Abstract
This article proposes a multifunctional cascade controller structure for voltage-source converters. The proposed structure contains a decoupling loop between the outer voltage control loop and the inner current control loop, and operation in either voltage or current control mode is possible. In voltage control mode, the current controller can be made completely transparent. In the case of faults, the proposed structure enables inherent overcurrent protection by a seamless transition from voltage to current control mode, wherein the current controller is fully operational. Seamless transitions between the control modes can also be triggered with an external signal to adapt the converter to different operating conditions. The proposed structure allows for integration of simple, accurate, and flexible overcurrent protection to state-of-the-art single-loop voltage controllers without affecting voltage control properties under normal operation. The properties of the proposed controller structure are validated experimentally on a 10-kVA converter system.
Highlights
T HE paradigm shift towards clean energy production has sparked a significant interest in microgrids and standalone converters powered by distributed renewable energy generation
This paper proposes a multifunctional cascade controller structure for voltage-source converters
These maps are purely defined by the voltage and current controllers, i.e., the proposed cascade controller structure does not have an effect on the stability of the control modes
Summary
T HE paradigm shift towards clean energy production has sparked a significant interest in microgrids and standalone converters powered by distributed renewable energy generation. In the recently proposed high-performance single-loop voltage controllers [11]–[14], the aspect of overcurrent protection is either neglected [11], requires additional fault detection mechanism and results in tripping of the converter [12], or relies on modification of the pulse-width modulator (PWM) reference [13], [14]. The properties, e.g., dynamic performance and robustness to load variations, of the two control modes can be set independently of each other This allows for integration of simple and accurate overcurrent protection to single-loop voltage controllers without having an effect on their original properties under normal operating conditions. The properties of the proposed cascade controller structure are experimentally validated on a 10-kVA converter
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