EV Charger Current Sensor Compensation for DC Offset Ripple
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Solution Overview
Problem
AC to DC converters in electric systems face issues due to a DC offset in AC current sensors, leading to resistive losses, saturation, and asymmetries in magnetic components, which result in ripple on the DC output.
Innovation Solution
A control circuit with a time domain PI controller and a frequency domain PR controller is used to reduce or eliminate the ripple by operating at a known frequency of the imposed ripple, and the PI controller responds to time-variant stimuli like the DC level of the DC link.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a DC offset is present in AC current sensors, then the AC signal includes a DC value, but this causes resistive losses through resistive components and saturation in magnetic components
Solution Approach 1:
The patent segments the control into two independent domains: a time-domain controller (PI controller) that handles DC level variations, and a frequency-domain controller (PR controller) that handles AC ripple at specific frequencies. This segmentation allows each controller to optimize for its specific function without interference, eliminating the need for DC-blocking capacitors and preventing both resistive losses and measurement errors
Solution Approach 2:
The patent introduces an intermediary compensation signal generated by the dual-controller system that is injected into the control loop to actively cancel out the DC offset effects. This intermediary signal mediates between the sensor output and the control action, preventing DC content from reaching the power stage while preserving accurate AC current measurement
2Measurement precision
If a DC offset is present in AC current sensors, then the AC signal includes a DC value, but this results in saturation or other asymmetries in magnetic components
Solution Approach 1:
The patent segments the control into two independent domains: a time-domain controller (PI controller) that handles DC level variations, and a frequency-domain controller (PR controller) that handles AC ripple at specific frequencies. This segmentation allows each controller to optimize for its specific function without interference, eliminating the need for DC-blocking capacitors and preventing both resistive losses and measurement errors
Solution Approach 2:
The patent applies preliminary anti-action by using the PI controller to preemptively counteract DC level shifts before they can cause magnetic component saturation. The controller continuously adjusts the operating point to maintain symmetry in the magnetic components, preventing asymmetries before they occur
3Measurement precision
If a DC offset is present in AC current sensors, then the AC signal includes a DC value, but this imposes ripple on a DC output of the AC to DC converter
Solution Approach 1:
The patent segments the control into two independent domains: a time-domain controller (PI controller) that handles DC level variations, and a frequency-domain controller (PR controller) that handles AC ripple at specific frequencies. This segmentation allows each controller to optimize for its specific function without interference, eliminating the need for DC-blocking capacitors and preventing both resistive losses and measurement errors
Solution Approach 2:
The patent implements feedback by continuously monitoring the DC link voltage and using the dual-controller system to adjust the control signals accordingly. The PR controller specifically targets and eliminates ripple components at the fundamental frequency and its harmonics, while the PI controller maintains the overall DC level, creating a stable DC output
Data Source
AI summary
Current sensor compensation is provided. A system can include a charger for an electric vehicle having one or more controllers. A controller can amplify an input signal at a selected frequency to generate a first signal. A controller can amplify a direct current component of the input signal to generate a second signal. A component of the charger can generate a reference signal for input into a current sensor of the charger. The reference signal can be based on a combination of the first signal and the second signal.