Control method, device, equipment and storage medium for stable voltage

Abstract

The embodiment of the present invention discloses a control method and device, equipment and storage medium for stabilizing voltage. The method is applied to an electric power system including an induction motor and an energy storage system. The method includes: determining the operating state of the electric power system according to the torque difference data of the induction motor; if the operating state is load instability, determining the total amount of load shedding of the electric power system by using the equivalent inertia center frequency; and determining the first charge and discharge state of the energy storage system; performing load shedding processing on the electric power system by using the total amount of load shedding, and determining the second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system, and changing the energy storage system to the second charge and discharge state to stabilize the voltage. Through the above-mentioned method, the energy storage system participates in the load shedding emergency control strategy for protecting transient voltage safety. When the energy storage system participates in the case of voltage instability, part of the load is cut off, which not only reduces the amount of load shedding, but also improves the transient voltage stability.

Description

Technical Field

[0001] The present invention relates to the technical field of power system automation, and in particular to a control method and device, equipment and storage medium for stabilizing voltage. Background Art

[0002] Although the characteristics of my country's modern power system, such as large units, large power grids, ultra-high voltage, long distances, heavy loads, large regional networking, and AC / DC combined systems, have strongly guaranteed the society's electricity demand, the safety of the power system is also facing challenges due to nonlinear and impact loads, especially the widespread use of power electronic conversion devices. Due to the constraints of resources, economy, and environment, the continuous emergence of dense power sources in the region and long-distance large-capacity transmission systems, the power grid structure is relatively weak in the early stage and development of power grid construction, which often leads to the power system often operating in a state close to the limit, which makes the power system stability problem serious. Once the stability is destroyed, it often causes the parallel generators to lose synchronization, the frequency continues to drop seriously and cause the system to collapse, and the voltage continues to drop seriously and cause the system to collapse. This will cause large-scale and long-term power outages. In the worst case, it may cause the power system to collapse and disintegrate.

[0003] Researching and implementing corresponding emergency control measures for transient stability can not only improve the reliability of system operation, but also generate direct economic benefits due to the improvement of transmission capacity. In addition, from the perspective of economy and practicality, preventive control is not always flexible and effective. For some serious accidents with a small probability, it may be more reasonable to take emergency control measures than preventive control. In some cases, such as the loss of synchronization of large-capacity units at a distance, emergency control is even the only practical way to prevent transient voltage instability in the system.

[0004] With the continuous increase of load in the system, the traditional low-voltage load shedding method has become increasingly unable to meet the needs of maintaining safe and stable operation of the power grid. The traditional low-voltage load shedding method sets a certain voltage threshold. When the voltage of certain nodes in the system is lower than the set threshold, a fixed proportion of the load is cut off. Its control strategy is generated by offline calculation. The offline calculation is based on the simulated operating state of the system, which is different from the actual operating state of the system, making it difficult to achieve optimal load shedding. Therefore, it is necessary to propose a new low-voltage load shedding method that can not only ensure the safe and stable operation of the system and prevent the occurrence of voltage collapse accidents, but also reduce the economic losses caused by low-voltage load shedding.

[0005] When a large-scale power shortage occurs due to a fault in the receiving circuit, if the emergency control is insufficient, a large-scale power outage will occur. Therefore, low-frequency load reduction is the most effective measure to ensure system stability after a shortage occurs. The most commonly used measure is load shedding, but shedding a large amount of load will cause significant economic losses to society. In California, the U.S., excessive growth in disaster load caused a major fault in the power system, and load shedding measures were implemented, resulting in a large number of casualties.

[0006] Therefore, there is still a lack of an effective means to stabilize voltage. Summary of the invention

[0007] The main purpose of the present invention is to provide a control method and device, equipment and storage medium for stabilizing voltage, which can solve the problem of lack of an effective means for stabilizing voltage in the prior art.

[0008] To achieve the above object, the present invention provides a first aspect of a control method for stabilizing voltage, the method being applied to a power system, the power system comprising an induction motor and an energy storage system, the method comprising:

[0009] Acquiring operation data of the power system, the operation data at least including torque difference data of the induction motor;

[0010] determining an operating state of the power system according to the torque difference data of the induction motor, wherein the operating state at least includes load instability;

[0011] If the operating state is load instability, the total amount of load shedding of the power system is determined using the equivalent inertia center frequency of the power system; and the first charge and discharge state of the energy storage system is determined;

[0012] The power system is subjected to load shedding processing using the total load shedding amount, and a second charge and discharge state of the energy storage system is determined according to the first charge and discharge state and the active output instruction of the energy storage system, and the energy storage system is controlled to change from the first charge and discharge state to the second charge and discharge state, so as to stabilize the voltage of the power system.

[0013] In a feasible implementation, the method further includes:

[0014] Determine the target absorbed power of the energy storage system and the actual load shedding amount of the power system by using the total amount of load shedding and the preset functional relationship between the absorbed power and the load shedding amount, wherein the preset functional relationship between the absorbed power and the load shedding amount includes taking the total amount of load shedding as the sum of the absorbed power of the energy storage system and the actual load shedding amount of the power system;

[0015] The absorbed power of the energy storage system is adjusted to the target absorbed power to stabilize the voltage of the power system.

[0016] In a feasible implementation, determining the second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system includes:

[0017] If the first charge-discharge state of the energy storage system is a discharge state and the active output instruction is greater than 0, determining that the second charge-discharge state of the energy storage system is a discharge state;

[0018] If the first charge-discharge state of the energy storage system is a discharge state and the active output instruction is less than 0, determining that the second charge-discharge state of the energy storage system is a charge state;

[0019] If the first charge-discharge state of the energy storage system is a charge state and the active output instruction is greater than 0, determining that the second charge-discharge state of the energy storage system is a discharge state;

[0020] If the first charge-discharge state of the energy storage system is a charging state and the active output instruction is less than 0, it is determined that the second charge-discharge state of the energy storage system is a charging state.

[0021] In a feasible implementation, the determining the total amount of load shedding of the power system by using the equivalent inertia center frequency of the power system includes:

[0022] Determine the equivalent inertia center frequency of the power system by using the number of load nodes of the power system, the equivalent coefficient and frequency of each node, and a preset equivalent inertia center frequency algorithm;

[0023] The equivalent inertia center frequency and a preset network-wide active unbalance algorithm are used to determine the network-wide active unbalance of the power system, where the network-wide active unbalance is the total amount of load shedding.

[0024] In a feasible implementation, the equivalent inertial center frequency algorithm includes the following mathematical expression:

[0025]

[0026] In the formula, f c is the equivalent inertial center frequency, N 0 is the number of nodes of load, H i and S i are the equivalent coefficients of node i, f i is the frequency of node i.

[0027] In a feasible implementation, the algorithm for the unbalanced active power of the entire network includes the following mathematical expression:

[0028]

[0029] Where ΔP is the unbalanced active power of the power system, f c is the equivalent inertial center frequency, N 0 is the number of nodes of load, H i and S i are the equivalent coefficients of node i, f i is the frequency of node i, f n is the rated frequency, ΔP i is the active power shortage of node i.

[0030] In a feasible implementation, determining the operating state of the power system according to the torque difference data of the induction motor includes:

[0031] After the fault is cleared, if the unstable slip in the torque difference data is less than the critical slip, it is determined that the operating state of the power system is load instability, and the unstable slip is the torque difference of the induction motor corresponding to the maximum value of the terminal voltage;

[0032] After the fault is cleared, if the unstable slip is greater than or equal to the critical slip, determining that the operating state of the power system is transient voltage stability;

[0033] Alternatively, after the fault is cleared, when the maximum torque difference value in the torque difference data is less than 0, it is determined that the operating state of the power system is load instability.

[0034] To achieve the above object, the second aspect of the present invention provides a control device for stabilizing voltage, the device comprising:

[0035] The device is applied to an electric power system, the electric power system includes an induction motor and an energy storage system, and the device includes:

[0036] A data acquisition module: used for acquiring operation data of the power system, wherein the operation data at least includes torque difference data of the induction motor;

[0037] A state determination module: used for determining the operating state of the power system according to the torque difference data of the induction motor, wherein the operating state at least includes load instability;

[0038] A load shedding amount determination module: used to determine the total amount of load shedding of the power system by using the equivalent inertia center frequency of the power system if the operating state is load instability; and to determine the first charge and discharge state of the energy storage system;

[0039] A voltage stabilization module is used to perform load shedding on the power system using the total load shedding amount, and determine a second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system, and control the energy storage system to change from the first charge and discharge state to the second charge and discharge state, so as to stabilize the voltage of the power system.

[0040] To achieve the above-mentioned purpose, the third aspect of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps shown in the first aspect and any feasible implementation method.

[0041] To achieve the above-mentioned purpose, the fourth aspect of the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps shown in the first aspect and any feasible implementation method.

[0042] The embodiments of the present invention have the following beneficial effects:

[0043] The present invention provides a control method for stabilizing voltage, which is applied to an electric power system, wherein the electric power system includes an induction motor and an energy storage system, and the method includes: obtaining the operating data of the electric power system, wherein the operating data includes at least the torque difference data of the induction motor; determining the operating state of the electric power system according to the torque difference data of the induction motor, wherein the operating state includes at least load instability; if the operating state is load instability, determining the total amount of load shedding of the electric power system using the equivalent inertia center frequency of the electric power system; and determining the first charge and discharge state of the energy storage system; performing load shedding processing on the electric power system using the total amount of load shedding, and determining the second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system, and controlling the energy storage system to change from the first charge and discharge state to the second charge and discharge state, so as to stabilize the voltage of the electric power system. Through the above method, an emergency control strategy for load shedding in which the energy storage system participates in protecting the safety of transient voltage is proposed, and in the case of voltage instability, the energy storage power source participates and cuts off part of the load at the same time, which can not only reduce the amount of load shedding, but also improve the stability of transient voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] in:

[0046] Figure 1 This is a flow chart of a method for controlling a stable voltage according to an embodiment of the present invention;

[0047] Figure 2 Another flow chart of a method for controlling a stable voltage according to an embodiment of the present invention;

[0048] Figure 3 is a characteristic curve of the torque difference of an induction motor in an embodiment of the present invention;

[0049] Figure 4 It is a control model of an energy storage system in an embodiment of the present invention;

[0050] Figure 5 It is a schematic diagram of equal area investment of an energy storage system in an embodiment of the present invention;

[0051] Figure 6 It is a structural block diagram of a control device for stabilizing voltage in an embodiment of the present invention;

[0052] Figure 7 4 is a structural block diagram of a computer device in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] It should be noted that with the continuous expansion of the scale of the power system, the voltage level of the transmission line has gradually increased, and the proportion of intermittent energy such as wind power has also increased year by year. The voltage stability problem of the power system has become more and more prominent. Load shedding, as the last line of defense to prevent voltage instability, has received more and more attention. However, the traditional low-voltage load shedding method has been difficult to meet the needs of the actual system. It is necessary to seek an economical and efficient load shedding control method.

[0055] Voltage instability is a gradual process that originates from the weakest node in the system and then gradually spreads to nearby nodes. Low-voltage load shedding is a reliable measure to prevent voltage instability accidents in the power grid. As the third line of defense, it is an indispensable part of maintaining the safe and stable operation of the system. Therefore, studying the role of load shedding control in maintaining voltage stability and preventing voltage collapse is the most effective control measure to achieve transient voltage stability in the power system.

[0056] Among them, the energy storage system can improve the power quality of the power grid and alleviate the aggravation of the peak-to-valley difference of the power grid. The randomness and volatility of renewable energy have driven the large-scale configuration and operation of the energy storage system in the power system. Improving the power quality can be used as part of the "one machine, multiple uses" function of the energy storage system; while the energy storage system provides generalized reactive power regulation in the converter, the energy storage can provide active power regulation capabilities, and it also has an irreplaceable role in solving the voltage quality problems of medium and low voltage distribution networks. Therefore, making full use of the main body and converter resources of the energy storage system has a better regulation effect on the power quality problems of the power grid with active / reactive power, which can significantly reduce the repeated investment of new energy power stations, power grids and users, and has good economic efficiency. The rapid energy conversion capability of the energy storage power source absorbs the excess transient kinetic energy injected during the disturbance of the power system, controls the transient potential energy of the branch of the critical cut set in the system within a limited range, and realizes the effective conversion of kinetic energy and potential energy in the transient process of the power system.

[0057] Research shows that energy storage is several times more efficient than traditional frequency modulation power sources, and the frequency modulation capability of battery energy storage is 9 times that of thermal power units. Electrochemical energy storage has been used in a variety of power systems, and has gained a lot of experience in battery itself, integrated technology, coordinated operation, etc., and has formed a standard system, laying a solid foundation for the next larger-scale application. Battery energy storage will be the most promising frequency modulation method in the future.

[0058] When a large area of ​​power shortage occurs due to a fault in the receiving circuit, if the emergency control is insufficient, a large area power outage will occur. Therefore, low-frequency load reduction is the most effective measure to ensure system stability after the system shortage occurs. The most commonly used measure is load shedding, but shedding a large amount of load will cause significant economic losses to society. California, USA, had a major power system failure due to excessive growth of disaster load, and load shedding measures were taken, resulting in a large number of casualties. To avoid similar situations, energy storage systems can be used for peak regulation to alleviate the problem of power supply and demand caused by excessive system load, and greatly increase the flexibility of the power grid's load-bearing capacity.

[0059] The method for controlling the stable voltage shown in the present application is to invest in an energy storage system during the process of controlling the stable voltage of the power system so that the energy storage system participates in the process of voltage stabilization, thereby effectively alleviating the problem of power supply and demand imbalance caused by excessive system load, and greatly increasing the elasticity of the power grid's load-bearing capacity. Among them, the energy storage system includes but is not limited to energy storage devices such as energy storage batteries that have energy conversion capabilities. The specific method for controlling the stable voltage can refer to the following content.

[0060] See also Figure 1 , Figure 1 FIG. 1 is a flow chart of a method for controlling a stable voltage according to an embodiment of the present invention. Figure 1The method is applied to an electric power system, the electric power system includes an induction motor and an energy storage system, and the method includes the following steps:

[0061] 101. Acquire operation data of the power system, wherein the operation data at least includes torque difference data of the induction motor;

[0062] It should be noted that the control method for stable voltage shown in the present application is applied to a power system, which may be a power supply system, such as a power grid, and the power system at least includes an induction motor. The present application invests in an energy storage system during the control process of stable voltage, and the power system also includes an energy storage system. In order to determine whether the voltage of the power system is stable, the operating data of the power system is first obtained. The operating data is used to reflect the changes in power parameters when the power system is running. The power parameters include but are not limited to the torque difference data of the induction motor and the charge and discharge data of the energy storage system, etc.

[0063] 102. Determine the operating state of the power system according to the torque difference data of the induction motor, wherein the operating state at least includes load instability;

[0064] Furthermore, after obtaining the above-mentioned operation data, the operation status of the system can be evaluated through the operation data, such as whether there is a fault, whether the voltage is stable, whether the load is stable, etc. Among them, the induction motor is the main component of the power system and the most important dynamic load. Its dynamic characteristics have a significant impact on the transient process of the power system. Therefore, this application judges the operation status of the power system through the torque difference data. Specifically, according to the torque difference data of the induction motor, the operation status of the power system is determined, and the operation status includes but is not limited to load instability or transient voltage stability. If the operation status of the power system is in a load instability state, step 103 is executed to perform voltage stability control.

[0065] 103. If the operating state is load instability, the total amount of load shedding of the power system is determined by using the equivalent inertia center frequency of the power system; and the first charge and discharge state of the energy storage system is determined;

[0066] It should be noted that if the operating state of the power system is in a load instability state, that is, the operating state is load instability, the transient voltage is restored to stability through the control method of load shedding. Specifically, the total load shedding of the power system can be determined by the equivalent inertia center frequency of the power system. Furthermore, when shedding the load, the present application will also determine the first charge and discharge state of the energy storage system to put the energy storage system into the process of transient voltage restoration and stability. Among them, the first charge and discharge state is used to reflect the working state of the energy storage system, and the charge and discharge state includes a charging state or a discharging state. The first charge and discharge state also represents the working state of the energy storage system before the load is sheared.

[0067] 104. Perform load shedding on the power system using the total load shedding amount, determine a second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system, and control the energy storage system to change from the first charge and discharge state to the second charge and discharge state, so as to stabilize the voltage of the power system.

[0068] Finally, the power system is subjected to load shedding by using the above-mentioned total load shedding amount, and then after the power system is disturbed, that is, after the load is shedding, the energy storage system is controlled to participate in the stabilization process of the transient voltage of the power system according to the first charge-discharge state and the active output instruction of the energy storage system. Specifically, the power system is subjected to load shedding by using the total load shedding amount, and the second charge-discharge state of the energy storage system is determined according to the first charge-discharge state and the active output instruction of the energy storage system, and the energy storage system is controlled to change from the first charge-discharge state to the second charge-discharge state, so as to stabilize the voltage of the power system. Among them, the second charge-discharge state is the working state of the energy storage system after the power system is disturbed.

[0069] The present invention provides a control method for stabilizing voltage, which is applied to an electric power system, wherein the electric power system includes an induction motor and an energy storage system, and the method includes: obtaining the operating data of the electric power system, wherein the operating data includes at least the torque difference data of the induction motor; determining the operating state of the electric power system according to the torque difference data of the induction motor, wherein the operating state includes at least load instability; if the operating state is load instability, determining the total amount of load shedding of the electric power system using the equivalent inertia center frequency of the electric power system; and determining the first charge and discharge state of the energy storage system; performing load shedding processing on the electric power system using the total amount of load shedding, and determining the second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system, and controlling the energy storage system to change from the first charge and discharge state to the second charge and discharge state, so as to stabilize the voltage of the electric power system. Through the above method, an emergency control strategy for load shedding in which the energy storage system participates in protecting the safety of transient voltage is proposed, and in the case of voltage instability, the energy storage power source participates and cuts off part of the load at the same time, which can not only reduce the amount of load shedding, but also improve the stability of transient voltage.

[0070] See also Figure 2 , Figure 2 FIG. 4 is another flow chart of a method for controlling a stable voltage according to an embodiment of the present invention. Figure 2 The method is applied to an electric power system, the electric power system includes an induction motor and an energy storage system, and the method includes the following steps:

[0071] 201. Acquire operation data of the power system, wherein the operation data at least includes torque difference data of the induction motor;

[0072] 202. Determine the operating state of the power system according to the torque difference data of the induction motor, wherein the operating state at least includes load instability;

[0073] It should be noted that step 201 and step 202 are Figure 1 The contents of steps 101 and 102 are similar, and are not described here to avoid repetition. For details, please refer to the aforementioned Figure 1 The contents of steps 101 and 102 are shown.

[0074] In a feasible implementation, step 202 may include steps A1 to A2 or B1:

[0075] A1. After the fault is cleared, if the unstable slip in the torque difference data is less than the critical slip, it is determined that the operating state of the power system is load instability, and the unstable slip is the torque difference of the induction motor corresponding to the maximum value of the terminal voltage;

[0076] A2. After the fault is cleared, if the unstable slip is greater than or equal to the critical slip, the operating state of the power system is determined to be transient voltage stability; or,

[0077] B1. After the fault is cleared, when the maximum torque difference value in the torque difference data is less than 0, it is determined that the operating state of the power system is load instability.

[0078] It should be noted that the system instability is judged according to the stable state of the induction motor load. The criterion is to judge the stability of the load by comparing the change of the induction motor slip after the disturbance, and then judge whether the transient voltage is unstable. Among them, the voltage instability in the local area causes the system power characteristic curve to decrease, such as Figure 3 As shown, Figure 3 is a characteristic curve of the torque difference of an induction motor in an embodiment of the present invention, wherein, given the terminal voltage T m =T e , a is the stable operating point of the induction motor, b is the unstable operating point of the induction motor, Figure 3It can be seen that the unbalanced energy that can be absorbed is greatly reduced, and the transient voltage is unstable.

[0079] In order to avoid the occurrence of mis-cutting or over-cutting, the system operation status is accurately judged and the transient voltage stability is judged by the proposed criterion, that is, after the fault of the power system is cleared, if the terminal voltage is at the maximum value, the corresponding unstable slip S us(Umac) m , then the load is unstable, otherwise the system is transiently voltage stable, where S m Further, after the fault is cleared, if the torque difference ΔT reaches the maximum value ΔT max When ΔT max <0, that is, the rotor is still decelerating, then the load is unstable, that is, when the maximum torque difference value in the torque difference data is less than 0, it is determined that the operating state of the power system is load instability.

[0080] 203. If the operating state is load instability, the total amount of load shedding of the power system is determined by using the equivalent inertia center frequency of the power system; and the first charge and discharge state of the energy storage system is determined;

[0081] It should be noted that step 203 and Figure 1 The contents of step 103 are similar, and are not described here to avoid repetition. For details, please refer to the aforementioned Figure 1 The content of step 103 is shown.

[0082] In a feasible implementation, the stability of the induction motor load bus voltage is judged according to known criteria to determine the load state at different fault removal times. The instability of the load node after the fault is removed is judged according to the transient voltage stability judgment basis. For the locally unstable load, the node with a more serious instability state is selected for load shedding control. The total load shedding control amount required for emergency control measures is calculated, and then the equivalent inertia center frequency of the power system is used to determine the total load shedding amount of the power system, including the following steps C1 to C2:

[0083] C1. Determine the equivalent inertia center frequency of the power system by using the number of load nodes of the power system, the equivalent coefficient and frequency of each node, and a preset equivalent inertia center frequency algorithm;

[0084] C2. Determine the total network active unbalance amount of the power system by using the equivalent inertia center frequency and a preset total network active unbalance amount algorithm, wherein the total network active unbalance amount is the total amount of load shedding.

[0085] Exemplarily, the above equivalent inertial center frequency algorithm includes the following mathematical expression (1):

[0086] ​

[0087] In the formula, f c is the equivalent inertial center frequency, N 0 is the number of nodes of the load, H i and S i are the equivalent coefficients of node i, f i is the frequency of node i.

[0088] Exemplarily, the above-mentioned algorithm for the unbalanced active power of the entire network includes the following mathematical expression (2):

[0089]

[0090] Where ΔP is the unbalanced active power of the power system, f c is the equivalent inertial center frequency, N 0 is the number of nodes of the load, H i and S i are the equivalent coefficients of node i, f i is the frequency of node i, f n is the rated frequency, ΔP i is the active power shortage of node i.

[0091] Then, after the disturbance occurs, the equivalent inertial center frequency f is calculated by formula (1): c , by obtaining df c / dt, the unbalanced active power of the whole network ΔP can be obtained from formula (2), that is, the total load that needs to be removed by the system.

[0092] 204. Perform load shedding processing on the power system using the total load shedding amount, and determine a second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system, and control the energy storage system to change from the first charge and discharge state to the second charge and discharge state, so as to stabilize the voltage of the power system;

[0093] It should be noted that step 204 and Figure 1 The contents of step 104 are similar, and will not be described here to avoid repetition. For details, please refer to the aforementioned Figure 1 The content of step 104 is shown.

[0094] In a feasible implementation, determining the second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system includes the following steps D1 to D4:

[0095] D1. If the first charge-discharge state of the energy storage system is a discharge state and the active output instruction is greater than 0, then determining that the second charge-discharge state of the energy storage system is a discharge state;

[0096] D2. If the first charge-discharge state of the energy storage system is a discharge state and the active output instruction is less than 0, determining that the second charge-discharge state of the energy storage system is a charge state;

[0097] D3. If the first charge-discharge state of the energy storage system is a charge state and the active output instruction is greater than 0, determining that the second charge-discharge state of the energy storage system is a discharge state;

[0098] D4. If the first charge-discharge state of the energy storage system is a charging state and the active output instruction is less than 0, it is determined that the second charge-discharge state of the energy storage system is a charging state.

[0099] It should be noted that if the first charge and discharge state of the energy storage system, that is, the current working state, is in the discharge state, and the remaining regulation capacity meets the requirements, two cases are discussed: [1.1] Assuming that the energy storage is currently in the discharge state, when the system is disturbed, the active output command is greater than 0, then the energy storage system needs to maintain the discharge state, so its second charge and discharge state is determined to be the discharge state, specifically refer to the following formulas (3) and (4):

[0100] k·Δδ=P f,max -P f =ΔP S (3)

[0101]

[0102] Where, k is the active power regulation coefficient; P f,max is the maximum discharge power of energy storage, P f The active power of the energy storage battery participating in auxiliary frequency regulation; δ u is the stable equilibrium point of the system after no energy storage measures are put into use; δ c is the rotor angle when the fault is removed; Δδ is the active power angle difference; E is the output of energy storage, ΔP S is the actual energy storage power.

[0103] [1.2] Assuming that the energy storage is currently in a discharging state, after a disturbance occurs in the system, its active output command is less than 0, and the energy storage system is converted into a charging state. Therefore, its second charge-discharge state is determined to be a charging state. For details, refer to the following equations (5) and (6).

[0104] k·Δδ=P c,max +P f =ΔP S (5)

[0105]

[0106] Where, k is the active power regulation coefficient; P c,maxis the maximum charging power of energy storage, P f The active power of the energy storage battery participating in auxiliary frequency regulation; δ u is the stable equilibrium point of the system after no energy storage measures are put into use; δ c is the rotor angle when the fault is removed; Δδ is the active power angle difference; E is the output of energy storage, ΔP S is the actual energy storage power.

[0107] Furthermore, if the first charge-discharge state of the energy storage system, that is, the current working state, is in the charging state, its remaining regulation capacity meets the requirements. The same two cases are discussed: [2.1] Assuming that the energy storage is currently in the charging state, when the system is disturbed, its active output is greater than 0, and the energy storage system needs to be transformed into the discharging state, so its second charge-discharge state is determined to be the discharging state. For details, refer to the following equations (7) and (8):

[0108] k·Δδ=P f,max +P c =ΔP S (7)

[0109]

[0110] Where, k is the active power regulation coefficient; P f,max is the maximum discharge power of the energy storage battery, P f The active power of the energy storage battery participating in auxiliary frequency regulation; δ u is the stable equilibrium point of the system after no energy storage measures are put into use; δ c is the rotor angle when the fault is cleared; Δδ is the active power angle difference, ΔP S is the actual energy storage power.

[0111] [2.2] Assuming that the energy storage is currently in a charging state, when the system is disturbed, its active output is still less than 0. The energy storage system needs to continue to maintain the charging state and determine that its second charge-discharge state is the charging state. For details, refer to the following equations (9) and (10).

[0112] k·Δδ=P c,max -P c =ΔP S (9)

[0113]

[0114] Where, k is the active power regulation coefficient; P c,max is the maximum charging power of energy storage, P f The active power of the energy storage battery participating in auxiliary frequency regulation; δ u is the stable equilibrium point of the system after no energy storage measures are put into use; δ c is the rotor angle when the fault is removed; Δδ is the active power angle difference; E is the output of energy storage, ΔPS is the actual energy storage power.

[0115] 205. Determine the target absorbed power of the energy storage system and the actual load shedding amount of the power system by using the total amount of load shedding and the preset functional relationship between the absorbed power and the load shedding amount, wherein the preset functional relationship between the absorbed power and the load shedding amount includes taking the total amount of load shedding as the sum of the absorbed power of the energy storage system and the actual load shedding amount of the power system;

[0116] 206. Adjust the absorbed power of the energy storage system to the target absorbed power to stabilize the voltage of the power system.

[0117] Furthermore, after obtaining the total load shedding ΔP, the target absorbed power of the energy storage system and the actual load shedding of the power system can be determined by the preset absorbed power and load shedding function relationship, wherein the total load shedding is taken as the sum of the absorbed power of the energy storage system and the actual load shedding of the power system, that is, the total load shedding of the single-machine infinite equivalent system is regarded as the power MΔP absorbed by the energy storage power source S The sum of the load shedding amount MΔP′ after the fault.

[0118] That is, centralized load shedding control measures are adopted, the total load shedding capacity of the system is calculated according to the system shortage situation, and the energy storage power supply is put into use at the same time as the load shedding, and the system active power is adjusted at the same time to obtain the actual load shedding capacity and the absorbed power of the energy storage power supply. For details, please refer to the following formula (11):

[0119] ΔP=MΔP′+MΔP S (11)

[0120] Where, ΔP′ is the actual load shedding amount, ΔP S is the power absorbed by the energy storage power source (that is, the actual energy storage power), and M is the equivalent conversion coefficient that regards the total load shedding of a single-machine infinite equivalent system as the power absorbed by the energy storage power source or the actual load shedding.

[0121] Furthermore, after the system becomes unstable, the energy storage power supply and load shedding joint control measures are carried out, and the energy storage power supply absorption power and the actual load shedding amount are calculated respectively by formula (11). The absorption power of the energy storage system is adjusted to the target absorption power to stabilize the voltage of the power system.

[0122] The present invention provides a control method for stabilizing voltage. The method is applied to an electric power system. The electric power system includes an induction motor and an energy storage system. The method includes: obtaining operation data of the electric power system, the operation data at least including torque difference data of the induction motor; determining the operation state of the electric power system according to the torque difference data of the induction motor, the operation state at least including load instability; if the operation state is load instability, determining the total amount of load shedding of the electric power system by using the equivalent inertia center frequency of the electric power system; and determining a first charge and discharge state of the energy storage system; performing load shedding processing on the electric power system by using the total amount of load shedding, and determining the load shedding of the electric power system according to the first charge and discharge state and the energy storage system. The active output instruction of the system is used to determine the second charge and discharge state of the energy storage system, and the energy storage system is controlled to change from the first charge and discharge state to the second charge and discharge state to stabilize the voltage of the power system; the target absorption power of the energy storage system and the actual load shedding amount of the power system are determined by using the total amount of load shedding and the preset absorption power and load shedding function relationship, and the preset absorption power and load shedding function relationship includes taking the total amount of load shedding as the sum of the absorption power of the energy storage system and the actual load shedding amount of the power system; adjusting the absorption power of the energy storage system to the target absorption power to stabilize the voltage of the power system. Through the above method, an emergency control strategy for load shedding in which the energy storage system participates in protecting the transient voltage safety is proposed. When the energy storage power source participates in the case of voltage instability, part of the load is cut off, which can not only reduce the load shedding amount, but also improve the transient voltage stability.

[0123] To better illustrate the present application, the implementation process of the present application is described below in conjunction with the simulation process. Please refer to the following content:

[0124] Taking the instability state of the induction motor load in the 36-node power system as an example, the energy storage power supply participates in the simultaneous shedding of part of the load in the instability state, and studies how the energy storage power supply improves the transient voltage stability under load shedding.

[0125] Firstly, a non-delay BESS electromechanical transient model with battery charging and discharging power limit and charging and discharging times limit is designed. The model interface is developed using the node current injection method. The model mainly consists of a battery pack, an IGBT-based grid-connected inverter (PCS) and a monitoring and control system. Figure 4 As shown, Figure 4 This is a control model of an energy storage system in an embodiment of the present invention.

[0126] Among them, the PCS control system uses the difference ΔU and Δω between the voltage U and the power angle ω obtained by the power grid generator and the set standard value as input to perform PI control, and obtains the active power P through the outer loop controller. set and reactive power Q set , which is used as the input of the internal control link, refer to the following equations (12) and (13).

[0127]

[0128]

[0129] Where, T p is the PCS active power response time constant; T q is the reactive power response time constant of PCS; P is the active power output of the energy storage battery; Q is the reactive power output of the energy storage battery, P set is the active power and Q set is the reactive power and S is the input quantity.

[0130] Step 1: According to the charging and discharging power of the battery, the upper and lower limits of the battery charging and discharging are set by the energy storage active output instruction, and the active output power of the converter is limited to obtain the restriction conditions of the energy storage battery; from the perspective of battery safety and life, the charging and discharging depth is constrained. When the battery pack SOC exceeds 90% of the capacity, the battery can only be discharged but not charged; when the discharge SOC is lower than 10%, in order to protect the battery life, the discharge is stopped and only charging is performed, refer to the following equations (14) and (15).

[0131] Energy storage battery charging:

[0132]

[0133] Energy storage battery discharge:

[0134]

[0135] Where, δ is the self-discharge rate of the energy storage battery; E c is the rated capacity of the energy storage battery, P bat_ch , P bat_dh Charging and discharging power for energy storage batteries; η bat is the working efficiency of the energy storage battery; η ch , η dh is the PCS charging and discharging efficiency, t is the time

[0136] Furthermore, the output power of the converter is also limited, so the reactive power support capacity cannot be increased infinitely and should be limited according to the actual situation. Refer to the following formula (16):

[0137]

[0138] Where V AC is the voltage amplitude on the AC side; I maxAC is the current amplitude on the AC side. P is the active power output by the energy storage battery, Q max The maximum value of reactive power output by the energy storage battery.

[0139] Step 2: Based on the extended equal area criterion (EEAC), the energy storage control is equivalent to a trapezoid, P max is the maximum charge and discharge power in the energy storage process, P is the charge and discharge power in the current state of the energy storage, Δδ is the power angle difference from the energy storage input to the constant power angle, and k is the energy storage charge and discharge rate. The output of the energy storage power supply is quantified as follows: Figure 5 , Figure 5 It is a schematic diagram of equal area investment in an energy storage system according to an embodiment of the present invention.

[0140] Furthermore, assuming that the energy storage is currently in a discharging state and the remaining regulation capacity meets the requirements, when the system is disturbed, the active output command is greater than 0, and the energy storage system needs to maintain a discharging state, specifically referring to expressions (3) and (4).

[0141] If the energy storage is currently in a discharging state, when a disturbance occurs in the system, its active output is less than 0, and the energy storage system is converted into a charging state. For details, refer to expressions (5) and (6).

[0142] Furthermore, assuming that the energy storage is currently in a charging state, when a disturbance occurs in the system, its active output is greater than 0, and the energy storage system needs to be converted into a discharging state. For details, refer to expressions (7) and (8).

[0143] Assuming that the energy storage is currently in a charging state, its remaining regulation capacity meets the requirements. When the system is disturbed, its active output is still less than 0, and the energy storage system needs to continue to maintain a charging state. For details, refer to expressions (9) and (10).

[0144] Step 3: Determine the instability of the system based on the stable state of the induction motor load. The criterion is to determine the stability of the load by comparing the change in the induction motor slip after the disturbance, and then determine whether the transient voltage is unstable. The voltage instability in the local area causes the system power characteristic curve to decrease. Figure 3 , the unbalanced energy that can be absorbed is greatly reduced, and the transient voltage becomes unstable.

[0145] Furthermore, after the fault is cleared, if the terminal voltage is at a maximum value, the corresponding unstable slip S us(Umax) m , then the load is unstable, otherwise the system is transient voltage stable, where S m It is a critical slip.

[0146] Furthermore, if the torque difference reaches a maximum value after the fault is cleared, the rotor still decelerates, that is, ΔT max <0, the load is unstable.

[0147] ​In step 4, centralized load shedding control measures should be adopted. The total load shedding capacity of the system should be calculated according to the system shortage situation, referring to expressions (1) and (2). The energy storage power supply should be put into use at the same time as the load shedding, and the system active power should be adjusted at the same time to obtain the actual load shedding capacity and the absorbed power of the energy storage power supply, referring to equation (11).

[0148] Step 5: Set up different emergency control schemes, conduct experimental comparisons on different schemes under the same instability situation, observe the voltage amplitude, frequency, etc., and restore the voltage stability under emergency control, and calculate and analyze the load shedding amount.

[0149] Step 6, again determine the stability of the induction motor load after the emergency control. If the system continues to be unstable, continue the emergency control until the system recovers stability.

[0150] In order to verify the feasibility of the present application, experiments were set up to compare emergency control of load shedding, emergency control of the system by energy storage power supply, and emergency control of transient voltage by energy storage power supply and load shedding at the same time. Experimental simulation was performed on the weak nodes determined above in the 36-node system.

[0151] The voltage amplitude and frequency fluctuations were observed based on the experimental results, as well as the time it takes for the experimental results to return to stability in different schemes, verifying that this patent can reduce the amount of load shedding while improving transient voltage stability.

[0152] This application proposes an emergency load shedding control strategy in which energy storage power supplies participate in protecting transient voltage safety. Based on the EEAC principle, the energy storage model is quantitatively analyzed, the total load shedding amount is calculated under voltage instability conditions, the instability state of the induction motor load of the 36-node system is determined, and the energy storage power supply participates in the simultaneous shedding of part of the load under instability conditions. The energy storage power supply is studied to improve the transient voltage stability under load shedding conditions, and the impact of load shedding and energy storage backup power supply on the transient stability of the system is analyzed.

[0153] See also Figure 6 , Figure 6 FIG. 1 is a structural block diagram of a voltage stabilization control device according to an embodiment of the present invention. Figure 6 The device is applied to an electric power system, the electric power system includes an induction motor and an energy storage system, and the device includes:

[0154] Data acquisition module 601: used to acquire operation data of the power system, wherein the operation data at least includes torque difference data of the induction motor;

[0155] A state determination module 602 is used to determine the operation state of the power system according to the torque difference data of the induction motor, wherein the operation state at least includes load instability;

[0156] The load shedding amount determination module 603 is used to determine the total load shedding amount of the power system by using the equivalent inertia center frequency of the power system if the operating state is load instability; and determine the first charge and discharge state of the energy storage system;

[0157] Voltage stabilization module 604: used to perform load shedding processing on the power system using the total load shedding amount, and determine the second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system, and control the energy storage system to change from the first charge and discharge state to the second charge and discharge state, so as to stabilize the voltage of the power system.

[0158] It should be noted that Figure 6 The functions of each module in the device shown are Figure 1 The contents of each step in the method shown are similar. To avoid repetition, they are not described here. For details, please refer to the aforementioned Figure 1 The content of each step in the method shown.

[0159] The present invention provides a control device for stabilizing voltage, which is applied to an electric power system, and the electric power system includes an induction motor and an energy storage system, and the device includes: a data acquisition module: used to acquire the operation data of the electric power system, and the operation data at least includes the torque difference data of the induction motor; a state determination module: used to determine the operation state of the electric power system according to the torque difference data of the induction motor, and the operation state at least includes load instability; a load removal amount determination module: used to determine the total amount of load removal of the electric power system by using the equivalent inertia center frequency of the electric power system if the operation state is load instability; and determine the first charge and discharge state of the energy storage system; a voltage stabilization module: used to perform load removal processing on the electric power system by using the total amount of load removal, and determine the second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system, and control the energy storage system from the first charge and discharge state to the second charge and discharge state, so as to stabilize the voltage of the electric power system. Through the above method, an emergency control strategy for load removal in which the energy storage system participates in protecting the safety of transient voltage is proposed. When the energy storage power source participates in the voltage instability, while removing part of the load, it can not only reduce the load removal amount, but also improve the transient voltage stability.

[0160] Figure 7 FIG. 1 shows an internal structure diagram of a computer device in an embodiment. The computer device may be a terminal or a server. Figure 7As shown, the computer device includes a processor, a memory and a network interface connected via a system bus. The memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium of the computer device stores an operating system and may also store a computer program. When the computer program is executed by the processor, the processor can implement the above method. The internal memory may also store a computer program. When the computer program is executed by the processor, the processor can implement the above method. Those skilled in the art can understand that Figure 7 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0161] In one embodiment, a computer device is provided, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the following steps: Figure 1 or Figure 2 The steps of the method are shown.

[0162] In one embodiment, a computer-readable storage medium is provided, which stores a computer program. When the computer program is executed by a processor, the processor performs the following steps: Figure 1 or Figure 2 The steps of the method are shown.

[0163] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0164] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0165] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for controlling a stable voltage, characterized in that: The method is applied to an electric power system, the electric power system includes an induction motor and an energy storage system, and the method includes: Acquiring operation data of the power system, the operation data at least including torque difference data of the induction motor; determining an operating state of the power system according to the torque difference data of the induction motor, wherein the operating state at least includes load instability; If the operating state is load instability, the total amount of load shedding of the power system is determined using the equivalent inertia center frequency of the power system; and the first charge and discharge state of the energy storage system is determined; Performing load shedding processing on the power system using the total load shedding amount, and determining a second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system, and controlling the energy storage system to change from the first charge and discharge state to the second charge and discharge state, so as to stabilize the voltage of the power system; Wherein, determining the total amount of load shedding of the power system by using the equivalent inertia center frequency of the power system comprises: Determine the equivalent inertia center frequency of the power system by using the number of load nodes of the power system, the equivalent coefficient and frequency of each node, and a preset equivalent inertia center frequency algorithm; Determine the total network active unbalance amount of the power system by using the equivalent inertia center frequency and a preset total network active unbalance amount algorithm, wherein the total network active unbalance amount is the total amount of load shedding; Wherein, the equivalent inertial center frequency algorithm includes the following mathematical expression: ； The algorithm for the unbalanced active power of the entire network includes the following mathematical expression: ； In the formula, N 0 is the number of nodes under load, is the unbalanced active power of the power system, is the equivalent inertial center frequency, N 0 is the number of nodes under load, as well as are the equivalent coefficients of node i, is the frequency of node i, is the rated frequency, For Node i The meritorious vacancies.

2. The method according to claim 1, characterized in that: The method further comprises: Determine the target absorbed power of the energy storage system and the actual load shedding amount of the power system by using the total amount of load shedding and the preset functional relationship between the absorbed power and the load shedding amount, wherein the preset functional relationship between the absorbed power and the load shedding amount includes taking the total amount of load shedding as the sum of the absorbed power of the energy storage system and the actual load shedding amount of the power system; The absorbed power of the energy storage system is adjusted to the target absorbed power to stabilize the voltage of the power system.

3. The method according to claim 1, characterized in that: The determining, according to the first charge-discharge state and the active output instruction of the energy storage system, a second charge-discharge state of the energy storage system comprises: If the first charge-discharge state of the energy storage system is a discharge state and the active output instruction is greater than 0, determining that the second charge-discharge state of the energy storage system is a discharge state; If the first charge-discharge state of the energy storage system is a discharge state and the active output instruction is less than 0, determining that the second charge-discharge state of the energy storage system is a charge state; If the first charge-discharge state of the energy storage system is a charge state and the active output instruction is greater than 0, determining that the second charge-discharge state of the energy storage system is a discharge state; If the first charge-discharge state of the energy storage system is a charging state and the active output instruction is less than 0, it is determined that the second charge-discharge state of the energy storage system is a charging state.

4. The method according to claim 1, characterized in that: Determining the operating state of the power system according to the torque difference data of the induction motor includes: After the fault is cleared, if the unstable slip in the torque difference data is less than the critical slip, it is determined that the operating state of the power system is load instability, and the unstable slip is the torque difference of the induction motor corresponding to the maximum value of the terminal voltage; After the fault is cleared, if the unstable slip is greater than or equal to the critical slip, determining that the operating state of the power system is transient voltage stability; Alternatively, after the fault is cleared, when the maximum torque difference value in the torque difference data is less than 0, it is determined that the operating state of the power system is load instability.

5. A control device for stabilizing voltage, characterized in that: The device is applied to an electric power system, the electric power system includes an induction motor and an energy storage system, and the device includes: A data acquisition module: used for acquiring operation data of the power system, wherein the operation data at least includes torque difference data of the induction motor; A state determination module: used for determining the operating state of the power system according to the torque difference data of the induction motor, wherein the operating state at least includes load instability; A load shedding amount determination module: used to determine the total amount of load shedding of the power system by using the equivalent inertia center frequency of the power system if the operating state is load instability; and to determine the first charge and discharge state of the energy storage system; A voltage stabilization module: used to perform load shedding processing on the power system using the total load shedding amount, and determine the second charge and discharge state of the energy storage system according to the first charge and discharge state and the active output instruction of the energy storage system, and control the energy storage system to change from the first charge and discharge state to the second charge and discharge state, so as to stabilize the voltage of the power system; The load shedding amount determination module is specifically used to: determine the equivalent inertia center frequency of the power system by using the number of load nodes of the power system, the equivalent coefficient and frequency of each node, and a preset equivalent inertia center frequency algorithm; determine the total network active unbalance amount of the power system by using the equivalent inertia center frequency and a preset total network active unbalance amount algorithm, wherein the total network active unbalance amount is the total amount of load shedding; Wherein, the equivalent inertial center frequency algorithm includes the following mathematical expression: ； The algorithm for the unbalanced active power of the entire network includes the following mathematical expression: ； In the formula, N 0 is the number of nodes under load, is the unbalanced active power of the power system, is the equivalent inertial center frequency, N 0 is the number of nodes under load, as well as are the equivalent coefficients of node i, is the frequency of node i, is the rated frequency, For Node i The meritorious vacancies.

6. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 4.

7. A computer device comprising a memory and a processor, characterized in that: The memory stores a computer program, and when the computer program is executed by the processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 4.

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