Commissioning Example Of An Infeed With Dynamic Grid Support For A Power Grid; Design - Siemens SINAMICS S120 System Manual

Commissioning

7.5 Commissioning example of an infeed with dynamic grid support for a power grid

7.5 Commissioning example of an infeed with dynamic grid support for a
power grid
7.5.1

Design

Photovoltaic plant
The example shows a photovoltaic plant feeding the electrical energy generated into a power
grid.
Closed-loop control
Characteristic for a photovoltaic system is that the energy flows in one direction from the DC
link into the power grid. The optimum operating voltage for the solar cells or the DC link
voltage is highly dependent on the working point, and is decisive for achieving the best
possible efficiency. The setpoint voltage for the maximum power (maximum power point:
MPP) of course depends on the actual intensity of solar radiation but also on many other
parameters, such as the ambient temperature.
A superimposed maximum power-point closed-loop control (MPP) in an external controller
determines the optimum V
Active Line Module.
The Active Line Module is operated in "closed-loop DC link voltage control" mode in this
case.
Design
The solar cells are interconnected in such a manner that they directly charge the DC link of
the Active Line Modules.
Sequence
The higher-level control system closes the optional DC contactors and issues the command
to start the line infeed, provided that sufficient sunlight is present. The DC link voltage
generated from the PV field must correspond to at least 1.5 times the transformer secondary
voltage. First, the grid transformer is magnetized and synchronized with the network. The
required power must be provided from the PV field. The VSM10 performs sensing of the line
voltage on the primary side of the grid transformer until synchronization is achieved. After
synchronization, the circuit breaker is closed and power infeed to the network started.
86
setpoint and transfers this to the closed-loop controller of the
DC
System Manual, 04/2015, A5E03347436A
Grid infeed