Introduction - Control of Power Inverters in Renewable Energy and Smart Grid Integration - page 55

according to utility regulations, e.g. on power quality control, reactive power control, fault
ride-through etc. (Kjaer et al . 2005). If a DC/DC converter is introduced, then the MPPT
function is often embedded into the controller of the DC/DC converter.

1.6 Smart Grid Integration
1.6.1 Operation Paradigms of Power Systems
1.6.1.1 Centralised Generation
Electrical power systems have been in existence all over the world for more than 100 years. A
typical power system, as shown in Figure 1.46, consists of facilities to generate, transmit and
distribute electrical power to consumers or loads (Karady and Holbert 2004) because power
plants, which generate electricity from energy sources such as fossil fuels, hydro, nuclear,
etc, are far from consumers. Although there are often interconnections at the transmission
level to form a strong grid, to which massive power plants are connected, electricity normally
flows uni-directionally from generation to loads. In particular, the electricity flows through the
distribution network is unidirectional.

1.6.1.2 Distributed Generation

For economic, technical and environmental reasons, there is today a trend towards the use of
small power generating units connected to the low-voltage distribution systems in addition to
the traditional large generators connected to the high-voltage transmission systems (Jenkins

Generation

Power Plant

500 kV Transmission

Extra-High-Voltage Substation
(500/230 kV)

230 kV
Transmission

Commercial/
Industrial
Customer

Transmission
System

Distribution Substation
(69/12 kV)

69 kV Sub-transmission

Urban
Customers

Distribution
System
(12 kV)

High-Voltage Substation
(230/69 kV)

Distribution Line

Overhead
Distribution
Transformer

Underground Cable

To Ot he r
High-Voltage
Substations

Residential
Customer

Residential
Customer

Underground
Distribution Transfomer

Figure 1.46 Overview of a current electrical power system. Source: Karady G and Holbert K,
2004. Electrical Energy Conversion and Transport: An Interactive Computer-Based Approach , C

John

Wiley & Sons