On-Board Charger AFE Switching for Full Power on Any AC Grid
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Solution Overview
Problem
Current on-board charger (OBC) configurations are limited in delivering maximum power in single, split, and two-phase electrical grids, as they typically allow only a third of the total power that can be extracted in three-phase grids, compromising power density and component optimization.
Innovation Solution
The proposed OBC architecture employs a three-phase active front-end power factor corrector with three switches and a diodes arm, allowing for power extraction equal to that of a three-phase grid in any phase configuration by strategically controlling the switches and diodes to manage current flow, ensuring unity power factor and low Total Harmonic Distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a three-phase AFE is used with single-phase boost PFC stages, then the power factor is corrected and DC voltage is regulated, but only one-third of the maximum three-phase power can be extracted in single-phase mode
Solution Approach 1:
The patent applies dynamics by making the circuit topology reconfigurable through switching elements. The PFC stage can dynamically switch between single-phase and three-phase operational modes, allowing the system to adapt its power extraction capability based on the available input configuration. This dynamic reconfiguration enables the system to extract full power in both single-phase and three-phase modes rather than being limited to one-third power in single-phase mode.
Solution Approach 2:
The patent implements universality by designing a PFC stage that can universally handle both single-phase and three-phase input configurations using the same core circuitry. The active front-end converter is configured to accept either single-phase or three-phase AC input and regulate the DC output voltage appropriately, making the system multi-functional and adaptable to different grid configurations without requiring separate dedicated circuits for each mode.
2Power
If single-phase boost PFC converters are paralleled to achieve three-phase operation, then power extraction capability is improved, but the number of components increases and power density decreases
Solution Approach 1:
The patent applies merging by combining multiple PFC circuit functions into a single integrated active front-end converter. Instead of using separate paralleled single-phase boost PFC converters, the invention merges the functionality into one three-phase AFE circuit that handles all three phases simultaneously, reducing the total number of components while maintaining the power extraction capability.
Solution Approach 2:
The patent transitions from a single-phase dimensional approach to a three-phase dimensional approach. By utilizing all three phases of the AC input simultaneously in the active front-end converter, the system achieves higher power extraction capability without needing to parallel multiple single-phase circuits, thus reducing component count and increasing power density.
3Productivity
If a three-phase AFE is used, then power density is increased and components are optimized, but the maximum current extraction in single-phase mode is limited to one-third of three-phase capacity
Solution Approach 1:
The patent uses dynamics by enabling the three-phase AFE to dynamically adapt its operational characteristics based on the input configuration. When operating in single-phase mode, the AFE dynamically adjusts its current distribution and switching patterns to maximize the utilization of available single-phase input, allowing extraction of full power rather than being statically limited to one-third capacity.
Solution Approach 2:
The patent applies parameter changes by modifying the operational parameters of the AFE based on the input configuration. The system detects whether single-phase or three-phase input is available and changes its operating parameters accordingly, including current limits, switching frequencies, and power distribution ratios, to optimize power extraction for each mode while maintaining high power density.
Data Source
AI summary
An on-board charger (OBC) may include a power factor corrector PFC comprising a three phase active front end (AFE) connected to an AC electrical grid, and a DC/DC converter receiving a regulated DC voltage from the PFC and configured to charge a high voltage battery. The OBC may be configured to extract a power value which is equal to a reference maximum power extracted from a three phase electrical grid PMAX3∅, from any type of AC electrical grid to which the OBC is connected, and may include three switches SW1, SW2 and SW3 and a diodes arm having diodes D1 and D2 connected in series between a high and low side of the AFE, whereby two switches SW1 and SW2 are arranged between the AFE and the AC electrical grid and are able to interrupt current flowing between phase arms of the three phase AFE, wherein the third switch SW3 is arranged on a line connecting the diodes arm and the AC electrical grid.