Multi-Terminal Power System Constant-Power Control
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Solution Overview
Problem
Existing systems face challenges in efficiently connecting multiple renewable energy sources in series with the power grid due to the need for precise voltage or current matching, which is difficult to achieve, especially over long distances, leading to stability issues and increased costs.
Innovation Solution
Implementing a method where each sending terminal behaves as a constant-power source, allowing both output voltage and current to vary with external conditions while maintaining a constant product, enabling series or parallel connections and facilitating the integration of renewable energy sources into the grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple voltage sources are connected in series to provide higher supply voltage, then the supply voltage is improved, but the voltage matching precision requirement increases
Solution Approach 1:
The patent changes the operating parameter of the power sources from fixed voltage mode to variable voltage mode. Each power source adjusts its output voltage dynamically based on the total power requirement and series configuration, eliminating the need for precise pre-matching of voltage parameters while maintaining stable power delivery.
Solution Approach 2:
The patent introduces dynamic control where each power source in the series connection can independently adjust its output voltage in real-time. This dynamic adjustment capability allows the system to adapt to changing load conditions and eliminates the static voltage matching requirements that previously constrained series connections.
2Power
If multiple current sources are connected in parallel to provide higher supply current, then the supply current is improved, but the current matching precision requirement increases
Solution Approach 1:
The patent transforms the control parameter from fixed current to variable current for each power source. By controlling each source to deliver a proportional share of the total power rather than requiring equal current, the system eliminates precise current matching requirements while achieving high current output through parallel connections.
3Reliability
If renewable energy sources are integrated through power electronics interface controlled as current source, then the stability with voltage source grid is improved, but the device complexity increases
Solution Approach 1:
The patent changes the control mode of the power electronics interface from current-source control to variable voltage control with power-based coordination. This parameter change simplifies the control architecture by eliminating the need for complex impedance matching and stability compensation while maintaining grid compatibility through autonomous power delivery.
4Device complexity
If multiple sending terminals are connected in series to reduce cost and increase efficiency, then the device complexity is reduced, but the voltage and current matching difficulty increases
Solution Approach 1:
The patent implements a power-based control strategy where each sending terminal adjusts its output voltage and current dynamically to deliver a predetermined power level. This parameter transformation from voltage/current control to power control automatically resolves the matching problem in series connections, as each terminal independently contributes its power share without requiring coordination of electrical parameters.
Data Source
AI summary
A method for forming and operating a multi-terminal power system, includes: connecting multiple sending terminals to a network of a power system; and local control of each sending terminal to behave as a constant-power source such that both output voltage and output current of the sending terminal may simultaneously vary in response to changing external circuit conditions while maintaining constant a product of the output voltage and the output current of the sending terminal. At least one sending terminal may include a capacitive output converter having a capacitor connected between two output terminals and a controlled current source connected in parallel to the capacitor, or an inductive output converter having an inductor connected to an output terminal and a controlled voltage source connected in series with the inductor.