generated by three Hall effect sensors placed on the non-drive end of the motor. However, these temperature-sensitive sensors not only increase the cost of the motor, but also require special mechanical settings to mount.
This paper aims to explore how to improve the performance of BLDC motor drive systems. To this end, a ZSI drive scheme is proposed, which uses a clever random pulse width modulation (RPWM) technique to drive a sensorless BLDC motor. The proposed system uses back electromotive force (BEMF) sensing for position estimation, and the ZSI drive can provide a wider range of boost voltages. For the ZSI-BLDC motor drive, this paper proposes a detourive double random simple boost pulse width modulation (DTRSBPWM) technique, which can achieve randomness in two ways with four initial carriers.
Two of the carriers are normal and inverted fixed-frequency triangular waves, and the third and fourth carriers are frequency-converted triangular waves obtained by the chaotic frequency generator and its inverter. The DTRSBPWM harmonic power distribution method outperforms the simple boost PWM (SBPWM) method. Simulation studies of the drive system were performed on MATLAB software and have been validated using the SPARTAN-6 Field Programmable Gate Array (FPGA) (XC6SLX45) device. This article will focus on total harmonic distortion (THD) of the output line voltage, DC bus utilization, and harmonic expansion factor (HSF).
How ZSI works
The Z-source inverter is a DC-AC converter that can perform buck and boost functions as a single stage. ZSI overcomes the conceptual and theoretical barriers and limitations of traditional systems and can also boost the DC input voltage without the help of a DC-DC boost converter or step-up transformer. The working principle of ZSI can be divided into four modes. The first mode is the traditional active state mode, where the inverter bridge acts as a current source for the DC link. The second mode is the through state mode, in which the inverter bridge operates in one of two conventional zero vectors, passing through the upper and lower devices of the inverter. The third mode is the non-through mode, where the inductor current assists in reducing the harmonics of the line current. The fourth mode is the traditional zero state, ie the inverter bridge operates in one of the zero states.
Simple boost PWM
The most common switching method used by ZSI is the simple boost PWM. This is an easy way, just two straight lines to control the through state. When the triangular waveform is higher than the upper envelope VP or lower than the lower envelope VN, the circuit operates in a through state. In other cases, it works like a traditional carrier PWM. During a simple boost PWM, the voltage stress generated by the entire device is high.
Sensorless control of ZSI-fed BLDC motor
ZSI's sensorless control is shown in Figure 1. The BLDC motor is sensorlessly controlled by estimating the zero-crossing moment of the back EMF (from the terminal voltage) and the correct commutation instant and feeding it to the ZSI circuit. The speed control of the motor is sensed by a proportional integral controller (PIC) and compared to the reference speed of the control action.
