Desynchronized Synchronous Turbogenerators:

1. Desynchronized Synchronous Turbogenerators: Could They Benefit The New England Electric Power System? Boris Shapiro, MA DTE Presented to ISO-NE RC Members October 5, 2004

2. Transmission System Challenges • Increased power flows caused by more transactions between the regions. • Frequent and substantial fluctuations of demand for both active and reactive power. • Light load conditions are more often than ever before. • The higher the voltage rating of a transmission line – the more demanding the system for fast and smooth response to disturbances. • Local requirements for an underground cable may increase charging capacitance of the transmission upgrade. Potential for a low harmonic resonant effect.

3. How Is the High Voltage Problem Mitigated? • Fixed and variable shunt reactors • STATCOMs • Overhead lines and underground cables types with lower charging capacitance • HVDC • Generators? Yes, but… Inherently unstable under leading VAR operation with load angles more than 90o. The leading VAR range can be slightly extended with an advanced automatic voltage controller (AVC)

4. Range of Admissible Operating Modes of a Synchronous Turbogenerator • 1 – rated normal capacity • 2 – rotor current limitation • 3 – stability limitation (minimum excitation limit)

5. Range of Admissible Operating Modes of a DS-Turbogenerator • 1 – rated normal capacity • 2 – rotor current limitation • 3 – stator current limitation • 4 – rotor current limitation when operating with one field winding • 5 – stability limitation when operating with one field winding • 6 – asynchronous characteristic with short-circuited field windings

6. Structure of a DS-Turbogenerator Auxiliary Excitation System Transformer GSU Reversing Thyristor Exciter (d) q d+ d- d Thyristor Control System (d) Thyristor Control System (q) q+ Ufd Ufq q- Reversing Thyristor Exciter (q)

7. Rotor of a DS-Turbogenerator Four slip rings could be seen on the rotor end

8. Automatic Controls of a DS-Turbogenerator Controls of the Electromagnetic Moment and Reactive Power are Unbundled Where: Me is electromagnetic moment Q is reactive power U is stator voltage Ifx, Ify, Ufx, Ufy are excitation currents and voltages in the synchronous coordinate system Uf(q, d) is excitation voltage in the rotor windings “q” and “d” X, Xaf – stator winding impedance and mutual impedance δ is the rotor angle in the synchronous coordinate system

9. Vector Diagram of a DS-Turbogenerator Transition from point 1 to point 2 occurs without a change of the rotor angle position q E01 x 1 2 E02 -I2(r+jx) Ifq1 Ifx1 I2 If1 -I1(r+jx) y Ify U Ifd2 I1 Ifd1 d Ifq2 Ifx2 If2

10. Ranges of Dynamic Stability DS-Turbogenerator’s advantage over a synchronous generator escalates in the leading VAR operation DS-Turbogenerator Synchronous Turbogenerator

11. Characteristics of Desynchronized Generators • No steady state stability limitations in a broad range of operation including leading VAR range. • Most effective where excessive reactive power often exist. Allow avoiding costly installations of shunt reactors and other static devices. • Dynamic stability is equally high under both lagging and leading VAR operations. • Fast response to system disturbances and load fluctuation with no inertia and ability to support stable operation of synchronous generators in parallel operation. • In contrast to the synchronous generators, the DSTG voltage control is a pure electromagnetic process. • Control voltage smoothly. Typical static electronic devices control voltage in discrete steps. • Reliable, versatile, can continue operation with certain limitations under various abnormal and accidental conditions. Allow to reduce system reserved capacity. • Capital costs are in the same ballpark as of synchronous generators.

12. DS-Turbogenerators’ Implementation Status Worldwide • Two generators 200 MW each, manufactured by Electrotyazhmash (Ukraine). Re-powered Units 10 and 9 at Burshtinskaya Power Plant in Lvivenergo energy system, started commercial operation in 1985 and 1991, respectively. • A generator 110 MW manufactured by Electrosila* (Russia). Re-powered Unit 8 at Moscow Cogeneration (Heat and Power) Facility No.22, Mosenergo energy system, in December 2003. • Parsons (United Kingdom) started construction of a 500 MW generator in the 1970s. A 5 MW prototype was built and tested, and then the project was suspended indefinitely due to the technical difficulties. • Electrosila has developed a production line of the DS-Turbogenerators: - water-cooled generators T3VA type with normal capacity from 110 MW to 350 MW - air-cooled generators T3FA type 110 MW. * Electrosila is a member of Power Machines conglomerate and is partly owned by Siemens Corp. It has completed many recent projects according to the GE specifications

13. Impediments for the DS-Turbogenerators Design and Implementation • Two major parts of the design task: (a) construction of the electrical machine itself (“the hardware”); (b) composition of the AVC and determination of the control math algorithm (“the brains”). Part (b) was the most science-intensive task that required a lot of research effort. Mission accomplished. • Imperfections in the market rules and lack of the market incentives. Need to be resolved.

14. Lack of Market Incentives • NOATT Schedule 2: $1.05 per KVAR/year lagging VAR capability • No tariff for leading reactive support • No multi-point reactive support capability testing until 2008

15. Actions • Update the GE model to simulate the system operation equipped with the DS generator(s). • Review the tariff and address compensation for the leading VAR support capability. • Expedite implementation of the multi-point reactive capability test. • Implement a market-based pricing for reactive power support; mitigate the market power if it exists.

16. Questions?