11-08-2012, 02:30 PM
Models for a Stand-Alone PV System
[attachment=31132]
Introduction
This report presents a number of models for modelling and simulation of a stand-alone photovoltaic (PV) system with a battery bank verified against a sys-tem installed at Risø National Laboratory. The work has been supported by the Danish Ministry of Energy, as a part of the activities in the Solar Energy Centre Denmark. The model of the stand-alone PV system is made up by blocks in or-der to facilitate the modelling of other structures of PV systems.
Many photovoltaic systems operate in a stand-alone mode. Such systems consist of a PV generator, energy storage (for example a battery), AC and DC consum-ers and elements for power conditioning – as sketched in Figure 1. Per defini-tion, a stand-alone system involves no interaction with a utility grid. A PV gen-erator can contain several arrays. Each array is composed of several modules, while each module is composed of several solar cells. The battery bank stores energy when the power supplied by the PV modules exceeds load demand and releases it backs when the PV supply is insufficient. The load for a stand-alone PV system can be of many types, both DC (television, lighting) and AC (elec-tric motors, heaters, etc.). The power conditioning system provides an interface between all the elements of the PV system, giving protection and control. The most frequently encountered elements of the power conditioning system are blocking diodes, charge regulators and DC-AC converters.
Measurement system
The measurement system is shown in Figure 3. The central unit in the meas-urement system is the Analog 6B ADC box. This box collects the analogue data from terminal boxes located in different places on the PV system and converts the signals to digital signals. The digital signals are transmitted on a serial con-nection to the data acquisition PC, where the data is logged on the harddisk.
Component models for stand-alone PV system
The main purpose of this section is to describe the models for the elements of a stand-alone PV system: PV generator, battery, controller, inverter and load. The modelling of the PV system is based on modular blocks, as illustrated in Figure 4. The modular structure facilitates the modelling of the other system structures and replacing of elements, for instance a DC load instead of an AC load.
Battery
An another important element of a stand-alone PV system is the battery. The battery is necessary in such a system because of the fluctuating nature of the output delivered by the PV arrays. Thus, during the hours of sunshine, the PV system is directly feeding the load, the excess electrical energy being stored in the battery. During the night, or during a period of low solar irradiation, energy is supplied to the load from the battery.
[attachment=31132]
Introduction
This report presents a number of models for modelling and simulation of a stand-alone photovoltaic (PV) system with a battery bank verified against a sys-tem installed at Risø National Laboratory. The work has been supported by the Danish Ministry of Energy, as a part of the activities in the Solar Energy Centre Denmark. The model of the stand-alone PV system is made up by blocks in or-der to facilitate the modelling of other structures of PV systems.
Many photovoltaic systems operate in a stand-alone mode. Such systems consist of a PV generator, energy storage (for example a battery), AC and DC consum-ers and elements for power conditioning – as sketched in Figure 1. Per defini-tion, a stand-alone system involves no interaction with a utility grid. A PV gen-erator can contain several arrays. Each array is composed of several modules, while each module is composed of several solar cells. The battery bank stores energy when the power supplied by the PV modules exceeds load demand and releases it backs when the PV supply is insufficient. The load for a stand-alone PV system can be of many types, both DC (television, lighting) and AC (elec-tric motors, heaters, etc.). The power conditioning system provides an interface between all the elements of the PV system, giving protection and control. The most frequently encountered elements of the power conditioning system are blocking diodes, charge regulators and DC-AC converters.
Measurement system
The measurement system is shown in Figure 3. The central unit in the meas-urement system is the Analog 6B ADC box. This box collects the analogue data from terminal boxes located in different places on the PV system and converts the signals to digital signals. The digital signals are transmitted on a serial con-nection to the data acquisition PC, where the data is logged on the harddisk.
Component models for stand-alone PV system
The main purpose of this section is to describe the models for the elements of a stand-alone PV system: PV generator, battery, controller, inverter and load. The modelling of the PV system is based on modular blocks, as illustrated in Figure 4. The modular structure facilitates the modelling of the other system structures and replacing of elements, for instance a DC load instead of an AC load.
Battery
An another important element of a stand-alone PV system is the battery. The battery is necessary in such a system because of the fluctuating nature of the output delivered by the PV arrays. Thus, during the hours of sunshine, the PV system is directly feeding the load, the excess electrical energy being stored in the battery. During the night, or during a period of low solar irradiation, energy is supplied to the load from the battery.