Discussion on Distribution Network Operating Envelope for Providing Allowable Active and Reactive Power Injections

Introduction: The high-proportion distributed energy resource (DER) connection in the distribution network deteriorates the condition of voltage violation when DERs control their power output arbitrarily. The operating envelope of distribution networks can decouple the safe operation of distribution networks from the regulation of distributed energy resources and map the voltage constraints of distribution networks into DER output constraints. Methods: This provides an effective means to solve the problem of different ownership entities and regulation objectives between distribution networks and DER. Existing researches mainly focus on the active power operating envelopes while ignoring the reactive power. This paper studies the calculating method for the active-reactive power operating envelope of distribution networks. First, the rectangle model of active-reactive power operating envelopes is constructed to calculate the operating envelopes that provide more flexibility for DER control, while satisfying the voltage constraints robustly and meeting the actual demands in the operation of DER control. Second, the area that the active-reactive operating envelope covers is enlarged by finding a new vertex on the right side of the p-q plane to generate a pentagon operating envelope which is called the expanded operating envelope. Results: This leads to a higher active power output limit for DER control. Conclusion: Finally, the effectiveness and safety of the proposed calculating method for distribution network operating envelopes is verified in distribution networks with different sizes