ENEL has designed a multi-source energy control and management system to ensure the overall plant performance and reliability. In fact, the management of such kind of plants (located in remote areas where the presence of skilled personnel and the supply of spare parts are critical) has highlighted how the maintenance of the whole system can be very expensive and even requiring long trips by expert technicians. Ginostra Integrated Control and Management System (ICMS) has been designed taking into account these backgrounds.

To supply energy with high reliability and as well optimize the plant overall performance it is necessary to run the plant components using control and Fig. 2 — Ginostra ICMS

regulations methods specially designed.

The experience previously made in such tasks (hybrid prototype developed an run by ENEL) has highlighted that is extremely important that the control and regulation strategy of that kind of plants take into account the following factors:

Overall system reliability

— the system control is performed using a high end programmable logic controller (PLC) made by Siemens;

— no electromechanical actuators components have been used to switch the power conditioning units, they can be controlled directly by the PLC using both analog and digital low power signal;

— a remote plant monitoring/control via GSM modem is implemented in order to evaluate on line plant performance, take the control of the plant and quickly diagnostic the state of health of components;

— accurate main battery charge/discharge regulation will last long this expensive plant component.

— only high end industrial grade components have been selected and used

Plant performance

— accurate energy balance strategy avoid the production of surplus energy.

— minimize the usage of the backup generator (diesel generator set)

The Ginostra ICMS (see figure 2) manage the whole system according to the plant components status, mainly following two operation modes:

Normal operation

During this mode the PV generator supply energy to battery and to the user load (through the GIIGE’s DC/AC converters).

The control system manage the battery status by partially or totally disconnecting the PV generator when the battery voltage reaches an upper threshold, and, will start the back-up diesel generator set when the battery reaches a lower threshold.

When the diesel set is running the battery are charged through the GIIGE’s AC/DC converters, load demand energy is supply both by PV generator (if available) and diesel — set.

Battery charge is achieved by ICMS using the analog regulation control inputs of the embedded GIIGE AC/DC converter performing an accurate battery charge process using both current and voltage regulation. Particularly a constant current charge (at C10) is implemented to avoid main battery stress. The back-up generator set is finally turned off when the battery is fully charged.

In case of more than two power conditioning units (GIIGE) fault or when the battery goes below a protection threshold (even if the diesel back-up generator is on) the ICMS forces the plant into Emergency operation.

Emergency operation

During this mode, if the condition is caused by an excessive battery discharge condition (battery voltage goes below the protection threshold), the GIIGE’s embedded DC/AC converters will turn off, the PV generator will continue to supply energy (as much as can) to battery as well as the diesel generator back-up set. The load demand can be supplied only by the diesel generator set directly connected to the user load.

ICMS will restore the Normal operation condition only when the battery will reach a maximum charge voltage threshold.

If the condition is caused by the simultaneous fault of two of the three plant equipped power conditioning units (GIIGE) the load demand will be supplied only by the diesel generator set directly connected to the user load through the GIIGE’s embedded static — switch. In this unlikely condition ICMS will not restore to the Normal Operation.

This status is irreversible being necessary the presence of technicians who repair the GIIGE’s faults.

ICMS is made of two sub-systems: the plant and the industrial grade PC sub-system running the monitoring/control software.

The failure of the PC subsystem will not affect the normal operation of the plant.

ICMS includes a monitoring/control system based on a industrial grade personal computer that interact with the PLC collecting data and sending appropriate instructions.

This unit perform a user friendly graphic interface (GUI) touch screen based (see figure 3) able to give on-line information about the overall plant or single component. Through this unit it is possible to take the control (local or remote) of the overall plant: this is very helpful in some condition or when the presence of technicians is delayed for whatever reason.

ICMS is also able to evaluate plant components performance and diagnose incipient failure allowing the quick arrangement of the related maintenance.

This monitoring/control system allows also the connection to the plant from remote place using a standard GSM modem. The software design of ICMS has been performed using standard industrial platform: SIEMENS SCL for the PLC embedded firmware and Windows 2000 for the monitoring/control software. Both offer robustness and feasibility. Figure 4 show the ICMS block diagram.

Conclusion

The hybrid PV system realised in Ginostra, with the innovative solutions applied, constitutes therefore an optimal solution for the electrification of isolated communities, answering to the environmental safeguard requirements and to those of reliability and quality of the electrical service.