Abstract—Compared with conventional table-based direct
power control (DPC), DPC using space vector modulation (DPCSVM)
exhibits several specific features, such as a constant switching
frequency and small ripples in both active power and reactive
power. However, conventional DPC-SVM exhibits highly distorted
grid currents when the grid voltages are unbalanced. In this study,
we propose a novel and simple DPC-SVM that is effective under
both ideal and unbalanced grid voltage conditions by using
an extension of original instantaneous power theory. After deducing
the power slopes of both active power and reactive power,
the suitable converter voltage reference to nullify the errors of
active power and reactive power is analytically derived, which is
subsequently synthesized by SVM. The proposed DPC-SVM does
not require the extraction of complex positive/negative sequence
from the grid voltage/current or power compensation. Compared
to prior DPC-SVM using original imaginary power, the proposed
method exhibits much better performance by obtaining highly sinusoidal
line currents and eliminating twice grid-frequency ripples
in both active power and the reactive power under unbalanced
conditions. Simulations and experimental results supported the
theoretical study and confirmed the effectiveness of the proposed
method.
Index Terms—Direct power control (DPC), pulse width modulation
(PWM) rectifier, reactive power control, space vector
modulation (SVM).