Modular Multilevel Converter Series Compensation Device
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Solution Overview
Problem
Existing series compensation devices for electrical energy transmission networks are inflexible and often cause undesired oscillations due to their fixed capacitance, limiting their ability to adapt to various impedance conditions and voltage profiles.
Innovation Solution
A series compensation device utilizing a modular multilevel power converter connected to a transformer, allowing for flexible impedance adjustment and voltage profile generation, which avoids sub-synchronous resonances by using a transformer to impress a periodically changing voltage into the power transmission network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed capacitance series capacitor is used for series compensation, then the impedance of the transmission line can be reduced, but undesired oscillations (sub-synchronous resonances) occur in the power transmission network
Solution Approach 1:
The patent applies dynamics by replacing the fixed capacitance series capacitor with a modular multilevel power converter that can dynamically adjust its impedance characteristics. The converter uses multiple controllable switching elements to vary the compensation amount in real-time, transforming the static compensation system into a dynamic one that can adapt to changing network conditions and avoid resonant frequencies.
Solution Approach 2:
The patent implements parameter changes by enabling continuous adjustment of the compensation impedance through the modular multilevel power converter. The converter can change its effective capacitance or inductance values by controlling the switching states of its modules, allowing the system to operate at optimal parameters under different load conditions and avoid fixed parameter resonances.
2Adaptability or versatility
If series compensation devices are customized for each application, then the compensation can be tailored to specific impedance conditions, but the device complexity and adaptation requirements increase
Solution Approach 1:
The patent applies segmentation by dividing the power converter into multiple identical modular units (submodules). Each module contains switching elements and energy storage components that can be independently controlled. This modular structure allows the system to achieve high adaptability by simply adding or removing modules rather than redesigning the entire device for different applications.
Solution Approach 2:
The patent implements universality through the modular multilevel power converter design that can function in various compensation scenarios. The same modular architecture can be configured for different impedance compensation needs, voltage levels, and power ratings by adjusting the number and arrangement of modules, making a single device design applicable to multiple applications.
3Adaptability or versatility
If a modular multilevel power converter is used for series compensation, then flexible impedance adjustment and voltage profile generation are achieved, but the device complexity increases
Solution Approach 1:
The patent uses segmentation to manage complexity by organizing the power converter into standardized modular units. Each submodule contains a fixed set of switching elements and energy storage components, creating a repetitive building block structure. This segmentation allows complex impedance control functions to be achieved through simple combinations of identical modules, reducing design and control complexity.
Solution Approach 2:
The patent applies partial action by using a large number of simple modular units to achieve the desired compensation effect, rather than using a single complex high-power converter. Each module operates at a lower power level with simpler switching requirements, and the cumulative effect of multiple modules provides the necessary impedance control flexibility.
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
Enables flexible and efficient series compensation of electrical energy transmission networks, effectively managing impedance and damping oscillations, while allowing for the transmission of both reactive and active power, thus improving network stability and adaptability.
Implementation Method 1
a primary winding of the transformer can be connected (or switched) in series in a phase line of the power transmission network, and with a modular multilevel converter that has a large number of modules that have an electrical module - Form a series circuit, with the modular multilevel power converter (AC side) being connected to a secondary winding of the transformer
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a series compensation device (1) for an electrical energy transmission network (3) having a transformer (7), wherein a primary winding (4) of the transformer (7) can be connected in series in a phase line (L1) of the energy transmission network (3). The series compensation device has a modular multilevel power converter (13), which has a plurality of modules (1_1 … 1_n), which form an electrical module series circuit (22). The modular multilevel power converter (13) is connected to a secondary winding (10) of the transformer (7).