Low voltage ride through control method and device of converter

Abstract

The invention provides a low-voltage ride-through control method and device for a current converter, and the method comprises the steps: determining a d-axis current reference value of the current converter through the self-adaptive additional current of the current converter, and carrying out the low-voltage ride-through control of the current converter according to a q-axis current reference value and the d-axis current reference value. The adaptive additional current is considered, the mapping function of the q-axis voltage component to the track sensitivity is constructed, and the transient synchronization stability of the new energy station and the alternating current power grid can be ensured. The self-adaptive additional current obtained through the q-axis current component and the d-axis voltage component is negative, and the d-axis current reference value is equal to the sum of the d-axis current initial value and the self-adaptive additional current, so that the d-axis current reference value can be reduced, the deceleration energy of the new energy field station is increased, and the deceleration efficiency of the new energy field station is improved. The problem of transient synchronization instability of the new energy station under low voltage ride through is effectively solved.

Description

Technical Field

[0001] The present application relates to the technical field of new energy grid connection, and in particular to a low voltage ride through control method and device for a converter. Background Art

[0002] With the increase in the installed capacity of new energy stations, the problem of transient synchronization and stability of new energy grid-connected systems has become increasingly prominent. New energy stations can be connected to the AC power grid through converters. Usually, the port voltage of the converter can be measured through a phase-locked loop to achieve frequency synchronization between the converter and the AC power grid (which can also be understood as a virtual power angle). In an AC power grid with a low short-circuit ratio, due to the long electrical distance between the new energy station and the AC power grid, the equivalent reactance of the line between the converter and the AC power grid is large, and the anti-interference ability of the converter port voltage is poor. In the event of a transient fault such as a short circuit in the AC power grid, the port voltage fluctuates violently, the phase-locked loop may become transiently unstable, and the port voltage cannot be accurately tracked, which may lead to large-scale power switching of units in the new energy station, bringing a chain instability risk to the AC power grid.

[0003] For transient faults in the AC power grid, the low voltage ride-through method provided by related technologies usually only considers the reactive power support provided by the new energy station, and cannot guarantee the transient synchronization and stability of the new energy station and the AC power grid. Summary of the invention

[0004] In order to solve the problem that the existing technology cannot ensure the transient synchronization and stability of the new energy station and the AC power grid, the present application provides a low voltage ride-through control method for the converter, which may include:

[0005] The q-axis current reference value of the converter is determined according to the output voltage amplitude of the converter.

[0006] The adaptive additional current of the converter is determined according to the actual value of the output current and the actual value of the output voltage of the converter, and the d-axis current reference value of the converter is determined according to the adaptive additional current and the q-axis current reference value.

[0007] The converter is subjected to low voltage ride-through control according to the q-axis current reference value and the d-axis current reference value.

[0008] Optionally, the low voltage ride-through control method further includes:

[0009] The actual value of the output current of the converter is subjected to Parker transformation to obtain the q-axis current component and d-axis current component of the converter, and the actual value of the output voltage of the converter is subjected to Parker transformation to obtain the q-axis voltage component and d-axis voltage component of the converter.

[0010] In some possible implementations, determining the adaptive additional current of the converter according to the actual value of the output current and the actual value of the output voltage of the converter includes:

[0011] The sum of the q-axis current component and the d-axis voltage component is controlled in proportional-integral mode to obtain an adaptive additional current.

[0012] In some other possible implementations, determining the d-axis current reference value of the converter according to the adaptive additional current and the q-axis current reference value includes:

[0013] The initial value of the d-axis current of the converter is calculated according to the q-axis current reference value.

[0014] The d-axis current initial value and the adaptive additional current are superimposed to obtain the d-axis current reference value.

[0015] Exemplarily, determining a q-axis current reference value of the converter according to an output voltage amplitude of the converter includes:

[0016] The difference between the output voltage amplitude of the converter and the preset voltage reference value is proportionally controlled to obtain a q-axis current reference value.

[0017] Optionally, low voltage ride-through control is performed on the converter according to the q-axis current reference value and the d-axis current reference value, including:

[0018] The q-axis current reference value and the d-axis current reference value are subjected to current inner loop control to obtain the d-axis inner potential and the q-axis inner potential of the converter.

[0019] The q-axis voltage component is subjected to phase-locked loop control to obtain the phase-locked loop output phase.

[0020] According to the phase-locked loop output phase, the q-axis current component, the d-axis current component, the q-axis voltage component and the d-axis current component, the d-axis internal potential and the q-axis internal potential are subjected to Park inverse transformation to obtain a first control signal.

[0021] The first control signal is modulated to obtain a second control signal.

[0022] The inverter is controlled according to the second control signal.

[0023] Further, the q-axis current reference value and the d-axis current reference value are subjected to current inner loop control to obtain the d-axis inner potential and the q-axis inner potential of the converter, including:

[0024] The d-axis voltage component is filtered to obtain a d-axis first modulation voltage, and the q-axis voltage component is filtered to obtain a q-axis first modulation voltage.

[0025] The d-axis current component is multiplied by the reactance of the filter inductor connected to the converter to obtain the q-axis second modulation voltage, and the q-axis current component is multiplied by the reactance of the filter inductor connected to the converter to obtain the d-axis second modulation voltage.

[0026] The d-axis current reference value is subjected to proportional-integral control to obtain the d-axis third modulation voltage, and the q-axis current reference value is subjected to proportional-integral control to obtain the q-axis third modulation voltage.

[0027] The d-axis inner potential is calculated based on the d-axis first modulation voltage, the d-axis second modulation voltage, and the q-axis inner potential is calculated based on the first q-axis modulation voltage, the second q-axis modulation voltage, and the third q-axis modulation voltage.

[0028] Where, the electric potential in the d-axis is E d Satisfy E d =U d1 +U d3 -U d2 , E d represents the potential in the d-axis, U d1 represents the first modulation voltage of the d-axis, U d2 represents the d-axis second modulation voltage, U d3 represents the third modulation voltage of d axis. The potential E in q axis q Satisfy E q =U q1 +U q3 +U q2 , E q represents the potential in the q axis, U q1 represents the first modulation voltage on the q axis, U q2 represents the q-axis second modulation voltage, U q3 represents the q-axis third modulation voltage.

[0029] In some possible implementations, the low voltage ride through control method provided by the present application further includes:

[0030] The d-axis voltage component and the q-axis current component are superimposed as a mapping function of the q-axis voltage component to the trajectory sensitivity.

[0031] When the mapping function is greater than or equal to 0, the initial value of the d-axis current is used as the d-axis current reference value. When the mapping function is less than 0, the d-axis current reference value of the converter is determined according to the adaptive additional current and the q-axis current reference value.

[0032] In some other possible implementations, the low voltage ride through control method provided by the present application further includes:

[0033] When the output voltage amplitude is greater than the preset voltage reference value, the difference between the actual DC voltage value of the converter and the DC voltage reference value is proportionally and integrally controlled to obtain a d-axis current reference value.

[0034] When the output voltage amplitude is less than or equal to the preset voltage reference value, the difference between the actual reactive power value of the converter and the reactive power reference value is proportionally and integrally controlled to obtain the current reference value of the q-axis.

[0035] On the other hand, the present application also provides a low voltage ride through control device for a converter, which may include:

[0036] The first determination module is used to determine the q-axis current reference value of the converter according to the output voltage amplitude of the converter.

[0037] The second determination module is used to determine the adaptive additional current of the converter according to the actual value of the output current and the actual value of the output voltage of the converter, and to determine the d-axis current reference value of the converter according to the adaptive additional current and the q-axis current reference value.

[0038] The control module is used to perform low voltage ride-through control on the converter according to the q-axis current reference value and the d-axis current reference value.

[0039] Optionally, the low voltage ride through control device further includes a conversion module.

[0040] The conversion module is used to: perform a Parker transformation on the actual value of the output current of the converter to obtain the q-axis current component and the d-axis current component of the converter, and perform a Parker transformation on the actual value of the output voltage of the converter to obtain the q-axis voltage component and the d-axis voltage component of the converter.

[0041] In a possible implementation manner, the second determining module is specifically configured to:

[0042] The sum of the q-axis current component and the d-axis voltage component is controlled by proportional integral to obtain an adaptive additional current.

[0043] In another possible implementation manner, the second determining module is specifically configured to:

[0044] The initial value of the d-axis current of the converter is calculated according to the q-axis current reference value.

[0045] The d-axis current initial value and the adaptive additional current are superimposed to obtain the d-axis current reference value.

[0046] Exemplarily, the first determining module is specifically used for:

[0047] The difference between the output voltage amplitude of the converter and the preset voltage reference value is proportionally controlled to obtain a q-axis current reference value.

[0048] In yet another possible implementation, the control module is specifically configured to:

[0049] The q-axis current reference value and the d-axis current reference value are subjected to current inner loop control to obtain the d-axis inner potential and the q-axis inner potential of the converter.

[0050] The q-axis voltage component is subjected to phase-locked loop control to obtain the phase-locked loop output phase.

[0051] According to the phase-locked loop output phase, the q-axis current component, the d-axis current component, the q-axis voltage component and the d-axis current component, the d-axis internal potential and the q-axis internal potential are subjected to Park inverse transformation to obtain a first control signal.

[0052] The first control signal is modulated to obtain a second control signal.

[0053] The inverter is controlled according to the second control signal.

[0054] Furthermore, the control module is specifically used for:

[0055] The d-axis voltage component is filtered to obtain a d-axis first modulation voltage, and the q-axis voltage component is filtered to obtain a q-axis first modulation voltage.

[0056] The d-axis current component is multiplied by the reactance of the filter inductor connected to the converter to obtain the q-axis second modulation voltage, and the q-axis current component is multiplied by the reactance of the filter inductor connected to the converter to obtain the d-axis second modulation voltage.

[0057] The d-axis current reference value is subjected to proportional-integral control to obtain the d-axis third modulation voltage, and the q-axis current reference value is subjected to proportional-integral control to obtain the q-axis third modulation voltage.

[0058] The d-axis inner potential is calculated based on the d-axis first modulation voltage, the d-axis second modulation voltage, and the q-axis inner potential is calculated based on the first q-axis modulation voltage, the second q-axis modulation voltage, and the third q-axis modulation voltage.

[0059] Where, the electric potential in the d-axis is E d Satisfy E d =U d1 +U d3 -U d2 , E d represents the potential in the d-axis, U d1 represents the first modulation voltage of the d-axis, U d2 represents the d-axis second modulation voltage, U d3 represents the third modulation voltage of d axis. The potential E in q axis q Satisfy E q =U q1 +U q3 +U q2 , E q represents the potential in the q axis, U q1 represents the first modulation voltage on the q axis, U q2 represents the q-axis second modulation voltage, U q3represents the q-axis third modulation voltage.

[0060] Optionally, the second determining module is specifically used for:

[0061] The d-axis voltage component and the q-axis current component are superimposed as a mapping function of the q-axis voltage component to the trajectory sensitivity.

[0062] When the mapping function is greater than or equal to 0, the initial value of the d-axis current is used as the d-axis current reference value. When the mapping function is less than 0, the d-axis current reference value of the converter is determined according to the adaptive additional current and the q-axis current reference value.

[0063] Furthermore, the second determination module is also used to: when the output voltage amplitude is greater than a preset voltage reference value, perform proportional integral control on the difference between the actual DC voltage value of the converter and the DC voltage reference value to obtain a d-axis current reference value.

[0064] The first determination module is also used to: when the output voltage amplitude is less than or equal to the preset voltage reference value, perform proportional integral control on the difference between the actual reactive power value of the converter and the reactive power reference value to obtain the current reference value of the q-axis.

[0065] On the other hand, the present application also provides a computer device, including: one or more processors.

[0066] A processor is used to execute one or more programs.

[0067] When one or more programs are executed by one or more processors, the low voltage ride-through control method as described above is implemented.

[0068] In another aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, the above-mentioned low voltage ride-through control method is implemented.

[0069] Compared with the prior art, the beneficial effects of this application are:

[0070] The low voltage ride-through control method provided in the present application determines the d-axis current reference value of the converter through the adaptive additional current of the converter, and performs low voltage ride-through control on the converter according to the q-axis current reference value and the d-axis current reference value. The present application considers the adaptive additional current and can ensure the transient synchronization stability between the new energy station and the AC power grid.

[0071] This application constructs a mapping function of the q-axis voltage component to the trajectory sensitivity, and determines the d-axis current reference value through the mapping function to further ensure the transient synchronization stability of the new energy grid-connected system.

[0072] In the present application, the adaptive additional current obtained by the q-axis current component and the d-axis voltage component is negative. Since the d-axis current reference value is equal to the sum of the d-axis current initial value and the adaptive additional current, the d-axis current reference value can be reduced, thereby increasing the deceleration energy of the new energy station, effectively solving the problem of transient synchronous instability of the new energy station under low voltage crossing. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] In order to more clearly illustrate the technical solutions in the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0074] Figure 1 A schematic structural diagram of a new energy grid-connected system in an embodiment of the present application;

[0075] Figure 2 A schematic flow chart of a low voltage ride through control method in an embodiment of the present application;

[0076] Figure 3 Another schematic flow chart of the low voltage ride through control method in the embodiment of the present application;

[0077] Figure 4 A schematic diagram of a time domain response waveform obtained by using a low voltage ride-through control method provided by a related technology;

[0078] Figure 5 A schematic diagram of a time domain response waveform obtained by using the low voltage ride through control method provided by an embodiment of the present application;

[0079] Figure 6 A schematic structural diagram of a low voltage ride through control device in an embodiment of the present application. DETAILED DESCRIPTION

[0080] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0081] The terms "first", "second", etc. in the specification embodiments, claims, and drawings of the present application are only used for the purpose of distinguishing descriptions, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, including a series of steps or units. The method, system, product, or device is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

[0082] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0083] like Figure 1 As shown, the new energy grid-connected system may include a photovoltaic power station PV, a converter (taking a voltage source converter VSC as an example), a filter inductor L f 、Filter capacitor C f The low-voltage direct current output by the photovoltaic power station PV is converted into alternating current through the VSC and connected to the AC power grid. Figure 1 In, L g Indicates the inductance of the line, U g Indicates the voltage of the AC bus, R g Indicates the equivalent resistance of the line. abc Indicates the actual value of the converter output voltage (i.e. the actual value of the voltage at the grid connection point), I abc Indicates the actual value of the converter's output current (i.e. the actual value of the current at the grid connection point).

[0084] The present application embodiment provides a low voltage ride through control method for a converter, such as Figure 2 The low voltage ride through control method 100 comprises the following steps:

[0085] Step S1: According to the output voltage amplitude of the converter (U t (expressed) determines the q-axis current reference value of the converter. Figure 3 , according to the output voltage amplitude U t The q-axis current reference value is obtained by I qref2 express.

[0086] Step S2: According to the actual value of the output current I of the converter abc And the actual value of output voltage U abc Determine the adaptive additional current ΔI of the converter dref , according to the adaptive additional current ΔI dref and q-axis current reference value I qref2Determine the d-axis current reference value of the converter. Figure 3 , according to the adaptive additional current ΔI dref and q-axis current reference value I qref2 The obtained d-axis current reference value can be used dref2 express.

[0087] Step S3: According to the q-axis current reference value I qref2 and d-axis current reference value I dref2 Perform low voltage ride through control on the converter.

[0088] Optionally, the low voltage ride through control method 100 provided in the embodiment of the present application further includes:

[0089] refer to Figure 3 , the actual value of the converter output current I abc Perform Park transformation to obtain the q-axis current component of the converter (using I q ) and the d-axis current component (denoted by I d The actual value of the output voltage U abc Perform Park transformation to obtain the q-axis voltage component of the converter (using U q ) and the d-axis voltage component (U d express).

[0090] Optionally, the output voltage amplitude of the converter U t satisfy In step S1, according to the output voltage amplitude U t Determine the q-axis current reference value I of the converter qref2 ,include:

[0091] The output voltage amplitude of the converter is U t and preset voltage reference value (can be used with U ref It means that the difference of 0.9pu, etc. can be taken for proportional control and limiting, etc. to obtain the q-axis current reference value I qref2 . That is to say, it satisfies: I qref2 =-K(U ref -U t ), K represents the proportionality coefficient.

[0092] In some possible implementations, the low voltage ride through control method 100 provided in the embodiment of the present application further includes:

[0093] The d-axis voltage component U d and the q-axis voltage component U q The superposition is used as the mapping function of the q-axis voltage component to the trajectory sensitivity (which can be expressed by f(δ)). That is, it satisfies: f(δ)=U d+U q .

[0094] When the mapping function f(δ) is greater than or equal to 0, the initial value of the d-axis current (which can be expressed as I dref0 represents) as the d-axis current reference value I dref2 , that is I dref2 =I dref0 When the mapping function f(δ) is less than 0, the adaptive additional current ΔI dref and q-axis current reference value I qref2 Determine the d-axis current reference value I of the converter dref2 .

[0095] Optionally, in step S2, according to the actual value of the output current I of the converter abc And the actual value of output voltage U abc Determine the adaptive additional current ΔI of the converter dref ,include:

[0096] refer to Figure 3 , for the q-axis current component I q and the d-axis voltage component I d The sum of ΔI and ΔI is controlled by proportional integral control (PI control) and amplitude limiting to obtain the adaptive additional current ΔIdref. dref =k I ∫(U d +I q )dt, where k I represents the integral coefficient, and dt represents the derivative with respect to time t.

[0097] Exemplarily, according to the adaptive additional current ΔI dref and q-axis current reference value I qref2 Determine the d-axis current reference value I of the converter dref2 ,include:

[0098] refer to Figure 3 , according to the q-axis current reference value I qref2 Calculate the initial value of the converter's d-axis current I dref0 I dref0 satisfy Among them, I max Indicates the output current limit value of the converter.

[0099] Set the initial value of the d-axis current I dref0 and adaptive additional current ΔI dref Superposition, get the d-axis current reference value I dref2 . That is to say, it satisfies: I dref2 =I dref0 +ΔI dref .

[0100] In some possible implementations, the low voltage ride through control method 200 provided in the embodiment of the present application further includes:

[0101] At the output voltage amplitude U t Greater than the preset voltage reference value U ref (such as 0.9pu, etc.), the actual value of the DC voltage of the converter (U dc Indicated by U dcref The difference between the two is proportional-integral control to obtain the d-axis current reference value. Figure 3 , according to the actual value of DC voltage U dc And DC voltage reference value U dcref The d-axis current reference value is obtained by I dref1 express.

[0102] At the output voltage amplitude U t Less than or equal to the preset voltage reference value U ref (such as 0.9pu, etc.), the actual value of the reactive power of the converter (expressed in Q) and the reference value of the reactive power (expressed in Q ref The difference between the two is proportional-integral control to obtain the current reference value of the q axis. Figure 3 , according to the actual value of reactive power Q and the reference value of reactive power Q ref The current reference value of the q-axis is obtained by I qref1 express.

[0103] It can be seen that the d-axis current reference value and the q-axis current reference value can be obtained through the PQ control mode, and can also be obtained through the low voltage ride through (LVRT) mode (which can be called LVRT mode).

[0104] So, reference Figure 3 In the PQ control mode, the q-axis current reference value of the converter (which can be used with I qref It means that you can take I qref1 In LVRT mode, the q-axis current reference value I qref You can take I qref2 Similarly, in the PQ control mode, the d-axis current reference value of the converter (which can be expressed as I dref It means that you can take I dref1 In LVRT mode, the d-axis current reference value I dref You can take I dref2 .

[0105] Further, according to the q-axis current reference value I qref and d-axis current reference value Idref Perform low voltage ride-through control on the converter, including:

[0106] refer to Figure 3 , for the q-axis current reference value I qref and d-axis current reference value I dref Perform current inner loop control to obtain the d-axis inner potential of the converter (using E d ) and the potential in the q axis (denoted by E q express).

[0107] For the q-axis voltage component U q Perform phase-locked loop control and obtain the phase of the phase-locked loop output (using θ PLL For details, refer to Figure 3 , for the q-axis voltage component U q By performing proportional integral control (PI control), the angular frequency change △ω can be obtained. Adding it to the initial value of the angular frequency ω0, the angular frequency ω of the AC power grid can be obtained. By integrating the angular frequency ω of the AC power grid, the phase-locked loop output phase θ can be obtained. PLL .

[0108] According to the phase-locked loop output phase θ PLL , q-axis current component I q , d-axis current component I d , q-axis voltage component U q and the d-axis current component U d , for the electric potential E in the d-axis d and the q-axis potential E q Performing an inverse Park transform, a first control signal CS1 is obtained.

[0109] The first control signal CS1 is modulated (such as PWM modulation, etc.) to obtain the second control signal CS2.

[0110] The inverter is controlled according to the second control signal CS2.

[0111] Furthermore, for the q-axis current reference value I qref and d-axis current reference value I dref Perform current inner loop control to obtain the d-axis inner potential E of the converter d and the q-axis potential E q ,include:

[0112] For the d-axis voltage component U d Filter and obtain the d-axis first modulation voltage U d1 , and the q-axis voltage component U q Filter and obtain the first modulation voltage U of the q axis q1 . Figure 3 In, T vrepresents the filtering time constant, and s represents the Laplace operator.

[0113] The d-axis current component I d and the filter inductor L connected to the converter f The reactance is multiplied by the q-axis second modulation voltage U q2 , and the q-axis current component I q and filter inductor L f The reactance is multiplied by the d-axis second modulation voltage U d2 . refer to Figure 3 , it can be seen that satisfying U q2 =I d ωL f , U d2 =I q ωL f .

[0114] The d-axis current reference value I dref Perform proportional integral control to obtain the d-axis third modulation voltage U d3 , and the q-axis current reference value I qref Perform proportional integral control to obtain the q-axis third modulation voltage U q3 .

[0115] According to the d-axis first modulation voltage U d1 , d-axis second modulation voltage U d2 and the d-axis third modulation voltage U d3 Calculate the electric potential E in the d-axis d , and according to the first q-axis modulation voltage U q1 , the second q-axis modulation voltage U q2 and the third q-axis modulation voltage U q3 Calculate the potential E in the q axis q .

[0116] Where, the electric potential in the d-axis is E d Satisfy E d =U d1 +U d3 -U d2 , E d represents the potential in the d-axis, U d1 represents the first modulation voltage of the d-axis, U d2 represents the d-axis second modulation voltage, U d3 represents the third modulation voltage of d axis. The potential E in q axis q Satisfy E q =U q1 +U q3 +U q2 , E q represents the potential in the q axis, U q1 represents the first modulation voltage on the q axis, Uq2 represents the q-axis second modulation voltage, U q3 represents the q-axis third modulation voltage.

[0117] In order to analyze the transient synchronization stability of the converter during low voltage ride-through, a simulation system as shown in the attached figure is built in the Matlab / Simulink simulation platform. Figure 1 The new energy grid-connected system shown in the figure. It is assumed that a three-phase short circuit fault occurs in the power grid at t = 1s, and the fault lasts for 1s. The parameters of the new energy grid-connected system are shown in Table 1:

[0118] Table 1

[0119] Converter parameters Value [pu] AC grid parameters Value [pu] <![CDATA[K PLLp ]]> 10 <![CDATA[L g ]]> 0.05 <![CDATA[K PLLi ]]> 1600 <![CDATA[C f ]]> 0.05 <![CDATA[k ip ]]> 3 <![CDATA[k ii ]]> 1 <![CDATA[I dref ]]> 1 <![CDATA[I qref ]]> 0 <![CDATA[L f ]]> 0.1

[0120] In Table 1, K PLLp Represents the proportionality factor of the phase-locked loop, K PLLi Indicates the integral coefficient of the phase-locked loop, k ip Indicates U dc and U dcref The difference between Q and Q is controlled by proportional integral. ref Proportional coefficient for proportional-integral control, k ii Indicates U dc and U dcref The difference between Q and Q is controlled by proportional integral. ref The integral coefficient for proportional-integral control.

[0121] The time domain response waveform obtained by the low voltage ride-through control method provided by the relevant technology is as follows: Figure 4 As shown, the time domain response waveform obtained by the low voltage ride through control method provided by the embodiment of the present application is as follows Figure 5 shown. Figure 4 and Figure 5 In the equation, ω represents the angular frequency of the AC grid, δ represents the output phase of the converter, and X g Indicates the reactance of the line.

[0122] contrast Figure 4 and Figure 5 It can be found that the low voltage ride-through control method provided by the related art is unstable during the transient state of the AC power grid, and the output phase δ continues to increase. However, the low voltage ride-through control method provided by the embodiment of the present application is unstable during the transient state of the AC power grid due to I dref2 =I dref0 +ΔI dref And ΔI dref Less than 0, therefore, the embodiment of the present application reduces the d-axis current reference value and ensures transient stability, indicating the effectiveness of the low voltage ride-through control method provided by the embodiment of the present application.

[0123] Based on the same inventive concept, the embodiment of the present application also provides a low voltage ride through control device for a converter, such as Figure 6 The low voltage ride through control device 200 may include:

[0124] The first determination module 21 is used to determine the output voltage amplitude U of the converter according to the output voltage amplitude U t Determine the q-axis current reference value of the converter. Figure 3 , according to the output voltage amplitude U t The q-axis current reference value is obtained by I qref2 express.

[0125] The second determining module 22 is used to determine the actual value of the output current I of the converter. abc And the actual value of output voltage U abc Determine the adaptive additional current ΔI of the converter dref , according to the adaptive additional current ΔI dref and q-axis current reference value I qref2 Determine the d-axis current reference value of the converter. Figure 3 , according to the adaptive additional current ΔI dref and q-axis current reference value I qref2 The obtained d-axis current reference value can be used dref2 express.

[0126] The control module 23 is used to control the current reference value I of the q-axis current according to the qref2 and d-axis current reference value I dref2 Perform low voltage ride through control on the converter.

[0127] Optional, reference Figure 6 The low voltage ride through control device 200 further includes a transformation module 24 .

[0128] The transformation module 24 is used to: refer to Figure 3 , the actual value of the converter output current I abc Perform Park transformation to obtain the q-axis current component of the converter (using I q ) and the d-axis current component (denoted by I d The actual value of the output voltage U abc Perform Park transformation to obtain the q-axis voltage component of the converter (using U q ) and the d-axis voltage component (U d express).

[0129] In a possible implementation manner, the second determining module 22 is specifically configured to:

[0130] For the q-axis current component I q and the d-axis voltage component U dThe sum of ΔI and ΔI is proportional-integral controlled to obtain the adaptive additional current ΔIdref. dref =k I ∫(U d +I q )dt, where k I represents the integral coefficient, and dt represents the derivative with respect to time t.

[0131] In another possible implementation, the second determining module 22 is specifically configured to:

[0132] refer to Figure 3 , according to the q-axis current reference value I qref2 Calculate the initial value of the converter's d-axis current I dref0 I dref0 satisfy Among them, I max Indicates the output current limit value of the converter.

[0133] Set the initial value of the d-axis current I dref0 and adaptive additional current ΔI dref Superposition, get the d-axis current reference value I dref2 . That is to say, it satisfies: I dref2 =I dref0 +ΔI dref .

[0134] Optionally, the first determining module 21 is specifically configured to:

[0135] The output voltage amplitude of the converter is U t (U t satisfy ) and the preset voltage reference value (which can be ref It means that the difference of 0.9pu, etc. can be taken for proportional control and limiting, etc. to obtain the q-axis current reference value I qref2 . That is to say, it satisfies: I qref2 =-K(U ref -U t ), K represents the proportionality coefficient.

[0136] In yet another possible implementation, refer to Figure 3 , the control module 23 is specifically used for:

[0137] refer to Figure 3 , for the q-axis current reference value I qref and d-axis current reference value I dref Perform current inner loop control to obtain the d-axis inner potential of the converter (using E d ) and the potential in the q axis (denoted by E q express).

[0138] For the q-axis voltage component U q Perform phase-locked loop control and obtain the phase of the phase-locked loop output (using θ PLL For details, refer to Figure 3 , for the q-axis voltage component U q By performing proportional integral control (PI control), the angular frequency change △ω can be obtained. Adding it to the initial value of the angular frequency ω0, the angular frequency ω of the AC power grid can be obtained. By integrating the angular frequency ω of the AC power grid, the phase-locked loop output phase θ can be obtained. PLL .

[0139] According to the phase-locked loop output phase θ PLL , q-axis current component I q , d-axis current component I d , q-axis voltage component U q and the d-axis current component U d , for the electric potential E in the d-axis d and the q-axis potential E q Performing an inverse Park transform, a first control signal CS1 is obtained.

[0140] The first control signal CS1 is modulated (such as PWM modulation, etc.) to obtain the second control signal CS2.

[0141] The inverter is controlled according to the second control signal CS2.

[0142] Furthermore, the control module 23 is specifically used for:

[0143] For the d-axis voltage component U d Filter and obtain the d-axis first modulation voltage U d1 , and the q-axis voltage component U q Filter and obtain the first modulation voltage U of the q axis q1 .

[0144] The d-axis current component I d and the filter inductor L connected to the converter f The reactance is multiplied by the q-axis second modulation voltage U q2 , and the q-axis current component I q and filter inductor L f The reactance is multiplied by the d-axis second modulation voltage U d2 . refer to Figure 3 , it can be seen that satisfying U q2 =I d ωL f , U d2 =I q ωL f .

[0145] The d-axis current reference value I drefPerform proportional integral control to obtain the d-axis third modulation voltage U d3 , and the q-axis current reference value I qref Perform proportional integral control to obtain the q-axis third modulation voltage U q3 .

[0146] According to the d-axis first modulation voltage U d1 , d-axis second modulation voltage U d2 and the d-axis third modulation voltage U d3 Calculate the electric potential E in the d-axis d , and according to the first q-axis modulation voltage U q1 , the second q-axis modulation voltage U q2 and the third q-axis modulation voltage U q3 Calculate the potential E in the q axis q .

[0147] Where, the electric potential in the d-axis is E d Satisfy E d =U d1 +U d3 -U d2 , E d represents the potential in the d-axis, U d1 represents the first modulation voltage of the d-axis, U d2 represents the d-axis second modulation voltage, U d3 represents the third modulation voltage of d axis. The potential E in q axis q Satisfy E q =U q1 +U q3 +U q2 , E q represents the potential in the q axis, U q1 represents the first modulation voltage on the q axis, U q2 represents the q-axis second modulation voltage, U q3 represents the q-axis third modulation voltage.

[0148] Optionally, the second determining module 22 is specifically configured to:

[0149] The d-axis voltage component U d and the q-axis voltage component U q The superposition is used as the mapping function of the q-axis voltage component to the trajectory sensitivity (which can be expressed by f(δ)). That is, it satisfies: f(δ)=U d +U q .

[0150] When the mapping function f(δ) is greater than or equal to 0, the initial value of the d-axis current (which can be expressed as I dref0 represents) as the d-axis current reference value I dref2 , that is I dref2 =I dref0When the mapping function f(δ) is less than 0, the adaptive additional current ΔI dref and q-axis current reference value I qref2 Determine the d-axis current reference value I of the converter dref2 .

[0151] Furthermore, the second determining module 22 is further configured to: t Greater than the preset voltage reference value U ref (such as 0.9pu, etc.), the actual value of the DC voltage of the converter (U dc Indicated by U dcref The difference between the two is proportional-integral control to obtain the d-axis current reference value. Figure 3 , according to the actual value of DC voltage U dc And DC voltage reference value U dcref The d-axis current reference value is obtained by I dref1 express.

[0152] The first determining module 21 is further used to: t Less than or equal to the preset voltage reference value U ref (such as 0.9pu, etc.), the actual value of the reactive power of the converter (expressed in Q) and the reference value of the reactive power (expressed in Q ref The difference between the two is proportional-integral control to obtain the current reference value of the q axis. Figure 3 , according to the actual value of reactive power Q and the reference value of reactive power Q ref The current reference value of the q-axis is obtained by I qref1 express.

[0153] It can be seen that the d-axis current reference value and the q-axis current reference value can be obtained through the PQ control mode, and can also be obtained through the low voltage ride through (LVRT) mode (which can be called LVRT mode).

[0154] So, reference Figure 3 In the PQ control mode, the q-axis current reference value of the converter (which can be used with I qref It means that you can take I qref1 In LVRT mode, the q-axis current reference value I qref You can take I qref2 Similarly, in the PQ control mode, the d-axis current reference value of the converter (which can be expressed as I dref It means that you can take I dref1 In LVRT mode, the d-axis current reference value I dref You can take I dref2 .

[0155] Based on the same inventive concept, the embodiment of the present application also provides a computer device, which includes a processor and a memory, the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, which are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding functions, so as to implement the steps of the low voltage ride-through control method provided in the above embodiment.

[0156] Based on the same inventive concept, the embodiment of the present application also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in a computer device and, of course, an extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space that stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the low voltage ride-through control method provided in the above embodiment.

[0157] Those skilled in the art will appreciate that the embodiments of the application may be provided as methods, systems, or computer program products. Therefore, the application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0158] The application is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0159] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0160] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0161] The above are merely embodiments of the application and are not intended to limit the application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the application are included in the scope of the claims of the pending application.

Claims

1. A low voltage ride through control method for a converter, characterized in that: include: Determining a q-axis current reference value of the converter according to an output voltage amplitude of the converter; determining an adaptive additional current of the converter according to an actual value of the output current and an actual value of the output voltage of the converter, and determining a d-axis current reference value of the converter according to the adaptive additional current and the q-axis current reference value; The converter is subjected to low voltage ride-through control according to the q-axis current reference value and the d-axis current reference value.

2. The low voltage ride through control method according to claim 1, characterized in that: The low voltage ride through control method further includes: The actual value of the output current of the converter is subjected to a Park transformation to obtain the q-axis current component and the d-axis current component of the converter, and the actual value of the output voltage of the converter is subjected to a Park transformation to obtain the q-axis voltage component and the d-axis voltage component of the converter.

3. The low voltage ride through control method according to claim 2, characterized in that: The step of determining the adaptive additional current of the converter according to the actual value of the output current and the actual value of the output voltage of the converter comprises: Proportional-integral control is performed on the sum of the q-axis current component and the d-axis voltage component to obtain the adaptive additional current.

4. The low voltage ride through control method according to claim 1, characterized in that: The step of determining the d-axis current reference value of the converter according to the adaptive additional current and the q-axis current reference value comprises: Calculating the initial value of the d-axis current of the converter according to the q-axis current reference value; The d-axis current initial value and the adaptive additional current are superimposed to obtain the d-axis current reference value.

5. The low voltage ride through control method according to claim 1, characterized in that: The step of determining the q-axis current reference value of the converter according to the output voltage amplitude of the converter comprises: The difference between the output voltage amplitude of the converter and a preset voltage reference value is proportionally controlled to obtain the q-axis current reference value.

6. The low voltage ride through control method according to claim 2, characterized in that: The performing low voltage ride through control on the converter according to the q-axis current reference value and the d-axis current reference value comprises: Performing current inner loop control on the q-axis current reference value and the d-axis current reference value to obtain the d-axis inner potential and the q-axis inner potential of the converter; Performing phase-locked loop control on the q-axis voltage component to obtain a phase-locked loop output phase; According to the phase-locked loop output phase, the q-axis current component, the d-axis current component, the q-axis voltage component and the d-axis current component, performing a Park inverse transformation on the d-axis internal potential and the q-axis internal potential to obtain a first control signal; modulating the first control signal to obtain a second control signal; The converter is controlled according to the second control signal.

7. The low voltage ride through control method according to claim 6, characterized in that: The performing current inner loop control on the q-axis current reference value and the d-axis current reference value to obtain the d-axis inner potential and the q-axis inner potential of the converter includes: Filtering the d-axis voltage component to obtain a d-axis first modulation voltage, and filtering the q-axis voltage component to obtain a q-axis first modulation voltage; Multiplying the d-axis current component by the reactance of the filter inductor connected to the converter to obtain a q-axis second modulation voltage, and multiplying the q-axis current component by the reactance of the filter inductor connected to the converter to obtain a d-axis second modulation voltage; Performing proportional-integral control on the d-axis current reference value to obtain a d-axis third modulation voltage, and performing proportional-integral control on the q-axis current reference value to obtain a q-axis third modulation voltage; calculating the d-axis inner potential according to the d-axis first modulation voltage, the d-axis second modulation voltage, and the d-axis third modulation voltage, and calculating the q-axis inner potential according to the first q-axis modulation voltage, the second q-axis modulation voltage, and the third q-axis modulation voltage; Wherein, the d-axis inner potential satisfies E d =U d1 +U d3 -U d2 , E d represents the d-axis potential, U d1 represents the d-axis first modulation voltage, U d2 represents the d-axis second modulation voltage, U d3 represents the third modulation voltage of the d-axis; the potential in the q-axis satisfies E q =U q1 +U q3 +U q2 , E q represents the q-axis potential, U q1 represents the q-axis first modulation voltage, U q2 represents the q-axis second modulation voltage, U q3 represents the q-axis third modulation voltage.

8. The low voltage ride through control method according to claim 4, characterized in that: The low voltage ride through control method further includes: superimposing the d-axis voltage component and the q-axis current component as a mapping function of the q-axis voltage component to trajectory sensitivity; When the mapping function is greater than or equal to 0, the initial d-axis current value is used as the d-axis current reference value; when the mapping function is less than 0, the d-axis current reference value of the converter is determined according to the adaptive additional current and the q-axis current reference value.

9. The low voltage ride through control method according to claim 1, characterized in that: The low voltage ride through control method further includes: When the output voltage amplitude is greater than a preset voltage reference value, proportional-integral control is performed on the difference between the actual DC voltage value of the converter and the DC voltage reference value to obtain the d-axis current reference value; When the output voltage amplitude is less than or equal to a preset voltage reference value, a proportional-integral control is performed on the difference between the actual reactive power value of the converter and the reactive power reference value to obtain the current reference value of the q-axis.

10. A low voltage ride through control device for a converter, characterized in that: include: A first determination module, configured to determine a q-axis current reference value of the converter according to an output voltage amplitude of the converter; a second determination module, configured to determine an adaptive additional current of the converter according to an actual value of the output current and an actual value of the output voltage of the converter, and to determine a d-axis current reference value of the converter according to the adaptive additional current and the q-axis current reference value; A control module is used to perform low voltage ride-through control on the converter according to the q-axis current reference value and the d-axis current reference value.

11. The low voltage ride through control device according to claim 10, characterized in that: The low voltage ride through control device further includes a conversion module; The conversion module is used to: perform a Parker transformation on the actual value of the output current of the converter to obtain the q-axis current component and the d-axis current component of the converter, and perform a Parker transformation on the actual value of the output voltage of the converter to obtain the q-axis voltage component and the d-axis voltage component of the converter.

12. The low voltage ride through control device according to claim 11, characterized in that: The second determining module is specifically used for: Proportional-integral control is performed on the sum of the q-axis current component and the d-axis voltage component to obtain the adaptive additional current.

13. The low voltage ride through control method according to claim 10, characterized in that: The second determining module is specifically used for: Calculating the initial value of the d-axis current of the converter according to the q-axis current reference value; The d-axis current initial value and the adaptive additional current are superimposed to obtain the d-axis current reference value.

14. The low voltage ride through control device according to claim 10, characterized in that: The first determining module is specifically used for: The difference between the output voltage amplitude of the converter and a preset voltage reference value is proportionally controlled to obtain the q-axis current reference value.

15. The low voltage ride through control device according to claim 11, characterized in that: The control module is specifically used for: Performing current inner loop control on the q-axis current reference value and the d-axis current reference value to obtain the d-axis inner potential and the q-axis inner potential of the converter; Performing phase-locked loop control on the q-axis voltage component to obtain a phase-locked loop output phase; According to the phase-locked loop output phase, the q-axis current component, the d-axis current component, the q-axis voltage component and the d-axis current component, performing a Park inverse transformation on the d-axis internal potential and the q-axis internal potential to obtain a first control signal; modulating the first control signal to obtain a second control signal; The converter is controlled according to the second control signal.

16. The low voltage ride through control device according to claim 15, characterized in that: The control module is specifically used for: Filtering the d-axis voltage component to obtain a d-axis first modulation voltage, and filtering the q-axis voltage component to obtain a q-axis first modulation voltage; Multiplying the d-axis current component by the reactance of the filter inductor connected to the converter to obtain a q-axis second modulation voltage, and multiplying the q-axis current component by the reactance of the filter inductor connected to the converter to obtain a d-axis second modulation voltage; Performing proportional-integral control on the d-axis current reference value to obtain a d-axis third modulation voltage, and performing proportional-integral control on the q-axis current reference value to obtain a q-axis third modulation voltage; calculating the d-axis inner potential according to the d-axis first modulation voltage, the d-axis second modulation voltage, and the d-axis third modulation voltage, and calculating the q-axis inner potential according to the first q-axis modulation voltage, the second q-axis modulation voltage, and the third q-axis modulation voltage; Wherein, the d-axis inner potential satisfies E d =U d1 +U d3 -U d2 , E d represents the d-axis potential, U d1 represents the d-axis first modulation voltage, U d2 represents the d-axis second modulation voltage, U d3 represents the third modulation voltage of the d-axis; the potential in the q-axis satisfies E q =U q1 +U q3 +U q2 , E q represents the q-axis potential, U q1 represents the q-axis first modulation voltage, U q2 represents the q-axis second modulation voltage, U q3 represents the q-axis third modulation voltage.

17. The low voltage ride through control device according to claim 13, characterized in that: The second determining module is specifically used for: superimposing the d-axis voltage component and the q-axis current component as a mapping function of the q-axis voltage component to trajectory sensitivity; When the mapping function is greater than or equal to 0, the d-axis current initial value is used as the d-axis current reference value; When the mapping function is less than 0, a d-axis current reference value of the converter is determined according to the adaptive additional current and the q-axis current reference value.

18. The low voltage ride through control device according to claim 10, characterized in that: The second determination module is further used to: when the output voltage amplitude is greater than a preset voltage reference value, perform proportional integral control on the difference between the actual DC voltage value of the converter and the DC voltage reference value to obtain the d-axis current reference value; The first determination module is also used to: when the output voltage amplitude is less than or equal to a preset voltage reference value, perform proportional integral control on the difference between the actual reactive power value of the converter and the reactive power reference value to obtain the current reference value of the q-axis.

19. A computer device, characterized in that: include: one or more processors; The processor is used to store one or more programs; When the one or more programs are executed by the one or more processors, the low voltage ride-through control method according to any one of claims 1 to 9 is implemented.

20. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the low voltage ride-through control method as claimed in any one of claims 1 to 9 is implemented.

Images