Foreword ...................................................... xi
Preface ...................................................... xiii
Acknowledgements ............................................... xv
1. Energy and Electricity .................................... 1
1.1. The World Energy Scene .............................. 1
1.1.1. History ..................................... 1
1.1.2. World energy consumption .................... 1
1.1.3. Finite resources ............................ 2
1.1.4. Energy security and disparity of use ........ 3
1.2. The Environmental Impact of Energy Use .............. 3
1.2.1. The problem ................................. 3
1.2.2. The science ................................. 5
1.2.3. The Kyoto protocol .......................... 6
1.2.4. The Stern Report ............................ 7
1.2.5. Efficient energy use ........................ 8
1.2.6. The electricity sector ...................... 1
1.2.7. Possible solutions and sustainability ...... 11
1.3. Generating Electricity ............................. 11
1.3.1. Conversion from other energy forms - the
importance of efficiency ................... 11
1.3.2. The nuclear path ........................... 12
1.3.3. Carbon capture and storage ................. 13
1.3.4. Renewables ................................. 13
1.4. The Electrical Power System ........................ 16
1.4.1. Structure of the electrical power system ... 16
1.4.2. Integrating renewables into power
systems .................................... 18
1.4.3. Distributed generation ..................... 19
1.4.4. RE penetration ............................. 19
References ......................................... 20
2. Features of Conventional and Renewable Generation ........ 21
2.1. Introduction ....................................... 21
2.2. Conventional Sources: Coal, Gas and Nuclear ........ 22
2.3. Hydroelectric Power ................................ 23
2.3.1. Large hydro ................................ 24
2.3.2. Small hydro ................................ 25
2.4. Wind Power ......................................... 27
2.4.1. The resource ............................... 27
2.4.2. Wind variability ........................... 28
2.4.3. Wind turbines .............................. 30
2.4.4. Power variability .......................... 33
2.5. PV and Solar Thermal Electricity ................... 36
2.5.1. The resource ............................... 36
2.5.2. The technology ............................. 37
2.5.3. Photovoltaic systems ....................... 38
2.5.4. Solar thermal electric systems ............. 40
2.6. Tidal Power ........................................ 42
2.6.1. The resource ............................... 42
2.6.2. Tidal enhancement .......................... 43
2.6.3. Tidal barrages ............................. 43
2.6.4. Operational strategies ..................... 44
2.6.5. Tidal current schemes ...................... 45
2.7. Wave Power ......................................... 47
2.7.1. The resource ............................... 47
2.7.2. The technology ............................. 48
2.7.3. Variability ................................ 49
2.8. Biomass ............................................ 50
2.8.1. The resource ............................... 50
2.8.2. Resource sustainability .................... 51
2.9. Summary of Power Generation Characteristics ........ 52
2.10. Combining Sources .................................. 53
References ......................................... 53
3. Power Balance/ Frequency Control ......................... 55
3.1. Introduction ....................................... 55
3.1.1. The power balance issue .................... 55
3.2. Electricity Demand ................................. 56
3.2.1. Demand curves .............................. 56
3.2.2. Aggregation ................................ 57
3.2.3. Demand-side management - deferrable
loads ...................................... 58
3.3. Power Governing .................................... 59
3.3.1. Power conversion chain ..................... 59
3.3.2. The governor ............................... 60
3.3.3. Parallel operation of two generators ....... 61
3.3.4. Multigenerator system ...................... 62
3.3.5. The steady state power-frequency
relationship ............................... 63
3.4. Dynamic Frequency Control of Large Systems ......... 64
3.4.1. Demand matching ............................ 64
3.4.2. Demand forecasting ......................... 65
3.4.3. Frequency limits ........................... 67
3.4.4. Generation scheduling and reserve .......... 68
3.4.5. Frequency control at different
timescales ................................. 68
3.4.6. Meeting demand and ensuring reliability .... 70
3.4.7. Capacity factor and capacity credit ........ 71
3.5. Impact of Renewable Generation on Frequency
Control and Reliability ............................ 72
3.5.1. Introduction ............................... 72
3.5.2. Aggregation of sources ..................... 73
3.5.3. Value of energy from the wind .............. 76
3.5.4. Impact on balancing ........................ 76
3.5.5. Impact on reliability ...................... 79
3.5.6. Discarded/curtailed energy ................. 79
3.5.7. Overall penalties due to increasing
penetration ................................ 80
3.5.8. Combining different renewable sources ...... 81
3.5.9. Differences between electricity systems .... 81
3.5.10. Limits of penetration from
nondispatchable sources .................... 81
3.6. Frequency Response Services from Renewables ........ 84
3.6.1. Wind power ................................. 84
3.6.2. Biofuels ................................... 85
3.6.3. Water power ................................ 86
3.6.4. Photovoltaics .............................. 86
3.7. Frequency Control Modelling ........................ 86
3.7.1. Background ................................. 86
3.7.2. A modelling example ........................ 89
3.8. Energy Storage ..................................... 91
3.8.1. Introduction ............................... 91
3.8.2. Storage devices ............................ 91
3.8.3. Dynamic demand control ..................... 93
References ......................................... 94
Other Useful Reading ............................... 95
4. Electrical Power Generation and Conditioning ............. 97
4.1. The Conversion of Renewable Energy into
Electrical Form .................................... 97
4.2. The Synchronous Generator .......................... 98
4.2.1. Construction and mode of operation ......... 98
4.2.2. The rotating magnetic field ............... 101
4.2.3. Synchronous generator operation when
grid-connected ............................ 103
4.2.4. The synchronous generator equivalent
circuit ................................... 104
4.2.5. Power transfer equations .................. 105
4.2.6. Three-phase equations ..................... 106
4.2.7. Four-quadrant operation ................... 107
4.2.8. Power-load angle characteristic:
stability ................................. 108
4.3. The Transformer ................................... 108
4.3.1. Transformer basics ........................ 108
4.3.2. The transformer equivalent circuit ........ 110
4.3.3. Further details on transformers ........... 111
4.4. The Asynchronous Generator ........................ 112
4.4.1. Construction and properties ............... 112
4.4.2. The induction machine equivalent
circuit ................................... 114
4.4.3. The induction machine efficiency .......... 116
4.4.4. The induction machine speed-torque
characteristic ............................ 117
4.4.5. Induction generator reactive power ........ 120
4.4.6. Comparison between synchronous and
asynchronous generators ................... 121
4.5. Power Electronics ................................. 121
4.5.1. Introduction .............................. 121
4.5.2. Power semiconductor devices ............... 122
4.5.3. Diode bridge rectifier .................... 124
4.5.4. Harmonics ................................. 126
4.5.5. The thyristor bridge converter ............ 126
4.5.6. The transistor bridge ..................... 128
4.5.7. Converter internal control systems ........ 133
4.5.8. DC-DC converters .......................... 133
4.6. Applications to Renewable Energy Generators ....... 134
4.6.1. Applications to PV systems ................ 134
4.6.2. Applications to wind power ................ 137
References ........................................ 147
5. Power System Analysis ................................... 149
5.1. Introduction ...................................... 149
5.2. The Transmission System ........................... 149
5.2.1. Single-phase representation ............... 151
5.2.2. Transmission and distribution systems ..... 152
5.2.3. Example networks .......................... 153
5.3. Voltage Control ................................... 153
5.4. Power Flow in an Individual Section of Line ....... 156
5.4.1. Electrical characteristics of lines and
cables .................................... 156
5.4.2. Single-phase equivalent circuit ........... 156
5.4.3. Voltage drop calculation .................. 157
5.4.4. Simplifications and conclusions ........... 158
5.5. Reactive Power Management ......................... 160
5.5.1. Reactive power compensation equipment ..... 160
5.6. Load Flow and Power System Simulation ............. 163
5.6.1. Uses of load flow ......................... 163
5.6.2. A particular case ......................... 164
5.6.3. Network data .............................. 165
5.6.4. Load/generation data ...................... 165
5.6.5. The load flow calculations ................ 167
5.6.6. Results ................................... 168
5.6.7. Unbalanced load flow ...................... 168
5.7. Faults and Protection ............................. 169
5.7.1. Short-circuit fault currents .............. 169
5.7.2. Symmetrical three-phase fault current ..... 170
5.7.3. Fault currents in general ................. 170
5.7.4. Fault level (short-circuit level) -
weak grids ................................ 171
5.7.5. Thevenin equivalent circuit ............... 171
5.8. Time Varying and Dynamic Simulations .............. 172
5.9. Reliability Analysis .............................. 173
References ........................................ 173
6. Renewable Energy Generation in Power Systems ............ 175
6.1. Distributed Generation ............................ 175
6.1.1. Introduction .............................. 175
6.1.2. Point of common coupling (PCC) ............ 176
6.1.3. Connection voltage ........................ 176
6.2. Voltage Effects ................................... 177
6.2.1. Steady state voltage rise ................. 177
6.2.2. Automatic voltage control - tap
changers .................................. 178
6.2.3. Active and reactive power from renewable
energy generators ......................... 179
6.2.4. Example load flow ......................... 180
6.3. Thermal Limits .................................... 183
6.3.1. Overhead lines and cables ................. 183
6.3.2. Transformers .............................. 184
6.4. Other Embedded Generation Issues .................. 184
6.4.1. Flicker, voltage steps and dips ........... 184
6.4.2. Harmonics/distortion ...................... 185
6.4.3. Phase voltage imbalance ................... 186
6.4.4. Power quality ............................. 186
6.4.5. Network reinforcement ..................... 187
6.4.6. Network losses ............................ 187
6.4.7. Fault level increase ...................... 187
6.5. Islanding ......................................... 188
6.5.1. Introduction .............................. 188
6.5.2. Loss-of-mains protection for rotating
machines .................................. 189
6.5.3. Loss-of-mains protection for inverters .... 190
6.6. Fault Ride-through ................................ 190
6.7. Generator and Converter Characteristics ........... 192
References ........................................ 193
7. Power System Economics and the Electricity Market ....... 195
7.1. Introduction ...................................... 195
7.2. The Costs of Electricity Generation ............... 195
7.2.1. Capital and running costs of renewable
and conventional generation plant ......... 195
7.2.2. Total generation costs .................... 197
7.3. Economic Optimization in Power Systems ............ 198
7.3.1. Variety of generators in a power system ... 198
7.3.2. Optimum economic dispatch ................. 200
7.3.3. Equal incremental cost dispatch ........... 201
7.3.4. OED with several units and generation
limits .................................... 203
7.3.5. Costs on a level playing field ............ 204
7.4. External Costs .................................... 205
7.4.1. Introduction .............................. 205
7.4.2. Types of external cost .................... 205
7.4.3. The Kyoto Agreements ...................... 206
7.4.4. Costing pollution ......................... 207
7.4.5. Pricing pollution ......................... 208
7.5. Effects of Embedded Generation .................... 209
7.5.1. Value of energy at various points of
the network ............................... 209
7.5.2. A cash-flow analysis ...................... 210
7.5.3. Value of embedded generation - regional
and local issues .......................... 212
7.5.4. Capacity credit ........................... 213
7.5.5. Summary ................................... 215
7.6. Support Mechanisms for Renewable Energy ........... 215
7.6.1. Introduction .............................. 215
7.6.2. Feed-in law ............................... 216
7.6.3. Quota system .............................. 217
7.6.4. Carbon tax ................................ 217
7.7. Electricity Trading ............................... 218
7.7.1. Introduction .............................. 218
7.7.2. The UK electricity supply industry
(ESI) ..................................... 218
7.7.3. Competitive wholesale markets in other
countries ................................. 223
7.7.4. The value of renewable energy in a
competitive wholesale market .............. 226
References ........................................ 229
8. The Future - Towards a Sustainable Electricity Supply
System .................................................. 231
8.1. Introduction ...................................... 231
8.2. The Future of Wind Power .......................... 232
8.2.1. Large wind turbines ....................... 232
8.2.2. Offshore wind farm development ............ 233
8.2.3. Building integrated wind turbines ......... 238
8.3. The Future of Solar Power ......................... 240
8.3.1. PV technology development ................. 240
8.3.2. Solar thermal electric systems ............ 241
8.4. The Future of Biofuels ............................ 242
8.5. The Future of Hydro and Marine Power .............. 243
8.6. Distributed Generation and the Shape of Future
Networks .......................................... 244
8.6.1. Distribution network evolution ............ 244
8.6.2. Active networks ........................... 245
8.6.3. Problems associated with distributed
generation ................................ 246
8.6.4. Options to resolve technical
difficulties .............................. 246
8.7. Conclusions ....................................... 249
References ........................................ 250
Appendix: Basic Electric Power Engineering Concepts ........... 253
A.l. Introduction ............................................ 253
A.2. Generators and Consumers of Energy ...................... 253
A.3. Why AC? ................................................. 255
A.4. AC Waveforms ............................................ 255
A.5. Response of Circuit Components to AC .................... 256
A.5.1. Resistance ...................................... 257
A.5.2. Inductance ...................................... 258
A.5.3. Capacitance ..................................... 259
A.6. Phasors ................................................. 260
A.7. Phasor Addition ......................................... 261
A.8. Rectangular Notation .................................... 263
A.9. Reactance and Impedance ................................. 265
A.9.1. Resistance ...................................... 265
A.9.2. Inductance ...................................... 265
A.9.3. Capacitance ..................................... 266
A.9.4. Impedance ....................................... 266
A.10. Power in AC Circuits .................................... 267
A.11. Reactive Power .......................................... 269
A.12. Complex Power ........................................... 269
A.13. Conservation of Active and Reactive Power ............... 271
A.14. Effects of Reactive Power Flow - Power Factor
Correction .............................................. 272
A.15. Three-phase AC .......................................... 273
A.16. The Thevenin Equivalent Circuit ......................... 275
Reference ............................................... 276
Index ......................................................... 277
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