Method and device for quickly eliminating ferromagnetic resonance of voltage transformer

Abstract

The present invention discloses a method for quickly eliminating ferromagnetic resonance of a voltage transformer. The method includes: first sampling a three-phase voltage and an open-delta voltage of a voltage transformer; calculating a flux linkage corresponding to a zero-sequence voltage by means of an integral algorithm; and when detecting that ferromagnetic resonance occurs in the mutual inductor, further checking whether the absolute value of the flux linkage corresponding to the zero-sequence voltage or the absolute value of the open-delta voltage respectively falls within a set range, and if yes, starting a secondary resonance elimination loop for resonance elimination. The present invention also discloses a corresponding device for quickly eliminating ferromagnetic resonance of a voltage transformer. The present method and device accurately analyze and control resonance elimination trigger time based on a conventional secondary resonance elimination principle, and can effectively eliminate the impact of the core saturation of a voltage transformer on a resonance elimination process, thereby greatly improving the success probability of single resonance elimination.

Claims

1. A method for quickly eliminating ferromagnetic resonance of a voltage transformer, comprising the following steps: step 1: collecting a three-phase voltage secondary value and an open-delta voltage of a voltage transformer in real time; step 2: calculating a flux linkage ψ.sub.0 corresponding to a zero-sequence voltage in real time according to the three-phase voltage secondary value or the open-delta voltage collected in real time; and step 3: when detecting that ferromagnetic resonance occurs in the voltage transformer, further checking whether an absolute value of the flux linkage corresponding to the zero-sequence voltage or an absolute value of the open-delta voltage respectively falls within a set range, if yes, triggering a silicon controlled rectifier resonance elimination loop connected in parallel to both ends of an open-delta winding of the voltage transformer to be quickly turned on, to eliminate ferromagnetic resonance, and if not, not triggering the silicon controlled rectifier resonance elimination loop to be turned on.

2. The method for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 1, wherein in the step 2, the flux linkage ψ.sub.0 corresponding to the zero-sequence voltage is calculated by means of the three-phase voltage secondary value or the open-delta voltage with a calculation formula shown as follows:
ψ.sub.0=−∫(U.sub.A+U.sub.B+U.sub.C)dt
or ψ.sub.0=−∫(3U.sub.0)dt wherein U.sub.A, U.sub.B, U.sub.C, and 3 U.sub.0 are three-phase voltage secondary values and an open-delta voltage, respectively.

3. The method for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 1, wherein in the step 3, the ferromagnetic resonance occurring in the voltage transformer comprises fractional-frequency ferromagnetic resonance, fundamental-frequency ferromagnetic resonance, and multiple-frequency ferromagnetic resonance.

4. The method for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 1, wherein in the step 3, the absolute value of the flux linkage corresponding to the zero-sequence voltage falling within the set range means that the flux linkage ψ.sub.0 corresponding to the zero-sequence voltage satisfies |ψ.sub.0|≤K1*ψ.sub.N, wherein K1 is a coefficient, ${\psi }_N=\frac{U_m}{\omega },U_m$ is a rated secondary voltage peak value of the voltage transformer, and ω power-frequency angular frequency.

5. The method for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 1, wherein in the step 3, the absolute value of the open-delta voltage falling within the set range means that the absolute value of the open-delta voltage 3 U.sub. satisfies |3 U.sub.0|≥K2*U.sub.max, wherein U.sub.max is the maximum value of the open-delta voltage collected in the previous resonance period when the resonance is detected, and K2 is a coefficient.

6. The method for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 1, wherein in the step 3, a silicon controlled rectifier loop comprises a silicon controlled rectifier capable of being bidirectionally turned on and a resonance elimination resistor connected in series thereto; the silicon controlled rectifier loop is mounted in parallel at the output port of an open-delta loop on the secondary side of the voltage transformer, and is connected in parallel to an open-delta voltage measurement loop.

7. The method for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 1, wherein in the step 3, triggering the silicon controlled rectifier loop means issuing a turn-on instruction to a silicon controlled rectifier in the loop, so that the silicon controlled rectifier is in an ON state in both forward and reverse directions.

8. A device for quickly eliminating ferromagnetic resonance of a voltage transformer, comprising a collection unit, a calculation unit, and a detection and resonance elimination unit, wherein: the collection unit collects a three-phase voltage secondary value and an open-delta voltage of a voltage transformer in real time; the calculation unit receives measured data of the collection unit, and calculates a flux linkage ψ.sub.0 corresponding to a zero-sequence voltage in real time according to the three-phase voltage secondary value or the open-delta voltage collected in real time; and the detection and resonance elimination unit receives the measured and calculated data of the collection unit and the calculation unit, and when detecting that ferromagnetic resonance occurs in the voltage transformer, further checks whether the absolute value of the flux linkage corresponding to the zero-sequence voltage or the absolute value of the open-delta voltage respectively falls within a set range, if yes, triggers a silicon controlled rectifier resonance elimination loop connected in parallel to both ends of an open-delta winding of the voltage transformer to be quickly turned on, to eliminate ferromagnetic resonance, and if not, does not trigger the silicon controlled rectifier resonance elimination loop to be turned on.

9. The device for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 8, wherein in the calculation unit, the flux linkage ψ.sub.0 corresponding to the zero-sequence voltage is calculated by means of the three-phase voltage secondary value or the open-delta voltage with a calculation formula shown as follows:
ψ.sub.0=−∫(U.sub.A+U.sub.B+U.sub.C)dt
or ψ.sub.0=−∫(3U.sub.0)dt wherein U.sub.A, U.sub.B, U.sub.C, and 3 U.sub.0 are three-phase voltage secondary values and an open-delta voltage, respectively.

10. The device for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 8, wherein in the detection and resonance elimination unit, the absolute value of the flux linkage corresponding to the zero-sequence voltage falling within the set range means that the flux linkage ψ.sub.0 corresponding to the zero-sequence voltage satisfies |ψ.sub.0|≤K1*ψ.sub.N, wherein K1 is a coefficient, ${\psi }_N=\frac{U_m}{\omega },U_m$ is a rated secondary voltage peak value of the voltage transformer, and ω is power-frequency angular frequency.

11. The device for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 8, wherein in the detection and resonance elimination unit, the absolute value of the open-delta voltage falling within the set range means that the absolute value of the open-delta voltage 3 U.sub.0 satisfies |3 U.sub.0|≥K2*U.sub.max, wherein U.sub.max is the maximum value of the open-delta voltage collected in the previous resonance period when the resonance is detected, and K2 is a coefficient.

12. The device for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 8, wherein in the detection and resonance elimination unit, a silicon controlled rectifier loop comprises a silicon controlled rectifier capable of being bidirectionally turned on and a resonance elimination resistor connected in series thereto; the silicon controlled rectifier loop is mounted in parallel at the output port of an open-delta loop on the secondary side of the voltage transformer, and is connected in parallel to an open-delta voltage measurement loop.

13. The device for quickly eliminating ferromagnetic resonance of a voltage transformer according to claim 8, wherein in the detection and resonance elimination unit, triggering the silicon controlled rectifier loop means issuing a turn-on instruction to a silicon controlled rectifier in the loop, so that the silicon controlled rectifier is in an ON state in both forward and reverse directions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic flowchart of a method according to the present invention; and

(2) FIG. 2 is a schematic diagram of a silicon controlled rectifier resonance elimination loop.

DETAILED DESCRIPTION

(3) Further description is made below with reference to the accompanying drawings and the specific embodiments.

(4) The present invention provides a method for quickly eliminating ferromagnetic resonance of a voltage transformer, as shown in FIG. 1 which is a schematic flowchart of a method according to the present invention, including the following steps: step 1: collecting a three-phase voltage secondary value and an open-delta voltage of a voltage transformer in real time; step 2: calculating a flux linkage ψ.sub.0 corresponding to a zero-sequence voltage in real time according to the three-phase voltage secondary value or the open-delta voltage collected in real time; and step 3: when detecting that ferromagnetic resonance occurs in the voltage transformer, further checking whether the absolute value of the flux linkage corresponding to the zero-sequence voltage or the absolute value of the open-delta voltage respectively falls within a set range, if yes, triggering a silicon controlled rectifier resonance elimination loop connected in parallel to both ends of an open-delta winding of the voltage transformer to be quickly turned on, to eliminate ferromagnetic resonance, and if not, not triggering the silicon controlled rectifier resonance elimination loop to be turned on.

(5) Furthermore, in the step 2, the flux linkage ψ.sub.0 corresponding to the zero-sequence voltage is calculated by means of the three-phase voltage secondary value or the open-delta voltage with a calculation formula shown as follows:
ψ.sub.0=−∫(U.sub.A+U.sub.B+U.sub.C)dt
or ψ.sub.0=−∫(3U.sub.0)dt

(6) wherein U.sub.A, U.sub.B, U.sub.C, and 3 U.sub.0 are three-phase voltage secondary values and an open-delta voltage, respectively.

(7) Furthermore, in the step 3, the ferromagnetic resonance occurring in the voltage transformer includes fractional-frequency ferromagnetic resonance, fundamental-frequency ferromagnetic resonance, and multiple-frequency ferromagnetic resonance.

(8) Furthermore, in the step 3, the absolute value of the flux linkage corresponding to the zero-sequence voltage falling within the set range means that the flux linkage ψ.sub.0 corresponding to the zero-sequence voltage satisfies |ψ.sub.0|≤K1*ψ.sub.N, wherein K1 is a coefficient,

(9) ${\psi }_N=\frac{U_m}{\omega },$
U.sub.m is a rated secondary voltage peak value of the voltage transformer, and ω is power-frequency angular frequency. The value range of K1 may be 0.01-0.2.

(10) Furthermore, in the step 3, the absolute value of the open-delta voltage falling within the set range means that the absolute value of the open-delta voltage 3U.sub.0 satisfies |3U.sub.0|≥K2*U.sub.max, wherein U.sub.max is the maximum value of the open-delta voltage collected in the previous resonance period when the resonance is detected, and K2 is a coefficient. The value range of K2 may be 0.8-1.0.

(11) Furthermore, in the step 3, a silicon controlled rectifier loop includes a silicon controlled rectifier capable of being bidirectionally turned on and a resonance elimination resistor connected in series thereto; the silicon controlled rectifier loop is mounted in parallel at the output port of an open-delta loop on the secondary side of the voltage transformer, and is connected in parallel to an open-delta voltage measurement loop. FIG. 2 is a schematic diagram of a silicon controlled rectifier resonance elimination loop.

(12) Furthermore, in the step 3, triggering the silicon controlled rectifier loop means issuing a turn-on instruction to a silicon controlled rectifier in the loop, so that the silicon controlled rectifier is in an ON state in both forward and reverse directions.

(13) An ungrounded system normally has no zero-sequence voltage, i.e., the open-delta voltage 3 U.sub.0=0V. The flux linkage corresponding to the zero-sequence voltage is ψ.sub.0=−∫(3 U.sub.0)dt=0.

(14) For a general voltage transformer, the rated value of a phase voltage of the secondary side is 57.74 V and the peak value is 57.74√{square root over (2)} V. According to the descriptions of the summary, the rated value of the flux linkage corresponding to the zero-sequence voltage may be obtained, i.e.,

(15) ${\psi }_N=\frac{U_m}{\omega }=\frac{57.74V.Math.\sqrt{2}}{2\pi .Math.50\mathrm{Hz}}=\frac{\sqrt{2\text{/}3}}{\pi }\mathrm{Wb}.$

(16) At a certain time, triple-frequency resonance occurs in the system; in this case, a triple-frequency voltage appears at the open delta, an open-delta voltage value when the resonance occurs is set to U.sub.0=A.sub.0 sin(3 ωt), where A.sub.0 is the magnitude of a triple-frequency voltage and is 300 V, and 3ω=3×2π×50 Hz is resonance angular frequency of triple frequency.

(17) (1) Trigger time is calculated according to the flux linkage corresponding to the zero-sequence voltage

(18) According to the formula in the step 2, the flux linkage ψ.sub.0 corresponding to the zero-sequence voltage may be calculated and is

(19) ${\psi }_0=-\int \left(3U_0\right)\mathrm{dt}=-\int \left(300V.Math.\sin \left(300\pi .Math.t\right)\right)\mathrm{dt}=\frac{1}{\pi }.Math.\cos \left(300\pi .Math.t\right)\mathrm{Wb}$

(20) when ψ.sub.0 satisfies |ψ.sub.0|≤K*ψ.sub.N, the resonance elimination loop is triggered to be turned on, the coefficient is K=0.2, and

(21) $-0.2\times \frac{\sqrt{2\text{/}3}}{\pi }\le \frac{1}{\pi }.Math.\cos \left(300\pi .Math.t\right)\le 0.2\times \frac{\sqrt{2\text{/}3}}{\pi }$
the value of t may be obtained and is

(22) $\frac{2\pi n+1.4068}{300\pi }\le t\le \frac{2\pi n+1.7348}{300\pi }\left(n=0,1,2\mathrm{.Math.}\right)\mathrm{or}\frac{2\pi n-1.7348}{300\pi }\le t\le \frac{2\pi n-1.4068}{300\pi }\left(n=1,2,3\mathrm{.Math.}\right)$
that is, when t is within the above range, conditions of the flux linkage ψ.sub.0 are satisfied, and the resonance elimination loop is triggered to be turned on.

(23) (2) The trigger time is calculated according to the open-delta voltage the open-delta voltage is 3 U.sub.0=300 sin(300π.Math.t), the maximum value of the open-delta voltage is 3 U.sub.0.max=300V, the open-delta voltage satisfies |3 U.sub.0|≥K.Math.U.sub.0.max, the coefficient is K=0.9, and |300 sin(300π.Math.t)|≥300×0.9; the value of t may be obtained and is

(24) $\frac{2\pi n+1.120}{300\pi }\le t\le \frac{2\pi n+2.022}{300\pi }\left(n=0,1,2\mathrm{.Math.}\right)\mathrm{or}\frac{2\pi n-2.022}{300\pi }\le t\le \frac{2\pi n-1.120}{300\pi }\left(n=1,2,3\mathrm{.Math.}\right)$

(25) that is, when t is within the above range, conditions of the open-delta voltage are satisfied, and the resonance elimination loop is triggered to be turned on.

(26) The trigger time range calculated according to the flux linkage ψ.sub.0 corresponding to the zero-sequence voltage overlaps the trigger time range calculated according to the open-delta voltage in most cases. When the open-delta voltage is the maximum value at resonance, the corresponding flux linkage is basically the minimum value. Therefore, the trigger time calculated by the two methods is basically the same, and there is no conflict between the two methods.

(27) The present invention also provides a device for quickly eliminating ferromagnetic resonance of a voltage transformer, comprising a collection unit, a calculation unit, and a detection and resonance elimination unit, wherein

(28) the collection unit collects a three-phase voltage secondary value and an open-delta voltage of a voltage transformer in real time;

(29) the calculation unit receives measured data of the collection unit, and calculates a flux linkage ψ.sub.0 corresponding to a zero-sequence voltage in real time according to the three-phase voltage secondary value or the open-delta voltage collected in real time; and

(30) the detection and resonance elimination unit receives the measured and calculated data of the collection unit and the calculation unit, and when detecting that ferromagnetic resonance occurs in the voltage transformer, further checks whether the absolute value of the flux linkage corresponding to the zero-sequence voltage or the absolute value of the open-delta voltage respectively falls within a set range, if yes, triggers a silicon controlled rectifier resonance elimination loop connected in parallel to both ends of an open-delta winding of the voltage transformer to be quickly turned on, to eliminate ferromagnetic resonance, and if not, does not trigger the silicon controlled rectifier resonance elimination loop to be turned on.

(31) Furthermore, in the calculation unit, the flux linkage ψ.sub.0 corresponding to the zero-sequence voltage is calculated by means of the three-phase voltage secondary value or the open-delta voltage with a calculation formula shown as follows:
ψ.sub.0=−∫(U.sub.A+U.sub.B+U.sub.C)dt
or ψ.sub.0=−∫(3U.sub.0)dt

(32) wherein U.sub.A, U.sub.B, U.sub.C, and 3 U.sub.0 are three-phase voltage secondary values and an open-delta voltage, respectively.

(33) Furthermore, in the detection and resonance elimination unit, the absolute value of the flux linkage corresponding to the zero-sequence voltage falling within the set range means that the flux linkage ψ.sub.0 corresponding to the zero-sequence voltage satisfies |ψ.sub.0|≤K1*ψ.sub.N, wherein K1 is a coefficient,

(34) ${\psi }_N=\frac{U_m}{\omega },U_m$
is a rated secondary voltage peak value of the voltage transformer, and ω is power-frequency angular frequency. The value range of K1 may be 0.01-0.2.

(35) Furthermore, in the detection and resonance elimination unit, the absolute value of the open-delta voltage falling within the set range means that the absolute value of the open-delta voltage 3 U.sub.0 satisfies |3 U.sub.0|≥K2*U.sub.max wherein U.sub.max is the maximum value of the open-delta voltage collected in the previous resonance period when the resonance is detected, and K2 is a coefficient. The value range of K2 may be 0.8-1.0.

(36) Furthermore, in the detection and resonance elimination unit, a silicon controlled rectifier loop includes a silicon controlled rectifier capable of being bidirectionally turned on and a resonance elimination resistor connected in series thereto; the silicon controlled rectifier loop is mounted in parallel at the output port of an open-delta loop on the secondary side of the voltage transformer, and is connected in parallel to an open-delta voltage measurement loop.

(37) Furthermore, in the detection and resonance elimination unit, triggering the silicon controlled rectifier loop means issuing a turn-on instruction to a silicon controlled rectifier in the loop, so that the silicon controlled rectifier is in an ON state in both forward and reverse directions.

(38) The foregoing embodiments are only intended to explain the technical idea of the present invention, and cannot be used for limiting the scope of protection of the preset invention. Any equivalent replacement or modification made based on the technical solutions according to the technical idea proposed by the present invention does not exceed the scope of protection of the present invention.