Let This Sync In
Jason Doering, P.Eng
Grid & Physics Advocate - physics trumps rhetoric every time
ERCOT recently published a report that identified the installation of synchronous condensers at six locations on the Texas power system to address operational and reliability challenges associated with the large volumes of wind and solar generation on their system. This is an excellent example of the evolving nature of power system planning and operations so I think it's worth some discussion.
Degrading Power System Characteristics
ERCOT has seen a significant increase in inverter-based resources (IBRs, wind and solar generation) connecting to the Texas power system in recent years, and they have reached a point where there are regions of the system that are dominated by IBRs with little to no synchronous generators. In these regions, the strength of the system has been weakened with decreased inertial response and reactive power support which is creating operational challenges that make it difficult to maintain reliable operations and manage system disturbances.
Texas is not alone in its challenges with large penetrations of IBRs. There have been 13 significant disturbance events associated with IBRs on the Western Interconnection (WECC) and ERCOT combined since 2016, the largest of which was the Odessa Disturbance in 2022. The graph below shows 12 of the disturbances and doesn't include the Southwest Utah Disturbance that happened in April 2023.
These large disturbances demonstrate the growing reliability risks associated with increasing volumes of IBRs and decreasing volumes of synchronous generators on power systems. FERC's recent Order No. 901 directing NERC to develop specific reliability standards for IBRs recognizes this current and growing threat to reliability.
Given the current challenges and the large number of IBRs planning to connect to the Texas power system in the near term, ERCOT has identified the installation of a number of synchronous condensers at specific locations on its system as a near-term action to help maintain reliable operations.
What's a Synchronous Condenser?
A synchronous condenser is essentially a conventional generator that is not coupled to a turbine to provide energy, but simply synchronized to the power system to freely spin at system frequency (60 Hz, 3600 RPM) to provide inertia, reactive power, and short circuit support. Synchronous condensers can also be fitted with flywheels to provide additional inertia beyond the inherent inertia provided by their rotating masses.
Synchronous condensers (aka synchronous compensators, synchronous capacitors, or syncs) are not new, and have been used on power systems since the 1920s to provide voltage control and inertia and many are in operation today. When I was a maintenance engineer at Manitoba Hydro in the early 2000s, I got to balance synchronous condensers at HVDC converter stations when they went back into service after maintenance. However, because power systems have historically been dominated by synchronous generators that provide inertia and voltage support, the use of additional synchronous condensers to provide reactive power support gradually gave way to more cost-effective technologies such as static VAR compensation or STATCOMs, which are based on power electronics that are faster acting and cheaper to operate and maintain than big spinning masses. As with many technologies, "analog" syncs gave way to "digital" STATCOMs.
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But with the proliferation of "digital" IBRs (wind, solar) driven by the energy transition, the good old "analog" physical operating characteristics of synchronous condensers can now help compensate for the decreasing number of synchronous generators on power systems to help system operators maintain reliable operations.
ERCOT describes the characteristics of synchronous condensers in their report as follows:
Synchronous condensers are not new to the Texas system. In 2018, two syncs were added in the panhandle region to provide voltage support and increase system strength.
ERCOT Recommendations
The ERCOT study makes the following synchronous condenser recommendations:
ERCOT states that adding new syncs at these specific locations on the Texas power system will "effectively bolster the reliability of the West Texas system, make the system more resilient to unexpected events, and address the challenges that may arise in real-time operations."
Concluding Thoughts
The increasing number of IBRs connecting to power systems around the world as part of the energy transition is creating new reliability and operability challenges for power system operators who have historically relied on synchronous generators to help maintain system reliability. However, the revival of good old synchronous condenser technology can help, and we are seeing new syncs being installed on power systems in Texas, Ireland, Maine, and others. This is just one example of the kinds of adaptations system operators are making as our power systems continue to evolve. In the long term, power the power system evolution will require a combination of existing technologies, such as syncs, and new technologies we haven't even thought of yet. Suffice it to say, power system planners and operators are certainly living in interesting times :-)
Mechanical Maintenance Scheduler at TransAlta, Sheerness Generating Station
1 年As they become more necessary I wonder what new, unanticipated costs will result. Sounds like old base load units maintained frequency stability without these costs.
Principal Engineer at APH Consulting Inc
1 年sounds logical to me, I was in TX in 2021 when the cold front moved in, many people died, these would have been God SEND, had some of them been in place. We need to ensure that idiotic Trudeau & Guilbeault will never force their unscientific ideology to impact our Electrical Grid System here in AB
Information Broker for the electrical industry
1 年Synchronous condensers, motor Gen sets with fly wheels, I wonder what’s gonna come back next? Vacuum tubes!? To quote Doc Brown from back to the future, “Great Scott!” (No doubt a salutation to Commander Montgomery Scott, future patron saint of power engineering, LOL)
An Engineer who strives to provide clients with Value Added solutions.
1 年I agree that wind turbines have inverters so synch condensers are needed to stabilize the grid. They also provide inertia and short circuit capacity to the grid for stability. I don’t know fully why sync condensers went out of style. I know we are always drawn towards trendy tech but condensers are reliable. I am not fully a transmission guy but have a well rounded knowledge of electrical and power grids so that is my disclaimer.