Electric-Power Conversion Apparatus Control Unit
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Solution Overview
Problem
Conventional electric-power conversion apparatuses experience control delays due to the need for voltage detection and A/D conversion, leading to prolonged charging times and discrepancies between input and output electric power, especially when the output current command value changes.
Innovation Solution
The apparatus includes a control unit that creates an input current amplitude command value based on the output current command value, allowing it to control the first and second electric-power conversion circuits to follow these command values without relying on detected DC voltage, thus eliminating calculation delays and stabilizing the voltage across the smoothing capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage detection and A/D conversion are performed to estimate DC input current, then input electric power can be calculated, but control delay occurs due to detection and conversion processing time
Solution Approach 1:
The invention creates a command value copy of the output current command value and uses this copied value directly for input current amplitude command calculation, bypassing the need for actual voltage detection and A/D conversion. This copying approach eliminates measurement delays while maintaining sufficient control accuracy.
Solution Approach 2:
The invention performs preliminary calculation of the input current amplitude command value based on the output current command value before actual voltage detection is completed. By anticipating the required input power based on commanded output, the system prepares control signals in advance, reducing overall control loop delay.
2Reliability
If output current command value is increased gradually to prevent load failure, then load safety is improved, but charging time is prolonged due to slow power transfer
Solution Approach 1:
The system performs preliminary preparation by calculating the input current amplitude command value in advance based on the output current command value and its changing rate. This allows the input power to be ready immediately when output power needs to increase, enabling faster charging while still gradually increasing output current to protect the load.
Solution Approach 2:
The invention replaces the mechanical detection-and-react control mechanism with a calculated command-value-based control system. Instead of detecting actual voltage and current to determine power flow, the system uses command values and their rates of change to preemptively adjust input power, significantly reducing response time.
3Ease of operation
If input current amplitude command value is adjusted to follow output current command value, then input/output power balance is improved, but control complexity increases due to additional calculation requirements
Solution Approach 1:
The invention changes the control parameter from actual detected voltage and current values to command value parameters. By using the output current command value and its changing rate as the basis for calculation, the system simplifies the control logic while maintaining power balance, as command values are already available without additional detection overhead.
Data Source
AI summary
A control unit of an electric-power conversion apparatus has an input current amplitude command value creation means that creates an input current amplitude command value, which is an amplitude command value of an input current of a first electric-power conversion circuit, in accordance with an output current command value, which is a command value of an output current of a second electric-power conversion circuit, when the output current command value changes; the control unit controls the first electric-power conversion circuit so that an input current follows an input current command value created based on an input current amplitude command value created by the input current amplitude command value creation means; the control unit controls the second electric-power conversion circuit so that an output current follows an output current command value.