HVDC Power Converter Control for Voltage Support and Frequency Stability
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Solution Overview
Problem
Existing power converters in HVDC networks struggle to maintain stable AC voltage support and real power transfer, especially during disturbances, leading to potential frequency disruptions and ineffective frequency control measures.
Innovation Solution
A power converter with a controller that prioritizes reactive power transfer during AC voltage deviations and adjusts reactive current limits based on AC frequency stability, allowing for continued active power transfer by limiting reactive current during normal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power converter prioritizes reactive power transfer during AC voltage deviations, then AC voltage support is improved, but real power transfer capability deteriorates
Solution Approach 1:
The power converter dynamically adjusts its operating mode based on AC voltage conditions. During voltage deviations, it prioritizes reactive power transfer for voltage support. During normal conditions, it transitions to prioritize real power transfer, optimizing performance for different operating scenarios
Solution Approach 2:
The controller changes the priority parameter between reactive and active power transfer based on operating conditions. By monitoring AC voltage levels and frequency stability, the system switches between prioritizing reactive power (during voltage deviations) and active power (during normal conditions), resolving the contradiction between voltage support and real power transfer
Data Source
Figure 1
Figure 2~4
Figure 3(a)~3(d)
AI summary
In the field of high voltage direct current (HVDC) power transmission networks there is a need for an improved power converter. A power converter (10), for use in a HVDC power transmission network, comprises first and second DC terminals (12, 14), for connection in use to a DC network and between which extends at least one converter limb (16). The or each converter limb (16) includes first and second limb portions (18, 20) which are separated by an AC terminal (22), for connection in use to an AC network. Each limb portion (18, 20) includes a switching valve (24), and the power converter (10) including a controller (30) programmed to control switching of the switching valves (24) to control the flow of a converter current (Imax) through the power converter (10) and thereby in-use transfer power between the power converter (10) and the AC network. The power transferred between the power converter (10) and the AC network has an active component and a reactive component. The controller (30) is further programmed in use to: (i) prioritise to a first extent the transfer of reactive power (34) between the power converter (10) and the AC network during a first operating condition, when the AC voltage (V) of the AC network lies outside a desired operating range, by allowing up to a first amount of the converter current (Imax) to be a reactive current; and (ii) prioritise to a second extent, less than the first extent, the transfer of reactive power (34) between the power converter (10) and the AC network during a second operating condition, when the AC voltage (V) of the AC network lies within the desired operating range, by limiting the amount of converter current (Imax) that can be a reactive current to a second amount, less than the first amount, the second amount being determined according to a measured operating frequency of the AC network.