Method and system for protecting open-phase imbalance of rotor winding of variable-speed pumped storage unit

Abstract

The invention discloses an open-phase imbalance protection method and system for a rotor winding of a variable-speed pumped storage unit. The method comprises the following steps: acquiring a sampling value of three-phase current of the rotor winding of the variable-speed pumped storage unit; the amplitude of the three-phase current sampling value is obtained, and then the phase angle of the three-phase current sampling value is obtained; forming a sampling value instantaneous unbalance degree criterion based on the phase angle of the three-phase current sampling value, and judging the action behavior of the sampling value instantaneous unbalance degree criterion; calculating a heat accumulation value of the three-phase current to form an amplitude ratio criterion, and judging an action behavior of the amplitude ratio criterion; and judging the action behavior of rotor winding open-phase unbalance protection according to the judgment result of the sampling value instantaneous unbalance degree criterion and the amplitude ratio criterion. According to the method, the open-phase and unbalanced faults of the rotor winding can be quickly identified, and meanwhile, the method also serves as backup protection for asymmetric inter-phase short circuit and turn-to-turn short circuit of the rotor winding, and guarantees are provided for stable operation of a variable-speed pumped storage unit.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection for electric power systems, and more specifically, to a method and system for protecting rotor winding unbalance of a variable-speed pumped storage unit from phase failure. Background Art

[0002] The excitation system of the fixed-speed pumped storage unit adopts DC excitation, and is usually equipped with ping-pong and injection-type rotor grounding protection to respond to the grounding fault of the rotor winding. The excitation system of the doubly fed variable-speed pumped storage unit adopts three-phase AC excitation, and its rotor winding protection configuration is very different from that of the fixed-speed pumped storage unit. It should be able to respond to rotor winding phase failure, grounding, phase-to-phase short circuit and turn-to-turn short circuit faults. Since the variable-speed pumped storage unit adopts a three-phase AC excitation structure, the probability of three phases being disconnected at the same time is extremely small, that is, the probability of total demagnetization is extremely small. It is often easy to cause phase-break unbalance faults caused by rotating devices, such as single-phase brush slip rings or slip ring rotor leads, poor contact, falling off, and rotor winding welding. When a phase-break unbalance fault occurs, it will cause huge mechanical vibration and electrical oscillation, endangering the safety of the unit. Therefore, it is necessary to install rotor winding phase-break unbalance protection.

[0003] When the unit is operating normally, the AC excitation operates at an extremely low frequency of -5Hz to 5Hz. The conventional power frequency protection algorithm is no longer applicable, and the integral algorithm requires a longer calculation data window. How to implement a short data window fast algorithm for rotor winding phase-break unbalance protection is a difficult problem. Accurate acquisition of analog signals is a prerequisite for the implementation of relay protection. Traditional current transformers cannot accurately collect extremely low frequency signals. Therefore, accurate acquisition of rotor winding low-frequency current signals is another difficult problem in realizing rotor winding phase-break unbalance protection. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a method and system for protecting the rotor winding of a variable-speed pumped storage unit from phase loss and unbalance, which can quickly identify rotor winding phase loss and unbalance faults, and also serve as backup protection for asymmetric phase-to-phase short circuit and turn-to-turn short circuit of the rotor winding, thereby providing guarantee for the stable operation of the variable-speed pumped storage unit.

[0005] The present invention adopts the following technical solution.

[0006] The present invention discloses a method for protecting rotor windings of a variable speed pumped storage unit from phase loss and imbalance, comprising:

[0007] Step 1, obtaining the sampled values ​​of the three-phase current of the rotor winding of the variable speed pumped storage unit;

[0008] Step 2, obtaining the amplitude of the three-phase current sampling value, and then obtaining the phase angle of the three-phase current sampling value;

[0009] Step 3, forming a sampling value instantaneous unbalance degree criterion based on the phase angles of the three-phase current sampling values, and determining the action behavior of the sampling value instantaneous unbalance degree criterion;

[0010] Step 4, calculating the heat accumulation value of the three-phase current, thereby forming an amplitude ratio criterion, and determining the action behavior of the amplitude ratio criterion;

[0011] Step 5: Determine the action behavior of the rotor winding open-phase unbalance protection according to the judgment results of the sampling value instantaneous unbalance degree judgment criterion and the amplitude ratio judgment criterion.

[0012] More preferably,

[0013] In step 1, the method for obtaining the sampled values ​​of the three-phase current of the rotor winding of the variable speed pumped storage unit is:

[0014] The rotor winding current signal is collected by installing a flexible optical current sensor or a Hall current sensor, and the current sensor signal is connected to the protection device through an optical fiber or a cable to obtain the sampling value of the three-phase current.

[0015] More preferably,

[0016] In step 2, the amplitude I of the three-phase current sampling value is obtained according to the following formula: M (t):

[0017]

[0018] Where t is the current sampling point; i a (t) is the sampling value of the current of phase A at the current sampling point; i b (t) is the sampling value of the current of phase B at the current sampling point; i c (t) is the sampling value of the C phase current at the current sampling point.

[0019] More preferably,

[0020] In step 2, the phase angle of the three-phase current sampling value is obtained according to the following formula:

[0021]

[0022] Among them, θ a (t) is the phase angle of the A phase sample value at the current sampling point; θ b (t) is the phase angle of the B phase sampling value at the current sampling point; θ c (t) is the phase angle of the C phase sampling value at the current sampling point;

[0023] The obtained θ a (t),θ b (t),θ c The value range of (t) is converted from [-90°, 90°] to [0, 360°].

[0024] More preferably,

[0025] The value range of the current sampling value phase angle is converted from [-90°, 90°] to [0, 360°] in the following way:

[0026] Compare the current sampling value with the previous sampling value. When it is determined to be an upward trend, if the current sampling value is positive, the angle of the current sampling value remains unchanged, otherwise the angle of the current sampling value is increased by 360°; when it is determined to be a downward trend, the angle of the sampling value is 180° minus the angle of the current sampling value.

[0027] More preferably,

[0028] In step 3, the instantaneous imbalance criterion equation of the sampling value is as follows:

[0029]

[0030] Where: is the constant value of unbalance, I QDset is the starting current setting, I max is the maximum value among the three-phase currents, Abs[θ a (t)-θ b (t)] means taking the difference of the phase angles of the sampling values ​​of phases A and B and taking the absolute value;

[0031] Abs[θ b (t)-θ c (t)] means taking the difference of the phase angles of the B and C phase sampling values ​​and taking the absolute value; Abs[θ c (t)-θ a (t)] means to make a difference between the phase angles of the C and A phase sampling values ​​and take the absolute value; X%120 means to take the remainder of X with respect to 120;

[0032] When the maximum value of the three-phase current is greater than the set starting current value, and the phase angle difference between any two-phase current is greater than the unbalanced value, after the set delay, it is determined that the sampling value instantaneous unbalanced degree judgment criterion is activated;

[0033] When the maximum value of the three-phase current is not greater than the set starting current value, or the angle difference between any two-phase currents is not greater than the imbalance value, it is determined that the instantaneous imbalance criterion of the sampling value is not actuated and the protection returns.

[0034] More preferably,

[0035] The starting current constant is set to 0.3 to 1 times the rated current of the rotor winding.

[0036] More preferably,

[0037] In step 4, the thermal accumulation values ​​Accu(t), Bccu(t), and Cccu(t) of the three-phase currents A, B, and C are calculated according to the following formula;

[0038]

[0039] Wherein, Accu(t) is the thermal accumulation value of the A-phase current corresponding to the current sampling point; Accu(t-1) is the thermal accumulation value of the A-phase current at the moment corresponding to the previous sampling point; Bccu(t) is the thermal accumulation value of the B-phase current corresponding to the current sampling point; Bccu(t-1) is the thermal accumulation value of the B-phase current corresponding to the previous sampling point; Cccu(t) is the thermal accumulation value of the C-phase current corresponding to the current sampling point; Cccu(t-1) is the thermal accumulation value of the C-phase current corresponding to the previous sampling point; Samp A (t) is the sampling value of phase A current at time t; Samp B (t) is the sampling value of phase B current at time t; Samp C (t) is the sampling value of the C phase current at the tth moment, Δt is the sampling interval, and τ is the time constant.

[0040] More preferably,

[0041] In step 4, the amplitude ratio criterion formula is as follows:

[0042]

[0043] In the formula, Hccu max Hccu is the maximum value of the three-phase heat accumulation value; min It is the minimum value among the three-phase heat accumulation values; I Phset is the hot start setting value of the amplitude ratio criterion, k phSet is the value of the amplitude ratio coefficient;

[0044] When the maximum value of the three-phase heat accumulation value is greater than the amplitude ratio criterion hot start setting, and the ratio of the maximum value to the minimum value of the heat accumulation is greater than the amplitude ratio coefficient setting, after the set delay, it is determined that the amplitude ratio criterion is in action;

[0045] When the maximum value of the three-phase heat accumulation value is less than the amplitude ratio criterion hot start setting, or the ratio of the maximum and minimum heat accumulation values ​​is not greater than the amplitude ratio coefficient setting, it is determined that the amplitude ratio criterion is not actuated and the protection returns.

[0046] More preferably,

[0047] In step 5, the action behavior of the rotor winding phase failure unbalance protection is determined according to the judgment results of the sampling value instantaneous unbalance degree criterion and the amplitude ratio criterion:

[0048] When the sampling value instantaneous unbalance judgment criterion is activated, or the amplitude ratio judgment criterion is activated, it is determined that the rotor winding phase failure unbalance protection is activated. After the set delay, the rotor winding phase failure unbalance protection is activated;

[0049] When the instantaneous unbalance criterion of the sampling value does not work and the amplitude ratio criterion does not work, it is determined that the rotor winding phase failure unbalance protection returns.

[0050] On the other hand, the present invention discloses a variable speed pumped storage unit rotor winding phase-out unbalance protection system based on a variable speed pumped storage unit rotor winding phase-out unbalance protection method, comprising a current sampling module, a phase angle solving module, an instantaneous unbalance degree criterion building module, an amplitude ratio criterion building module and an unbalance protection action behavior determination module:

[0051] The current sampling module obtains the sampling values ​​of the three-phase current of the rotor winding of the variable speed pumped storage unit;

[0052] The phase angle solving module obtains the amplitude of the three-phase current sampling value, and then obtains the phase angle of the three-phase current sampling value;

[0053] The instantaneous unbalance criterion module forms a sampling value instantaneous unbalance criterion based on the phase angles of the three-phase current sampling values, and determines the action behavior of the sampling value instantaneous unbalance criterion;

[0054] The amplitude ratio criterion module calculates the heat accumulation value of the three-phase current, thereby forming an amplitude ratio criterion, and determines the action behavior of the amplitude ratio criterion;

[0055] The unbalance protection action behavior module determines the action behavior of the rotor winding phase failure unbalance protection according to the judgment results of the sampling value instantaneous unbalance degree judgment criterion and the amplitude ratio judgment criterion.

[0056] On the other hand, the present application discloses an electronic device, including a processor and a storage medium; the characteristics are:

[0057] The storage medium is used to store instructions;

[0058] The processor is used to operate according to the instruction to execute the above-mentioned variable speed pumped storage unit rotor winding phase-out unbalance protection method.

[0059] The present application also discloses a computer-readable storage medium having a computer program stored thereon, wherein the program, when executed by a processor, implements the variable-speed pumped storage unit rotor winding phase-loss unbalance protection method.

[0060] The beneficial effect of the present invention is that, compared with the prior art, the present invention discloses a method and system for protecting the rotor winding of a variable speed pumped storage unit from phase failure and imbalance, the method comprising: obtaining the sampling value of the three-phase current of the rotor winding of the variable speed pumped storage unit; obtaining the amplitude of the three-phase current sampling value, and then obtaining the phase angle of the three-phase current sampling value; forming a sampling value instantaneous imbalance criterion based on the phase angle of the three-phase current sampling value, and judging the action behavior of the sampling value instantaneous imbalance criterion; calculating the heat accumulation value of the three-phase current, and then forming an amplitude ratio criterion, and judging the action behavior of the amplitude ratio criterion; judging the action behavior of the rotor winding phase failure and imbalance protection according to the judgment results of the sampling value instantaneous imbalance criterion and the amplitude ratio criterion. The present invention can quickly identify the rotor winding phase failure and imbalance faults, and also serves as a backup protection for the asymmetric phase-to-phase short circuit and turn-to-turn short circuit of the rotor winding, providing guarantee for the stable operation of the variable speed pumped storage unit.

[0061] The method of the present invention can quickly identify rotor winding phase failure and unbalance faults, and also serves as backup protection for asymmetric phase-to-phase short circuit and turn-to-turn short circuit of the rotor winding, providing guarantee for the stable operation of the variable speed pumped storage unit; a fast sampling value amplitude and phase angle calculation algorithm is adopted, and the protection is not affected by frequency changes, the action speed is fast, and the speed and sensitivity of the protection are improved; a method for connecting a rotor winding low-frequency analog quantity to a protection device is proposed. Specifically, the present invention adopts a low-frequency sensor for signal acquisition, and uses a set amplitude and phase angle calculation algorithm. These algorithms are not affected by frequency and are frequency-independent algorithms, which solves the problem that extremely low frequency signals are difficult to accurately measure. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 The invention is a schematic flow chart of the steps of a method for protecting the rotor winding of a variable speed pumped storage unit from phase failure and unbalance;

[0063] Figure 2 It is a schematic diagram of the arrangement of CT for the phase-break unbalance protection of the rotor winding of the variable speed pumped storage unit in the present invention;

[0064] Figure 3 It is a logical schematic diagram of the inter-turn protection of the excitation winding in the present invention. DETAILED DESCRIPTION

[0065] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0066] The present invention proposes a method for protecting the rotor winding of a variable speed pumped storage unit from phase failure and imbalance. Figure 1 Said method comprises the following steps:

[0067] Step 1, obtaining the sampled values ​​of the three-phase current of the rotor winding of the variable speed pumped storage unit;

[0068] The method for obtaining the sampling value of the three-phase current of the rotor winding of the variable speed pumped storage unit is:

[0069] The rotor winding current signal is collected by installing a flexible optical current sensor or a Hall current sensor, and the current sensor signal is connected to the protection device through an optical fiber or a cable to obtain the sampling value of the three-phase current.

[0070] Step 2, obtaining the amplitude of the three-phase current sampling value, and then obtaining the phase angle of the three-phase current sampling value;

[0071] The amplitude I of the three-phase current sampling value is obtained according to the following formula M (t):

[0072]

[0073] Where t is the current sampling point; i a (t) is the sampling value of the current of phase A at the current sampling point; i b (t) is the sampling value of the current of phase B at the current sampling point; i c (t) is the sampling value of the C phase current at the current sampling point.

[0074] The phase angle of the three-phase current sampling value is obtained according to the following formula:

[0075]

[0076] Among them, θ a (t) is the phase angle of the A phase sample value at the current sampling point; θ b (t) is the phase angle of the B phase sampling value at the current sampling point; θ c (t) is the phase angle of the C phase sampling value at the current sampling point; where sin -1 x is the inverse sine function;

[0077] The obtained θ a (t),θ b (t),θ c The value range of (t) is converted from [-90°, 90°] to [0, 360°].

[0078] The value range of the current sampling value phase angle is converted from [-90°, 90°] to [0, 360°] in the following way:

[0079] Compare the current sampling value with the previous sampling value. When it is determined to be an upward trend, if the current sampling value is positive, the angle of the current sampling value remains unchanged, otherwise the angle of the current sampling value is increased by 360°; when it is determined to be a downward trend, the angle of the sampling value is 180° minus the angle of the current sampling value. When the current sampling value is greater than the previous sampling value, it is determined to be an upward trend; when the current sampling value is less than the previous sampling value, it is determined to be a downward trend;

[0080] Step 3, forming a sampling value instantaneous unbalance degree criterion based on the phase angles of the three-phase current sampling values, and determining the action behavior of the sampling value instantaneous unbalance degree criterion;

[0081] The instantaneous imbalance criterion equation of the sampling value is as follows:

[0082]

[0083] Where: is the constant value of unbalance, I QDset I is the starting current constant, which is set to 0.3 to 1 times the rated current of the rotor winding. max is the maximum value among the three-phase currents, Abs[θ a (t)-θ b (t)] means taking the difference of the phase angles of the sampling values ​​of phases A and B and taking the absolute value; Abs[θ b (t)-θ c (t)] means taking the difference of the phase angles of the B and C phase sampling values ​​and taking the absolute value; Abs[θ c (t)-θ a (t)] means to make a difference between the phase angles of the C and A phase sampling values ​​and take the absolute value; X%120 means to take the remainder of X to 120;

[0084] When the maximum value of the three-phase current is greater than the set starting current value, and the phase angle difference between any two-phase current is greater than the unbalanced value, after the set delay, it is determined that the sampling value instantaneous unbalanced degree judgment criterion is activated;

[0085] When the maximum value of the three-phase current is not greater than the set starting current value, or the angle difference between any two-phase currents is not greater than the imbalance value, it is determined that the instantaneous imbalance criterion of the sampling value is not actuated and the protection returns.

[0086] Step 4, calculating the heat accumulation value of the three-phase current, thereby forming an amplitude ratio criterion, and determining the action behavior of the amplitude ratio criterion;

[0087] The thermal accumulation values ​​Accu(t), Bccu(t), and Cccu(t) of the three-phase currents A, B, and C are calculated according to the following formula;

[0088]

[0089] Wherein, Accu(t) is the thermal accumulation value of the A-phase current corresponding to the current sampling point; Accu(t-1) is the thermal accumulation value of the A-phase current at the moment corresponding to the previous sampling point; wherein, when t=1, that is, when the current sampling point is the initial sampling point, Accu(t-1)=0 is set; Bccu(t) is the thermal accumulation value of the B-phase current corresponding to the current sampling point; Bccu(t-1) is the thermal accumulation value of the B-phase current corresponding to the previous sampling point; wherein, when t=1, that is, when the current sampling point is the initial sampling point, Bccu(t-1)=0 is set; Cccu(t) is the thermal accumulation value of the C-phase current corresponding to the current sampling point; Cccu(t-1) is the thermal accumulation value of the C-phase current corresponding to the previous sampling point; wherein, when t=1, that is, when the current sampling point is the initial sampling point, Cccu(t-1)=0 is set; Samp A (t) is the sampling value of phase A current at time t; Samp B (t) is the sampling value of phase B current at time t; Samp C (t) is the sampling value of the C phase current at the tth moment, Δt is the sampling interval, τ is the time constant, and its preferred value range is 0.5~10, and its unit is second; in practice, the time constant can be adjusted by adjusting the value of τ to meet different protection calculation accuracy and time accuracy requirements.

[0090] The amplitude ratio criterion formula is as follows:

[0091]

[0092] In the formula, Hccu max Hccu is the maximum value of the three-phase heat accumulation value; min It is the minimum value among the three-phase heat accumulation values; I Phset is the hot start setting value of the amplitude ratio criterion, k phSet is the value of the amplitude ratio coefficient;

[0093] Among them Hccu max =max[Accu(t),Bccu(t),Cccu(t)];

[0094] Among them, max[·] means to find the maximum value in the brackets;

[0095] Hccu min =min[Accu(t),Bccu(t),Cccu(t)];

[0096] Among them, min[·] means to find the minimum value in the brackets;

[0097] When the maximum value of the three-phase heat accumulation value is greater than the amplitude ratio criterion hot start setting, and the ratio of the maximum value to the minimum value of the heat accumulation is greater than the amplitude ratio coefficient setting, after the set delay, it is determined that the amplitude ratio criterion is in action;

[0098] When the maximum value of the three-phase heat accumulation value is less than the amplitude ratio criterion hot start setting, or the ratio of the maximum and minimum heat accumulation values ​​is not greater than the amplitude ratio coefficient setting, it is determined that the amplitude ratio criterion is not actuated and the protection returns.

[0099] Step 5: Determine the action behavior of the rotor winding open-phase unbalance protection according to the judgment results of the sampling value instantaneous unbalance degree judgment criterion and the amplitude ratio judgment criterion.

[0100] According to the results of the instantaneous unbalance criterion and the amplitude ratio criterion of the sampling value, the action behavior of the rotor winding phase failure unbalance protection is determined:

[0101] When the sampling value instantaneous unbalance judgment criterion is activated, or the amplitude ratio judgment criterion is activated, it is determined that the rotor winding phase failure unbalance protection is activated. After the set delay, the rotor winding phase failure unbalance protection is activated;

[0102] When the instantaneous unbalance criterion of the sampling value does not work and the amplitude ratio criterion does not work, it is determined that the rotor winding phase failure unbalance protection returns.

[0103] Embodiment 1:

[0104] A method for protecting the rotor winding of a variable speed pumped storage unit from phase failure and unbalance. Figure 1 Said method comprises the following steps:

[0105] Step 1: Obtain the sampled values ​​of the three-phase current of the rotor winding of the variable speed pumped storage unit, which is specifically implemented as follows:

[0106] like Figure 2 As shown, a flexible optical current sensor or a Hall current sensor is installed on each phase winding of the rotor on the AC exciter side, denoted as CT1. CT1 is used to collect the rotor winding current signal, and the current sensor signal is connected to the protection device through optical fiber or cable to obtain the sampling value of the three-phase current.

[0107] Step 2, obtain the amplitude of the three-phase current sampling value, and then obtain the phase angle of the three-phase current sampling value, which is specifically implemented as follows:

[0108] The sampled values ​​of the three-phase current obtained in step 1 are defined as i a (n), i b (n), i c (n), n = 0, 1, 2, ...;

[0109] The amplitude I corresponding to the three-phase current sampling value is calculated by the following formula M (t):

[0110]

[0111] Where: t is the current sampling point; ia (t) is the sampling value of the current of phase A at the current sampling point; i b (t) is the sampling value of the current of phase B at the current sampling point; i c (t) is the sampled value of the C-phase current at the current sampling point. Preferably, the sampling buffer area is 64MB.

[0112] Then the phase angle of the three-phase current sampling value is obtained, the steps are as follows:

[0113] According to the instantaneous value angle calculation algorithm, the angle of each phase current sampling value is obtained:

[0114]

[0115] Among them, θ a (t) is the phase angle of the A phase sample value at the current sampling point; θ b (t) is the phase angle of the B phase sampling value at the current sampling point; θ c (t) is the phase angle of the C phase sampling value at the current sampling point;

[0116] The obtained θ a (t),θ b (t),θ c The value range of (t) is converted from [-90°, 90°] to [0, 360°].

[0117] The value range of the current sampling value phase angle is converted from [-90°, 90°] to [0, 360°] in the following way:

[0118] Compare the current sampling value with the previous sampling value. When it is determined to be an upward trend, if the current sampling value is positive, the angle of the current sampling value remains unchanged, otherwise the angle of the current sampling value is increased by 360°; when it is determined to be a downward trend, the angle of the sampling value is 180° minus the angle of the current sampling value.

[0119] Step 3, based on the phase angles of the three-phase current sampling values, a sampling value instantaneous unbalance degree criterion is formed, and the action behavior of the sampling value instantaneous unbalance degree criterion is determined, which is specifically implemented as follows;

[0120] The instantaneous imbalance criterion equation of the sampling value is as follows:

[0121]

[0122] Where: is the value of the unbalance degree, the preferred value range is 10-20, and its unit is °; I QDset I is the starting current constant, and its preferred value range is 0.3 to 1 times the rated current of the rotor winding; max is the maximum value of the three-phase current, Abs[θ a (t)-θb (t)] means to make the difference between the angles of the sampling values ​​of phase A and phase B and take the absolute value Abs[θ b (t)-θ c (t)] means taking the difference of the phase angles of the B and C phase sampling values ​​and taking the absolute value; Abs[θ c (t)-θ a (t)] means to make a difference between the phase angles of the C and A phase sampling values ​​and take the absolute value; X%120 means to take the remainder of X with respect to 120 degrees.

[0123] The action logic of the sampling value instantaneous imbalance criterion is:

[0124] When the maximum value of the three-phase current is greater than the set starting current value, and the phase angle difference between any two-phase current is greater than the unbalanced value, after the set delay, it is determined that the sampling value instantaneous unbalanced degree judgment criterion is activated;

[0125] When the maximum value of the three-phase current is not greater than the set starting current value, or the angle difference between any two-phase currents is less than the imbalance value, it is determined that the instantaneous imbalance criterion of the sampling value is not actuated and the protection returns.

[0126] Step 4, calculate the heat accumulation value of the three-phase current, then form the amplitude ratio criterion, and judge the action behavior of the amplitude ratio criterion, which is specifically implemented as follows:

[0127] The thermal accumulation values ​​Accu(t), Bccu(t), and Cccu(t) of the three-phase currents A, B, and C are calculated according to the following formula;

[0128]

[0129] Wherein, Accu(t) is the thermal accumulation value of the A-phase current corresponding to the current sampling point; Accu(t-1) is the thermal accumulation value of the A-phase current at the moment corresponding to the previous sampling point; Bccu(t) is the thermal accumulation value of the B-phase current corresponding to the current sampling point; Bccu(t-1) is the thermal accumulation value of the B-phase current corresponding to the previous sampling point; Cccu(t) is the thermal accumulation value of the C-phase current corresponding to the current sampling point; Cccu(t-1) is the thermal accumulation value of the C-phase current corresponding to the previous sampling point; Samp A (t) is the sampling value of phase A current at time t; Samp B (t) is the sampling value of phase B current at time t; Samp C (t) is the sampling value of the C phase current at the tth moment, Δt is the sampling interval, and τ is the time constant.

[0130] The amplitude ratio criterion formula is as follows:

[0131]

[0132] In the formula, Hccumax Hccu is the maximum value of the three-phase heat accumulation value; min It is the minimum value among the three-phase heat accumulation values; I Phset k is the starting current constant based on the amplitude ratio criterion, and its preferred value range is 0.3 to 1 times the rated current of the rotor winding; phSet is the constant value of the amplitude ratio coefficient, and its preferred value range is 1.5 to 10.

[0133] The action logic of the amplitude ratio criterion is:

[0134] When the maximum value of the three-phase heat accumulation value is greater than the amplitude ratio criterion hot start setting, and the ratio of the maximum value to the minimum value of the heat accumulation is greater than the amplitude ratio coefficient setting, after the set delay, it is determined that the amplitude ratio criterion is in action;

[0135] When the maximum value of the three-phase heat accumulation value is less than the amplitude ratio criterion hot start setting, or the ratio of the maximum and minimum heat accumulation values ​​is not greater than the amplitude ratio coefficient setting, it is determined that the amplitude ratio criterion is not actuated and the protection returns.

[0136] Step 5: According to the judgment results of the sampling value instantaneous imbalance degree criterion and the amplitude ratio criterion, the action behavior of the rotor winding phase unbalance protection is determined, such as Figure 3 As shown, the specific implementation is as follows:

[0137] When the sampling value instantaneous unbalance judgment criterion is activated, or the amplitude ratio judgment criterion is activated, it is determined that the rotor winding phase failure unbalance protection is activated. After the set delay, the rotor winding phase failure unbalance protection is activated;

[0138] When the instantaneous unbalance criterion of the sampling value does not work and the amplitude ratio criterion does not work, it is determined that the rotor winding phase failure unbalance protection returns.

[0139] The present application also discloses a variable speed pumped storage unit rotor winding phase-out unbalance protection system based on a variable speed pumped storage unit rotor winding phase-out unbalance protection method, comprising a current sampling module, a phase angle solving module, an instantaneous unbalance degree criterion building module, an amplitude ratio criterion building module and an unbalance protection action behavior determination module:

[0140] The current sampling module obtains the sampling value of the three-phase current of the rotor winding of the variable speed pumped storage unit;

[0141] The phase angle solving module obtains the amplitude of the three-phase current sampling value, and then obtains the phase angle of the three-phase current sampling value;

[0142] The instantaneous unbalance criterion module forms a sampling value instantaneous unbalance criterion based on the phase angles of the three-phase current sampling values, and determines the action behavior of the sampling value instantaneous unbalance criterion;

[0143] The amplitude ratio criterion module calculates the heat accumulation value of the three-phase current, thereby forming an amplitude ratio criterion, and determines the action behavior of the amplitude ratio criterion;

[0144] The unbalance protection action behavior module determines the action behavior of the rotor winding phase failure unbalance protection according to the judgment results of the sampling value instantaneous unbalance degree judgment criterion and the amplitude ratio judgment criterion.

[0145] The beneficial effects of the present invention are that, compared with the prior art, a method and system for protecting the rotor winding of a variable-speed pumped storage unit from phase loss and imbalance is provided, which can quickly identify rotor winding phase loss and imbalance faults, and also serve as backup protection for asymmetric phase-to-phase short circuit and turn-to-turn short circuit of the rotor winding, providing guarantee for the stable operation of the variable-speed pumped storage unit; a fast sampling value amplitude and phase angle calculation algorithm is adopted, and the protection is not affected by frequency changes, and the action speed is fast, thereby improving the speed and sensitivity of the protection; a method for connecting a rotor winding low-frequency analog quantity to a protection device is proposed. Specifically, the present invention adopts a low-frequency sensor for signal acquisition, and uses a set amplitude and phase angle calculation algorithm. These algorithms are not affected by frequency and are frequency-independent algorithms, which solves the problem that extremely low-frequency signals are difficult to accurately measure.

[0146] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0147] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0148] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0149] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0150] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A variable speed pumped storage unit rotor winding phase failure unbalance protection method, characterized in that: The steps include: Step 1, obtaining the sampled values ​​of the three-phase current of the rotor winding of the variable speed pumped storage unit; Step 2, obtaining the amplitude of the three-phase current sampling value, and then obtaining the phase angle of the three-phase current sampling value; Step 3, forming a sampling value instantaneous unbalance degree criterion based on the phase angles of the three-phase current sampling values, and determining the action behavior of the sampling value instantaneous unbalance degree criterion; Step 4, calculating the heat accumulation value of the three-phase current, thereby forming an amplitude ratio criterion, and determining the action behavior of the amplitude ratio criterion; Step 5: Determine the action behavior of the rotor winding open-phase unbalance protection according to the judgment results of the sampling value instantaneous unbalance degree judgment criterion and the amplitude ratio judgment criterion.

2. The variable speed pumped storage unit rotor winding unbalance protection method according to claim 1 is characterized in that: In step 1, the method for obtaining the sampled values ​​of the three-phase current of the rotor winding of the variable speed pumped storage unit is: The rotor winding current signal is collected by installing a flexible optical current sensor or a Hall current sensor, and the current sensor signal is connected to the protection device through an optical fiber or a cable to obtain the sampling value of the three-phase current.

3. The variable speed pumped storage unit rotor winding unbalance protection method according to claim 1 is characterized in that: In step 2, the amplitude I of the three-phase current sampling value is obtained according to the following formula: M (t): Where t is the current sampling point; i a (t) is the sampling value of the current of phase A at the current sampling point; i b (t) is the sampling value of the current of phase B at the current sampling point; i c (t) is the sampling value of the C phase current at the current sampling point.

4. The variable speed pumped storage unit rotor winding unbalance protection method according to claim 1 or 3, characterized in that: In step 2, the phase angle of the three-phase current sampling value is obtained according to the following formula: Among them, θ a (t) is the phase angle of the A phase sampling value at the current sampling point; θ b (t) is the phase angle of the B phase sampling value at the current sampling point; θ c (t) is the phase angle of the C phase sampling value at the current sampling point; The obtained θ a (t),θ b (t),θ c The value range of (t) is converted from [-90°, 90°] to [0, 360°].

5. The variable speed pumped storage unit rotor winding unbalance protection method according to claim 4 is characterized in that: The value range of the current sampling value phase angle is converted from [-90°, 90°] to [0, 360°] in the following way: Compare the current sampling value with the previous sampling value. When it is determined to be an upward trend, if the current sampling value is positive, the angle of the current sampling value remains unchanged, otherwise the angle of the current sampling value is increased by 360°; when it is determined to be a downward trend, the angle of the sampling value is 180° minus the angle of the current sampling value.

6. The variable speed pumped storage unit rotor winding unbalance protection method according to claim 1, characterized in that: In step 3, the instantaneous imbalance criterion equation of the sampling value is as follows: Where: is the constant value of unbalance, I QDset is the starting current setting, I max is the maximum value among the three-phase currents, Abs[θ a (t)-θ b (t)] means taking the difference of the phase angles of the sampling values ​​of phases A and B and taking the absolute value; Abs[θ b (t)-θ c (t)] means taking the difference of the phase angles of the B and C phase sampling values ​​and taking the absolute value; Abs[θ c (t)-θ a (t)] means to make a difference between the phase angles of the C and A phase sampling values ​​and take the absolute value; X%120 means to take the remainder of X with respect to 120; When the maximum value of the three-phase current is greater than the set starting current value, and the phase angle difference between any two-phase current is greater than the unbalanced value, after the set delay, it is determined that the sampling value instantaneous unbalanced degree judgment criterion is activated; When the maximum value of the three-phase current is not greater than the set starting current value, or the angle difference between any two-phase currents is not greater than the imbalance value, it is determined that the instantaneous imbalance criterion of the sampling value is not actuated and the protection returns.

7. The variable speed pumped storage unit rotor winding unbalance protection method according to claim 1 is characterized in that: The starting current constant is set to 0.3 to 1 times the rated current of the rotor winding.

8. The variable speed pumped storage unit rotor winding unbalance protection method according to claim 1, characterized in that: In step 4, the thermal accumulation values ​​Accu(t), Bccu(t), and Cccu(t) of the three-phase currents A, B, and C are calculated according to the following formula; Wherein, Accu(t) is the thermal accumulation value of the A-phase current corresponding to the current sampling point; Accu(t-1) is the thermal accumulation value of the A-phase current at the moment corresponding to the previous sampling point; Bccu(t) is the thermal accumulation value of the B-phase current corresponding to the current sampling point; Bccu(t-1) is the thermal accumulation value of the B-phase current corresponding to the previous sampling point; Cccu(t) is the thermal accumulation value of the C-phase current corresponding to the current sampling point; Cccu(t-1) is the thermal accumulation value of the C-phase current corresponding to the previous sampling point; Samp A (t) is the sampling value of phase A current at time t; Samp B (t) is the sampling value of phase B current at time t; Samp C (t) is the sampling value of the C phase current at the tth moment, Δt is the sampling interval, and τ is the time constant.

9. The variable speed pumped storage unit rotor winding unbalance protection method according to claim 1 or 6, characterized in that: In step 4, the amplitude ratio criterion formula is as follows: In the formula, Hccu max Hccu is the maximum value of the three-phase heat accumulation value; min It is the minimum value among the three-phase heat accumulation values; I Phset is the hot start setting value of the amplitude ratio criterion, k phSet is the value of the amplitude ratio coefficient; When the maximum value of the three-phase heat accumulation value is greater than the amplitude ratio criterion hot start setting, and the ratio of the maximum value to the minimum value of the heat accumulation is greater than the amplitude ratio coefficient setting, after the set delay, it is determined that the amplitude ratio criterion is in action; When the maximum value of the three-phase heat accumulation value is less than the amplitude ratio criterion hot start setting, or the ratio of the maximum and minimum heat accumulation values ​​is not greater than the amplitude ratio coefficient setting, it is determined that the amplitude ratio criterion is not actuated and the protection returns.

10. The variable speed pumped storage unit rotor winding unbalance protection method according to claim 1, characterized in that: In step 5, the action behavior of the rotor winding phase failure unbalance protection is determined according to the judgment results of the sampling value instantaneous unbalance degree criterion and the amplitude ratio criterion: When the sampling value instantaneous unbalance judgment criterion is activated, or the amplitude ratio judgment criterion is activated, it is determined that the rotor winding phase failure unbalance protection is activated. After the set delay, the rotor winding phase failure unbalance protection is activated; When the instantaneous unbalance criterion of the sampling value does not work and the amplitude ratio criterion does not work, it is determined that the rotor winding phase failure unbalance protection returns.

11. A variable speed pumped storage unit rotor winding unbalanced protection system using the variable speed pumped storage unit rotor winding unbalanced protection method according to any one of claims 1 to 10, characterized in that: It includes current sampling module, phase angle solving module, instantaneous unbalance degree judgment building module, amplitude ratio judgment building module and unbalance protection action behavior judgment module: The current sampling module obtains the sampling values ​​of the three-phase current of the rotor winding of the variable speed pumped storage unit; The phase angle solving module obtains the amplitude of the three-phase current sampling value, and then obtains the phase angle of the three-phase current sampling value; The instantaneous unbalance criterion module forms a sampling value instantaneous unbalance criterion based on the phase angles of the three-phase current sampling values, and determines the action behavior of the sampling value instantaneous unbalance criterion; The amplitude ratio criterion module calculates the thermal accumulation value of the three-phase current, thereby forming an amplitude ratio criterion, and determines the action behavior of the amplitude ratio criterion; The unbalance protection action behavior module determines the action behavior of the rotor winding phase failure unbalance protection according to the judgment results of the sampling value instantaneous unbalance degree judgment criterion and the amplitude ratio judgment criterion.

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