Modular Multilevel Voltage Source Converter DC Deicer
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Solution Overview
Problem
Existing DC deicers based on thyristors consume excessive reactive power, generate harmonic components, and are limited to lower voltage levels, failing to meet the needs for deicing power transmission lines above 220 kV and unable to boost current and voltage from zero at the DC side, thereby posing risks to power grids and AC systems.
Innovation Solution
A voltage source converter based DC deicer utilizing a modular multilevel converter with full H-bridge submodules, including connecting reactors, smoothing reactors, and deicing disconnectors, which allows for adjustable voltage and current at the DC side, enabling deicing of power transmission lines of various voltages, including ultra-high voltages, without grounding points at the DC side, and employing fully-controlled power electronic devices and thyristor pairs for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thyristors are used in DC deicers, then deicing function is achieved, but reactive power consumption increases and harmonic components are generated
Solution Approach 1:
The patent replaces the thyristor-based mechanical switching system with a voltage source converter using IGBTs (insulated gate bipolar transistors), which are fully controllable power electronic devices. This substitution eliminates the need for reactive power consumption and harmonic generation inherent in thyristor systems, while maintaining the deicing function through controlled DC current output.
Solution Approach 2:
The patent changes the operating parameters of the power electronic system by using a voltage source converter with controllable DC voltage and current output. This allows precise control of the deicing current while avoiding the fixed operating characteristics of thyristor systems, thereby eliminating reactive power consumption and harmonic distortion.
2Ease of operation
If 6-pulse rectifier is adopted, then deicing operation is enabled, but serious harmonic component is generated requiring load transfer to another bus
Solution Approach 1:
The patent replaces the 6-pulse rectifier system with a voltage source converter using IGBTs, which provides fully controllable rectification. This substitution eliminates the serious harmonic components generated by 6-pulse rectifiers while maintaining ease of operation through controlled DC current output for deicing.
3Adaptability or versatility
If existing DC deicers are used, then deicing of 220 kV or lower voltage lines is achieved, but deicing of ultra-high voltage lines and current/voltage boosting from zero is not possible
Solution Approach 1:
The patent employs a voltage source converter with dynamic control capability that can adjust DC voltage and current output according to different deicing requirements. This dynamic control enables the system to handle various voltage levels from 10 kV to ultra-high voltages and to boost current and voltage from zero, overcoming the fixed limitations of existing DC deicers.
Solution Approach 2:
The voltage source converter is designed as a universal platform that can serve multiple voltage levels and application scenarios. By controlling the number of series-connected IGBT modules, the system can adapt to different voltage requirements, providing both deicing functionality and voltage/current boosting capability across a wide range of operating conditions.
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 solution effectively addresses the limitations of existing DC deicers by enabling safe and efficient deicing of all types of power transmission lines, ensuring AC system quality, and supporting deicing of lines from 10 kV to ultra-high voltages with minimal impact on the AC system, making it suitable for both new and existing deicing projects.
Implementation Method 1
a modular multilevel voltage source converter based on a full H-bridge submodule and having an alternating current (AC) side and a DC side
Implementation Method 2
a connecting reactor; first and second smoothing reactors
Implementation Method 3
employing fully-controlled power electronic devices and thyristor pairs for efficient operation
Data Source
AI summary
A voltage source converter based DC deicer and its control method are provided. The voltage source converter based DC deicer includes a connecting reactor, a modular multilevel voltage source converter based on a full H-bridge submodule, smoothing reactors, deicing disconnectors, a deicing bus, and a deicing AC line. The AC side of the modular multilevel voltage source converter is connected to an AC side bus through the connecting reactor, an isolation disconnector and a breaker. The DC side of the modular multilevel voltage source converter is connected to the deicing AC line through the smoothing reactors, the deicing disconnectors, and the deicing bus.