Active Converter Stabilizes Intermediate Circuit Voltage
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Solution Overview
Problem
Intermediate circuits in electrical systems experience destabilization due to resonance issues caused by high-switching frequency inverters and negative input impedance behavior of power electronic consumers, leading to voltage fluctuations and instability, which can disrupt motor operations and processes.
Innovation Solution
A small, active converter is connected to the intermediate circuit via a controllable switching device, with an energy store and control system that regulates energy exchange to stabilize the voltage, acting as an active damper to counteract resonant behavior and voltage oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-switching frequency inverters are used to control electric motors, then motor control precision and response speed are improved, but resonance and voltage instability occur in the intermediate circuit
Solution Approach 1:
An active power filter is introduced as an intermediary device between the inverter and the intermediate circuit. This filter acts as a mediator that absorbs resonant frequencies and stabilizes voltage fluctuations caused by high-switching frequency operations, thereby allowing the inverter to operate at high frequencies without causing intermediate circuit instability.
Solution Approach 2:
The active power filter dynamically adjusts its operating parameters (such as switching frequency and impedance characteristics) to match and counteract the resonant frequencies generated by the inverter. By changing parameters in real-time, the system maintains voltage stability while allowing high-speed motor control.
2Loss of energy
If power electronic consumers with negative input impedance are connected to the intermediate circuit, then power conversion efficiency is improved, but voltage destabilization and resonance occur
Solution Approach 1:
The active power filter incorporates a feedback control mechanism that continuously monitors the intermediate circuit voltage and inverter current. When negative impedance effects cause voltage destabilization, the feedback system detects these changes and adjusts the filter's output to counteract the instability, thereby maintaining voltage stability while allowing efficient power conversion.
Solution Approach 2:
The active power filter converts the harmful negative impedance effect into a beneficial control signal. By detecting the conditions that lead to instability and using them to trigger compensatory actions, the system transforms the problematic negative impedance behavior into an opportunity for active stabilization.
3Stability of the object's composition
If intermediate circuit capacitors are increased to smooth voltage ripple, then voltage smoothing is improved, but resonance impedance increases at certain frequencies
Solution Approach 1:
Instead of using a fixed large capacitor value, the active power filter dynamically adjusts its equivalent capacitance through active control. This allows the system to maintain voltage smoothing benefits while avoiding the fixed resonance frequencies that occur with large passive capacitors, as the active filter can adapt its characteristics in real-time.
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 stabilizes the intermediate circuit voltage, reducing oscillations and maintaining system stability even with high-switching frequency inverters, without disrupting motor operations or processes, and allows for efficient energy exchange matching the resonance behavior of the circuit.
Implementation Method 1
an electrical energy store (46) is connected to the intermediate circuit (16) via a controllable switching device (42)
Implementation Method 2
The line inductance, together with the intermediate circuit capacitors, results in a blocking circuit that can have a high impedance at its resonant frequency
Implementation Method 3
A voltage signal of the electrical voltage of the intermediate circuit is determined and the switching device is then controlled as a function of the voltage signal determined
Data Source
Figure 1
Figure 2
AI summary
The method involves connecting electrical energy storage devices (46,52) to intermediate circuit (16) via respective controllable switching unit (42,48). Control units (44,50) determine respective voltage signal (U1,U2) fed into the intermediate circuit, and generate respective control signal (S1,S2) dependence on determined voltage signal so that power exchange between the intermediate circuit and electrical energy storage device is controlled. An independent claim is included for a circuit device for stabilizing voltage signal fed into intermediate circuit.