Inverter Control Apparatus Phase Synchronization for Seamless Grid Switching
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Solution Overview
Problem
Conventional voltage inverter systems experience electric shocks during the switching operation from inverter output to commercial power source, making it difficult to apply the multi-soft starter method to voltage motors and posing challenges during inverter maintenance or failure.
Innovation Solution
A voltage inverter control apparatus synchronizes the sizes and phases of commercial and inverter output voltages, and installs a reactor between the two power sources to minimize electric shocks, allowing seamless switching and maintaining motor operation during inverter repairs or failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching is implemented between inverter output and commercial power source, then motor operation continuity is improved, but electric shock is generated due to voltage difference
Solution Approach 1:
The control apparatus synchronizes the phase and frequency of the inverter output voltage with the commercial power source voltage before switching occurs. This preliminary synchronization ensures that voltage levels match, preventing electric shock during the transition while maintaining continuous motor operation
Solution Approach 2:
The control apparatus acts as an intermediary by monitoring and adjusting the inverter output to match the commercial power source parameters. It controls the switching timing and ensures smooth transition, preventing direct conflict between mismatched voltage sources that would cause electric shock
2Ease of operation
If multi-soft starter method is applied to voltage motors, then sequential motor starting is improved, but electric shock prevents application
Solution Approach 1:
Before each motor starts or before switching between power sources, the control apparatus pre-synchronizes the voltage parameters. This preliminary action ensures that the voltage match is achieved before the motor starts or before switching, eliminating electric shock and enabling safe application of multi-soft starter method to voltage motors
Solution Approach 2:
The control apparatus dynamically adjusts the inverter output voltage parameters (frequency, phase, amplitude) to match the commercial power source. By changing these parameters in real-time, it ensures voltage compatibility during sequential motor starting operations, preventing electric shock
3Adaptability or versatility
If inverter output is switched to commercial power source, then power supply flexibility is improved, but voltage collision occurs
Solution Approach 1:
The control apparatus continuously monitors both the inverter output voltage and the commercial power source voltage. Based on this feedback, it adjusts the inverter parameters and controls the switching timing to prevent voltage collision, enabling flexible power supply switching without harmful effects
Solution Approach 2:
The system changes the inverter output parameters (frequency, phase, voltage magnitude) to match the commercial power source before switching. This parameter adjustment prevents voltage collision by ensuring both sources are compatible when connected to the same motor load
Data Source
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Figure 3~4
AI summary
An exemplary embodiment of the present disclosure includes a medium voltage inverter control apparatus and a medium voltage inverter system using the same. The medium voltage inverter control apparatus determines input voltage information by receiving an input voltage of a medium voltage inverter, compares an output command of the medium voltage inverter with an output of a first PLL unit to output a difference therebetween, and synchronizes the output command of the medium voltage inverter using the difference.