Synchronverters: Grid-friendly Inverters that Mimic Synchronous Generators - Control of Power Inverters in Renewable Energy and Smart Grid Integration - page 269

and the phase terminal voltages (18.3) become

⎡ ⎤

⎦ M d i N

1
1
1

L s d i

⎣

v =− R s i −

dt + dt +

e ,

where e is given by (18.4). The other formulae are not affected.
The presence of a neutral line makes the system model somewhat more complicated.
However, in a synchronverter to be designed in the next section, M is a design parameter that
can be chosen to be 0. The physical meaning of this is that there is no magnetic coupling
between the stator windings, which does not happen in a physical synchronous generator but
can easily be implemented in a synchronverter. When a neutral line is needed, it is advantageous
to take M 0 and then to provide a neutral line with the strategies discussed in Part II. The

choice of M and L individually is irrelevant; what matters is only L s =

=

M . In the sequel,
the model of a synchronous generator consisting of (18.3), (18.4), (18.6) and (18.7) will be
used to operate an inverter as a synchronverter.

L +

18.2 Implementation of a Synchronverter
In this section, the details of how to implement an inverter as a synchronverter are described.
A synchronverter consists of a power part and an electronic part. The power part is a simple
inverter used to convert DC power into three-phase AC as shown in Figure 18.2. The electronic
part is an electronic controller that runs a program in a processor to control the switches shown
in Figure 18.2. The core of the electronic part is the mathematical model of a synchronous
generator, shown in Figure 18.3. These two parts interact via the signals e and i , in addition to
v

and v g that are used for controlling the synchronverter.

18.2.1 Power Part
This part consists of three phase legs and a three-phase LC filter, which is used to suppress the
switching noise. If the inverter is to be connected to the grid, then three more inductors and a

+

Circuit
Breaker

L g , R g

L s , R s

v a

i a

v ga

e a

v b

i b

V DC

v gb

e b

v c

i c

v gc

e c

C

-

Figure 18.2 Power part of a synchronverter: a basic inverter