Virtual Resistance Gate Driver PWM Delay
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Solution Overview
Problem
Existing damping methods for inverter systems either result in inefficiencies due to resistive losses or overburden the controller with software-based virtual resistors, failing to effectively reduce harmonic distortion at resonant frequencies.
Innovation Solution
A gate driver is configured to delay pulse width modulation (PWM) signals based on the magnitude and polarity of the current flowing through the electric machine's switches, effectively generating a virtual damping resistor by modulating the PWM signal widths, thereby reducing harmonic distortion without hardware losses or performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive damping methods are used, then harmonic distortion is reduced, but resistive losses increase and efficiency decreases
Solution Approach 1:
The patent replaces physical passive damping components (resistors) with a software-based virtual resistor implemented in the controller. The virtual resistor uses computational algorithms to simulate resistive damping effects, achieving harmonic distortion reduction without actual resistive energy dissipation. This substitution of mechanical/physical damping with a software-based control approach resolves the contradiction by eliminating resistive losses while maintaining damping functionality.
2Loss of energy
If software-based virtual resistors are implemented, then hardware losses are reduced, but controller workload increases and performance decreases
Solution Approach 1:
The patent segments the virtual resistor computation into discrete, manageable components that can be processed efficiently by the controller. The damping calculation is broken down into specific algorithmic steps that operate on individual PWM cycles, allowing the controller to handle the computational load in a structured manner rather than as a monolithic complex task. This segmentation enables the controller to manage the software-based virtual resistor with reduced perceived workload.
Solution Approach 2:
The patent implements the virtual resistor using periodic computation synchronized with the PWM switching cycles. The controller calculates damping values at regular intervals corresponding to the inverter operating cycle, rather than requiring continuous complex computation. This periodic approach allows the controller to perform necessary calculations efficiently, reducing overall workload while maintaining effective damping control throughout operation.
3Object-affected harmful factors
If PWM signals are delayed by current-dependent amounts, then virtual damping is achieved, but signal timing complexity increases
Solution Approach 1:
The patent implements dynamic PWM signal delay where the delay amount varies based on real-time current magnitude and polarity conditions. Rather than using a fixed delay, the system adjusts the delay parameter dynamically according to operating conditions, allowing the virtual resistor to adapt to changing load scenarios. This dynamic approach achieves effective damping across varying operating points while using a relatively simple delay mechanism that can be implemented through basic conditional logic in the controller.
Data Source
AI summary
A vehicle includes an electric machine operated by an inverter. The electric machine includes a gate driver configured to energize a switch of the inverter with a pulse width modulation (PWM) signal. The gate driver is configured to delay the PWM signal by a dependent amount that is a function of a magnitude of current of a lead of the electric machine. The delay is responsive to a polarity of the current being positive.