Multi-Stage Converters for DC Grid Load Flow Control
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Solution Overview
Problem
In DC voltage networks with meshed outgoing lines, load flow imbalances occur due to differing line resistances, leading to overloading of some lines while others are underutilized, and existing solutions like transformers are costly and inefficient.
Innovation Solution
Implementing multi-level converters to generate longitudinal voltages along outgoing lines, allowing for the exchange of power between lines without dissipating energy into an AC network, and using a connecting line with a capacitor or inductor to manage current flow, thereby achieving a neutral power balance and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional transformers are used to control load flow in DC networks, then power transmission between lines is achieved, but construction and maintenance costs increase significantly
Solution Approach 1:
The patent replaces traditional mechanical transformers with electronic multi-stage converters to achieve power transmission and load flow control in DC networks. The converters use solid-state switching devices (IGBTs, MOSFETs) and capacitive energy storage to transfer power between DC lines without requiring electromagnetic transformation, thereby eliminating the high construction and maintenance costs associated with transformers while maintaining full power transmission capability
Solution Approach 2:
The invention changes the fundamental operating parameters by using DC voltage and electronic switching instead of AC frequency and electromagnetic induction. The multi-stage converters operate with DC links and use pulse-width modulation (PWM) techniques to control power flow, representing a parameter change from traditional AC transformer-based systems to DC converter-based systems, which reduces complexity and cost
2Productivity
If outgoing lines have different lengths and resistances, then load flow distribution occurs naturally, but some lines become overloaded while others remain underutilized
Solution Approach 1:
The patent implements feedback control through multi-stage converters that continuously monitor line conditions and adjust power flow in real-time. The converters receive feedback signals about line loading status and automatically modulate their output to balance the load distribution, preventing overloading of high-resistance lines and underutilization of low-resistance lines, thereby maintaining both efficiency and reliability
Solution Approach 2:
The invention introduces dynamic control capability through electronically controllable multi-stage converters, replacing the static passive line configuration. The converters can dynamically adjust their impedance and power output based on real-time network conditions, enabling flexible load redistribution that adapts to changing line characteristics and ensures optimal utilization of all outgoing lines
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
This method effectively balances load flow across outgoing lines, reduces costs by eliminating the need for transformers, and allows for scalable and efficient power transmission, ensuring that multi-level converters absorb and emit equal energy over time.
Implementation Method 1
a first multi-stage converter (18) generates a longitudinal voltage along the first output line (12), a second multi-stage converter (22) generates a longitudinal voltage along the second output line (14)
Implementation Method 2
a connecting line (24) is provided through which the two outgoing lines (12, 14) are connected to each other
Implementation Method 3
using a connecting line with a capacitor or inductor to manage current flow
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a method for controlling a load flow in a DC voltage network (2). According to the invention, in order that the load flow can be controlled cost-effectively, a first and a second output line (12, 14) of the DC voltage network (2) are connected to two bus lines (4, 6) of the DC voltage network (2) and form a loop (16), a longitudinal voltage is produced along the first output line (12) by means of a first multi-stage current converter (18), a longitudinal voltage is produced along the second output line (14) by means of a second multi-stage current converter (22), and in this way electrical power is transmitted between the two output lines (12, 14).