Virtual Synchronous Generator Control for Strong-Grid Power Oscillation
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Solution Overview
Problem
Existing virtual synchronous generators (VSGs) face instability in strong grids due to oscillating output power, and existing stability control methods are either costly or inapplicable to inner-loop-free VSGs, which lack the necessary hardware components for virtual grid-side inductance control.
Innovation Solution
A stability control method using inductance-current differential feedback is introduced, implementing virtual series-connection inductance through a three-phase LC filter, allowing for stable operation in strong grids without additional hardware costs by controlling the modulation voltage in the VSG.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If virtual grid-side inductance control strategy is used to stabilize VSG in strong grids, then stability is improved, but hardware cost increases due to requiring grid-side current sensor
Solution Approach 1:
The patent uses the inverter-side filter inductance current as a substitute (copy) for the unavailable grid-side inductance current. By processing this available current signal through differential feedback control, the system achieves virtual grid-side inductance control without requiring additional current sensors, thus resolving the contradiction between stability and hardware cost.
Solution Approach 2:
The patent introduces an intermediary control mechanism (inductance-current differential feedback) that transforms the inverter-side filter inductance current into an effective virtual grid-side inductance control signal. This intermediary approach enables stability control without direct grid-side current measurement, avoiding additional hardware costs.
2Ease of operation
If inner-loop-free VSG control is used to simplify control scheme, then ease of operation is improved, but stability deteriorates in strong grids due to inability to implement virtual grid-side inductance control
Solution Approach 1:
The patent dynamically adjusts the control strategy by introducing inductance-current differential feedback that adapts to grid conditions. This dynamic approach maintains the simplicity of inner-loop-free control while enabling stability in strong grids through the additional differential feedback mechanism that activates when needed.
Solution Approach 2:
The patent incorporates feedback control by using the inverter-side filter inductance current and its differential to regulate the output. This feedback mechanism enables the simplified inner-loop-free VSG to achieve virtual grid-side inductance control, resolving the stability issue while maintaining control scheme simplicity.
3Reliability
If filter inductance is added to implement stable operation of inner-loop-free VSG in strong grids, then stability is improved, but hardware cost increases
Solution Approach 1:
The patent creates a virtual copy of the grid-side inductance effect using the inverter-side filter inductance current signal. By processing this existing signal through differential feedback, the system achieves the stabilizing effect of additional inductance without physically adding filter inductance, thus avoiding increased hardware cost.
Solution Approach 2:
The patent replaces the mechanical/physical addition of filter inductance with a control-theoretic solution (inductance-current differential feedback). This substitution achieves the same stabilizing effect through signal processing and control algorithms rather than physical hardware modification, eliminating the need for additional inductance components.
Data Source
AI summary
A stability control method for a virtual synchronous generator (VSG) in a strong grid based on an inductance-current differential feedback is provided. A grid-connected topological structure of a VSG using the control method includes a direct-current (DC)-side voltage source, a three-phase inverter, a three-phase grid impedance and a three-phase grid. By controlling the VSG and controlling the inductance-current differential feedback, the method suppresses the oscillation of the output power from the VSG in the strong grid and implements the stable operation of an inner-loop-free VSG in the strong grid, without adding the physical inductance, increasing the cost of the filter and additionally providing a grid-side current sensor.