Transient impact stabilization control method, system and equipment of flexible direct current system and medium

Abstract

The invention provides a transient impact stabilization control method, system, equipment and medium for a flexible direct current system, and the method comprises the steps: determining a final trigger signal of each submodule in a converter through the corrected modulation wave index of each phase of upper and lower bridge arms in the converter; the average operating voltage of the converter sub-modules is reduced, the surplus power in the converter can be ensured to be reduced when the converter has a power transmission fault, and the capacity demand required by an energy consumption device for absorbing the surplus power to realize fault ride-through is reduced, so that the overvoltage level of the flexible direct current system is reduced, the flexible direct current system is prevented from forming transient impact, and the fault ride-through performance of the flexible direct current system is improved. And the operation cost of the flexible direct current system is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current transmission, and in particular to a transient impulse smoothing control method, system, equipment and medium for a flexible direct current system. Background Art

[0002] Flexible direct current transmission is an important technical means to achieve large-scale renewable energy power plant transmission and long-distance power transmission. In a large-scale wind farm connected to the grid through a flexible direct current system, when a power transmission failure occurs in the receiving AC grid, the wind farm cannot quickly reduce the output voltage due to the delay in detection, communication and response. The surplus power in the flexible direct current system causes overvoltage in the flexible direct current system and disconnection of the wind farm from the grid within a few milliseconds to tens of milliseconds. In order to improve the ability of the flexible direct current system to ride through power transmission failures, the current mainstream technical solution is to configure AC or DC energy dissipation devices to dissipate the surplus power fed into the wind farm in the form of internal resistance heat energy.

[0003] However, the parameter configurations of the AC and DC energy dissipation devices are all configured in accordance with the rated transmission power of the flexible DC system for 1 to 2 seconds. The cost of the energy dissipation device is directly related to the thermal capacity of its internal resistor, which is not conducive to reducing the operating cost of the flexible DC system. Summary of the invention

[0004] In order to solve the problem of operating cost of flexible direct current system in the prior art, the present invention proposes a transient impulse smoothing control method of flexible direct current system, the method comprising:

[0005] Based on the active power, reactive power, bridge arm current, circulating current and preset power-circulating current control algorithm of the converter in the flexible DC system, the modulation wave index of the upper and lower bridge arms of each phase in the converter is determined;

[0006] Based on the correction coefficient, the modulation wave index of the upper and lower bridge arms of each phase in the converter is corrected to obtain the corrected modulation wave index of the upper and lower bridge arms of each phase in the converter;

[0007] The modified modulation wave index of the upper and lower bridge arms of each phase in the converter is input into the voltage modulation-voltage equalization algorithm to generate the final trigger signal of each submodule in the converter, so as to reduce the average operating voltage of the submodules in the converter.

[0008] Preferably, the process of determining the correction coefficient includes:

[0009] Determining a first correction parameter based on the number of submodules and the number of faulty submodules in each phase bridge arm;

[0010] Determine a second correction parameter based on a DC component, a fundamental frequency component amplitude, and a double frequency component amplitude in the converter output voltage, wherein the fundamental frequency component amplitude is the component amplitude in the converter output voltage whose frequency is equal to the fundamental frequency of the power grid, and the double frequency component amplitude is the component amplitude in the converter output voltage whose frequency is twice the fundamental frequency of the power grid;

[0011] The ratio of the first correction parameter to the second correction parameter is used as the correction coefficient.

[0012] Preferably, the determination of the first correction parameter satisfies the following formula:

[0013] C1=1-Nf / N

[0014] Among them, C1 is the first correction parameter, N is the number of submodules in each phase bridge arm, and N f is the number of submodules with fault bypass in each phase bridge arm.

[0015] Preferably, the determination of the second correction parameter satisfies the following formula:

[0016]

[0017] Among them, C2 is the second correction parameter, U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component.

[0018] Preferably, the modulation wave index of the upper and lower bridge arms of each phase in the converter is determined based on the active power, reactive power, bridge arm current, circulating current and a preset power-circulating current control algorithm of the converter in the flexible direct current system, including:

[0019] Determine the DC component, the amplitude of the fundamental frequency component and the amplitude of the double frequency component in the output voltage of the converter based on the active power, the reactive power, the bridge arm current and the circulating current;

[0020] Based on the DC component, the amplitude of the fundamental frequency component, the amplitude of the double frequency component and the preset power-circulating current control algorithm, the modulation wave index of the upper and lower bridge arms of each phase in the converter is determined.

[0021] Preferably, the modulation wave index of the upper and lower bridge arms of each phase in the converter is determined to satisfy the following formula:

[0022]

[0023] Among them, n u_old is the modulation wave index of the upper bridge arm, n l_old is the modulation wave index of the lower bridge arm, n u_old 、nl_old ∈[0, 1], U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component, ω is the angular frequency of the power frequency, t is the time, θ1 is the initial phase angle of the fundamental frequency voltage of each phase, θ2 is the initial phase angle of the double frequency voltage of each phase, N is the number of submodules in each phase bridge arm, u c0 is the reference voltage of the capacitor in the submodule.

[0024] Based on the same inventive concept, the present invention also provides a transient impact smoothing control system for a flexible direct current system, the system comprising:

[0025] A modulation wave index determination unit, used to determine the modulation wave index of the upper and lower bridge arms of each phase in the converter based on the active power, reactive power, bridge arm current, circulating current and a preset power-circulating current control algorithm of the converter in the flexible DC system;

[0026] A modulation wave index correction unit, used to correct the modulation wave index of the upper and lower bridge arms of each phase in the converter based on the correction coefficient, so as to obtain the corrected modulation wave index of the upper and lower bridge arms of each phase in the converter;

[0027] The trigger signal generating unit is used to input the modified modulation wave index of the upper and lower bridge arms of each phase in the converter into the voltage modulation-voltage equalization algorithm to generate the final trigger signal of each submodule in the converter, so as to reduce the average operating voltage of the submodules in the converter.

[0028] Preferably, the method further comprises: a correction coefficient determination module, which is used to:

[0029] Determining a first correction parameter based on the number of submodules and the number of faulty submodules in each phase bridge arm;

[0030] Determine a second correction parameter based on a DC component, a fundamental frequency component amplitude, and a double frequency component amplitude in the converter output voltage, wherein the fundamental frequency component amplitude is the component amplitude in the converter output voltage whose frequency is equal to the fundamental frequency of the power grid, and the double frequency component amplitude is the component amplitude in the converter output voltage whose frequency is twice the fundamental frequency of the power grid;

[0031] The ratio of the first correction parameter to the second correction parameter is used as the correction coefficient.

[0032] Preferably, the determination of the first correction parameter satisfies the following formula:

[0033] C1=1-N f / N

[0034] Among them, C1 is the first correction parameter, N is the number of submodules in each phase bridge arm, and N fis the number of submodules with fault bypass in each phase bridge arm.

[0035] Preferably, the determination of the second correction parameter satisfies the following formula:

[0036]

[0037] Among them, C2 is the second correction parameter, U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component.

[0038] Preferably, the modulation wave index determination unit includes:

[0039] An output voltage component determination module, used to determine a DC component, a fundamental frequency component amplitude, and a double frequency component amplitude in the output voltage of the converter based on the active power, the reactive power, the bridge arm current, and the circulating current;

[0040] The modulation wave index determination module is used to determine the modulation wave index of the upper and lower bridge arms of each phase in the converter based on the DC component, the amplitude of the fundamental frequency component, the amplitude of the double frequency component and the preset power-circulation current control algorithm.

[0041] Preferably, the modulation wave index of the upper and lower bridge arms of each phase in the converter is determined to satisfy the following formula:

[0042]

[0043] Among them, n u_old is the modulation wave index of the upper bridge arm, n l_old is the modulation wave index of the lower bridge arm, n u_old 、n l_old ∈[0, 1], U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component, ω is the angular frequency of the power frequency, t is the time, θ1 is the initial phase angle of the fundamental frequency voltage of each phase, θ2 is the initial phase angle of the double frequency voltage of each phase, N is the number of submodules in each phase bridge arm, u c0 is the reference voltage of the capacitor in the submodule.

[0044] Based on the same inventive concept, the present invention also provides an electronic device, comprising: at least one processor and a memory; the memory and the processor are connected via a bus;

[0045] The memory is used to store one or more programs;

[0046] When the one or more programs are executed by the at least one processor, the transient impulse smoothing control method of the flexible direct current system described above is implemented.

[0047] Based on the same inventive concept, the present invention further provides a readable storage medium on which an execution program is stored. When the execution program is executed, the transient impulse smoothing control method of the flexible direct current system described above is implemented.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention provides a transient impact smoothing control method for a flexible DC system. The final trigger signal of each submodule in the converter is determined by the modified modulation wave index of the upper and lower bridge arms of each phase in the converter, so that the average operating voltage of the converter submodule is reduced. This can ensure that when a power transmission failure occurs in the converter, the surplus power in the converter is reduced, so that the energy-consuming device absorbs the surplus power to achieve the capacity requirement required for fault crossing, thereby reducing the overvoltage level of the flexible DC system, avoiding the formation of transient impacts in the flexible DC system, and helping to reduce the operating cost of the flexible DC system. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a schematic diagram of a flexible DC transmission system;

[0051] Figure 2 A topological structure diagram of a modular multi-level converter;

[0052] Figure 3 A flow chart of a transient impulse suppression control method for a flexible DC system provided by the present invention;

[0053] Figure 4 A schematic diagram of the modulation wave index before and after correction provided by the present invention;

[0054] Figure 5 A logic diagram of a transient impulse smoothing control method for a flexible DC system provided by the present invention;

[0055] Figure 6 A schematic diagram of voltage changes when a transmission failure occurs at the receiving end of a flexible direct current system provided by the present invention;

[0056] Figure 7 A schematic diagram for comparing changes in DC voltage of a flexible DC system provided by the present invention;

[0057] Figure 8 A schematic diagram comparing the effect of energy absorption by an energy dissipation device when crossing a fault provided by the present invention;

[0058] Fig. 9 A block diagram of a transient impulse suppression control system for a flexible direct current system provided by the present invention;

[0059] Fig.10 A schematic diagram of an electronic device provided by the present invention. DETAILED DESCRIPTION

[0060] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0061] Before describing the specific implementation of the present invention in detail, first, the application scenario of the present invention is described. The present invention is applicable to a flexible DC transmission control system, which may include a flexible DC transmission system. Figure 1 The present invention is a schematic diagram of a flexible direct current transmission system, which may include a first MMC (Modular Multilevel Converter), a second MMC, a first transformer, a second transformer, an AC energy consumption device and a DC energy consumption device. The input end of the first transformer may be used to connect a distributed power source (e.g., a fan), the output end of the first transformer may be connected to the AC end of the AC end of the first MMC and the AC energy consumption device, the DC end of the first MMC may be connected to the DC energy consumption device and the DC end of the second MMC, the AC end of the second MMC may be connected to the input end of the second transformer, and the output end of the second transformer may be used to connect to an AC power grid, wherein the topological structure of the first MMC and the second MMC is as follows: Figure 2 As shown, the first MMC and the second MMC include three-phase parallel MMC bridge arms, the midpoint of each phase MMC bridge arm serves as the AC side of the converter, used to connect the three-phase AC power, the connection point of the three-phase MMC bridge arm serves as the DC side of the converter, and each phase MMC bridge arm includes an upper bridge arm and a lower bridge arm connected in series, and the upper bridge arm and the lower bridge arm are connected by an inductor L VIt is composed of a plurality of SMs (Sub-modules) connected in series in sequence, wherein the SM includes a first IGBT tube T1, a second IGBT tube T2 and a capacitor C, the first IGBT tube T1 is connected in reverse parallel with the diode D1, the second IGBT tube T2 is connected in reverse parallel with the diode D2, the first IGBT tube T1 and the second IGBT tube T2 are connected in series to form an SM bridge arm, and the SM bridge arm is connected in parallel with the capacitor C. In a flexible DC transmission system, when a power transmission failure occurs in the receiving AC power grid, the wind farm cannot quickly reduce the output voltage due to the delay in detection, communication and response. The surplus power in the flexible DC system causes overvoltage in the flexible DC system within a few milliseconds to tens of milliseconds, and the wind farm is disconnected from the grid. In order to improve the ability of the flexible DC system to ride through power transmission failures, the current mainstream technical solution is to configure AC or DC energy consumption devices to dissipate the surplus power fed into the wind farm in the form of internal resistance heat energy. However, the parameter configurations of the AC and DC energy dissipation devices are all configured in accordance with the rated transmission power of the flexible DC system for 1 to 2 seconds. The cost of the energy dissipation device is directly related to the thermal capacity of its internal resistor, which is not conducive to reducing the operating cost of the flexible DC system.

[0062] In order to solve the above technical problems, the present invention provides a transient impulse smoothing control method for a flexible DC system, the method comprising: determining the modulation wave index of the upper and lower bridge arms of each phase in the converter based on the active power, reactive power, bridge arm current, circulating current and a preset power-circulating current control algorithm of the converter in the flexible DC system; based on a correction coefficient, correcting the modulation wave index of the upper and lower bridge arms of each phase in the converter to obtain the corrected modulation wave index of the upper and lower bridge arms of each phase in the converter; inputting the corrected modulation wave index of the upper and lower bridge arms of each phase in the converter into a voltage modulation-voltage equalization algorithm to generate a final trigger signal for each submodule in the converter, so as to reduce the average operating voltage of the submodules in the converter. The final trigger signal of each submodule in the converter is determined by the modified modulation wave index of the upper and lower bridge arms of each phase in the converter, so that the average operating voltage of the converter submodule is reduced. This can ensure that when a power transmission failure occurs in the converter, the surplus power in the converter is reduced, so that the capacity demand required for the energy-consuming device to absorb the surplus power to achieve fault crossing is reduced, thereby reducing the overvoltage level of the flexible DC system, avoiding transient shocks in the flexible DC system, and helping to reduce the operating cost of the flexible DC system.

[0063] Embodiment 1:

[0064] Figure 3 The present invention provides a flow chart of a transient impulse suppression control method for a flexible DC system. The transient impulse suppression control method for a flexible DC system may include the following steps:

[0065] In step 101, based on the active power, reactive power, bridge arm current, circulating current and a preset power-circulating current control algorithm of the converter in the flexible DC system, the modulation wave index of the upper and lower bridge arms of each phase in the converter is determined.

[0066] Possible implementation methods of this step may be: based on active power, reactive power, bridge arm current and circulating current, determine the DC component, fundamental frequency component amplitude and double frequency component amplitude in the converter output voltage; based on the DC component, fundamental frequency component amplitude, double frequency component amplitude and a preset power-circulating current control algorithm, determine the modulation wave index of the upper and lower bridge arms of each phase in the converter.

[0067] The modulation wave index of the upper and lower bridge arms of each phase in the converter in the above implementation manner is determined to satisfy the following formula:

[0068]

[0069] Among them, n u_old is the modulation wave index of the upper bridge arm, n l_old is the modulation wave index of the lower bridge arm, n u_old 、n l_old ∈[0, 1], U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component, ω is the angular frequency of the power frequency, t is the time, θ1 is the initial phase angle of the fundamental frequency voltage of each phase, θ2 is the initial phase angle of the double frequency voltage of each phase, N is the number of submodules in each phase bridge arm, u c0 is the reference voltage of the capacitor in the submodule.

[0070] It should be noted that the preset power-circulating current control algorithm can be implemented by a proportional-integral controller after ABC / dq three-phase coordinate transformation. The specific implementation method of the preset power-circulating current control algorithm is a common technical means in this field, and the present invention will not describe it in detail.

[0071] In step 102, based on the correction coefficient, the modulation wave index of the upper and lower bridge arms of each phase in the converter is corrected to obtain the corrected modulation wave index of the upper and lower bridge arms of each phase in the converter.

[0072] The process of determining the correction coefficient in this step may include the following steps:

[0073] Based on the number of submodules and the number of faulty submodules in each phase bridge arm, a first correction parameter is determined; based on the DC component, the amplitude of the fundamental frequency component and the amplitude of the double frequency component in the converter output voltage, a second correction parameter is determined, wherein the amplitude of the fundamental frequency component is the amplitude of the component in the converter output voltage with a frequency equal to the fundamental frequency of the power grid, and the amplitude of the double frequency component is the amplitude of the component in the converter output voltage with a frequency twice the fundamental frequency of the power grid; the ratio of the first correction parameter to the second correction parameter is used as a correction coefficient.

[0074] The determination of the first correction parameter satisfies the following formula:

[0075] C1=1-N f / N (1)

[0076] Among them, C1 is the first correction parameter, N is the number of submodules in each phase bridge arm, and N f is the number of submodules with fault bypass in each phase bridge arm.

[0077] The second correction parameter is determined to satisfy the following formula:

[0078]

[0079] Among them, C2 is the second correction parameter, U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component.

[0080] It should be noted that the value range of C1 is (0, 1). In general, C1 / C2>1 (i.e., the correction coefficient is greater than 1). The ratio of the first correction parameter C1 and the second correction parameter C2 calculated by formulas (1) and (2) is used as the correction coefficient. As shown in formula (3), the modulation wave index of the upper and lower bridge arms of each phase in the converter is multiplied by the correction coefficient to obtain the modified modulation wave index of the upper and lower bridge arms of each phase in the converter.

[0081]

[0082] Among them, n u_old is the modulation wave index of the upper bridge arm, n l_old is the modulation wave index of the lower bridge arm, n u_new is the modulated wave index after correction of the upper bridge arm, n l_new is the modulation wave index after correction of the lower bridge arm.

[0083] like Figure 4 As shown, Figure 4The schematic diagram of the modulation wave index before and after correction provided by the present invention, the modulation wave index after correction is greater than the modulation wave index after correction, that is, in the present invention, when the converter is in normal operation, the modulation wave index required to modulate the same reference voltage is greater, and more submodules need to be invested to generate the reference voltage, thereby reducing the average operating voltage of each submodule. When the converter has a power delivery failure, the converter input power is greater than the output power, and the surplus power accumulates inside the submodule capacitor to cause the voltage to rise. Since more submodules are invested, the initial voltage of the submodule is lower than the normal voltage, resulting in a reduction in the overvoltage level after the fault occurs, reducing the capacity requirement required for the energy-consuming device to absorb the surplus power to achieve fault crossing, thereby reducing the cost of the energy-consuming device.

[0084] In step 103, the modified modulation wave index of the upper and lower bridge arms of each phase in the converter is input into the voltage modulation-voltage equalization algorithm to generate the final trigger signal of each submodule in the converter, so as to reduce the average operating voltage of the submodules in the converter.

[0085] The final trigger signal may include an input signal or a bypass signal. The generated final trigger signal is sent to each submodule in the converter, and the submodule in the converter is controlled to be in an input state or a bypass state through the input signal or the bypass signal in the trigger signal. In the present invention, more submodules are put into the input state, thereby reducing the average operating voltage of the submodules in the converter.

[0086] It should be noted that the voltage modulation algorithm can adopt the nearest level modulation (NLM), and the voltage balancing algorithm can be implemented based on the current direction and capacitor voltage sorting. The implementation method of the voltage modulation-voltage balancing algorithm is a common technical means in this field, and the present invention will not go into details about it.

[0087] Figure 5 The logic diagram of the transient impulse suppression control method of a flexible DC system provided by the present invention is as follows: Figure 5 As shown, the DC component, fundamental frequency component amplitude and double frequency component amplitude in the converter output voltage are calculated through active power, reactive power, bridge arm current and circulating current. The DC component, fundamental frequency component amplitude and double frequency component amplitude are input into the preset power-circulating current control algorithm to obtain the modulation wave index (n) of the upper and lower bridge arms of each phase in the converter. u_old and n l_old ), the modulation wave index of each phase of the upper and lower bridge arms in the converter is multiplied by the correction coefficient (i.e. C1 / C2), and the modified modulation wave index of each phase of the upper and lower bridge arms in the converter is obtained (i.e. n u_new and n l_new), the modified modulation wave index of the upper and lower bridge arms of each phase in the converter is input into the voltage modulation-voltage equalization algorithm to generate the final trigger signal of each submodule in the converter, so that the average operating voltage of the submodule in the converter is reduced. The values ​​of C1, C2 and C1 / C2 are obtained by calculation, and the modulation wave index of the upper and lower bridge arms of each phase in the converter is corrected. The control strategy is simple and easy to implement, and no new hardware equipment is required. It can effectively reduce the average operating voltage of the submodule. When a power delivery failure occurs, the submodule in the converter absorbs more energy before overvoltage occurs, thereby delaying the start-up of the energy-consuming device and reducing the capacity demand and equipment cost of the energy-consuming device.

[0088] Figure 6 A schematic diagram of voltage changes when a transmission failure occurs at the receiving end of a flexible direct current system provided by the present invention. Figure 6 As shown, the horizontal axis is time and the vertical axis is the receiving end AC voltage U ac (pu (Per Unit) is the ratio of the actual value to the reference value). When the converter fails to send power (or the three-phase AC short circuit fault occurs at the receiving end of the converter), the external power supply continuously injects power into the converter through the receiving end of the converter, so that the DC voltage in the flexible DC system gradually increases. Figure 7 As shown, Figure 7 A schematic diagram showing the comparison of the change of the DC voltage of a flexible DC system provided by the present invention, where the horizontal axis is time and the vertical axis is the DC voltage U of the flexible DC system dc When the DC voltage reaches the starting threshold of the energy-consuming device, the energy-consuming device starts to dissipate the surplus power to make the system return to the rated power. Through the transient impact smoothing control method of the flexible DC system of the present invention, the average operating voltage of the converter submodule is reduced. Under the same surplus power support, the time lag of the flexible DC system reaching the overvoltage threshold is increased. During the fault ride-through period, the energy-consuming device absorbs energy such as Figure 8 As shown ( Figure 8 The horizontal axis is time, and the vertical axis is the energy E absorbed by the energy consuming device. The energy absorbed by the energy consuming device is reduced, thereby reducing the capacity demand and cost of the energy consuming device.

[0089] The present invention determines the final trigger signal of each submodule in the converter through the modified modulation wave index of the upper and lower bridge arms of each phase in the converter, so as to reduce the average operating voltage of the converter submodule. This can ensure that when a power transmission failure occurs in the converter, the surplus power in the converter is reduced, so that the capacity demand required for the energy-consuming device to absorb the surplus power to achieve fault crossing is reduced, the overvoltage level of the flexible DC system is reduced, and the formation of transient shocks in the flexible DC system is avoided, which is beneficial to reducing the operating cost of the flexible DC system.

[0090] Embodiment 2:

[0091] Based on the same inventive concept, the present invention also provides a transient impact smoothing control system for a flexible direct current system, such as Fig. 9 As shown, Fig. 9 The present invention provides a block diagram of a transient impulse suppression control system for a flexible direct current system. The transient impulse suppression control system for the flexible direct current system may include:

[0092] A modulation wave index determination unit, used to determine the modulation wave index of the upper and lower bridge arms of each phase in the converter based on the active power, reactive power, bridge arm current, circulating current and a preset power-circulating current control algorithm of the converter in the flexible DC system;

[0093] A modulation wave index correction unit, used to correct the modulation wave index of the upper and lower bridge arms of each phase in the converter based on the correction coefficient, so as to obtain the corrected modulation wave index of the upper and lower bridge arms of each phase in the converter;

[0094] The trigger signal generating unit is used to input the modified modulation wave index of the upper and lower bridge arms of each phase in the converter into the voltage modulation-voltage equalization algorithm to generate the final trigger signal of each submodule in the converter, so as to reduce the average operating voltage of the submodules in the converter.

[0095] Preferably, Fig. 9 For example, it also includes: a correction coefficient determination module, which is used to:

[0096] Determining a first correction parameter based on the number of submodules and the number of faulty submodules in each phase bridge arm;

[0097] Determine a second correction parameter based on a DC component, a fundamental frequency component amplitude, and a double frequency component amplitude in the converter output voltage, wherein the fundamental frequency component amplitude is the component amplitude in the converter output voltage whose frequency is equal to the fundamental frequency of the power grid, and the double frequency component amplitude is the component amplitude in the converter output voltage whose frequency is twice the fundamental frequency of the power grid;

[0098] The ratio of the first correction parameter to the second correction parameter is used as the correction coefficient.

[0099] Preferably, the determination of the first correction parameter satisfies the following formula:

[0100] C1=1-Nf / N

[0101] Among them, C1 is the first correction parameter, N is the number of submodules in each phase bridge arm, and N f is the number of submodules with fault bypass in each phase bridge arm.

[0102] Preferably, the determination of the second correction parameter satisfies the following formula:

[0103]

[0104] Among them, C2 is the second correction parameter, U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component.

[0105] Preferably, the modulation wave index determination unit includes:

[0106] An output voltage component determination module is used to determine the DC component, the amplitude of the fundamental frequency component and the amplitude of the double frequency component in the output voltage of the converter based on the active power, reactive power, bridge arm current and circulating current;

[0107] The modulation wave index determination module is used for the DC component, the amplitude of the fundamental frequency component, the amplitude of the double frequency component and the preset power-circulating current control algorithm to determine the modulation wave index of the upper and lower bridge arms of each phase in the converter.

[0108] Preferably, the modulation wave index of the upper and lower bridge arms of each phase in the converter is determined to satisfy the following formula:

[0109]

[0110] Among them, n u_old is the modulation wave index of the upper bridge arm, n l_old is the modulation wave index of the lower bridge arm, n u_old 、n l_old ∈[0, 1], U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component, ω is the angular frequency of the power frequency, t is the time, θ1 is the initial phase angle of the fundamental frequency voltage of each phase, θ2 is the initial phase angle of the double frequency voltage of each phase, N is the number of submodules in each phase bridge arm, u c0 is the reference voltage of the capacitor in the submodule.

[0111] Embodiment 3:

[0112] Based on the same inventive concept, the present invention also provides an electronic device, such as Fig.10 As shown, Fig.10 The schematic diagram of the electronic device provided by the present invention may be a computer device, a single-chip device, an intelligent mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, the processor and the transceiver component are connected via a bus; the memory may be used to store an execution program, and an exemplary execution program may include instructions; the processor is used to execute the instructions stored in the memory. The memory may also be used to store data, which may be called and / or modified when the instructions are executed.

[0113] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), or application-specific integrated circuits.

[0114] (Application Specific Integrated Circuit, ASIC), off-the-shelf programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in a readable storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of a transient impulse smoothing control method for a flexible direct current system shown in the above embodiment.

[0115] Embodiment 4:

[0116] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It can be understood that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of a transient impulse smoothing control method for a flexible direct current system in the above embodiment.

[0117] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0118] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0119] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0120] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0121] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A transient impulse smoothing control method for a flexible DC system, characterized in that: The method comprises: Based on the active power, reactive power, bridge arm current, circulating current and preset power-circulating current control algorithm of the converter in the flexible DC system, the modulation wave index of the upper and lower bridge arms of each phase in the converter is determined; Based on the correction coefficient, the modulation wave index of the upper and lower bridge arms of each phase in the converter is corrected to obtain the corrected modulation wave index of the upper and lower bridge arms of each phase in the converter; The modified modulation wave index of the upper and lower bridge arms of each phase in the converter is input into the voltage modulation-voltage equalization algorithm to generate the final trigger signal of each submodule in the converter, so as to reduce the average operating voltage of the submodules in the converter.

2. The method according to claim 1, characterized in that: The process of determining the correction coefficient includes: Determining a first correction parameter based on the number of submodules and the number of faulty submodules in each phase bridge arm; Determine a second correction parameter based on a DC component, a fundamental frequency component amplitude, and a double frequency component amplitude in the converter output voltage, wherein the fundamental frequency component amplitude is the component amplitude in the converter output voltage whose frequency is equal to the fundamental frequency of the power grid, and the double frequency component amplitude is the component amplitude in the converter output voltage whose frequency is twice the fundamental frequency of the power grid; The ratio of the first correction parameter to the second correction parameter is used as the correction coefficient.

3. The method according to claim 2, characterized in that The determination of the first correction parameter satisfies the following formula: C1=1-Nf / N Among them, C1 is the first correction parameter, N is the number of submodules in each phase bridge arm, and N f is the number of submodules with fault bypass in each phase bridge arm.

4. The method according to claim 2, characterized in that: The determination of the second correction parameter satisfies the following formula: Among them, C2 is the second correction parameter, U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component.

5. The method according to claim 1, characterized in that The method of determining the modulation wave index of the upper and lower bridge arms of each phase in the converter based on the active power, reactive power, bridge arm current, circulating current and a preset power-circulating current control algorithm of the converter in the flexible direct current system comprises: Determine the DC component, the amplitude of the fundamental frequency component and the amplitude of the double frequency component in the output voltage of the converter based on the active power, the reactive power, the bridge arm current and the circulating current; Based on the DC component, the amplitude of the fundamental frequency component, the amplitude of the double frequency component and the preset power-circulating current control algorithm, the modulation wave index of the upper and lower bridge arms of each phase in the converter is determined.

6. The method according to claim 5, characterized in that The modulation wave index of the upper and lower bridge arms of each phase in the converter is determined by the following formula: Among them, n u_old is the modulation wave index of the upper bridge arm, n l_old is the modulation wave index of the lower bridge arm, n u_old 、n l_old ∈[0, 1], U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component, ω is the angular frequency of the power frequency, t is the time, θ1 is the initial phase angle of the fundamental frequency voltage of phase A, θ2 is the initial phase angle of the double frequency voltage of phase A, N is the number of submodules in each phase bridge arm, u c0 is the reference voltage of the capacitor in the submodule.

7. A transient impact smoothing control system for a flexible direct current system, characterized in that: The system comprises: A modulation wave index determination unit, used to determine the modulation wave index of the upper and lower bridge arms of each phase in the converter based on the active power, reactive power, bridge arm current, circulating current and a preset power-circulating current control algorithm of the converter in the flexible DC system; A modulation wave index correction unit, used to correct the modulation wave index of the upper and lower bridge arms of each phase in the converter based on the correction coefficient, so as to obtain the corrected modulation wave index of the upper and lower bridge arms of each phase in the converter; The trigger signal generating unit is used to input the modified modulation wave index of the upper and lower bridge arms of each phase in the converter into the voltage modulation-voltage equalization algorithm to generate the final trigger signal of each submodule in the converter, so as to reduce the average operating voltage of the submodules in the converter.

8. The system according to claim 7, characterized in that Also includes: Correction factor determination module for: Determining a first correction parameter based on the number of submodules and the number of faulty submodules in each phase bridge arm; Determine a second correction parameter based on a DC component, a fundamental frequency component amplitude, and a double frequency component amplitude in the converter output voltage, wherein the fundamental frequency component amplitude is the component amplitude in the converter output voltage whose frequency is equal to the fundamental frequency of the power grid, and the double frequency component amplitude is the component amplitude in the converter output voltage whose frequency is twice the fundamental frequency of the power grid; The ratio of the first correction parameter to the second correction parameter is used as the correction coefficient.

9. The system according to claim 8, characterized in that The determination of the first correction parameter satisfies the following formula: C1=1-N f / N Among them, C1 is the first correction parameter, N is the number of submodules in each phase bridge arm, and N f is the number of submodules with fault bypass in each phase bridge arm.

10. The system according to claim 8, characterized in that The determination of the second correction parameter satisfies the following formula: Among them, C2 is the second correction parameter, U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component.

11. The system according to claim 7, characterized in that The modulation wave index determination unit comprises: An output voltage component determination module, used to determine a DC component, a fundamental frequency component amplitude, and a double frequency component amplitude in the output voltage of the converter based on the active power, the reactive power, the bridge arm current, and the circulating current; The modulation wave index determination module is used to determine the modulation wave index of the upper and lower bridge arms of each phase in the converter based on the DC component, the amplitude of the fundamental frequency component, the amplitude of the double frequency component and the preset power-circulation current control algorithm.

12. The system according to claim 11, characterized in that The modulation wave index of the upper and lower bridge arms of each phase in the converter is determined by the following formula: Among them, n u_old is the modulation wave index of the upper bridge arm, n l_old is the modulation wave index of the lower bridge arm, n u_old 、n l_old ∈[0, 1], U dc is the DC component, U ac1 is the amplitude of the fundamental frequency component, U ac2 is the amplitude of the double frequency component, ω is the angular frequency of the power frequency, t is the time, θ1 is the initial phase angle of the fundamental frequency voltage of each phase, θ2 is the initial phase angle of the double frequency voltage of each phase, N is the number of submodules in each phase bridge arm, u c0 is the reference voltage of the capacitor in the submodule.

13. An electronic device, characterized in that: include: at least one processor and memory; The memory and the processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, the transient impulse smoothing control method for a flexible direct current system according to any one of claims 1 to 6 is implemented.

14. A readable storage medium, characterized in that: An execution program is stored thereon, and when the execution program is executed, the transient impulse smoothing control method of the flexible direct current system according to any one of claims 1 to 6 is implemented.

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