Power Converter Control Segmentation for Grid Fault Stability
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Solution Overview
Problem
Existing power converters used to interface generators with variable voltage and frequency to a fixed voltage and frequency power grid lose control during network faults or transients, leading to instability in dc link voltage and reactive current control.
Innovation Solution
A power converter system with a first and second active rectifier/inverter, a dc link, and filters, controlled by dedicated controllers to maintain desired dc link voltage and power transfer, with the ability to adjust power and voltage during network deviations, ensuring voltage support and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single controller regulates dc link voltage during network faults, then control simplicity is maintained, but control reliability and stability are lost
Solution Approach 1:
The control system is segmented into two independent controllers: a first controller that regulates dc link voltage by controlling the first active rectifier/inverter, and a second controller that regulates power transfer and provides voltage support at the network terminals. This segmentation allows each controller to independently maintain its control function during network faults, preventing the loss of control that occurs in single-controller systems when voltage dips are detected.
2Object-affected harmful factors
If the power converter disconnects during network voltage loss, then protection is provided, but continuous grid support capability is lost
Solution Approach 1:
The filter acts as an intermediary between the power converter and the supply network, providing galvanic isolation that allows the converter to remain connected during voltage dips. The first active rectifier/inverter and second active rectifier/inverter can independently control power flow through the filter to the network, enabling continuous voltage support and reactive current injection even when network voltage is lost, while still providing protection through controlled operation.
3Device complexity
If reactive current control is lost during voltage dips, then control simplicity is maintained, but voltage support capability is lost
Solution Approach 1:
The second controller dynamically adjusts its control strategy based on network conditions. During normal operation, it regulates power transfer to the supply network. During voltage dips, it automatically switches to providing voltage support by controlling the voltage at the network terminals and injecting reactive current as needed. This dynamic adaptability allows the system to maintain voltage support capability without requiring complex pre-programmed fault response mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system maintains control and stability of the dc link voltage and reactive current during network faults or transients, enabling continued operation and support of the grid, thus ensuring reliable energy transfer and compliance with network codes.
Implementation Method 1
a first active rectifier/inverter electrically connected to the stator of the generator and including a plurality of semiconductor power switching devices; a second active rectifier/inverter including a plurality of semiconductor power switching devices
Data Source
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AI summary
The present invention provides_a power converter that can be used to interface a generator (4) that provides variable voltage at variable frequency to a supply network operating at nominally fixed voltage and nominally fixed frequency and including features that allow the power converter to remain connected to the supply network and retain control during supply network fault and transient conditions. The power converter includes a generator bridge (10) electrically connected to the stator of the generator (4) and a network bridge (14). A dc link (12) is connected between the generator bridge (10) and the network bridge (14). A filter (16) having network terminals is connected between the network bridge (14) and the supply network. A first controller (18) is provided for controlling the operation of the semiconductor power switching devices of the generator bridge (14). Similarly, a second controller (46) is provided for controlling the operation of the semiconductor power switching devices of the network bridge (14). The first controller (18) uses a dc link voltage demand signal (VDC_GEN*) indicative of a desired dc link voltage to control the semiconductor power switching devices of the network bridge (10) to achieve the desired level of dc link voltage that corresponds to the dc link voltage demand signal (VDC_GEN*). The second controller (46) uses a power demand signal (P*) indicative of the level of power to be transferred from the dc link to the supply network through the network bridge (14), and a voltage demand signal (VTURB*) indicative of the voltage to be achieved at the network terminals of the filter (16) to control the semiconductor power switching devices of the network bridge (14) to achieve the desired levels of power and voltage that correspond to the power and voltage demand signals (P* and VTURB*).