Power system equivalent method considering transient characteristics of wind power cluster

Abstract

This invention discloses a power system equivalent method considering the transient characteristics of wind power clusters. The method includes: Step 1, aggregating wind farms based on the average minimum transient voltage; Step 2, simplifying the station outlet buses of wind farms belonging to the same cluster using the constant power transformation method; Step 3, simplifying the external system network using the current trench simplification method (CSR) and equating the load to the retained buses; Step 4, determining the transient recovery characteristics of the equivalent wind turbine units after a fault. This invention addresses the technical problem that as the scale of new energy units grows larger, the impact of their transient characteristics on the dynamic equivalent of the power system becomes increasingly significant. Continuing to use simplification methods often leads to large errors between the transient characteristics of the power system after equating and those before equating, failing to meet the requirements for the accuracy of dynamic equivalent power system data.

Description

Technical Field

[0001] This invention belongs to the field of power system equivalent technology, and particularly relates to a power system equivalent method that considers the transient characteristics of wind power clusters. Background Technology

[0002] Dynamic equivalent modeling of power systems is a modeling method that simplifies power systems to reduce their size. Its basic requirement is that the steady-state characteristics (e.g., line power flow, bus voltage, and short-circuit capacity) and transient characteristics (e.g., active and reactive power fluctuations, bus voltage fluctuations, and frequency fluctuations after a fault) of the equivalent system are consistent with those of the original system, and the error is within the allowable range.

[0003] The conventional dynamic equivalent method for power systems is the same as the equivalent method for co-regulation. Its main steps include: determining the systems to be retained, identifying and dividing co-regulation generator groups, simplifying co-regulation generator buses, simplifying network buses, and aggregating the models and parameters of co-regulation generators and their regulation systems.

[0004] The equivalent load method can handle conventional hydropower, thermal power and nuclear power units, but it cannot handle new energy units such as wind power and photovoltaic power. For new energy units in the power system, the method of converting them into equivalent loads is generally used for simplification. This method will lose the transient characteristics of the new energy units.

[0005] With the construction and development of new power systems based on new energy sources, the scale of new energy generating units is getting larger and larger. The impact of their transient characteristics on the dynamic equivalence of the power system is becoming increasingly difficult to ignore. Continuing to use simplified processing methods often leads to a large error between the transient characteristics of the power system after equivalence and the transient characteristics of the power system before equivalence, which cannot meet the requirements for the accuracy of the dynamic equivalence of the power system. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a power system equivalent method that takes into account the transient characteristics of wind power clusters, so as to solve the problem that as the scale of new energy units becomes larger and larger, the impact of their transient characteristics on the dynamic equivalent of the power system can no longer be ignored. Continuing to use simplified processing methods often leads to a large error between the transient characteristics of the power system after equivalent and the transient characteristics of the power system before equivalent, which cannot meet the requirements for the accuracy of the dynamic equivalent of the power system.

[0007] The technical solution of this invention is:

[0008] An equivalent method for power systems considering the transient characteristics of wind power clusters, the method comprising:

[0009] Step 1: Aggregate wind farms based on the average minimum transient voltage;

[0010] Step 2: Use the constant power transformation method to simplify the station outlet busbars of wind farms belonging to the same cluster;

[0011] Step 3: Use the Current Trench Simplification (CSR) method to simplify the network of the external system and distribute the loads to the retained buses.

[0012] Step 4: Determine the transient recovery characteristics of the equivalent wind turbine unit after a fault.

[0013] Methods for aggregating wind farms based on the average minimum transient voltage include: identifying wind farms that the power system does not need to retain after equivalence, and assuming these wind farms form a set W = {w1, w2, ..., w...} n}, where w n This is the nth wind farm; after determining the equivalent values, the power system needs to perform fault simulations, assuming these faults constitute a fault set F = {f1, f2, ..., f...} m}, where f m This is the m-th fault, where m is the total number of faults. A simulation is performed on one fault in the fault set to obtain the lowest transient voltage value of the wind farm's outlet bus during the fault period. Through simulation calculations, the wind farm's voltage (w) is obtained. i The set of lowest transient voltage values ​​is U i ={u1, u2, ..., u m}, where u m By performing fault f m The simulated wind farm w i The lowest transient voltage value at the station outlet during a fault;

[0014] Calculate wind farm w i Average minimum transient voltage value Each wind farm is divided into six categories according to its average minimum transient voltage value and the following voltage range: (1) (2) (3) (4) (5) (6) Wind farms belonging to the same category form a cluster, and their transient characteristics are simulated using an equivalent unit.

[0015] After the equivalent, the power system can have a maximum of 6 equivalent wind turbine units.

[0016] The station outlet busbars of wind farms belonging to the same cluster are simplified and represented by an equivalent busbar; each wind farm belonging to the same cluster is represented by an equivalent wind turbine connected to the above equivalent busbar, and the total power generated by wind farms belonging to the same cluster remains unchanged before and after equivalence.

[0017] When equipotentially applying loads to the reserved busbars, it is essential to ensure that the power flow deviation is zero.

[0018] Methods for determining the transient recovery characteristics of an equivalent wind turbine after a fault include:

[0019] Step 4.1: Use formula (1) to describe the active power recovery characteristics after a fault;

[0020]

[0021] The parameter to be determined is P. i0 k pi and P i1 ;

[0022] Step 4.2: Use formula (2) to describe the reactive power recovery characteristics after a fault;

[0023]

[0024] The parameter to be determined is q. i0 k qi and q i1 ;

[0025] Step 4.3: Determine the fitting parameters to be determined in formulas (1) and (2).

[0026] Methods for determining the fitting parameters to be determined in formulas (1) and (2) include:

[0027] Step 4.3.1: Determine the observation busbar and observation line as needed;

[0028] Step 4.3.2: Select a fault f from the fault set F. j Perform simulation;

[0029] Step 4.3.3: Obtain the voltage curve v of the power system at the observation point before the equivalent voltage is measured. q (t) and the voltage curve v of the equivalent power system h (t), calculation error Where v q (i) is the voltage value of the power system before the equivalent value at time i, v h (i) is the equivalent voltage value of the power system at time j;

[0030] Step 4.3.4: Obtain the active power curve p of the power system at the observation point before the observation line is equivalent. q (t) and the equivalent active power curve p of the power system h (t), calculation error δ p ;

[0031] Step 4.3.5: Obtain the reactive power curve q of the power system at the observation point before the observation line is equivalent. q (t) and the reactive power curve q of the equivalent power system h (t), calculation error δ q ;

[0032] Step 4.3.6: Calculate the fault f. j error

[0033] Step 4.3.7: Repeat steps 4.3.2-4.3.6 to calculate the error of all faults in the fault set F, and obtain the total error. Where m is the total number of faults;

[0034] Step 4.3.8, with the total error δ F Using the minimum as the objective function, the particle swarm optimization algorithm is employed to obtain the parameters corresponding to the optimal active and reactive power recovery characteristics of each equivalent unit.

[0035] error Where p q (i) is the voltage value of the power system before the equivalent value at time i, p h (i) is the equivalent active power of the power system at time i;

[0036] error Where q q (i) is the voltage value of the power system before the equivalent value at time i, q h (i) is the equivalent active power of the power system at time i.

[0037] The beneficial effects of this invention are:

[0038] The power system equivalent method considering the transient characteristics of wind power clusters provided by this invention overcomes the problem that the transient characteristic error of the system after the equivalent is not met due to the lack of equivalent wind farms in the existing power system dynamic equivalent program, thus improving the accuracy of dynamic equivalent.

[0039] It can effectively handle dynamic equivalent power systems when there are a large number of wind turbines in the power system, thus improving the accuracy of the equivalent system.

[0040] The project addresses the technical challenges of increasingly larger new energy generating units whose transient characteristics have a significant impact on the dynamic equivalence of the power system. It also addresses the issue that continuing to use simplified processing methods often leads to large errors between the equivalent and unequivalent transient characteristics of the power system, failing to meet the requirements for the accuracy of dynamic equivalence of the power system. Attached Figure Description

[0041] Figure 1This is a schematic diagram of the active power recovery characteristics of the i-th equivalent wind turbine unit after a fault, according to a specific embodiment of the present invention.

[0042] Figure 2 This is a schematic diagram illustrating the reactive power recovery characteristics of the i-th equivalent wind turbine unit after a fault, according to a specific embodiment of the present invention. Detailed Implementation

[0043] An equivalent method for power systems considering the transient characteristics of wind power clusters, the method comprising the following steps:

[0044] Step 1: Aggregate wind farms based on the average minimum transient voltage.

[0045] After determining the equivalent wind farms that the power system does not need to retain, let these wind farms form a set W = {w1, w2, ..., w...} n}, where w n This is the nth wind farm. After determining the equivalent faults, the power system needs to perform fault simulations. Let these faults constitute a fault set F = {f1, f2, ..., f...} m}, where f m This is the m-th fault, where m is the total number of faults. A simulation is performed on a single fault in the fault set to obtain the lowest transient voltage value of the wind farm's outlet bus during the fault period. Through simulation calculations, the wind farm's voltage (w) is obtained. i The set of lowest transient voltage values ​​is U i ={u1, u2, ..., u m}, where u m By performing fault f m The simulated wind farm w i The lowest transient voltage value at the station outlet during a fault.

[0046] Calculate wind farm w i Average minimum transient voltage value Each wind farm is divided into six categories according to its average minimum transient voltage value and the following voltage range: (1) (2) (3) (4) (5) (6) Wind farms belonging to the same category form a cluster, and their transient characteristics are simulated by an equivalent unit. After equivalence, the power system can have a maximum of 6 equivalent wind turbine units.

[0047] Step 2: Using the constant power transformation method, the station outlet busbars of wind farms belonging to the same cluster are simplified and represented by an equivalent busbar. Each wind farm belonging to the same cluster is represented by an equivalent wind turbine connected to the aforementioned equivalent busbar, ensuring that the total power generated by wind farms belonging to the same cluster remains unchanged before and after equivalence.

[0048] Step 3: Use the Current Sink Reduction (CSR) method to simplify the network of the external system, convert the load to the reserved bus, and ensure that the power flow deviation is zero.

[0049] Step 4: Determine the transient recovery characteristics of the equivalent wind turbine unit after a fault.

[0050] Let the active power recovery characteristics after the fault of the i-th equivalent wind turbine be as follows: Figure 1 As shown, the reactive power recovery characteristics are as follows: Figure 2 As shown, where i≤6.

[0051] Formula (1) is used to describe the active power recovery characteristics after a fault.

[0052]

[0053] The parameter to be determined is P. i0 k pi and P i1 .

[0054] Formula (2) is used to describe the reactive power recovery characteristics after a fault.

[0055]

[0056] The parameter to be determined is q. i0 k qi and q i1 .

[0057] The fitting parameters to be determined in formulas (1) and (2) are determined using the following methods.

[0058] (1) Determine the observation bus and observation line as needed.

[0059] (2) Select a fault f from the fault set F. j Perform simulation.

[0060] (3) Obtain the voltage curve v of the power system at the observation point before the equivalent voltage is obtained. q (t) and the voltage curve v of the equivalent power system h (t), calculation error Where v q (i) is the voltage value of the power system before the equivalent value at time i, v h(i) is the equivalent voltage value of the power system at time i.

[0061] (4) Obtain the active power curve p of the power system at the observation point before the equivalent value of the observed line. q (t) and the equivalent active power curve p of the power system h (t), calculation error Where p q (i) is the voltage value of the power system before the equivalent value at time i, p h (i) is the equivalent active power of the power system at time i.

[0062] (5) Obtain the reactive power curve q of the power system at the observation point before the equivalent value of the observed line. q (t) and the reactive power curve q of the equivalent power system h (t), calculation error Where q q (i) is the voltage value of the power system before the equivalent value at time i, q h (i) is the equivalent active power of the power system at time i.

[0063] (6) The fault f is calculated j error

[0064] (7) Repeat steps (2)-(6) to calculate the error of all faults in the fault set F, and obtain the total error. Where m is the total number of faults.

[0065] (8) Using the total error δ F Using the minimum as the objective function, the particle swarm optimization algorithm is employed to obtain the parameters corresponding to the optimal active and reactive power recovery characteristics of each equivalent unit.

[0066] Compared with existing technologies, the power system equivalent method considering the transient characteristics of wind power clusters provided by this invention has the following advantages:

[0067] The power system equivalent method considering the transient characteristics of wind power clusters provided by this invention overcomes the problem that the transient characteristic error of the system after the equivalent is not met due to the lack of equivalent wind farms in the existing power system dynamic equivalent program, thus improving the accuracy of dynamic equivalent.

Claims

1. An equivalent method for power systems considering the transient characteristics of wind power clusters, characterized in that: The method includes: Step 1: Aggregate wind farms based on the average minimum transient voltage; Step 2: Use the constant power transformation method to simplify the station outlet busbars of wind farms belonging to the same cluster; Step 3: Use the Current Trench Simplification (CSR) method to simplify the network of the external system and distribute the loads to the retained buses. Step 4: Determine the transient recovery characteristics of the equivalent wind turbine unit after a fault; the determination methods include: Step 4.1: Use formula (1) to describe the active power recovery characteristics after a fault; （1）； The parameter to be determined is: , and ; Step 4.2: Use formula (2) to describe the reactive power recovery characteristics after a fault; （2）； The parameter to be determined is: , and ; Step 4.3: Determine the parameters to be determined in formulas (1) and (2); the methods for determining the parameters include: Step 4.3.1: Determine the observation busbar and observation line as needed; Step 4.3.2, from the fault set Take one fault Perform simulation; Step 4.3.3: Obtain the voltage curve of the power system at the observation point before the equivalent voltage is measured. Voltage curves of the power system after equivalent values Calculation error ,in It is the voltage value of the power system before the equivalent value at time i. It is the equivalent voltage value of the power system at time i; Step 4.3.4: Obtain the active power curve of the power system at the observation point before the observation line is equivalent. The active power curve of the power system after equalization Calculation error ; Step 4.3.5: Obtain the reactive power curve of the power system at the observation point before the observation line is equivalent. The reactive power curve of the power system after equalization Calculation error ; Step 4.3.6: Calculate the fault. error = ; Step 4.3.7: Repeat steps 4.3.2-4.3.6 to calculate the fault set. The total error is obtained by taking the errors of all faults. ,in This is the total number of faults; Step 4.3.8, with total error Using the minimum as the objective function, the particle swarm optimization algorithm is employed to obtain the parameters corresponding to the optimal active and reactive power recovery characteristics of each equivalent unit.

2. The power system equivalent method considering the transient characteristics of wind power clusters according to claim 1, characterized in that: Methods for aggregating wind farms based on the average minimum transient voltage include: identifying wind farms that the power system does not need to retain after equivalence, and assuming these wind farms constitute a set. ,in It is the first A wind farm; after determining the equivalent faults, the power system needs to perform fault simulations, assuming these faults constitute a fault set. ,in It is the first One fault, This represents the total number of faults; a simulation is performed on one fault within the fault set to obtain the lowest transient voltage value of the wind farm's outlet bus during the fault period; through simulation calculations, the wind farm... The set of lowest transient voltage values ​​is ,in By performing fault The simulated wind farm The lowest transient voltage value at the station outlet during a fault; Calculate wind farm Average minimum transient voltage value Each wind farm is divided into six categories according to its average minimum transient voltage value and the following voltage range: (1) (2) (3) (4) (5) (6) Wind farms belonging to the same category form a cluster, and their transient characteristics are simulated using an equivalent unit.

3. The power system equivalent method considering the transient characteristics of wind power clusters according to claim 2, characterized in that: After the equivalent, the power system can have a maximum of 6 equivalent wind turbine units.

4. The power system equivalent method considering the transient characteristics of wind power clusters according to claim 1, characterized in that: The station outlet busbars of wind farms belonging to the same cluster are simplified and represented by an equivalent busbar; each wind farm belonging to the same cluster is represented by an equivalent wind turbine connected to the above equivalent busbar, and the total power generated by wind farms belonging to the same cluster remains unchanged before and after equivalence.

5. The power system equivalent method considering the transient characteristics of wind power clusters according to claim 1, characterized in that: When equipotentially applying loads to the reserved busbars, it is essential to ensure that the power flow deviation is zero.

6. The power system equivalent method considering the transient characteristics of wind power clusters according to claim 1, characterized in that: error in It is the voltage value of the power system before the equivalent value at time i. It is the equivalent active power value of the power system at time i; error ,in It is the voltage value of the power system before the equivalent value at time i. It is the equivalent active power value of the power system at time i.

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