Configurable DC Strand Polygon Circuit for Phase Load Compensation
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Solution Overview
Problem
Existing energy supply systems using multiple DC voltage sources face challenges in achieving efficient load compensation between phases, leading to potential damage to battery cells and inefficiencies in energy usage.
Innovation Solution
A procedure and circuit arrangement that generate a multi-phase change current by configuring configurable DC strands in a polygon circuit, allowing for improved load compensation between DC sources without influencing external supply networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive charge balancing is used to balance battery cells, then charge balance between cells is improved, but valuable electrical energy is lost and the method does not offer a solution for the discharge process
Solution Approach 1:
The system uses the load itself to perform charge balancing. During discharge, the control unit distributes the discharge current among battery cells in a balanced manner, allowing cells to discharge at different rates based on their state of charge. This eliminates the need for separate balancing circuits and prevents energy loss, as the balancing function is integrated into the normal discharge operation.
2Reliability
If active charge balancing is used to balance battery cells, then charge balance between cells is improved, but the circuit complexity increases with power electronic components and control systems
Solution Approach 1:
The invention extracts the charge balancing function from separate dedicated circuits and integrates it into the existing inverter control system. By using the inverter's control unit to manage current distribution during discharge, the system eliminates the need for complex active balancing circuits with power electronic components, reducing overall system complexity while maintaining effective charge balance.
Solution Approach 2:
The inverter control unit is given a dual function: it performs both the primary function of converting DC to AC for power delivery and the secondary function of charge balancing during discharge. This multi-functionality eliminates the need for separate balancing hardware, significantly reducing circuit complexity while maintaining effective charge management across all battery cells.
3Manufacturing precision
If inverter switching frequency is increased to reduce voltage harmonics, then voltage quality is improved, but switching losses increase proportionally
Solution Approach 1:
The system optimizes the inverter switching frequency by selecting an appropriate frequency range that balances voltage quality and switching losses. Rather than continuously increasing frequency to eliminate harmonics, the control unit uses pulse-width modulation (PWM) techniques and selective harmonic elimination methods to maintain acceptable voltage quality at moderate switching frequencies, thereby minimizing switching losses while still delivering high-quality AC power.
Data Source
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AI summary
The invention relates to a method for generating a multiphase alternating current, in particular a three-phase alternating current, by connecting a plurality of DC voltage sources (3), comprising at least the following method steps: - providing a configurable DC voltage string (5) for each phase (L1, L2, L3) of the multiphase alternating current, wherein each configurable DC voltage string (5) is formed from a plurality of the DC voltage sources (3) which can be connected together in a configurable series connection; - arranging the configurable DC voltage strings (5) in a polygon connection, in particular in a delta connection; - providing a neutral point generator (10) for realizing a common neutral point (N) of all configurable DC voltage strings (5);and - configuring the configurable DC voltage strings (5) so that the multiphase alternating current is provided and also a zero-system current is formed for charge equalization between the configurable DC voltage strings (5).