"If you care about climate change, you should care about transmission" - Bill Gates

Uzbekistan’s ambitious plans to secure energy independence and provide its industries and population with sustainable and reliable access to modern, clean, and affordable energy are attainable. To ensure success, policymakers and the utility should invest in strengthening the nation’s power grid to be reliant and resilient against the challenges of renewable energy integration.  

In Uzbekistan, where nearly 95 percent of electricity is generated by thermal plants and more than 75 percent of power comes from natural gas, clean energy has become an increasingly important vector of the government’s strategy for economic development. Recently, the Government of Uzbekistan set ambitious renewable energy targets including 8,000 MW of renewable capacity by 2026. In addition, the Government of Uzbekistan is considering increasing solar capacity goals from 5,000 to 7,000 MW and wind capacity goals from 3,000 to 5,000 MW. If realized, this would achieve the goals of generating at least 30 percent of electricity from renewable energy sources with hydropower generation increasing up to 50 percent by 2030.   

Reducing Uzbekistan’s reliance on fossil fuels is a commendable development but transitioning to reliable clean energy requires more than financing, building, and commissioning new power plants. Grid integration of substantial amounts of renewable energy creates several challenges to the power system’s stability and reliability. Since renewable production is less predictable, and has less inertia than conventional generation, there is an increased potential for frequency and voltage issues and the temporary overloading of existing transmission lines. Integrating large volumes of renewable generation into a weak and inflexible grid may lead to a mismatch between energy supply and demand that might result in a blackout or even system collapse. To mitigate these risks, system operators must implement strict requirements for network flexibility and controllability, especially for active power regulation, and begin utilizing energy storage solutions that help offset the variability of renewable energy sources.

In Uzbekistan, where power outages are already frequent, particularly in winter months, grid instability is a critical concern. To address this issue, the United States Energy Association (USEA) conducted a study on stability and reliability of the planned state of the Uzbekistan power system in 2026 with 1,800 MW of wind power, 2,500 MW of solar, and 6,500 MW of new thermal and hydropower generation capacity added to the grid. The purpose of the study, funded by the U.S. Agency for International Development (USAID), was to analyze the future transmission system behavior and develop technical and engineering solutions to avoid network instability that might be caused by the planned integration of these large volumes of renewable generation. The study, carried out by the consulting firm DMCC Engineering, included analyses of steady state conditions for normal (N-0) and emergency (N-1) network schemes, and dynamic stability and small signal stability calculations. The results of the system study revealed several potential issues of grid instability, the overloading of lines and transformers, limited evacuation of power from certain power stations, and the possibility for inter-area oscillations between western Uzbekistan and the rest of the Central Asia power system that can lead to a total system collapse.   

Fortunately, there are technical and administrative solutions that the Government of Uzbekistan and the National Electric Grid of Uzbekistan (NEGU), the country’s transmission system operator (TSO), can implement to mitigate these potential issues and preserve the stability of the national power grid.    

Modernize the grid

System steady-state calculations results show that many network facilities in 2026 will be on the edge of overloading due to a significant growth in load demand and the integration of renewable energy sources (RES). This can be avoided by increasing the rated transfer capacity of the overloaded transmission lines and adding parallel transformers at overloaded substations. It is also recommended to implement Special Integrity Protection Schemes (SIPS) to control the output of power at certain Hydro Power Plants (HPPs).

In certain scenarios, the transient stability is either violated or very close to being violated. The loss of transient stability will lead to a serious limitation of a power plant’s ability to deliver power to the grid and, in the worst-case scenario, might result in a total system blackout. To prevent this, breaker failure protection settings should be revised to reduce short-circuit clearing times. NEGU should consider investing in more modern equipment, such as digital instrument transformer solutions enabling full IEC 61850 implementation, numerical relay protections, or Gas Insulated Switchgear. These types of devices can reduce short-circuit clearing time to be as low as 0.25-0.30 seconds and thereby eliminate transient stability issues. 

The transfer capacity of critical grid interfaces between western Uzbekistan and the rest of Central Asia should be increased to reduce the probability of poorly damped low-frequency oscillations, and to allow evacuation of full capacity operation of western power plants. There are many options to achieve this increase, including by increasing the capacity of the existing power lines connected to these interfaces, constructing new lines, and using modern technologies such as Flexible AC Transmission Systems (FACTS), Battery Energy Storage Systems (BESS), Embedded High Voltage Direct Current (HVDC) lines and others.

Revise grid operating procedures and system controls’ settings

Every second, a power system goes through many disturbances and structural changes due to forced and planned outages, optimization actions, operation of control equipment, switching operations, and dispatcher interventions. Introducing new generating facilities in the already constantly changing environment requires system operators to re-engineer many processes to control the grid, including re-tuning the controls at power plants, checking the logic and accuracy of protection systems and SIPSs settings, and many others.

In Uzbekistan, NEGU should review the settings and operational logic of the existing emergency automatic load shedding scheme, as well as breaker failure protection settings, to reduce the short-circuit clearing times and increase the transfer capacity of the most important grid interfaces.  

Improve asset inventory and conduct system studies

Accurate and reliable power system modeling and analyses are very important for operating a traditional grid, but they become crucial in power systems with large and increasing shares of renewable generation. NEGU should be diligent at maintaining, updating, and improving their grid model of the Uzbekistan power system. The crucial task at this moment is to collect the most current data on existing power plant generating units. Having accurate data significantly improves the accuracy of the current dynamic model of the Uzbekistan power grid and enhances the reliability of system studies. Accurate modeling of power plants will also improve results of dynamic stability calculations. Therefore, the software model of the Uzbekistan grid should be regularly checked for accuracy to be in line with the current network structure and conditions. 

NEGU should also conduct a power balance study with hourly time resolution, stochastic analysis, and market studies. Larger volumes of renewable generation in the Uzbekistan power system will require NEGU to manage RES variability with great precision, and stochastic studies, as the cutting-edge approach, will enable it to do so. 

Build in-house capacity

The last, but perhaps the most important recommendation is to build capacity within all Central Asia’s system operators, including NEGU. All Central Asian countries have committed to considerable renewable energy goals and emission reduction targets. However, without the in-house capacity to manage grids with a large penetration of renewables and to model power systems and conduct studies using modern tools and emerging methodologies, their efforts to achieve these goals might fail against the highly variable and unpredictable nature of renewable generation.

This article was drafted by Marina N. Barnett, Program Manager at the United States Energy Association, Washington, DC; Lukian N. Lukianenko, Deputy Project Manager and Vsevolod V. Pavlovsky, CEO and Principal Engineer, DMCC Engineering, Kyiv, Ukraine, within the framework of USEA and USAID’s Central Asia Partnership as part of the Energy Utility Partnership Program.

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Marina Barnett

Source: https://usea.org/article/renewables-and-grid-stability-uzbekistan-can-have-both

Press Service of JSC “National Electric Grid of Uzbekistan”