AC Subgrid Droop Control Using Virtual Voltage Averaging
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Solution Overview
Problem
Existing AC subgrids face challenges in standardized power control and interoperability due to differing control methods compared to DC subgrids, complicating the management of power flow and frequency regulation.
Innovation Solution
A decentralized power control concept using virtual DC voltage calculations and droop curves to manage power flow and frequency in AC subgrids, allowing for standardized power control and improved interoperability between AC subgrids and main grids, with devices grouped based on power control capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If different control methods are used for AC and DC subgrids, then power control can be optimized for each specific grid type, but interoperability between different power grids becomes complicated
Solution Approach 1:
The patent transforms the AC subgrid control problem into a DC-like control framework by introducing virtual DC voltage as a control parameter. This parameter transformation allows AC subgrids to use standardized DC subgrid control methods while maintaining AC-specific operational characteristics, thereby achieving both optimization and interoperability
Solution Approach 2:
The patent introduces virtual DC voltage as an intermediary parameter that bridges AC and DC control domains. This virtual parameter enables AC subgrids to participate in standardized power control protocols designed for DC systems, resolving the interoperability issue while preserving AC grid-specific control optimization
2Adaptability or versatility
If decentralized power control is implemented in AC subgrids, then standardized power control and interoperability are improved, but frequency regulation complexity increases
Solution Approach 1:
The patent implements frequency regulation through feedback mechanisms where each device monitors local frequency deviations and adjusts its power output accordingly. This decentralized feedback approach standardizes control while managing complexity through localized decision-making rather than centralized coordination
Solution Approach 2:
The patent divides frequency regulation into segmented, device-level responsibilities rather than centralized control. Each device independently regulates frequency based on its local conditions and virtual voltage calculations, simplifying the overall system complexity while achieving standardized control across the AC subgrid
Data Source
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AI summary
A method and a device (6, 7) for managing power in an AC subgrid (2) is proposed. To do so, virtual voltages (V..Vn) from a plurality of other devices (5, 8) in the AC subgrid (2) are received (201 ) and used to calculate (202) a weighted average virtual voltage (Vavg). Based on that and a droop curve (Cdroop), a droop current (Idroop) is determined (204). Furthermore, the frequency (f) in the AC subgrid (2) is measured (205) and used to calculate (206) a set current (Iset) based on the droop current (Idroop) and the measured frequency (f). Then, the set current (Iset) is set (207) in a current control circuit (25) of the device (6, 7). Finally, an actual virtual voltage (Vnew) based on the droop curve (Cdroop) and the set current (Iset) is determined (208) and sent (209) to other devices (5, 8) in the AC subgrid (2). In addition, an AC-subgrid (2) is disclosed, comprising a plurality of such devices (6, 7), which are interconnected in terms of power and data communication.