Converter network control method, device, electronic device and storage medium

Abstract

The present invention provides a method, device, electronic device, and storage medium for converter network control, relating to the field of converter control technology. The method comprises: determining an internal potential phase angle reference value and an internal potential amplitude reference value of the converter; determining a voltage reference value of the converter based on the internal potential amplitude reference value, a first inner loop control formula, and a second inner loop control formula; converting the voltage reference value into a three-phase modulation wave based on the internal potential phase angle reference value; and modulating the voltage waveform output by the converter so that the difference between the voltage waveform and the three-phase modulation wave is within a target range based on a modulation method. The present invention retains the voltage source characteristics of the network control, ensures stable operation under capacitive loads, satisfies the full-operation-condition operation of the network control, and improves the current limiting effect of the network control.

Description

Technical Field

[0001] The present invention relates to the field of converter control technology, and in particular to a converter networking control method, device, electronic equipment and storage medium. Background Art

[0002] In recent years, with the continuous increase in the penetration rate of new energy and the extensive application of power electronic equipment, the system inertia and voltage support capacity have continued to decline. Grid control can support the stable operation of the power grid by simulating synchronous generator control and establishing its own frequency and voltage.

[0003] Currently, the current limiting method for network control mainly involves using a virtual circuit to calculate a current reference value for the network's inner loop control after the outer loop control generates the phase angle and internal potential. This is then followed by a voltage reference value generated by the inner current loop control. However, this inner loop control is unstable under capacitive load scenarios, affecting the full-condition operation of the network control. Summary of the Invention

[0004] The present invention provides a converter networking control method, device, electronic device and storage medium, which are used to solve the defect in the prior art that the inner loop control is unstable under capacitive load scenarios, affecting the full-operation condition operation of the networking control. The method retains the voltage source characteristics of the networking control, ensures stable operation under capacitive loads, meets the full-operation condition operation of the networking control, and improves the current limiting effect of the networking control.

[0005] The present invention provides a converter network control method, comprising:

[0006] determining a reference value of an internal potential phase angle of a converter and a reference value of an internal potential amplitude of the converter;

[0007] determining a voltage reference value of the converter based on the inner potential amplitude reference value, a first inner loop control formula, and a second inner loop control formula; the first inner loop control formula is used to generate a current reference value of the converter, and the second inner loop control formula is used to generate a voltage reference value of the converter; the second inner loop control formula can offset the current reference value generated by the first inner loop control formula;

[0008] Based on the internal potential phase angle reference value, converting the voltage reference value into a three-phase modulation wave;

[0009] Based on the modulation mode, the difference between the voltage waveform output by the modulated converter and the three-phase modulation wave is within a target range.

[0010] According to a converter network control method provided by the present invention, the voltage reference value of the converter is determined based on the internal potential amplitude reference value, the first inner loop control formula and the second inner loop control formula, including: determining the current reference value of the converter based on the internal potential amplitude reference value and the first inner loop control formula; determining the voltage reference value of the converter based on the current reference value and the second inner loop control formula.

[0011] According to a converter network control device provided by the present invention, determining the current reference value of the converter based on the internal potential amplitude reference value and the first inner loop control formula includes: when the converter is in steady-state operation, determining that the first inner loop control formula is an equivalent inner loop control formula, and the equivalent inner loop control formula is:

[0012]

[0013] in, for d The first current reference value on the coordinate axis, for q The second current reference value on the coordinate axis, s is the complex frequency of Laplace transform, is the proportionality coefficient, is the integration coefficient, for d The first internal potential amplitude reference value on the coordinate axis, for q The second internal potential amplitude reference value on the coordinate axis, for d The first grid-side voltage value on the coordinate axis, for q The second grid-side voltage value on the coordinate axis, for d The first converter current value on the coordinate axis, for q The second converter current value on the coordinate axis, is the equivalent reactance of the converter, is the equivalent resistance of the converter; and based on the internal potential amplitude reference value and the equivalent inner loop control formula, determines the current reference value of the converter.

[0014] According to a converter network control method provided by the present invention, determining the current reference value of the converter based on the internal potential amplitude reference value and the first inner loop control formula includes: when the converter is in a fault period, determining that the first inner loop control formula is a virtual inner loop control formula, and the virtual inner loop control formula is:

[0015]

[0016] in, for d The first current reference value on the coordinate axis, for q The second current reference value on the coordinate axis, s is the complex frequency of the Laplace transform, is the proportionality coefficient, is the integration coefficient, for d The first internal potential amplitude reference value on the coordinate axis, for q The second internal potential amplitude reference value on the coordinate axis, for d The first grid-side voltage value on the coordinate axis, for q The second grid-side voltage value on the coordinate axis, for d The first converter current value on the coordinate axis, for q The second converter current value on the coordinate axis, is the virtual reactance of the converter, is the virtual resistance of the converter; and based on the inner potential amplitude reference value and the virtual inner loop control formula, determines the current reference value of the converter.

[0017] According to a converter network control method provided by the present invention, the second inner loop control formula is:

[0018]

[0019] in, is the first voltage reference value on the d-axis, is the second voltage reference value on the q coordinate axis.

[0020] According to a converter network control method provided by the present invention, the current reference value of the converter is generated based on the internal potential amplitude reference value and the first inner loop control formula, including: when the converter is in a fault period, an initial current reference value is generated based on the internal potential amplitude reference value and the first inner loop control formula; based on a third inner loop control formula, the initial current reference value is limited to obtain the current reference value; the third inner loop control formula is used to keep the phase angle of the initial current reference value unchanged.

[0021] According to a converter network control method provided by the present invention, the determination of the internal potential phase angle reference value of the converter and the internal potential amplitude reference value of the converter includes: performing dq decomposition on the three-phase current of the power grid and the three-phase voltage of the power grid respectively to obtain the first grid-side current value on the d coordinate axis, the second grid-side current value on the q coordinate axis, the first grid-side voltage value and the second grid-side voltage value; based on the first product of the first grid-side current value and the first grid-side voltage value, and the second product of the second grid-side current value and the second grid-side voltage value, determining the The active measurement value of the converter; based on the third product of the first grid-side current value and the second grid-side voltage value, and the fourth product of the first grid-side voltage value and the second grid-side current value, determine the reactive measurement value of the converter; based on the active measurement value and the active reference value of the converter, determine the internal potential phase angle reference value; based on the reactive measurement value, the reactive reference value of the converter, the voltage amplitude of the grid connection point and the voltage reference amplitude of the grid connection point, determine the internal potential amplitude reference value, the grid connection point being the connection point between the grid and the converter.

[0022] The present invention also provides a converter network control device, comprising:

[0023] A first determining module is used to determine an internal potential phase angle reference value of the converter and an internal potential amplitude reference value of the converter;

[0024] a second determination module, configured to determine a voltage reference value of the converter based on the inner potential amplitude reference value, a first inner loop control formula, and a second inner loop control formula; the first inner loop control formula is configured to generate a current reference value of the converter, and the second inner loop control formula is configured to generate a voltage reference value of the converter; the second inner loop control formula may offset the current reference value generated by the first inner loop control formula;

[0025] a conversion module, configured to convert the voltage reference value into a three-phase modulation wave based on the internal potential phase angle reference value;

[0026] The modulation module modulates the difference between the voltage waveform output by the converter and the three-phase modulation wave to be within a target range based on the modulation mode.

[0027] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the converter network control method described above is implemented.

[0028] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the computer program implements any of the above-mentioned converter network control methods.

[0029] The present invention also provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the computer program implements any of the above-mentioned converter network control methods.

[0030] The present invention provides a method, device, electronic device and storage medium for converter networking control, which obtains converter networking control by sequentially connecting a networking outer-loop control, a networking inner-loop control and a modulation module. In the networking inner-loop control, a second inner-loop control formula can offset the current reference value generated by the first inner-loop control formula, so that the voltage reference value of the converter can be close to the internal potential amplitude reference value, fully retaining the voltage source characteristics of the networking control, ensuring stable operation under capacitive loads, meeting the full-condition operation of the networking control, and improving the current limiting effect of the networking control. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 It is a schematic diagram of the circuit structure of the voltage source converter provided by the present invention connected to the power grid.

[0033] Figure 2 It is a flow chart of the converter network control method provided by the present invention.

[0034] Figure 3 It is a structural diagram of the voltage inner loop control module provided by the present invention.

[0035] Figure 4 It is a structural diagram of the current inner loop control module provided by the present invention.

[0036] Figure 5 It is a schematic diagram of the voltage results of the fault current limiting test provided by the present invention.

[0037] Figure 6 It is a schematic diagram of the current results of the fault current limiting test provided by the present invention.

[0038] Figure 7 It is a schematic diagram of the voltage results of the capacitive load test provided by the present invention.

[0039] Figure 8 It is a schematic diagram of capacitance results of a capacitive load test provided by the present invention.

[0040] Figure 9It is a structural diagram of the converter network control device provided by the present invention.

[0041] Figure 10 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0043] Grid control is applied in various scenarios, such as renewable energy transmission, offshore wind power transmission, weak grids, and isolated grid operation. However, these scenarios place varying demands on grid-connecting equipment, such as energy storage, static var generators (SVG), and flexible DC systems, including but not limited to overcurrent capability, transient voltage support capability, inertia level, and frequency adaptability. While academia and industry have proposed numerous grid-connecting control strategies, most focus on outer-loop control for specific application scenarios, specifically the generation of phase angles and internal potentials, to meet the support requirements of these diverse scenarios.

[0044] After the outer-loop control of the network generates the phase angle and internal potential, one approach is to calculate a current reference value through a virtual circuit, and then generate a voltage reference value through the inner-loop current control. This inner-loop control is unstable under capacitive load scenarios, affecting the full-scale operation of the network control and resulting in limited current limiting effectiveness. Another approach is to calculate a virtual voltage drop using a virtual impedance and reduce the amplitude of the voltage reference value. Although this method reduces control complexity, its current limiting effectiveness is limited and can easily cause the virtual impedance to be repeatedly switched on and off.

[0045] Based on the above-mentioned problems, the converter networking control method proposed in the present invention obtains the converter networking control by sequentially connecting the networking outer loop control, the networking inner loop control and the modulation wave generation module. Among them, the second inner loop control formula in the networking inner loop control can offset the current reference value generated by the first inner loop control formula, so that the voltage reference value of the converter can be close to the internal potential amplitude reference value, completely retaining the voltage source characteristics of the networking control, ensuring stable operation under capacitive load, meeting the full working condition operation of the networking control, and improving the current limiting effect of the networking control.

[0046] The following combination Figures 1-8 The converter network control method of the present invention is described.

[0047] Figure 1This is a schematic diagram of the circuit structure of the voltage source converter provided by the present invention connected to the power grid, as shown in FIG. Figure 1 As shown, including: DC power supply U dc 101, converter 102, converter equivalent impedance 103, grid and converter connection point 104, grid equivalent impedance 105 and grid power supply U g 106, is the three-phase voltage of the power grid, is the three-phase current of the power grid, is the three-phase current of the converter.

[0048] Figure 2 This is a flow chart of the converter network control method provided by the present invention, as shown in FIG. Figure 2 Shown, including:

[0049] S201: Determine a reference value of an internal potential phase angle of a converter and a reference value of an internal potential amplitude of the converter.

[0050] It should be noted that the outputs of the power grid and the converter are both three-phase alternating current. Therefore, before determining the internal potential phase angle reference value and the internal potential amplitude reference value, the initial internal potential phase angle reference value is used to perform a two-phase rotation (dq transformation, dq) decomposition on the electrical quantities (such as voltage and current) in the three-phase stationary coordinate system to obtain dq voltage and dq current. The dq voltage and dq current are then used to calculate the internal potential phase angle reference value and the internal potential amplitude reference value.

[0051] S202 : Determine a voltage reference value of the converter based on the inner potential amplitude reference value, a first inner loop control formula, and a second inner loop control formula.

[0052] The first inner loop control formula is used to generate a current reference value of the converter, and the second inner loop control formula is used to generate a voltage reference value of the converter; the second inner loop control formula can offset the current reference value generated by the first inner loop control formula;

[0053] S203 : Based on the internal potential phase angle reference value, convert the voltage reference value into a three-phase modulation wave.

[0054] S204 : Based on the modulation mode, modulate the voltage waveform output by the converter so that the difference between the voltage waveform and the three-phase modulation waveform is within a target range.

[0055] Here, the target interval may be an interval close to zero, that is, the voltage waveform output by the converter approaches a three-phase modulation wave.

[0056] It should be noted that the converter can be a flexible DC converter. Flexible DC is a high-voltage DC transmission system based on a voltage source converter. In the grid control mode, the flexible DC transmission system autonomously maintains the stability of the grid voltage / frequency through a fast and precise inner-loop control strategy.

[0057] Here, the internal potential phase angle reference value is used to describe the angular position of the internal potential (i.e., no-load electromotive force) of the generator or synchronous motor relative to a certain reference phasor during operation.

[0058] Here, the internal potential amplitude reference value and the internal potential phase angle reference value can be obtained based on the voltage and current, wherein the internal potential amplitude reference value and the internal potential phase angle reference value can be determined by any appropriate method, for example, by substituting the voltage and current into the calculation formula.

[0059] Exemplarily, the internal potential amplitude reference value can be obtained through reactive voltage control, the internal potential phase angle reference value can be obtained through active power control, and the active power measurement value and reactive power measurement value can be calculated by the data processing module using the current and voltage after dq decomposition.

[0060] Exemplarily, determining the internal potential phase angle reference value of the converter and the internal potential amplitude reference value of the converter includes: Perform dq decomposition on the three-phase current of the power grid and the three-phase voltage of the power grid respectively to obtain a first grid-side current value on the d-axis, a second grid-side current value on the q-axis, the first grid-side voltage value, and the second grid-side voltage value; determine the active measurement value of the converter based on a first product of the first grid-side current value and the first grid-side voltage value, and a second product of the second grid-side current value and the second grid-side voltage value; determine the reactive measurement value of the converter based on a third product of the first grid-side current value and the second grid-side voltage value, and a fourth product of the first grid-side voltage value and the second grid-side current value; determine the internal potential phase angle reference value based on the active measurement value and the active reference value of the converter; determine the internal potential amplitude reference value based on the reactive measurement value, the reactive reference value of the converter, the voltage amplitude of the grid-connected point, and the voltage reference amplitude of the grid-connected point, where the grid-connected point is the connection point between the power grid and the converter.

[0061] Here, the three-phase voltage of the grid is Figure 1 middle , the three-phase current of the power grid is Figure 1 in , the three-phase current of the converter is Figure 1 in , where the three-phase current of the converter can also be called the valve-side three-phase current.

[0062] Here, the active power measurement value may be the sum of the first product and the second product or a weighted sum of the first product and the second product. The reactive power measurement value may be the difference between the third product and the fourth product or a weighted difference.

[0063] For example, the internal potential phase angle reference value is calculated according to the calculation formula, and the internal potential phase angle reference value is The calculation formula is as follows:

[0064]

[0065] in, and are the inertia time constant and damping coefficient, respectively, is the active reference value after primary frequency modulation and DC voltage control adjustment, is the rated angular velocity, It is the active power measurement value.

[0066] For example, the internal potential amplitude reference value is calculated according to the calculation formula, and the internal potential amplitude reference value is The calculation formula is as follows:

[0067]

[0068] in, and is the PI control parameter of voltage and reactive power droop, and are the grid connection point voltage and reactive power reference values ​​respectively, is the reactive power measurement value, is the droop coefficient.

[0069] For example, the data processing module performs data processing including: collecting the three-phase voltage of the grid side; , three-phase current on the grid side , valve side three-phase current , using the internal potential phase angle reference value, 、 and Perform dq decomposition to obtain the grid voltage on the d coordinate axis V sd That is, the first grid-side voltage value, the grid voltage on the q coordinate axis V sq That is, the second grid side voltage value, the grid current on the d coordinate axis I sd That is, the first grid-side current value, the grid current on the q coordinate axis I sq That is, the second grid-side current value, the first converter current on the d-axis I dand the second converter current on the q axis I q ,Will V sd and I sd The product of V sq and I sq The product of the active power measurement value is obtained , will V sq and I sd The product of minus V sd and I sq The product of the reactive power measurement value is obtained .

[0070] In another embodiment, the three-phase voltage on the grid side , three-phase current on the grid side , valve side three-phase current After dq decomposition, the decomposed electrical signal can be filtered by a low-pass filter to obtain V sd 、 V sq 、 I sd 、 I sq 、 I d and I q .

[0071] In an embodiment of the present invention, three-phase current and voltage data are collected through a data processing module, dq decomposition is performed on the three-phase current and voltage data, and reactive measurement values ​​and active measurement values ​​are calculated to improve the accuracy of the data, thereby improving the precise control of the inner loop control strategy.

[0072] It should be noted that the principle of the second inner loop control formula to offset the current reference value is to first substitute the internal potential amplitude reference value into the first inner loop control formula to obtain the current reference value of the converter, and then substitute the current reference value into the second control formula to obtain a voltage reference value close to the internal potential amplitude reference value by offsetting the current reference value.

[0073] It should be noted that the inner loop control of the network can meet the requirements of the steady-state operation of the converter and the situation of the converter side flow fault.

[0074] Specifically, the network outer loop control generates an internal potential phase angle reference value and an internal potential amplitude reference value of the converter and inputs them into the network inner loop control. The network inner loop control substitutes the internal potential amplitude reference value into the first inner loop control formula to generate a current reference value of the converter. The current reference value is substituted into the second inner loop control formula to obtain a voltage reference value of the converter. The voltage reference value is converted into a three-phase modulation wave. The modulation module modulates the voltage waveform output by the converter based on the modulation method so that the difference between the three-phase modulation wave and the voltage waveform is within a target range.

[0075] In an embodiment of the present invention, the network control of the converter is obtained by sequentially connecting the network outer loop control, the network inner loop control and the modulation module, wherein the second inner loop control formula in the network inner loop control can offset the current reference value generated by the first inner loop control formula, so that the voltage reference value of the converter can approach the internal potential amplitude reference value, completely retaining the voltage source characteristics of the network control, ensuring stable operation under capacitive load, meeting the full working condition operation of the network control, and improving the current limiting effect of the network control.

[0076] Further, determining the voltage reference value of the converter based on the internal potential amplitude reference value, the first inner loop control formula and the second inner loop control formula includes: determining the current reference value of the converter based on the internal potential amplitude reference value and the first inner loop control formula; determining the voltage reference value of the converter based on the current reference value and the second inner loop control formula.

[0077] It should be noted that the voltage inner loop control is used to generate the current reference value, and the current inner loop control is used to generate the voltage reference value.

[0078] In an embodiment of the present invention, by combining the voltage inner loop control and the current inner loop control using the first inner loop control formula and the second inner loop control formula, the converter achieves the effect of offsetting the inner loop, thereby ensuring stable operation under capacitive load.

[0079] In one embodiment, determining the current reference value of the converter based on the inner potential amplitude reference value and the first inner loop control formula includes: when the converter is in steady-state operation, determining that the first inner loop control formula is an equivalent inner loop control formula, and the equivalent inner loop control formula is:

[0080]

[0081] in, for d The first current reference value on the coordinate axis, for q The second current reference value on the coordinate axis, s is the complex frequency of Laplace transform, is the proportionality coefficient, is the integration coefficient, for d The first internal potential amplitude reference value on the coordinate axis, for q The second internal potential amplitude reference value on the coordinate axis, for d The first grid-side voltage value on the coordinate axis, for q The second grid-side voltage value on the coordinate axis, for d The first converter current value on the coordinate axis, for q The second converter current value on the coordinate axis, is the equivalent reactance of the converter, is the equivalent resistance of the converter; and based on the internal potential amplitude reference value and the equivalent inner loop control formula, determines the current reference value of the converter.

[0082] It should be noted that the current reference value can be determined by the voltage inner loop control module. Figure 3 This is a schematic diagram of the structure of the voltage inner loop control module provided by the present invention. Figure 3 As shown, the internal potential amplitude reference value is decomposed into dq to obtain the first internal potential amplitude reference value on the d coordinate axis. and the second internal potential amplitude reference value on the q coordinate axis Here, the current reference value includes a first current reference value on the d coordinate axis and a second current reference value on the q coordinate axis. Taking the d coordinate axis as an example, Figure 3 in Generating unit 301, and the first grid-side voltage value on the d-axis Subtract and get the first difference, and use the virtual reactance and the second converter current value on the q axis Multiply the negative value of the virtual resistance by the first product. and the first converter current value on the d-axis Multiply them to get the second product, subtract the first product and the second product from the first difference to get the second difference, and add the second difference to the formula Multiply them to get the third product, add the third product to the first converter current value on the d coordinate axis , get the first current reference value on the d coordinate axis Similarly, the second current reference value on the q coordinate axis Generation principle and first current reference value The principle is the same, such as Figure 3 in The generation unit 302 is not described in detail here.

[0083] It should be noted that when the converter is in steady state operation, Figure 3 Virtual reactance in and virtual resistance Replace with equivalent reactance and equivalent resistance .

[0084] In an embodiment of the present invention, when the circuit is in steady-state operation, the voltage inner-loop control and the current inner-loop control are combined by utilizing the first inner-loop control formula and the second inner-loop control formula, so that the converter can achieve the effect of offsetting the inner loop, thereby ensuring stable operation under capacitive load.

[0085] In another embodiment, determining the current reference value of the converter based on the inner potential amplitude reference value and the first inner loop control formula includes:

[0086] When the converter is in a fault period, it is determined that the first inner loop control formula is a virtual inner loop control formula, and the virtual inner loop control formula is:

[0087]

[0088] in, for d The first current reference value on the coordinate axis, for q The second current reference value on the coordinate axis, s is the complex frequency of the Laplace transform, is the proportionality coefficient, is the integration coefficient, for d The first internal potential amplitude reference value on the coordinate axis, for q The second internal potential amplitude reference value on the coordinate axis, for d The first grid-side voltage value on the coordinate axis, for q The second grid-side voltage value on the coordinate axis, for d The first converter current value on the coordinate axis, for q The second converter current value on the coordinate axis, is the virtual reactance of the converter, is the virtual resistance of the converter;

[0089] A current reference value of the converter is determined based on the inner potential amplitude reference value and the virtual inner loop control formula.

[0090] Here, a fault refers to an AC voltage positive-sequence component less than 0.85 per-unit (pu) or a zero-sequence component greater than 0.05 pu. In the event of a fault, the flexible HVDC system enters fault ride-through control, and virtual impedance is activated through the converter voltage inner loop control. The virtual impedance is removed after the fault is cleared.

[0091] Here, virtual impedance (i.e., virtual resistance and virtual reactance) simulates the electrical characteristics of traditional physical impedances (such as resistance, inductance, or capacitance) through control algorithms without actually adding physical components.

[0092] It should be noted that the value of the virtual reactance and the value of the virtual resistance can be a preset value or calculated in real time. The values ​​of the virtual resistance and virtual reactance can be calculated by the total amplitude of the virtual impedance. After the total amplitude of the virtual impedance is calculated, the ratio of resistance to reactance can be set as needed to obtain the final virtual resistance and virtual reactance. The calculation formula is as follows:

[0093]

[0094] in, is the maximum current amplitude, is the phase angle difference between the grid connection point voltage and the internal potential, is the reference value of the internal potential amplitude, is the voltage amplitude at the grid connection point, which is the connection point between the grid and the converter. is the imaginary unit.

[0095] Here, the control structure of increasing the virtual impedance to generate the current reference value can refer to Figure 3 control structure.

[0096] In the embodiment of the present invention, after a current fault occurs in the circuit, the current reference value generated by the voltage inner loop control is reduced by increasing the virtual impedance, thereby achieving the effect of current limiting.

[0097] Furthermore, the second inner loop control formula is:

[0098]

[0099] in, is the first voltage reference value on the d-axis, is the second voltage reference value on the q coordinate axis.

[0100] It should be noted that when the circuit is operating in a steady state, the voltage inner loop control and the current inner loop control are combined using the equivalent inner loop control formula and the second inner loop control formula to achieve the effect of offsetting the inner loop. When a circuit fails, a virtual impedance is added to the virtual inner loop control formula, and the current reference value is reduced. Then, the second inner loop control formula is used to obtain the voltage reference value based on the current reference value obtained after adding the impedance, and the output voltage of the converter is controlled to be the voltage reference value, thereby achieving the effect of current limiting.

[0101] It should be noted that the voltage reference value can be determined by the current inner loop control module. Figure 4 This is a schematic diagram of the structure of the current inner loop control module provided by the present invention. Figure 4 As shown, taking the d coordinate axis as an example, Figure 4 in The generating unit 401 converts the first current reference value on the d coordinate axis into Subtract the first converter current value on the d axis , get the third difference, and convert the equivalent reactance and the second converter current value on the q axis Multiply the negative value of the fourth product to get the equivalent resistance and the first converter current value on the d-axis Multiply them together to get the fifth product, and add the third difference to the formula Multiply them to get the sixth product, and multiply the fourth product, the fifth product, the sixth product and the first grid-side voltage value on the d coordinate axis Add together to get the first voltage reference value on the d coordinate axis Similarly, the second voltage reference value on the q coordinate axis Generation principle and first voltage reference value The principle is the same, such as Figure 4 in The generation unit 402 is not described in detail here.

[0102] In an embodiment of the present invention, for the equivalent inner loop control formula, the second inner loop control formula can offset the effect of the equivalent inner loop and maintain steady-state operation of the circuit. For the virtual inner loop control formula, the second inner loop control formula can reduce the voltage according to the virtual inner loop control formula, thereby achieving the purpose of current limiting.

[0103] In another embodiment, the current reference value of the converter is generated based on the internal potential amplitude reference value and the first inner loop control formula, including: when the converter is in a fault period, an initial current reference value is generated based on the internal potential amplitude reference value and the first inner loop control formula; based on a third inner loop control formula, the initial current reference value is limited to obtain the current reference value; the third inner loop control formula is used to keep the phase angle of the initial current reference value unchanged.

[0104] It should be noted that the initial current reference value may be obtained according to an equivalent inner loop control formula or a virtual inner loop control formula.

[0105] It should be noted that the third inner loop control formula can be combined with the equivalent inner loop control formula to form the first current limiting method; the third inner loop control formula can be combined with the virtual inner loop control formula to form the second current limiting method; the virtual inner loop control formula alone constitutes the third current limiting method.

[0106] In the embodiment of the present invention, the reference current of the voltage inner loop control is reduced by current saturation limiting, thereby causing the voltage inner loop control to reduce the voltage reference value, thereby reducing the output voltage of the converter and achieving the purpose of current limiting.

[0107] Furthermore, the third inner loop control formula is:

[0108]

[0109] in, is the maximum current amplitude, and arctan is the inverse tangent function.

[0110] It should be noted that the third inner loop control formula may be to use the current reference value saturation limiting to lower the initial current reference value, and the current amplitude calculated in the current saturation limiting is the positive sequence current amplitude.

[0111] It should be noted that when a serious three-phase unbalanced fault occurs, if the negative sequence current control lags, there is a possibility that one or two phases will overcurrent in the initial stage of the fault. When this current limiting method is used alone, the negative sequence current suppression function is required to be high. Therefore, the two current limiting methods, the virtual inner loop control formula and the third inner loop control method, can be combined to achieve the current limiting effect.

[0112] In the embodiment of the present invention, the reference current of the voltage inner loop control is reduced by current saturation limiting, thereby causing the voltage inner loop control to reduce the voltage reference value, thereby reducing the output voltage of the converter and achieving the purpose of current limiting.

[0113] The converter network control device provided by the present invention was applied to two sending-end converter stations, and tests on fault current limiting and capacitive load connection were performed respectively:

[0114] Figure 5 FIG. 1 is a schematic diagram of the voltage results of the fault current limiting test provided by the present invention, such as Figure 5 As shown in the figure, the horizontal axis represents time and the vertical axis represents voltage. It is assumed that a three-phase metallic grounding fault occurs on the AC grid side of one of the converter stations at t=0.2 seconds (s), the fault resistance is 0.1 ohm, the fault lasts for 1 second, and 0.2-1.2 seconds is the fault period. During the fault period, the three-phase voltage drops to 0.

[0115] Figure 6 FIG. 1 is a schematic diagram of the current results of the fault current limiting test provided by the present invention, as shown in FIG. Figure 6 As shown, the horizontal axis represents time and the vertical axis represents current. The three-phase fault current does not exceed the current transient limit (1.3pu). Figure 5 and 6 It shows that the converter network control device proposed in the present invention is effective.

[0116] Figure 7 FIG. 1 is a schematic diagram of the voltage results of the capacitive load test provided by the present invention, as shown in FIG. Figure 7 As shown, the horizontal axis represents time and the vertical axis represents voltage. The load of one of the converter stations is set to 0. When t=6s, a capacitive load of 0.3pu is applied and maintained for 2s. It can be seen that the voltage is stable after 6s.

[0117] Figure 8 Schematic diagram of capacitance results of capacitive load test provided by the present invention, as shown in FIG. Figure 8 As shown, the horizontal axis represents time and the vertical axis represents capacitance. It can be seen that at t=6s, after the capacitive load of 0.3pu is input, the reactive power is -0.3pu. Figure 7 and 8 It shows that the converter network control device provided by the present invention is applicable to the working condition of capacitive load.

[0118] The converter networking control device provided by the present invention is described below. The converter networking control device described below and the converter networking control method described above can be referenced to each other.

[0119] Figure 9 This is a schematic diagram of the structure of the converter network control device provided by the present invention. Figure 9 As shown, the converter network control device 900 includes:

[0120] A first determining module 910 is configured to determine a reference value of an internal potential phase angle of a converter and a reference value of an internal potential amplitude of the converter;

[0121] a second determining module 920, configured to determine a voltage reference value of the converter based on the inner potential amplitude reference value, a first inner loop control formula, and a second inner loop control formula; the first inner loop control formula is configured to generate a current reference value of the converter, and the second inner loop control formula is configured to generate a voltage reference value of the converter; the second inner loop control formula may offset the current reference value generated by the first inner loop control formula;

[0122] A conversion module 930 is configured to convert the voltage reference value into a three-phase modulation wave based on the internal potential phase angle reference value;

[0123] The modulation module 940 is configured to modulate the voltage waveform output by the converter so that the difference between the voltage waveform output by the converter and the three-phase modulation waveform falls within a target range based on a modulation method.

[0124] In one embodiment, the second determination module 920 is specifically used to: determine the current reference value of the converter based on the internal potential amplitude reference value and the first inner loop control formula; determine the voltage reference value of the converter based on the current reference value and the second inner loop control formula.

[0125] In one embodiment, the second determining module 920 is further specifically configured to: when the converter is in steady-state operation, determine that the first inner-loop control formula is an equivalent inner-loop control formula, and the equivalent inner-loop control formula is:

[0126]

[0127] in, for d The first current reference value on the coordinate axis, for q The second current reference value on the coordinate axis, s is the complex frequency of the Laplace transform, is the proportionality coefficient, is the integration coefficient, for d The first internal potential amplitude reference value on the coordinate axis, for q The second internal potential amplitude reference value on the coordinate axis, for d The first grid-side voltage value on the coordinate axis, for q The second grid-side voltage value on the coordinate axis, for d The first converter current value on the coordinate axis, for q The second converter current value on the coordinate axis, is the equivalent reactance of the converter, is the equivalent resistance of the converter; and based on the internal potential amplitude reference value and the equivalent inner loop control formula, determines the current reference value of the converter.

[0128] In one embodiment, the second determination module 920 is further specifically configured to: determine the current reference value of the converter based on the inner potential amplitude reference value and the first inner loop control formula, including: when the converter is in a fault period, determining that the first inner loop control formula is a virtual inner loop control formula, and the virtual inner loop control formula is:

[0129]

[0130] in, for d The first current reference value on the coordinate axis, for q The second current reference value on the coordinate axis, s is the complex frequency of the Laplace transform, is the proportionality coefficient, is the integration coefficient, for d The first internal potential amplitude reference value on the coordinate axis, for q The second internal potential amplitude reference value on the coordinate axis, for d The first grid-side voltage value on the coordinate axis, for q The second grid-side voltage value on the coordinate axis, for d The first converter current value on the coordinate axis, for q The second converter current value on the coordinate axis, is the virtual reactance of the converter, is the virtual resistance of the converter; and based on the inner potential amplitude reference value and the virtual inner loop control formula, determines the current reference value of the converter.

[0131] In one embodiment, the second inner loop control formula is:

[0132]

[0133] in, for d The first voltage reference value on the coordinate axis, for q The second voltage reference value on the coordinate axis.

[0134] In one embodiment, the second determination module 920 is further specifically used to: generate an initial current reference value based on the internal potential amplitude reference value and the first inner loop control formula when the converter is in a fault period; limit the initial current reference value based on the third inner loop control formula to obtain the current reference value; the third inner loop control formula is used to keep the phase angle of the initial current reference value unchanged.

[0135] In one embodiment, the first determination module 910 is specifically used to: perform dq decomposition on the three-phase current of the power grid and the three-phase voltage of the power grid respectively to obtain the first grid-side current value on the d-axis, the second grid-side current value on the q-axis, the first grid-side voltage value and the second grid-side voltage value; determine the active measurement value of the converter based on the first product of the first grid-side current value and the first grid-side voltage value, and the second product of the second grid-side current value and the second grid-side voltage value; determine the reactive measurement value of the converter based on the third product of the first grid-side current value and the second grid-side voltage value, and the fourth product of the first grid-side voltage value and the second grid-side current value; determine the internal potential phase angle reference value based on the active measurement value and the active reference value of the converter; determine the internal potential amplitude reference value based on the reactive measurement value, the reactive reference value of the converter, the voltage amplitude of the grid connection point and the voltage reference amplitude of the grid connection point, where the grid connection point is the connection point between the power grid and the converter.

[0136] Figure 10 An example of a physical structure diagram of an electronic device is shown below. Figure 10 As shown, the electronic device may include: a processor (processor) 1010 , a communication interface (Communications Interface) 1020 , a memory (memory) 1030 and a communication bus 1040 , wherein the processor 1010 , the communication interface 1020 , and the memory 1030 communicate with each other via the communication bus 1040 . The processor 1010 can call the logic instructions in the memory 1030 to execute the converter network control method, which includes: determining the internal potential phase angle reference value of the converter and the internal potential amplitude reference value of the converter; determining the voltage reference value of the converter based on the internal potential amplitude reference value, the first inner loop control formula and the second inner loop control formula; the first inner loop control formula is used to generate the current reference value of the converter, and the second inner loop control formula is used to generate the voltage reference value of the converter; the second inner loop control formula can offset the current reference value generated by the first inner loop control formula; based on the internal potential phase angle reference value, the voltage reference value is converted into a three-phase modulation wave; based on the modulation method, the difference between the voltage waveform output by the modulated converter and the three-phase modulation wave is in the target range.

[0137] Furthermore, the logic instructions in the aforementioned memory 1030 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0138] On the other hand, the present invention also provides a computer program product, which includes a computer program, which can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the converter network control method provided by the above methods, which includes: determining the internal potential phase angle reference value of the converter and the internal potential amplitude reference value of the converter; determining the voltage reference value of the converter based on the internal potential amplitude reference value, the first inner loop control formula and the second inner loop control formula; the first inner loop control formula is used to generate the current reference value of the converter, and the second inner loop control formula is used to generate the voltage reference value of the converter; the second inner loop control formula can offset the current reference value generated by the first inner loop control formula; based on the internal potential phase angle reference value, the voltage reference value is converted into a three-phase modulation wave; based on the modulation method, the difference between the voltage waveform output by the modulated converter and the three-phase modulation wave is in a target range.

[0139] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the converter network control method provided by the above-mentioned methods, the method comprising: determining the internal potential phase angle reference value of the converter and the internal potential amplitude reference value of the converter; determining the voltage reference value of the converter based on the internal potential amplitude reference value, the first inner loop control formula and the second inner loop control formula; the first inner loop control formula is used to generate the current reference value of the converter, and the second inner loop control formula is used to generate the voltage reference value of the converter; the second inner loop control formula can offset the current reference value generated by the first inner loop control formula; based on the internal potential phase angle reference value, converting the voltage reference value into a three-phase modulation wave; based on the modulation method, the difference between the voltage waveform output by the modulated converter and the three-phase modulation wave is in a target range.

[0140] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0141] Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented using software plus a necessary general-purpose hardware platform, or of course, hardware. Based on this understanding, the essence of the above technical solution, or the portion that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, or an optical disk, and includes a number of instructions for causing a computer device (such as a personal computer, server, or network device) to execute the methods described in each embodiment or certain portions of the embodiments.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for controlling a converter network, characterized in that: include: determining a reference value of an internal potential phase angle of a converter and a reference value of an internal potential amplitude of the converter; Determining a current reference value of the converter based on the inner potential amplitude reference value and a first inner loop control formula; The first inner loop control formula is used to generate a current reference value of the converter; Determining a voltage reference value of the converter based on the current reference value and a second inner loop control formula; The second inner loop control formula is used to generate a voltage reference value of the converter; The second inner loop control formula can offset the current reference value generated by the first inner loop control formula; Based on the internal potential phase angle reference value, converting the voltage reference value into a three-phase modulation wave; Based on the modulation mode, the difference between the voltage waveform output by the converter and the three-phase modulation waveform is modulated to be within a target range; The step of determining the current reference value of the converter based on the inner potential amplitude reference value and the first inner loop control formula includes: When the converter is in steady-state operation, the first inner-loop control formula is determined to be an equivalent inner-loop control formula, and the equivalent inner-loop control formula is: in, is the first current reference value on the d-axis, is the second current reference value on the q axis, s is the complex frequency of Laplace transform, is the proportionality coefficient, is the integration coefficient, is the first internal potential amplitude reference value on the d coordinate axis, is the second internal potential amplitude reference value on the q coordinate axis, is the first grid-side voltage value on the d-axis, is the second grid-side voltage value on the q coordinate axis, is the first converter current value on the d-axis, is the second converter current value on the q axis, is the equivalent reactance of the converter, is the equivalent resistance of the converter; Determining a current reference value of the converter based on the inner potential amplitude reference value and the equivalent inner loop control formula; When the converter is in a fault period, it is determined that the first inner loop control formula is a virtual inner loop control formula, and the virtual inner loop control formula is: in, is the first current reference value on the d-axis, is the second current reference value on the q axis, s is the complex frequency of Laplace transform, is the proportionality coefficient, is the integration coefficient, is the first internal potential amplitude reference value on the d coordinate axis, is the second internal potential amplitude reference value on the q coordinate axis, is the first grid-side voltage value on the d-axis, is the second grid-side voltage value on the q coordinate axis, is the first converter current value on the d-axis, is the second converter current value on the q axis, is the virtual reactance of the converter, is the virtual resistance of the converter; A current reference value of the converter is determined based on the inner potential amplitude reference value and the virtual inner loop control formula.

2. The converter network control method according to claim 1, characterized in that: The second inner loop control formula is: in, is the first voltage reference value on the d-axis, is the second voltage reference value on the q coordinate axis, is the equivalent reactance of the converter, is the equivalent resistance of the converter.

3. The converter network control method according to claim 1, characterized in that: The step of generating a current reference value of the converter based on the inner potential amplitude reference value and the first inner loop control formula includes: When the converter is in a fault period, generating an initial current reference value based on the inner potential amplitude reference value and the first inner loop control formula; Based on a third inner loop control formula, the initial current reference value is limited to obtain the current reference value; the third inner loop control formula is used to keep the phase angle of the initial current reference value unchanged.

4. The converter network control method according to claim 2, characterized in that: Determining the internal potential phase angle reference value of the converter and the internal potential amplitude reference value of the converter includes: Performing dq decomposition on the three-phase current of the power grid and the three-phase voltage of the power grid respectively to obtain a first grid-side current value on the d coordinate axis, a second grid-side current value on the q coordinate axis, the first grid-side voltage value, and the second grid-side voltage value; determining an active power measurement value of the converter based on a first product of the first grid-side current value and the first grid-side voltage value and a second product of the second grid-side current value and the second grid-side voltage value; determining a reactive measurement value of the converter based on a third product of the first grid-side current value and the second grid-side voltage value and a fourth product of the first grid-side voltage value and the second grid-side current value; Determining the internal potential phase angle reference value based on the active power measurement value and the active power reference value of the converter; The internal potential amplitude reference value is determined based on the reactive measurement value, the reactive reference value of the converter, the voltage amplitude of the grid connection point and the voltage reference amplitude of the grid connection point, where the grid connection point is the connection point between the power grid and the converter.

5. A converter network control device, characterized in that: include: A first determining module is used to determine an internal potential phase angle reference value of the converter and an internal potential amplitude reference value of the converter; a second determining module, configured to determine a current reference value of the converter based on the inner potential amplitude reference value and a first inner loop control formula; The first inner loop control formula is used to generate a current reference value of the converter; determining a voltage reference value of the converter based on the current reference value and a second inner-loop control formula; the second inner-loop control formula is used to generate the voltage reference value of the converter; the second inner-loop control formula can offset the current reference value generated by the first inner-loop control formula; a conversion module, configured to convert the voltage reference value into a three-phase modulation wave based on the internal potential phase angle reference value; a modulation module, configured to modulate the voltage waveform output by the converter so that the difference between the voltage waveform output by the converter and the three-phase modulation waveform falls within a target range based on a modulation mode; The second determining module is further configured to determine, when the converter is in steady-state operation, that the first inner-loop control formula is an equivalent inner-loop control formula, where the equivalent inner-loop control formula is: in, is the first current reference value on the d-axis, is the second current reference value on the q axis, s is the complex frequency of Laplace transform, is the proportionality coefficient, is the integration coefficient, is the first internal potential amplitude reference value on the d coordinate axis, is the second internal potential amplitude reference value on the q coordinate axis, is the first grid-side voltage value on the d-axis, is the second grid-side voltage value on the q coordinate axis, is the first converter current value on the d-axis, is the second converter current value on the q axis, is the equivalent reactance of the converter, is the equivalent resistance of the converter; based on the internal potential amplitude reference value and the equivalent inner loop control formula, determining the current reference value of the converter; when the converter is in a fault period, determining that the first inner loop control formula is a virtual inner loop control formula, and the virtual inner loop control formula is: in, is the first current reference value on the d-axis, is the second current reference value on the q axis, s is the complex frequency of Laplace transform, is the proportionality coefficient, is the integration coefficient, is the first internal potential amplitude reference value on the d coordinate axis, is the second internal potential amplitude reference value on the q coordinate axis, is the first grid-side voltage value on the d-axis, is the second grid-side voltage value on the q coordinate axis, is the first converter current value on the d-axis, is the second converter current value on the q axis, is the virtual reactance of the converter, is the virtual resistance of the converter; and based on the inner potential amplitude reference value and the virtual inner loop control formula, determines the current reference value of the converter.

6. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the converter network control method according to any one of claims 1 to 4 is implemented.

7. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the converter network control method according to any one of claims 1 to 4 is implemented.

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