A method and device for detecting short circuit on secondary side of phase-shifting transformer

Abstract

The present invention provides a method and device for detecting short circuit on the secondary side of a phase-shifting transformer. The method and device detect short circuit on the secondary side of the phase-shifting transformer by real-time sampling of the primary side voltage and the primary side current, and calculating the reactive power on the primary side, the negative sequence component of the primary side current, and the zero sequence current component of the primary side current, so as to determine whether the secondary side of the phase-shifting transformer is short-circuited; and weight coefficients are designed for the reactive power on the primary side, the negative sequence component of the primary side current, and the zero sequence current component of the primary side current, so as to determine whether the short circuit type belongs to three-phase short circuit, single-phase short circuit, or short circuit to ground. The present invention can not only quickly detect the short circuit problem on the secondary side of a multi-secondary phase-shifting transformer, but also determine the type of short circuit on the secondary side, accurately analyze the short circuit type, and improve the practical life of the phase-shifting transformer.

Description

Technical Field

[0001] The present invention relates to the field of transformer protection, and in particular to a method and device for detecting short circuit on the secondary side of a phase-shifting transformer. Background Art

[0002] Cascaded multi-level high-voltage inverters have the characteristics of mature technology, low harmonics on the grid side and the motor side, high power factor, and relatively low price. They play an important role in reducing energy consumption and improving processes, especially for high-pressure fans and water pumps. The energy-saving effect is significant. At present, they have been widely used in steel, petrochemical, mining, metallurgy, urban construction and other application fields.

[0003] The multi-side phase-shifting transformer in the cascade type high-voltage inverter has the functions of stepping down, shifting phase, and supplying power to the power unit. However, once the secondary side load (power unit side) of the multi-side phase-shifting transformer is short-circuited or the secondary side is directly short-circuited, the secondary side current will reach more than 20 times the rated current. The mechanical stress and heat generated by the short-circuit current will endanger the reliable operation of the entire multi-side transformer and even destroy the transformer. Therefore, it is necessary to detect and protect the short circuit on the secondary side of the multi-side transformer. At present, the existing detection methods include detecting the current of each secondary winding and detecting the primary current. Detecting the current of each secondary winding not only increases the cost, but also increases the burden on the control system, and has poor reliability. The primary current detection method is difficult to identify accurately. Summary of the invention

[0004] To solve the above problems, the present invention provides a method and device for detecting short circuit on the secondary side of a phase-shifting transformer. The method can not only quickly detect the short circuit problem on the secondary side of the phase-shifting transformer, but also determine the type of secondary side short circuit, perform accurate fault analysis based on the short circuit type, and improve the service life of the phase-shifting transformer.

[0005] A method for detecting short circuit on the secondary side of a phase-shifting transformer comprises the following steps: Step S1: real-time sampling of primary side voltage , , and the instantaneous value of the primary current , , .

[0006] Step S2: According to the primary side voltage , , and the instantaneous value of the primary current , , Calculate the reactive power on the primary side , the amplitude of the negative sequence component of the primary current , zero-sequence current component of primary current .

[0007] Reactive power The calculation formula is as follows: , Amplitude of negative sequence component of primary current The calculation process is as follows: The instantaneous value of the primary current , , Decompose into positive-sequence component group and negative-sequence component group: , in, , , is the instantaneous value of the primary current, For the summation symbol, is the infinity symbol, is the current amplitude of the positive sequence component of the nth harmonic, is the phase angle of the positive sequence component of the nth harmonic, is the current amplitude of the negative sequence component of the nth harmonic, is the phase angle of the negative sequence component of the nth harmonic, n represents the harmonic order, when n is equal to 1, it represents the fundamental wave, sin is the sine trigonometric function, is the angular velocity and t is the time.

[0008] Primary current instantaneous value , , After 3s / 2r transformation, the d and q axis current components are obtained , : , in, , are the d and q axis current components, sin is the sine trigonometric function, cos is the cosine trigonometric function, is the angular velocity, t is the time, , , is the instantaneous value of the primary current, For the summation symbol, is the infinity symbol, is the current amplitude of the positive sequence component of the nth harmonic, is the current amplitude of the negative sequence component of the nth harmonic, is the phase angle of the positive sequence component of the nth harmonic, It is the phase angle of the negative sequence component of the nth harmonic, where n represents the harmonic order. When n is equal to 1, it represents the fundamental wave.

[0009] d, q axis current components , AC component , With DC component , , the AC component is filtered through a low-pass filter to obtain the DC component , : , in, , are the d and q axis current components , The DC component, sin is the sine trigonometric function, cos is the cosine trigonometric function, is the current amplitude of the fundamental negative sequence component, is the phase angle of the fundamental negative sequence component.

[0010] The DC component , After 2r / 3s transformation, the negative sequence component of the primary side fundamental current is obtained , , : , in, , , is the negative sequence component of the primary side fundamental current, sin is the sine trigonometric function, cos is the cosine trigonometric function, is the angular velocity, t is the time, , are the d and q axis current components , The DC component of is the current amplitude of the fundamental negative sequence component, is the phase angle of the fundamental negative sequence component.

[0011] Amplitude of negative sequence component of primary current The calculation formula is as follows: , , in, , is the negative sequence current component in the two-phase stationary coordinate system, , , is the negative sequence component of the primary side fundamental current, is the amplitude of the negative sequence component of the primary current.

[0012] Zero-sequence current component of primary current The calculation formula is as follows: , in, is the zero-sequence current component of the primary current, , , is the instantaneous value of primary current.

[0013] Step S3, based on the reactive power of the primary side , the amplitude of the negative sequence component of the primary current , zero-sequence current component of primary current Determine whether the secondary side of the phase-shifting transformer is short-circuited.

[0014] Step S4, the reactive power of the primary side , the amplitude of the negative sequence component of the primary current , zero-sequence current component of primary current Design the weight coefficient to determine whether the short circuit type is a three-phase short circuit, a single-phase short circuit or a short circuit to ground.

[0015] Collect reactive power of multiple groups of primary sides , voltage RMS , the amplitude of the negative sequence component of the primary current , the zero-sequence current component of the primary current , construct a sample set: , Among them, the first m sample points are three-phase short circuit type data, the sample points from m+1 to 2m are single-phase short circuit type data, the sample points from 2m+1 to 3m are ground short circuit type data, m is the number of three types of short circuit data collected, and D is the sample set; the three types of data are respectively brought into the corresponding short circuit type judgment method to solve three groups , , , and find the intersection of the three sets of solutions, and finally take a set within the intersection range. , , As the three-phase short-circuit weight coefficient , , .

[0016] The short circuit type determination method is as follows: , in, is the three-phase short-circuit weight coefficient, is the reactive power on the primary side, is the effective value of voltage, is the single-phase short-circuit weight coefficient, is the amplitude of the negative sequence component of the primary current, is the short-circuit weight coefficient to ground, is the zero-sequence current component of the primary current.

[0017] when When , it is judged that the short circuit type belongs to three-phase short circuit; when When the short circuit type is judged to be a single-phase short circuit; when The short circuit type is determined to be a short circuit to ground.

[0018] A short-circuit detection device for the secondary side of a phase-shifting transformer is used to implement the above-mentioned short-circuit detection method for the secondary side of a phase-shifting transformer, and includes: a voltage sampling module, a current sampling module, a short-circuit judgment module, a weight detection module, and a fault analysis module. Among them, the voltage sampling module is used to sample the primary side voltage of the phase-shifting transformer; the current sampling module is used to sample the primary side current of the phase-shifting transformer; the short-circuit judgment module is used to calculate the reactive power of the primary side, the negative sequence component of the primary side current, and the zero sequence current component of the primary side current according to the primary side voltage and the primary side current, and judge whether the secondary side of the phase-shifting transformer is short-circuited according to the reactive power of the primary side, the negative sequence component of the primary side current, and the zero sequence current component of the primary side current; the weight detection module is used to detect the short-circuit type under the short-circuit state of the secondary side; the fault analysis module is used to analyze the cause of the short-circuit.

[0019] Furthermore, the short-circuit judgment module includes a first calculation module, a phase angle calculation module, and a second calculation module. The first calculation module is used to calculate the reactive power of the primary side, the phase angle calculation module is used to calculate the voltage phase angle of the primary side, and the second calculation module is used to calculate the negative sequence component of the primary side current and the zero sequence current component of the primary side current.

[0020] The technical effect of the present invention is to quickly detect the secondary side short circuit problem of multiple secondary side phase-shifting transformers, determine the secondary side short circuit type, perform accurate fault analysis on the short circuit type, and improve the practical life of the phase-shifting transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A flow chart of a method for detecting short circuit on the secondary side of a phase-shifting transformer provided by the present invention; Figure 2 A schematic diagram of a phase-shifting transformer system provided by the present invention; Figure 3 A schematic diagram of a phase-shifting transformer secondary side short-circuit detection device provided by the present invention; Figure 4A schematic diagram of a short-circuit judgment module of a phase-shifting transformer secondary-side short-circuit detection device provided by the present invention. DETAILED DESCRIPTION

[0022] The following is only a preferred embodiment of the present invention. The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can understand the present invention. It should be pointed out that for those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims without departing from the principle of the present invention, all inventions and creations using the concept of the present invention are protected.

[0023] Figure 1 A flow chart of a method for detecting short circuit on the secondary side of a phase-shifting transformer provided by the present invention is shown in FIG. Figure 1 As shown, a method for detecting short circuit on the secondary side of a phase-shifting transformer comprises the following steps: Step S1: real-time sampling of primary side voltage , , and the instantaneous value of the primary current , , .

[0024] Step S2: According to the primary side voltage , , and the instantaneous value of the primary current , , Calculate the reactive power on the primary side , the amplitude of the negative sequence component of the primary current , zero-sequence current component of primary current .

[0025] Reactive power The calculation formula is as follows: , Amplitude of negative sequence component of primary current The calculation process is as follows: The instantaneous value of the primary current , , Decompose into positive-sequence component group and negative-sequence component group: , in, , , is the instantaneous value of the primary current, For the summation symbol, is the infinity symbol, is the current amplitude of the positive sequence component of the nth harmonic, is the phase angle of the positive sequence component of the nth harmonic, is the current amplitude of the negative sequence component of the nth harmonic, is the phase angle of the negative sequence component of the nth harmonic, n represents the harmonic order, when n is equal to 1, it represents the fundamental wave, sin is the sine trigonometric function, is the angular velocity and t is the time.

[0026] Primary current instantaneous value , , After 3s / 2r transformation, the d and q axis current components are obtained , : , in, , are the d and q axis current components, sin is the sine trigonometric function, cos is the cosine trigonometric function, is the angular velocity, t is the time, , , is the instantaneous value of the primary current, For the summation symbol, is the infinity symbol, is the current amplitude of the positive sequence component of the nth harmonic, is the current amplitude of the negative sequence component of the nth harmonic, is the phase angle of the positive sequence component of the nth harmonic, It is the phase angle of the negative sequence component of the nth harmonic, where n represents the harmonic order. When n is equal to 1, it represents the fundamental wave.

[0027] d, q axis current components , AC component , With DC component , , the AC component is filtered through a low-pass filter to obtain the DC component , : , in, , are the d and q axis current components , The DC component, sin is the sine trigonometric function, cos is the cosine trigonometric function, is the current amplitude of the fundamental negative sequence component, is the phase angle of the fundamental negative sequence component.

[0028] The DC component , After 2r / 3s transformation, the negative sequence component of the primary side fundamental current is obtained , , : , in, , , is the negative sequence component of the primary side fundamental current, sin is the sine trigonometric function, cos is the cosine trigonometric function, is the angular velocity, t is the time, , are the d and q axis current components , The DC component of is the current amplitude of the fundamental negative sequence component, is the phase angle of the fundamental negative sequence component.

[0029] Amplitude of negative sequence component of primary current The calculation formula is as follows: , , in, , is the negative sequence current component in the two-phase stationary coordinate system, , , is the negative sequence component of the primary side fundamental current, is the amplitude of the negative sequence component of the primary current.

[0030] Zero-sequence current component of primary current The calculation formula is as follows: , in, is the zero-sequence current component of the primary current, , , is the instantaneous value of primary current.

[0031] Step S3, based on the reactive power of the primary side , the amplitude of the negative sequence component of the primary current , zero-sequence current component of primary current Determine whether the secondary side of the phase-shifting transformer is short-circuited.

[0032] Step S4, the reactive power of the primary side , the amplitude of the negative sequence component of the primary current , zero-sequence current component of primary current Design the weight coefficient to determine whether the short circuit type is a three-phase short circuit, a single-phase short circuit or a short circuit to ground.

[0033] Collect reactive power of multiple groups of primary sides , voltage RMS , the amplitude of the negative sequence component of the primary current , the zero-sequence current component of the primary current , construct a sample set: , Among them, the first m sample points are three-phase short circuit type data, the sample points from m+1 to 2m are single-phase short circuit type data, the sample points from 2m+1 to 3m are ground short circuit type data, m is the number of three types of short circuit data collected, and D is the sample set; the three types of data are respectively brought into the corresponding short circuit type judgment method to solve three groups , , , and find the intersection of the three sets of solutions, and finally take a set within the intersection range. , , As the three-phase short-circuit weight coefficient , , .

[0034] The short circuit type determination method is as follows: , in, is the three-phase short-circuit weight coefficient, is the reactive power on the primary side, is the effective value of voltage, is the single-phase short-circuit weight coefficient, is the amplitude of the negative sequence component of the primary current, is the short-circuit weight coefficient to ground, is the zero-sequence current component of the primary current.

[0035] when When , it is judged that the short circuit type belongs to three-phase short circuit; when When the short circuit type is judged to be a single-phase short circuit; when The short circuit type is determined to be a short circuit to ground.

[0036] Figure 2 A schematic diagram of a phase-shifting transformer system provided by the present invention, such as Figure 2 As shown, the primary side of the phase-shifting transformer system is connected to the power grid, and the secondary side is connected to the power unit. The power units are connected in series and output three-phase electricity to the motor M.

[0037] Figure 3 A schematic diagram of a phase-shifting transformer secondary side short-circuit detection device provided by the present invention is shown in FIG. Figure 3 As shown, a short circuit detection device for the secondary side of a phase-shifting transformer includes: a voltage sampling module, a current sampling module, a short circuit judgment module, a weight detection module, and a fault analysis module. Among them, the voltage sampling module is used to sample the primary side voltage of the phase-shifting transformer; the current sampling module is used to sample the primary side current of the phase-shifting transformer; the short circuit judgment module is used to calculate the reactive power of the primary side, the negative sequence component of the primary side current, and the zero sequence current component of the primary side current according to the primary side voltage and the primary side current, and judge whether the secondary side of the phase-shifting transformer is short-circuited according to the reactive power of the primary side, the negative sequence component of the primary side current, and the zero sequence current component of the primary side current; the weight detection module is used to detect the short circuit type under the secondary side short circuit state; the fault analysis module is used to analyze the cause of the short circuit.

[0038] Figure 4 A schematic diagram of a short-circuit judgment module of a phase-shifting transformer secondary side short-circuit detection device provided by the present invention is shown in FIG. Figure 4 As shown, the short-circuit judgment module includes a first calculation module, a phase angle calculation module, and a second calculation module. The first calculation module is used to calculate the reactive power of the primary side, the phase angle calculation module is used to calculate the voltage phase angle of the primary side, and the second calculation module is used to calculate the negative sequence component of the primary side current and the zero sequence current component of the primary side current.

[0039] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A method for detecting short circuit on the secondary side of a phase-shifting transformer, characterized in that: The following steps are involved: Step S1: real-time sampling of primary side voltage , , and the instantaneous value of the primary current , , ; Step S2: According to the primary side voltage , , and the instantaneous value of the primary current , , Calculate the reactive power on the primary side , the amplitude of the negative sequence component of the primary current , zero-sequence current component of primary current ; The reactive power The calculation formula is as follows: ， The amplitude of the negative sequence component of the primary current The calculation process is as follows: The instantaneous value of the primary current , , Decompose into positive-sequence component group and negative-sequence component group: ， in, , , is the instantaneous value of the primary current, For the summation symbol, is the infinity symbol, is the current amplitude of the positive sequence component of the nth harmonic, is the phase angle of the positive sequence component of the nth harmonic, is the current amplitude of the negative sequence component of the nth harmonic, is the phase angle of the negative sequence component of the nth harmonic, n represents the harmonic order, when n is equal to 1, it represents the fundamental wave, sin is the sine trigonometric function, is the angular velocity, t is the time; Primary current instantaneous value , , After 3s / 2r transformation, the d and q axis current components are obtained , : , in, , are the d and q axis current components, sin is the sine trigonometric function, cos is the cosine trigonometric function, is the angular velocity, t is the time, , , is the instantaneous value of the primary current, For the summation symbol, is the infinity symbol, is the current amplitude of the positive sequence component of the nth harmonic, is the current amplitude of the negative sequence component of the nth harmonic, is the phase angle of the positive sequence component of the nth harmonic, is the phase angle of the negative sequence component of the nth harmonic, n represents the harmonic order, and when n is equal to 1, it represents the fundamental wave; d, q axis current components , AC component , With DC component , , the AC component is filtered through a low-pass filter to obtain the DC component , : ， in, , are the d and q axis current components , The DC component, sin is the sine trigonometric function, cos is the cosine trigonometric function, is the current amplitude of the fundamental negative sequence component, is the phase angle of the fundamental negative sequence component; The DC component , After 2r / 3s transformation, the negative sequence component of the primary side fundamental current is obtained , , : ， in, , , is the negative sequence component of the primary side fundamental current, sin is the sine trigonometric function, cos is the cosine trigonometric function, is the angular velocity, t is the time, , are the d and q axis current components , The DC component of is the current amplitude of the fundamental negative sequence component, is the phase angle of the fundamental negative sequence component; Amplitude of negative sequence component of primary current The calculation formula is as follows: ， ， in, , is the negative sequence current component in the two-phase stationary coordinate system, , , is the negative sequence component of the primary side fundamental current, is the amplitude of the negative sequence component of the primary current; The zero-sequence current component of the primary current The calculation formula is as follows: ， in, is the zero-sequence current component of the primary current, , , is the instantaneous value of the primary current; Step S3, based on the reactive power of the primary side , the amplitude of the negative sequence component of the primary current , zero-sequence current component of primary current Determine whether the secondary side of the phase-shifting transformer is short-circuited; Step S4, the reactive power of the primary side , the amplitude of the negative sequence component of the primary current , zero-sequence current component of primary current Design weight coefficients to determine whether the short circuit type is three-phase short circuit, single-phase short circuit or short circuit to ground; Collect reactive power of multiple groups of primary sides , voltage RMS , the amplitude of the negative sequence component of the primary current , the zero-sequence current component of the primary current , construct a sample set: ， Among them, the first m sample points are three-phase short circuit type data, the sample points from m+1 to 2m are single-phase short circuit type data, the sample points from 2m+1 to 3m are ground short circuit type data, m is the number of three types of short circuit data collected, and D is the sample set; the three types of data are respectively brought into the corresponding short circuit type judgment method to solve three groups , , , and find the intersection of the three sets of solutions, and finally take a set within the intersection range. , , As the three-phase short-circuit weight coefficient , , ; The short circuit type determination method is as follows: ， in, is the three-phase short-circuit weight coefficient, is the reactive power on the primary side, is the effective value of voltage, is the single-phase short-circuit weight coefficient, is the amplitude of the negative sequence component of the primary current, is the short-circuit weight coefficient to ground, is the zero-sequence current component of the primary current; when When , it is judged that the short circuit type belongs to three-phase short circuit; when When the short circuit type is judged to be a single-phase short circuit; when The short circuit type is determined to be a short circuit to ground.

2. A phase-shifting transformer secondary side short-circuit detection device, used to implement a phase-shifting transformer secondary side short-circuit detection method according to claim 1, characterized in that: include: A voltage sampling module, a current sampling module, a short-circuit judgment module, a weight detection module, and a fault analysis module; wherein the voltage sampling module is used to sample the primary-side voltage of the phase-shifting transformer; the current sampling module is used to sample the primary-side current of the phase-shifting transformer; the short-circuit judgment module is used to calculate the reactive power of the primary side, the negative-sequence component of the primary-side current, and the zero-sequence current component of the primary-side current according to the primary-side voltage and the primary-side current, and to judge whether the secondary-side short circuit of the phase-shifting transformer is short-circuited according to the reactive power of the primary side, the negative-sequence component of the primary-side current, and the zero-sequence current component of the primary-side current; the weight detection module is used to detect the short-circuit type under the secondary-side short-circuit state; The fault analysis module is used to analyze the cause of the short circuit.

3. A phase-shifting transformer secondary side short-circuit detection device according to claim 2, characterized in that: The short-circuit judgment module includes a first calculation module, a phase angle calculation module, and a second calculation module; the first calculation module is used to calculate the reactive power of the primary side, the phase angle calculation module is used to calculate the voltage phase angle of the primary side, and the second calculation module is used to calculate the negative sequence component of the primary side current and the zero sequence current component of the primary side current.

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