Self-Commutated Inverter Control for Zero-Sequence Oscillation Damping
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Solution Overview
Problem
Self-commutated inverters with output filters coupled to a DC circuit experience oscillations in filter input currents due to resonant frequencies, which stress filter components and electronic switches, and existing solutions require additional components or complex active circuits.
Innovation Solution
Control the electronic switches of a self-commutated inverter using space vector modulation to regulate the zero-sequence voltage of the filter input voltages, suppressing oscillations by modifying the time ratio of zero-sequence space vectors and incorporating a proportional controller to dampen these oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If damping resistors are introduced to reduce resonant oscillations, then oscillation amplitude is reduced, but additional installation space is required and energy losses increase
Solution Approach 1:
The invention changes the control parameters of the inverter by introducing a zero-sequence voltage component through modified space vector modulation. This parameter change allows the system to suppress resonant oscillations without adding physical damping components, thereby avoiding energy losses and additional installation space requirements
Solution Approach 2:
The invention replaces the mechanical/passive damping approach (using physical resistors) with an electronic control approach. By using zero-sequence voltage control through modified space vector modulation, the system achieves oscillation suppression without mechanical or passive electrical components, eliminating the associated energy losses and space requirements
2Stability of the object's composition
If additional components such as common-mode inductors or capacitors are added to reduce resonant oscillations, then oscillation damping is improved, but device complexity and installation space increase
Solution Approach 1:
The invention extracts the oscillation suppression function from the physical filter components and transfers it to the control system. By removing the need for additional damping components like common-mode inductors or capacitors, the invention simplifies the filter topology while maintaining oscillation damping through zero-sequence voltage control
Solution Approach 2:
The space vector modulation system is given a dual function: it continues to perform its primary role of controlling the inverter output while simultaneously suppressing resonant oscillations through zero-sequence voltage injection. This multi-functionality eliminates the need for separate damping components, reducing device complexity and installation space
3Stability of the object's composition
If the connection to the DC circuit is disconnected to prevent common-mode currents, then oscillations are reduced, but the filtering effect for common-mode disturbances is lost
Solution Approach 1:
The invention uses feedback control through zero-sequence voltage injection to actively suppress common-mode oscillations. The control system continuously monitors and adjusts the zero-sequence voltage component to counteract oscillations, maintaining suppression capability while preserving the DC circuit connection and its associated common-mode filtering benefits
Data Source
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AI summary
The invention relates to a method for operating a self-commutated inverter (1), which is supplied from a direct voltage circuit (3) and comprises electronic switches (S1, S2, S3) for producing a three-phase output voltage and a three-phase output filter (5) which is connected downstream of the electronic switches (S1, S2, S3) and is coupled to the direct voltage circuit (3). The electronic switches (S1, S2, S3) are controlled in an open-loop manner by space-vector modulation, in which a zero-phase-sequence system voltage is controlled in a closed-loop manner by filter-input voltages of the output filter (5) on the basis of a target-voltage space vector (uα , β_ s) of the space-vector modulation and filter input currents (i1_in, 12_in, i3_in) of the output filter (5) such that oscillations in a zero-phase-sequence system of the filter input currents (i1_in, 12_in, i3_in) are suppressed.