A Review of Current-Limiting Control of Grid-Forming Inverters Under
Symmetrical Disturbances
Abstract
Grid-forming (GFM) inverters are recognized as a viable solution to
increase the penetration of renewable energy in bulk power systems.
However, they are physically different from synchronous generators in
terms of overcurrent capability. To protect the power semiconductor
devices and support the power grid under severe symmetrical
disturbances, the GFM control systems should be able to achieve the
following requirements: current magnitude limitation, fault current
contribution, and fault recovery capability. Various current-limiting
control methods are reported in the literature to fulfill these goals,
including current limiters, virtual impedance, and voltage limiters.
This paper presents an overview of those methods. Emerging challenges
that need to be addressed, including temporary overcurrent, unspecified
output current vector angle, undesired current saturation, and transient
overvoltage, are pointed out. Comparative simulations are conducted to
demonstrate the performance of different methods under grid voltage
drops and phase jumps. Finally, open issues of current-limiting control
methods for GFM inverters, including transient stability assessment,
voltage source behavior under overcurrent conditions, and windup of
voltage controllers, are shared.