Cell Capacitor Voltage Determination in Multi-Cell Power Converters
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Solution Overview
Problem
Existing methods for determining the cell capacitor voltage in multi-cell power converters are inefficient and require additional hardware, leading to increased costs and complexity in measurement and maintenance.
Innovation Solution
Integrating voltage measurement units into the gate units of each power electronic valve, allowing continuous voltage measurements to be taken and transmitted to a control unit, which determines the cell capacitor voltage value using redundant measurements from both phase legs, thereby reducing the need for additional communication lines and enhancing modularity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate voltage measurement unit is connected in parallel to the cell capacitor, then the cell capacitor voltage can be measured directly, but the device complexity and cost increase due to additional hardware and communication lines
Solution Approach 1:
The voltage measurement unit is integrated into the existing gate units that control the power electronic valves. The gate units already have communication connections to the control unit, so the voltage measurement functionality is merged with the existing control structure, eliminating the need for separate measurement hardware and communication lines.
Solution Approach 2:
The gate units, which originally only controlled the power electronic valves, are enhanced to perform dual functions: controlling the valves and measuring the voltage across them. This multi-functionality reduces the overall system complexity by eliminating dedicated measurement units.
2Reliability
If continuous voltage measurements are taken from multiple power electronic valves, then redundant measurements improve reliability, but the amount of data to be processed increases
Solution Approach 1:
The control unit receives continuous voltage measurements from multiple gate units and uses this feedback information to determine the cell capacitor voltage. The redundant measurements provide feedback that enhances reliability, and the control unit processes this data to extract the necessary voltage information.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An arrangement to determine a cell capacitor voltage value (Udc) of a cell (10") of a multi-cell power converter comprises the cell (10") and a control unit (28). The cell (10") itself comprises four power electronic valves (1-4) interconnected as a full-bridge converter having a first and a second phase leg, where each phase leg comprises a series-connection of two (1, 3; 2, 4) of the four power electronic valves and where the connection point (6; 7) between the two power electronic valves of each phase leg is externally connectable, a cell capacitor (5) being connected in parallel to the first and the second phase legs, and four gate units (16-19), each being connected to a corresponding one of the power electronic valves (1-4) as well as to the control unit (28). Each of the four gate units (16-19) comprises a voltage measurement unit (24-27) adapted to take a continuous voltage measurement across the corresponding power electronic valve, and each of the four gate units (16-19) is adapted to transmit its continuous voltage measurement. The control unit (28) is adapted to receive from each of the four gate units (16-19) its continuous voltage measurement and to determine the cell capacitor voltage value (Udc) based on at least one of these voltage measurements.