Variable Voltage Inverter Duty Cycle Control
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Solution Overview
Problem
Existing vehicle inverters face inefficiencies in electrical power use by electric machines due to voltage output being above or below the optimal range, leading to suboptimal propulsion and regeneration capabilities.
Innovation Solution
A variable voltage control inverter system that adjusts the duty cycle of transistors responsive to battery voltage, allowing for precise control of output voltage, reducing over-boosting, and enhancing voltage boost capability in both buck and boost modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the inverter operates in boost mode to increase battery voltage, then the output voltage can be increased above battery voltage, but the voltage output may be above or below the optimal range for electric machine efficiency
Solution Approach 1:
The inverter employs dynamic voltage control by adjusting the duty cycle of switching transistors in real-time based on battery voltage conditions. This allows the output voltage to be dynamically optimized to match the electric machine's efficient operating range, rather than using fixed voltage levels. The system continuously adapts the boost ratio to maintain optimal efficiency across varying operating conditions.
Solution Approach 2:
The system changes the operating parameters of the inverter by monitoring battery voltage and adjusting the duty cycle accordingly. When battery voltage is low, the duty cycle is increased to provide greater voltage boost; when battery voltage is high, the duty cycle is reduced to prevent over-boosting. This parameter adjustment ensures the output voltage remains within the optimal range for electric machine efficiency.
2Power
If the inverter provides voltage boost capability, then higher output voltages can be achieved, but over boosting occurs when battery charge is low
Solution Approach 1:
The inverter incorporates feedback control by continuously monitoring battery voltage and using this information to adjust the duty cycle of the switching transistors. This closed-loop control prevents over-boosting by reducing the duty cycle when battery voltage is already high, and allows maximum boost when battery voltage is low. The feedback mechanism ensures precise control of the output voltage within the optimal range for electric machine operation.
3Device complexity
If the inverter uses fixed duty cycle switching, then the control is simple, but the electrical power use by the electric machine is less efficient
Solution Approach 1:
The system transitions from fixed duty cycle control to dynamic duty cycle control based on real-time battery voltage conditions. The controller adjusts the duty cycle of the switching transistors according to the battery state, enabling the inverter to adapt its voltage conversion ratio dynamically. This maintains electrical power efficiency across varying operating conditions while adding only moderate control complexity.
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
Improves electrical system efficiency, enhances battery charging efficiency, and allows for higher voltage boosting, optimizing electric machine performance and battery charging.
Implementation Method 1
battery voltage may be increased via storing electric energy in a magnetic field of an inductor and then discharging the inductor to the electric machine
Data Source
AI summary
Systems and methods for operating an inverter that is electrically coupled to a battery and an electric machine that provides propulsive force to vehicle are described. The systems and methods may selectively adjust a duty cycle of an inverter transistor responsive to battery voltage and a dead time between when a first transistor is deactivated and when a second transistor is activated.