Voltage Converter Control to Limit Heat in EV Power Conversion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electric power conversion systems for electric vehicles generate excessive heat due to high currents, particularly when supplying power to traveling motors, leading to inefficiencies and potential overheating in switching elements and reactors.
Innovation Solution
An electric power conversion system that includes an inverter, a voltage converter with switching elements and a reactor, and a controller that adjusts voltage levels based on current and power thresholds to prevent pulsating currents and heat generation, ensuring the voltage at the low-voltage end matches the high-voltage end when high currents or power is required, and prioritizes preventing overheating by maintaining switching elements in an ON state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a chopper voltage converter is used to step down voltage with switching elements, then voltage conversion function is achieved, but heat generation increases due to pulsating current and switching element on-off operations
Solution Approach 1:
The patent applies dynamics by making the voltage converter configuration adaptable based on operating conditions. The controller dynamically selects between two control modes: when the DC voltage is higher than the AC voltage, the converter operates in a mode that generates pulsating current; when the DC voltage is lower than or equal to the AC voltage, the converter operates in a mode that maintains continuous current flow. This dynamic adaptation resolves the contradiction by eliminating unnecessary switching operations and pulsating current when DC voltage is already low, thereby reducing heat generation while maintaining voltage conversion capability.
Solution Approach 2:
The patent changes the operational parameters of the voltage converter based on the voltage relationship between DC and AC sides. By monitoring the DC voltage level and comparing it with the AC voltage, the system adjusts the switching element control strategy: keeping switching elements continuously ON when DC voltage is low, and using pulsed switching when DC voltage is high. This parameter change approach allows the system to optimize between voltage conversion efficiency and heat generation reduction.
2Power
If switching elements are used for voltage step-down conversion, then voltage regulation is achieved, but heat generation increases particularly when high current flows to the motor
Solution Approach 1:
The system dynamically adjusts the switching element operation based on real-time voltage conditions. When the DC voltage drops to or below the AC voltage level, the controller transitions to a mode where switching elements remain continuously ON, eliminating the pulsating current phenomenon. This dynamic response prevents energy loss in the form of heat while maintaining the necessary voltage regulation capability through alternative control mechanisms.
Solution Approach 2:
The patent converts the potentially harmful effect of low DC voltage (which would normally require aggressive switching and cause heat generation) into a beneficial operating mode. By detecting when DC voltage is low and switching to a continuous conduction mode, the system eliminates the need for high-frequency switching operations that cause energy loss. The low voltage condition, which could be problematic, becomes the trigger for a more efficient operating regime.
3Power
If pulsating current is generated by switching element on-off operation, then voltage conversion is achieved, but heat generation in reactor and switching elements increases
Solution Approach 1:
The patent implements dynamic control by continuously monitoring the DC voltage level and adjusting the switching element operation accordingly. When DC voltage is higher than AC voltage, the system allows pulsating current for effective voltage step-down. When DC voltage equals or falls below AC voltage, the system eliminates pulsating current by maintaining continuous conduction. This dynamic adaptation resolves the contradiction between achieving voltage conversion and minimizing heat generation in the reactor and switching elements.
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
The system effectively suppresses heat generation and prevents overheating in switching elements and reactors, maintaining efficiency and reliability even under high power conditions, while allowing continuous operation without the need for additional cooling measures.
Implementation Method 1
The voltage converter includes switching elements and a reactor, and is configured to step down the voltage of the direct-current power source
Implementation Method 2
the switching element itself and a reactor generate heat
Implementation Method 3
the switching element itself and a reactor generate heat
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An electric power conversion system (2; 2a) includes: an inverter (20); a voltage converter (10; 110) including a high-voltage end connected to a direct-current power source and a low-voltage end connected to the inverter (20); and a controller (8). The controller (8) is configured to control switching elements (3a, 3b) such that a voltage of the low-voltage end becomes lower than a voltage of the high-voltage end in a first state. The controller (8) is configured to control the switching elements (3a, 3b) such that the voltage of the low-voltage end becomes equal to the voltage of the high-voltage end in a second state.