The TRIMODE Power Processor optimizes power flow in hybrid generator systems that have photovoltaic arrays, batteries and a diesel generator. It operates in three modes -
First, it may operate as an inverter providing power from the batteries to the load with the diesel generator turned off. Second, it may operate as a battery charger delivering power from the diesel generator. Third, it operates in parallel with the diesel generator to provide a bumpless transfer and to augment the total power available.
The Power Processing Center (PPC) - The 480 VAC three-phase grid can be serviced either from the diesel engine generator or the three-phase TRIMODE power Processor.
The Alternate energy source is the photovoltaic array. At the output of the array is a rectifier, whose function is to block reverse power flow into the array from the battery - a vital protection for array.
Interfacing between the array and the battery is an optional DC-DC Max Power Tracker (MPT). Considering the rated power of the system components and the broad range of the operating voltage for both the photovoltaic array and the battery; the economics of the system cost easily justify the added purchase cost of the MPT. An added advantage of including the MPT in the system is that the on-off controller for the battery is no longer needed.
The Power Processor Controller (PPC) keeps record on the status of the array, the battery, and the diesel engine generator and delivers start / stop commands to the diesel; Whenever the diesel is supplied power through the SS Relay, the TRIMODE automatically goes into the charger mode.
The most desirable mode of operation is with the array supplying power via the MPT and the battery to the TRIMODE as a inverter; and the inverter supplying the 480 VAC grid with the diesel engine generator off thereby minimizing fuel consumption.
One of the PPC design objectives is to achieve load management and load balancing. This is best achieved by having a separate control for the inverter in each phase. A significant benefit from this design approach is that a failure in one inverter will not migrate to the other inverters, and modular repairs need be made to one third of the system only.
In the protective circuit interface, loss or out-of-tolerance on any phase voltage from the diesel will automatically transfer all three phases of the load to the inverter. Failure of any phase of the inverter will automatically shut down the system until the diesel is ready to supply the load. The UPS in the PPC supplies the control power.
Single Phase Load Management
By applying load management to the individual phases, the battery charging function can be used to obtain full load operation on each of the generators phase when the load on the grid plus the battery charger rating exceeds the rating of the diesel engine generator. This is accomplished by setting the battery charger power for each phase to be equal to the generator power rating per phase less the power on that phase being delivered to the grid.
The table below demonstrates the load management concept. Assume that the generator rating if 50 KW and the battery charger rating is 25 KW the power, and that the grid draws loads from zero to 40 KW in different periods.
Solar Modules
Battery Based Inverters
