Asynchronous Generator Coupling With Capacitive Inrush and Shutdown Control
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Solution Overview
Problem
Existing systems for connecting asynchronous machines driven by thermodynamic circular processes directly to a power grid face challenges such as high inrush currents, potential damage from residual energy during emergency shutdowns, and increased network voltage due to inductive reactive power.
Innovation Solution
Incorporating an excitation component formed by capacitors connected to the asynchronous machine, which creates a vibration circuit with the machine's inductance, reducing inrush currents and providing a braking effect during shutdowns to manage residual energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an asynchronous machine is directly connected to the power grid without a frequency converter, then the system cost is reduced and maintenance requirements are minimized, but high inrush currents occur causing unacceptable drop in grid voltage
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor bank before connecting the asynchronous machine to the power grid. The capacitors are charged to match the grid voltage level in advance, so when the connection is made, there is no voltage difference to cause inrush current. This preparatory step eliminates the harmful inrush current effect while maintaining the simplicity of direct grid coupling.
2Device complexity
If an asynchronous machine is directly connected to the power grid, then the system becomes more robust and cost-effective, but residual energy during emergency shutdown causes the rotor to accelerate dangerously
Solution Approach 1:
The patent converts the harmful residual energy that causes dangerous rotor acceleration into a beneficial braking effect. By connecting the capacitor bank to the stator windings during shutdown, the stored electrical energy in the capacitors interacts with the rotor's residual kinetic energy, creating an electromagnetic braking effect that safely dissipates the residual energy and prevents dangerous rotor acceleration.
Solution Approach 2:
The capacitor bank serves as an intermediary element between the asynchronous machine and the power grid during emergency shutdown. Instead of directly disconnecting the machine from the grid (which would leave residual energy uncontrolled), the capacitor bank mediates the energy transfer, providing a controlled path for dissipating residual energy through electromagnetic braking.
3Device complexity
If an asynchronous machine operates as a generator directly connected to the grid, then the system is simpler, but the machine consumes inductive reactive power which increases current without benefit
Solution Approach 1:
The patent applies self-service by using the capacitor bank to provide reactive power compensation directly to the asynchronous machine. The capacitors generate reactive power locally at the machine terminals, allowing the machine to self-compensate for its inductive reactive power consumption. This eliminates the need for external reactive power compensation systems and reduces overall current in the grid connection.
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 solution effectively reduces high inrush currents, prevents rotor uncontrolled acceleration during shutdowns, and minimizes voltage fluctuations in the network, enhancing the safety and stability of the power grid connection.
Implementation Method 1
The capacitance of the capacitors can form a resonant circuit with the inductance of the asynchronous machine. Through resonance, this circuit allows a sufficiently high voltage to be excited from the very small voltage induced in the stator by the rotor remanence.
Implementation Method 2
a sufficiently high voltage to be excited from the very small voltage induced in the stator by the rotor remanence
Implementation Method 3
it can dissipate power in a braking resistor, thus acting as a brake
Data Source
Figure 1~3
Figure 4~5
AI summary
The present invention provides a generating unit, EZE (1, 36), comprising an asynchronous machine (5) with a connecting branch for direct grid connection to a power grid (11) and an energy converter (2) that operates according to a thermodynamic or fluid-dynamic process, in particular a thermodynamic cycle, and thus drives the asynchronous machine (5) to generate electricity. An excitation component (12) is provided, formed from capacitors (13) that are connected to the asynchronous machine (5) for simple, safe, and gentle grid connection.