Drive System Braking Chopper Frequency for Resonance Avoidance
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Solution Overview
Problem
Conventional drive systems face challenges in operating safely due to voltage fluctuations and resonant oscillations when using capacitors in generator-mode operations, particularly when multiple inverters are connected to a shared DC-voltage circuit.
Innovation Solution
The implementation of a drive system with additional inductance and non-polar capacitors at the DC-voltage-side connections of inverters and rectifiers, along with a braking chopper that operates at a frequency spaced from the resonant frequency, allows for safe operation by controlling voltage-dependent and time-dependent conditions to prevent oscillations. This includes using a series circuit with a resistor and controllable semiconductor switch, and digital filters to generate actuating signals for the braking chopper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a capacitor is connected at the DC-voltage-side connection of the inverter, then the voltage stability is improved, but resonant oscillations occur when the braking chopper operates at certain frequencies
Solution Approach 1:
The patent applies parameter changes by selecting a specific operating frequency for the braking chopper that is spaced apart from the resonant frequency of the LC circuit. This frequency parameter adjustment prevents excitation of resonant oscillations while maintaining voltage stability, directly resolving the contradiction between using capacitors for stability and avoiding resonant harmful effects
2Measurement precision
If the braking chopper is operated at high frequency, then the voltage control precision is improved, but the risk of exciting resonant oscillations increases
Solution Approach 1:
The patent resolves this contradiction by carefully selecting the braking chopper frequency parameter. The frequency is chosen to be high enough for adequate voltage control precision but specifically spaced apart from the resonant frequency of the LC circuit formed by the capacitor and inductance, thereby avoiding resonant oscillations while maintaining control precision
3Adaptability or versatility
If multiple inverters are connected to a shared DC-voltage circuit, then the system versatility is improved, but the interaction of inductances and capacitances creates resonant frequencies that compromise safety
Solution Approach 1:
The patent addresses this contradiction by adjusting the operating frequency parameter of the braking chopper to be spaced apart from the resonant frequency created by the interaction of inductances and capacitances in the shared DC-voltage circuit. This allows multiple inverters to operate safely together while maintaining system versatility
Solution Approach 2:
The patent introduces the braking chopper as an intermediary component that actively manages the resonant interactions in the shared DC-voltage circuit. By operating at a frequency spaced from the resonant frequency, the braking chopper mediates between the multiple inverters and the capacitive elements, preventing harmful resonances while allowing the system to maintain its versatile multi-inverter configuration
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
The solution effectively prevents resonant oscillations, ensures safe operation by maintaining voltage within specified ranges, and allows for efficient energy conversion, reducing the risk of unintentional voltage drops and maintaining frequency stability, even when multiple inverters are connected.
Implementation Method 1
the frequency, in particular, being spaced apart from the resonant frequency of the resonant circuit including the inductances and the capacitance or capacitances
Data Source
AI summary
In a method for operating a drive system, and drive system, having a rectifier and at least one inverter including an electric motor, the electric motor is connected at the AC-voltage-side connection of the inverter, the DC-voltage-side connection of the inverter is connected via inductance(s) in addition to the line inductance, to the DC-voltage-side connection of the rectifier, a capacitance is connected at the DC-voltage-side connection of the inverter and/or at the DC-voltage-side connection of the rectifier, a series circuit, including a resistor and a controllable semiconductor switch is connected at the DC-voltage-side connection of the inverter and/or at the DC-voltage-side connection of the rectifier, the braking chopper being operated using a single frequency during the particular time span in which the braking chopper is in operation, the frequency, e.g., being set apart from the resonant frequency of the resonant circuit including the inductance or the capacitances.