Three-Phase Inverter Grid Connection with Sequential Switching Control
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Solution Overview
Problem
Existing photovoltaic inverter grid-connected systems generate a high inrush current when connecting to an alternating current electric grid, leading to switch damage and reduced lifespan.
Innovation Solution
A three-phase alternating current grid-connected system with a controlled switching module that gradually turns on routes between the inverter module and the grid, avoiding simultaneous activation of all switches, and uses a controller to ensure specific conditions are met before activating each route, thereby preventing inrush current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If all switches are turned on simultaneously during grid connection, then the connection process is simple and fast, but a high inrush current is generated causing switch damage and reduced lifespan
Solution Approach 1:
The patent divides the three-phase grid connection process into three separate sequential steps, with each phase connected independently through its own switch (S1-S3 for phase A, B, C respectively). This segmentation allows controlled connection of each phase separately, preventing simultaneous inrush current from all three phases and thereby protecting the switches while maintaining connection functionality.
2Reliability
If switches are turned on sequentially to avoid inrush current, then switch lifespan is extended, but the control complexity increases
Solution Approach 1:
The patent implements preliminary detection of grid voltage and current conditions before each switch is turned on. The controller checks whether the grid is ready to accept each phase connection, and only permits switch activation when conditions are met. This preliminary action simplifies the control logic by providing clear activation criteria while maintaining the protective sequential connection approach.
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 reduces the probability of switch damage and prolongs the lifespan of the switching module by avoiding inrush currents during grid connection.
Implementation Method 1
The inverter module converts a direct current electric power into an alternating current electric power
Data Source
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AI summary
A controller (38) controls a first switch (S1), a second switch (S2), a third switch (S3), a fourth switch (S4), a fifth switch (S5) and a sixth switch (S6), so that an alternating current electric power is fed to an alternating current electric grid (2). Moreover, the controller (38) firstly turns on a first route including the first switch (S1) and the second switch (S2), and then the controller (38) turns on a second route including the third switch (S3) and the fourth switch (S4) if the second route meets a first specific condition, and then the controller (38) turns on a third route including the fifth switch (S5) and the sixth switch (S6) if the third route meets a second specific condition.