Dynamic DC Terminal Voltage Control for Hybrid Excavator Efficiency
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Solution Overview
Problem
Existing hybrid excavator systems experience inefficiencies due to constant direct current terminal voltage maintenance, leading to unnecessary voltage loss, especially in low-speed and high-torque regions, as they fail to adapt to varying operation conditions of swing and engine auxiliary motors.
Innovation Solution
An apparatus and method that dynamically control the direct current terminal voltage by calculating the maximum demanded voltage among inverter and converter demands, adding a predetermined margin, and adjusting the voltage accordingly, using a control unit connected to inverters, converters, and a direct current terminal capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a maximum voltage capable of encompassing all speeds and torque regions is maintained, then reliability is improved, but energy efficiency deteriorates due to unnecessary voltage loss in low-speed regions
Solution Approach 1:
The patent applies dynamics by transitioning from a static maximum voltage design to a dynamic voltage control system. The control unit calculates the actual maximum voltage required based on real-time operating conditions (motor speed, torque, inductance, current pulsatory motion) and adjusts the direct current terminal voltage accordingly. This resolves the contradiction by making the voltage adaptive - high enough to ensure reliability when needed, but reduced to minimize energy loss during low-speed operation.
Solution Approach 2:
The patent changes the voltage parameter dynamically based on operating conditions. Instead of maintaining a fixed maximum voltage, the system calculates the required voltage using parameters such as motor inductance, switching frequency, current pulsatory motion, and operating speed. This parameter-based dynamic adjustment resolves the contradiction between maintaining sufficient voltage for reliability and reducing voltage to minimize energy loss.
2Ease of operation
If a uniform reference voltage is used for all operating conditions, then ease of operation is improved, but adaptability deteriorates as the system cannot optimize for specific speed and torque regions
Solution Approach 1:
The system transitions from a static uniform reference voltage to a dynamic adaptive reference voltage. The control unit automatically calculates the appropriate reference voltage based on real-time operating conditions including motor speed, torque requirements, and electrical parameters. This dynamic approach maintains ease of operation through automated control while achieving adaptability to different operating regions.
Solution Approach 2:
The system implements feedback by continuously monitoring operating conditions (motor speed, torque, current) and using this information to adjust the reference voltage. The control unit calculates the required voltage based on feedback from the actual operating state, ensuring the system adapts to different speed and torque regions while maintaining simple automated control.
3Power
If a high direct current terminal voltage is maintained to encompass all torque regions, then power capability is improved, but energy efficiency deteriorates due to excessive voltage loss in low-speed high-torque regions
Solution Approach 1:
The patent applies dynamics by making the direct current terminal voltage adaptive to operating conditions. The control unit calculates the minimum voltage required to achieve the demanded torque at the current speed, considering motor inductance and current pulsatory motion. This dynamic voltage adjustment ensures sufficient power capability when needed while minimizing energy loss during low-speed high-torque operation.
Solution Approach 2:
The system changes the voltage parameter based on the relationship between speed, torque, and electrical characteristics. By calculating the required voltage using motor parameters (inductance, resistance) and operating conditions (speed, torque demand), the system optimizes the voltage level to achieve both adequate power capability and minimal energy loss in different operating regions.
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 improves energy efficiency and reduces power loss in the power conversion apparatus, leading to enhanced overall system efficiency and decreased cooling system power usage.
Implementation Method 1
a direct current terminal capacitor connected between the one or more inverters and the converter, and configured to receive power through the one or more inverters or collect the regenerated power through the converter
Implementation Method 2
Energy loss generated during the driving of the semiconductor switch is proportional to an output current, a switching frequency, and a direct current terminal voltage
Data Source
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AI summary
An exemplary embodiment suggested in the present specification provides an apparatus and a method of controlling a voltage of a direct current terminal of construction machinery equipped with a motor, which are capable of improving energy efficiency of a power conversion apparatus, such as an inverter and a converter by changing a voltage of the direct current terminal to an optimum voltage size in consideration of operation conditions of a swing motor, an engine auxiliary motor, and an energy storage apparatus.