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5
Preload resistor
6
Main contactor
7
Auxiliary fuses
8
Neutral cable connection (not mandatory)
9
Battery connection
The current generator is physically organized in power units. Each unit enclosure
contains one power unit. An ESI-S inverter can contain up to 4 power units. Power units
can be combined in a master-slave arrangement, or in a master-master arrangement,
the latter giving full operational redundancy. The current rating of different units must
be of the same rating. Please refer to
unit ratings.
In
Figure 12
it may be seen that each current generator consists of an IGBT-inverter
bridge (1) that is controlled using PWM-switching technology. Information from the
controller is sent to the IGBTs through one flat cable. At the output of the inverter a
voltage waveform is generated which contains the desired spectral components
(imposed by the inverter controller) as well as high frequency noise (due to the IGBT
switching technology). Coupling impedance consisting of a reactor (3) and a high
frequency rejection inverter (4) ensures that the useful voltage components are
converted into a useful current while the high frequency noise is absorbed. The IGBT-
inverter is equipped with DC capacitors that act as energy storage reservoirs (2).
The battery is connected (9) on the DC capacitors (4) of the inverter. The preload of these
DC capacitors is done thanks to the grid. This avoid inrush current coming from the
battery.
All units contain a DC capacitors preloading resistor (5) which charges the DC capacitors
up to the peak AC voltage once the auxiliary fuse box of the unit(s) is closed. This
approach ensures a smooth inverter start-up without excessive inrush currents from the
grid. Later in the start-up sequence the IGBT switching pattern will charge more the DC
capacitors in order to reach the battery voltage and ensure a connection to the battery
without inrush currents.
In ESS system containing more than one power unit the control information between
different units passes through a CAN control cable.
If a master-master configuration of inverter is chosen, all power units incorporate an
ESI-Manager display. If a master-slave configuration of inverter is chosen, only the
master enclosure contains an ESI-Manager display.
4.4 The ESI main controller
The ESI main controller controls the complete inverter system. Its tasks include:
-
Accepting and executing customer requests to stop and start the equipment;
-
Calculating and generating IGBT-inverter control references based on the user
requirements and line current measurements ;
18 Hardware description ç Manual Energy Storage Inverter ESI-S
Chapter 12
for more information on the possible
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