Three-Level HV Rectifier Circuit for EV Battery Charging
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Solution Overview
Problem
High voltage traction batteries in electric vehicles stress rectifier devices, leading to limited choices, higher costs, and lower efficiency due to the need for high voltage rating components, especially when battery voltage exceeds 450 V.
Innovation Solution
A three-level rectifier circuit is proposed, where power semiconductor devices and capacitors are arranged to reduce voltage stress by half, allowing the use of lower voltage rated components, such as 600 V diodes instead of 1200 V diodes, by connecting devices and capacitors in series and parallel configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high voltage rating components are used to match traction battery voltage, then the system can operate at high voltage, but the cost increases and component choices are limited
Solution Approach 1:
The rectifier circuit is segmented into multiple voltage levels using series and parallel configurations of semiconductor devices and capacitors. The three-level topology divides the high battery voltage into lower voltage segments, allowing the use of lower voltage rated components (e.g., 600V diodes instead of 1200V diodes) while still matching the high voltage battery system.
Solution Approach 2:
The patent changes the voltage parameter distribution across circuit components by introducing a three-level voltage structure. By using capacitors to create intermediate voltage levels and configuring semiconductor devices in series-parallel arrangements, the voltage stress on individual components is reduced while maintaining the overall high voltage capability of the system.
2Power
If high voltage rating semiconductor devices are used, then the system can handle high battery voltage, but conversion efficiency decreases
Solution Approach 1:
The semiconductor devices are segmented into multiple lower voltage-rated units arranged in series-parallel configurations. This segmentation reduces the voltage stress on each device, allowing the use of lower voltage rated components that have lower on-state voltage drops and switching losses, thereby improving overall conversion efficiency while handling high battery voltages.
Solution Approach 2:
The patent changes the voltage parameter distribution across semiconductor devices by implementing a three-level topology. This parameter change allows operation at lower voltage stress points for each device, which improves their efficiency characteristics (lower conduction and switching losses) while maintaining the ability to interface with high voltage batteries.
3Device complexity
If conventional rectifier circuits are used with high voltage batteries, then the system is simple, but the voltage stress on semiconductor devices is high
Solution Approach 1:
The rectifier circuit is segmented into a three-level topology with multiple capacitors and semiconductor devices arranged in series-parallel configurations. This segmentation distributes the voltage stress across multiple components, reducing the voltage burden on each individual semiconductor device while maintaining a relatively simple overall circuit structure that builds upon conventional rectifier designs.
Solution Approach 2:
Capacitors are introduced as intermediary elements that create intermediate voltage levels between the high voltage battery and the semiconductor devices. These intermediary capacitors act as voltage buffers, reducing the direct voltage stress on semiconductor devices while maintaining circuit simplicity through a structured three-level architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces the voltage stress on semiconductor devices, enabling the use of lower voltage rated components with higher performance, thereby reducing on-board charger expenses and improving conversion efficiency.
Implementation Method 1
a transformer, electrically connected between the DC/AC converter and the AC/DC converter
Implementation Method 2
The diodes and capacitors are arranged such that when a voltage across the terminals is in a positive half cycle, a first subset of the diodes are conducting
Implementation Method 3
a first subset of the capacitors are in parallel, and a voltage across each of the capacitors is half the input voltage
Data Source
AI summary
A power system includes a DC/AC converter, a traction battery, an AC/DC converter electrically connected between the DC/AC converter and traction battery, and a transformer electrically connected between the DC/AC converter and AC/DC converter. The AC/DC converter includes a plurality of semiconductor devices and a plurality of capacitors such that during power transfer from the DC/AC converter to the traction battery, a voltage across each of the capacitors is half of a battery voltage.