As renewable penetration surges, advanced grid control technologies become critical for solar+storage systems.
PQ (Grid-Following), VF (Grid-Forming), and VSG (Virtual Synchronous Generator) modes empower inverters to balance energy flow, stabilize microgrids, and support grid resilience. Here’s how they work.
Control Modes Explained
1. PQ Mode (Grid-Following)
Core Function: Precisely regulates active power (P) and reactive power (Q) by synchronizing with the grid’s voltage phase.
Applications:
Peak shaving/valley filling via scheduled charging/discharging.
Grid support through reactive power compensation (e.g., voltage regulation).
Limitation: Relies on external grid stability. Fails during blackouts.
Ideal For: Grid-tied commercial solar+storage projects requiring revenue-generating functions like frequency regulation and energy arbitrage.
2. VF Mode (Grid-Forming)
Core Function: Establishes independent voltage and frequency references for off-grid systems using dual-loop voltage/current control.
Applications:
Powering critical loads (medical equipment, telecom) in islands or remote mines.
Emergency backup during main grid failures.
Challenge: Requires synchronization for multi-unit parallel operation.
Ideal For: Off-grid microgrids demanding stable standalone power.
3. VSG Mode (Virtual Synchronous Generator)
Core Function: Mimics synchronous generator dynamics via virtual inertia and damping. Simulates rotor motion equations to provide:
Frequency support during disturbances.
Voltage stabilization through reactive power control.
Breakthroughs:
Adaptive AI-driven algorithms reduce power-sharing errors to <1%.
Seamless grid-to-island transition capability.
Ideal For: High-renewable penetration grids needing inertia emulation and black start capability.
Real-World Applications
| Mode | Use Cases | Project Example |
|---|---|---|
| PQ | Grid-tied peak shaving, frequency regulation | Industrial park PV+storage optimization |
| VF | Island microgrids, emergency backup systems | Remote mining site power resilience |
| VSG | Utility-scale renewable integration, weak grid support | 1,000+ VSG inverters in Red Sea microgrid |
The Future: Why VSG Leads
With global grids facing declining inertia due to renewables, VSG emerges as the cornerstone technology:
Multi-Energy Synergy: Integrates with hydrogen/compressed air storage for extended duration support.
Digital Twin & Edge Computing: Enables real-time adaptive control and rapid strategy validation.
Global Forecast: >80% of new grid-scale storage will support VSG by 2027 (Wood Mackenzie).
Conclusion
Choosing between PQ, VF, and VSG hinges on your project’s needs:
PQ maximizes ROI in grid-tied systems.
VF ensures off-grid reliability.
VSG future-proofs high-renewable networks with synthetic inertia.
As grids evolve, VSG’s ability to bridge conventional and renewable power cements its role in the energy transition.
