Motor Drive Controller Deadtime Compensation
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Solution Overview
Problem
Electric motor drive controllers face issues with short-circuiting due to deadtime, leading to current distortion, torque pulsation, and voltage estimation errors, particularly in low voltage and low speed operations.
Innovation Solution
An electric motor drive controller with a control unit that includes a sign calculation module to determine current polarity and a compensation module to generate a voltage compensation signal, using a lookup table to neutralize the deadtime effect by adding a compensation voltage vector, thereby reducing voltage estimation errors and improving current waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deadtime is provided to prevent short-circuiting between upper and lower switching devices, then reliability of switching devices is improved, but manufacturing precision of voltage estimation deteriorates
Solution Approach 1:
The patent applies preliminary anti-action by calculating and applying a compensation voltage in advance to counteract the known deadtime effect. The control unit determines the polarity of reference current commands during deadtime, calculates the corresponding deadtime voltage using a lookup table, and adds this compensation voltage to the voltage command before inversion. This pre-compensation approach neutralizes the deadtime effect on voltage estimation while maintaining the necessary deadtime for preventing short-circuiting.
2Reliability
If deadtime is provided to prevent short-circuiting between upper and lower switching devices, then reliability of switching devices is improved, but productivity of current supply deteriorates
Solution Approach 1:
The control unit performs preliminary calculation of deadtime voltage compensation based on the polarity of reference current commands determined during the deadtime period. By using a lookup table to quickly retrieve the appropriate compensation voltage and applying it before the actual current supply, the system maintains high-quality current supply without being degraded by the necessary deadtime for reliable switching operation.
3Reliability
If deadtime is provided to prevent short-circuiting between upper and lower switching devices, then reliability of switching devices is improved, but object-affected harmful factors increase
Solution Approach 1:
The patent converts the harmful deadtime effect into a beneficial compensation mechanism. Instead of simply eliminating deadtime (which would cause short-circuiting), the system utilizes the known deadtime duration to calculate a compensation voltage that, when added to the voltage command, transforms the harmful voltage estimation error into an accurate effective voltage. This approach maintains reliable switching while eliminating current distortion and torque pulsation caused by uncompensated deadtime effects.
Data Source
AI summary
A system and method of controlling an electric motor using a motor drive controller are provided. The motor drive controller includes a rectifier configured to convert an AC input voltage to a DC voltage, a DC bus electrically coupled to the rectifier, an inverter electrically coupled to the DC bus and configured to generate an AC voltage to drive the electric motor, and a control unit. The control unit includes a sign calculation module configured to determine a polarity of each phase of a reference current command and a compensation module configured to generate a voltage compensation command signal using one of the determined polarities of the reference current command and a measured current, and one of a measurement of DC bus voltage and a constant DC bus voltage value, the voltage compensation signal compensating the drive controller to neutralize a deadtime effect.