Distributed new energy low voltage ride through control method and system

Abstract

The application provides a distributed new energy low-voltage ride-through control method and system, the method comprises the following steps: after obtaining induction motor parameters and distributed new energy parameters, distributed new energy power output models and induction motor Thevenin equivalent models are established respectively; according to the power output model, Thevenin equivalent model, induction motor parameters, slip and terminal voltage, a slip model and active power model of main grid feed-in are established respectively; the solution of the slip model is substituted into the active power model, the critical instability minimum voltage and the region where the operating point is located after fault clearing are determined according to the established critical instability minimum voltage model; and based on the defined low-voltage ride-through control rule, the critical instability minimum voltage, the terminal voltage and the region where the operating point is located after fault clearing are used for low-voltage ride-through control. The method and system adopt different low-voltage ride-through controls according to different conditions, and the stability of the power system is improved.

Description

Technical Field

[0001] This invention relates to the field of power system voltage control technology, and more specifically, to a method and system for controlling low voltage ride-through of distributed renewable energy sources. Background Technology

[0002] The efficient development and utilization of new energy sources is a crucial support for sustainable energy development. In recent years, the installed capacity of distributed new energy sources has experienced explosive growth. However, their voltage support capability is weaker than that of traditional generators. When the grid voltage drops beyond expectations, continuous low-voltage operation will damage equipment safety, and grid disconnection will affect grid stability and even cause grid collapse.

[0003] Low-voltage ride-through (LVRT) control technology is one of the key technologies for solving this problem. When distributed renewable energy sources face low voltage from the grid, this technology can protect the safety of the distributed renewable energy sources themselves while reducing their impact on the grid, and even providing support capabilities. Many countries' technical standards require distributed renewable energy sources to have a certain level of low-voltage ride-through capability when connected to the grid, but the specific requirements vary. Currently, very few studies in the industry provide theoretical support for these standards and requirements, or assess their effectiveness from a voltage stability perspective. Summary of the Invention

[0004] To address the technical problem of the lack of standards and requirements for evaluating the low-voltage ride-through capability of distributed renewable energy sources as the scale of renewable energy integration increases, this invention provides a distributed renewable energy low-voltage ride-through control method and system. This method aims to improve the stability of the power system by employing different low-voltage ride-through controls based on different conditions, while considering the transient voltage support capability and equipment safety.

[0005] According to one aspect of the present invention, a distributed renewable energy low-voltage ride-through control method is provided, the method comprising: Acquire the parameters of the induction motor and the parameters of the distributed renewable energy in the power system connected to the distributed renewable energy source, wherein the parameters of the induction motor include mechanical torque; A distributed renewable energy power output model is established, wherein the distributed renewable energy power output model is used to construct the relationship between the active power output of the distributed renewable energy and the terminal voltage, and the relationship between the reactive power output and the terminal voltage, respectively, based on the distributed renewable energy parameters. A Thevenin equivalent model of an induction motor is established, wherein the Thevenin equivalent model is used to calculate and determine the equivalent motor parameters based on the induction motor parameters, and to construct the relationship between the Thevenin equivalent voltage and the terminal voltage based on the induction motor parameters; An active power absorption model for an induction motor is established, wherein the active power absorption model is used to construct the relationship between the active power absorption of the induction motor and the Thevenin equivalent voltage, terminal voltage, and slip rate based on the equivalent motor parameters and the induction motor parameters. An electromagnetic torque model for an induction motor is established, wherein the electromagnetic torque model is used to construct the relationship between the electromagnetic torque of the induction motor and the Thevenin equivalent voltage and slip rate based on the equivalent motor parameters and the induction motor parameters. A slip rate model is established based on the mechanical torque, wherein the slip rate model is used to construct the relationship between the unstable slip rate and the terminal voltage, and the stable slip rate and the terminal voltage, respectively, when the electromagnetic torque and the mechanical torque of the induction motor are equal. Establish an active power model fed into the main grid, wherein the active power model fed into the main grid is used to construct the relationship between the active power fed into the main grid and the absorbed active power and the active power output by distributed new energy sources. A critical instability minimum voltage model is established, wherein the critical instability minimum voltage model is used to solve for the hook-shaped curve generated from the instability slip rate curve and the stable slip rate curve, and to determine the critical instability minimum voltage based on the hook-shaped curve. The model also determines the region of the operating point after fault clearance based on the boundary line between the hook-shaped curve and the critical instability minimum voltage. The instability slip rate curve and the stable slip rate curve are located on a coordinate plane with the active power fed by the main grid as the abscissa and the induction motor terminal voltage as the ordinate. The instability slip rate curve and the stable slip rate curve are obtained by substituting the instability slip rate and the stable slip rate from the slip rate model into the active power model fed by the main grid, respectively, and ensuring that the terminal voltage is within a defined range. The curve obtained by taking arbitrary values ​​reflects the relationship between the active power fed into the main grid and the generator terminal voltage. The critical instability minimum voltage is the minimum generator terminal voltage corresponding to the hook-shaped curve. The critical instability minimum voltage boundary line is a straight line passing through the coordinate point corresponding to the critical instability minimum voltage and parallel to the horizontal axis. The area where the operating point is located after the fault is cleared includes a stable area, an unstable area, and a multistate area. The multistate area is the area enclosed by the hook-shaped curve. The stable area is the area located outside the right side of the instability slip rate curve and located at and above the critical instability minimum voltage boundary line. The area on the coordinate plane other than the hook-shaped curve, the multistate area, and the stable area is the unstable area. Based on the defined low-voltage ride-through control rules, low-voltage ride-through control is performed according to the critical minimum voltage of instability, the terminal voltage of the operating point after the fault is cleared, and the region in which it is located.

[0006] According to another aspect of the present invention, a distributed renewable energy low-voltage ride-through control system is provided, the system comprising: The data acquisition module is used to acquire the parameters of the induction motor and the parameters of the distributed new energy in the power system connected to the distributed new energy, wherein the parameters of the induction motor include mechanical torque; The first model module is used to establish a distributed renewable energy power output model, wherein the distributed renewable energy power output model is used to construct the relationship between the active power output of the distributed renewable energy and the terminal voltage, and the relationship between the reactive power output and the terminal voltage, respectively, based on the distributed renewable energy parameters. The second model module is used to establish the Thevenin equivalent model of the induction motor, wherein the Thevenin equivalent model is used to calculate and determine the equivalent motor parameters based on the induction motor parameters, and to construct the relationship between the Thevenin equivalent voltage and the terminal voltage based on the induction motor parameters. The third model module is used to establish the active power absorption model of the induction motor. The active power absorption model is used to construct the relationship between the active power absorption of the induction motor and the Thevenin equivalent voltage, terminal voltage and slip rate based on the equivalent motor parameters and the induction motor parameters. The fourth model module is used to establish an electromagnetic torque model of the induction motor, wherein the electromagnetic torque model is used to construct the relationship between the electromagnetic torque of the induction motor and the Thevenin equivalent voltage and slip rate based on the equivalent motor parameters and the induction motor parameters. The fifth model module is used to establish a slip rate model based on the mechanical torque. The slip rate model is used to construct the relationship between the unstable slip rate and the terminal voltage, and the stable slip rate and the terminal voltage, respectively, when the electromagnetic torque and the mechanical torque of the induction motor are equal. The sixth model module is used to establish an active power model fed into the main grid, wherein the active power model fed into the main grid is used to construct the relationship between the active power fed into the main grid and the absorbed active power and the active power output by distributed new energy sources. The seventh model module is used to establish a critical minimum voltage instability model. This model is used to solve for a hook-shaped curve generated from the instability slip rate curve and the stable slip rate curve, and to determine the critical minimum voltage instability based on the hook-shaped curve. It also determines the region where the operating point is located after fault clearance based on the boundary line between the hook-shaped curve and the critical minimum voltage instability. The instability slip rate curve and the stable slip rate curve are located on a coordinate plane with the active power fed by the main grid as the abscissa and the induction motor terminal voltage as the ordinate. The instability slip rate curve and the stable slip rate curve are obtained by substituting the instability slip rate and stable slip rate from the slip rate model into the active power model fed by the main grid, and ensuring that the terminal voltage is within a defined range. The curve obtained by taking arbitrary values ​​within the value range reflects the relationship between the active power fed into the main grid and the generator terminal voltage. The critical instability minimum voltage is the minimum generator terminal voltage corresponding to the hook-shaped curve. The critical instability minimum voltage boundary line is a straight line passing through the coordinate point corresponding to the critical instability minimum voltage and parallel to the horizontal axis. The region where the operating point is located after the fault is cleared includes a stable region, an unstable region, and a multistate region. The multistate region is the region enclosed by the hook-shaped curve. The stable region is the region located outside the right side of the instability slip rate curve and located on and above the critical instability minimum voltage boundary line. The region on the coordinate plane other than the hook-shaped curve, the multistate region, and the stable region is the unstable region. The ride-through control module is used to perform low-voltage ride-through control based on the defined low-voltage ride-through control rules, the critical instability minimum voltage, the terminal voltage of the operating point after the fault is cleared, and the area in which it is located.

[0007] According to another aspect of the present invention, a computer-readable storage medium is provided, the storage medium storing a computer program that, when executed by a processor, implements the methods described in any of the above aspects of the present invention.

[0008] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising: a processor; a memory for storing executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the method described in any of the preceding aspects of the present invention.

[0009] The present invention discloses a distributed renewable energy low-voltage ride-through control method and system. The method includes: acquiring the parameters of the induction motor and the distributed renewable energy in the power system connected to the distributed renewable energy, and then establishing a distributed renewable energy power output model and a Thevenin equivalent model of the induction motor, respectively; establishing an active power absorption model of the induction motor based on the Thevenin equivalent model, the induction motor parameters, slip, and terminal voltage; establishing a slip rate model based on the mechanical torque using the Thevenin equivalent model, the induction motor parameters, and slip; establishing an active power model fed into the main grid based on the distributed renewable energy power output model and the active power absorption model of the induction motor; substituting the solution of the slip rate model into the active power model fed into the main grid; determining the critical instability minimum voltage and the region where the operating point is located after fault clearance based on the established critical instability minimum voltage model; and performing low-voltage ride-through control based on the defined low-voltage ride-through control rules, the critical instability minimum voltage, the terminal voltage of the operating point after fault clearance, and the region where it is located. The method and system, taking into account both transient voltage support capability and equipment safety, employ different low-voltage ride-through controls based on different conditions to find the optimal transient voltage support, thereby further improving the stability of the power system. Attached Figure Description

[0010] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures: Figure 1 A flowchart of a distributed renewable energy low-voltage ride-through control method according to a preferred embodiment of the present invention; Figure 2 A schematic diagram of generating a Thevenin equivalent model based on a T-type equivalent model of an induction motor according to a preferred embodiment of the present invention; Figure 3 This is a schematic diagram of low voltage ride-through control according to a preferred embodiment of the present invention, where the terminal voltage at the operating point is below the critical instability minimum voltage after fault clearance. Figure 4 This is a schematic diagram of low voltage ride-through control according to a preferred embodiment of the present invention, where the terminal voltage at the operating point is above the minimum critical instability voltage after fault clearance. Figure 5 This is a schematic diagram of the structure of a distributed renewable energy low-voltage ride-through control system according to a preferred embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention. Detailed Implementation

[0011] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0012] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0013] Exemplary methods Figure 1 This is a flowchart of a distributed renewable energy low-voltage ride-through control method according to a preferred embodiment of the present invention. Figure 1 As shown, the distributed new energy low voltage ride-through control method described in this preferred embodiment starts from step 101.

[0014] In step 101, the parameters of the induction motor and the parameters of the distributed new energy in the power system connected to the distributed new energy are obtained, wherein the parameters of the induction motor include mechanical torque.

[0015] In this preferred embodiment, the induction motor parameters required for calculating the hook-shaped curve include stator resistance Rs, rotor resistance Rr, stator reactance Xs, rotor reactance Xr, excitation reactance Xm, and mechanical torque Tm. The obtained distributed renewable energy parameters are mainly control parameters used to calculate the low-voltage ride-through control of the active and reactive power output of the renewable energy source. These are divided into active power control parameters and reactive power control parameters. The active power control parameters include the active power-terminal voltage droop coefficient. Active current bias coefficient of distributed renewable energy sources before crossing the threshold Active current bias coefficient during crossing Reactive power control parameters include reactive current-terminal voltage droop coefficient. and reactive current bias coefficient during ride-through .

[0016] In step 102, a distributed renewable energy power output model is established, wherein the distributed renewable energy power output model is used to construct the relationship between the active power output of the distributed renewable energy and the terminal voltage, and the relationship between the reactive power output and the terminal voltage, respectively, based on the distributed renewable energy parameters.

[0017] Preferably, a distributed renewable energy power output model is established, wherein the expression of the distributed renewable energy power output model is: (1) (2) (3) In the formula, Active power generated by distributed renewable energy sources; Reactive power generated by distributed renewable energy sources; Operating mode; The terminal voltage during runtime t. Used according to Determine the first Active power under various operating modes Used according to Determine the first Reactive power under various operating modes; when At that time, the power output of distributed energy sources were as follows: (4) (5) In the formula, , and These represent the active power-terminal voltage droop coefficient, the active current bias coefficient of distributed renewable energy before crossing, and the active current bias coefficient during crossing, respectively. and These represent the reactive current-terminal voltage droop coefficient and the reactive current bias coefficient during ride-through, respectively. The threshold voltages for entering and exiting low-voltage ride-through are set. This refers to the active current before entering the low-voltage circuit.

[0018] In practical applications, It is generally set to 0. In this preferred embodiment, The value is 0.9pu.

[0019] In step 103, a Thevenin equivalent model of the induction motor is established, wherein the Thevenin equivalent model is used to calculate and determine the equivalent motor parameters based on the induction motor parameters, and to construct the relationship between the Thevenin equivalent voltage and the terminal voltage based on the induction motor parameters.

[0020] Preferably, a Thevenin equivalent model of the induction motor is established, and the expression of the Thevenin equivalent model is as follows: (6) (7) In the formula, , and These are the stator resistance, stator reactance, and magnetizing reactance in the parameters of an induction motor. This is the Thevenin equivalent voltage. and These are the equivalent resistance and equivalent reactance in the equivalent motor parameters, respectively, and j is the imaginary part of the complex number.

[0021] Figure 2 A schematic diagram illustrating the generation of a Thevenin equivalent model based on a T-type equivalent model of an induction motor according to a preferred embodiment of the present invention. Figure 2 As shown, the T-type equivalent model of the induction motor includes stator resistance Rs, rotor resistance Rr, stator reactance Xs, rotor reactance Xr, excitation reactance Xm, and terminal voltage Xm. The rotor-side current is Ir. After performing the Thevenin equivalent, the terminal Thevenin equivalent voltage is... The stator resistance Rs, stator reactance Xs, and magnetizing reactance Xm are equivalent to resistances. and reactance .

[0022] In step 104, an active power absorption model of the induction motor is established, wherein the active power absorption model is used to construct the relationship between the active power absorption of the induction motor and the Thevenin equivalent voltage, terminal voltage and slip rate based on the equivalent motor parameters and the induction motor parameters.

[0023] Preferably, a model for the absorbed active power of the induction motor is established, wherein the expression for the absorbed active power model is: (8) (9) In the formula, The active power absorbed by the induction motor is s, and the slip is s. and These are the rotor resistance and rotor reactance, which are parameters of an induction motor. This represents an intermediate variable set up to simplify the formula.

[0024] according to Figure 2 The T-type equivalent model shows that the electromagnetic power of the induction motor and stator copper loss The expressions are as follows: make The expression for absorbed active power in formula (8) can be obtained by converting the rotor-side current Ir into the expression in the Thevenin equivalent model.

[0025] In step 105, an electromagnetic torque model of the induction motor is established, wherein the electromagnetic torque model is used to construct the relationship between the electromagnetic torque of the induction motor and the Thevenin equivalent voltage and slip rate based on the equivalent motor parameters and the induction motor parameters.

[0026] Preferably, an electromagnetic torque model of the induction motor is established, wherein the expression of the electromagnetic torque model of the induction motor is: (10) (11) (12) (13) (14) In the formula, This refers to the electromagnetic torque of the induction motor.

[0027] In step 106, a slip rate model is established based on the mechanical torque. The slip rate model is used to construct the relationship between the unstable slip rate and the terminal voltage, and the stable slip rate and the terminal voltage, respectively, when the electromagnetic torque and the mechanical torque of the induction motor are equal.

[0028] Preferably, establishing a slip rate model based on the mechanical torque includes: Let the electromagnetic torque of the induction motor be equal to its mechanical torque; its expression is: (15) In the formula, This refers to the mechanical torque in the parameters of the induction motor. Combining equations (10) to (15), we obtain the following equation: (16) In the formula: Solving equation (16) yields the following expression for the slip ratio model: (17) (18) In the formula, and These are the instability slip rate and the steady-state slip rate, respectively. .

[0029] In this preferred embodiment, the electromagnetic torque model of the induction motor is a model about the slip rate and the Thevenin equivalent voltage. The Thevenin equivalent voltage is related to the terminal voltage of the induction motor. Therefore, the unstable slip rate and stable slip rate obtained by solving formula (16) are actually models that reflect their functional relationship with the terminal voltage.

[0030] In step 107, an active power model is established for the main grid feed-in, wherein the active power model for the main grid feed-in is used to construct the relationship between the active power fed in by the main grid and the absorbed active power and the active power output by distributed new energy sources.

[0031] Preferably, an active power model fed into the main grid is established, wherein the expression of the active power model fed into the main grid is: (19) In the formula, The active power fed into the main grid.

[0032] According to formula (8), the absorbed active power, under the condition that the parameters of the induction motor are determined, is a function of Thevenin equivalent voltage, slip rate and terminal voltage. According to formula (6), the Thevenin equivalent voltage can be expressed as a function related to the terminal voltage. According to formulas (10) to (19), both the unstable slip rate and the stable slip rate can be expressed as functions related to the Thevenin equivalent voltage and the terminal voltage. Therefore, the absorbed active power is actually a function of voltage that is only related to the terminal voltage. According to formula (1), the active power generated by distributed new energy sources is also a function that is only related to the terminal voltage when the active power control parameters are constant. Therefore, the active power fed into the main grid is essentially a function that is only related to the terminal voltage.

[0033] In step 108, a critical instability minimum voltage model is established. This model is used to solve for the hook-shaped curve generated from the instability slip rate curve and the stable slip rate curve, and to determine the critical instability minimum voltage based on the hook-shaped curve. It also determines the region where the operating point is located after fault clearance based on the boundary line between the hook-shaped curve and the critical instability minimum voltage. The instability slip rate curve and the stable slip rate curve are located on a coordinate plane with the active power fed by the main grid as the abscissa and the induction motor terminal voltage as the ordinate. The instability slip rate curve and the stable slip rate curve are obtained by substituting the instability slip rate and stable slip rate from the slip rate model into the active power model fed by the main grid, and allowing the terminal voltage to take arbitrary values ​​within a defined range, reflecting the input from the main grid. The curve representing the relationship between active power and terminal voltage, wherein the hook-shaped curve is formed by all coordinate points on the instability slip rate curve and the stable slip rate curve, the critical minimum instability voltage is the lowest terminal voltage corresponding to the hook-shaped curve, the critical minimum instability voltage boundary line is a straight line passing through the coordinate point corresponding to the critical minimum instability voltage and parallel to the horizontal axis, the region where the operating point is located after the fault is cleared includes a stable region, an unstable region, and a multistate region, the multistate region is the region enclosed by the hook-shaped curve, the stable region is the region located outside the right side of the instability slip rate curve and above the critical minimum instability voltage boundary line, and the region on the coordinate plane other than the hook-shaped curve, the multistate region, and the stable region is the unstable region.

[0034] In this preferred embodiment, according to formulas (17) and (18), the instability slip rate and the stability slip rate are functions related to the generator terminal voltage. When the calculated results of the instability slip rate and the stability slip rate are limited to the interval [0, 1], the corresponding range of generator terminal voltage values ​​can be obtained. This range is used as the defined range of generator terminal voltage values. Substituting formulas (17) and (18) into formula (19), the instability slip rate curve and the stability slip rate curve with the grid-feed power on the horizontal axis and the generator terminal voltage on the vertical axis can be obtained respectively. The lowest generator terminal voltage corresponding to the hook-shaped curve formed by all the coordinate points on the instability slip rate curve and the stability slip rate curve is the critical minimum instability voltage. Based on the hook-shaped curve and the critical minimum instability voltage boundary line, the area where the operating point is located after the fault is cleared can be further divided into a multi-state region, a stable region, and an unstable region, such as Figure 4 As shown, the region enclosed by the instability slip rate curve and the stable slip rate curve is the multistate region. The region outside the right side of the instability slip rate curve, where the terminal voltage at the operating point after fault clearance is not less than the critical minimum instability voltage, is the steady-state region. The remaining region is the instability region.

[0035] The basis for dividing the region where the operating point is located after fault clearance in this preferred embodiment is as follows, based on the hook-shaped curve and the critical instability minimum voltage boundary: When the operating point is on or above the critical instability minimum voltage boundary line after the fault is cleared, it means that there is a solution for equation (16). If the operating point falls outside the right side of the instability slip rate curve after the fault is cleared, it means that the slip rate of the induction motor is less than the instability slip rate, the electromagnetic torque is greater than the mechanical torque, the system can remain stable, and will return to the stable slip rate curve represented by the stable slip rate, which is the stable region. If it is located in the left side of the stable slip rate curve, it means that the slip rate of the induction motor is greater than the instability slip rate, the electromagnetic torque is less than the mechanical torque, the system will experience voltage instability, which is the unstable region. If it falls in the area enclosed by the hook-shaped curve, it cannot be directly judged due to the existence of copper loss.

[0036] When the operating point is below the critical instability minimum voltage boundary line after the fault is cleared, it means that there is no solution to equation (16) at this time, there is no point in the system that can operate stably, the electromagnetic torque will always be less than the mechanical torque, the system will inevitably become unstable, and it is also an unstable region.

[0037] In step 109, based on the defined low voltage ride-through control rules, low voltage ride-through control is performed according to the critical instability minimum voltage, the terminal voltage of the operating point after the fault is cleared, and the region in which it is located.

[0038] Preferably, based on the defined low-voltage ride-through control rules, low-voltage ride-through control is performed according to the critical minimum voltage of instability, the terminal voltage of the operating point after fault clearance, and the region in which it is located. The low-voltage ride-through control rules are as follows: When the generator terminal voltage at the operating point is less than the critical minimum voltage of instability after the fault is cleared, the active power control parameters and reactive power control parameters of the power output model of the distributed new energy are adjusted so that the generator terminal voltage at the operating point is not less than the critical minimum voltage of instability after the fault is cleared. When the terminal voltage of the operating point after the fault is cleared is not less than the critical minimum voltage of instability, if the operating point after the fault is cleared is in the stable region, there is no need to adjust the parameters of the low voltage ride-through control; otherwise, adjust the active power control parameters of the power output model of the distributed renewable energy source until the operating point after the fault is cleared is in the stable region.

[0039] Figure 3 This is a schematic diagram of low-voltage ride-through control according to a preferred embodiment of the present invention, where the operating point terminal voltage is below the critical instability minimum voltage after fault clearance. Figure 3 As shown, after the fault is cleared, the generator terminal voltage at its operating point is less than the critical instability minimum voltage of 0.7598. At this time, the active power control parameters... Reactive power control parameters , According to the defined low-voltage ride-through control rules, it is necessary to adjust both active power control parameters and reactive power control parameters simultaneously. Ultimately, when... , , When the fault is cleared, the terminal voltage at the operating point is greater than the critical instability minimum voltage of 0.7598. When it is in the stable region, the system will be stable and there is no need to perform active control parameters for the low voltage ride-through control.

[0040] Figure 4 This is a schematic diagram of low-voltage ride-through control according to a preferred embodiment of the present invention, where the operating point terminal voltage is above the critical instability minimum voltage after fault clearance. Figure 4 As shown in the left figure, after the fault is cleared, the generator terminal voltage at the operating point is greater than the critical minimum voltage for instability, but it is not in the stable region, but rather in the multi-state region. According to the defined low-voltage ride-through control rule, at this time, it is necessary to adjust the active power control parameters of the distributed renewable energy source. Therefore, the active power control parameters in the left figure are adjusted accordingly. , Adjusted to the image on the right. , After the fault is cleared, the operating point is located above the critical instability voltage boundary line and to the right of the instability slip rate curve, i.e., the stable region. Therefore, its transient trajectory eventually converges to the stable slip rate curve, and the system becomes stable.

[0041] The distributed renewable energy low-voltage ride-through control method described in this preferred embodiment can, under the premise of considering the transient voltage support capability and equipment safety, adopt different low-voltage ride-through control methods according to different conditions to find the optimal transient voltage support, thereby further improving the stability of the power system connected to distributed renewable energy.

[0042] Exemplary System Figure 5 This is a schematic diagram of a distributed renewable energy low-voltage ride-through control system according to a preferred embodiment of the present invention. Figure 5 As shown, the distributed renewable energy low-voltage ride-through control system 200 of this preferred embodiment includes: The data acquisition module 201 is used to acquire the parameters of the induction motor and the parameters of the distributed new energy in the power system connected to the distributed new energy, wherein the parameters of the induction motor include mechanical torque; The first model module 202 is used to establish a distributed renewable energy power output model, wherein the distributed renewable energy power output model is used to construct the relationship between the active power output of the distributed renewable energy and the terminal voltage, and the relationship between the reactive power output and the terminal voltage, respectively, based on the distributed renewable energy parameters. The second model module 203 is used to establish the Thevenin equivalent model of the induction motor, wherein the Thevenin equivalent model is used to calculate and determine the equivalent motor parameters based on the induction motor parameters, and to construct the relationship between the Thevenin equivalent voltage and the terminal voltage based on the induction motor parameters. The third model module 204 is used to establish an active power absorption model of the induction motor, wherein the active power absorption model is used to construct the relationship between the active power absorption of the induction motor and the Thevenin equivalent voltage, terminal voltage and slip rate based on the equivalent motor parameters and the induction motor parameters. The fourth model module 205 is used to establish an electromagnetic torque model of the induction motor, wherein the electromagnetic torque model is used to construct the relationship between the electromagnetic torque of the induction motor and the Thevenin equivalent voltage and slip rate based on the equivalent motor parameters and the induction motor parameters. The fifth model module 206 is used to establish a slip rate model based on the mechanical torque, wherein the slip rate model is used to construct the relationship between the unstable slip rate and the terminal voltage, and the stable slip rate and the terminal voltage, respectively, when the electromagnetic torque of the induction motor and the mechanical torque are equal. The sixth model module 207 is used to establish an active power model fed into the main grid, wherein the active power model fed into the main grid is used to construct the relationship between the active power fed into the main grid and the absorbed active power and the active power output by distributed new energy sources. The seventh model module 208 is used to establish a critical instability minimum voltage model. This model is used to solve for a hook-shaped curve generated from the instability slip rate curve and the stable slip rate curve, and to determine the critical instability minimum voltage based on the hook-shaped curve. It also determines the region where the operating point is located after fault clearance based on the boundary line between the hook-shaped curve and the critical instability minimum voltage. The instability slip rate curve and the stable slip rate curve are located on a coordinate plane with the active power fed by the main grid as the abscissa and the induction motor terminal voltage as the ordinate. The instability slip rate curve and the stable slip rate curve are obtained by substituting the instability slip rate and stable slip rate from the slip rate model into the active power model fed by the main grid, and allowing the terminal voltage to take arbitrary values ​​within a defined range, reflecting the main grid voltage. The curve showing the relationship between the input active power and the terminal voltage, wherein the hook-shaped curve is formed by all coordinate points on the instability slip curve and the stable slip curve, the critical minimum instability voltage is the lowest terminal voltage corresponding to the hook-shaped curve, the critical minimum instability voltage boundary line is a straight line passing through the coordinate point corresponding to the critical minimum instability voltage and parallel to the horizontal axis, the region where the operating point is located after the fault is cleared includes a stable region, an unstable region and a multistate region, the multistate region is the region enclosed by the hook-shaped curve, the stable region is the region located outside the right side of the instability slip curve and located on and above the critical minimum instability voltage boundary line, and the region on the coordinate plane other than the hook-shaped curve, the multistate region and the stable region is the unstable region; The ride-through control module 209 is used to perform low-voltage ride-through control based on the defined low-voltage ride-through control rules, the critical instability minimum voltage, the terminal voltage of the operating point after the fault is cleared, and the area in which it is located.

[0043] The distributed new energy low-voltage ride-through control system and the distributed new energy low-voltage ride-through control method described in this preferred embodiment have the same steps and achieve the same technical effects, taking into account the transient voltage support capability and equipment safety, and will not be repeated here.

[0044] Exemplary electronic devices Figure 6 This is a schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention. Figure 6 As shown, the electronic device includes one or more processors 301 and memory 302.

[0045] The processor 301 may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0046] The memory 302 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 301 may execute the program instructions to implement the distributed renewable energy low-voltage ride-through control method of the various embodiments disclosed above and / or other desired functions. In one example, the electronic device may also include an input device 303 and an output device 304, these components being interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0047] In addition, the input device 303 may also include, for example, a keyboard, a mouse, etc.

[0048] The output device 304 can output various information to the outside. The output device 304 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0049] Of course, for the sake of simplicity, Figure 6 Only some of the components of the electronic device relevant to this disclosure are shown, omitting components such as buses, input / output interfaces, etc. In addition, the electronic device may include any other suitable components depending on the specific application.

[0050] Exemplary computer program products and computer-readable storage media In addition to the methods and devices described above, embodiments of the present invention may also be computer program products, which include computer program instructions that, when executed by a processor, cause the processor to perform the steps in the distributed renewable energy low-voltage ride-through control method according to various embodiments of the present invention as described in the "Exemplary Methods" section of this specification.

[0051] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of the present invention. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0052] Furthermore, embodiments of the present invention may also be computer-readable storage media storing computer program instructions thereon, which, when executed by a processor, cause the processor to perform the steps in the distributed renewable energy low-voltage ride-through control method according to various embodiments of the present invention described in the "Exemplary Methods" section above.

[0053] The computer-readable storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof.

[0054] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0055] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For system embodiments, since they largely correspond to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0056] The block diagrams of devices, apparatuses, devices, and systems involved in this invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0057] The apparatus and methods of the present invention may be implemented in many ways. For example, they may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order of steps for the methods is for illustrative purposes only, and the steps of the methods of the present invention are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, the present invention may also be implemented as a program recorded on a recording medium, the program comprising machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers recording media storing programs for performing the methods according to the present invention.

[0058] It should also be noted that in the apparatus, device, and method of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered equivalents of the present invention. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Therefore, the invention is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0059] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A distributed renewable energy low-voltage ride-through control method, characterized in that, The method includes: Acquire the parameters of the induction motor and the parameters of the distributed renewable energy in the power system connected to the distributed renewable energy source, wherein the parameters of the induction motor include mechanical torque; A distributed renewable energy power output model is established, wherein the distributed renewable energy power output model is used to construct the relationship between the active power output of the distributed renewable energy and the terminal voltage, and the relationship between the reactive power output and the terminal voltage, respectively, based on the distributed renewable energy parameters. A Thevenin equivalent model of an induction motor is established, wherein the Thevenin equivalent model is used to calculate and determine the equivalent motor parameters based on the induction motor parameters, and to construct the relationship between the Thevenin equivalent voltage and the terminal voltage based on the induction motor parameters; An active power absorption model for an induction motor is established, wherein the active power absorption model is used to construct the relationship between the active power absorption of the induction motor and the Thevenin equivalent voltage, terminal voltage, and slip rate based on the equivalent motor parameters and the induction motor parameters. An electromagnetic torque model for an induction motor is established, wherein the electromagnetic torque model is used to construct the relationship between the electromagnetic torque of the induction motor and the Thevenin equivalent voltage and slip rate based on the equivalent motor parameters and the induction motor parameters. A slip rate model is established based on the mechanical torque, wherein the slip rate model is used to construct the relationship between the unstable slip rate and the terminal voltage, and the stable slip rate and the terminal voltage, respectively, when the electromagnetic torque and the mechanical torque of the induction motor are equal. Establish an active power model fed into the main grid, wherein the active power model fed into the main grid is used to construct the relationship between the active power fed into the main grid and the absorbed active power and the active power output by distributed new energy sources. A critical instability minimum voltage model is established, wherein the critical instability minimum voltage model is used to solve the hook-shaped curve generated from the instability slip rate curve and the stability slip rate curve, and to determine the critical instability minimum voltage based on the hook-shaped curve. The model also determines the region of the operating point after fault clearance based on the boundary line between the hook-shaped curve and the critical instability minimum voltage. The instability slip rate curve and the stability slip rate curve are located on a coordinate plane with the active power fed by the main grid as the abscissa and the induction motor terminal voltage as the ordinate. The instability slip rate curve and the stability slip rate curve are obtained by substituting the instability slip rate and the stability slip rate from the slip rate model into the active power model fed by the main grid, and allowing the terminal voltage to take arbitrary values ​​within a defined range, thus reflecting the active power fed by the main grid. The curve representing the relationship between the slip rate and the terminal voltage, wherein the hook-shaped curve is formed by all coordinate points on the instability slip rate curve and the stable slip rate curve, the critical minimum instability voltage is the lowest terminal voltage corresponding to the hook-shaped curve, the critical minimum instability voltage boundary line is a straight line passing through the coordinate point corresponding to the critical minimum instability voltage and parallel to the horizontal axis, the region where the operating point is located after the fault is cleared includes a stable region, an unstable region, and a multistate region, the multistate region is the region enclosed by the hook-shaped curve, the stable region is the region located outside the right side of the instability slip rate curve and above the critical minimum instability voltage boundary line, and the region on the coordinate plane other than the hook-shaped curve, the multistate region, and the stable region is the unstable region; Based on the defined low-voltage ride-through control rules, low-voltage ride-through control is performed according to the critical minimum voltage of instability, the terminal voltage of the operating point after the fault is cleared, and the region in which it is located.

2. The method according to claim 1, characterized in that, A distributed renewable energy power output model is established, wherein the expression of the distributed renewable energy power output model is: (1) (2) (3) In the formula, Active power generated by distributed renewable energy sources; Reactive power generated by distributed renewable energy sources; Operating mode; The terminal voltage during runtime t. Used according to Determine the first Active power under various operating modes Used according to Determine the first Reactive power under various operating modes; when At that time, the power output of distributed energy sources were as follows: （4） （5） In the formula, , and The active power control parameters for low voltage ride-through control in the distributed renewable energy parameters are respectively represented as active power-terminal voltage droop coefficient, active current bias coefficient before distributed renewable energy ride-through, and active current bias coefficient during ride-through. and The reactive power control parameters for low voltage ride-through control in the distributed renewable energy parameters are represented by the reactive current-terminal voltage droop coefficient and the reactive current bias coefficient during ride-through, respectively. The threshold voltages for entering and exiting low-voltage ride-through are set. This refers to the active current before entering the low-voltage circuit.

3. The method according to claim 1, characterized in that, A Thevenin equivalent model of the induction motor is established, and the expression of the Thevenin equivalent model is as follows: (6) (7) In the formula, , and These are the stator resistance, stator reactance, and magnetizing reactance in the parameters of an induction motor. This is the Thevenin equivalent voltage. and These are the equivalent resistance and equivalent reactance in the equivalent motor parameters, respectively, and j is the imaginary part of the complex number.

4. The method according to claim 3, characterized in that, A model for the active power absorbed by an induction motor is established, wherein the expression for the active power absorbed model is: (8) (9) In the formula, The active power absorbed by the induction motor is s, and the slip is s. and These are the rotor resistance and rotor reactance, which are parameters of an induction motor. This represents an intermediate variable set up to simplify the formula.

5. The method according to claim 4, characterized in that, An electromagnetic torque model for an induction motor is established, wherein the expression for the electromagnetic torque model of the induction motor is: (10) (11) (12) (13) (14) In the formula, This refers to the electromagnetic torque of the induction motor.

6. The method according to claim 5, characterized in that, A slip rate model is established based on the aforementioned mechanical torque, including: Let the electromagnetic torque of the induction motor be equal to its mechanical torque; its expression is: (15) In the formula, This refers to the mechanical torque in the parameters of the induction motor. Combining equations (10) to (15), we obtain the following equation: (16) In the formula: Solving equation (16) yields the following expression for the slip ratio model: (17) (18) In the formula, and These are the instability slip rate and the steady-state slip rate, respectively. .

7. The method according to claim 2, characterized in that, Establish an active power model fed into the main grid, wherein the expression for the active power model fed into the main grid is: (19) In the formula, The active power fed into the main grid.

8. The method according to claim 2, characterized in that, Based on the defined low-voltage ride-through control rules, low-voltage ride-through control is performed according to the critical minimum voltage of instability, the terminal voltage of the operating point after fault clearance, and the region it is located in. The low-voltage ride-through control rules are as follows: When the generator terminal voltage at the operating point is less than the critical minimum voltage of instability after the fault is cleared, the active power control parameters and reactive power control parameters of the power output model of the distributed new energy are adjusted so that the generator terminal voltage at the operating point is not less than the critical minimum voltage of instability after the fault is cleared. When the terminal voltage of the operating point after the fault is cleared is not less than the critical minimum voltage of instability, if the area where the operating point is located after the fault is cleared is a stable area, there is no need to adjust the parameters of the low voltage ride-through control. Otherwise, adjust the active power control parameters of the power output model of the distributed new energy source until the area where the operating point is located after the fault is cleared is a stable area.

9. A distributed renewable energy low-voltage ride-through control system, characterized in that, The system includes: The data acquisition module is used to acquire the parameters of the induction motor and the parameters of the distributed new energy in the power system connected to the distributed new energy, wherein the parameters of the induction motor include mechanical torque; The first model module is used to establish a distributed renewable energy power output model, wherein the distributed renewable energy power output model is used to construct the relationship between the active power output of the distributed renewable energy and the terminal voltage, and the relationship between the reactive power output and the terminal voltage, respectively, based on the distributed renewable energy parameters. The second model module is used to establish the Thevenin equivalent model of the induction motor, wherein the Thevenin equivalent model is used to calculate and determine the equivalent motor parameters based on the induction motor parameters, and to construct the relationship between the Thevenin equivalent voltage and the terminal voltage based on the induction motor parameters. The third model module is used to establish the active power absorption model of the induction motor. The active power absorption model is used to construct the relationship between the active power absorption of the induction motor and the Thevenin equivalent voltage, terminal voltage and slip rate based on the equivalent motor parameters and the induction motor parameters. The fourth model module is used to establish an electromagnetic torque model of the induction motor, wherein the electromagnetic torque model is used to construct the relationship between the electromagnetic torque of the induction motor and the Thevenin equivalent voltage and slip rate based on the equivalent motor parameters and the induction motor parameters. The fifth model module is used to establish a slip rate model based on the mechanical torque. The slip rate model is used to construct the relationship between the unstable slip rate and the terminal voltage, and the stable slip rate and the terminal voltage, respectively, when the electromagnetic torque and the mechanical torque of the induction motor are equal. The sixth model module is used to establish an active power model fed into the main grid, wherein the active power model fed into the main grid is used to construct the relationship between the active power fed into the main grid and the absorbed active power and the active power output by distributed new energy sources. The seventh model module is used to establish a critical minimum voltage instability model. This model is used to solve for a hook-shaped curve generated from the instability slip rate curve and the stable slip rate curve, and to determine the critical minimum voltage instability based on the hook-shaped curve. It also determines the region where the operating point is located after fault clearance based on the boundary line between the hook-shaped curve and the critical minimum voltage instability. The instability slip rate curve and the stable slip rate curve are located on a coordinate plane with the active power fed by the main grid as the abscissa and the induction motor terminal voltage as the ordinate. The instability slip rate curve and the stable slip rate curve are obtained by substituting the instability slip rate and stable slip rate from the slip rate model into the active power model fed by the main grid, and ensuring that the terminal voltage is within a defined range. The curve obtained by taking arbitrary values ​​within the value range reflects the relationship between the active power fed into the main grid and the generator terminal voltage. The critical instability minimum voltage is the minimum generator terminal voltage corresponding to the hook-shaped curve. The critical instability minimum voltage boundary line is a straight line passing through the coordinate point corresponding to the critical instability minimum voltage and parallel to the horizontal axis. The region where the operating point is located after the fault is cleared includes a stable region, an unstable region, and a multistate region. The multistate region is the region enclosed by the hook-shaped curve. The stable region is the region located outside the right side of the instability slip rate curve and located on and above the critical instability minimum voltage boundary line. The region on the coordinate plane other than the hook-shaped curve, the multistate region, and the stable region is the unstable region. The ride-through control module is used to perform low-voltage ride-through control based on the defined low-voltage ride-through control rules, the critical instability minimum voltage, the terminal voltage of the operating point after the fault is cleared, and the area in which it is located.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method as described in any one of claims 1-8.

11. An electronic device, characterized in that, include: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the executable instructions to implement the steps of the method according to any one of claims 1-8.

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