Method and device for controlling high and low voltage fault ride-through of network construction type converter

Abstract

The invention discloses a high-low voltage fault ride-through control method and device for a network-forming converter, and the method comprises the steps: obtaining the three-phase voltage of a grid-connected point, and carrying out the dq rotation coordinate transformation of the three-phase voltage of the grid-connected point, and obtaining a three-phase voltage component; determining a grid-connected point three-phase voltage effective value according to the three-phase voltage component; according to the grid-connected point three-phase voltage effective value and a preset high-low voltage threshold value, whether a grid-connected point power grid meets a high-low voltage fault ride-through condition or not is determined; wherein the preset high and low voltage threshold values comprise a high voltage threshold value and a low voltage threshold value; if the grid-connected point power grid meets the high-low voltage fault ride-through condition, determining an active power instruction value and a reactive power instruction value through a high-low voltage fault ride-through algorithm; and inputting the active power instruction value and the reactive power instruction value into a VSG control system for high and low voltage control. According to the invention, the reactive voltage supporting capability during the high-low voltage fault ride-through period of the grid-forming converter is improved.

Description

Technical Field

[0001] The present invention relates to the field of renewable energy power generation technology, and in particular to a method and device for controlling high and low voltage fault ride-through of a grid-connected converter. Background Art

[0002] In recent years, renewable energy power generation has developed rapidly. Traditional grid-connected converters usually adopt grid-following control. However, grid-connected converters need to rely on the power grid to provide stable voltage and frequency and cannot independently support the system. Compared with grid-connected converters, grid-building converters have essential advantages. As power electronic devices, grid-building converters need to meet the requirements of high and low voltage crossing of the system voltage during grid-connected operation in order to ensure that the grid-building converter can continue to operate stably when a grid failure occurs, thereby ensuring the stability and reliability of the power system. Therefore, the grid-building converter can output stable voltage and frequency, and can operate both on the grid and off the grid. The grid-building converter has stronger grid support capabilities and reactive current support capabilities.

[0003] However, there is a lack of relevant grid-connected technical standards for high and low voltage fault ride-through of grid-type converters at present, so the current requirements for high and low voltage fault ride-through of grid-type converters are mainly based on the grid-connected technical standards for traditional grid-type devices. However, since grid-type converters usually use complex control strategies to control voltage and current to achieve high and low voltage ride-through, while grid-type converters directly control active power and reactive power to achieve high and low voltage ride-through, there are great differences in the control mechanism between grid-type converters and grid-type devices, so it is necessary to redesign the high and low voltage ride-through control strategy of grid-type converters.

[0004] This section is intended to provide a background or context to the embodiments of the invention recited in the claims. No admission is made that the description herein is prior art by inclusion in this section. Summary of the invention

[0005] An embodiment of the present invention provides a high and low voltage fault ride-through control method for a grid-type converter, which is used to improve the supporting capacity of reactive voltage during high and low voltage fault ride-through of the grid-type converter by establishing a control method for adapting the high and low voltage ride-through requirements of the grid-type converter.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a high and low voltage fault ride-through control method for a grid-connected converter, comprising:

[0008] Obtaining a three-phase voltage at a grid connection point, and performing a dq rotation coordinate transformation on the three-phase voltage at the grid connection point to obtain a three-phase voltage component;

[0009] Determine the effective value of the three-phase voltage at the grid connection point according to the three-phase voltage components;

[0010] Determine whether the grid connection point power grid meets the high and low voltage fault ride-through conditions according to the effective value of the three-phase voltage of the grid connection point and the preset high and low voltage thresholds; wherein the preset high and low voltage thresholds include a high voltage threshold and a low voltage threshold;

[0011] If the grid connection point power grid meets the high and low voltage fault ride-through conditions, the active power command value and the reactive power command value are determined by the high and low voltage fault ride-through algorithm;

[0012] The active power command value and the reactive power command value are input into the VSG control system for high and low voltage control.

[0013] Further, the determining whether the grid connection point power grid meets the high and low voltage fault ride-through conditions according to the effective value of the three-phase voltage at the grid connection point and the preset high and low voltage thresholds includes:

[0014] The effective value of the three-phase voltage at the grid connection point is compared with the high voltage threshold and the low voltage threshold respectively; if the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold or the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the grid connection point power grid meets the conditions for entering the high and low voltage fault ride-through.

[0015] Further, the determining of the active power command value and the reactive power command value by the high and low voltage fault ride-through algorithm includes:

[0016] If the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold, the active power command value and the reactive power command value are determined according to a high voltage fault ride-through algorithm.

[0017] Further, the determining of the active power command value and the reactive power command value by the high and low voltage fault ride-through algorithm includes:

[0018] If the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the active power command value and the reactive power command value are determined according to a low voltage fault ride-through algorithm.

[0019] Further, the determining the active power command value and the reactive power command value according to the high voltage fault ride-through algorithm includes:

[0020] Determine the reactive power command value according to the output steady-state reactive power at a moment before the high voltage fault ride-through, the reactive power coefficient during the high voltage fault ride-through, the positive sequence component of the three-phase voltage at the grid connection point, the high voltage threshold and the reactive current coefficient, and the positive sequence voltage at the grid connection point that meets the maximum lift requirement under the high voltage fault ride-through;

[0021] The active power command value is determined according to the output steady-state active power at a moment before the high voltage fault ride-through.

[0022] Further, determining the active power command value and the reactive power command value according to the low voltage fault ride-through algorithm includes:

[0023] Determine the reactive power command value according to the output steady-state reactive power at the moment before the low voltage fault ride-through, the reactive power coefficient during the low voltage fault ride-through, the positive sequence component of the three-phase voltage at the grid connection point, the low voltage threshold and the reactive current coefficient, and the positive sequence voltage at the grid connection point that meets the maximum drop requirement under the low voltage fault ride-through;

[0024] The active power command value is determined according to the output steady-state active power at the moment before the low voltage fault ride-through.

[0025] Further, the method for determining the reactive power coefficient during the high voltage fault ride-through includes:

[0026] The reactive power coefficient during the high voltage fault ride-through is determined according to the preset reactive power regulation voltage during the high voltage fault ride-through, the high voltage threshold, the grid connection point positive sequence voltage that meets the maximum lift requirement under the high voltage fault ride-through, and the preset reactive current proportional coefficient.

[0027] Further, the method for determining the reactive power coefficient during the low voltage fault ride-through period includes:

[0028] The reactive power coefficient during the low voltage fault ride-through is determined according to the preset reactive power regulation voltage during the low voltage fault ride-through, the low voltage threshold, the grid connection point positive sequence voltage that meets the maximum drop requirement under the low voltage fault ride-through, and the preset reactive current proportional coefficient.

[0029] In a second aspect, an embodiment of the present invention further provides a high and low voltage fault ride-through control device for a grid-type converter, which is used to improve the supporting capacity of reactive voltage during high and low voltage fault ride-through of the grid-type converter, and the device includes:

[0030] A voltage acquisition module is used to obtain the three-phase voltage of the grid connection point, and obtain the three-phase voltage components by dq rotating coordinate transformation of the three-phase voltage of the grid connection point;

[0031] A voltage processing module, used to determine the effective value of the three-phase voltage at the grid connection point according to the three-phase voltage components;

[0032] A ride-through condition judgment module is used to determine whether the grid connection point power grid meets the high and low voltage fault ride-through conditions according to the effective value of the three-phase voltage of the grid connection point and the preset high and low voltage thresholds; wherein the preset high and low voltage thresholds include a high voltage threshold and a low voltage threshold;

[0033] If the grid connection point power grid meets the high and low voltage fault ride-through conditions, a power determination module is used to determine the active power command value and the reactive power command value through a high and low voltage fault ride-through algorithm;

[0034] The voltage control module is used to input the active power command value and the reactive power command value into the VSG control system for high and low voltage control.

[0035] Furthermore, the crossing condition judgment module is specifically used to compare the effective value of the three-phase voltage at the grid connection point with the high voltage threshold and the low voltage threshold respectively; if the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold or the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the grid connection point power grid meets the conditions for entering the high and low voltage fault crossing.

[0036] Further, the power determination module includes a high voltage power determination unit;

[0037] If the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold, the high voltage power determination unit is used to determine the active power command value and the reactive power command value according to a high voltage fault ride-through algorithm.

[0038] Further, the power command value determination module also includes a low voltage power determination unit;

[0039] If the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the low voltage power determination unit is used to determine the active power command value and the reactive power command value according to a low voltage fault ride-through algorithm.

[0040] Furthermore, the high voltage power determination unit includes:

[0041] A high-voltage reactive power determination subunit, used to determine the reactive power command value according to the output steady-state reactive power at a moment before the high-voltage fault ride-through, the reactive power coefficient during the high-voltage fault ride-through, the positive-sequence component of the three-phase voltage at the grid connection point, the high-voltage threshold and the reactive current coefficient, and the positive-sequence voltage at the grid connection point that meets the maximum lift requirement under the high-voltage fault ride-through;

[0042] The high voltage active power determination subunit is used to determine the active power command value according to the output steady-state active power at a moment before the high voltage fault passes through.

[0043] Furthermore, the low voltage power determination unit includes:

[0044] A low voltage reactive power determination subunit, used to determine the reactive power command value according to the output steady-state reactive power at a moment before the low voltage fault ride-through, the reactive power coefficient during the low voltage fault ride-through, the positive sequence component of the three-phase voltage of the grid connection point, the low voltage threshold and the reactive current coefficient, and the positive sequence voltage of the grid connection point that meets the maximum drop requirement under the low voltage fault ride-through;

[0045] The low voltage active power determination subunit is used to determine the active power command value according to the output steady-state active power at the moment before the low voltage fault ride-through.

[0046] Furthermore, the high-voltage reactive power determination subunit includes:

[0047] The high-voltage reactive power coefficient determination subunit is used to determine the reactive power coefficient during the high-voltage fault ride-through period based on the preset reactive power regulation voltage during the high-voltage fault ride-through period, the high-voltage threshold, the positive sequence voltage of the grid connection point that meets the maximum lift requirement during the high-voltage fault ride-through period, and the preset reactive current proportional coefficient.

[0048] Furthermore, the low voltage reactive power determination subunit includes:

[0049] The low-voltage reactive power coefficient determination subunit is used to determine the reactive power coefficient during the low-voltage fault ride-through period based on the preset reactive power regulation voltage during the low-voltage fault ride-through period, the low-voltage threshold, the grid-connected point positive sequence voltage that meets the maximum drop requirement under the low-voltage fault ride-through period, and the preset reactive current proportional coefficient.

[0050] An embodiment of the present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned grid-type converter high and low voltage fault ride-through control method when executing the computer program.

[0051] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the above-mentioned grid-type converter high and low voltage fault ride-through control method is implemented.

[0052] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the above-mentioned high and low voltage fault ride-through control method of the grid-type converter is implemented.

[0053] An embodiment of the present invention provides a high and low voltage fault ride-through control method and device for a grid-connected converter, which obtains the three-phase voltage at the grid-connected point, and obtains the three-phase voltage components through dq rotation coordinate transformation of the three-phase voltage at the grid-connected point; determines the effective value of the three-phase voltage at the grid-connected point according to the three-phase voltage components; determines whether the grid at the grid-connected point meets the conditions for entering high and low voltage fault ride-through according to the effective value of the three-phase voltage at the grid-connected point and preset high and low voltage thresholds; if the grid at the grid-connected point meets the conditions for entering high and low voltage fault ride-through, determines the active power command value and the reactive power command value through a high and low voltage fault ride-through algorithm; inputs the active power command value and the reactive power command value into a VSG control system for high and low voltage control, thereby improving the supporting capacity of the reactive voltage during the high and low voltage fault ride-through of the grid-connected converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0055] Figure 1 It is a flow chart of a high and low voltage fault ride-through control method of a grid-type converter in one embodiment of the present invention;

[0056] Figure 2 A schematic diagram of a high and low voltage fault ride-through control method for a grid-type converter in another embodiment of the present invention;

[0057] Figure 3 It is a flow chart of a high and low voltage fault ride-through control method of a grid-type converter in another embodiment of the present invention;

[0058] Figure 4 It is a flow chart of a high and low voltage fault ride-through control method of a grid-type converter in another embodiment of the present invention;

[0059] Figure 5 It is a flow chart of a high and low voltage fault ride-through control method of a grid-type converter in another embodiment of the present invention;

[0060] Figure 6 It is a structural schematic diagram of a high and low voltage fault ride-through control device of a grid-type converter in one embodiment of the present invention;

[0061] Figure 7 It is a structural schematic diagram of a high and low voltage fault ride-through control device of a grid-type converter in another embodiment of the present invention;

[0062] Figure 8It is a structural schematic diagram of a high and low voltage fault ride-through control device of a grid-type converter in another embodiment of the present invention;

[0063] Fig. 9 It is a structural schematic diagram of a high and low voltage fault ride-through control device of a grid-type converter in another embodiment of the present invention;

[0064] Fig.10 A schematic diagram of the physical structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0065] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0066] The information collected in the technical solution of this application is information and data authorized by the user or fully authorized by all parties, and the collection, storage, use, processing, transmission, provision, disclosure and application of relevant data comply with the relevant laws, regulations and standards of relevant countries and regions, take necessary confidentiality measures, do not violate public order and good morals, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0067] The acquisition, transmission, storage, use, and processing of data in the technical solution of this application comply with the relevant provisions of national laws and regulations.

[0068] It should be noted that in the embodiments of the present application, certain software, components, models and other existing solutions in the industry may be mentioned, and they should be regarded as exemplary. Their purpose is only to illustrate the feasibility of implementing the technical solution of the present application, but it does not mean that the applicant has or will necessarily use the solution.

[0069] In order to improve the stability of a grid-type converter during high and low voltage fault riding, a control strategy that meets the requirements of the grid-type converter for high and low voltage fault riding is established according to the control mechanism of the grid-type converter to achieve the supporting capability of reactive voltage during the high and low voltage fault riding of the grid-type converter. The present invention provides a high and low voltage fault riding control method for a grid-type converter.

[0070] Figure 1 1 is a flow chart of a high and low voltage fault ride-through control method for a grid-type converter according to an embodiment of the present invention. The execution subject of the high and low voltage fault ride-through control method for a grid-type converter is a high and low voltage fault ride-through control device, such as Figure 1 As shown, the high and low voltage fault ride-through control method of the grid-connected converter includes steps 101 to 105.

[0071] Step 101: acquiring the three-phase voltage of the grid connection point, and transforming the three-phase voltage of the grid connection point through dq rotation coordinate transformation to obtain the three-phase voltage components;

[0072] Step 102: determining the effective value of the three-phase voltage at the grid connection point according to the three-phase voltage components;

[0073] Step 103: determining whether the grid at the grid connection point meets the high and low voltage fault ride-through conditions according to the effective value of the three-phase voltage at the grid connection point and the preset high and low voltage thresholds; wherein the preset high and low voltage thresholds include a high voltage threshold and a low voltage threshold;

[0074] Step 104: If the grid at the connection point meets the high and low voltage fault ride-through conditions, an active power command value and a reactive power command value are determined by a high and low voltage fault ride-through algorithm;

[0075] Step 105: Input the active power command value and the reactive power command value into the VSG control system for high and low voltage control.

[0076] from Figure 1 It can be seen from the process shown that in the embodiment of the present invention, the three-phase voltage of the grid connection point is obtained, and the three-phase voltage of the grid connection point is transformed by dq rotation coordinate to obtain the three-phase voltage component; the effective value of the three-phase voltage of the grid connection point is determined according to the three-phase voltage component; according to the effective value of the three-phase voltage of the grid connection point and the preset high and low voltage thresholds, it is determined whether the grid connection point power grid meets the conditions for entering the high and low voltage fault crossing; if the grid connection point power grid meets the conditions for entering the high and low voltage fault crossing, the active power command value and the reactive power command value are determined by the high and low voltage fault crossing algorithm; the active power command value and the reactive power command value are input into the VSG control system for high and low voltage control, thereby improving the supporting capacity of the reactive voltage of the grid-connected converter during the high and low voltage fault crossing.

[0077] like Figure 1 As shown, each step is explained in detail below.

[0078] Step 101: Obtain the three-phase voltage of the grid connection point, and obtain the three-phase voltage components by performing dq rotation coordinate transformation on the three-phase voltage of the grid connection point.

[0079] Specifically, the voltage Hall sensor is used to collect the three-phase voltage V pcc , we get V pcca 、V pccb and V pccc .

[0080] like Figure 2 As shown, the three-phase voltage V at the grid connection point is transformed by dq rotating coordinates. pcca 、V pccb and V pcccPerform dq rotation coordinate transformation to obtain the d-axis component V of the three-phase voltage in the dq coordinate system d , q-axis component V q Among them, the three-phase voltage component is V d and V q And V0; in the dq coordinate system, the d-axis component represents active power, the q-axis component represents reactive power, and V0 is usually 0.

[0081] Specifically, the dq rotation coordinate transformation formula is:

[0082]

[0083] Among them, ωt is the active power loop output phase of the grid-connected converter, V d is the d-axis component of the three-phase voltage in the dq coordinate system, V q is the q-axis component of the three-phase voltage in the dq coordinate system, V pcca is the a-axis component of the three-phase voltage in the abc coordinate system, V pccb is the b-axis component of the three-phase voltage in the abc coordinate system, V pccc It is the c-axis component of the three-phase voltage in the abc coordinate system.

[0084] Step 102: Determine the effective value of the three-phase voltage at the grid connection point according to the three-phase voltage components.

[0085] Specifically, according to the three-phase voltage component V d and V q Calculate the effective value components of the three-phase voltage at the grid connection point

[0086] Step 103: Determine whether the grid at the grid connection point meets the conditions for entering high and low voltage fault ride-through according to the effective value of the three-phase voltage at the grid connection point and the preset high and low voltage thresholds; wherein the preset high and low voltage thresholds include a high voltage threshold and a low voltage threshold.

[0087] Specifically, the three-phase voltage effective value component of the above-mentioned grid connection point As the judgment condition for determining whether the grid connection point power grid enters high and low voltage fault ride-through, the grid connection point power grid meets the high and low voltage fault ride-through conditions according to the effective value of the three-phase voltage at the grid connection point and the preset high and low voltage thresholds. Among them, the preset high and low voltage thresholds include high voltage threshold and low voltage threshold; the high voltage threshold is the per unit value of the threshold increase of the grid-connected converter during the high voltage fault ride-through period, denoted as U setH , generally U setH The value is 1.1; the low voltage threshold is the per unit value of the grid-connected converter drop threshold during the low voltage fault ride-through period, denoted as U setL , generally U setL The value is 0.9.

[0088] In one embodiment, step 103 further includes: comparing the effective value of the three-phase voltage at the grid connection point with the high voltage threshold and the low voltage threshold respectively; if the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold or the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the grid connection point power grid meets the conditions for entering the high and low voltage fault ride-through.

[0089] Specifically, the three-phase voltage effective value component of the grid connection point Respectively with the high voltage threshold U setH And low voltage threshold U setL For comparison. or The grid at the connection point meets the conditions for entering high and low voltage fault ride-through.

[0090] After determining that the grid at the connection point meets the high and low fault ride-through conditions, the active power command value P of the grid at the connection point is adjusted by function switching. ref and reactive power command value Q ref , switch the grid from the steady-state operation state to the high and low voltage fault ride-through state, and calculate the active power command value P according to the high and low voltage fault ride-through algorithm ref and reactive power command value Q ref .

[0091] Step 104: If the grid at the connection point meets the high and low voltage fault ride-through conditions, the active power command value and the reactive power command value are determined by the high and low voltage fault ride-through algorithm.

[0092] like Figure 3 As shown, the active power command value P is determined by the high and low voltage fault ride-through algorithm. ref and reactive power command value Q ref It includes step 301 and step 302.

[0093] Step 301: If the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold, an active power command value and a reactive power command value are determined according to a high voltage fault ride-through algorithm.

[0094] Specifically, if When the active power command value P ref and reactive power command value Q ref Calculated based on the high voltage fault ride-through algorithm.

[0095] According to the high voltage fault ride-through algorithm, the active power command value P is determined. ref and reactive power command value Q ref Before that, the reactive power factor k during high voltage fault ride-through must be determined. Q .

[0096] Reactive power factor k during high voltage fault ride-through QThe calculation methods include:

[0097] The reactive power coefficient during the high voltage fault ride-through is determined according to the preset reactive power regulation voltage during the high voltage fault ride-through, the high voltage threshold, the positive sequence voltage of the grid connection point that meets the maximum lift requirement under the high voltage fault ride-through, and the preset reactive current proportional coefficient.

[0098] Specifically, the reactive power factor k of the grid-type converter during the high voltage fault ride-through of the grid-type converter is Q Satisfies the following relationship:

[0099]

[0100] Among them, U m The reactive power regulation voltage during high voltage fault ride-through of the grid-connected converter, U m Should satisfy U setH <U m ≤U d ≤U p , so during high voltage fault ride-through U m Can be set to a fixed value or set to change with U d The value of the change.

[0101] In one embodiment, according to the technical standards for grid connection of existing grid-following equipment, the reactive current proportional coefficient k of the grid-following converter during high voltage fault ride-through is i The value range should be k i ≥5.5, this application is not limited to this.

[0102] like Figure 4 As shown, the active power command value P is determined according to the high voltage fault ride-through algorithm. ref and reactive power command value Q ref It includes step 401 and step 402.

[0103] Step 401: Determine the reactive power command value according to the output steady-state reactive power at a moment before the high voltage fault ride-through, the reactive power coefficient during the high voltage fault ride-through, the positive sequence component of the three-phase voltage at the grid connection point, the high voltage threshold and the reactive current coefficient, and the positive sequence voltage at the grid connection point that meets the maximum lift requirement under the high voltage fault ride-through.

[0104] Specifically, the reactive power command value Q is calculated according to the expression of the reactive power command value during high voltage fault ride-through: ref , the expression of reactive power command value of grid-connected converter during high voltage fault ride-through is:

[0105]

[0106] Where Q0 is the per-unit value of the steady-state reactive power component output by the grid-connected converter just before the high voltage fault ride-through, k Q is the reactive power factor of the grid-connected converter during high voltage fault ride-through, U d is the per-unit value of the positive sequence component of the three-phase voltage at the grid-connected point of the grid-connected converter during high voltage fault ride-through, U setH is the per-unit value of the grid-connected converter's threshold rise during high voltage fault ride-through, generally U setH The value is 1.1; U p In order to construct the positive sequence voltage per unit value of the grid connection point that meets the highest lifting requirement under the high voltage fault ride-through of the grid-type converter, according to the existing grid-type converter standard U p The value is 1.3; I qmax is the reactive current coefficient during high voltage fault ride-through. According to the current requirement of 3 times overcurrent capacity of grid-type equipment, I qmax The value should satisfy 0≤I qmax ≤3.

[0107] Step 402: Determine an active power command value according to the output steady-state active power at a moment before the high voltage fault ride-through.

[0108] Specifically, the active power command value P is calculated according to the expression of the active power command value during high voltage fault ride-through: ref , the expression of the active power command value of the grid-connected converter during high voltage fault ride-through is: ref =P0.

[0109] Wherein, P0 is the per unit value of the steady-state active power component output by the grid-connected converter at the moment before the high voltage fault ride-through.

[0110] Step 302: If the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the active power command value and the reactive power command value are determined according to the low voltage fault ride-through algorithm.

[0111] Specifically, if When the active power command value P ref and reactive power command value Q ref Calculated based on the low voltage fault ride-through algorithm.

[0112] According to the low voltage fault ride-through algorithm, the active power command value P is determined. ref and reactive power command value Q ref Before that, it is necessary to determine the reactive power factor k during low voltage fault ride-through. Q .

[0113] Reactive power factor k during low voltage fault ride-through Q The calculation methods include:

[0114] The reactive power coefficient during the low voltage fault ride-through is determined according to the preset reactive power regulation voltage during the low voltage fault ride-through, the low voltage threshold, the grid connection point positive sequence voltage that meets the maximum drop requirement under the low voltage fault ride-through, and the preset reactive current proportional coefficient.

[0115] Specifically, the reactive power factor k of the grid-type converter during the low voltage fault ride-through of the grid-type converter is Q Satisfies the following relationship:

[0116]

[0117] Among them, U m The reactive power regulation voltage during low voltage fault ride-through of the grid-connected converter, U m Should satisfy U setL >U m ≥U d >U L , so during the low voltage fault ride-through period U m Can be set to a fixed value or set to change with U d The value of the change.

[0118] In one embodiment, according to the technical standards for grid connection of existing grid-following equipment, the reactive current proportional coefficient k of the grid-following converter during low voltage fault ride-through is i The value range should be k i ≥1.5, this application is not limited to this.

[0119] like Figure 5 As shown, the active power command value P is determined according to the low voltage fault ride-through algorithm. ref and reactive power command value Q ref It includes step 501 and step 502.

[0120] Step 501: Determine the reactive power command value according to the output steady-state reactive power at a moment before the low voltage fault ride-through, the reactive power coefficient during the low voltage fault ride-through, the positive sequence component of the three-phase voltage of the grid connection point, the low voltage threshold and the reactive current coefficient, and the positive sequence voltage of the grid connection point that meets the maximum drop requirement under the low voltage fault ride-through.

[0121] Specifically, the reactive power command value Q is calculated according to the expression of the reactive power command value during the low voltage fault ride-through period: ref , the expression of reactive power command value of grid-connected converter during low voltage fault ride-through is:

[0122]

[0123] Where Q0 is the per unit value of the steady-state reactive power component output by the grid-connected converter just before the low voltage fault ride-through, k Qis the reactive power factor of the grid-connected converter during low voltage fault ride-through, U d is the per-unit value of the positive sequence component of the three-phase voltage at the grid-connected point of the grid-connected converter during low voltage fault ride-through, U setL is the per unit value of the grid-connected converter drop threshold during low voltage fault ride-through, generally U setL The value is 0.9; U L In order to construct the positive sequence voltage per unit value of the grid connection point that meets the maximum drop requirement under the low voltage fault ride-through of the grid-type converter, according to the existing grid-type standard U L The value is 0.2; I qmax is the reactive current coefficient during low voltage fault ride-through. According to the current requirement of 3 times overcurrent capacity of grid-type equipment, I qmax The value should satisfy 0≤I qmax ≤3.

[0124] Step 502: Determine the active power command value according to the output steady-state active power before the low voltage fault ride-through.

[0125] Specifically, the active power command value P is calculated according to the expression of the active power command value during the low voltage fault ride-through period: ref , the expression of the active power command value of the grid-connected converter during low voltage fault ride-through is: ref =P0.

[0126] Wherein, P0 is the per unit value of the steady-state active power component output by the grid-connected converter at the moment before the low voltage fault ride-through.

[0127] The active power command value P of the grid-connected converter is calculated by the high and low voltage fault ride-through algorithm. ref and reactive power command value Q ref After that, according to the actual measured three-phase voltage V pcc and three-phase current I pcc The instantaneous value of is calculated by the power algorithm to obtain the active component P and reactive component Q of the grid at the actual grid-connected point of the grid-connected converter.

[0128] In one embodiment, the power algorithm may be a power calculation method based on a rotating coordinate system, or may be other power algorithms, which is not specifically limited in this embodiment.

[0129] Step 105: Input the active power command value and the reactive power command value into the VSG control system for high and low voltage control.

[0130] Specifically, the active power command value P of the grid-connected converter is ref and reactive power command value Q refThe active power component P and reactive power component Q of the actual grid connection point are input into the VSG control system, and the active power loop control and reactive power loop control of the VSG control system are used to make the active power component P and reactive power component Q reach the active power command value P respectively. ref and reactive power command value Q ref This target value is used to achieve high and low voltage fault ride-through control of the grid-connected converter.

[0131] In an embodiment of the present invention, based on the reactive power and active power at the previous moment during the high voltage ride-through period of the grid-type converter and the correlation coefficient between the voltage and the current, expressions for the active power command value and the reactive power command value during the high voltage ride-through period and the low voltage ride-through period of the grid-type converter are proposed, as well as a relationship and calculation method for the reactive power coefficient that characterizes the reactive support capability of the grid-type converter during the high and low voltage ride-through control period. The active power command value and reactive power command value are determined by using the expressions of the active power command value and reactive power command value during the high voltage ride-through period and the low voltage ride-through period, and then the active component and reactive component of the actual grid-connected point power grid are calculated by the power algorithm, and the above active power command value, reactive power command value, active component and reactive component are input into the VSG control system. The active power loop control and reactive power loop control of the VSG control system are used to make the active component and reactive component reach the active power command value and reactive power command value respectively, thereby realizing the high and low voltage fault ride-through control of the grid-forming converter, and improving the supporting capacity of the reactive voltage during the high and low voltage fault ride-through of the grid-forming converter.

[0132] The embodiment of the present invention also provides a high and low voltage fault ride-through control device for a grid-type converter, as described in the following embodiments. Since the principle of solving the problem by the device is similar to the high and low voltage fault ride-through control method for a grid-type converter, the implementation of the device can refer to the implementation of the high and low voltage fault ride-through control method for a grid-type converter, and the repeated parts will not be repeated.

[0133] Figure 6 Schematic diagram of the structure of the high and low voltage fault ride-through control device of the grid-type converter in the embodiment of the present invention. Figure 6 As shown, the high and low voltage fault ride-through control device 600 of a grid-type converter includes: a voltage acquisition module 601 , a voltage processing module 602 , a ride-through condition judgment module 603 , a power determination module 604 and a voltage control module 605 .

[0134] The voltage acquisition module 601 is used to obtain the three-phase voltage of the grid connection point, and obtain the three-phase voltage components by dq rotating coordinate transformation of the three-phase voltage of the grid connection point.

[0135] The voltage processing module 602 is used to determine the effective value of the three-phase voltage at the grid connection point according to the three-phase voltage components.

[0136] The crossing condition judgment module 603 is used to determine whether the grid connection point power grid meets the high and low voltage fault crossing conditions according to the effective value of the three-phase voltage of the grid connection point and the preset high and low voltage thresholds; wherein the preset high and low voltage thresholds include a high voltage threshold and a low voltage threshold.

[0137] If the grid at the connection point meets the conditions for entering high and low voltage fault ride-through, the power determination module 604 is used to determine the active power command value and the reactive power command value through the high and low voltage fault ride-through algorithm.

[0138] The voltage control module 605 is used to input the active power command value and the reactive power command value into the VSG control system to perform high and low voltage control.

[0139] In one embodiment, the crossing condition judgment module 603 is specifically used to compare the effective value of the three-phase voltage at the grid connection point with the high voltage threshold and the low voltage threshold respectively; if the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold or the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the grid connection point power grid meets the conditions for entering the high and low voltage fault crossing.

[0140] In one embodiment, if Figure 7 As shown, the power determination module 604 includes a high voltage power determination unit 701 .

[0141] If the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold, the high voltage power determination unit 701 is used to determine the active power command value and the reactive power command value according to the high voltage fault ride-through algorithm.

[0142] In one embodiment, if Figure 7 As shown, the power command value determination module 604 further includes a low voltage power determination unit 702 .

[0143] If the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the low voltage power determination unit 702 is used to determine the active power command value and the reactive power command value according to the low voltage fault ride-through algorithm.

[0144] In one embodiment, if Figure 8 As shown, the high voltage power determination unit 701 includes: a high voltage reactive power determination subunit 801 and a high voltage active power determination subunit 802 .

[0145] The high-voltage reactive power determination subunit 801 is used to determine the reactive power command value based on the output steady-state reactive power at the moment before the high-voltage fault ride-through, the reactive power coefficient during the high-voltage fault ride-through, the positive-sequence component of the three-phase voltage of the grid connection point, the high-voltage threshold and the reactive current coefficient, and the positive-sequence voltage of the grid connection point that meets the maximum lift requirement under the high-voltage fault ride-through.

[0146] The high voltage active power determination subunit 802 is used to determine the active power command value according to the output steady-state active power at a moment before the high voltage fault ride-through.

[0147] In one embodiment, if Fig. 9 As shown, the low voltage power determination unit 702 includes: a low voltage reactive power determination subunit 901 and a low voltage active power determination subunit 902 .

[0148] The low-voltage reactive power determination subunit 901 is used to determine the reactive power command value based on the output steady-state reactive power at the moment before the low-voltage fault ride-through, the reactive power coefficient during the low-voltage fault ride-through, the positive-sequence component of the three-phase voltage of the grid-connected point, the low-voltage threshold and the reactive current coefficient, and the positive-sequence voltage of the grid-connected point that meets the maximum drop requirement under the low-voltage fault ride-through.

[0149] The low voltage active power determination subunit 902 is used to determine the active power command value according to the output steady-state active power at the moment before the low voltage fault ride-through.

[0150] In one embodiment, the high-voltage reactive power determination subunit 801 includes a high-voltage reactive power coefficient determination subunit.

[0151] The high-voltage reactive power coefficient determination subunit is used to determine the reactive power coefficient during the high-voltage fault ride-through period based on the preset reactive power regulation voltage during the high-voltage fault ride-through period, the high-voltage threshold, the positive sequence voltage of the grid connection point that meets the maximum lift requirement during the high-voltage fault ride-through period, and the preset reactive current proportional coefficient.

[0152] In one embodiment, the low-voltage reactive power determination subunit 901 includes a low-voltage reactive power coefficient determination subunit.

[0153] The low-voltage reactive power coefficient determination subunit is used to determine the reactive power coefficient during the low-voltage fault ride-through period based on the preset reactive power regulation voltage during the low-voltage fault ride-through period, the low-voltage threshold, the grid-connected point positive sequence voltage that meets the maximum drop requirement under the low-voltage fault ride-through period, and the preset reactive current proportional coefficient.

[0154] Fig.10 A schematic diagram of the physical structure of an electronic device 1000 provided in an embodiment of the present invention is shown in FIG. Fig.10 As shown, the electronic device 1000 includes a processor 1001 , a memory 1002 and a bus 1003 .

[0155] The processor 1001 and the memory 1002 communicate with each other via the bus 1003 .

[0156] The processor 1001 is used to call the program instructions in the memory 1002 to execute the methods provided by the above-mentioned method embodiments.

[0157] An embodiment of the present invention further provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the above-mentioned high and low voltage fault ride-through control method of the grid-type converter is implemented.

[0158] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the above-mentioned high and low voltage fault ride-through control method of the grid-type converter is implemented.

[0159] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention 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.

[0160] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. 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 produce 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.

[0161] 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.

[0162] 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 1The steps for the functions specified in one or more boxes.

[0163] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for controlling high and low voltage fault ride-through of a grid-connected converter, characterized in that: include: Obtaining a three-phase voltage at a grid connection point, and performing a dq rotation coordinate transformation on the three-phase voltage at the grid connection point to obtain a three-phase voltage component; Determine the effective value of the three-phase voltage at the grid connection point according to the three-phase voltage components; Determine whether the grid connection point power grid meets the high and low voltage fault ride-through conditions according to the effective value of the three-phase voltage of the grid connection point and the preset high and low voltage thresholds; wherein the preset high and low voltage thresholds include a high voltage threshold and a low voltage threshold; If the grid connection point power grid meets the high and low voltage fault ride-through conditions, the active power command value and the reactive power command value are determined by the high and low voltage fault ride-through algorithm; The active power command value and the reactive power command value are input into the VSG control system for high and low voltage control.

2. The method according to claim 1, characterized in that The determining whether the grid connection point power grid meets the high and low voltage fault ride-through conditions according to the effective value of the three-phase voltage of the grid connection point and the preset high and low voltage thresholds includes: The effective value of the three-phase voltage at the grid connection point is compared with the high voltage threshold and the low voltage threshold respectively; if the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold or the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the grid connection point power grid meets the conditions for entering the high and low voltage fault ride-through.

3. The method according to claim 1, characterized in that The determining of the active power command value and the reactive power command value by using the high and low voltage fault ride-through algorithm includes: If the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold, the active power command value and the reactive power command value are determined according to a high voltage fault ride-through algorithm.

4. The method according to claim 1, characterized in that: The determining of the active power command value and the reactive power command value by using the high and low voltage fault ride-through algorithm includes: If the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the active power command value and the reactive power command value are determined according to a low voltage fault ride-through algorithm.

5. The method according to claim 3, characterized in that: Determining the active power command value and the reactive power command value according to the high voltage fault ride-through algorithm includes: Determine the reactive power command value according to the output steady-state reactive power at a moment before the high voltage fault ride-through, the reactive power coefficient during the high voltage fault ride-through, the positive sequence component of the three-phase voltage at the grid connection point, the high voltage threshold and the reactive current coefficient, and the positive sequence voltage at the grid connection point that meets the maximum lift requirement under the high voltage fault ride-through; The active power command value is determined according to the output steady-state active power at a moment before the high voltage fault ride-through.

6. The method according to claim 4, characterized in that Determining the active power command value and the reactive power command value according to the low voltage fault ride-through algorithm includes: Determine the reactive power command value according to the output steady-state reactive power at the moment before the low voltage fault ride-through, the reactive power coefficient during the low voltage fault ride-through, the positive sequence component of the three-phase voltage at the grid connection point, the low voltage threshold and the reactive current coefficient, and the positive sequence voltage at the grid connection point that meets the maximum drop requirement under the low voltage fault ride-through; The active power command value is determined according to the output steady-state active power at the moment before the low voltage fault ride-through.

7. The method according to claim 5, characterized in that The method for determining the reactive power coefficient during the high voltage fault ride-through period includes: The reactive power coefficient during the high voltage fault ride-through is determined according to the preset reactive power regulation voltage during the high voltage fault ride-through, the high voltage threshold, the grid connection point positive sequence voltage that meets the maximum lift requirement under the high voltage fault ride-through, and the preset reactive current proportional coefficient.

8. The method according to claim 6, characterized in that The method for determining the reactive power coefficient during the low voltage fault ride-through period includes: The reactive power coefficient during the low voltage fault ride-through is determined according to the preset reactive power regulation voltage during the low voltage fault ride-through, the low voltage threshold, the grid connection point positive sequence voltage that meets the maximum drop requirement under the low voltage fault ride-through, and the preset reactive current proportional coefficient.

9. A high and low voltage fault ride-through control device for a grid-type converter, characterized in that: include: A voltage acquisition module is used to obtain the three-phase voltage of the grid connection point, and obtain the three-phase voltage components by dq rotating coordinate transformation of the three-phase voltage of the grid connection point; A voltage processing module, used to determine the effective value of the three-phase voltage at the grid connection point according to the three-phase voltage components; A ride-through condition judgment module is used to determine whether the grid connection point power grid meets the high and low voltage fault ride-through conditions according to the effective value of the three-phase voltage of the grid connection point and the preset high and low voltage thresholds; wherein the preset high and low voltage thresholds include a high voltage threshold and a low voltage threshold; If the grid connection point power grid meets the high and low voltage fault ride-through conditions, a power determination module is used to determine the active power command value and the reactive power command value through a high and low voltage fault ride-through algorithm; The voltage control module is used to input the active power command value and the reactive power command value into the VSG control system for high and low voltage control.

10. The device according to claim 9, characterized in that The crossing condition judgment module is specifically used to compare the effective value of the three-phase voltage at the grid connection point with the high voltage threshold and the low voltage threshold respectively; if the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold or the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the grid connection point power grid meets the high and low voltage fault crossing conditions.

11. The device according to claim 9, characterized in that The power determination module includes a high voltage power determination unit; If the effective value of the three-phase voltage at the grid connection point is greater than the high voltage threshold, the high voltage power determination unit is used to determine the active power command value and the reactive power command value according to a high voltage fault ride-through algorithm.

12. The device according to claim 9, characterized in that The power command value determination module also includes a low voltage power determination unit; If the effective value of the three-phase voltage at the grid connection point is less than the low voltage threshold, the low voltage power determination unit is used to determine the active power command value and the reactive power command value according to a low voltage fault ride-through algorithm.

13. The device according to claim 11, characterized in that The high voltage power determination unit comprises: A high-voltage reactive power determination subunit, used to determine the reactive power command value according to the output steady-state reactive power at a moment before the high-voltage fault ride-through, the reactive power coefficient during the high-voltage fault ride-through, the positive-sequence component of the three-phase voltage at the grid connection point, the high-voltage threshold and the reactive current coefficient, and the positive-sequence voltage at the grid connection point that meets the maximum lift requirement under the high-voltage fault ride-through; The high voltage active power determination subunit is used to determine the active power command value according to the output steady-state active power at a moment before the high voltage fault passes through.

14. The device according to claim 12, characterized in that The low voltage power determination unit comprises: A low voltage reactive power determination subunit, used to determine the reactive power command value according to the output steady-state reactive power at a moment before the low voltage fault ride-through, the reactive power coefficient during the low voltage fault ride-through, the positive sequence component of the three-phase voltage of the grid connection point, the low voltage threshold and the reactive current coefficient, and the positive sequence voltage of the grid connection point that meets the maximum drop requirement under the low voltage fault ride-through; The low voltage active power determination subunit is used to determine the active power command value according to the output steady-state active power at the moment before the low voltage fault ride-through.

15. The device according to claim 13, characterized in that The high-voltage reactive power determination subunit comprises: The high-voltage reactive power coefficient determination subunit is used to determine the reactive power coefficient during the high-voltage fault ride-through period based on the preset reactive power regulation voltage during the high-voltage fault ride-through period, the high-voltage threshold, the positive sequence voltage of the grid connection point that meets the maximum lift requirement during the high-voltage fault ride-through period, and the preset reactive current proportional coefficient.

16. The device according to claim 14, characterized in that The low voltage reactive power determination subunit comprises: The low-voltage reactive power coefficient determination subunit is used to determine the reactive power coefficient during the low-voltage fault ride-through period based on the preset reactive power regulation voltage during the low-voltage fault ride-through period, the low-voltage threshold, the grid-connected point positive sequence voltage that meets the maximum drop requirement under the low-voltage fault ride-through period, and the preset reactive current proportional coefficient.

17. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 8 is implemented.

18. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

19. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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