Full-State Virtual Oscillator Control for Grid-Forming PV Stability
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Solution Overview
Problem
Existing grid-forming control strategies for photovoltaic and energy storage systems fail to effectively address large disturbances on AC and DC sides, leading to instability and overcurrent issues, as they do not adequately consider the physical characteristics of the energy source, resulting in potential DC bus voltage collapse and interaction problems with conventional synchronous machines.
Innovation Solution
A grid-forming control method using a full-state virtual oscillator that includes a control model with frequency and voltage amplitude, a constraint current inner loop, and adjusted control parameters to stabilize operation, incorporating load reduction policies and current inner loop mechanisms to enhance adaptability and suppress overcurrent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing virtual oscillator control policy is used, then grid-forming characteristic is improved, but system stability under large disturbance deteriorates
Solution Approach 1:
The patent implements dynamic adjustment of control parameters (η, μ, kdc, koc) based on system operating conditions and disturbance levels. The controller transitions from static parameter control to dynamic parameter adaptation, allowing the system to maintain stability under varying disturbance conditions while preserving grid-forming characteristics.
Solution Approach 2:
The patent changes the parameters of the virtual oscillator controller (active synchronous control parameter η, amplitude control parameter μ, DC voltage control parameter kdc, overcurrent suppression control parameter koc) to adapt to different operating conditions. This parameter optimization resolves the contradiction by tuning the system response to maintain both grid-forming capability and disturbance stability.
2Reliability
If existing virtual oscillator control policy is used, then grid-forming characteristic is improved, but overcurrent suppression capability deteriorates
Solution Approach 1:
The patent introduces feedback mechanisms through the constraint control model of the current inner loop and dynamic parameter adjustment. The controller continuously monitors system state and adjusts parameters to suppress overcurrent transients, resolving the contradiction by adding active feedback control that maintains grid-forming characteristics while eliminating overcurrent issues.
Solution Approach 2:
The patent introduces an intermediary constraint control layer between the virtual oscillator control and the power conversion system. This intermediate control structure mediates between the grid-forming requirements and overcurrent suppression needs, allowing both objectives to be achieved simultaneously through coordinated control.
3Device complexity
If ideal voltage source assumption is used, then control simplicity is improved, but DC bus voltage stability deteriorates
Solution Approach 1:
The patent transitions from static ideal voltage source assumption to dynamic DC voltage control that accounts for actual power electronics characteristics. The DC voltage control parameter kdc is dynamically adjusted based on power balance between DC side power supply and AC side synchronous grid-forming characteristics, resolving the contradiction by maintaining control simplicity while achieving voltage stability.
Data Source
AI summary
A grid-forming control method with full-state virtual oscillator for photovoltaic and energy storage system includes: establishing a control model of the full-state virtual oscillator, where the control model of the full-state virtual oscillator includes a frequency and a voltage amplitude; establishing a constraint control model of a current inner loop; and according to the control model of the full-state virtual oscillator and the constraint control model of the current inner loop, adjusting control parameters of the full-state virtual oscillator, where the control parameters are used to control the stable operation of grid-forming photovoltaic and energy storage systems.