Inverter Reactive Power Control for Energy Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power conversion apparatuses fail to effectively utilize inverters after switching from inverter-driven to commercial AC power supply-driven operation during synchronous incorporation, leading to inefficient energy usage.
Innovation Solution
A power conversion apparatus with enhanced control units and detection systems that adjust speed and output voltage to match AC power supply and inverter parameters, allowing the inverter to operate in parallel with the AC power supply without shock and perform reactive power control, ensuring efficient energy utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the inverter is switched off after synchronous incorporation to AC power supply driving, then the system operates with commercial AC power supply, but the inverter capacity is wasted and energy efficiency deteriorates
Solution Approach 1:
The inverter is designed to perform multiple functions: it can drive the AC motor directly during variable frequency driving mode, and it can also function as a reactive power compensator during fixed frequency driving mode with AC power supply. This multi-functionality resolves the contradiction by ensuring the inverter remains useful and contributes to energy efficiency even after switching to AC power supply operation.
Solution Approach 2:
The control mode of the inverter is changed based on operating conditions. During variable frequency driving, the inverter operates in motor driving mode with PWM control. During fixed frequency driving with AC power supply, the inverter switches to reactive power compensating mode where it controls reactive power output while maintaining synchronization with the AC power supply. This parameter change in control mode allows the inverter to adapt its function and prevent energy waste.
2Reliability
If the inverter operates in parallel with AC power supply for synchronous incorporation, then shock-free switching is achieved, but the system complexity increases due to additional control requirements
Solution Approach 1:
Before switching to AC power supply driving mode, the system performs preliminary synchronous incorporation control. The control unit adjusts the inverter's output voltage and frequency to match the AC power supply parameters, and synchronizes the phase. This preliminary action ensures smooth, shock-free transition and reliable operation when the inverter operates in parallel with the AC power supply during mode switching.
Solution Approach 2:
The control unit continuously monitors the operating mode and automatically adjusts control parameters based on feedback. When detecting fixed frequency driving conditions, it switches to reactive power compensating mode and maintains synchronization with AC power supply through continuous feedback control. This feedback mechanism manages system complexity by providing automated, adaptive control rather than requiring manual intervention.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A power conversion apparatus comprises, a converter 31 that receives a three-phase AC power supply 1 and outputs a DC voltage, an inverter 32 that is connected to the output of the converter 31 and drives the AC motor 5 via the output switch 4, a power switch 6 for directly driving an AC motor 5 from the AC power supply 1, a current detector 12 for detecting the output current of the inverter 32, a voltage detector 14 and a current detector 13 for detecting the voltage and current of the power supply system on the input side of the converter 3, respectively, and a control unit 7 for controlling the three-phase output voltage of the inverter 32 based on the voltage command of three phases. The control unit 7 includes a vector control unit that performs vector control of the AC motor 5 and a synchronous incorporation controller 83. The synchronous incorporation controller 83 switches to operate the inverter 32 as a reactive power controller for the power supply system after closing the power switch 6 to synchronize the AC motor 5 with the AC power supply 1.