Modern Digital Controllers Provide Additional Features to Improve Hydro Generators' Reliability


Modern digital automatic voltage regulators (AVR) provide many more features than analog AVRs or early vintage digital AVRs. This paper discusses several of these features in detail and the benefit of these features in today’s hydro power station generation system. In modern digital AVR systems, it is common to have multiple modes of operation including automatic voltage regulation, manual regulation, var control, and power factor control. One of the most important considerations with an AVR system is that it is tuned properly so the hydro electricity generator can properly react to transient conditions with the ability to rapidly return to steady state voltage with little to no oscillation. Also, this paper will explore details of Basler's auto tuning feature that is integrated in several digital AVR’s. 


Hydro power station/
DECS-250E Digital Excitation Control System/
SGC-250N Synchronous Generator Controller/
DECS-2100 Static Excitation System/

It is common for a hydro generator to have excitation limiters integrated in the digital AVR. These include overexcitation limiters, underexcitation limiters, V/HZ or underfrequency limiters, and stator current limiters. This paper discusses all of these features of newer digital regulators and their use within a hydro power station.

The integrated power system stabilizer (PSS) utilizes the integral of accelerating power. Further discussion is made regarding when it should be applied in a hydro application. The focus is on the available software tools that allow the power station to commission a Digital AVR system and the PPS more easily and accurately. Other topics discussed are protection, data log and trending, synchronizing/voltage matching, permissive for synchronizing (sync check), and redundancy. Programmable logic and how it is used to program the logic for protection schemes, inputs, outputs, and alarms is also discussed. The modern digital AVR is much more than previous AVRs. It is a digital excitation control system equipped with numerous tools that save time and money.

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