Integration methods for energy metering systems using a Rogowski coil
View Patent ↗Devices and methods for accurately realizing the integration functions, in particular for energy metering systems using a Rogowski coil, are disclosed. In this regard, exemplary embodiments of the present invention may be constructed as two stable filters for the current (I) and voltage (U) channel. In the analog realization form, the transfer function of the voltage channel may be constructed as a high-pass filter function with at least one zero at the origin, while the transfer function of the current channel may be constructed as the multiplication of the high-pass filter function of the voltage channel and the ideal analog integration function. In the digital realization form, the transfer function of the filter for the voltage channel may be constructed as a high-pass filter function with zero(s) at the same location(s) as the pole(s) of the digital integration function, while the transfer function of the filter for the current channel is the multiplication of the high-pass filter function of the voltage channel and the digital integration function.
1. A method of realizing an ideal analog integration function in energy measuring, comprising:
utilizing a Rogowski coil to sense the time derivative of current;
operating a first analog stable filter to process a signal input in a current channel; and
operating a second analog stable filter to process a signal input in a voltage channel.
2. The method of claim 1 , wherein said operating a first analog stable filter to process a signal input in a current channel comprises operating said first analog stable filter to implement a transfer function having at least one zero at origin.
3. The method of claim 2 , wherein said operating a second analog stable filter to process a signal input in a voltage channel comprises operating said second analog stable filter to implement a transfer function having at least one zero at the origin and said ideal analog integration function.
4. A system for realizing an ideal analog integration function in energy measuring, comprising:
a Rogowski coil for sensing the time derivative of current;
a first analog stable filter operatively coupled to the Rogowski coil, said first analog stable filter configured to process a signal input in a current channel of the system; and
a second analog stable filter operatively coupled to the Rogowski coil, said second stable filter configured to process a signal input in a voltage channel of the system.
5. The system of claim 4 , wherein one of said analog filters comprises a circuit element for implementing a high-pass function having at least one zero at the origin.
6. The system of claim 5 , wherein the other of said analog filters comprises a circuit element for implementing a high-pass function having at least one zero at the origin and said ideal analog integration function.
7. A method of realizing an ideal digital integration function in energy measuring, comprising:
utilizing a Rogowski coil for sensing the time derivative of current;
digitizing a signal input in a current channel;
operating a first digital stable filter to process the signal input in the current channel;
digitizing a signal input in a voltage channel; and
operating a second digital stable filter to process the signal input in the voltage channel.
8. The method of claim 7 , wherein said operating a first digital stable filter to process the signal input in the current channel comprises operating said first digital stable filter to implement a transfer function having zero or zeroes at the exact pole positions of said digital integration function.
9. The method of claim 8 , wherein said operating a second digital stable filter to process the signal input in the voltage channel further comprises operating said second digital stable filter to implement a transfer function having zero or zeroes at the exact positions of said digital integration function and said digital integration function.
10. A system for realizing an ideal digital integration function in energy measuring, comprising:
a Rogowski coil for sensing the time derivative of current;
a first AD converter disposed in a current channel of the system and operatively coupled to the Rogowski coil;
a first digital stable filter operatively coupled to the first AD converter, said first digital stable filter configured to process a signal input in the current channel;
a second AD converter disposed in a voltage channel of the system and operatively coupled to the Rogowski coil; and
a second digital stable filter operatively coupled to the second AD converter, said second digital stable filter configured to process a signal input in the voltage channel.
11. The system of claim 10 , wherein one of said digital filters comprises a circuit element for implementing a high-pass function with at least the equal number of zeros at the poles of said digital integration function.
12. The system of claim 11 , wherein the other of said digital filters comprises a circuit element for implementing a high-pass function with at least the equal number of zeros at the poles said digital integration function and said digital integration function.
13. The system of claim 10 , wherein said first digital filter comprises a circuit element for implementing a transfer function given by
H
I
(
z
-
1
)
=
k
(
1
-
z
-
1
)
1
-
kz
-
1
·
k
(
1
+
z
-
1
)
2
(
1
-
kz
-
1
)
,
k
=
1
-
2
-
6
,
and said second digital filter comprises a circuit element for implementing a transfer function given by
H
U
(
z
-
1
)
=
k
(
1
-
z
-
1
)
1
-
kz
-
1
·
k
(
1
-
z
-
1
)
1
-
kz
-
1
,
k
=
1
-
2
-
6
.
14. The method of claim 1 , wherein said operating a second analog stable filter to process a signal input in a voltage channel comprises operating said second analog stable filter to implement a transfer function having at least one zero at the origin.
15. The method of claim 14 , wherein said operating a first analog stable filter to process a signal input in a current channel comprises operating said first analog stable filter to implement a transfer function having at least one zero at the origin and said ideal analog integration function.