Series Voltage Source Converter Precharging via Circulating Current Impedance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Voltage source converters connected in series with the load face challenges in regulating capacitor voltages, especially when the load is not carrying current, leading to difficulties in precharging and maintaining permissible voltage ranges, which affects the reliability and efficiency of reactive power compensation.
Innovation Solution
Incorporating a multi-phase impedance circuit that provides circulating currents for charging and discharging capacitors, even in a no-load state, allowing for precharging and voltage regulation of voltage source converters, thereby enabling their operation regardless of the load's current-carrying condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage source converter is connected in series with load for reactive power compensation, then reactive power compensation is achieved, but capacitor voltage regulation becomes impossible when load current is zero
Solution Approach 1:
A circulating current impedance is introduced as an intermediary element between the voltage source converter and the load. This impedance enables current circulation through the converter's capacitor even when the load current is zero, allowing the converter to regulate its capacitor voltage and operate reliably in no-load conditions while maintaining its series connection configuration for reactive power compensation
2Ease of manufacture
If voltage source converter operates in series configuration, then reactive power compensation is provided, but precharging of capacitors cannot be performed when load is open circuit
Solution Approach 1:
The circulating current impedance serves as a mediator that enables precharging current to flow through the converter's capacitor during startup or when the load is open-circuited. This allows the converter to be charged before operation without requiring additional precharging equipment, maintaining circuit simplicity while improving operational ease
3Reliability
If conventional parallel compensation systems are used, then reactive power compensation is achieved, but network stability and component stress optimization are reduced
Solution Approach 1:
The voltage source converter in series configuration with circulating current impedance is designed to perform multiple functions: reactive power compensation during load operation, capacitor voltage regulation during no-load conditions, and precharging capability. This multi-functionality eliminates the need for separate parallel compensation systems, optimizing network stability while reducing overall system complexity
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 solution ensures the voltage source converters can be regulated and precharged in no-load conditions, optimizing network stability and reducing stress on components, particularly for large, rapidly changing non-linear loads, and potentially eliminating the need for conventional parallel compensation systems.
Implementation Method 1
The voltage source converter (24a-c) has a capacitor array, in particular a DC capacitor, and the electrical circuit (23) is configured to regulate the charge and/or voltage of the capacitor array under no-load conditions
Implementation Method 2
The electrical circuit (23) includes an impedance (26) configured to provide a circulating current for charging and discharging the capacitor array
Implementation Method 3
the electrical circuit (23) includes an impedance (26) configured to provide a circulating current for charging and discharging the capacitor array
Data Source
Figure 1
Figure 2
AI summary
The invention relates to an electrical circuit comprising a load (2) and at least one voltage source converter (24a-c) for reactive power compensation, which is connected to the load (2) in series. The voltage source converter (24a-c) is designed to be functional in a zero-load state of the load (2), in which the load (2) does not conduct any current. The invention additionally relates to a device (1) and also to a method for reactive power compensation.