Inverter-Charger Combining Traction and Charging via Segmented Switching
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Solution Overview
Problem
Existing electric vehicle systems face inefficiencies in combining traction inverters and chargers, as they operate independently and incur high semiconductor losses due to differing current requirements and switching frequencies, leading to compromised charging efficiency and increased costs.
Innovation Solution
A single device combining the functions of a traction inverter and charger using parallel switching elements, such as IGBTs or SiC transistors, which can be switched in and out of the circuit to manage high currents for propulsion and lower currents for charging, allowing for higher switching frequencies without sacrificing efficiency, and sharing processor and DC link structures to reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same semiconductors are used for both traction inverter and charger functions, then device complexity is reduced, but semiconductor losses increase due to high current requirements
Solution Approach 1:
The patent divides the semiconductor switching elements into two distinct groups: a first plurality for traction inverter operation and a second plurality for charger operation. This segmentation allows each group to be optimized for its specific function, with the first group handling high currents for motor propulsion and the second group handling lower currents for battery charging, thereby reducing overall semiconductor losses while maintaining a single integrated device structure.
2Power
If high current is used for traction motor propulsion, then motor power is sufficient, but semiconductor switching losses increase
Solution Approach 1:
The patent segments the semiconductor switching elements into a first plurality dedicated to traction inverter operation and a second plurality for charger operation. The first plurality is configured to handle high currents required for motor propulsion while the second plurality handles lower charging currents, allowing each segment to be optimized for its specific current range and reducing overall switching losses.
Solution Approach 2:
The control system dynamically selects which plurality of switching elements to activate based on the operational mode (traction or charging). During motor propulsion, the first plurality is activated to handle high currents; during charging, the second plurality is activated for lower currents. This dynamic switching between different semiconductor groups optimizes efficiency for each operational state.
3Loss of energy
If low PWM frequency is used for traction motor, then switching losses are reduced, but charging efficiency decreases due to insufficient switching frequency
Solution Approach 1:
The patent implements dynamic PWM frequency adjustment based on operational mode. During traction inverter operation, a lower PWM frequency is used to minimize switching losses in the first plurality of switching elements handling high currents. During charger operation, the PWM frequency is increased to optimize charging efficiency for the second plurality of switching elements handling lower currents, thereby achieving high efficiency in both operational states.
4Loss of energy
If separate inverter and charger devices are used, then efficiency is optimized for each function, but device complexity and cost increase
Solution Approach 1:
The patent merges the functions of a separate traction inverter and a separate charger into a single integrated device. The inverter-charger combination includes a first plurality of switching elements for inverter operation and a second plurality for charger operation, both sharing common circuitry and control systems. This consolidation maintains the efficiency benefits of function-optimized semiconductors while reducing overall device complexity, component count, and system cost.
Solution Approach 2:
The patent creates a universal inverter-charger combination device that can perform both traction inverter and charger functions using a single integrated system. The device includes switching elements configured for dual purposes: the first plurality for motor propulsion and the second plurality for battery charging, allowing one device to replace two separate devices while maintaining optimal efficiency for each function through selective activation.
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 solution enables efficient simultaneous power transmission and charging without compromising efficiency, reducing semiconductor losses, and minimizing the size and weight of the device, while optimizing motor performance and lowering costs by utilizing fewer paralleled semiconductors and reducing the need for additional gate drivers.
Implementation Method 1
an inverter-charger combination that both transmits electrical power to a traction motor of an electric vehicle and provides an electrical charge to the battery of the same vehicle
Implementation Method 2
charging devices that typically accept AC power and voltage from the electric utility grid and convert that power and voltage to DC power and voltage to charge the batteries
Data Source
AI summary
An inverter-charger combination includes plurality of first and second switching elements, a capacitor, and a dual active bridge, connected in parallel to one another. The first and the second switching elements are connected in series to form switching subassemblies that are disposed in parallel and are connected to an AC source. Each of the first and the second switching elements has a first and a second contactor, and, when the first contactor is open and the second contactor is closed, an electric current flows from a rechargeable energy storage system (RESS) in direct current form to a load in AC form through the switching subassemblies to provide power to the load, and when the first contactor is closed and the second contractor is open, an electric current flows from the AC source in AC form to the RESS in DC form through the switching subassemblies to charge the RESS.