Electric Power Converter Duty Control for Voltage Fluctuation
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Solution Overview
Problem
In electric power converters used in hybrid and electric vehicles, the output voltage fluctuates due to dead time, especially when switching between power-running and regenerative operations, leading to inaccurate detection of battery currents and deteriorated output-voltage controllability.
Innovation Solution
An electric power converter with a control unit that calculates a main duty based on target and inter-terminal voltages, and a sub-duty to accurately manage the duty amount for the electric-power conversion unit, using first and second voltage detection units to detect inter-terminal voltages at both the DC power source and motor sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current-based dead-time correction is used, then output voltage controllability is improved, but measurement precision deteriorates due to sensing errors near zero current
Solution Approach 1:
The patent introduces voltage detection as an intermediary measurement method to indirectly determine the operating state and dead-time correction needs, avoiding direct reliance on inaccurate current sensing near zero. By detecting voltages at both input and output terminals, the system can calculate duty ratios and infer current flow direction without directly measuring problematic near-zero currents.
Solution Approach 2:
The patent replaces the mechanical/electrical current sensing approach with a voltage-based detection and calculation system. Instead of using current sensors to detect charging/discharging states, the system uses voltage detection units and computational logic to determine the same information, thereby eliminating sensing errors associated with near-zero current measurements.
2Stability of the object's composition
If dead-time correction is applied during operation switching, then output voltage stability is improved, but response speed deteriorates due to detection delays
Solution Approach 1:
The patent performs preliminary voltage detection and duty ratio calculation based on detected voltages before actual operation switching occurs. By pre-determining the appropriate dead-time correction and duty adjustment based on voltage states, the system prepares correction actions in advance, enabling faster response when switching between power-running and regenerative operations without compromising voltage stability.
3Reliability
If voltage detection and dual calculation method are used, then tracking capability is improved, but device complexity increases
Solution Approach 1:
The patent makes the voltage detection units serve multiple functions: they detect terminal voltages for duty ratio calculation, determine operating states (power-running vs. regenerative), and provide data for dead-time correction. This multi-functionality reduces the need for separate detection systems, thereby limiting the increase in device complexity while achieving improved tracking capability through the first and second calculation units.
Data Source
AI summary
An electric power converter including an electric-power conversion circuit that performs bidirectional conversion of a voltage between a DC power source and a motor and outputs the voltage, a first voltage detector that detects an inter-terminal voltage at the DC power source side of the electric-power conversion unit, a second voltage detector that detects an inter-terminal voltage at the motor side of the electric-power conversion unit, and a controller. The controller includes a first calculator that calculates a main duty, based on a target voltage and the inter-terminal voltage at the motor side, and a second calculator that calculates a sub-duty, based on the main duty, the inter-terminal voltage at the motor side, and the inter-terminal voltage, at the DC power source side, detected by the second voltage detection unit. The controller calculates a duty amount for operating the electric-power conversion unit, based on the main duty and the sub-duty.