How can variable speed control optimize hydroelectric power generation?
CZECHIA: In the Albrechtice and Orlicí municipality in Czechia, a small hydropower plant (SHP) has been supplying electricity to surrounding towns since before World War II. However, the plant was originally designed to produce energy at maximum efficiency for only about three months a year. When the 80-year-old gears began to fail, Danfoss proposed a retrofit solution that eliminated the need for gears and introduced variable speed drives to increase the plant’s efficiency with minimal adjustment to the existing installation. The new gearless solution includes a VACON® NXC low harmonic drive, a VACON® NXP Common DC Bus, and DrivePro® services. As a result, the plant now produces approximately 10% more energy than the previous setup.
Discover how SHP Albrechtice improved the efficiency of their operations with a retrofit solution and DrivePro® services.
The challenge: Ensuring year-round efficiency despite changing demands
High efficiency, performance, and longevity are key for any hydropower plant to operate reliably while reducing maintenance costs. However, with one 150 kW and two 250 kW Francis turbines with MV synchronous generators synchronized to the grid and running at a fixed speed, the 80 year-old SHP Albrechtice installation was designed to operate at optimal efficiency only during the three months of the year when water levels were most consistent.
When SHP Albrechtice saw the gears in the old generators begin to fail, they reached out to Danfoss and Q-ELEKTRIK for a new solution. Danfoss identified an opportunity to improve efficiency in the old installation by retrofitting the system with drives and a synchronous generator with permanent magnets, rather than simply replacing the worn gears with new ones.
The old gears had been working well for 80 years, but technology has obviously advanced quite a bit since then. We saw a chance to enhance efficiency by introducing variable speed drives. However, we wanted to avoid making the project more extensive than necessary, so we proposed a retrofit solution instead of a full replacement
The solution: Adapting to the changing flow with variable speed drives
The system proposed by Danfoss included a 250 kW TES VSETIN GSP1120S60 synchronous generator with permanent magnets, a 250 kW Danfoss VACON® NXC Low Harmonic drive with regenerative capabilities, and a brake chopper unit from the VACON® NXP Common DC Bus products.
One of the standout features was the robust design of the compact VACON® NXC drive, which adjusts the frequency and voltage of the power supplied to the motor/generator. This allows the turbine to run at variable speeds, adapting to changes in water flow and maintaining optimal performance under different conditions — always generating maximum power at any given time.
The drive, which includes an integrated filter for harmonic mitigation, was custom configured with an Active Front-end (AFE) inverter equipped with a voltage measurement board to support grid code compliance.
In addition to the two types of drives, SHP Albrechtice selected two DrivePro® lifecycle services to ensure a smooth implementation and minimize unplanned downtime. With DrivePro® Start-up, professional drive experts helped guarantee optimal performance from day one, reducing both installation and commissioning time and costs. DrivePro® Preventive Maintenance offers a tailored maintenance program, helping the plant enhance efficiency while mitigating the effects of wear and tear.
- The VACON® NXC enclosed drive performs reliably in harsh operating conditions
- VACON® NXC offers lower maintenance costs due to its robust, type-tested design
- Reduced energy costs with VACON® NXP as regenerative front end feeds excess braking energy back into the network
- The active front-end unit in VACON® NXP improves drive line-up tolerance to voltage dips/sags and minimized harmonic distortion
- DrivePro® services cover the full lifecycle of a Danfoss drive, maximizing performance, uptime, and lifespan with expert assistance and a predictable maintenance budget
Learn more about DrivePro® services
The outcome: Producing 10% more energy in the first year
After one year of operation, SHP Albrechtice’s expectations for a more efficient setup had already been met.
“With the ability to adjust the speed of the system based on real-time demand, we produced 10% more energy in the first year of running the new setup,” says Mr. Jiří Čáp, Owner, SHP Albrechtice.
In addition, the system, along with the two service agreements, has helped the plant reduce maintenance costs and minimize stoppages.
“Overall, our experience with Danfoss has been very positive, marked by a proactive approach, dedicated people, and clear communication,“ says Mr. Jiří Čáp.
Preparations began in 2021, with commissioning taking place at the end of 2022. The first DrivePro® Preventive Maintenance visit is scheduled, and an upgrade of the plant’s next generator is planned for 2025.
