Open-winding motor interface and grid-connected system low-voltage ride-through control method and device

Abstract

The application discloses a kind of open-winding motor interface grid-connected system low voltage ride through control method and device, comprising: first, obtain grid dispatch power given value, calculate system apparent power given value and power factor angle given value;Second, according to system apparent power and power factor angle given value, design apparent power to motor excitation voltage droop, power factor angle to converter voltage phase and amplitude droop three droop structure system power control method;Third, according to the short-circuit current safety constraint of converter and the reactive power support demand of grid, design low voltage ride through method to inhibit transient overcurrent by compensating converter amplitude droop and phase droop channel at the moment of grid fault;Finally, the voltage vector required by inverter is calculated, and the driving signal of each bridge arm switching device in the inverter is generated combined with SVPWM, to exert control on system, realize low voltage ride through.

Description

Technical Field

[0001] This application relates to the field of motor control technology, and in particular to a low voltage ride-through control method and device for an open-winding motor interface grid-connected system. Background Technology

[0002] With the increasing proportion of new energy equipment in the power system, the penetration rate of new energy sources, represented by wind and solar power, has been rising year by year in recent years. Their large-scale integration has brought severe challenges to the safe and stable operation of the power grid. Grid connection rules require new energy units to have low-voltage ride-through capability, that is, to maintain uninterrupted operation of new energy units during grid faults to ensure the safe and stable operation of the power system. However, due to the limited overload capacity of power electronic devices, the instantaneous overcurrent during a short-circuit fault in the grid can easily damage the devices, posing a significant threat to the safety and stability of the system. Currently, grid-connected converters have gained widespread attention due to their active disturbance rejection and active support characteristics. They possess voltage and frequency support capabilities, solving the problem of traditional grid-connected control relying on phase-locked loops being prone to disconnection and instability in weak grids due to a lack of support capabilities. However, when the grid is subjected to large disturbances, the power angle curve controlled by the outer power loop and the fixed active and reactive power reference values ​​limit the potential for significant power angle instability and the generation of high-multiple short-circuit currents, leading to the breakdown of power electronic devices and subsequent equipment damage.

[0003] Some scholars have also studied ways to enhance the transient support capability of renewable energy converters by improving grid-connected topologies. Adding devices to the grid-connected system for reactive power support offers greater flexibility. Commonly used reactive power compensation devices include parallel capacitors / reactors, static var compensators (SVCs), static synchronous compensators (STATCOMs), and synchronous condensers. Traditional capacitors / reactors, due to their fixed reactance, may interact with grid impedance, potentially causing resonance risks. SVCs experience significant voltage support degradation under weak grid conditions; furthermore, large-capacity SVCs require multiple parallel reactors / capacitors, leading to a substantial increase in floor space requirements and potentially causing cascading stability issues. For STATCOMs, high switching frequencies increase power losses, necessitate additional cooling systems, and incur high maintenance costs. Additionally, their impedance characteristics in the sub- / super-synchronous frequency bands can negatively impact wind turbine performance. Adding synchronous power supplies can enhance grid strength and synchronization characteristics, but the engineering solution of installing synchronous condensers is costly and cannot be configured at lower voltage levels, limiting its support capability for renewable energy generators.

[0004] To fundamentally solve this problem, improvements have been made to the system topology, resulting in grid-connected systems with open-winding motor interfaces. This topology provides new energy devices with active support capabilities and improves overload capacity. To promote the adoption of this topology, corresponding low-voltage ride-through control strategies need to be designed for this topology. Summary of the Invention

[0005] The purpose of this application is to provide a low-voltage ride-through control method and device for an open-winding motor interface grid-connected system, so as to solve the technical problem that the overload capacity of new energy converter power generation devices is limited when a short-circuit fault occurs in the power grid.

[0006] According to a first aspect of the embodiments of this application, a low-voltage ride-through control method for an open-winding motor interface grid-connected system is provided, characterized in that it includes:

[0007] Obtain the active and reactive power setpoints provided by the power grid dispatching system;

[0008] Based on the given active power and reactive power values, calculate the system apparent power setpoint and power factor angle setpoint;

[0009] Based on the system apparent power setpoint, power factor angle setpoint, and reactive power setpoint, a three-droop structure system power control method is designed, where apparent power droops with respect to motor excitation voltage, and power factor angle droops with respect to converter voltage phase and amplitude. This method takes the motor excitation voltage and the converter d-axis and q-axis reference voltage vectors as direct control targets, and actively constructs the system voltage vector triangle corresponding to the power setpoint to achieve the expected active and reactive power setpoints.

[0010] Based on the safety constraints of the converter short-circuit current and the reactive power support requirements of the power grid, a low-voltage ride-through control method for new energy converters is designed. This method compensates for the amplitude droop and phase droop of the converter during the instant of a power grid fault. By reducing the reactance voltage drop on the motor, it indirectly suppresses the current flowing through the motor stator, thereby achieving low-voltage ride-through.

[0011] The power control method and low voltage ride-through control method of the three-droop structure system are used to generate the d-axis and q-axis reference voltage vectors and the reference electrical angle of the converter.

[0012] Based on the d-axis and q-axis reference voltage vectors and the reference electrical angle of the inverter, the voltage vector required by the inverter is calculated, and the drive signals of each bridge arm switching device in the inverter are generated in combination with SVPWM to apply control to the system.

[0013] According to a second aspect of the embodiments of this application, a low-voltage ride-through control device for an open-winding motor interface grid-connected system is provided, characterized in that it comprises:

[0014] The data acquisition module is used to acquire the active and reactive power setpoints given by the power grid dispatching system.

[0015] The first calculation module is used to calculate the system apparent power setpoint and power factor angle setpoint based on the active power and reactive power setpoints.

[0016] The first design module is used to design a three-droop structure system power control method based on the system apparent power setpoint, power factor angle setpoint, and reactive power setpoint. This method has the apparent power drooping with respect to the motor excitation voltage, the power factor angle drooping with respect to the converter voltage phase and amplitude, and takes the motor excitation voltage and the converter d-axis and q-axis reference voltage vectors as direct control targets. By actively constructing the system voltage vector triangle corresponding to the power setpoint, the expected active power and reactive power setpoints are achieved.

[0017] The second design module is used to design a low-voltage ride-through control method for new energy converters based on the safety constraints of the converter short-circuit current and the reactive power support requirements of the power grid. This method compensates for the amplitude droop and phase droop of the converter at the moment of power grid fault, and indirectly suppresses the current flowing through the stator of the motor by reducing the reactance voltage drop on the motor, thereby achieving low-voltage ride-through.

[0018] The generation module is used to generate the converter's d-axis and q-axis reference voltage vectors and the converter's reference electrical angles through the power control method and low-voltage ride-through control method of the three-droop structure system.

[0019] The control module is used to calculate the voltage vector required by the inverter based on the d-axis and q-axis reference voltage vectors of the inverter and the reference electrical angle of the inverter, and to generate drive signals for each bridge arm switching device in the inverter in combination with SVPWM, so as to apply control to the system.

[0020] According to a third aspect of the embodiments of this application, an electronic device is provided, comprising:

[0021] One or more processors;

[0022] Memory, used to store one or more programs;

[0023] When the one or more programs are executed by the one or more processors, the one or more processors perform the method as described in the first aspect.

[0024] The technical solutions provided by the embodiments of this application may include the following beneficial effects:

[0025] As can be seen from the above embodiments, this application adopts the technical means of connecting an open-winding synchronous motor and a new energy converter in series to the power grid, overcoming the technical problem of insufficient overload capacity of traditional new energy converter power generation devices under short-circuit faults in the power grid, thereby achieving low-voltage ride-through. By designing a system power control method with a three-droop structure of synchronous motor excitation voltage, converter voltage phase, and transformer voltage amplitude, the technical problem of the lack of a matching converter transient power control strategy for the aforementioned open-winding synchronous motor interface new energy power generation device is overcome, thereby allowing flexible adjustment of the power of the converter and open-winding motor when a short-circuit fault occurs in the power grid. By designing a transient overcurrent suppression method with instantaneous compensation of new energy converter voltage phase-amplitude, the technical problem of new energy converter power generation devices being easily damaged by high-multiple short-circuit currents when a short-circuit fault occurs in the power grid is overcome, thereby achieving low-voltage ride-through.

[0026] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0028] Figure 1 This is the topology of an open-winding motor interface grid-connected system according to an embodiment of the present invention.

[0029] Figure 2 This is a flowchart of a low-voltage ride-through control method for an open-winding motor interface grid-connected system according to an embodiment of the present invention.

[0030] Figure 3 This is a control block diagram of a power control method for a three-droop structure system according to an embodiment of the present invention.

[0031] Figure 4 This is a control block diagram of a low-voltage ride-through control method for a new energy converter according to an embodiment of the present invention.

[0032] Figure 5 The figure shows the results of a simulation case without converter voltage phase-amplitude compensation according to an embodiment of the present invention.

[0033] Figure 6 The figure shows the simulation results of adding a converter voltage phase-amplitude compensation stage according to an embodiment of the present invention.

[0034] Figure 7 This is a block diagram of a low-voltage ride-through control device for an open-winding motor interface grid-connected system according to an embodiment of the present invention. Detailed Implementation

[0035] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0036] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0037] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0038] Figure 1 The topology of the open-winding motor interface grid-connected system studied in this embodiment of the invention includes a new energy power generation device and a DC / AC three-phase inverter I, an open-winding synchronous motor II, and an AC power grid III. The new energy power generation device and the DC / AC three-phase inverter are connected to photovoltaic or energy storage on the DC side to realize the DC-AC conversion of new energy. Three terminals of the stator winding of the open-winding synchronous motor are connected to the converter, and the other three terminals are connected to the power grid. The motor operates in motor state without load. The power grid can be regarded as a three-phase ideal voltage source.

[0039] Compared with the traditional grid-connected topology of new energy systems, Figure 1 The open-winding synchronous motor winding impedance introduced into the topology can serve as a filter at the converter output port, thereby reducing system costs to some extent. Simultaneously, under transient conditions, it enables the new energy converter to possess inertia response capabilities similar to synchronous machines, thus improving the problem of insufficient grid inertia. Furthermore, in the event of a short-circuit fault in the grid, it can withstand short-circuit currents that are several times higher than the converter's overload capacity. However, the introduction of the open-winding motor will also slightly increase the system's topology complexity and operating losses.

[0040] Figure 2This is a flowchart illustrating a low-voltage ride-through control method for an open-winding motor interface grid-connected system according to an embodiment of the present invention; as follows: Figure 2 As shown, the method includes the following steps:

[0041] S1: Obtain the active and reactive power setpoints provided by the power grid dispatching system;

[0042] Specifically, the system receives active power setpoints from the dispatch center via automatic generation control in real time, and reactive power setpoints from the dispatch center via automatic voltage control system synchronously. This step provides the basic data source for subsequent method design.

[0043] S2: Calculate the system apparent power setpoint and power factor angle setpoint based on the given active power and reactive power values;

[0044] Specifically, the system apparent power setpoint and power factor angle setpoint are calculated using the following formulas respectively;

[0045] ;

[0046] In the formula: S ref The apparent power setpoint of the system; P ref The active power setpoint for power grid dispatch; Q ref The reactive power setpoint for power grid dispatching; φ ref This is the given value for the power factor angle.

[0047] This step lays the foundation for the subsequent transfer of active and reactive power control to apparent power and power factor angle control.

[0048] S3: Based on the system's apparent power setpoint, power factor angle setpoint, and reactive power setpoint, a three-droop structure system power control method is designed, where apparent power droops with respect to the motor excitation voltage, and the power factor angle droops with respect to the converter voltage phase and amplitude. This method uses the motor excitation voltage and the converter's d-axis and q-axis reference voltage vectors as direct control targets. By actively constructing a system voltage vector triangle corresponding to the power setpoint, the expected active and reactive power setpoints are achieved. The power control method block diagram is shown below. Figure 3 As shown, it includes the following sub-steps:

[0049] S31: Setpoint for the apparent power of the system S Sagging, sagging coefficient is k 1. Obtain the excitation voltage u f ;

[0050] Specifically, by analyzing the voltage vector relationship and active and reactive power among the converter, motor and power grid, it can be found that the apparent power of the system and the motor voltage amplitude conform to the droop control law. Since the motor voltage is determined by the excitation voltage, droop control is adopted to indirectly achieve accurate control of the motor excitation voltage through the apparent power of the control system.

[0051] Based on the droop relationship between the system's apparent power and the motor's excitation voltage, the excitation voltage is constructed. u f Input, excitation voltage u f The calculation formula for the input is as follows:

[0052] ;

[0053] ;

[0054] In the formula, S X represents the system's apparent power. md For motor d Shaft-induced reactance; X s For the stator reactance of the motor; X f For the motor excitation reactance; U g This is the grid voltage.

[0055] S32: Power factor angle setpoint φ Sagging, sagging coefficient is k 2. Furthermore, a phase synchronization and accurate tracking circuit is added to the forward path of the converter phase differential to obtain the converter phase. θ 1;

[0056] Specifically, by analyzing the voltage vector relationship and active and reactive power among the converter, motor and power grid, the droop control rate of the system power factor angle and the converter voltage phase can be obtained. Therefore, droop control is adopted to indirectly achieve accurate control of the converter voltage phase by controlling the system power factor angle.

[0057] Based on voltage phase jumps caused by grid fluctuations, an additional converter voltage phase synchronization mechanism is added to ensure that the system voltage vector phase relationship changes synchronously, including:

[0058] The additional amount required for converter voltage phase synchronization is calculated using the following formula:

[0059] ;

[0060] In the formula, θ com Additional quantity for the voltage phase synchronization stage of the converter; Δ θ0 represents the initial phase difference between the converter voltage phase and the grid voltage phase; Δ θ The instantaneous phase difference between the converter voltage phase and the grid voltage phase during a fault.

[0061] Based on the relationship between the grid power factor angle and the droop of the converter voltage phase, as well as the phase synchronization and accurate tracking links, the input value of the converter voltage phase is constructed. The formulas for calculating the input values ​​of the converter voltage phase and amplitude are as follows:

[0062] ;

[0063] In the formula, θ 1 represents the phase difference between the converter voltage and the grid voltage;

[0064] PI control is performed based on the difference between the system reactive power setpoint and the system reactive power (e.g., Figure 3 Module 9), added to the forward path of the converter phase differential, ensures the accuracy and speed of system operating power, including:

[0065] The additional amount required for accurate voltage tracking of the converter is calculated using the following formula:

[0066] ;

[0067] In the formula, θ q Additional parameters for accurate voltage phase tracking of the converter; k pq and k iq These are the proportional and integral coefficients of the PI regulator, which are additional factors for accurate phase tracking of the converter. Q ref The given value for system reactive power; Q This represents the actual value of the system's reactive power.

[0068] S33: Power factor angle setpoint φ Sagging, Sagging Factor k 3. A phase synchronization element is added to the forward path where the converter voltage amplitude is drooping to obtain the converter voltage amplitude. U vsc ;

[0069] Specifically, by analyzing the voltage vector relationship and active and reactive power among the converter, motor and power grid, it can be found that the system power factor angle and the converter voltage amplitude conform to the droop control law. Therefore, droop control is adopted to indirectly achieve accurate control of the converter voltage amplitude by controlling the power factor angle of the power grid.

[0070] Based on voltage phase jumps caused by grid fluctuations, an additional converter voltage phase synchronization mechanism is added, including:

[0071] The additional amount required for converter voltage phase synchronization is calculated using the following formula:

[0072] ;

[0073] In the formula, θ com Additional quantity for the voltage phase synchronization stage of the converter; Δ θ 0 represents the initial phase difference between the converter voltage phase and the grid voltage phase; Δ θ The instantaneous phase difference between the converter voltage phase and the grid voltage phase during a fault.

[0074] Based on the droop relationship between the system power factor angle and the converter voltage phase and amplitude, the input value of the converter voltage amplitude is determined. The formula for calculating the input value of the converter voltage amplitude is as follows:

[0075] ;

[0076] In the formula, U vsc This refers to the voltage amplitude of the converter.

[0077] S34: Through excitation voltage u f Indirect control of open-winding synchronous motor voltage U s Converter voltage phase θ 1 and converter voltage amplitude U vsc Direct control actively constructs the system voltage vector triangle, thereby achieving system power control;

[0078] Specifically, based on the vector relationship between the converter voltage, synchronous motor voltage, and grid voltage, a system voltage vector triangle is actively constructed to achieve system power control, including:

[0079] The formula for calculating the steady-state voltage of the system is as follows:

[0080] ;

[0081] In the formula: U vsc For converter voltage, U s The voltage of the open-winding synchronous motor. U g This is the grid voltage. E 0 represents the induced internal electromotive force of an open-winding synchronous motor. j The imaginary unit, I X is the current flowing through the grid connection point. s L is the stator reactance of the motor, ω is the rotor speed of the motor, and L is the stator reactance of the motor.md The d-axis inductance of the motor. I f This refers to the excitation current of an open-winding synchronous motor.

[0082] The formula for calculating the steady-state current of the system is as follows:

[0083] ;

[0084] The formula for calculating the steady-state power of the system is as follows:

[0085] ;

[0086] In the formula: P , Q These are the system's active power and reactive power, respectively.

[0087] By using the three-droop structure system power control method, the converter and motor can be controlled as a whole in a coordinated manner, and the device can be controlled quickly and accurately to respond to system power commands.

[0088] S4: Based on the safety constraints of the converter short-circuit current and the reactive power support requirements of the power grid, a low-voltage ride-through control method for new energy converters is designed. This method compensates for the amplitude droop and phase droop of the converter during a grid fault, and indirectly suppresses the current flowing through the motor stator by reducing the reactance voltage drop on the motor, thereby achieving low-voltage ride-through. The method includes the following sub-steps:

[0089] S41: Collect motor stator current and grid voltage, and calculate the reactive power at the grid connection point;

[0090] Specifically, a three-phase current sensor is used to collect the stator current of the motor. I Voltage sensors collect grid voltage. U g The reactive power at the grid connection point can be calculated as follows:

[0091] ;

[0092] In the formula, Q out1 The reactive power at the grid connection point before the fault. U g1 The three-phase voltage of the power grid before the fault. I 1 represents the three-phase stator current of the motor before the fault. φ 1 represents the power factor angle at the grid connection point before the fault;

[0093] The formula for calculating reactive power after a short-circuit fault in the power grid is as follows:

[0094] ;

[0095] In the formula, Q out2 This refers to the reactive power at the grid connection point after a fault. U g2 The three-phase voltage of the power grid after the fault. I 2 represents the three-phase stator current and current rating of the motor after the fault. φ 2 represents the power factor angle at the grid connection point after the fault.

[0096] S42: Based on the reactive power at the grid connection point and the rated current constraint of the converter, calculate the phase difference between the system converter voltage and the grid voltage after fault instantaneous compensation;

[0097] Specifically, to simultaneously satisfy the converter short-circuit current capacity constraint and the device reactive power support, the power factor angle at the grid connection point after the fault must be... φ The formula for calculating 2 is as follows:

[0098] ;

[0099] In the formula, I gmax This is to ensure that the converter can withstand the maximum short-circuit current capacity.

[0100] S43: Based on the phase difference between the converter voltage and the grid voltage during the fault instantaneous moment, and the relationship between the power factor angle and the droop of the converter voltage phase and amplitude, calculate the compensation amount for the converter voltage phase and amplitude, and add the compensation amount to the forward path with the given converter voltage phase and amplitude.

[0101] Specifically, the formulas for calculating the power factor angle and the converter voltage phase are as follows:

[0102] ;

[0103] In the formula, θ 1ref This is the setpoint value for the converter voltage phase after the low-voltage control method is added;

[0104] The formula for calculating the converter voltage phase compensation value is as follows:

[0105] ;

[0106] In the formula, θ 1com The compensation value for the converter voltage phase during a fault (e.g.) Figure 4 Module 1), k p1 and k i1 These are the proportional and integral coefficients of the converter voltage phase compensation PI regulator, respectively.

[0107] The formulas for calculating the power factor angle and the converter voltage amplitude are as follows:

[0108] ;

[0109] In the formula, U vscref This is the setpoint value for the converter voltage amplitude after the low-voltage control method is added;

[0110] The formula for calculating the voltage amplitude compensation value of the converter is as follows:

[0111] ;

[0112] In the formula, U vsccom The compensation value for the instantaneous voltage amplitude of the converter during a fault (e.g.) Figure 4 Module 2), k p2 and k i2 These are the proportional coefficient and integral coefficient of the PI regulator for voltage amplitude compensation in the converter, respectively.

[0113] Low voltage ride-through control methods can improve the overload capacity and current withstand capability of the device during faults, and enhance the reactive power support capability of the power grid while meeting the safety constraints of the converter.

[0114] S5: Using the power control method and low voltage ride-through control method of the three-droop structure system, generate the d-axis and q-axis reference voltage vectors and the reference electrical angle of the converter;

[0115] Specifically, the calculation formulas for the d-axis and q-axis reference voltage vectors of the converter are as follows:

[0116] ;

[0117] In the formula, U md ref , U mq ref These are the d-axis and q-axis reference voltage vectors of the converter, respectively.

[0118] The formula for calculating the converter reference electrical angle is as follows:

[0119]

[0120] In the formula, ωt This is the reference electrical angle for the converter.

[0121] This step lays the foundation for subsequent converter SVPWM.

[0122] S6: Based on the d-axis and q-axis reference voltage vectors of the inverter and the reference electrical angle of the inverter, calculate the voltage vector required by the inverter and combine it with SVPWM to generate the drive signals of each bridge arm switching device in the inverter to apply control to the system, including the following sub-steps:

[0123] S61: Motor d-axis and q-axis reference voltage vectors generated according to the converter power control method. u md ref , u mq ref and converter reference electrical angle ωt The voltage components are converted to a two-phase stationary coordinate system using the Park transformation (e.g., ...). Figure 3 As shown in module 10, the inverter reference voltage vector is obtained;

[0124] Specifically, it is calculated using the following formula:

[0125] ;

[0126] In the formula, u mα ref , u mβ ref For inverters in α-β The reference voltage vector required for the axis.

[0127] S62: Execute the SVPWM algorithm (e.g., based on the inverter reference voltage vector) Figure 3 As shown in module 11, it mainly includes sector determination of the reference voltage vector, calculation of the action time of non-zero and zero vectors in each sector, and determination of the vector switching point of each sector. Finally, a triangular carrier signal of a certain frequency is used to compare with the vector switching point of each sector, so as to generate the PWM pulse signal required by the converter.

[0128] Figure 5 and Figure 6 The figure shows the simulation waveforms when the initial active power input to the grid is 1 p.u. and the reactive power is 0.3 p.u. At 2 s, when the grid voltage symmetrically drops to 0.6 p.u., the simulation waveforms of the grid-connected system with the open winding motor interface, without converter phase-amplitude compensation control, are shown below. Figure 5 As shown, the system experiences severe instantaneous overcurrent, and the converter output power overshoot is even greater, resulting in a slow response. Therefore, amplitude and phase compensation of the converter is necessary to suppress the system output current. Figure 6As can be seen, after adding the VSC voltage phase-amplitude compensation method, instantaneous overcurrent is effectively suppressed. The grid-connected current does not exceed 1.15 times the rated grid-connected current throughout the process. It can also provide a certain amount of reactive power to the grid for voltage support in accordance with national standards. The power response speed is faster, meeting the design requirements, and it also has good current limiting capability.

[0129] Through the above embodiments of the present invention, a power transient control strategy is studied for an open-winding motor interface grid-connected system topology, in which an open-winding synchronous motor is connected in series with a new energy power generation converter and then connected to the AC grid. By designing the system's apparent power setpoint and power factor angle setpoint, a three-droop relationship is established: apparent power versus open-winding synchronous motor excitation voltage droop, and power factor angle versus converter voltage phase and amplitude droop, thus forming a converter control method. Based on the constraints of the converter's short-circuit current and the reactive power support requirements of the device, a transient overcurrent suppression method for instantaneous compensation of the new energy converter voltage phase-amplitude is designed, thereby achieving a low-voltage ride-through method. Through the above low-voltage ride-through control method, the transient support capability of the designed new topology is realized.

[0130] This application introduces a synchronous motor between the new energy converter and the power grid. From the perspective of the power grid port, its grid connection is essentially a motor, which solves the technical problem of low short-circuit current tolerance of traditional power electronic converters and improves the safety, stability and active support capabilities of the power grid.

[0131] Figure 7 This is a block diagram illustrating a low-voltage ride-through control device for an open-winding motor interface grid-connected system according to an exemplary embodiment. (Refer to...) Figure 7 The device includes:

[0132] Acquisition module 1 is used to acquire the active power and reactive power given by the power grid dispatching system.

[0133] The first calculation module 2 is used to calculate the system apparent power setpoint and power factor angle setpoint based on the given active power and reactive power values;

[0134] The first design module 3 is used to design a three-droop structure system power control method based on the system apparent power setpoint, power factor angle setpoint, and reactive power setpoint. This method has a droop structure for apparent power on motor excitation voltage, and a droop structure for power factor angle on converter voltage phase and amplitude. The method takes the motor excitation voltage and the converter d and q axis reference voltage vectors as direct control targets. By actively constructing the system voltage vector triangle corresponding to the power setpoint, the expected active power and reactive power setpoints are achieved.

[0135] The second design module 4 is used to design a low voltage ride-through control method for new energy converters based on the safety constraints of the converter short-circuit current and the reactive power support requirements of the power grid. This method compensates for the amplitude droop and phase droop of the converter at the moment of power grid fault, and indirectly suppresses the current flowing through the stator of the motor by reducing the reactance voltage drop on the motor, thereby achieving low voltage ride-through.

[0136] Generation module 5 is used to generate the converter d-axis and q-axis reference voltage vectors and the converter reference electrical angle through the power control method and low voltage ride-through control method of the three-droop structure system.

[0137] The control module 6 is used to calculate the voltage vector required by the inverter based on the d-axis and q-axis reference voltage vectors of the inverter and the reference electrical angle of the inverter, and to generate drive signals for each bridge arm switching device in the inverter in combination with SVPWM, so as to apply control to the system.

[0138] Regarding the apparatus in the above embodiments, the specific manner in which each module performs its operation has been described in detail in the embodiments related to the method, and will not be elaborated upon here.

[0139] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this application according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0140] Accordingly, this application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; and when the one or more programs are executed by the one or more processors, causing the one or more processors to implement the low voltage ride-through control method for an open-winding motor interface grid-connected system as described above.

[0141] Accordingly, this application also provides a computer-readable storage medium storing computer instructions that, when executed by a processor, implement the low-voltage ride-through control method for an open-winding motor interface grid-connected system as described above.

[0142] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the claims.

[0143] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A low-voltage ride-through control method for an open-winding motor interface grid-connected system, characterized in that, include: Obtain the active and reactive power setpoints provided by the power grid dispatching system; Based on the given active power and reactive power values, calculate the system apparent power setpoint and power factor angle setpoint; Based on the system apparent power setpoint, power factor angle setpoint, and reactive power setpoint, a three-droop structure system power control method is designed, where apparent power droops with respect to motor excitation voltage, and power factor angle droops with respect to converter voltage phase and amplitude. This method takes the motor excitation voltage and the converter d-axis and q-axis reference voltage vectors as direct control targets, and actively constructs the system voltage vector triangle corresponding to the power setpoint to achieve the expected active and reactive power setpoints. Based on the safety constraints of the converter short-circuit current and the reactive power support requirements of the power grid, a low-voltage ride-through control method for new energy converters is designed. This method compensates for the amplitude droop and phase droop of the converter during the instant of a power grid fault. By reducing the reactance voltage drop on the motor, it indirectly suppresses the current flowing through the motor stator, thereby achieving low-voltage ride-through. The power control method and low voltage ride-through control method of the three-droop structure system are used to generate the d-axis and q-axis reference voltage vectors and the reference electrical angle of the converter. Based on the d-axis and q-axis reference voltage vectors and the reference electrical angle of the inverter, the voltage vector required by the inverter is calculated and combined with SVPWM to generate the drive signals of each bridge arm switching device in the inverter to apply control to the system.

2. The low-voltage ride-through control method for an open-winding motor interface grid-connected system according to claim 1, characterized in that, Based on the given active and reactive power values, calculate the system apparent power setpoint and power factor angle setpoint, including: The apparent power setpoint and power factor angle setpoint of the system are calculated using the following formulas respectively; ； In the formula: S ref This is the system apparent power setpoint; P ref The active power setpoint for power grid dispatch; Q ref The reactive power setpoint for power grid dispatching; φ ref This is the given value for the power factor angle.

3. The low-voltage ride-through control method for an open-winding motor interface grid-connected system according to claim 1, characterized in that, Based on the system's apparent power setpoint, power factor angle setpoint, and reactive power setpoint, a three-droop structure system power control method is designed, where apparent power droops with respect to motor excitation voltage, and power factor angle droops with respect to converter voltage phase and amplitude. This method includes: For the system apparent power setpoint S Sagging, sagging coefficient is k 1. Obtain the excitation voltage u f ; For the power factor angle given value φ Sagging, sagging coefficient is k 2. Furthermore, a phase synchronization and accurate tracking circuit is added to the forward path of the converter phase differential to obtain the converter phase. θ 1; For the power factor angle given value φ Sagging, Sagging Factor k 3. A phase synchronization element is added to the forward path where the converter voltage amplitude is drooping to obtain the converter voltage amplitude. U vsc ; Through excitation voltage u f Indirect control of open-winding synchronous motor voltage U s Converter voltage phase θ 1 and converter voltage amplitude U vsc Direct control actively constructs the system voltage vector triangle, thereby achieving system power control.

4. The low-voltage ride-through control method for an open-winding motor interface grid-connected system according to claim 3, characterized in that, The additional amount of the phase synchronization element is calculated using the following formula: ； In the formula, θ com Additional quantity for the voltage phase synchronization stage of the converter; Δ θ 0 represents the initial phase difference between the converter voltage phase and the grid voltage phase; Δ θ The instantaneous phase difference between the converter voltage phase and the grid voltage phase during a fault; The additional amount for accurate tracking is obtained using the following formula: ； In the formula, θ q Additional parameters for accurate voltage phase tracking of the converter; k pq and k iq These are the proportional and integral coefficients of the PI regulator, which are additional factors for accurate phase tracking of the converter. Q ref The reactive power setpoint for power grid dispatching; Q This refers to the reactive power of the power grid.

5. The low-voltage ride-through control method for an open-winding motor interface grid-connected system according to claim 3, characterized in that, Actively constructing the system voltage vector triangle to achieve system power control is accomplished through the following calculation formula: The steady-state voltage of the system is obtained by the following formula: ； In the formula: U vsc For converter voltage, U s The voltage of the open-winding synchronous motor. U g This is the grid voltage. E 0 represents the induced electromotive force of the open-winding synchronous motor, and j is the imaginary unit. I X is the current flowing through the grid connection point. s For the stator reactance of the motor, ω L is the rotor speed of the motor. md The d-axis inductance of the motor. I f This refers to the excitation current of an open-winding synchronous motor. The steady-state current of the system is obtained by the following formula: ； The steady-state power of the system is obtained by the following formula: ； In the formula: P and Q are the active power and reactive power of the system, respectively.

6. The low-voltage ride-through control method for an open-winding motor interface grid-connected system according to claim 1, characterized in that, Based on the safety constraints of the converter's short-circuit current and the reactive power support requirements of the power grid, a low-voltage ride-through control method for new energy converters is designed, including: (1) Collect the three-phase stator current of the motor and the three-phase voltage of the power grid, and calculate the reactive power at the grid connection point; (2) Based on the reactive power at the grid connection point and the rated current constraint of the converter, calculate the phase difference between the converter voltage and the grid voltage after instantaneous fault compensation; (3) Based on the phase difference between the instantaneous converter voltage and the grid voltage during the fault, and the relationship between the power factor angle and the phase and amplitude droop of the converter voltage, calculate the compensation amount of the converter voltage phase and amplitude, and add the compensation amount to the forward path of the given converter voltage phase and amplitude.

7. The low-voltage ride-through control method for an open-winding motor interface grid-connected system according to claim 6, characterized in that, (1) The formula for calculating the reactive power at the grid connection point is as follows: ； In the formula, Q out1 The reactive power at the grid connection point before the fault. U g1 The three-phase voltage of the power grid before the fault. I 1 represents the three-phase stator current of the motor before the fault. φ 1 represents the power factor angle at the grid connection point before the fault; The formula for calculating reactive power after a short-circuit fault in the power grid is as follows: ； In the formula, Q out2 This refers to the reactive power at the grid connection point after a fault. U g2 The three-phase voltage of the power grid after the fault. I 2 represents the three-phase stator current of the motor after the fault. φ 2 represents the power factor angle at the grid connection point after the fault; (2) The formula for calculating the phase difference between the converter voltage and the grid voltage after the instantaneous fault compensation is as follows: To simultaneously satisfy the converter's short-circuit current capacity constraint and reactive power support, the power factor angle at the grid connection point after a fault must be... φ The formula for calculating 2 is as follows: ； In the formula, I gmax This ensures that the converter can withstand the maximum short-circuit current capacity. (3) The calculation formula for the compensation amount of the voltage phase and amplitude of the converter is as follows: The formulas for calculating the power factor angle and the converter voltage phase are as follows: ； In the formula, θ 1ref This is the setpoint value for the converter voltage phase after the low-voltage control method is added; The formula for calculating the converter voltage phase compensation value is as follows: ； In the formula, θ 1com This is the compensation value for the converter voltage phase during a fault. k p1 and k i1 These are the proportional and integral coefficients of the converter voltage phase compensation PI regulator, respectively. The formulas for calculating the power factor angle and the converter voltage amplitude are as follows: ； In the formula, U vscref This is the setpoint value for the converter voltage amplitude after the low-voltage control method is added; The formula for calculating the voltage amplitude compensation value of the converter is as follows: ； In the formula, U vsccom This is the compensation value for the instantaneous converter voltage amplitude during a fault. k p2 and k i2 These are the proportional coefficient and integral coefficient of the PI regulator for voltage amplitude compensation in the converter, respectively.

8. The low-voltage ride-through control method for an open-winding motor interface grid-connected system according to claim 1, characterized in that, Based on the d-axis and q-axis reference voltage vectors of the inverter and the reference electrical angle of the inverter, the required voltage vector of the inverter is calculated and combined with SVPWM to generate drive signals for each bridge arm switching device in the inverter, so as to apply control to the system, including: Based on the d-axis and q-axis reference voltage vectors of the inverter, the Park transformation is used to convert them into voltage components in a two-phase stationary coordinate system, thus obtaining the inverter reference voltage vector. Based on the inverter reference voltage vector, the SVPWM algorithm is executed to generate the PWM pulse signal required by the converter, and then the drive signal of each bridge arm switching device in the inverter is generated to control the system.

9. A low-voltage ride-through control device for an open-winding motor interface grid-connected system, characterized in that, include: The data acquisition module is used to acquire the active and reactive power setpoints given by the power grid dispatching system. The first calculation module is used to calculate the system apparent power setpoint and power factor angle setpoint based on the active power and reactive power setpoints. The first design module is used to design a three-droop structure system power control method based on the system apparent power setpoint, power factor angle setpoint, and reactive power setpoint. This method has the apparent power drooping with respect to the motor excitation voltage, the power factor angle drooping with respect to the converter voltage phase and amplitude, and takes the motor excitation voltage and the converter d-axis and q-axis reference voltage vectors as direct control targets. By actively constructing the system voltage vector triangle corresponding to the power setpoint, the expected active power and reactive power setpoints are achieved. The second design module is used to design a low-voltage ride-through control method for new energy converters based on the safety constraints of the converter short-circuit current and the reactive power support requirements of the power grid. This method compensates for the amplitude droop and phase droop of the converter at the moment of power grid fault, and indirectly suppresses the current flowing through the stator of the motor by reducing the reactance voltage drop on the motor, thereby achieving low-voltage ride-through. The generation module is used to generate the converter's d-axis and q-axis reference voltage vectors and the converter's reference electrical angles through the power control method and low-voltage ride-through control method of the three-droop structure system. The control module is used to calculate the voltage vector required by the inverter based on the d-axis and q-axis reference voltage vectors of the inverter and the reference electrical angle of the inverter, and to generate drive signals for each bridge arm switching device in the inverter in combination with SVPWM, so as to apply control to the system.

10. An electronic device, characterized in that, include: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in any one of claims 1-8.

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