Parallel Operation of Inverters - Control of Power Inverters in Renewable Energy and Smart Grid Integration - page 289

E i ω i

E *

*

ω

*

E = E − n P

i i i

ω = ω

*

+ m Q

i i i

Capacitive Inductive

0 0

P i *

P i

Q i *

Q i

(a) for R-inverters

ω i E i

E *

*

ω

*

ω = ω − m P

E = E

*

− n Q

i i i

i i i

Capacitive Inductive

0 0

P i * P i Q i * Q i

(b) for L-inverters

E i

ω i

E *

*

ω

ω = ω

*

+ m P *

E = E + n Q

i i i

i i i

Capacitive Inductive

0 0

P i * P i Q i * Q i

(c) for C-inverters

Figure 19.3 Droop control strategies

where ∼ means in proportion to. Hence, the conventional droop control strategy takes the

form

E ∗ −

E i = n i P i ,

ω i = ω ∗ + m i Q i ,

This strategy, consisting of the Q − ω and P − E droop, is illustrated in Figure 19.3(a). In

this case, P Q and Q =− =

P .

19.4.2 For L-inverters
When the output impedance is inductive, 90 ◦ . Then θ =

EV o
Z o

EV o
Z o

V o

P = sin δ and Q = cos δ −

Z o .