Voltage Source Inverter Calibration for Deadtime and Voltage Drop
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Solution Overview
Problem
Existing voltage-source inverter systems face inaccuracies in output voltage due to semiconductor voltage drops and deadtime effects, which affect power output calculations and sensor-less motor control, necessitating accurate voltage determination without the need for sensors.
Innovation Solution
A method and system that induce a DC current at a load device to determine the load voltage value, calculate the ideal switching-averaged voltage based on a switching modulation scheme, and adjust the modulation scheme to account for semiconductor voltage drops and deadtime effects, allowing for accurate voltage calibration and control without sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensor-less motor control is used to reduce cost and complexity, then device complexity and cost are reduced, but voltage measurement precision deteriorates
Solution Approach 1:
The controller performs self-calibration by inducing a known DC current through the inverter and measuring the resulting load voltage, then using this information to determine semiconductor voltage drops and deadtime effects. This self-service approach eliminates the need for external voltage sensors while maintaining measurement precision through automated characterization of the inverter's non-ideal behaviors.
Solution Approach 2:
The system implements a feedback loop where the controller measures the load voltage during DC current induction, compares it with the ideal switching-averaged voltage, and uses this feedback to calculate compensation values for semiconductor voltage drops and deadtime effects. This feedback mechanism enables accurate voltage determination without external sensors.
2Measurement precision
If direct voltage measurement is used to improve feedback accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the voltage sensing function from external hardware and relocates it to the existing current sensor and controller processing capabilities. By measuring current during DC induction and calculating voltage from known resistance, the system removes the need for separate voltage sensors and associated feedback loop complexity while maintaining measurement accuracy.
3Adaptability or versatility
If switching modulation is used to achieve continuous voltage values, then voltage control flexibility is improved, but voltage accuracy deteriorates due to semiconductor losses
Solution Approach 1:
The system changes the control parameter from ideal switching-averaged voltage to compensated voltage that accounts for semiconductor voltage drops and deadtime effects. By inducing DC current and measuring actual load voltage, the controller determines these parasitic parameters and adjusts the modulation scheme accordingly, maintaining voltage accuracy while preserving the flexibility of switching modulation.
Solution Approach 2:
The controller performs preliminary calibration by inducing DC current and characterizing the semiconductor voltage drops and deadtime effects before normal operation. This preliminary action establishes compensation values that are then applied during subsequent voltage control, ensuring accuracy is maintained throughout operation while retaining modulation flexibility.
Data Source
AI summary
A method for operating a voltage source inverter is provided, the method including inducing, via the voltage source inverter, a DC current at a load device to obtain a load voltage value; determining an ideal switching-averaged voltage based on a switching modulation scheme; determining a combined semiconductor voltage drop and deadtime effect; and adjusting the switching modulation scheme such that a resulting ideal switching-averaged voltage is based on the combined semiconductor voltage drop and deadtime effect and the load voltage value.