Wide area synchronous grid

[1] Neighbouring interconnections with the same frequency and standards can be synchronized and directly connected to form a larger interconnection, or they may share power without synchronization via high-voltage direct current power transmission lines (DC ties), solid-state transformers or variable-frequency transformers (VFTs), which permit a controlled flow of energy while also functionally isolating the independent AC frequencies of each side.

As was discovered in the 2000–2001 California electricity crisis, there can be strong incentives among some market traders to create deliberate congestion and poor management of generation capacity on an interconnection network to inflate prices.

Increasing transmission capacity and expanding the market by uniting with neighbouring synchronous networks make such manipulations more difficult.

For rotating generators, a local governor regulates the driving torque and helps maintain a more or less constant speed as loading changes.

When the grid is heavily loaded, the frequency slows, and governors adjust their generators so that more power is output (droop speed control).

In addition, there's often central control, which can change the parameters of the AGC systems over timescales of a minute or longer to further adjust the regional network flows and the operating frequency of the grid.

Many traditional generator systems had wires which could be overloaded for very short periods without damage, but inverters are not as able to deliver multiple times their rated load.

The short circuit ratio can be calculated for each point on the grid, and if it is found to be too low, for steps to be taken to increase it to be above 1, which is considered stable.

In 2018 Kosovo used more power than it generated due to a row with Serbia, leading to the phase in the whole synchronous grid of Continental Europe lagging behind what it should have been.