Laboratory-scale demonstration
121 I∗ I
I (p.u.)
1 0 -1 0
0.01
0.02
0.03
0.04 t (s)
0.05
0.06
0.07
0.08
(a) Simulation. I∗ I
I (p.u.)
1 0 -1 0
0.01
0.02
0.03
0.04 t (s)
0.05
0.06
0.07
0.08
(b) Measurement.
Figure 6.5: Converter response to step function in reactive power reference value from 0 to 1 p.u.
6.2.2
Changing voltage reference value
When Converter 2 supplies a radial network section (LB2 is open), it is in V control mode. During mode transitions, small changes in the reference value for the voltage amplitude can occur. To assess the converter response to such changes, the voltage reference signal is changed from 0.9 to 1.1 p.u. while supplying a 0.9 p.u. load. Figure 6.6 shows the simulated and measured converter response. The converter response to a stepwise change of the voltage reference signal reaches steady state within a few milliseconds.
6.2.3
Changing load
A converter in V control mode supplies or consumes the power to and from connected loads and generators as needed. In the experimental set-up, load-break switch LB2 is open. To assess the converter response to load changes, a load is connected at t = 0. This test is performed to verify the response of two controllers: the AC voltage controller and the DC voltage controller. AC voltage controller response After connection of the 0.9 p.u. load, the AC voltage controller of Converter 2 changes the reference current signal to maintain the voltage on the AC port of Converter 2. In