Chain-link Converter Voltage Reference Control
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Solution Overview
Problem
Existing electrical chain-link converter systems face challenges in efficiently converting non-equal power outputs from multiple DC power sources, such as wind turbines and solar panels, into balanced AC power for distribution networks, often requiring costly adjustments and lengthy wiring due to unequal power source locations.
Innovation Solution
A control unit with a processor and storage unit is used to calculate and transmit dedicated voltage references to each converter cell, ensuring active and reactive power balance across the phase leg, allowing for non-equal power sources to be compensated and reducing the need for external power adjustments and lengthy wiring by co-locating cells with their respective sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external power sources are connected to converter cells by long cables to compensate for non-equal power outputs, then power balance can be achieved, but system cost increases and wiring complexity increases
Solution Approach 1:
The system divides the power conversion function into multiple independent converter cells, each connected to its own local DC power source. This segmentation allows each cell to operate independently with its own voltage reference, eliminating the need for long interconnecting cables between power sources and converter cells, while still achieving overall power balance through coordinated control of individual cell voltage references
Solution Approach 2:
Each converter cell is assigned a dedicated local DC power source and a cell-specific voltage reference signal, creating local autonomy in power management. This local quality approach allows each cell to independently regulate its power output based on local conditions, compensating for non-equal power outputs without requiring complex centralized wiring or long cables to redistribute power
2Length of stationary object
If converter cells are distributed at different locations to match power sources, then wiring length is reduced, but power balance control becomes more difficult
Solution Approach 1:
The control system dynamically adjusts the voltage reference parameter for each converter cell based on the cell's active power output and the total active power of the phase leg. By changing the voltage reference parameter individually for each distributed cell, the system achieves precise power balance control without requiring long cables, as each cell's voltage reference is tailored to its local power source characteristics and position
3Reliability
If batteries are used to adjust for non-equal power of external power sources, then power equality can be achieved, but system cost and device complexity increase
Solution Approach 1:
Each converter cell serves itself by using its own local DC power source and independently regulating its output through a dedicated voltage reference signal. The cell autonomously adjusts its active and reactive power output based on its local power source capabilities and the overall system requirements, eliminating the need for external batteries or complex power redistribution systems to achieve power equality
Data Source
Figure 1~3
Figure 4
AI summary
The invention relates to an electrical chain-link converter system (101) comprising a converter phase leg (102) for converting a plurality of DC electrical currents from a plurality of DC power sources (103) to an AC current of an electrical power distribution network (104). The phase leg comprises a plurality of serially connected converter cells (105) each of which is connected to a respective power source (103) of the plurality of DC power sources. The system also comprises a control unit (106) associated with the phase leg, the control unit comprising a processor; and a storage unit storing instructions that, when executed by the processor, cause the control unit to, for each of the converter cells: obtain a dedicated voltage reference for the converter cell; and transmit the voltage reference to the converter cell.