gridsynchronization

Grid synchronization, sometimes written gridsynchronization, is the process of bringing a device, power source, or control system into electrical parity with a larger power grid before electrical connection. The key goal is to match voltage magnitude, system frequency, and phase angle so that connecting to the grid does not cause circulating currents, excessive transient loads, or stability problems.

For conventional synchronous generators, synchronization occurs at the point of common coupling by aligning their output with the grid and closing the circuit breaker when the voltage, frequency, and phase align within acceptable limits. In modern systems, grid synchronization is often performed automatically using phase-locked loop (PLL) based control in inverters and synchronization relays. Devices commonly use a synchroscope or indicator to visualize phase, and inverter controls manage the transition from islanded to grid-following operation with minimal disturbance.

Typical criteria include voltage magnitude within a specified tolerance (often a few percent), grid frequency within a tolerance (for example, ±0.1–0.5 Hz depending on region), and a small phase-angle difference enabling safe paralleling. The switching must be performed with controlled rates to limit inrush currents and harmonics. In microgrids, seamless islanding and re-synchronization are also considered to maintain reliability when switching between islanded and grid-connected modes.

Grid synchronization is central to grid interconnections, renewable energy integration, and power quality. It involves standards and codes such as IEEE 1547 and IEC 61727 that define requirements for safe and reliable connection, anti-islanding, fault ride-through, and voltage/frequency support. Failures in synchronization can cause equipment damage, instability, and protection tripping.