1. INSTITUTE OF POWER ENGINEERING GDAŃSK DIVISION b.sobczak@ien.gda.pl Some Results of the Study „ Integration Possibilities of Wind Energy with the Polish Power Grid ” Carried Out by IPE for PPGC in 2002-2003

2. 2  Study has originated from strong interest in wind energy which has been observed in Poland although working wind installations are still below 100 MW  Wind energy developers have made applications for about 5000 MW total and due to law regulating grid connection, PPGC and distribution utilities are obliged to take position to each connection request without checking financial credibility of the applying customer  The study has had technical, economical and legal objectives. Only the technical ones will be included in this presentation. Economical and legal conditions are under continuous changes and the results of the study to some extent have lost their validity.

3. 3 Technical Goals of the Study  Assessment of maximum wind generation which could be absorbed by the Polish power system without substantial grid investments  Indication of wind investments enabling high wind penetration  Investigation of operational problems in the Polish power system resulting from high wind penetration  Proposals of technical requirements for wind farms connected to HV and EHV grids

4. 4 Input Data and Evaluation Criteria  The results of this kind of system study depend on input data and applied criteria  Model (location, power, type of WT) was established based on information obtained from the distribution utilities. Thanks to weather conditions and siting availability the north-western Poland along Baltic shore seems to be area of probable wind energy development  Other results of data collection: most of wind power will concentrate in large farms connected to HV and EHV grids, use of modern WT with DFIG will dominate

5. 5 Input Data and Evaluation Criteria Geographical distribution of wind farms Distribution of WF size „Planned” and „considered” WFs

6. 6 Input Data and Evaluation Criteria  Powerflow data elaborated for 2005 and 2010 for light and peak load conditions were used. Two models of WG were used („R” based on received data and „F” fictitious one where WG was connected to HV/EHV stations  The basic criterion for integration capability was occurrence of overload in the grid  The n-1 criterion was not applied as a strict rule. This responds to the situation where wind generation is treated as a „non-firm” generation which may be reduced or lost in „n-1” conditions at specific contingencies by applying so called remedial action schemes (RAS)  Criteria given in the Polish grid codes were used in other operational aspects for instance voltages profiles

7. 7 Maximum Wind Capacity Due to Thermal Ratings

8. 8 Operational Aspects Associated with High Wind Penetration Operational aspects were investigated on the „R” model of 4000 MW of WG. The following issues were considered:  Capacity reserves of regulating power  Control of line loadings  Regulation of voltage and reactive power  System automatics  Short Circuit power  Dynamic and transient stability

9. 9 Operational Reserves of Regulating Power  It was found that in the Polish power system being a part of UCTE unexpected wind gradients would not be the main problem  Due to the specifics of the north-western grid more serious will result from lost of WG after fault in the EHV grid. Up to 60% of WG can be lost due to fault on some EHV grid locations.  There is a strong need for appropriate regulations (setting of undervoltage protections and „ride through fault” capability for large WFs)

10. 10 Control of Line Loads  At present intact conditions loadings of transmission grid in the north-western Poland do not exceed 50%. 4000 MW of WG can increase loading of some elements to 90% and during contingencies many overloads was observed.  Wind generation cannot be treated as a firm generation from economical reasons. Its average productivity is around 25% and additional transfer capabilities will be exploited in small degree  HVDC link and pump storage hydro stations located in the north have some potential for avoiding overloads  It was observed that connection with Germany tend to be often overloaded (?)  RAS can be very efficient way to master the problem

11. 11 Regulation of Voltage and Reactive Power  Usually cos  =1 is required from WT. At high wind penetration this result with MVAr shortage. At low production problem with too high voltages in transmission grid can be observed (when local load is balanced by local generation)  Some range of Q generation/consumption in WG connection points is then required. 0.975 ind/cap range demanded by E.ON was used in powerflow calculations and ensured satisfactory voltage profiles. It is more than a standard DFIG WT can provide.

12. 12 System Automatics  VAR and voltage control installed in EHV/HV stations should involve large WFs with Q,U control capabilities, which are directly connected with the stations. This solution is better than installing compensating batteries  Grid operators assisted by automatics should initiate RAS to avoid overloadings. The automatics can also be installed in EHV/HV stations.  Algorithms of out-of-step protection automatics (APKO) which preserve global dynamic stability of the northern grid must be revised when large WF will have to be connected  TSO uses EMS. Evolution of EMS toward on-line calculation capabilities encompassing various operational aspects of grid operation is desired. It would allow safer integration of large WG with the Polish grid.

13. 13 System Dynamics  Experience of countries with large wind penetrations shows that WG concentrated in MV and HV is not critical for dynamic transient and small signal stability. Nevertheless some deterioration of low frequency oscillation damping was reported  Main danger for dynamics results from eventually lost WG during EHV faults  Other danger is connected with lowering of system inertia

14. 14 System Dynamics

15. 15 Technical Requirements for Wind Farm Connection  Proposals of such requirements taking into account already issued E.ON and ELTRA regulations and some other TSOs drafts as well as specifics of the Polish Power Grid were elaborated  Compatibility with other regulations  Due to the specifics of the Polish grid and probable model of wind energy development limitations can occur at rather low wind penetration  Importance of problem of Q,V regulation and staying grid connected during faults  Possibility of WFs active power control

16. 16 Some Conclusions  IPE performs many so called „WF connection expertizes”. Nowadays over 4000 MW of WG is considered in detailed powerflow calculations. Obtained results are compatible with results of the presented study  Level of WG present in government plans (< =2000 MW) can be reached without major investment in the grid but connected WFs must have some Q, V and active power regulations possibility  We see strong need for publishing WF connection requirements by the Polish TSO.  It would be desired to find out the Polish TSO attitude toward using RAS in case of WFs  Many planned WFs have valid rights to be connected to the grid. Low quantity of working wind installations result mainly from economical reasons (Euro/Zl rate) and other than grid connection regulations