UPS Voltage Compensation for Cable Impedance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In three-phase four-line power feeding methods, voltage drops due to cable impedance variations lead to non-uniform voltages across phases, making it difficult for uninterruptible power supply devices to provide stable power to single-phase loads, thereby reducing reliability.
Innovation Solution
The implementation of a smoothing circuit with capacitors, an inverter, current and voltage sensors, and a controller with a compensation circuit to adjust output voltage commands and compensate for voltage drops in the three-phase AC line, ensuring balanced voltage delivery across phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If cable length increases to extend power supply distance, then power supply coverage is improved, but voltage drop increases and voltage stability deteriorates
Solution Approach 1:
The system performs preliminary measurement of cable impedance before power supply operation, and pre-calculates the appropriate voltage drop compensation amount. This allows the inverter to output adjusted voltage from the start, preventing voltage instability rather than reacting to it afterward.
Solution Approach 2:
The system continuously monitors actual voltage at the load end and compares it with the target voltage. Based on the detected voltage deviation caused by cable impedance, the system automatically adjusts the inverter output voltage to maintain stable voltage at the load, creating a closed-loop feedback control mechanism.
2Adaptability or versatility
If cable impedance varies across phases due to different cable lengths, then power distribution flexibility is improved, but voltage uniformity across phases deteriorates
Solution Approach 1:
The system measures and identifies the specific impedance characteristics of each phase cable individually. Based on the detected impedance differences across phases, the system applies phase-specific voltage compensation, adjusting each phase's output voltage according to its unique cable characteristics to maintain uniform voltage at the load end.
Solution Approach 2:
The system dynamically changes the output voltage parameters of the inverter based on detected cable impedance values. By adjusting voltage magnitude and phase angle parameters according to measured impedance differences, the system compensates for unequal voltage drops and maintains voltage uniformity across all phases despite varying cable lengths.
Data Source
AI summary
A generation circuit is configured to generate an output voltage command value Vor* for an inverter based on a three-phase reference value Vr, a zero-phase reference value, a detected value of a current sensor, and a detected value of a voltage sensor. A compensation circuit is configured to compensate for a voltage drop in a three-phase AC line when three-phase AC power is supplied from the inverter to an AC load. A corrector is configured to correct the output voltage command value Vor* based on a compensation command value Vol. A control circuit is configured to control the inverter based on an output voltage command value Vo* corrected by the corrector.