High-Frequency DC-DC Converter for Variable EV DC-Link Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-voltage DC links in electric vehicle power train systems increase power switching losses and decrease the performance of electric motors and inverters, particularly at lower speeds and torques, leading to inefficiencies and reduced lifespan.
Innovation Solution
Integration of a high-frequency DC-DC power converter between the energy source and the inverter, which scales and controls the DC-link voltage according to motor load conditions, optimizing efficiency and torque/power requirements while simplifying motor design and extending lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If high-voltage DC link is used in the power train system, then charging time is reduced and cable size is decreased, but power switching losses in the motor and inverter increase
Solution Approach 1:
The patent applies dynamics by making the DC-link voltage variable rather than fixed. The power train system dynamically adjusts the DC-link voltage based on operating conditions (speed, torque, power demand) using a DC-DC converter. This allows the system to operate at high voltage during high-speed/high-power conditions to reduce charging time and cable size, while switching to lower voltage during low-speed/low-torque conditions to minimize power switching losses in the motor and inverter.
Solution Approach 2:
The patent changes the voltage parameter of the DC link from a constant high value to a variable parameter that adapts to operating conditions. By implementing a DC-DC converter between the battery and inverter, the system can transform the fixed high-voltage DC link into a variable voltage source, optimizing the voltage level according to real-time motor load conditions, speed, and torque requirements.
2Power
If high-voltage DC link is used, then power transfer capability is improved, but motor and inverter performance decreases at lower speeds and torques
Solution Approach 1:
The system dynamically adapts the DC-link voltage to match motor operating conditions. During high-power demands (acceleration, high-speed cruising), the DC-link operates at high voltage to maximize power transfer capability. During low-speed/low-torque operations, the voltage is reduced to prevent excessive switching losses and maintain optimal motor and inverter efficiency, thus preserving reliability across the entire operating range.
Solution Approach 2:
The DC-DC converter acts as an intermediary device between the battery and the inverter-motor system. It mediates the voltage transformation, allowing the battery to operate at its optimal high voltage while the inverter-motor system receives appropriately scaled voltage levels matched to its instantaneous power and torque requirements, thereby maintaining performance and reliability.
3Device complexity
If fixed DC-link voltage is used to simplify electrical architecture, then system complexity is reduced, but efficiency is decreased due to inability to adapt to varying load conditions
Solution Approach 1:
The DC-DC converter is designed with multi-functionality, serving both as a voltage scaling device and as an efficiency optimization component. It integrates voltage transformation, power management, and adaptive control functions into a single device, allowing the system to maintain simplified architecture while achieving adaptive efficiency across varying load conditions through its ability to operate in different modes (boost, buck, bypass).
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 high-frequency DC-DC power converter enhances the efficiency and adaptability of the power train system, reducing losses and enabling the electric motor to meet torque and power demands during low battery state of charge, while minimizing dynamic DC-DC losses and noise vibration harshness.
Implementation Method 1
the control signal causing the half-bridge to convert the input DC signal into a switched DC signal transmitted to the inductor and the at least one capacitor
Implementation Method 2
an inductor electrically connected to the half-bridge, and at least one capacitor electrically connected parallel to the inductor
Implementation Method 3
at least one capacitor electrically connected parallel to the inductor
Implementation Method 4
the DC-AC inverter being configured to: receive an indication of a required inverter output, and convert, based on the indication of the required inverter output and the indication the output DC signal, the output DC signal into an output AC signal
Implementation Method 5
the half-bridge being in thermal contact with a cooling system comprises a heat spreader
Data Source
AI summary
There is provided an electric dynamic drive train for electric vehicles (EVs), the electric dynamic drive train including a high frequency direct current (DC)-DC converter and a DC-alternative current (AC) inverter. The high frequency DC-DC power converter includes a DC-DC controller connected to one or more core cells comprising a driver, a half-bridge connected to the driver, the half-bridge including high and low sides transistors in thermal contact with a cooling system including a heat spreader, an inductor and a capacitor connected to the half-bridge and a capacitor connected to the inductor. The high frequency DC-DC power converter enables having an almost instantaneous response time by reducing voltage drops between transients, enables generating a clean waveform signal improving the longevity of connected components, and enables the inverter and the motor in the EVs to be sized apart from one to another.