A method for controlling a heat pump system
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Solution Overview
Problem
The heating capacity of heat pump systems in electric vehicles is insufficient at low ambient temperatures, necessitating additional electrical heaters, which complicates HVAC system design and increases costs.
Innovation Solution
The electric motor driving the compressor is controlled in a non-optimal mode to increase heat losses and recover heat, enhancing the heat pump system's performance by switching between two control modes based on heating demands, thereby omitting the need for additional heaters at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electric motor is controlled in the first control mode with highest efficiency, then the efficiency of the electric motor is improved, but the heating capacity of the heat pump system is insufficient at low ambient temperatures
Solution Approach 1:
The control system dynamically switches between two control modes for the electric motor based on heating demand conditions. The first control mode operates the motor at or close to the MTPA-line for maximum efficiency, while the second control mode operates the motor to generate additional heat losses for heating the working fluid. This dynamic adaptation allows the system to optimize between efficiency and heating capacity according to ambient temperature and heating requirements.
Solution Approach 2:
The invention changes the operating parameters of the electric motor by switching between different control modes. In the second control mode, the motor is deliberately operated with higher current and increased heat losses compared to the first control mode. This parameter change transforms the motor from purely a drive component to a dual-function component that also serves as a heat source for the heat pump system.
2Power
If the electric motor is controlled in the second control mode to increase heat losses, then the heating capacity of the heat pump system is improved, but the efficiency of the electric motor is decreased
Solution Approach 1:
The invention converts the harmful effect of increased heat losses in the electric motor into a beneficial heating source for the heat pump system. By deliberately operating the motor in the second control mode with higher current and increased resistive losses, the previously wasted thermal energy is now utilized to heat the working fluid, thereby increasing the overall heating capacity of the system without requiring additional heating devices.
3Power
If an additional electrical heater is provided to increase heating capacity, then the heating capacity is improved, but the device complexity and cost are increased
Solution Approach 1:
The invention makes the electric motor multi-functional by enabling it to serve both as a drive motor for the compressor and as a heat source for the heat pump system. Through the second control mode, the motor's stator windings and core are utilized as heating elements that transfer heat to the working fluid. This eliminates the need for separate heating devices such as resistance heaters or additional heater cores, thereby reducing system complexity and cost while maintaining adequate heating capacity across a wide range of ambient temperatures.
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 approach increases the maximal heating capacity of the heat pump system while maintaining efficiency, reducing the complexity and cost of the HVAC system by utilizing the electric motor as a heat source to enhance the heating capacity and avoid additional heating devices.
Implementation Method 1
The electric motor is controlled in a way creating higher heat losses of the electric motor for a given output torque of the electric motor in the second control mode than in the first control mode
Implementation Method 2
recovering heat emitted from the electric motor by heating the working fluid
Data Source
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AI summary
The invention relates to a method for controlling a heat pump system (1; 10). The heat pump system comprises a compressor (2; 20) for compressing a working fluid (3; 30) of the heat pump system and an electric motor (4; 40) for providing an output torque for driving the compressor. The method comprises the steps of recovering heat emitted from the electric motor by heating the working fluid, providing a first control mode and a second control mode for the electric motor (4; 40), and controlling the electrical motor in a way creating higher heat losses of the electric motor for a given output torque of the electric motor in the second control mode than in the first control mode.