DC Bus Voltage Control Using Virtual Conductance
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Solution Overview
Problem
In three-phase alternating current (AC) voltage systems, DC bus voltage oscillations are amplified when DC bus capacitance is reduced, leading to power quality issues, reduced capacitor lifetime, and limited operating range in hybrid electric vehicles.
Innovation Solution
A method and system for controlling a three-phase AC voltage source by determining an error between a DC bus voltage command and detected voltage, obtaining virtual conductance or resistance, and regulating the output DC bus voltage using a proportional integral (PI) function, with saturation limits and feed-forward power considerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If DC bus capacitance is reduced, then system size and cost are decreased, but DC bus voltage oscillations are amplified leading to power quality issues
Solution Approach 1:
The patent changes the control parameters of the voltage source converter by implementing a modified current control strategy that includes an additional current component. This parameter change allows the system to maintain stable DC bus voltage with reduced capacitance, effectively resolving the contradiction between minimizing capacitance and suppressing voltage oscillations.
Solution Approach 2:
The patent employs feedback control by continuously monitoring the DC bus voltage and adjusting the converter current accordingly. The control system uses the voltage error signal to modulate the converter output, creating a feedback mechanism that suppresses voltage oscillations even with reduced capacitance.
2Quantity of substance
If DC bus capacitance is reduced, then system size is decreased, but capacitor lifetime is reduced
Solution Approach 1:
By changing the control parameters to include active power factor correction and modified current control, the system reduces the stress on the capacitor. This allows using smaller capacitance values without exceeding capacitor ratings, thereby extending capacitor lifetime while maintaining reduced system size.
3Quantity of substance
If DC bus capacitance is reduced, then system size is decreased, but operating range is limited
Solution Approach 1:
The patent implements parameter changes in the control strategy, including active power factor correction and unity power factor operation modes. These parameter adjustments enable the system to accommodate a wider range of operating conditions and loads with reduced capacitance, thereby expanding the operating range despite smaller energy storage capacity.
Data Source
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AI summary
In an example embodiment, a method of controlling a three-phase alternating current (AC) voltage source includes determining an error between a direct current (DC) bus voltage command and a detected DC bus voltage, the detected DC bus voltage being a part of an outer feedback loop, obtaining one of a virtual conductance or virtual resistance, the one of the virtual conductance or the virtual resistance being a part of an inner feedback loop relative to the outer feedback loop, regulate an output DC bus voltage based on the error and the one of the virtual conductance or the virtual resistance and controlling the three-phase AC voltage source based on the regulation of the output DC bus voltage.