Stability in power system

[smruti]

Now a days in most of the power systems(generation,transmission (HVDC, HVAC) and distribution) we use semiconductor devices for efficient use of power.using power electronic components in power systems does it affect the stability(transient/steady state)?

 

[anorlunda]

Now a days in most of the power systems(generation,transmission (HVDC, HVAC) and distribution) we use semiconductor devices for efficient use of power.using power electronic components in power systems does it affect the stability(transient/steady state)?

Sure. In many cases, power electronics are added by the utilities to specifically improve stability, directly or indirectly. They wouldn't do that if they didn't work.

But your question is a bit unclear. You might be asking whether power electronics used broadly for many purposes may inadvertenly have an adverse effect on stability. Yes they could. But part of the responsibility of system planners is to include such effects in their simulations used to analyze grid performance. If they see adverse effects, they tweak things to mitigate. For example, I heard of utility studies that looked at the question of whether widespread adoption of LED lighting would have an adverse effect on the grid. Such questions are the everyday bread and butter of system planners.

But power electronics are not a panacea. In the near future, there is no chance of seeing a "smart" grid where an electronically controlled device replaces every segment of a "dumb" wire. They are very expensive, especially when used to throttle large quantities of power. I recall an installation at the Itaipu dam in Brazil/Paraguay in the 1970s that cost nearly $1 billion just for that one plant. Power electronics can also introduce substantial energy losses. Because of those factors, they are used only in niche applications where the benefits are large enough.

An example, could be an electronically controlled shunt VAR compensator, that helps to control voltage to aid stability. Controlling only the shunt reactive component is much less expensive than controlling the total load current passing through the lines.

 

[jim hardy]

Power system stability is fascinating. Real energy sloshes around the grid between rotating inertias and instability can manifest itself as oscillations in voltage, vars, or megawatts. Typical frequencies are a bit less than 1hz, I've seen 2/3 hz.

So electronic gizmos that lack a natural time constant in that range can be quite helpful or quite harmful, depending on the expertise of the fellow doing the installation.

I just learned that twenty megawatt battery-inverter combinations are commercially available right now.
A few dozen of those on a power system might provide short term frequency stability when a big steam unit suddenly trips.
You'd have to tune them so they don't start a fight with nearby steam plant governors, though.
And be doggone sure they can't do anything in the range of steam turbine shaft resonant frequency - maybe 5 to 10 hz.

old jim

 

[dlgoff]

Power system stability is fascinating.

And covers sooo many areas; SCADA and Protection just to name a couple.

I just learned that twenty megawatt battery-inverter combinations are commercially available right now.

Dang. Really?

welcome back BTW