Synchronous Inverter Regenerative Energy Feedback Circuit
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Solution Overview
Problem
Existing solutions for regenerative energy feedback in small electric drives are costly and inefficient, as they require complex structural measures and heating of braking resistors, which are not effective for small drive units.
Innovation Solution
A method and circuit that allow regenerative energy to be fed back into the power grid by using a synchronous inverter connected to the DC voltage intermediate circuit of a frequency converter, eliminating the need for a braking resistor and simplifying the circuit structure, with a DC-DC converter providing clocked and averaged current blocks for energy feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a braking resistor is used to dissipate regenerative energy, then the energy can be converted into heat and released into the environment, but the structural complexity increases and the cost increases due to the need for large braking resistors and sufficient cooling measures
Solution Approach 1:
The invention extracts the braking resistor from the frequency converter structure by using a brake chopper circuit that can be arranged outside the frequency converter. This separates the energy dissipation function from the main converter structure, reducing the structural complexity and cooling requirements while maintaining the energy dissipation capability.
Solution Approach 2:
The invention introduces a brake chopper as an intermediary component between the DC link and the braking resistor. This chopper circuit controls the discharge of regenerative energy to the braking resistor, providing a simplified interface that reduces the structural complexity compared to direct connection schemes.
2Loss of energy
If a converter with high-quality power transistors and complex mains filter is used to feed regenerative braking power back into the power network, then energy feedback is achieved, but the investment costs increase significantly
Solution Approach 1:
The invention extracts only the essential power electronics components needed for energy feedback from the complex converter system. By using a DC-DC converter and synchronous inverter instead of a full complex converter, it achieves energy feedback functionality while significantly reducing investment costs, especially for small drive units.
Solution Approach 2:
The invention changes the operating parameters and topology of the power electronics system by using a DC-DC converter stage followed by a synchronous inverter. This parameter change allows for simpler and more cost-effective implementation compared to traditional high-complexity converter solutions, making energy feedback economically viable for small drives.
3Loss of energy
If a synchronous inverter is used to feed energy back into the power grid, then regenerative energy feedback is enabled, but the circuit structure becomes more complex
Solution Approach 1:
The invention segments the energy feedback system into distinct functional stages: a DC-DC converter stage for energy conversion and a synchronous inverter stage for grid injection. This segmentation allows each stage to be optimized independently and simplifies the overall circuit structure compared to integrated solutions, making the system more manageable and easier to implement.
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 enables efficient and cost-effective regenerative energy feedback in small drives without additional costs to the frequency converter, allowing for easy retrofitting of existing systems and reducing structural complexity, while maintaining optimal control of the synchronous inverter.
Implementation Method 1
a DC voltage converter (9, 12) which is fed from a DC voltage intermediate circuit (3, 13) of the frequency converter (1, 1')
Implementation Method 2
a synchronous inverter (10, 10') which is connected downstream of the DC voltage converter (9, 12)
Implementation Method 3
a mains filter (11, 11') which is connected downstream of the synchronous inverter (10, 10')
Implementation Method 4
switches an inductance, the switching frequency being variable or constant
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a method for operating an electric motor in a generator mode, said electric motor being connected to at least three phases of a power supply network. An energy that is to be fed back into the power supply network (L1, L2, L3) is connected from a DC voltage intermediate circuit (3) of a frequency converter (1) to the network phase of the highest voltage as an intermittent and averaged power block by a synchronous inverter (10). A circuit is used in which a DC-DC converter (9) is fed from a DC voltage intermediate circuit (3) of the frequency converter (1), wherein a synchronous inverter (10) is connected downstream of the DC-DC converter and a network filter (11) is connected downstream of the synchronous inverter (10).