Paired Three-Phase Transformers for Harmonic Suppression
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Solution Overview
Problem
In motorized container yards, harmonic waves generated during AC/DC conversion in crane apparatuses leak into the commercial power system, causing adverse effects, and existing harmonic suppression methods are expensive and burdensome.
Innovation Solution
The implementation of a container yard system with paired three-phase transformers, where one outputs first three-phase AC power and the other outputs second three-phase AC power with a π/6 voltage phase shift, combined with a three-phase full-wave rectifier and power storage device, to cancel fifth and seventh harmonic waves and reduce harmonic leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If three-phase full-wave rectifier is used for AC/DC conversion in crane apparatus, then power conversion efficiency is improved, but harmonic waves are generated and leak into commercial power system
Solution Approach 1:
The patent applies the principle of converting harm into benefit by using the harmonic waves generated by the three-phase full-wave rectifier not as unwanted byproducts but as useful signals. The system detects these harmonic waves and utilizes them for phase detection and synchronization purposes, thereby eliminating the need for separate detection equipment and reducing harmonic leakage into the commercial power system.
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of a harmonic wave detection unit that acts as a mediator between the rectifier and the power system. This unit detects harmonic waves and provides phase information to the control system, enabling synchronized control without directly injecting additional harmonic content into the power system.
2Object-generated harmful factors
If expensive equipment like PWM converters or high-frequency filters is installed to suppress harmonic waves, then harmonic leakage is reduced, but initial investment cost increases
Solution Approach 1:
The patent replaces expensive, complex harmonic suppression equipment with a cost-effective solution based on simple harmonic wave detection and control. Instead of using costly PWM converters or high-frequency filters, the system uses inexpensive detection circuits and software-based control to achieve harmonic suppression, dramatically reducing initial investment costs.
Solution Approach 2:
The patent changes the operational parameters of the crane apparatus by implementing phase-controlled power supply based on detected harmonic waves. By adjusting the phase and timing of power supply to match the harmonic wave patterns, the system achieves harmonic suppression through parameter optimization rather than through expensive hardware modifications.
3Object-generated harmful factors
If phase detection equipment is added to detect harmonic waves, then harmonic suppression control is improved, but device complexity increases
Solution Approach 1:
The patent makes the detection unit multi-functional by designing it to simultaneously detect harmonic waves, determine phase information, and provide synchronization signals for power supply control. This single unit performs multiple functions that would otherwise require separate devices, thereby reducing overall system complexity while improving harmonic suppression control.
Solution Approach 2:
The system implements self-service by using the harmonic waves generated by its own rectifier as the detection signal source. The crane apparatus detects and utilizes its own harmonic emissions for phase detection and synchronization, eliminating the need for external detection equipment or additional signal sources, thereby simplifying the overall system architecture.
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 configuration effectively suppresses fifth and seventh harmonic waves, reducing their levels and the initial investment required for harmonic suppression, allowing for a low-cost harmonic measure without the need for expensive equipment like PWM converters or high-frequency filters.
Implementation Method 1
a three-phase full-wave rectifier configured to perform full-wave rectification of the operating power supplied from the feeder line and to supply obtained DC power to a common bus
Implementation Method 2
one of two paired three-phase transformers among the three-phase transformers is constituted by a first three-phase transformer configured to output, as the operating power, first three-phase AC power of the same voltage phase as a voltage phase of the power-supply power, and the other three-phase transformer of the two paired three-phase transformers is constituted by a second three-phase transformer configured to output, as the operating power, second three-phase AC power of a voltage phase shifted by α/6 from the voltage phase of the power-supply power
Data Source
AI summary
One three-phase transformer (71A) out of two paired three-phase transformers among three-phase transformers provided for respective feeder lines outputs, as operating power, first three-phase AC power of the same voltage phase as that of power-supply power. The other three-phase transformer (71B) out of the two paired three-phase transformers outputs, as the operating power, second three-phase AC power of a voltage phase shifted by π/6 from that of the power-supply power. The power storage device (4) of a crane apparatus (10) stores DC power supplied from a three-phase full-wave rectifier (1) to a common bus (B), and supplies the stored power to the common bus (B) upon reduction of the DC power.