Space Vector Modulation of Dual-Inverter System Focusing on Improvement of Multilevel Voltage Waveforms

Abstract

A space vector modulation (SVM) technique of a dual-inverter system for an open-end winding motor drive is described in this paper, where one inverter has a battery power source and the other has an only capacitor across the dc bus. The SVM must be achieved to operate the motor with field-oriented control and simultaneously to control the capacitor voltage at a constant value by using redundant switching states of the dual-inverter system. The control of the capacitor voltage is carried out by selecting a charging or a discharging mode in each redundant switching state, taking the instantaneous motor power factor into account. In addition, it is also required to reduce the error voltage pulses, which are generated in output multilevel voltage waveforms during the dead time. The compensation method of the existing dead-time scheme and the improved SVM sequence to reduce the error voltage vectors are proposed in this paper. The proposed methods are examined through several experimental tests and are confirmed to generate superior output voltage waveforms from the viewpoint of the measured total harmonic distortion and dv/dt.

Experimental Verification of Fault Tolerant Operation Focusing on DC-Bus Battery Failure in Dual Inverter Motor Drive

“…In this paper, the SVM technique for the fault tolerant operation at the high-modulation-index is newly proposed, which controls the voltage command within the limited voltage region by employing a field-weakening control technique. However, it has the problem that unexpected error voltage pulses are generated in the multilevel voltage waveforms during a dead time [21,22]. In this paper, it is confirmed through experimental tests that the proposed fault tolerant operations at the high-modulation-index can continue to drive the motor even though one of the inverter DC-bus batteries fails.…”

“…A conventional SVM sequence, which is based on a general triangular-wave pulse width modulation (PWM), has seven switching states in one control period, that is, it cannot avoid the switching transition between V60 and V60in. On the other hand, it is possible to avoid the transition by designing the SVM sequence to have five states as described in Reference [22]. The block diagram and the algorithm of the SVM sequence which has five states are the same as the conventional sequence, for example, the capacitor charging or discharging mode of each switching state.…”

Reduction of Input Current Harmonics Using Dual Inverter for Motor Drive

“…The topology and modulation strategies of a dual inverter system consisting of two VSIs and an open-end winding machine have been researched for several purposes such as multi-level operations (17)- (19) , wide speed range operations (20) (21) , and fault-tolerant functions (22) (23) . In multi-level operations, the DC-link voltage are controlled to be 2:1 for the purpose of high-efficiency driving of the motor, and a 5-level waveform is generated in the winding phase voltage (17) (19) .…”

A Ten Level Inverter Scheme with Extended Linear Modulation Range Till Full Base Speed

“…This configuration aids in increasing the phase voltage levels with a reduced number of switches besides the benefit of reliability and fault-tolerant capability [4], [5], [8]. These two inverters together can generate a combined hexagonal multilevel space vector structure (SVS) of radius V dc similar to a 2-level inverter single hexagonal structure feeding the IM from one end using a DC-link voltage of V dc [4]- [6]. For any hexagonal SVS, the maximum peak phase fundamental voltage that can be attained from a DC link of V dc is 0.637V dc (correspond to the full base speed operation of the IM drive), when the inverter operates in six-step mode.…”