Field-Oriented Control for Intermediate Circuit Voltage Damping
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Solution Overview
Problem
Intermediate circuits in electrical systems experience destabilization due to resonance issues caused by high switching frequencies of inverters and negative input impedance behavior of power electronic consumers, leading to inefficient energy transmission and potential disruption of motor-driven processes.
Innovation Solution
Implementing a method where a DC-AC inverter is controlled to dampen oscillations in the intermediate circuit voltage using field-oriented regulation of an electrical machine's stator current, with a control device setting a d-component of the stator current to actively dampen vibrations, mimicking ohmic resistance and reducing the intermediate circuit's impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inverter switching frequency is increased to improve power transmission speed, then energy transmission efficiency is improved, but resonance instability in the intermediate circuit worsens
Solution Approach 1:
The patent converts the harmful resonance oscillations into beneficial damping effects by introducing an artificial damping component through field-oriented control of the electrical machine. The control system generates a damping torque that opposes the resonance oscillations, effectively transforming the unstable resonant behavior into a stabilizing force that reduces voltage fluctuations in the intermediate circuit.
Solution Approach 2:
The patent changes the control parameters of the electrical machine by introducing a damping component in the field-oriented control. Specifically, a damping torque is generated by adjusting the q-axis current component based on the detected voltage fluctuation frequency, thereby changing the machine's operational parameters to achieve resonance damping without altering the physical structure.
2Stability of the object's composition
If damping control is applied to reduce intermediate circuit oscillations, then voltage stability is improved, but motor torque and process performance deteriorate
Solution Approach 1:
The patent segments the control of the electrical machine into two independent components: one for torque production (d-axis current) and another for damping (q-axis current modulation). This segmentation allows the damping function to be added without interfering with the primary torque-producing function, as each component can be controlled independently through field-oriented control techniques.
Solution Approach 2:
The patent implements dynamic damping control where the damping torque is not fixed but varies dynamically based on the detected voltage fluctuation frequency and amplitude. The control system continuously adjusts the damping component in real-time, enabling the motor to adapt its damping characteristics to match the instantaneous resonance conditions while maintaining optimal torque output.
3Stability of the object's composition
If intermediate circuit capacitance is increased to smooth voltage ripple, then voltage stabilization is improved, but system complexity and cost increase
Solution Approach 1:
The patent replaces the passive mechanical/electrical approach of using large capacitance for voltage stabilization with an active control approach. Instead of relying on the physical energy storage capability of large capacitors, the system uses field-oriented control of the electrical machine to actively counteract voltage fluctuations, thereby substituting a control system for a passive energy storage system.
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 stabilizes the intermediate circuit voltage without affecting motor torque or rotational speed, allowing for increased energy transmission and reduced ohmic losses, effectively damping oscillations and enhancing power exchange efficiency.
Implementation Method 1
a control device for controlling a stator current of the electrical machine; the damping device is designed to dampen the oscillation in the intermediate circuit voltage by means of field-oriented control of a stator current of the electrical machine
Implementation Method 2
The stator windings ( 46 ) together with the control device ( 42 ) thus together form an active intermediate circuit damper, which dampens the oscillations that occur in the intermediate circuit voltages
Data Source
Figure 1
Figure 2
AI summary
The method involves determining a time profile of oscillation of the rectified electrical voltage (U1) by a measuring device (44), based on field-oriented control of torque setting, thrust force component and perpendicular component of a q-defining stator of an electric machine (18). A set point gradient is regulated for the d-component of the stator current, as a function of the detected vibration of a controller. A control unit (42) is adapted to damp the vibration. The control unit is adjusted by the controller. An independent claim is included for a circuit device.