Hybrid Construction Machine DC Bus Voltage Control for Safe Capacitor Charging
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Solution Overview
Problem
In hybrid-type construction machines, newly assembled or replaced electric power accumulators, such as capacitors, often remain uncharged, leading to a 0 V output terminal voltage, and existing charging methods can result in excessive charging currents when the accumulator has low voltage, potentially damaging the device.
Innovation Solution
A hybrid-type construction machine with a control system that manages the charging of electric power accumulators by initially using a lower DC bus voltage and adjusting the voltage reference value based on the motor generator's induced voltage and the accumulator's state, preventing excessive current flow and ensuring safe and effective charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a newly assembled or replaced electric power accumulator is charged using conventional charging methods, then the accumulator can be charged, but excessive charging current flows when the accumulator has low voltage (0 V), potentially damaging the device
Solution Approach 1:
The patent applies dynamics by making the DC bus voltage reference value changeable based on operating conditions. Specifically, the reference value is set to a lower value during initial charging when the electric power accumulator has low voltage, and then increased to a higher value after charging progresses. This dynamic adjustment of the voltage reference prevents excessive charging current while ensuring efficient charging completion.
Solution Approach 2:
The patent applies parameter changes by modifying the DC bus voltage reference value parameter according to the charging state. The control system detects the voltage of the electric power accumulator and adjusts the DC bus voltage reference accordingly - using a first (lower) reference value when voltage is low and a second (higher) reference value when voltage increases, thereby optimizing charging current throughout the process.
2Productivity
If the DC bus voltage reference value is set high to ensure efficient charging, then charging speed improves, but excessive current flows when the accumulator voltage is low, causing potential damage
Solution Approach 1:
The patent applies dynamics by making the DC bus voltage reference value changeable based on operating conditions. Specifically, the reference value is set to a lower value during initial charging when the electric power accumulator has low voltage, and then increased to a higher value after charging progresses. This dynamic adjustment of the voltage reference prevents excessive charging current while ensuring efficient charging completion.
Solution Approach 2:
The patent applies preliminary action by setting a lower DC bus voltage reference value before charging begins when the accumulator voltage is unknown or low. This preliminary conservative setting prevents excessive current from flowing at the start of charging, protecting the device from damage before the charging process fully establishes the voltage levels.
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 allows for safe and efficient initial charging of electric power accumulators, preventing excessive current and ensuring the accumulator is charged without damage, while also managing charging currents to maintain operational safety and efficiency.
Implementation Method 1
a motor generator which assists an engine... the assist motor is driven by the engine to generate electricity
Data Source
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AI summary
A disclosed hybrid-type construction machine includes a generator part (12) configured to generate electric energy by the driving force of an engine (11); an inverter (18A) configured to control the generator part (12); an electric power accumulator (120) configured to accumulate the electric energy generated by the generator part (12); a DC bus located between the generator part (12) and the electric power accumulator (120); and a converter (100) configured to control a voltage of the DC bus, wherein when the electric power accumulator (120) having approximately zero electric energy is charged the inverter (18A) of the generator part is not controlled, and a reference value of a voltage command for the DC bus to charge the electric power accumulator is set to be smaller than an induced voltage of the generator part (12).