DC Microgrid Power Sharing via Virtual Impedance Droop Control
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Solution Overview
Problem
In direct current (DC) networks, ensuring fair power sharing between multiple energy sources is challenging due to differences in impedance, leading to uneven power distribution, stability issues, and increased wear on energy storage devices, with existing methods often requiring costly and complex communication infrastructure.
Innovation Solution
The technique involves superimposing a small alternating current (AC) voltage on top of the DC voltage, using virtual impedance frequency droop control to regulate the AC signal and determine a desired DC voltage output, allowing for equal power contribution from all sources without the need for external communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple energy sources are connected at different distances to loads in a DC network, then power can be supplied to meet demand, but uneven power distribution occurs due to impedance differences
Solution Approach 1:
The patent changes the operating parameters by superimposing an AC signal on the DC voltage, enabling frequency droop control to regulate power sharing. This transforms the DC-only system into a hybrid AC-DC system where the AC component allows for controllable power distribution based on frequency modulation, resolving the uneven power sharing issue caused by impedance differences.
Solution Approach 2:
The patent introduces an AC signal as an intermediary mechanism to mediate power sharing between DC energy sources. This AC component acts as a mediator that carries frequency information, allowing sources to communicate their power contribution status without requiring direct DC-DC communication, thus achieving fair power sharing despite different impedances.
2Productivity
If power sharing is not properly managed in DC networks, then power can be distributed, but stability of the microgrid deteriorates
Solution Approach 1:
The patent implements feedback control through frequency droop mechanisms where the AC signal frequency responds to power imbalances. When power sharing becomes uneven, the frequency deviation provides feedback that triggers corrective action, regulating the DC voltage to restore proper power distribution and maintain microgrid stability.
Solution Approach 2:
The patent introduces dynamic control by superimposing an AC signal on the DC voltage, transforming the static DC system into a dynamic system. The AC component allows for real-time adjustments in power sharing based on system conditions, enabling the microgrid to adapt and maintain stability under varying load and generation conditions.
3Quantity of substance
If multiple energy storage devices operate without coordinated power sharing, then energy can be stored and supplied, but uneven discharge and charge patterns increase aging and replacement rates
Solution Approach 1:
The patent changes the operational parameters of energy storage devices by implementing AC-based frequency droop control on top of DC voltage. This allows for regulated power sharing where each storage device's charge/discharge rate is modulated based on system conditions, preventing excessive stress on individual devices and extending their operational lifespan.
4Ease of operation
If external communication infrastructure is used for power sharing control, then power distribution can be managed, but system complexity and cost increase
Solution Approach 1:
The patent enables self-service power sharing control where each DC energy source autonomously regulates its power contribution using local measurements of the AC signal frequency. Sources independently adjust their output based on frequency droop characteristics without requiring external communication infrastructure, achieving coordinated power sharing through self-contained control mechanisms.
Solution Approach 2:
The AC signal serves as an intermediary that eliminates the need for external communication infrastructure. Instead of requiring separate communication channels between control systems, the AC component embedded in the DC voltage carries the necessary control information, allowing sources to coordinate power sharing through the power lines themselves.
Data Source
AI summary
Techniques for power sharing in DC networks using virtual impedance frequency droop control are provided. In one aspect, a method for power sharing in a DC network having multiple electrical energy generation sources connected to at least one load includes the steps of, at each of the electrical energy generation sources: generating a controllable DC voltage; superimposing a controllable AC signal on top of the DC voltage; regulating the AC signal using virtual impedance frequency droop control; and determining a desired DC voltage output using the regulated AC signal. The DC voltage can then be regulated to match the desired DC voltage output. A system for power sharing in a DC network is also provided.