DC-to-AC Inverter Power Distribution via Dynamic DC Link Control
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Solution Overview
Problem
Existing power distribution methods in multistring inverters face challenges in maximizing the utilization of available power without additional complexity, particularly during derated operations, where power variations among DC sources lead to inefficiencies and increased losses.
Innovation Solution
A method that dynamically adjusts the power distribution among multiple DC sources connected to a DC-to-AC converter via actuable DC-to-DC converters, ensuring that the total power fed into the DC link remains constant, with variations compensated by corresponding changes in individual sources, thereby maintaining a stable DC-link voltage and optimizing power utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power distribution among DC sources is adjusted during derated operation to maximize power utilization, then power losses are minimized, but system complexity increases due to additional control mechanisms
Solution Approach 1:
The system uses the existing DC-to-DC converters to actively compensate for power variations among DC sources during derated operation, making the components serve dual purposes: their original power conversion function plus the additional function of power distribution optimization. This eliminates the need for separate control mechanisms while minimizing power losses.
Solution Approach 2:
The control device dynamically adjusts operating parameters (power distribution ratios) of the DC-to-DC converters based on real-time power availability from each DC source. By changing these parameters during derated operation, the system optimizes power utilization and minimizes losses without adding physical complexity.
2Reliability
If DC-to-AC converter power is derated below maximum available power, then grid stability is improved, but power utilization efficiency deteriorates
Solution Approach 1:
The system dynamically distributes power from multiple DC sources through controllable DC-to-DC converters during derated operation. This dynamic power distribution allows the system to adapt to varying power availability and maintain optimal efficiency even when the DC-to-AC converter operates below its maximum capacity, thus improving power utilization during grid stability events.
3Productivity
If operating voltage of DC sources is shifted during derated operation, then power distribution is optimized, but voltage control complexity increases
Solution Approach 1:
The DC-to-DC converters perform multiple functions: power conversion, power distribution optimization, and voltage control. By making these existing components multi-functional, the system achieves optimized power distribution during derated operation without adding separate voltage control mechanisms, thus avoiding increased control complexity.
4Productivity
If maximum power is fed into AC grid continuously, then power utilization is maximized, but grid stability deteriorates during peak demand
Solution Approach 1:
The system proactively distributes and manages power from multiple DC sources through the DC-to-DC converters before derated operation is required. This preliminary power management ensures that when grid stability becomes an issue, the system can quickly transition to optimized power distribution, maintaining both high power utilization and grid stability during peak demand periods.
Data Source
AI summary
In order to distribute power over multiple direct current sources which are connected in parallel to an input-side direct voltage intermediate circuit of a DC/AC transformer, at least one of which direct current sources is connected to the direct voltage intermediate circuit via a DC/DC transformer, wherein the DC/DC transformer can be actuated to change the power fed into the direct voltage intermediate circuit by the direct current source, the power levels of the direct current sources are decreased differently in a decreased operating mode of the DC/AC transformer in which the power of the DC/AC transformer is decreased compared to the sum of the maximum power levels available from all the direct current sources, and by actuating at least the one DC/DC transformer via which the at least one direct current source is connected to the direct voltage intermediate circuit, variation in the power levels of at least one other direct current source is compensated dynamically.