Hybrid PLL for grid synchronization in distributed generation
Systems, methods, and devices relating to the extraction of parameters for a grid voltage. A multi-block hybrid PLL or hybrid observer receives grid voltage. The grid voltage is received by a harmonic/noise decomposer block which separates the harmonic/noise component of the incoming voltage from the clean voltage signal. The clean voltage signal is then output from the PLL/observer. The clean voltage signal is also sent to an amplitude estimator block which estimates the amplitude of the clean voltage signal. The harmonic/noise component of the input voltage signal is sent, along with the clean voltage signal, to a frequency estimator block. The frequency estimator block then determines the phase angle of the incoming signal as well as the frequency of the incoming voltage signal.
1. A system to synchronize grid-connected power converters with a power grid including establishing parameters of an incoming grid voltage signal, the system comprising:
a harmonic/noise decomposer embodied in a first circuit that decomposes said incoming grid voltage signal, said harmonic/noise decomposer receiving said incoming grid voltage signal and, from said incoming grid voltage signal, producing an estimate of a harmonic/noise component of said incoming grid voltage signal and a sinusoidal clean voltage signal that is said incoming grid voltage signal without said harmonic/noise component;
a frequency estimator embodied in a second circuit that estimates a frequency and phase angle of said incoming grid voltage signal, said frequency estimator receiving said sinusoidal clean voltage signal from said harmonic/noise decomposer and producing an estimate of a frequency of said sinusoidal clean voltage signal and values related to a phase angle of said sinusoidal clean voltage signal; and
an amplitude estimator embodied in a third circuit that estimates an amplitude of said incoming grid voltage signal, said amplitude estimator receiving said sinusoidal clean voltage signal from said harmonic/noise decomposer and producing an estimate of an amplitude of said sinusoidal clean voltage signal from said sinusoidal clean voltage signal;
wherein
said estimate of said amplitude of said sinusoidal clean voltage signal from said amplitude estimator is received by said frequency estimator, and at least each said estimated harmonic/noise component, estimated frequency, and estimated amplitude are provided to an interface with a grid-connected power converter.
2. The system according to claim 1 , wherein said incoming grid voltage signal is a voltage of a utility power grid.
3. The system according to claim 1 , wherein said first circuit embodying said harmonic/noise decomposer is represented by:
Θ
g
Obs
:
{
ϑ
^
.
1
=
ω
ϑ
^
2
+
ω
ϑ
1
+
ω
ξ
^
1
+
ξ
^
2
+
μ
1
ϑ
~
1
ϑ
^
.
2
=
-
2
ω
ϑ
1
-
ω
ϑ
^
2
+
μ
2
ϑ
~
1
ξ
^
.
1
=
ξ
^
2
ξ
^
.
2
=
γ
1
ϑ
~
1
where
{tilde over (ϑ)} 1 =ϑ 1 −{circumflex over (ϑ)} 1 ; and
{dot over ({circumflex over (ξ)})} 1 , is an estimate of said harmonic/noise component.
4. The system according to claim 1 , wherein said second circuit embodying said frequency estimator is represented by:
Ψ
Frq
Obs
:
{
v
.
1
=
-
β
1
v
1
-
v
2
v
^
.
2
=
v
^
3
+
β
1
v
2
+
σ
^
v
1
+
β
2
v
~
2
v
^
.
3
=
-
β
1
v
^
3
-
β
1
2
v
2
+
β
3
v
~
2
σ
^
.
=
γ
2
v
1
v
~
2
φ
^
.
=
γ
3
cos
θ
^
(
v
2
-
A
^
sin
θ
^
)
θ
^
=
∫
σ
^
d
t
+
φ
^
wherein
{tilde over (v)} 2 =v 2 −{circumflex over (v)} 2 ;
{circumflex over (θ)} is an estimate of said phase angle of said incoming signal; and
f
^
=
σ
^
2
π
=
estimated
frequency
of
said
incoming
signal
.
5. The system according to claim 1 , wherein said third circuit embodying said amplitude estimator is represented by:
O
Amp
Obs
:
{
η
^
.
1
=
2
ω
η
^
2
+
2
ω
η
1
+
2
ω
δ
^
+
α
1
η
~
1
η
^
.
2
=
-
4
ω
η
1
-
2
ω
η
^
2
+
α
2
η
~
1
δ
^
.
=
2
ω
γ
4
η
~
1
where
{tilde over (η)} 1 =η 1 −{circumflex over (η)} 1 ; and
Â=√{square root over ({circumflex over (δ)})}=estimated amplitude for said incoming signal.
6. The system according to claim 1 , wherein said system is used to estimate parameters for a grid voltage for a power utility grid.
7. The system according to claim 6 , wherein said parameters are for use in synchronizing said grid-connected power converter connected to said power utility grid.