A 3-Phase Z-Source Inverter Driven By A Novel Hybrid Switching Algorithm

Abstract

A 3-phase Z-source inverter has been researched, designed, simulated, built

and tested. The purpose of the inverter is to deliver 3-phase 400 VAC from a

DC supply that can vary over a range of 20 to 70 Vdc. This is done with a Zsource

inverter topology which is a single conversion method with no additional

DC to DC boost converter. A novel DSP control algorithm allows the inverter to

achieve the following:

· Run Space Vector Pulse Width Modulation (SV-PWM) for maximum DC

bus voltage utilization while boosting the DC bus during zero space vector

states using shoot through.

· Seamless transition between modulation control and modulation / shoot

through control.

· Optimised efficiency and DC bus utilisation using Hybrid Space Vector

Boost Pulse Width Modulation (HSVB PWM) which is unique to this

dissertation.

Such a system is particularly suited to fuel cell and particularly wind turbine

applications where the DC bus voltage is varies over a wide range resulting in

the need for a DC to DC buck/boost to regulate the DC bus to maintain a steady

3-phase sinusoidal output. A further application could be for general purpose 3-

phase inverter capable of operating on different DC standard bus voltages ( e.g.

24, 36, 48 VDC).

The benefits of a Z-source topology for the above purposes are a reduction in

high power semi-conductor components (e.g. power MOSFET). There is also a

reduction in switching losses and inherent shoot through protection.

Furthermore, the inverter is more robust in the sense that it is not vulnerable to

spurious shoot through, which could be disastrous in the case of a traditional

voltage fed inverter.