Network construction control method, network construction control device and medium

Abstract

The embodiment of the invention discloses a network construction control method, a network construction control device and a medium, and is applied to the technical field of electrical control. In the embodiment of the invention, whether the far-end voltage of the virtual synchronous generator has unbalanced drop or not is determined; when the unbalanced drop of the far-end voltage of the virtual synchronous generator does not occur, acquiring the output voltage of the virtual synchronous generator; when the unbalanced drop of the far-end voltage of the virtual synchronous generator occurs, obtaining a negative sequence current value output by the virtual synchronous generator; based on the negative-sequence current value output by the virtual synchronous generator and a preset negative-sequence current reference value, adjusting the output voltage of the virtual synchronous generator so as to adjust the negative-sequence current value output by the virtual synchronous generator until the negative-sequence current value output by the virtual synchronous generator reaches the negative-sequence current reference value; the negative-sequence current output by the virtual synchronous generator can be controlled when unbalanced drop of the far-end voltage of the virtual synchronous generator occurs, and the stability of a power system is ensured.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of electrical control, in particular to a network construction control method, a network construction control device and a medium. BACKGROUND

[0002] With the increasing requirement of power grid on the stability of power system, the grid-connected control technology of voltage source device with inertia and damping characteristics is widely studied, and the commonly used control technology of voltage source device is virtual synchronous generator (VSG) control technology. The virtual synchronous generator control technology controls the output voltage of the virtual synchronous generator to adapt to and support the change of the remote voltage of the virtual synchronous generator (i.e. the voltage of the power grid far away from the side of the access point of the virtual synchronous generator), so as to ensure the stable operation of the power system.

[0003] However, when the power grid side fails (such as single-phase grounding fault, two-phase short circuit fault), the remote voltage of the virtual synchronous generator will appear unbalanced drop, at this time, the asymmetric voltage will generate negative sequence current in the circuit of the virtual synchronous generator, which affects the stability of the power system. SUMMARY

[0004] The embodiment of the present application provides a network construction control method, a network construction control device and a medium, which can control the negative sequence current output by the virtual synchronous generator when the remote voltage of the virtual synchronous generator appears unbalanced drop, and ensure the stability of the power system.

[0005] The embodiment of the present application provides a network construction control method, comprising:

[0006] determining whether the remote voltage of the virtual synchronous generator appears unbalanced drop;

[0007] when the remote voltage of the virtual synchronous generator does not appear unbalanced drop, acquiring the output voltage of the virtual synchronous generator;

[0008] when the remote voltage of the virtual synchronous generator appears unbalanced drop, acquiring the negative sequence current value output by the virtual synchronous generator; based on the negative sequence current value output by the virtual synchronous generator and a preset negative sequence current reference value, adjusting the output voltage of the virtual synchronous generator to adjust the negative sequence current value output by the virtual synchronous generator, until the negative sequence current value output by the virtual synchronous generator reaches the negative sequence current reference value.

[0009] Further, the determination of whether the remote voltage of the virtual synchronous generator appears unbalanced drop comprises:

[0010] acquiring the three-phase voltage signal corresponding to the remote voltage of the virtual synchronous generator;

[0011] If the voltage value of any one of the three-phase voltage signals is lower than a preset voltage threshold, it is determined that an unbalanced drop occurs in the remote voltage of the virtual synchronous generator;

[0012] If the voltage value of the three-phase voltage signals is greater than or equal to the preset voltage threshold, it is determined that an unbalanced drop does not occur in the remote voltage of the virtual synchronous generator.

[0013] Further, the output voltage of the virtual synchronous generator includes:

[0014] The phase angle of the active power ring output of the virtual synchronous generator and the field voltage of the reactive power ring output of the virtual synchronous generator are obtained.

[0015] Based on the phase angle and the field voltage, the grid-connected point reference voltage of the inverter of the virtual synchronous generator is determined, and the grid-connected point reference voltage of the inverter is taken as the output voltage of the virtual synchronous generator.

[0016] Further, the negative sequence current value output by the virtual synchronous generator includes a direct-axis negative sequence current value and a cross-axis negative sequence current value.

[0017] The negative sequence current value output by the virtual synchronous generator includes:

[0018] The three-phase current signal output by the virtual synchronous generator is obtained.

[0019] The three-phase current signal is converted into a current signal in a rotating coordinate system, and based on the current signal in the rotating coordinate system, the direct-axis negative sequence current value and the cross-axis negative sequence current value output by the virtual synchronous generator are obtained.

[0020] Further, the negative sequence current value output by the virtual synchronous generator includes a direct-axis negative sequence current value and a cross-axis negative sequence current value; and the negative sequence current reference value includes a direct-axis negative sequence current reference value and a cross-axis negative sequence current reference value.

[0021] The output voltage of the virtual synchronous generator is adjusted based on the negative sequence current value output by the virtual synchronous generator and the preset negative sequence current reference value, including:

[0022] Based on the direct-axis negative sequence current value and the direct-axis negative sequence current reference value, and the cross-axis negative sequence current value and the cross-axis negative sequence current reference value, a negative sequence voltage component in a three-phase rotating coordinate system is determined.

[0023] Superimpose the negative sequence voltage component in the three-phase rotating coordinate system to grid point reference voltage of an inverter of the virtual synchronous generator to adjust the output voltage of the virtual synchronous generator.

[0024] Further, the negative sequence voltage component in the three-phase rotating coordinate system is determined based on the direct-axis negative sequence current value and the direct-axis negative sequence current reference value, and the quadrature-axis negative sequence current value and the quadrature-axis negative sequence current reference value, including:

[0025] The direct-axis negative sequence current value and the direct-axis negative sequence current reference value are input into a PI regulator to obtain a direct-axis negative sequence voltage value output by the PI regulator;

[0026] The quadrature-axis negative sequence current value and the quadrature-axis negative sequence current reference value are input into a PI regulator to obtain a quadrature-axis negative sequence voltage value output by the PI regulator;

[0027] The direct-axis negative sequence voltage value and the quadrature-axis negative sequence voltage value are converted into the negative sequence voltage component in the three-phase rotating coordinate system.

[0028] Further, the direct-axis negative sequence voltage value and the quadrature-axis negative sequence voltage value are converted into the negative sequence voltage component in the three-phase rotating coordinate system, including:

[0029] The direct-axis negative sequence voltage value and the quadrature-axis negative sequence voltage value are converted into the negative sequence voltage component in the two-phase stationary coordinate system through inverse Park transformation;

[0030] The negative sequence voltage component in the two-phase stationary coordinate system is converted into the negative sequence voltage component in the three-phase rotating coordinate system through inverse Clark transformation.

[0031] The application embodiment further provides a network construction control device, including:

[0032] A determination unit is configured to determine whether remote voltage of a virtual synchronous generator appears unbalanced drop;

[0033] An acquisition unit is configured to acquire output voltage of the virtual synchronous generator when the determination unit determines that the remote voltage of the virtual synchronous generator does not appear unbalanced drop;

[0034] An execution unit is configured to acquire negative sequence current value output by the virtual synchronous generator when the determination unit determines that the remote voltage of the virtual synchronous generator appears unbalanced drop; and adjust the output voltage of the virtual synchronous generator based on the negative sequence current value output by the virtual synchronous generator and a preset negative sequence current reference value, to adjust the negative sequence current value output by the virtual synchronous generator until the negative sequence current value output by the virtual synchronous generator reaches the negative sequence current reference value.

[0035] The embodiment of the present application also provides a voltage source type device, and a control method of the voltage source device includes the network construction control method.

[0036] The embodiment of the present application also provides a computer readable storage medium, which includes instructions, when the instructions are executed on a computer, the computer executes the method as described above.

[0037] From the above technical solutions, the embodiment of the present application has the following advantages:

[0038] In the embodiment of the present application, it is determined whether the remote voltage of the virtual synchronous generator appears unbalanced drop, when the remote voltage of the virtual synchronous generator does not appear unbalanced drop, the output voltage of the virtual synchronous generator is obtained, when the remote voltage of the virtual synchronous generator appears unbalanced drop, the negative sequence current value output by the virtual synchronous generator is obtained, based on the negative sequence current value output by the virtual synchronous generator and the preset negative sequence current reference value, the output voltage of the virtual synchronous generator is adjusted to adjust the negative sequence current value output by the virtual synchronous generator, until the negative sequence current value output by the virtual synchronous generator reaches the negative sequence current reference value. When the remote voltage of the virtual synchronous generator appears unbalanced drop, the output voltage of the virtual synchronous generator is adjusted based on the negative sequence current value output by the virtual synchronous generator and the preset negative sequence current reference value, the negative sequence current value output by the virtual synchronous generator can be controlled to the negative sequence current reference value, that is, the negative sequence current output by the virtual synchronous generator can be controlled when the remote voltage of the virtual synchronous generator appears unbalanced drop, and the stability of the power system is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art according to these drawings.

[0040] Figure 1 A network construction control flowchart disclosed by the embodiment of the present application;

[0041] Figure 2 A negative sequence current control flowchart disclosed by the embodiment of the present application;

[0042] Figure 3 A structure schematic diagram of a virtual synchronous generator disclosed by the embodiment of the present application;

[0043] Figure 4 A structure schematic diagram of a virtual synchronous generator with added negative sequence control disclosed by the embodiment of the present application;

[0044] Figure 5 A remote voltage and a remote current waveform diagram disclosed by an embodiment of the present application;

[0045] Figure 6 A partial enlarged waveform diagram disclosed by an embodiment of the present application;

[0046] Figure 7 A waveform diagram of a plurality of negative sequence parameters output by a virtual synchronous generator disclosed by an embodiment of the present application;

[0047] Figure 8 A schematic diagram of a network construction control device disclosed by an embodiment of the present application;

[0048] Figure 9 A schematic diagram of another network construction control device disclosed by an embodiment of the present application. DETAILED DESCRIPTION

[0049] In order to enable persons skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by persons skilled in the art without creative work fall within the scope of protection of the present application.

[0050] In the description of the embodiments of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0051] In the description of the embodiments of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0052] The existing voltage source type device commonly uses virtual synchronous generator (VSG) control technology. The VSG control technology is a network construction control technology. The VSG does not need to rely on the reference signal of the power grid, but controls the output voltage of the VSG to adapt to and support the change of the remote voltage (the power grid voltage far away from the VSG access point) of the VSG, and guarantees the stable operation of the power system. However, when the power grid side fails (such as single-phase grounding fault, two-phase short circuit fault), the asymmetric switching of large loads, etc., the remote voltage of the VSG will appear unbalanced drop, that is, the amplitudes of the three-phase voltages are not equal, the phase difference is no longer maintained at 120°, and the overall power grid voltage amplitude is reduced. The asymmetric voltage will generate negative sequence current in the circuit of the VSG, which affects the stability of the power system (such as equipment heating, torque pulsation, etc.). Therefore, the embodiment of the present application provides a network construction control method, which can control the negative sequence current output by the VSG when the remote voltage of the VSG appears unbalanced drop, and ensure the stability of the power system. As shown in Figure 1 The specific steps are as follows:

[0053] 101, determine whether the remote voltage of the VSG appears unbalanced drop; if not, execute step 102; if yes, execute step 103.

[0054] In the embodiment of the present application, the network construction control device can determine whether the remote voltage of the VSG appears unbalanced drop. The network construction control device can obtain the three-phase voltage signal corresponding to the remote voltage of the VSG. Specifically, the network construction control device can detect the three-phase voltage signal corresponding to the remote voltage at the access point of the VSG through a voltage sensor (such as an electromagnetic voltage transformer or a Hall effect sensor); and determine whether the remote voltage appears unbalanced drop based on the three-phase voltage signal corresponding to the remote voltage.

[0055] Wherein, whether the remote voltage appears unbalanced drop can be determined by a preset voltage threshold. Specifically, if the voltage value of any phase voltage in the three-phase voltage signal corresponding to the remote voltage is lower than the preset voltage threshold, it is determined that the remote voltage of the virtual synchronous generator appears unbalanced drop; if the voltage values of the three-phase voltages in the three-phase voltage signal corresponding to the remote voltage are all greater than or equal to the preset voltage threshold, it is determined that the remote voltage of the virtual synchronous generator does not appear unbalanced drop; the preset voltage threshold can be 90% of the rated value of the remote voltage or 80% of the rated value, which is not limited here. Whether the remote voltage appears unbalanced drop can also be determined by the unbalance degree. Specifically, the three-phase voltage signal corresponding to the remote voltage can be decomposed into positive sequence voltage, negative sequence voltage and zero sequence voltage, and the unbalance degree can be obtained by the ratio of the negative sequence voltage to the positive sequence voltage. When the unbalance degree is greater than a preset threshold (such as 2% or 3%), the remote voltage appears unbalanced drop; when the unbalance degree is less than or equal to the preset threshold, the remote voltage does not appear unbalanced drop.

[0056] 102, obtaining the output voltage of the virtual synchronous generator.

[0057] In the embodiments of the present application, when the remote voltage of the virtual synchronous generator does not appear unbalanced drop, the grid connection control device can obtain the output voltage of the virtual synchronous generator. Specifically, the frequency of the virtual synchronous generator is adjusted and controlled by the active power loop, and the voltage is adjusted and controlled by the reactive power loop. The phase angle output by the active power loop of the virtual synchronous generator and the field voltage output by the reactive power loop of the virtual synchronous generator can be obtained. Based on the phase angle and the field voltage, the grid connection point reference voltage of the inverter of the virtual synchronous generator is determined. The grid connection point reference voltage of the inverter is used for closed-loop control, so that the actual grid connection point voltage of the inverter (i.e. the output voltage of the virtual synchronous generator) tends to or equals to the grid connection point reference voltage of the inverter. The grid connection point reference voltage of the inverter can be used as the output voltage of the virtual synchronous generator, so as to control the frequency and voltage of the power grid by the output voltage of the virtual synchronous generator.

[0058] The structure of the virtual synchronous generator is shown in Figure 3 The control equation of the corresponding power loop is:

[0059]

[0060]

[0061] Wherein, and are the active power command (i.e. given active power) and the actual active power output by the virtual synchronous generator. and respectively are the reactive power command (i.e. given reactive power) and the actual reactive power output by the virtual synchronous generator; 、 、 and respectively are the voltage frequency value and the voltage frequency rating value output by the virtual synchronous generator, the grid output voltage amplitude and the grid rated voltage amplitude; 、J、 、 respectively are the frequency damping coefficient of the virtual synchronous generator, the virtual inertia coefficient of the virtual synchronous generator, the voltage droop coefficient of the virtual synchronous generator and the reactive inertia coefficient of the virtual synchronous generator; is the phase angle output by the active power loop; E is the field voltage output by the reactive power loop of the virtual synchronous generator, and E0 is the no-load electromotive force.

[0062] The phase angle output by the active power loop and the field voltage E output by the reactive power loop can obtain the grid point reference voltage of the inverter; the corresponding grid point reference voltage of the inverter is:

[0063] , ,

[0064] .

[0065] 103. Obtain the negative sequence current value output by the virtual synchronous generator.

[0066] In the embodiment of the application, when the remote voltage of the virtual synchronous generator appears unbalanced drop, the grid forming control device can obtain the negative sequence current value output by the virtual synchronous generator. Wherein, the grid forming control device can detect the three-phase current signal output by the virtual synchronous generator through the current transformer, and obtain the negative sequence current value output by the virtual synchronous generator based on the three-phase current signal.

[0067] Wherein, the negative sequence current value output by the virtual synchronous generator includes: direct-axis negative sequence current value and cross-axis negative sequence current value. After the grid forming control device obtains the three-phase current signal output by the virtual synchronous generator, the three-phase current signal can be converted into the current signal in the rotating coordinate system (dq coordinate system), that is, the three-phase current signal can be converted into the current signal in the two-phase stationary coordinate system (αβ coordinate system) through Clarke transformation, and then converted into the current signal in the rotating coordinate system (dq coordinate system) through park transformation; based on the current signal in the rotating coordinate system, the direct-axis negative sequence current value and the cross-axis negative sequence current value output by the virtual synchronous generator are obtained, and the negative sequence current value output by the virtual synchronous generator is obtained.

[0068] 104. Based on the negative sequence current value output by the virtual synchronous generator and the preset negative sequence current reference value, the output voltage of the virtual synchronous generator is adjusted to adjust the negative sequence current value output by the virtual synchronous generator until the negative sequence current value output by the virtual synchronous generator reaches the negative sequence current reference value.

[0069] In the embodiments of the present application, after the network construction control device obtains the negative sequence current value output by the virtual synchronous generator, the output voltage of the virtual synchronous generator can be adjusted based on the negative sequence current value output by the virtual synchronous generator and the preset negative sequence current reference value, to adjust the negative sequence current value output by the virtual synchronous generator until the negative sequence current value output by the virtual synchronous generator reaches the negative sequence current reference value. In order to avoid the adverse effects of negative sequence current, the preset negative sequence current reference value should not be too large, and the preset negative sequence current reference value can be 5 mA or 8 A, which is not limited here.

[0070] Specifically, the output voltage of the virtual synchronous generator can be adjusted based on the deviation between the negative sequence current value output by the virtual synchronous generator and the preset negative sequence current reference value; that is, if the deviation obtained by subtracting the negative sequence current reference value from the negative sequence current value is greater than zero, the output voltage of the virtual synchronous generator is increased, and if the deviation obtained by subtracting the negative sequence current reference value from the negative sequence current value is less than zero, the output voltage of the virtual synchronous generator is decreased. Preferably, in order to reduce the negative sequence current value output by the virtual synchronous generator as much as possible, the preset negative sequence current reference value can be set to 0 A to adjust the negative sequence current value output by the virtual synchronous generator to 0 A. At this time, when the remote voltage of the virtual synchronous generator is unbalanced and drops, the negative sequence current value output by the virtual synchronous generator is greater than 0 A, the deviation obtained by subtracting the negative sequence current reference value from the negative sequence current value is greater than zero, and the output voltage of the virtual synchronous generator is increased until the negative sequence current value output by the virtual synchronous generator reaches the negative sequence current reference value (i.e. 0 A).

[0071] It can be seen that in the embodiment of the present application, it is determined whether the remote voltage of the virtual synchronous generator appears unbalanced drop; when the remote voltage of the virtual synchronous generator does not appear unbalanced drop, the output voltage of the virtual synchronous generator is obtained; when the remote voltage of the virtual synchronous generator appears unbalanced drop, the negative sequence current value output by the virtual synchronous generator is obtained; based on the negative sequence current value output by the virtual synchronous generator and the preset negative sequence current reference value, the output voltage of the virtual synchronous generator is adjusted to adjust the negative sequence current value output by the virtual synchronous generator until the negative sequence current value output by the virtual synchronous generator reaches the negative sequence current reference value. When the remote voltage of the virtual synchronous generator appears unbalanced drop, the output voltage of the virtual synchronous generator is adjusted based on the negative sequence current value output by the virtual synchronous generator and the preset negative sequence current reference value, so that the negative sequence current value output by the virtual synchronous generator can be controlled to the negative sequence current reference value, that is, the negative sequence current output by the virtual synchronous generator can be controlled when the remote voltage of the virtual synchronous generator appears unbalanced drop, and the stability of the power system is ensured.

[0072] It can be understood that in the embodiment of the present application, the virtual synchronous generator is a voltage source type device, and the network construction control method in the present application is mainly to close-loop control the negative sequence current value output by the virtual synchronous generator, that is, the network construction control method is a voltage source type negative sequence control method to control the negative sequence current in a voltage source mode. In the network construction control of the embodiment of the present application, only the output voltage of the virtual synchronous generator is adjusted to accurately control the negative sequence current value output by the virtual synchronous generator; the active power loop (active closed-loop control) and the reactive power loop (reactive closed-loop control) of the virtual synchronous generator are not affected, and the network construction inertia and damping characteristics of the virtual synchronous generator are not changed, so that the negative sequence current can be effectively controlled without changing the voltage source characteristics.

[0073] Further, the process of negative sequence control will be described in detail below, and the specific steps are as shown in Figure 4 The process of negative sequence control will be described in detail below, and the specific steps are as shown in Figure 2 The process of negative sequence control will be described in detail below, and the specific steps are as shown in

[0074] 201, based on the direct-axis negative sequence current value and the direct-axis negative sequence current reference value, and the quadrature-axis negative sequence current value and the quadrature-axis negative sequence current reference value, the negative sequence voltage component in the three-phase rotating coordinate system is determined.

[0075] In this embodiment, the grid control device can determine the negative sequence voltage component in the three-phase rotating coordinate system based on the direct-axis negative sequence current value and the direct-axis negative sequence current reference value, as well as the quadrature-axis negative sequence current value and the quadrature-axis negative sequence current reference value. The direct-axis negative sequence current reference value and the quadrature-axis negative sequence current reference value are preset current reference values, which can be 5mA or 8mA, and are not specifically limited here; preferably, the direct-axis negative sequence current reference value and the quadrature-axis negative sequence current reference value are 0A. The determination of the negative sequence voltage component in the three-phase rotating coordinate system based on the direct-axis negative sequence current value and the direct-axis negative sequence current reference value, as well as the quadrature-axis negative sequence current value and the quadrature-axis negative sequence current reference value, is specifically shown in steps 2011 and 2012 below:

[0076] 2011. The direct-axis negative-sequence voltage value is obtained based on the direct-axis negative-sequence current value and the direct-axis negative-sequence current reference value, and the quadrature-axis negative-sequence voltage value is obtained based on the quadrature-axis negative-sequence current value and the quadrature-axis negative-sequence current reference value.

[0077] In this embodiment of the application, the network control device can obtain the direct-axis negative-sequence voltage value based on the direct-axis negative-sequence current value and the direct-axis negative-sequence current reference value, and obtain the quadrature-axis negative-sequence voltage value based on the quadrature-axis negative-sequence current value and the quadrature-axis negative-sequence current reference value. For example... Figure 4 As shown, the direct-axis negative-sequence current value Id_neg_fdb (i.e., the direct-axis negative-sequence current value fed back by the virtual synchronous generator) and the direct-axis negative-sequence current reference value Id_neg_ref can be input into the PI regulator to obtain the direct-axis negative-sequence voltage value Vd_neg output by the PI regulator; the quadrature-axis negative-sequence current value Id_neg_fdb (i.e., the quadrature-axis negative-sequence current value fed back by the virtual synchronous generator) and the quadrature-axis negative-sequence current reference value Iq_neg_ref can be input into the PI regulator to obtain the quadrature-axis negative-sequence voltage value Vq_neg output by the PI regulator.

[0078] It is understood that, in the embodiments of this application, the deviation between the direct-axis negative sequence current value Id_neg_fdb and the direct-axis negative sequence current reference value Id_neg_ref can also be input into the PI regulator to obtain the direct-axis negative sequence voltage value Vd_neg output by the PI regulator; the deviation between the quadrature-axis negative sequence current value Id_neg_fdb and the quadrature-axis negative sequence current reference value Iq_neg_ref can also be input into the PI regulator to obtain the quadrature-axis negative sequence voltage value Vq_neg output by the PI regulator; the specifics are not limited here.

[0079] 2012. Convert the direct-axis negative sequence voltage value and the quadrature-axis negative sequence voltage value into negative sequence voltage components in a three-phase rotating coordinate system.

[0080] After obtaining the direct-axis negative sequence voltage value Vd_neg and the quadrature-axis negative sequence voltage value Vq_neg, the direct-axis negative sequence voltage value Vd_neg and the quadrature-axis negative sequence voltage value Vq_neg can be converted into negative sequence voltage components Va_neg, Vb_neg and Vc_neg in a three-phase rotating coordinate system.

[0081] Specifically, the direct-axis negative sequence voltage value Vd_neg and the quadrature-axis negative sequence voltage value Vq_neg can be converted into negative sequence voltage components in a two-phase stationary coordinate system (αβ coordinate system) through inverse Park transformation (ipark transformation); the corresponding formula is:

[0082]

[0083]

[0084] wherein, and are negative sequence voltage components in a two-phase stationary coordinate system, is an included angle between a rotating coordinate system and a stationary coordinate system, and can be a grid voltage phase angle.

[0085] The negative sequence voltage components in the two-phase stationary coordinate system and are converted into negative sequence voltage components Va_neg, Vb_neg and Vc_neg in a three-phase rotating coordinate system through inverse Clarke transformation (iClarke transformation); the corresponding formula is:

[0086]

[0087]

[0088]

[0089] 202、The negative sequence voltage components in the three-phase rotating coordinate system are superimposed to a grid-connection point reference voltage of an inverter of the virtual synchronous generator to adjust an output voltage of the virtual synchronous generator.

[0090] After obtaining the negative sequence voltage components Va_neg, Vb_neg and Vc_neg in the three-phase rotating coordinate system, the negative sequence voltage components in the three-phase rotating coordinate system can be superimposed to a grid-connection point reference voltage of an inverter of the virtual synchronous generator to adjust an output voltage of the virtual synchronous generator. At this time, the corresponding grid-connection point reference voltage of the inverter is:

[0091]

[0092]

[0093]

[0094] The corresponding simulation verification waveform is shown in Figure 5 、 Figure 6 and Figure 7 ; Figure 5 Uabc is the remote voltage of the virtual synchronous generator, Iabc is the remote current of the virtual synchronous generator, Figure 6 is a partial enlarged view of Figure 5 , the blue, yellow and orange lines in the Uabc waveform correspond to the three-phase (A, B and C phase) voltage waveforms, and the blue, yellow and orange lines in the Iabc waveform correspond to the three-phase (A, B and C phase) current waveforms. It can be seen that the remote voltage of the virtual synchronous generator appears unbalanced drop at 6-8, and the remote current of the virtual synchronous generator appears transient fluctuation synchronously due to voltage disturbance. Figure 7 U- is the negative sequence voltage output by the virtual synchronous generator, P- is the negative sequence active power output by the virtual synchronous generator, Q- is the negative sequence reactive power output by the virtual synchronous generator, Id_neg_fdb is the direct-axis negative sequence current value output by the virtual synchronous generator, and Iq_neg_fdb is the quadrature-axis negative sequence current value output by the virtual synchronous generator; it can be seen that when the remote voltage Uabc of the virtual synchronous generator appears unbalanced drop, the negative sequence voltage U-, the negative sequence active power P- and the negative sequence reactive power Q- will appear corresponding disturbance, and the direct-axis negative sequence current value Id_neg_fdb and the quadrature-axis negative sequence current value Iq_neg_fdb will be generated, that is, the direct-axis negative sequence current value Id_neg_fdb and the quadrature-axis negative sequence current value Iq_neg_fdb are not 0A. When the network construction control method of the embodiment of the application is adopted, the direct-axis negative sequence current value Id_neg_fdb and the quadrature-axis negative sequence current value Iq_neg_fdb can be controlled to 0A, so as to realize the control of the negative sequence current.

[0095] The embodiment of the application further provides a network construction control device, as shown in Figure 8 , comprising:

[0096] A determination unit 801 is configured to determine whether the remote voltage of the virtual synchronous generator appears unbalanced drop;

[0097] An acquisition unit 802 is configured to acquire the output voltage of the virtual synchronous generator when the determination unit determines that the remote voltage of the virtual synchronous generator does not appear unbalanced drop;

[0098] The execution unit 803 is configured to, when the determining unit determines that an unbalanced voltage drop occurs at the far end of the virtual synchronous generator, acquire the negative sequence current value output by the virtual synchronous generator; and, based on the negative sequence current value output by the virtual synchronous generator and a preset negative sequence current reference value, adjust the output voltage of the virtual synchronous generator to adjust the negative sequence current value output by the virtual synchronous generator until the negative sequence current value output by the virtual synchronous generator reaches the negative sequence current reference value.

[0099] This application also provides a voltage source device, the control method of which includes the grid-connected control method described above. The voltage source device can be an energy storage converter or a photovoltaic inverter, and is not specifically limited here.

[0100] This application embodiment also provides a network construction control device 900, such as... Figure 9 As shown, the network control device 900 of this application embodiment may include one or more central processing units (CPUs) 901 and a memory 902, wherein the memory 902 stores one or more application programs or data.

[0101] The memory 902 can be volatile or persistent storage. The program stored in the memory 902 can include one or more modules, each module including a series of instruction operations on the electronic device. Furthermore, the central processing unit 901 can be configured to communicate with the memory 902 and execute the series of instruction operations in the memory 902 on the network control device 900.

[0102] The network control device 900 may also include one or more power supplies 905, one or more wired or wireless network interfaces 904, one or more input / output interfaces 903, and / or one or more operating systems, such as Windows Server™, Mac OS X™, Unix™, Linux™, FreeBSD™, etc.

[0103] The central processing unit 901 can perform the operations performed by the first aspect or any specific method embodiment of the first aspect, which will not be described in detail here.

[0104] This application also provides a computer-readable storage medium including instructions that, when executed on a computer, cause the computer to perform the method described above.

[0105] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the foregoing method embodiments, which will not be repeated here.

[0106] In several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0107] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, that is, they can be located in one place, or can be distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0108] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0109] The integrated unit, if realized in the form of a software functional unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product, which is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, read-only memory), a random access memory (RAM, random access memory), a magnetic disk or an optical disk, and various program code storage media.

Claims

1. A network control method, characterized in that, include: Determine if there is an unbalanced voltage drop at the remote end of the virtual synchronous generator; When there is no unbalanced voltage drop at the far end of the virtual synchronous generator, the output voltage of the virtual synchronous generator is obtained; When the voltage at the far end of the virtual synchronous generator experiences an unbalanced drop, the negative sequence current value output by the virtual synchronous generator is obtained. Based on the negative sequence current value output by the virtual synchronous generator and the preset negative sequence current reference value, the output voltage of the virtual synchronous generator is adjusted to adjust the negative sequence current value output by the virtual synchronous generator until the negative sequence current value output by the virtual synchronous generator reaches the negative sequence current reference value.

2. The network control method according to claim 1, characterized in that, Determining whether an unbalanced voltage drop occurs at the far end of the virtual synchronous generator includes: Obtain the three-phase voltage signal corresponding to the remote voltage of the virtual synchronous generator; If the voltage value of any phase voltage in the three-phase voltage signal is lower than a preset voltage threshold, it is determined that the remote voltage of the virtual synchronous generator has an unbalanced drop. If the voltage values ​​of all three phases in the three-phase voltage signal are greater than or equal to the preset voltage threshold, then it is determined that the remote voltage of the virtual synchronous generator has not experienced an unbalanced drop.

3. The network control method according to claim 1, characterized in that, The step of obtaining the output voltage of the virtual synchronous generator includes: Obtain the phase angle of the active power loop output of the virtual synchronous generator and the excitation voltage of the reactive power loop output of the virtual synchronous generator; Based on the phase angle and the excitation voltage, the grid connection point reference voltage of the inverter of the virtual synchronous generator is determined, and the grid connection point reference voltage of the inverter is used as the output voltage of the virtual synchronous generator.

4. The network control method according to claim 1, characterized in that, The negative sequence current value output by the virtual synchronous generator includes: direct-axis negative sequence current value and quadrature-axis negative sequence current value; The step of obtaining the negative sequence current value output by the virtual synchronous generator includes: Obtain the three-phase current signal output by the virtual synchronous generator; The three-phase current signal is converted into a current signal in a rotating coordinate system; based on the current signal in the rotating coordinate system, the direct-axis negative sequence current value and the quadrature-axis negative sequence current value output by the virtual synchronous generator are obtained.

5. The network control method according to claim 1, characterized in that, The negative sequence current value output by the virtual synchronous generator includes: direct-axis negative sequence current value and quadrature-axis negative sequence current value; the negative sequence current reference value includes: direct-axis negative sequence current reference value and quadrature-axis negative sequence current reference value. The step of adjusting the output voltage of the virtual synchronous generator based on the negative sequence current value output by the virtual synchronous generator and a preset negative sequence current reference value includes: Based on the direct-axis negative sequence current value and the direct-axis negative sequence current reference value, and the quadrature-axis negative sequence current value and the quadrature-axis negative sequence current reference value, the negative sequence voltage component in the three-phase rotating coordinate system is determined; The negative sequence voltage component in the three-phase rotating coordinate system is superimposed on the grid connection reference voltage of the inverter of the virtual synchronous generator to adjust the output voltage of the virtual synchronous generator.

6. The network control method according to claim 5, characterized in that, The determination of the negative sequence voltage component in the three-phase rotating coordinate system based on the direct-axis negative sequence current value and the direct-axis negative sequence current reference value, and the quadrature-axis negative sequence current value and the quadrature-axis negative sequence current reference value, includes: The direct-axis negative-sequence current value and the direct-axis negative-sequence current reference value are input into the PI regulator to obtain the direct-axis negative-sequence voltage value output by the PI regulator. The cross-axis negative sequence current value and the cross-axis negative sequence current reference value are input into the PI regulator to obtain the cross-axis negative sequence voltage value output by the PI regulator; The direct-axis negative-sequence voltage value and the quadrature-axis negative-sequence voltage value are converted into negative-sequence voltage components in a three-phase rotating coordinate system.

7. The network control method according to claim 6, characterized in that, The step of converting the direct-axis negative-sequence voltage value and the quadrature-axis negative-sequence voltage value into negative-sequence voltage components in a three-phase rotating coordinate system includes: The direct-axis negative-sequence voltage value and the quadrature-axis negative-sequence voltage value are converted into negative-sequence voltage components in a two-phase stationary coordinate system by inverse Park transformation. The negative sequence voltage component in the two-phase stationary coordinate system is converted into a negative sequence voltage component in the three-phase rotating coordinate system by the inverse Clarke transformation.

8. A network construction control device, characterized in that, include: The determination unit is used to determine whether an unbalanced voltage drop occurs at the far end of the virtual synchronous generator; The acquisition unit is used to acquire the output voltage of the virtual synchronous generator when the determining unit determines that there is no unbalanced voltage drop at the far end of the virtual synchronous generator; An execution unit is configured to acquire the negative sequence current value output by the virtual synchronous generator when the determining unit determines that an unbalanced voltage drop has occurred at the far end of the virtual synchronous generator. Based on the negative sequence current value output by the virtual synchronous generator and the preset negative sequence current reference value, the output voltage of the virtual synchronous generator is adjusted to adjust the negative sequence current value output by the virtual synchronous generator until the negative sequence current value output by the virtual synchronous generator reaches the negative sequence current reference value.

9. A voltage source type device, That The characteristic is that the control method of the voltage source device includes the network control method described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes instructions that, when executed on a computer, cause the computer to perform the method as described in any one of claims 1 to 7.

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