Abstract
This paper presents a proof-of-concept for a novel dq droop control technique that applies DC droop control methods to fixed frequency inverter-based AC microgrids using the dq0 transformation. Microgrids are usually composed of distributed generation units (DGUs) that are electronically coupled to each other through power converters. An inherent property of inverter-based microgrids is that, unlike microgrids with spinning machines, the frequency of the parallel-connected DGUs is a global variable independent from the output power since the inverters can control the output waveform frequency with a high level of precision. Therefore, conventional droop control methods that distort the system frequency are not suitable for microgrids operating at a fixed frequency. It is shown that the proposed distributed droop control allows accurate sharing of the active and reactive power without altering the microgrid frequency. The simulation and hardware-in-the-loop (HIL) results are presented to demonstrate the efficacy of the proposed droop control. Indeed, following a load change, the dq droop controller was able to share both active and reactive power between the DGUs, whereas maintaining the microgrid frequency deviation at 0% and the bus voltage deviations below 6% of their respective nominal values.
Highlights
Centralized power plants no longer have a monopoly on energy generation, which is becoming more and more distributed, especially with the evolution of distributed renewable energy resources and storage systems
The d and q axis components of the voltage are drooped proportionally to the d and q axis currents, respectively. This method relies on a synchronous reference frame phase-locked loop (PLL) to cancel the cross-coupling terms by keeping the d axis of the dq rotating frame aligned with the output voltage of the inverter, which can be very challenging during the transient phase
This paper presents a novel technique for active and reactive power-sharing in fixed frequency inverter-based AC microgrids with multiple distributed generation units (DGUs)
Summary
Centralized power plants no longer have a monopoly on energy generation, which is becoming more and more distributed, especially with the evolution of distributed renewable energy resources and storage systems. Angle droop control has been proposed in [14,15] to achieve power-sharing without changing the frequency of the microgrid This method has several drawbacks since it relies on accurate voltage angle measurement with respect to a reference angle. This method relies on a synchronous reference frame phase-locked loop (PLL) to cancel the cross-coupling terms by keeping the d axis of the dq rotating frame aligned with the output voltage of the inverter, which can be very challenging during the transient phase This method can only ensure equal load sharing and cannot be used for DGUs with different power ratings. The power-sharing is achieved using simple DC droop characteristics and reference frame transformation to share, independently, the d and q axis components of the load current among the DGUs. As the active and reactive power are shared separately, the line’s R/X ratio does not affect the proposed dq droop control method.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
