AT traction network locomotive online positioning and voltage stability monitoring method based on PMU measurement

Abstract

The invention discloses an AT traction network locomotive on-line positioning and voltage stability monitoring method based on PMU measurement, and the method specifically comprises the steps: obtaining the current and voltage data of each phase of an original AT station, calculating the position of a locomotive at the moment through the measurement data, carrying out the iterative correction of the position of the locomotive and the measurement data of each phase through state estimation, and carrying out the measurement of the current and voltage stability. Current and voltage on the locomotive are calculated, and then active power and reactive power of the locomotive are obtained; regarding the locomotive as a constant power load, regarding a large power grid at the front end of the locomotive and a traction power grid as black boxes, and performing Thevenin equivalence on the large power grid and the traction power grid to obtain equivalent voltage and equivalent impedance; and the limit power of the locomotive and the limit voltage corresponding to the limit power at the moment can be obtained by using the obtained equivalent voltage and equivalent impedance, so that the power margin is obtained. According to the method, the calculation process is rapid and accurate, the method has good abnormal data resistance, and accurate real-time power margin is provided; effective online real-time monitoring of the voltage stability of the traction power grid is realized.

Description

Technical Field

[0001] The present invention belongs to the field of traction power grid monitoring, and in particular relates to an AT traction network locomotive online positioning and voltage stability monitoring method based on PMU measurement. Background Art

[0002] Voltage instability in the power system may lead to large-scale power outages, causing huge economic losses and seriously affecting social life. Voltage instability in the traction grid may cause locomotive shutdowns, traffic paralysis, and even serious traffic safety accidents. The traction network voltage stability monitoring method based on PMU measurement only uses relevant measurement information to directly calculate power margin and voltage stability assessment. It does not require power flow calculation, reduces the amount of network solution, and can be applied online to traction grid voltage stability monitoring, which is of great significance to ensure the safe and stable operation of the power system.

[0003] The online monitoring method of power grid voltage stability based on local voltage stability indicators usually first determines the parameters of the single power transmission equivalent system, and then calculates the local voltage stability indicators of the system, and judges the voltage stability of the power grid based on this. In this process, the accuracy of the calculated single power transmission equivalent system parameters determines the effectiveness of the local voltage stability indicators for judging whether the system is stable. In the online monitoring method of power grid voltage stability based on local voltage stability indicators, there are two types according to whether the information to be measured for calculating the single power transmission equivalent system parameters is information within the entire power grid or information of a partial regional power grid. Among them, there are two methods for calculating the single power equivalent system using partial regional information of the power grid: the first is represented by the direct line model, which generally cannot accurately handle the time-varying characteristics of the actual load and cannot track the real-time changes of the load; the second is the method based on the Thevenin equivalent, which requires two or more voltage and current phasors of the system state, and estimates the parameters of the single power transmission equivalent system using the parameter identification method. In theory, the method based on the Thevenin equivalent can accurately handle the time-varying characteristics of the actual load. However, when the continuous excitation conditions are not met, the identified single power transmission equivalent system may have a large error, which is easy to cause misjudgment.

[0004] The voltage stability of the traction power grid has always threatened the safe operation of locomotives, especially in mountainous areas with weak power grids. In the past, railway personnel used experience to judge the departure of trains, and there was no specific calculation method to quantify it. The operating voltage requirement of the traction network is 19KV~29KV. However, in some special cases, although the voltage meets the minimum operating requirements, the maximum power that the line can withstand has reached the critical value. Fluctuations in load power can easily cause voltage collapse. Summary of the invention

[0005] In view of the above problems, the present invention provides an AT traction network locomotive online positioning and voltage stability monitoring method based on PMU measurement.

[0006] The present invention provides a method for online positioning and voltage stability monitoring of AT traction network locomotives based on PMU measurement, comprising the following steps:

[0007] Step 1: Obtain the topological structure of the traction power supply system and related component parameters, including: the impedance matrix per unit length of the traction network line, and the distances between the traction station, AT station, and substation.

[0008] Step 2: Configuration of PMU measurement: PMUs are set at the beginning and end of each AT segment and at each horizontal connection line; and current and voltage measurement data of each phase at the PMU configuration location are obtained.

[0009] Step 3: Based on the topological structure and component parameters described in step 1 and the measurement data described in step 2, taking into account the measurement uncertainty, perform state estimation to estimate the position of the locomotive and the voltage and current of the locomotive.

[0010] Step 4: Based on the locomotive position and the voltage and current of the locomotive described in step 3, identify the Thevenin equivalent circuit of the traction network seen from the locomotive port, including the equivalent potential E, the equivalent reactance X and the equivalent resistance R.

[0011] Step 5: According to the Thevenin equivalent circuit described in step 4, determine the locomotive limit power and the corresponding critical voltage.

[0012] Step 6: According to the limit power and the current power of the locomotive in step 5, the power margin of each locomotive position in the traction network and the power margin of the traction network are obtained.

[0013] Furthermore, the state estimation in step 3 is specifically as follows:

[0014] (1) Determine the section where the locomotive is located.

[0015] In a fully parallel traction power grid with m AT stations on each upstream and downstream sides, the section where the locomotive is located is determined based on the phase of the T-phase current of the overhead contact network between the AT stations; within this section, the direction of the current flowing from the AT station to the overhead contact network is defined as positive. When the directions of the T-phase currents of the overhead contact network measured by the kth AT station and the k+1th AT station are both positive, the locomotive is located between the kth AT station and the k+1th AT station, and the same is true for multiple locomotives.

[0016] (2) Preliminary estimate of the locomotive position.

[0017] It is known that the distance between two AT stations is Lkm. Assuming that the vehicle is d km away from the beginning of the AT segment, the voltage and current equations in the AT segment are:

[0018]

[0019] In the formula, Z T , Z R Respectively represent the self-impedance on the T phase and the R phase, Z RT , Z TF , Z RF They represent the mutual impedances of R to T phase, T to F phase, and R to F phase, respectively. Indicates the current of the contact network, rail and return line at the head end of the AT section. Indicates the current of the end contact network, rails, and return line. Respectively represent the voltage between the contact network and the rail at the beginning and end of the AT segment, represents the current flowing through the car, Indicates locomotive voltage.

[0020] Except for d which is unknown, the rest are component parameters and quantity measurements.

[0021] The initial estimated value d of the locomotive position can be obtained by solving (0) :

[0022]

[0023] (3) The locomotive position, locomotive voltage, current, active power and reactive power are obtained through state estimation.

[0024] The locomotive position described in (2) is used as the initial value, and the state estimation is performed iteratively to obtain the locomotive position and locomotive voltage, current and other state variables.

[0025] The state estimation measurement equation is:

[0026]

[0027] Where z, x and ε are the measurement, state vector and error vector respectively. ε T It is [ε1ε2ε3ε4ε5ε6ε7ε8].

[0028] The observation matrix H of the system is:

[0029]

[0030] The state vector estimate is obtained using the least squares method:

[0031]

[0032] Using the estimated value of the state vector, the locomotive position d is calculated using the same locomotive position calculation formula (1) .

[0033]

[0034] Locomotive position update formula:

[0035] diff (i) =d (i) -d (i-1)

[0036] If diff (i) If the convergence condition is met, the iteration ends and the locomotive position is d (i) ; According to the estimated value of the state vector after the i-th iteration, the voltage, current, active power and reactive power of the locomotive are calculated.

[0037] The voltage across the car:

[0038]

[0039] The current flowing through the car is:

[0040]

[0041] The locomotive active power and reactive power are:

[0042]

[0043] Otherwise, update the locomotive position and perform state estimation iteration:

[0044]

[0045] Furthermore, the specific method of the Thevenin equivalent in step 4 is:

[0046] The Thevenin equivalent system equation is:

[0047]

[0048] (1) In the traction power supply system, the equivalent impedance Z th The corresponding R th and X th Take a series of inductance values ​​around X thi and a series of inductor values ​​R thi .

[0049] (2) For R thi , X thi For each selected value of , the equivalent voltage E of each data sampling point is calculated using the Thevenin equivalent system equation. thi (k).

[0050] (3) For each E thi , calculate its average value:

[0051]

[0052] Calculate the root mean square error:

[0053]

[0054] Select ε i Smallest and its two adjacent points and Perform quadratic fitting to obtain the equivalent impedance R th +jX th The optimal solution is R+jX.

[0055] (4) Calculate E using R+jX th (k), and get the equivalent voltage:

[0056]

[0057] When the load equivalent impedance and the system equivalent impedance are the same, if the critical voltage is greater than 19kv, the power limit of the locomotive is:

[0058]

[0059] The corresponding critical voltage is:

[0060]

[0061] In the formula, θ represents the phase angle of the locomotive terminal voltage, Indicates the phase angle of the locomotive port current.

[0062] If the critical voltage is less than 19kv, the power limit of the locomotive is:

[0063]

[0064] Furthermore, step 6 determines the power margin of each position of the traction grid at this time based on the limit power calculated in step 5, and the locomotive power margin P m The calculation method is:

[0065] P m =P max -P

[0066] After obtaining the power margin, we can know whether the car can be started at each position at this time, and if it can be started, what is the maximum power at this time.

[0067] The beneficial technical effects of the present invention compared with the prior art are:

[0068] (1) The present invention uses the current and voltage data measured by the AT station to calculate the position of the locomotive after filtering. The calculation process is fast and accurate, and has good anti-abnormal data capabilities.

[0069] (2) The high resistance characteristics of the traction power grid are taken into account when calculating the Thevenin equivalent value of the present invention, thereby further improving the accuracy of the Thevenin equivalent value.

[0070] (3) The present invention utilizes power margin to monitor voltage stability online in the traction power grid, providing accurate real-time power margin. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 This is a topological diagram of the model built for the simulation of the present invention.

[0072] Figure 2 This is the line topology diagram between two AT stations.

[0073] Figure 3 This is a schematic diagram of the Thevenin equivalent.

[0074] Figure 4 This is the graph of the change of limit power with distance in Example 1.

[0075] Figure 5 This is the comparison chart of Example 2 where two cars are going up and down, and one car is fixed at the end of the up line. The limit power of the down line locomotive changes with distance.

[0076] Figure 6 This is a comparison diagram of the locomotive position before and after state estimation and the actual position in Example 3. DETAILED DESCRIPTION

[0077] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0078] The present invention provides an AT traction network locomotive online positioning and voltage stability monitoring method based on PMU measurement. First, the original current and voltage data of each phase of the AT station are obtained, and the position of the locomotive at this time is calculated using the measured data. The locomotive position and the measured data of each phase are iteratively corrected using state estimation, and the current and voltage on the locomotive are calculated to obtain the active power and reactive power of the locomotive. The locomotive is regarded as a constant power load, and the large power grid at the front of the locomotive and the traction power grid are regarded as black boxes. The Thevenin equivalent is performed on them to obtain the equivalent voltage and equivalent impedance. The equivalent voltage and equivalent impedance obtained can be used to obtain the limit power at the locomotive at this time and the limit voltage corresponding to the limit power, and then the power margin can be obtained. Specifically:

[0079] Step 1: Obtain the topological structure of the traction power supply system and related component parameters, including: the impedance matrix per unit length of the traction network line, and the distances between the traction station, AT station, and substation.

[0080] Step 2, PMU measurement configuration: Set up PMU at the beginning, end and each horizontal connection of each AT segment; obtain the current and voltage measurement data of each phase at the PMU configuration point. The line topology between the two AT stations is as follows: Figure 2 shown.

[0081] Step 3: Based on the topological structure and component parameters described in step 1 and the measurement data described in step 2, taking into account the measurement uncertainty, perform state estimation to estimate the position of the locomotive and the voltage and current of the locomotive.

[0082] The state estimation is as follows:

[0083] (1) Determine the section where the locomotive is located.

[0084] In a fully parallel traction power grid with m AT stations on each upstream and downstream sides, the section where the locomotive is located is determined based on the phase of the T-phase current of the overhead contact network between the AT stations; within this section, the direction of the current flowing from the AT station to the overhead contact network is defined as positive. When the directions of the T-phase currents of the overhead contact network measured by the kth AT station and the k+1th AT station are both positive, the locomotive is located between the kth AT station and the k+1th AT station, and the same is true for multiple locomotives.

[0085] (2) Preliminary estimate of locomotive position.

[0086] It is known that the distance between two AT stations is Lkm. Assuming that the vehicle is d km away from the beginning of the AT segment, the voltage and current equations in the AT segment are:

[0087]

[0088] In the formula, Z T , Z R Respectively represent the self-impedance on the T phase and the R phase, Z RT , Z TF , Z RF They represent the mutual impedances of R to T phase, T to F phase, and R to F phase, respectively. Indicates the current of the contact network, rail and return line at the head end of the AT section. Indicates the current of the end contact network, rails, and return line. Respectively represent the voltage between the contact network and the rail at the beginning and end of the AT segment, represents the current flowing through the car, Indicates locomotive voltage.

[0089] Except for d which is unknown, the rest are component parameters and quantity measurements.

[0090] The initial estimated value d of the locomotive position can be obtained by solving (0) :

[0091]

[0092] (3) The locomotive position, locomotive voltage, current, active power and reactive power are obtained through state estimation.

[0093] The locomotive position described in (2) is used as the initial value, and the state estimation is performed iteratively to obtain the locomotive position and locomotive voltage, current and other state variables.

[0094] The state estimation measurement equation is:

[0095]

[0096] Where z, x and ε are the measurement, state vector and error vector respectively. ε T It is [ε1ε2ε3ε4ε5ε6ε7ε8].

[0097] The observation matrix H of the system is:

[0098]

[0099] The state vector estimate is obtained using the least squares method:

[0100]

[0101] Using the estimated value of the state vector, the locomotive position d is calculated using the same locomotive position calculation formula (1) .

[0102]

[0103] Locomotive position update formula:

[0104] diff (i) =d (i) -d (i-1)

[0105] If diff (i) If the convergence condition is met, the iteration ends and the locomotive position is d (i) ; According to the estimated value of the state vector after the i-th iteration, the voltage, current, active power and reactive power of the locomotive are calculated.

[0106] The voltage across the car:

[0107]

[0108] The current flowing through the car is:

[0109]

[0110] The locomotive active power and reactive power are:

[0111]

[0112] Otherwise, update the locomotive position and perform state estimation iteration:

[0113]

[0114] Step 4: According to the locomotive position and the locomotive voltage and current described in step 3, identify the Thevenin equivalent circuit of the traction network seen from the locomotive port, including the equivalent potential E, the equivalent reactance X and the equivalent resistance R. The Thevenin equivalent schematic diagram is as follows: Figure 3 shown.

[0115] The specific method of Thevenin equivalence is:

[0116] The Thevenin equivalent system equation is:

[0117]

[0118] (1) In the traction power supply system, the equivalent impedance Z th The corresponding R th and X th Take a series of inductance values ​​around X thi and a series of inductor values ​​R thi .

[0119] (2) For R thi , X thi For each selected value of , the equivalent voltage E of each data sampling point is calculated using the Thevenin equivalent system equation. thi (k).

[0120] (3) For each E thi , calculate its average value:

[0121]

[0122] Calculate the root mean square error:

[0123]

[0124] Select ε i Smallest and its two adjacent points and Perform quadratic fitting to obtain the equivalent impedance R th +jX th The optimal solution is R+jX.

[0125] (4) Calculate E using R+jX th (k), and get the equivalent voltage:

[0126]

[0127] When the load equivalent impedance and the system equivalent impedance are the same, if the critical voltage is greater than 19kv, the power limit of the locomotive is:

[0128]

[0129] The corresponding critical voltage is:

[0130]

[0131] In the formula, θ represents the phase angle of the locomotive terminal voltage, Indicates the phase angle of the locomotive port current.

[0132] If the critical voltage is less than 19kv, the power limit of the locomotive is:

[0133]

[0134] Step 5: According to the Thevenin equivalent circuit described in step 4, determine the locomotive limit power and the corresponding critical voltage.

[0135] Step 6: According to the limit power and the current power of the locomotive in step 5, the power margin of each locomotive position in the traction network and the power margin of the traction network are obtained.

[0136] Locomotive power margin P m The calculation method is:

[0137] P m =P max -P

[0138] After obtaining the power margin, we can know whether the car can be started at each position at this time, and if it can be started, what is the maximum power at this time.

[0139] Example:

[0140] The experimental example of collecting experimental data using the AT traction station built with MATLAB / SIMULINK is shown in the topological structure diagram of the AT traction station. Figure 1 As shown. Among them, the 220KV side is an infinite power supply, the impedance matrix per unit length of the traction network line, the parameters of the autotransformer, the distance between the traction station, AT station, and the substation, etc. are obtained from field experiments. The locomotive model of the single-vehicle example is a continuously increasing power load. In the multi-vehicle example, the fixed locomotive model is a constant power load with a power of 10MW, and the mobile locomotive model is a continuously increasing power load. The PMU measurement device is installed at the left and right ends of each AT station and on each parallel connection line to measure the current and voltage information of each phase. In the following examples, Pm uses 100MW as the reference value.

[0141] Calculation example 1:

[0142] like Figure 4 To verify the accuracy of the equivalent value and the power margin calculation effect of the present invention, the attached Figure 1 The load between the two TR phases of the uplink is continuously increased every 1 km to obtain the limit power, and the data measured by the PMU is stored for use in the method of the present invention. The comparison between the limit power obtained by simulation and the limit power obtained by the method of the present invention is shown in Table 1.

[0143] Table 1 Comparison table of limit power of example 1

[0144] Location (km) Pm(Simulation) Pm (present invention) error Location (km) Pm(Simulation) Pm (present invention) error 1 0.5834 0.5754 0.008 16 0.4944 0.4839 0.0105 2 0.5660 0.5569 0.0091 17 0.4951 0.4851 0.01 3 0.5539 0.5441 0.0098 18 0.5003 0.4909 0.0094 4 0.5467 0.5366 0.0101 19 0.5101 0.5041 0.006 5 0.5440 0.5337 0.0103 20 0.5251 0.5200 0.0051 6 0.5455 0.5353 0.0102 21 0.4983 0.4912 0.0071 7 0.5514 0.5414 0.01 22 0.4780 0.4672 0.0108 8 0.5618 0.5522 0.0096 23 0.4632 0.4518 0.0114 9 0.5774 0.5686 0.0088 24 0.4527 0.4411 0.0116 10 0.5990 0.5917 0.0073 25 0.4462 0.4346 0.0116 11 0.5640 0.5546 0.0094 26 0.4433 0.4318 0.0115 12 0.5381 0.5290 0.0091 27 0.4439 0.4328 0.0111 13 0.5192 0.5105 0.0087 28 0.4480 0.4373 0.0107 14 0.5061 0.4958 0.0103 29 0.4558 0.4458 0.01 15 0.4980 0.4874 0.0106 30 0.4679 0.4591 0.0088

[0145] Calculation example 2:

[0146] like Figure 5 To verify the accuracy of the equivalent value and the power margin calculation effect of the present invention, the attached Figure 1 A locomotive with a constant power of 10MW was added at 30km between the two TR phases on the uplink. The load was continuously increased every 1km on the downlink to obtain the limit power, and the data measured by the PMU was stored for the method of the present invention. The comparison between the limit power obtained by simulation and the limit power obtained by the method of the present invention is shown in Table 2.

[0147] Table 2 Comparison table of limit power of example 2

[0148]

[0149]

[0150] Calculation example 3:

[0151] like Figure 6 As shown, in order to verify the state estimation iterative correction of the locomotive position proposed in the present invention, the comparison between the locomotive position before and after the state estimation and the actual position is calculated in Example 3, as shown in Table 3.

[0152] Table 3 Comparison of locomotive position before and after state estimation and actual position

[0153]

[0154] It can be seen that the average error before state estimation is 0.3073 km and the maximum error is 1.2521 km. After state estimation, the average error is 0.0777 km and the maximum error is 0.2321 km.

[0155] In summary, the present invention can determine the position of the locomotive based on the measured data, and its judgment process is rapid and accurate with strong anti-interference ability. It solves the problem of judging voltage stability based on experience in the traction network, quantifies the voltage stability from the perspective of power margin, and provides accurate limit power and limit voltage corresponding to the limit power, thereby realizing effective online real-time monitoring of the voltage stability of the traction power grid.

Claims

1. A method for online positioning and voltage stability monitoring of AT traction network locomotives based on PMU measurement, characterized in that: The following steps are involved: Step 1: Obtain the topological structure of the traction power supply system and related component parameters, including: the impedance matrix per unit length of the traction network line, and the distances between the traction station, AT station, and substation; Step 2: PMU measurement configuration: PMUs are set at the beginning and end of each AT segment and at each horizontal connection line; current and voltage measurement data of each phase at the PMU configuration location are obtained; Step 3: Based on the topological structure and component parameters in step 1 and the measured data in step 2, taking into account the measurement uncertainty, perform state estimation to estimate the position of the locomotive and the voltage and current of the locomotive; Step 4: According to the locomotive position and the voltage and current of the locomotive described in step 3, identify the Thevenin equivalent circuit of the traction network seen by the locomotive port, including the equivalent potential E, the equivalent reactance X and the equivalent resistance R; Step 5: Determine the locomotive limit power and the corresponding critical voltage according to the Thevenin equivalent circuit described in step 4; Step 6: According to the limit power and the current power of the locomotive in step 5, the power margin of each locomotive position in the traction network and the power margin of the traction network are obtained.

2. The method for online positioning and voltage stability monitoring of AT traction network locomotives based on PMU measurement according to claim 1 is characterized in that: The state estimation in step 3 is specifically as follows: (1) Determine the section where the locomotive is located; In a fully parallel traction power grid with m AT stations in both the upstream and downstream directions, the section where the locomotive is located is determined based on the phase of the T-phase current of the overhead contact network between the AT stations. In this interval, the direction of the current flowing from the AT station to the overhead line is defined as positive. When the directions of the T-phase currents of the overhead line measured by the kth AT station and the k+1th AT station are both positive, the vehicle is located between the kth AT station and the k+1th AT station, and the same is true for multi-vehicle operation. (2) Preliminary estimation of the locomotive position; It is known that the distance between two AT stations is Lkm. Assuming that the vehicle is d km away from the beginning of the AT segment, the voltage and current equations in the AT segment are: In the formula, Z T , Z R Respectively represent the self-impedance on the T phase and the R phase, Z RT , Z TF , Z RF They represent the mutual impedances of R to T phase, T to F phase, and R to F phase, respectively. Indicates the current of the contact network, rail and return line at the head end of the AT section. Indicates the current of the end contact network, rails, and return line. Respectively represent the voltage between the contact network and the rail at the beginning and end of the AT segment, represents the current flowing through the car, Indicates locomotive voltage; Except for unknown d, the rest are component parameters and quantity measurements; The initial estimated value d of the locomotive position can be obtained by solving (0) : (3) Obtain locomotive position, locomotive voltage, current, active power and reactive power through state estimation; Taking the locomotive position described in (2) as the initial value, iteratively performing state estimation to obtain the locomotive position and locomotive voltage, current and other state variables; The state estimation measurement equation is: Where z, x and ε are the measurement, state vector and error vector respectively. ε T is [ε1ε2ε3ε4ε5ε6ε7ε8]; The observation matrix H of the system is: The state vector estimate is obtained using the least squares method: Using the estimated value of the state vector, the locomotive position d is calculated using the same locomotive position calculation formula (1) ; Locomotive position update formula: diff (i) =d (i) -d (i-1) If diff (i) If the convergence condition is met, the iteration ends and the locomotive position is d (i) ; According to the estimated value of the state vector after the i-th iteration, the voltage, current, active power and reactive power of the locomotive are calculated; The voltage across the car: The current flowing through the car is: The locomotive active power and reactive power are: Otherwise, update the locomotive position and perform state estimation iteration:

3. The method for online positioning and voltage stability monitoring of AT traction network locomotives based on PMU measurement according to claim 2 is characterized in that: The specific method of the Thevenin equivalent in step 4 is: The Thevenin equivalent system equation is: (1) In the traction power supply system, the equivalent impedance Z th The corresponding R th and X th Take a series of inductance values ​​around X thi and a series of inductor values ​​R thi ; (2) For R thi , X thi For each selected value of , the equivalent voltage E of each data sampling point is calculated using the Thevenin equivalent system equation. thi (k); (3) For each E thi , calculate its average value: Calculate the root mean square error: Select ε i Smallest and its two adjacent points and Perform quadratic fitting to obtain the equivalent impedance R th +jX th The optimal solution is R+jX; (4) Calculate E using R+jX th (k), and get the equivalent voltage: When the load equivalent impedance and the system equivalent impedance are the same, if the critical voltage is greater than 19kv, the power limit of the locomotive is: The corresponding critical voltage is: In the formula, θ represents the phase angle of the locomotive terminal voltage, Indicates the phase angle of the locomotive port current; If the critical voltage is less than 19kv, the power limit of the locomotive is:

4. The method for online positioning and voltage stability monitoring of AT traction network locomotives based on PMU measurement according to claim 3 is characterized in that: The step 6 determines the power margin of each position of the traction grid according to the limit power calculated in step 5, and the locomotive power margin P m The calculation method is: P m =P max -P After obtaining the power margin, we can know whether the car can be started at each position at this time, and if it can be started, what is the maximum power at this time.

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