| Inverter, as an important part of new energy generation system such as wind energy, solar energy, fuel cell etc, plays a key role in the course of energy conversion and transmission. The traditional inverter includes voltage source inverter (VSI) and current source inverter (CSI). However, both of the inverters have barriers and limitations.They are either a buck (VSI) or a boost (CSI) inverter, In order to require a higher voltage or lower voltage relative to input voltage, an additional DC-DC converter to boost the output voltage (VSI) or to buck the output voltage (CSI) is needed, which lowers the efficiency of system. What is more, in a traditional inverter, the upper and lower devices of each phase leg could be gated ON (or OFF) simultaneously by EMI noise, which would decrease the circuit reliability. To avoid the state, dead time has to be provided in the control strategy. Nevertheless, a disadvantage of the dead time is that it can bring the output voltage and current waveform distortion.In order to solve the above limitations of traditional inverter, a new type inverter named Z-source inverter was presented, which can overcome the drawbacks of the traditional inverter; it employs a unique impedance network (Z-network), which allows the Z-source inverter to have some new features which are disabled on traditional inverter.In this paper, the operating principle and superiority of the Z-source inverter are described firstly, And its mathematical model and PWM control strategy are analyzed in detail. Then the devices voltage and current stress is analyzed, which offers a theoretical authority to the control of Z-source inverter based on DSP.At the same time, the design method of Z-source inverter is given out. Finally two sets of Z-source inverter systems are built under grid-connected active power inversion and UPS passive power inversion, the simulation and experimental results have been performed to confirm the analysis. They are quite consistent with the theoretical analysis. |
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