Converter low voltage ride through control active current reference set value determination method, device and equipment

Abstract

The invention relates to a method, a device and equipment for determining an active current reference set value for low voltage ride through control of a converter. The method comprises the following steps: acquiring parameter data and an active current reference given mode of a power grid, and calculating to obtain a reactive current reference given value and active power reference data according to the parameter data and the active current reference given mode; capacity constraint data and transient stability constraint data are obtained through calculation according to the reactive current reference given value and the parameter data, and a constraint limitation area is determined according to the capacity constraint data and the transient stability constraint data; if the active power reference data is in the constraint limited area, taking the active power reference data as an active power reference set value; if the active power reference data is not in the constraint limited area, adjusting the reactive current coefficient, the line resistance or the reactive current coefficient until the active power reference data in the constraint limited area is obtained, and taking the active power reference data as an active power reference set value; and the active current reference set value of the low-voltage ride-through control of the converter is determined.

Description

Technical Field

[0001] This application relates to the field of low voltage ride-through technology in power systems, and in particular to a method, apparatus and equipment for determining the active current reference setpoint for low voltage ride-through control of a converter. Background Technology

[0002] In the power industry, due to the volatility of renewable energy generation, equipping power grids with energy storage for peak and valley regulation is a crucial means of maintaining grid stability. As the interface between energy storage batteries and the grid, the performance of the converter PCS (Power Conversion System) is critical to the stable absorption of renewable energy. Currently, the converter PCS mainly deployed in actual power grids is based on a grid-following control strategy. A typical system block diagram of a converter PCS is shown below. Figure 8 and Figure 9 As shown. The grid-connected converter PCS includes a current control loop and a phase-locked loop. Its essential mechanism is to control the converter PCS into a controlled current source according to the phase of the terminal voltage, and then inject / absorb active and reactive power into the grid according to the dispatch instructions.

[0003] Low-voltage ride-through is a crucial test that must be completed before grid-connected power equipment (such as converter PCS) is put into actual field operation. Essentially, it ensures that the grid-connected power equipment can remain connected and not disconnected from the grid in the event of a grid fault. Low-voltage ride-through standards include... Figure 10 As shown, when the voltage amplitude at the inverter terminals is above the voltage profile line, the inverter should remain connected to the grid and should not disconnect from it. Simultaneously, to maintain grid voltage stability, the grid connection guidelines require the energy storage converter (PCS) to output reactive current to support the grid voltage. Current energy storage converters (PCS) need to meet the reactive current requirements in "GB_T34120-2023 Technical Requirements for Electrochemical System Energy Storage Converters" during low-voltage ride-through testing, as shown in the formula... As shown in the formula: ΔI t K1 is the dynamic reactive current increment output by the energy storage converter PCS; K1 is the proportional coefficient of the dynamic reactive current output by the energy storage converter PCS, which is not less than 1.5 and not greater than 3; U t I is the ratio of the actual voltage to the rated voltage at the AC port of the energy storage converter PCS. N This refers to the rated output current value of the AC port of the energy storage converter PCS.

[0004] Current grid connection standards do not specify requirements for active current during low-voltage circuit breaking. However, in actual grid operation, converter PCS is required to generate active current to the fullest extent possible according to equipment capacity. When implementing this strategy, under certain grid operating conditions, the inverter in the converter PCS may become unstable. For example, under a short-circuit ratio SCR of 1.2, with grid line impedance reactance Xg / line impedance resistance Rg = 10, steady-state charging active power of 0.9 pu, and capacitive reactive current of 0.59 pu, under three-phase zero-voltage circuit breaking conditions, when the active current coefficient is set to -0.05 pu, the output current reverses and becomes positive. Figure 11 As shown in the figure, when the extended fault time of the power grid is set to 1.15s, it can be seen that the active current does not stabilize during the zero-speed-through period, but instead exhibits low-frequency oscillations, such as... Figure 12 As shown.

[0005] like Figure 13 As shown, the typical phase-locked loop principle of a grid-type converter (PCS) is to control the q-axis component V of the converter's terminal voltage through PI control. pccq Controlled to zero. In other words, the condition for a phase-locked loop to have a stable equilibrium point is the first equation, which is: In the formula, V g Indicates the amplitude of the grid voltage. and X represents the reference values ​​for the d-axis and q-axis current loops, respectively. g and R g Let represent the reactance and resistance values ​​of the line impedance, respectively, and δ represent the phase. Transforming the first equation yields the second equation, which is: .like Figure 14 As shown, the solid line represents V under normal operating conditions. g The sin(δ) curve, with the dashed line representing V during the low-crossing period. g The sin(δ) curve, the steady-state operating point of the phase-locked loop under normal operating conditions is as follows: Figure 14 As shown at point e in the diagram, if the system has a steady-state operating point during the fault period, let's assume it's point c. Then the condition for the phase-locked loop to have an equilibrium point during the low-voltage break-in period is: That is, it should be ensured that the black dashed straight line and the dashed curve intersect at a point. Under the condition of short-circuit ratio SCR=1.2, Xg / Rg=10, steady-state charging active power of 0.9 pu, capacitive reactive current of 0.59 pu, and three-phase zero-voltage operation, when the active current coefficient is set to -0.05 pu, the corresponding grid... It is -0.095, while the grid voltage V g It is 0.05. Summary of the Invention

[0006] The application provides a method, device and equipment for determining an active current reference setting value of low voltage ride through control of a converter, to solve the problem of low frequency oscillation in the process of low voltage ride through of a power grid.

[0007] To achieve the above object, the application provides the following technical scheme.

[0008] In one aspect, the application provides a method for determining an active current reference setting value of low voltage ride through control of a converter, comprising the following steps:

[0009] obtaining parameter data of a power grid and an active current reference given mode, wherein the power grid comprises a converter, the parameter data comprises voltage amplitude, rated voltage, rated current, maximum allowable current amplitude, line reactance, line resistance and control coefficients of the converter, the control coefficients comprise reactive current coefficients and active current coefficients;

[0010] calculating a reactive current reference given value according to the reactive current coefficients, the line reactance, the voltage amplitude, the rated voltage and the rated current, and calculating active power reference data according to the active current reference given mode, the active current coefficients, the rated current and the maximum allowable current amplitude;

[0011] calculating capacity constraint data and transient stability constraint data according to the reactive current reference given value and the parameter data, and determining a constraint limited region according to the capacity constraint data and the transient stability constraint data;

[0012] if the active power reference data is in the constraint limited region, taking the active power reference data as an active power reference setting value of the converter, and if the active power reference data is not in the constraint limited region, adjusting the reactive current coefficients, the line resistance or the reactive current coefficients until the active power reference data in the constraint limited region is obtained, and taking the active power reference data as the active power reference setting value of the converter.

[0013] Preferably, the adjusting of the reactive current coefficients until the active power reference data in the constraint limited region is obtained, and the taking of the active power reference data as the active power reference setting value of the converter comprise:

[0014] adjusting the value of the active current coefficients to obtain updated active current coefficients;

[0015] According to the rated current and the active current update coefficient calculation, active power reference update data is obtained as adjusted active power reference data until the active power reference update data is within the constraint limit region, and the active power reference update data is set as the active power reference setting value of the converter.

[0016] Preferably, the line resistance is adjusted until the active power reference data is within the constraint limit region, and the active power reference data is set as the active power reference setting value of the converter includes:

[0017] The line resistance is adjusted to obtain a line update resistance.

[0018] According to the line update resistance, the constraint limit region is adjusted to obtain a constraint limit update region as the constraint limit region until the active power reference data is within the constraint limit update region, and the active power reference data is set as the active power reference setting value of the converter.

[0019] Preferably, the reactive current coefficient is adjusted until the active power reference data is within the constraint limit region, and the active power reference data is set as the active power reference setting value of the converter includes:

[0020] The value of the reactive current coefficient is adjusted to obtain a reactive current update coefficient.

[0021] According to the reactive current update coefficient, the reactive current reference given value and the active power reference data are adjusted to obtain a corresponding reactive current reference given update value and active power reference update data, and the active power reference update data is set as adjusted active power reference data.

[0022] According to the active power reference update data, the constraint limit region is adjusted to obtain a constraint limit update region as the constraint limit region until the adjusted active power reference update data is within the constraint limit update region, and the active power reference update data is set as the active power reference setting value of the converter.

[0023] Preferably, according to the reactive current reference given value and the parameter data calculation, capacity constraint data and transient stability constraint data are obtained; and the constraint limit region is determined according to the capacity constraint data and the transient stability constraint data includes:

[0024] According to the reactive current reference given value and the maximum allowed current amplitude calculation, a first active current reference upper limit value and a first active current reference lower limit value are obtained.

[0025] calculating, according to the reactive current reference given value, the rated voltage, the line reactance and the line resistance, a second active current reference upper limit value and a second active current reference lower limit value;

[0026] selecting the greater value from the first active current reference lower limit value and the second active current reference lower limit value as the minimum value of the constraint limited region, and selecting the smaller value from the first active current reference upper limit value and the second active current reference upper limit value as the maximum value of the constraint limited region;

[0027] The capacity constraint data includes a first active current reference upper limit value and a first active current reference lower limit value, and the transient stability constraint data includes a second active current reference upper limit value and a second active current reference lower limit value.

[0028] In another aspect, a device for determining an active current reference setting value of a converter low voltage ride through control is provided, including a data acquisition module, a reference data calculation module, a constraint region determination module and an active power determination module.

[0029] The data acquisition module is configured to acquire parameter data of a power grid and an active current reference given mode, the power grid including a converter, and the parameter data including voltage amplitude, rated voltage, rated current, maximum allowable current amplitude, line reactance, line resistance and control coefficients of the converter, the control coefficients including reactive current coefficients and active current coefficients.

[0030] The reference data calculation module is configured to calculate, according to the reactive current coefficients, the line reactance, the voltage amplitude, the rated voltage and the rated current, a reactive current reference given value; and calculate, according to the active current reference given mode, the active current coefficients, the rated current and the maximum allowable current amplitude, active power reference data.

[0031] The constraint region determination module is configured to calculate, according to the reactive current reference given value and the parameter data, capacity constraint data and transient stability constraint data; and determine a constraint limited region according to the capacity constraint data and the transient stability constraint data.

[0032] The active power determination module is configured to, according to the active power reference data being in the constraint limited region, take the active power reference data as an active power reference setting value of the converter; or, according to the active power reference data not being in the constraint limited region, adjust the reactive current coefficients, the line resistance or the reactive current coefficients until the active power reference data in the constraint limited region is obtained, and take the active power reference data as the active power reference setting value of the converter.

[0033] Preferably, the active power determination module is further configured to adjust the value of the active current coefficient to obtain an updated active current coefficient; and calculate the active power reference updated data as the adjusted active power reference data according to the rated current and the updated active current coefficient until the active power reference updated data is within the constraint limit region, and set the active power reference updated data as the active power reference setting value of the converter.

[0034] Preferably, the active power determination module is further configured to adjust the line resistance to obtain an updated line resistance; and adjust the constraint limit region according to the updated line resistance to obtain an updated constraint limit region as the constraint limit region until the active power reference data is within the updated constraint limit region, and set the active power reference data as the active power reference setting value of the converter.

[0035] Preferably, the active power determination module is further configured to adjust the value of the active current coefficient to obtain an updated active current coefficient; and adjust the active current reference given value and the active power reference data according to the updated active current coefficient to obtain an updated active current reference given value and an updated active power reference data, and set the updated active power reference data as the adjusted active power reference data; adjust the constraint limit region according to the updated active power reference data to obtain an updated constraint limit region as the constraint limit region until the adjusted active power reference updated data is within the updated constraint limit region, and set the active power reference updated data as the active power reference setting value of the converter.

[0036] In another aspect, a terminal device is provided, comprising a processor and a memory;

[0037] The memory is configured to store program code and transmit the program code to the processor.

[0038] The processor is configured to execute the above-mentioned method for determining the active current reference setting value of the converter low voltage ride through control according to the instructions in the program code.

[0039] The method comprises the following steps: acquiring parameter data of a power grid and an active current reference setting mode, the power grid comprising a converter, the parameter data comprising voltage amplitude, rated voltage, rated current, maximum allowable current amplitude, line reactance, line resistance, and control coefficients of the converter, the control coefficients comprising a reactive current coefficient and an active current coefficient; calculating a reactive current reference setting value according to the reactive current coefficient, the line reactance, the voltage amplitude, the rated voltage, and the rated current; calculating active power reference data according to the active current reference setting mode, the active current coefficient, the rated current, and the maximum allowable current amplitude; calculating capacity constraint data and transient stability constraint data according to the reactive current reference setting value and the parameter data; determining a constraint limited region according to the capacity constraint data and the transient stability constraint data; if the active power reference data is in the constraint limited region, taking the active power reference data as an active power reference setting value of the converter; if the active power reference data is not in the constraint limited region, adjusting the reactive current coefficient, the line resistance, or the reactive current coefficient until the active power reference data in the constraint limited region is obtained, and taking the active power reference data as the active power reference setting value of the converter.

[0040] From the above technical solutions, the application has the following advantages: the method for determining the active current reference setting value of the converter low-voltage ride-through control obtains the active power reference data and the constraint limited region by processing the parameter data of the power grid and the active current reference setting mode, then judges whether the active power reference data is in the constraint limited region, if not, adjusts the reactive current coefficient, the line resistance, or the reactive current coefficient until the active power reference data meeting the capacity constraint and the transient stability constraint condition is obtained as the active power reference setting value of the converter, and the active power reference setting value is used to control the operation of the converter in the power grid, thereby avoiding the occurrence of low-frequency oscillation phenomenon caused by the full output of the active current according to the capacity limit in the traditional scheme, and solving the technical problem of the low-frequency oscillation phenomenon caused by the capacity-limited output of the active power of the existing grid-connected converter PCS in the low-voltage ride-through process of the power grid.

[0041] The active current reference setting value determination device of the converter low voltage ride through control processes the parameter data of the power grid and the active current reference given mode through a data acquisition module, a reference data calculation module, a constraint region determination module and an active power determination module to obtain active power reference data and a constraint limited region, and then judges whether the active power reference data is within the constraint limited region. If not, the reactive current coefficient, line resistance or reactive current coefficient is adjusted until the active power reference data that meets the capacity constraint and transient stability constraint condition is obtained as the active power reference setting value of the converter, so as to realize the determination of the active current reference setting value of the converter in the power grid during voltage drop and realize the determination of the active current reference setting value of the converter low voltage ride through control. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0043] Figure 1 The step flow chart of the active current reference setting value determination method of the converter low voltage ride through control according to the embodiments of the present application;

[0044] Figure 2 The frame schematic diagram of the active current reference setting value determination method of the converter low voltage ride through control according to the embodiments of the present application;

[0045] Figure 3 The schematic diagram of the constraint limited region in the active current reference setting value determination method of the converter low voltage ride through control according to the embodiments of the present application;

[0046] Figure 4 The output waveform diagram during zero penetration under the traditional scheme;

[0047] Figure 5 The output waveform diagram during zero penetration in the active current reference setting value determination method of the converter low voltage ride through control according to the embodiments of the present application;

[0048] Figure 6 The frame schematic diagram of the active current reference setting value determination device of the converter low voltage ride through control according to the embodiments of the present application;

[0049] Figure 7 The schematic diagram of the terminal device according to the embodiments of the present application;

[0050] Figure 8A system block diagram of an existing grid-connected inverter of the grid-following type;

[0051] Figure 9 A simplified block diagram of an existing grid-connected inverter of the grid-following type;

[0052] Figure 10 A voltage interval diagram for maintaining grid-connected operation of an existing converter PCS;

[0053] Figure 11 A simulation waveform diagram during zero-crossing of an existing converter PCS;

[0054] Figure 12 A waveform diagram of an extended fault time during zero-crossing of an existing converter PCS;

[0055] Figure 13 A control block diagram of a phase-locked loop of an existing grid-connected inverter of the grid-following type;

[0056] Figure 14 A diagram of phase-locked loop stabilization of an existing grid-connected inverter of the grid-following type.

[0057] wherein, in Figure 13 , V pcc represents a common grid point voltage, V pccd and V pccq represent d-axis and q-axis components after Park transformation of V pcc , ω0 represents a rated angular frequency, k p and k i respectively represent a proportional coefficient and an integral coefficient of a PI controller in the phase-locked loop, and θ represents a phase angle output by the phase-locked loop. DETAILED DESCRIPTION

[0058] In order to make the objectives, characteristics and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the embodiments described below are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0059] In the description of the embodiments of the present application, the terms “first” and “second” are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with “first” and “second” can explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of “a plurality of” is two or more, unless otherwise specifically limited.

[0060] In the embodiments of the present application, unless specifically defined and limited otherwise, the terms "mounting", "connection", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integrated; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0061] The embodiments of the present application provide a method, device and equipment for determining active current reference setting value of low voltage ride through control of converter, which solves the technical problem of low frequency oscillation phenomenon in the process of low voltage ride through of power grid, in which the existing grid-connected converter PCS adopts capacity limiting output active power.

[0062] Embodiment one:

[0063] Figure 1 The step flow chart of the method for determining active current reference setting value of low voltage ride through control of converter described in the embodiments of the present application, Figure 2 The frame schematic diagram of the method for determining active current reference setting value of low voltage ride through control of converter described in the embodiments of the present application.

[0064] As shown in Figure 1 and Figure 2 The embodiments of the present application provide a method for determining active current reference setting value of low voltage ride through control of converter, comprising the following steps:

[0065] S1. Obtain parameter data of power grid and active current reference given mode, the power grid comprising a converter, the parameter data comprising voltage amplitude, rated voltage, rated current, maximum allowable current amplitude, line reactance, line resistance of the power grid, and control coefficient of the converter, the control coefficient comprising reactive current coefficient and active current coefficient.

[0066] It should be noted that in step S1, the parameters of the power grid input converter and the active current reference given mode and the control coefficient of the converter are obtained, which provides data for calculating the active power reference setting value under the condition of meeting two types of constraints (capacity constraint and transient stability constraint) in the subsequent steps. In the present embodiment, the parameter data comprises voltage amplitude V g , rated voltage V rate , rated current I rate , maximum allowable current amplitude I max , line reactance X g , line resistance R g and control coefficient of the converter, the control coefficient comprising reactive current coefficient k q and active current coefficient kp .

[0067] S2. Calculate the reactive current reference given value according to the reactive current coefficient, line reactance, voltage amplitude, rated voltage and rated current; calculate the active power reference data according to the active current reference given mode, active current coefficient, rated current and maximum allowed current amplitude.

[0068] It should be noted that in step S2, the reactive current reference given value and the active power reference data are calculated according to the parameter data obtained in step S1, so as to provide data for setting the active power reference value under the conditions of satisfying two types of constraints (capacity constraint and transient stability constraint) in the subsequent steps.

[0069] In the embodiment of the present application, the reactive current reference given value is calculated according to the reactive current coefficient, line reactance, voltage amplitude, rated voltage and rated current by using a reactive current formula; the reactive current formula is:

[0070]

[0071] In the formula, I qref is the reactive current reference given value, k p is the reactive current coefficient, V g is the voltage amplitude, V rate is the rated voltage, and I rate is the rated current.

[0072] In the embodiment of the present application, the active power reference data is calculated according to the active current reference given mode, active current coefficient, rated current and maximum allowed current amplitude by using an active current formula.

[0073] It should be noted that if the active current reference given mode is the given mode of sending out as much as possible, the active current formula is . If the active current reference given mode is the given mode of sending out active current according to a certain coefficient, the active current formula is I dref =-k p ×I rate , in the formula, I dref is the active power reference data.

[0074] S3. Calculate the capacity constraint data and the transient stability constraint data according to the reactive current reference given value and the parameter data; determine the constraint limited region according to the capacity constraint data and the transient stability constraint data.

[0075] It should be noted that in step S3, the reactive current reference given value is first calculated according to step S2, and the capacity constraint data and transient stability constraint data are calculated according to the parameter data obtained in step S1, and then the constraint limit region is determined according to the capacity constraint data and the transient stability constraint data.

[0076] S4. If the active power reference data is in the constraint limit region, the active power reference data is set as the active power reference setting value of the converter; if the active power reference data is not in the constraint limit region, the reactive current coefficient, the line resistance or the reactive current coefficient is adjusted until the active power reference data in the constraint limit region is obtained, and the active power reference data is set as the active power reference setting value of the converter.

[0077] It should be noted that in step S4, it is judged whether the active power reference data calculated in step S2 is in the constraint limit region determined in step S3, and if not, the reactive current coefficient, the line resistance or the reactive current coefficient is adjusted until the active power reference data that meets the conditions of the two types of constraints (capacity constraint and transient stability constraint) is obtained as the active power reference setting value of the converter, so as to realize the determination of the active current reference setting value of the converter in the power grid during voltage drop. In the embodiment, the capacity constraint is constituted by the capacity constraint data, and the transient stability constraint is constituted by the transient stability constraint data.

[0078] In the embodiment of the present application, the method for determining the active current reference setting value of the converter in low voltage ride through control is to process the parameter data of the power grid and the active current reference given mode to obtain the active power reference data and the constraint limit region, and then judge whether the active power reference data is in the constraint limit region, and if not, adjust the reactive current coefficient, the line resistance or the reactive current coefficient until the active power reference data that meets the conditions of the capacity constraint and the transient stability constraint is obtained as the active power reference setting value of the converter, so as to realize the determination of the active current reference setting value of the converter in the power grid during voltage drop, and realize the determination of the active current reference setting value of the converter in low voltage ride through control.

[0079] It should be noted that the method for determining the active current reference setting value of the converter in low voltage ride through control gives a suitable active power reference setting value to control the operation of the converter in the power grid, and avoids the occurrence of low frequency oscillation phenomenon caused by the full output of the active current in the traditional scheme according to the capacity limit. In other embodiments, the method for determining the active current reference setting value of the converter in low voltage ride through control can also be applied to all power equipment with grid-connected control strategies.

[0080] The application provides a method for determining an active current reference setting value of a converter low-voltage ride-through control, which comprises obtaining parameter data of a power grid and an active current reference given mode, the power grid comprising a converter, the parameter data comprising voltage amplitude, rated voltage, rated current, maximum allowable current amplitude, line reactance, line resistance of the power grid, and control coefficients of the converter, the control coefficients comprising reactive current coefficients and active current coefficients; calculating a reactive current reference given value according to the reactive current coefficients, the line reactance, the voltage amplitude, the rated voltage, and the rated current; calculating active power reference data according to the active current reference given mode, the active current coefficients, the rated current, and the maximum allowable current amplitude; calculating capacity constraint data and transient stability constraint data according to the reactive current reference given value and the parameter data; determining a constraint limited region according to the capacity constraint data and the transient stability constraint data; if the active power reference data is within the constraint limited region, taking the active power reference data as the active power reference setting value of the converter; if the active power reference data is not within the constraint limited region, adjusting the reactive current coefficients, the line resistance, or the reactive current coefficients until the active power reference data within the constraint limited region is obtained, and taking the active power reference data as the active power reference setting value of the converter. The method for determining the active current reference setting value of the converter low-voltage ride-through control obtains the active power reference data and the constraint limited region by processing the parameter data of the power grid and the active current reference given mode, and then judges whether the active power reference data is within the constraint limited region, if not, adjusts the reactive current coefficients, the line resistance, or the reactive current coefficients until the active power reference data under the conditions of the capacity constraint and the transient stability constraint is obtained as the active power reference setting value of the converter, and the active power reference setting value is used to control the operation of the converter in the power grid, thereby avoiding the occurrence of low-frequency oscillation phenomenon caused by the full output of the active current under the capacity limitation in the traditional scheme, and solving the technical problem of the low-frequency oscillation phenomenon caused by the capacity-limited output of the active power of the existing grid-connected converter PCS in the low-voltage ride-through process of the power grid.

[0081] In an embodiment of the application, the capacity constraint data and the transient stability constraint data are calculated according to the reactive current reference given value and the parameter data; and the constraint limited region is determined according to the capacity constraint data and the transient stability constraint data, which comprises:

[0082] The first active current reference upper limit value and the first active current reference lower limit value are calculated according to the reactive current reference given value and the maximum allowable current amplitude;

[0083] The second active current reference upper limit value and the second active current reference lower limit value are calculated according to the reactive current reference given value, the rated voltage, the line reactance, and the line resistance;

[0084] The greater value between the first active current reference lower limit value and the second active current reference lower limit value is selected as the minimum value of the constraint limit region, and the smaller value between the first active current reference upper limit value and the second active current reference upper limit value is selected as the maximum value of the constraint limit region.

[0085] The capacity constraint data includes the first active current reference upper limit value and the first active current reference lower limit value, and the transient stability constraint data includes the second active current reference upper limit value and the second active current reference lower limit value.

[0086] It should be noted that the first active current reference upper limit value and the first active current reference lower limit value are calculated by using a capacity constraint formula according to the given value of the reactive current reference and the maximum allowed current amplitude. , wherein I max is the maximum allowed current amplitude, I dref_lowerlimtit1 is the first active current reference lower limit value, and I dref_upperlimtit1 is the first active current reference upper limit value. The second active current reference upper limit value and the second active current reference lower limit value are calculated by using a transient stability constraint formula according to the given value of the reactive current reference, the rated voltage, the line reactance, and the line resistance.

[0087]

[0088] , wherein I dref_lowerlimtit2 is the second active current reference lower limit value, and I dref_upperlimtit2 is the second active current reference upper limit value. In the embodiment, the capacity constraint condition is , and the transient stability constraint condition is .

[0089] In an embodiment of the present application, the reactive current coefficient is adjusted until the active power reference data in the constraint limit region is obtained, and the active power reference data is taken as the active power reference setting value of the converter.

[0090] The value of the active current coefficient is adjusted to obtain an updated active current coefficient.

[0091] The active power reference updated data is calculated according to the rated current and the updated active current coefficient, and is taken as the adjusted active power reference data until the active power reference updated data is in the constraint limit region, and the active power reference updated data is taken as the active power reference setting value of the converter.

[0092] It should be noted that the value of the active current coefficient k p is adjusted by using the active current formula to adjust the active power reference data I drefthe value of the line resistance, so that the active power reference data I dref satisfy the constraint conditions in the constraint defined region, the constraint conditions including capacity constraint conditions and transient stability constraint conditions.

[0093] In an embodiment of the present application, the line resistance is adjusted until the active power reference data in the constraint defined region is obtained, and the active power reference data is taken as the active power reference setting value of the converter, including:

[0094] The line resistance is adjusted to obtain an updated line resistance;

[0095] The constraint defined region is adjusted according to the updated line resistance to obtain an updated constraint defined region as the constraint defined region, until the active power reference data is in the updated constraint defined region, and the active power reference data is taken as the active power reference setting value of the converter.

[0096] It should be noted that the line resistance R g is adjusted to achieve adjustment of the values of the second active current reference lower limit value I dref_lowerlimtit2 and the second active current reference upper limit value I dref_upperlimtit2 through the transient stability constraint formula, so that the constraint defined region obtained in step S3 is adjusted to obtain an updated constraint defined region, until the active power reference data I dref calculated in step S2 satisfies the constraint conditions of the updated constraint defined region.

[0097] In an embodiment of the present application, the reactive current coefficient is adjusted until the active power reference data in the constraint defined region is obtained, and the active power reference data is taken as the active power reference setting value of the converter, including:

[0098] The value of the reactive current coefficient is adjusted to obtain an updated reactive current coefficient;

[0099] The reactive current reference given value and the active power reference data are adjusted according to the updated reactive current coefficient to obtain corresponding updated reactive current reference given value and updated active power reference data, and the updated active power reference data is taken as the adjusted active power reference data;

[0100] The constraint defined region is adjusted according to the updated active power reference data to obtain an updated constraint defined region as the constraint defined region, until the adjusted active power reference data is in the updated constraint defined region, and the active power reference data is taken as the active power reference setting value of the converter.

[0101] It should be noted that the reactive current coefficient k qThe reactive current update coefficient is obtained by updating the reactive current value through the reactive current formula. Based on the reactive current update coefficient, the first active current reference lower limit value I is adjusted through the capacity constraint formula and the transient stability constraint formula. dref_lowerlimtit1 The first active current reference upper limit value I dref_upperlimtit1 Second active current reference lower limit I dref_lowerlimtit2 Second active current reference upper limit I dref_upperlimtit2 The value is adjusted to obtain the constraint limit region obtained in step S3, thus obtaining the constraint limit update region, until the active power reference data I calculated in step S2 is obtained. dref The constraints limiting the update region are met. Active power reference update data is obtained using the active current formula based on the reactive current update coefficient. The first active current reference lower limit value I is then adjusted using the capacity constraint formula and transient stability constraint formula based on the reactive current update coefficient. dref_lowerlimtit1 The first active current reference upper limit value I dref_upperlimtit1 Second active current reference lower limit I dref_lowerlimtit2 Second active current reference upper limit I dref_upperlimtit2 The value is adjusted to obtain the constraint limit region obtained in step S3, and the constraint limit update region is obtained until the active power reference update data meets the constraint conditions of the constraint limit update region.

[0102] Figure 3 This is a schematic diagram of the constraint-limited region in the converter low-voltage ride-through control active current reference setpoint determination method described in the embodiments of this application. Figure 4 This is the output waveform during zero-passage in the traditional scheme. Figure 5 This is an output waveform diagram during the zero-voltage ride-through period in the converter low-voltage ride-through control active current reference setpoint determination method described in this application embodiment. Figure 4 and Figure 5 In the figure, (a) shows the low-pass flag, (b) shows the PI output of the phase-locked loop, (c) shows the active power and reactive power, and (d) shows the active current and reactive current.

[0103] like Figure 3 As shown in the embodiments of this application, the active current reference setpoint for converter low-voltage ride-through control is determined according to the method for determining the active current reference setpoint, considering both capacity constraints and transient stability constraints, as shown in the figure. Figure 3 The shaded area in the image shows the active power reference setting. Figure 3 The reactive current coefficient includes a region where the active power reference setpoint is less than that under the capacity-only constraint (constraint 1). Constraint 1 is as shown in the capacity constraint, and constraint 2 is as shown in the transient stability constraint. Figure 3 In the middle, 0.05 times the voltage amplitude V greactive current coefficient k q is 1.6, the maximum allowed current amplitude I max is taken as 1.1 p.u., the ratio of line reactance X g to line resistance R g is taken as 10, the constraint limit area is shown as the shaded area in Figure 3 .

[0104] In the embodiments of the present application, the converter low voltage ride through control active current reference setting value determination method is verified under the following working conditions, the test working condition is short circuit ratio SCR=1.2, the zero penetration working condition with the ratio of line reactance X g to line resistance R g is 10, the output results under the traditional scheme and the converter low voltage ride through control active current reference setting value determination method are shown in Figure 4 and Figure 5 , wherein the converter low voltage ride through control active current reference setting value determination method reduces the active current coefficient during zero penetration from 0.05 under the traditional scheme to 0.04; also reduces the value of line resistance R g under the traditional scheme. As shown in Figure 4 , the active current waveform during zero penetration under the traditional scheme oscillates. When the converter low voltage ride through control active current reference setting value determination method is adopted, as shown in Figure 5 , the output of active current and the output of phase-locked are stable.

[0105] Embodiment two:

[0106] Figure 6 is a schematic diagram of the framework of the converter low voltage ride through control active current reference setting value determination device described in the embodiments of the present application.

[0107] As shown in Figure 6 , the present application provides a converter low voltage ride through control active current reference setting value determination device, which comprises a data acquisition module 10, a reference data calculation module 20, a constraint area determination module 30 and an active power determination module 40;

[0108] The data acquisition module 10 is used to acquire the parameter data of the power grid and the active current reference given mode, the power grid comprising a converter, the parameter data comprising the voltage amplitude, the rated voltage, the rated current, the maximum allowed current amplitude, the line reactance, the line resistance of the power grid and the control coefficient of the converter, the control coefficient comprising the reactive current coefficient and the active current coefficient;

[0109] The reference data calculation module 20 is configured to calculate the reactive current reference given value according to the reactive current coefficient, the line reactance, the voltage amplitude, the rated voltage and the rated current calculation, and to calculate the active power reference data according to the active current reference given mode, the active current coefficient, the rated current and the maximum allowable current amplitude calculation.

[0110] The constraint region determination module 30 is configured to calculate the capacity constraint data and the transient stability constraint data according to the reactive current reference given value and the parameter data calculation, and to determine the constraint limited region according to the capacity constraint data and the transient stability constraint data.

[0111] The active power determination module 40 is configured to set the active power reference data as the active power reference setting value of the converter when the active power reference data is in the constraint limited region, or to adjust the reactive current coefficient, the line resistance or the reactive current coefficient until the active power reference data in the constraint limited region is obtained, and then set the active power reference data as the active power reference setting value of the converter.

[0112] It should be noted that the content of the modules in the device of the second embodiment has been described in the content of the steps of the method of the first embodiment, and the content of the modules of the device of the second embodiment will not be repeated in this embodiment. In this embodiment, the device for determining the active current reference setting value of the converter low voltage ride through control processes the parameter data of the power grid and the active current reference given mode through the data acquisition module, the reference data calculation module, the constraint region determination module and the active power determination module, to obtain the active power reference data and the constraint limited region, and then determines whether the active power reference data is in the constraint limited region. If not, the reactive current coefficient, the line resistance or the reactive current coefficient is adjusted until the active power reference data that meets the capacity constraint and the transient stability constraint condition is obtained as the active power reference setting value of the converter, so as to determine the active current reference setting value of the converter in the voltage drop period of the power grid and determine the active current reference setting value of the converter low voltage ride through control.

[0113] In the embodiments of the present application, the active power determination module 40 is further configured to adjust the value of the active current coefficient to obtain an updated active current coefficient, and to calculate the updated active power reference data as the adjusted active power reference data according to the rated current and the updated active current coefficient, until the updated active power reference data is in the constraint limited region, and then set the updated active power reference data as the active power reference setting value of the converter.

[0114] In the embodiment of the present application, the active power determination module 40 is further configured to adjust the line resistance to obtain an updated line resistance; adjust the constraint limit region according to the updated line resistance to obtain an updated constraint limit region as the constraint limit region, until the active power reference data is within the updated constraint limit region, and set the active power reference data as the active power reference setting value of the converter.

[0115] In the embodiment of the present application, the active power determination module 40 is further configured to adjust the value of the reactive current coefficient to obtain an updated reactive current coefficient; adjust the reactive current reference given value and the active power reference data according to the updated reactive current coefficient to obtain an updated reactive current reference given value and an updated active power reference data, and set the updated active power reference data as the adjusted active power reference data; adjust the constraint limit region according to the updated active power reference data to obtain an updated constraint limit region as the constraint limit region, until the updated active power reference data is within the updated constraint limit region, and set the updated active power reference data as the active power reference setting value of the converter.

[0116] Embodiment three:

[0117] Figure 7 A schematic diagram of the terminal device according to the embodiment of the present application.

[0118] As shown in Figure 7 the embodiment of the present application provides a terminal device, which comprises a processor and a memory;

[0119] The memory is configured to store program code and transmit the program code to the processor.

[0120] The processor is configured to execute the instructions in the program code to perform the active current reference setting value determination method for low voltage ride through control of the converter.

[0121] It should be noted that the processor is configured to execute the instructions in the program code to perform the steps in the active current reference setting value determination method for low voltage ride through control of the converter. Alternatively, the processor executes the computer program to realize the functions of the modules / units in each system / device embodiment.

[0122] For example, the computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present application. One or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe the execution process of the computer program in the terminal device.

[0123] The terminal device can be a desktop computer, a notebook computer, a palm computer, a cloud server, and the like. The terminal device can include, but is not limited to, a processor, a memory. Those skilled in the art can understand that the terminal device is not limited to the above, and can include more or less components, or combine some components, or different components, for example, the terminal device can also include an input / output device, a network access device, a bus, and the like.

[0124] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and the like. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0125] The memory can be an internal storage unit of the terminal device, for example, a hard disk or a memory of the terminal device. The memory can also be an external storage device of the terminal device, for example, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, and the like. Further, the memory can include both the internal storage unit and the external storage device of the terminal device. The memory is used to store computer programs and other programs and data required by the terminal device. The memory can also be used to temporarily store data that has been output or will be output.

[0126] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system, device and unit described above can refer to the corresponding process in the foregoing method embodiments, which will not be described herein.

[0127] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other manners. For example, the described device embodiments are merely schematic. For example, the division of the units is only a logical function division. There can be another division manner for the actual implementation, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between different units, can be indirect couplings or communication connections through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0128] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e., can be located in one place, or can be distributed on multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0129] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can be physically present separately, or two or more units can be integrated into one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0130] The integrated unit, if realized in the form of a software functional unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the part that contributes to the prior art, or all or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0131] The above embodiments are merely used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for determining the reference setpoint of active current for low-voltage ride-through control of a converter, characterized in that, The method comprises the following steps: obtaining parameter data and active current reference setting mode of a power grid, the power grid comprising a converter, the parameter data comprising voltage amplitude, rated voltage, rated current, maximum allowable current amplitude, line reactance, line resistance of the power grid, and control coefficients of the converter, the control coefficients comprising reactive current coefficient and active current coefficient; calculating a reactive current reference setting value according to the reactive current coefficient, the line reactance, the voltage amplitude, the rated voltage and the rated current; calculating active power reference data according to the active current reference setting mode, the active current coefficient, the rated current and the maximum allowable current amplitude; calculating capacity constraint data and transient stability constraint data according to the reactive current reference setting value and the parameter data; determining a constraint limited region according to the capacity constraint data and the transient stability constraint data; if the active power reference data is in the constraint limited region, setting the active power reference data as an active power reference setting value of the converter; if the active power reference data is not in the constraint limited region, adjusting the reactive current coefficient, the line resistance or the reactive current coefficient until the active power reference data in the constraint limited region is obtained, and setting the active power reference data as the active power reference setting value of the converter.

2. The method for determining the reference setpoint of active current for converter low-voltage ride-through control according to claim 1, characterized in that, adjusting the value of the active current coefficient to obtain an active current updated coefficient; calculating active power reference updated data as the adjusted active power reference data according to the rated current and the active current updated coefficient until the active power reference updated data is in the constraint limited region, and setting the active power reference updated data as the active power reference setting value of the converter. adjusting the line resistance until the active power reference data in the constraint limited region is obtained, and setting the active power reference data as the active power reference setting value of the converter, which comprises:

3. The method for determining the reference setpoint of active current for converter low-voltage ride-through control according to claim 1, characterized in that, adjusting the line resistance to obtain an updated line resistance; adjusting the constraint limited region according to the updated line resistance to obtain an updated constraint limited region as the constraint limited region until the active power reference data is in the updated constraint limited region, and setting the active power reference data as the active power reference setting value of the converter. adjusting the value of the reactive current coefficient to obtain a reactive current updated coefficient; 4. The method for determining the reference setpoint of active current for converter low-voltage ride-through control according to claim 1, characterized in that, calculating active power reference updated data as the adjusted active power reference data according to the rated current and the active current updated coefficient until the active power reference updated data is in the constraint limited region, and setting the active power reference updated data as the active power reference setting value of the converter. ​ The reactive current reference setpoint and the active power reference data are adjusted according to the reactive current update coefficient to obtain the corresponding reactive current reference setpoint update value and active power reference update data, and the active power reference update data is used as the adjusted active power reference data. The constraint-limited region is adjusted based on the active power reference update data to obtain a constraint-limited update region, which is then used as the constraint-limited region until the adjusted active power reference update data falls within the constraint-limited update region. This active power reference update data is then used as the active power reference setpoint of the converter.

5. The method for determining the reference setpoint of active current for converter low-voltage ride-through control according to any one of claims 1-4, characterized in that, Based on the reactive current reference setpoint and the parameter data, capacity constraint data and transient stability constraint data are calculated and obtained. The constraint-bound region is determined based on the capacity constraint data and transient stability constraint data, including: The first active current reference upper limit and the first active current reference lower limit are calculated based on the reactive current reference setpoint and the maximum allowable current amplitude. The second active current reference upper limit and the second active current reference lower limit are calculated based on the reactive current reference setpoint, the rated voltage, the line reactance and the line resistance. The larger value between the first active current reference lower limit and the second active current reference lower limit is selected as the minimum value of the constraint-limited region; the smaller value between the first active current reference upper limit and the second active current reference upper limit is selected as the maximum value of the constraint-limited region. The capacity constraint data includes a first active current reference upper limit and a first active current reference lower limit, and the transient stability constraint data includes a second active current reference upper limit and a second active current reference lower limit.

6. A device for determining the active current reference setpoint for low-voltage ride-through control of a converter, characterized in that, include: The module includes a data acquisition module, a reference data calculation module, a constraint region determination module, and an active power determination module. The data acquisition module is used to acquire the parameter data of the power grid and the active current reference setting method. The power grid includes a converter. The parameter data includes the voltage amplitude, rated voltage, rated current, maximum allowable current amplitude, line reactance, line resistance of the power grid, and the control coefficient of the converter. The control coefficient includes reactive current coefficient and active current coefficient. The reference data calculation module is used to calculate and obtain a reference given value for reactive current based on the reactive current coefficient, the line reactance, the voltage amplitude, the rated voltage and the rated current. Active power reference data is obtained by calculating based on the active current reference setting method, the active current coefficient, the rated current, and the maximum allowable current amplitude. The constraint region determination module is used to calculate, based on the reactive current reference given value and the parameter data, to obtain capacity constraint data and transient stability constraint data. The constraint-limited region is determined based on the capacity constraint data and transient stability constraint data; The active power determination module is configured to set the active power reference data as the active power reference setting value of the converter if the active power reference data is within the constraint limit region; or adjust the reactive current coefficient, the line resistance or the reactive current coefficient until the active power reference data is within the constraint limit region, and then set the active power reference data as the active power reference setting value of the converter.

7. The current transformer low voltage ride through control active current reference setting value determination device according to claim 6, characterized in that, The active power determination module is further configured to adjust the value of the active current coefficient to obtain an updated active current coefficient; calculate the updated active power reference data as the adjusted active power reference data according to the rated current and the updated active current coefficient until the updated active power reference data is within the constraint limit region, and then set the updated active power reference data as the active power reference setting value of the converter.

8. The current transformer low voltage ride through control active current reference setting value determination device according to claim 6, characterized in that, The active power determination module is further configured to adjust the line resistance to obtain an updated line resistance; adjust the constraint limit region according to the updated line resistance to obtain an updated constraint limit region as the constraint limit region until the active power reference data is within the updated constraint limit region, and then set the active power reference data as the active power reference setting value of the converter.

9. The current transformer low voltage ride through control active current reference setting value determination device according to claim 6, characterized in that, The active power determination module is further configured to adjust the value of the reactive current coefficient to obtain an updated reactive current coefficient; adjust the active power reference data and the reactive current reference given value according to the updated reactive current coefficient to obtain corresponding updated values of the reactive current reference given value and the active power reference data, and set the updated active power reference data as the adjusted active power reference data; adjust the constraint limit region according to the updated active power reference data to obtain an updated constraint limit region as the constraint limit region until the updated active power reference data is within the updated constraint limit region, and then set the updated active power reference data as the active power reference setting value of the converter.

10. A terminal device, comprising: The device comprises a processor and a memory. The memory is configured to store program code and transmit the program code to the processor. The processor is configured to execute the method according to any one of claims 1-6 according to instructions in the program code.

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