Power Converter Control During Network Faults
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Solution Overview
Problem
Existing power converters fail to maintain control of reactive current and dc link voltage during network faults or transients, leading to loss of voltage support and power regulation when network voltage dips.
Innovation Solution
A power converter system with dual active rectifier/inverters and a dc link, featuring controllers that manage semiconductor switching devices using pulse width modulation and feedback signals to maintain desired dc link voltage and power transfer, even during network voltage deviations, allowing for voltage support and power regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single active rectifier/inverter controller is used to regulate dc link voltage, then the control structure is simple, but the ability to maintain control during network voltage dips is lost
Solution Approach 1:
The control system is segmented into two independent controllers: a first controller for the active rectifier that maintains dc link voltage, and a second controller for the active inverter that manages power transfer to the network. This segmentation allows each controller to independently maintain its control function even when the other is affected by network faults, thereby resolving the contradiction between simple control structure and reliability during faults.
2Device complexity
If the power converter relies solely on network voltage for control, then the control system is simple, but control is lost during network voltage dips
Solution Approach 1:
The control system incorporates feedback mechanisms where the first controller uses feedback from the dc link voltage sensor to maintain dc link voltage, and the second controller uses feedback from power measurements to manage power transfer. This feedback approach allows the system to maintain control during network voltage dips by relying on local measurements rather than network voltage, resolving the contradiction between simple control system and adaptability during voltage dips.
3Device complexity
If reactive current control is tied to network voltage, then the control implementation is straightforward, but voltage support capability is lost during network faults
Solution Approach 1:
The control system dynamically switches between different control modes based on network conditions. The second controller can operate in power control mode during normal conditions or switch to voltage support mode during network faults, adjusting its behavior dynamically to maintain voltage support capability. This dynamic control approach resolves the contradiction between straightforward control implementation and reliability during faults.
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 ensures continuous control and voltage support during network faults, maintaining efficient power transfer and reactive current management, thus addressing the limitations of previous technologies.
Implementation Method 1
The active semiconductor power switching devices are then controlled by the generator controller using a pulse width modulation circuit to produce stator electrical quantities that correspond to the desired quadrature axis current.
Implementation Method 2
a first active rectifier/inverter electrically connected to the stator of the generator and including a plurality of semiconductor power switching devices
Data Source
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 (VDC13 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 (VDC13 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*).