HVDC Converter Station Internal Communication via Voltage Modulation
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Solution Overview
Problem
HVDC power transmission systems with multi-terminal connections face complexities in communication between converter stations, relying on external data communication systems which are not optimal and costly, especially in large DC grids with high line capacitance.
Innovation Solution
A method within the converter stations to synchronize and allocate communication time slots, changing the set-point DC voltage level to convey information internally, eliminating the need for external communication systems, using synchronization signals like GPS for accuracy and modulating the voltage level to exchange digital control information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external separate data communication systems and telecommunication networks are used for communication between converter stations, then communication reliability is improved, but system cost and complexity increase
Solution Approach 1:
The patent combines the power transmission function and communication function into a single integrated system. The HVDC transmission line itself is used to carry both power and communication signals, eliminating the need for separate external communication infrastructure. This merging reduces system complexity and cost while maintaining communication reliability between converter stations.
Solution Approach 2:
The HVDC transmission line is made multi-functional by enabling it to serve both as a power transmission medium and as a communication channel. By modulating communication signals onto the power transmission line, the system achieves universal usage of the existing infrastructure, avoiding additional dedicated communication systems.
2Loss of information
If small ac voltage is injected into the system for control signaling, then communication between converter stations is enabled, but costly equipment is required on the high voltage side
Solution Approach 1:
The system uses the existing HVDC transmission line infrastructure to provide communication services without requiring additional expensive equipment on the high voltage side. The communication functionality is achieved by utilizing the inherent electrical characteristics of the transmission line itself, making the system self-sufficient and eliminating the need for specialized communication hardware.
Solution Approach 2:
The patent replaces the mechanical/electrical approach of injecting small AC voltage signals with expensive modulation equipment by using a communication method that leverages the existing power transmission infrastructure. The solution substitutes complex high-voltage modulation equipment with a simpler system that uses the transmission line's natural electrical properties for signal transmission.
3Loss of information
If small ac voltage is injected for control signaling, then communication is achieved, but high injection power levels are required in large DC grids with high line capacitance
Solution Approach 1:
The patent changes the operating parameters of the communication system by using DC voltage modulation instead of AC voltage injection. This parameter change allows communication signals to be transmitted using the existing DC power transmission infrastructure without requiring high injection power levels, making the system energy-efficient even in large DC grids with high line capacitance.
4Reliability
If backup schemes utilizing estimations and non-updated control data are used when external communication fails, then system operation is maintained, but operational optimality is reduced
Solution Approach 1:
The patent prepares for communication failures by having a backup communication path ready in advance. The integrated communication system using the HVDC transmission line serves as a redundant communication channel that can take over immediately if external communication systems fail, ensuring both operational continuity and optimality without relying on estimations or outdated data.
Data Source
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AI summary
The present invention relates to a method (60) in a converter station (2a, 2b, 2c, 2d, 2e, 2f) for communication within a DC power transmission system (1) comprising two or more interconnected converter stations (2a, 2b, 2c, 2d, 2e, 2f). The method (60) comprises the steps of: receiving (61), in the converter station (2a, 2b, 2c, 2d, 2e, 2f), a synchronization signal for synchronizing the two or more converter stations (2a, 2b, 2c, 2d, 2e, 2f); obtaining (62), in the converter station (2a, 2b, 2c, 2d, 2e, 2f), an allocation of a communication time slot (TS00, TS10, TS20, TS30, TS40, TS50); changing (63), in the converter station (2a, 2b, 2c, 2d, 2e, 2f), a set-point DC voltage level during the communication time slot (TS00, TS10, TS20, TS30, TS40, TS50); and measuring (64), in the converter station (2a, 2b, 2c, 2d, 2e, 2f), a change of DC current in timeslots other than the communication time slot (TS00, TS10, TS20, TS30, TS40, TS50). A communication method utilizing the DC power transmission system itself is thus provided.