Modular Power Converter Decoupling AC DC Flows
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Solution Overview
Problem
Existing power transmission systems face challenges in efficiently decoupling power flows between AC and DC networks, leading to undesirable power oscillations and modulation effects, especially in weak, low-inertia systems like wind farms, which can result in energy losses and mechanical stress.
Innovation Solution
A modular power converter with switching elements and energy storage devices, controlled by a unit that selectively transfers and stores energy to decouple power flows, inhibiting modulation effects between AC and DC networks, thereby preventing undesirable power flow changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power is transmitted over long distances via AC networks, then power transmission capability is improved, but capacitive load effects increase causing power oscillations and energy losses
Solution Approach 1:
The patent introduces a DC network as an intermediary medium between AC power sources and loads. By converting AC to DC for transmission and back to AC at the destination, the system eliminates the capacitive load effects that cause power oscillations in long-distance AC transmission, while maintaining power transmission capability.
Solution Approach 2:
The patent utilizes phase transitions between AC and DC power forms. Power is converted from AC to DC at the sending end for transmission, and then converted back to AC at the receiving end. This phase transition approach allows the system to avoid the harmful capacitive effects of long-distance AC transmission while maintaining the benefits of AC power distribution.
2Productivity
If power flows are coupled between AC and DC networks, then power transfer efficiency is improved, but modulation effects cause undesirable power flow changes in connected networks
Solution Approach 1:
The patent extracts the harmful modulation effects from the power flow by introducing independent control of reactive power at AC-DC interface points. This allows the system to maintain efficient power transfer while preventing modulation effects from propagating to other parts of the connected networks.
Solution Approach 2:
The patent changes the control parameters at the AC-DC interfaces by independently controlling reactive power flow. This parameter change allows the system to decouple the power flows, enabling efficient power transfer between AC and DC networks while preventing undesirable power flow changes in connected networks through proper reactive power management.
3Adaptability or versatility
If conventional power converters are used to connect AC and DC networks, then power conversion function is provided, but device complexity increases and control difficulty increases
Solution Approach 1:
The patent segments the power conversion system into modular AC-DC interface units distributed at different locations in the network. Each unit performs localized power conversion and reactive power control, simplifying the overall system architecture and reducing control complexity compared to a single large conventional converter.
Solution Approach 2:
The patent enables the AC-DC interface units to autonomously manage reactive power flow and maintain voltage stability without requiring complex centralized control. Each interface unit independently adjusts its reactive power output based on local conditions, reducing control system complexity while maintaining the necessary power conversion functionality.
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 modular power converter effectively decouples power flows, minimizing energy losses and mechanical stress, while enabling efficient power transfer and modulation, thus enhancing the reliability and efficiency of power transmission systems.
Implementation Method 1
the or each switching element and the or each energy storage device in the or each module combining to selectively provide a voltage source
Implementation Method 2
at least one energy storage device, the or each switching element and the or each energy storage device in the or each module combining to selectively provide a voltage source
Data Source
AI summary
A modular power converter includes first and second terminals to connect to electrical networks and at least one module connected between the first and second terminals, the module(s) including at least one switching element and at least one energy storage device, the switching element(s) and the energy storage device(s) combining to selectively provide a voltage source, the switching element(s) being switchable to transfer power between the first and second terminals. The converter further includes a control unit configured to selectively control switching of the switching element(s) to store energy from or release energy to either or both of the first and second terminals so as to decouple respective power flows at the first and second terminals and thereby inhibit a modulation of power flow at one of the first and second terminals from modifying a power flow at the other of the first and second terminals.