Method for determining power flow control boundary of direct-current transformer with power flow control function

Abstract

According to the power flow control boundary determination method of the direct-current transformer with the power flow control function, any group of output power can be selected from the output power set as the target power, and the output end duty ratio of the power flow controller and the direct-current voltage output by the direct-current transformer are calculated according to the target power; calculating the phase shift duty ratio of the direct-current transformer according to the direct-current voltage when the power flow controller is in an uncontrolled state, and calculating the maximum regulation capability of the power flow controller under the target power according to the phase shift duty ratio; the method comprises the following steps of: acquiring the duty ratio of an output end of a power flow controller, calculating a current difference value of two direct-current buses in the power flow controller based on the duty ratio of the output end, comparing the current difference value with the maximum regulation capability to obtain a comparison result, and finally determining a power flow control boundary under the current working condition according to the comparison result. The power flow control boundary of the power flow controller is tested and calculated, the duty ratio of the output end is effectively controlled, and stable operation of the system is guaranteed.

Description

Technical Field

[0001] The present application relates to the technical field of high-voltage direct current transmission, and in particular to a method for determining a power flow control boundary of a direct current transformer with a power flow control function. Background Art

[0002] Compared with AC transmission, HVDC transmission has the characteristics of large transmission power capacity, low loss, long transmission distance, good stability, etc., and has broad application prospects. In the rectifier side and inverter side of the HVDC transmission system, power frequency transformers are still required to connect to the AC power grid, which are large in size and mass. DC transmission is still an auxiliary function of AC transmission and is not directly used for power equipment. In order to adapt to the direct application of HVDC transmission to power equipment, especially for large-scale non-grid-connected wind power generation and other independent power systems, the original plan is bulky and uneconomical. Therefore, a DC transformer with similar functions to AC isolation transformers is needed to convert high-voltage DC into isolated low-voltage DC that meets the requirements of power equipment.

[0003] At present, there are two basic types of DC converters, namely, DC-DC converters with output voltage regulation and "DC transformers" whose output voltage is adjusted according to the input. DC transformers are similar to AC transformers, converting one DC voltage into another or multiple DC voltages: through high-frequency chopping, transformer isolation, and high-frequency rectification, a DC voltage is converted into another or multiple DC voltages proportional to it, which can be used in power transmission and voltage detection.

[0004] With the development of high-power electronic components and their control technology, DC transformers with DC power flow controllers (DCPFC) have been developed, which can flexibly adjust the DC line power flow by changing the voltage. Figure 1 As shown, Figure 1 The schematic diagram of the topological structure of a DC transformer with a power flow controller provided in the prior art. The regulation principle of the DCPFC power flow is: the output terminal is connected to the output filter inductor and resistor, and the topological structure is as follows: Figure 2 As shown by Figure 2 It can be seen that the prior art can achieve power flow control of multiple lines by controlling the duty cycle of the output end. However, since the power flow controller has a limited ability to adjust the power flow distribution, controlling the duty cycle of the output end without knowing its limit can easily affect the stable operation of the system. Summary of the invention

[0005] The purpose of the present application is to solve at least one of the above-mentioned technical defects, especially the technical defect in the prior art that the output duty cycle is controlled without knowing the adjustment limit of the power flow controller on the power flow distribution, which is easy to affect the stable operation of the system.

[0006] The present application provides a method for determining a power flow control boundary of a DC transformer with a power flow control function, the method comprising:

[0007] Acquire an output power set of a power flow controller in a DC transformer, wherein the output power set includes multiple groups of output powers with different power values;

[0008] Selecting any set of output powers from the output power set as the target power, and calculating the output duty cycle of the power flow controller and the DC voltage output by the DC transformer according to the target power;

[0009] Calculating the phase shift duty ratio of the DC transformer when the power flow controller is in an uncontrolled state according to the DC voltage, and calculating the maximum regulation capability of the power flow controller at the target power according to the phase shift duty ratio;

[0010] Calculating a current difference between two DC buses in the power flow controller based on the output end duty cycle, and comparing the current difference with the maximum regulation capability to obtain a comparison result;

[0011] After determining the power flow control boundary under the current working condition according to the comparison result, continue to select other groups of output power from the output power set as the target power, and determine the power flow control boundary under the corresponding working condition, until the power flow control boundary under the corresponding working condition of all output powers in the output power set is determined.

[0012] Optionally, calculating the output duty cycle of the power flow controller according to the target power includes:

[0013] Calculating the output current of the power flow controller according to the target power;

[0014] Obtaining the capacitor voltage inside the power flow controller and the equivalent resistance at the output end;

[0015] The output duty cycle of the power flow controller is calculated according to the output current, the capacitor voltage and the equivalent resistance.

[0016] Optionally, calculating the DC voltage output by the DC transformer according to the target power includes:

[0017] Obtaining a high-voltage side DC voltage of the DC transformer;

[0018] The DC voltage output by the DC transformer is calculated according to the output end current, the capacitor voltage, the equivalent resistance, and the high-voltage side DC voltage.

[0019] Optionally, the calculating, according to the DC voltage, a phase shift duty cycle of the DC transformer when the power flow controller is in an uncontrolled state includes:

[0020] Obtaining the transmission power, the secondary side and the primary side DC voltages, the total equivalent inductance of the AC circuit, the transformation ratio of the isolation transformer, and the switching frequency of the switching device of the DC transformer when the power flow controller is in an uncontrolled state and the power is regulated only by the phase shift duty cycle;

[0021] The phase shift duty cycle of the DC transformer is calculated according to the transmission power of the DC transformer, the DC voltages on the secondary side and the primary side, the total equivalent inductance of the AC circuit, the transformation ratio of the isolation transformer, and the switching frequency of the switching device.

[0022] Optionally, calculating the maximum regulation capability of the power flow controller at the target power according to the phase shift duty cycle includes:

[0023] Determining an energy balance condition of the power flow controller according to the phase shift duty cycle;

[0024] Determine, according to the energy balance condition, the adjustment capacity boundary that the power flow controller can reach when the duty cycle of the input end of the power flow controller is 0 or 1;

[0025] According to the energy balance condition and the regulation capability boundary that the power flow controller can reach, the maximum regulation capability of the power flow controller under the target power is calculated.

[0026] Optionally, the calculating the current difference between two DC buses in the power flow controller based on the output end duty cycle includes:

[0027] Calculating the output current of the power flow controller according to the target power;

[0028] The current difference between two DC buses in the power flow controller is calculated according to the output terminal current and the output terminal duty cycle.

[0029] Optionally, determining the power flow control boundary under the current working condition according to the comparison result includes:

[0030] Determine the operating status of the system under the current working condition according to the comparison result;

[0031] The power flow control boundary under the current working condition is determined according to the operating conditions of the system.

[0032] The present application also provides a device for determining a power flow control boundary of a DC transformer with a power flow control function, comprising:

[0033] An output power acquisition module, used to acquire an output power set of a power flow controller in a DC transformer, wherein the output power set includes a plurality of groups of output powers with different power values;

[0034] A first calculation module, used for selecting any set of output powers from the output power set as the target power, and calculating the output duty cycle of the power flow controller and the DC voltage output by the DC transformer according to the target power;

[0035] a second calculation module, configured to calculate, according to the DC voltage, a phase-shift duty ratio of the DC transformer when the power flow controller is in an uncontrolled state, and to calculate, according to the phase-shift duty ratio, a maximum regulation capability of the power flow controller at the target power;

[0036] A third calculation module, configured to calculate a current difference between two DC buses in the power flow controller based on the output end duty cycle, and compare the current difference with the maximum regulation capability to obtain a comparison result;

[0037] The power flow control boundary determination module is used to determine the power flow control boundary under the current working condition according to the comparison result, continue to select other groups of output power from the output power set as the target power, and determine the power flow control boundary under the corresponding working condition until the power flow control boundary under the corresponding working condition of all the output powers in the output power set is determined.

[0038] The present application also provides a computer-readable storage medium, which stores computer-readable instructions. When the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the method for determining the power flow control boundary of a DC transformer with a power flow control function as described in any of the above embodiments.

[0039] The present application also provides a computer device, comprising: one or more processors, and a memory;

[0040] The memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the method for determining the power flow control boundary of a DC transformer with a power flow control function as described in any one of the above embodiments are performed.

[0041] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0042] The method for determining the power flow control boundary of a DC transformer with a power flow control function provided in the present application can first obtain an output power set of the power flow controller in the DC transformer, and the output power set includes multiple groups of output powers with different power values. Therefore, any group of output powers can be selected from the output power set as the target power, and the output duty cycle of the power flow controller and the DC voltage output by the DC transformer are calculated according to the target power; then the present application can calculate the phase shift duty cycle of the DC transformer when the power flow controller is in an uncontrolled state according to the DC voltage, and calculate the maximum adjustment capacity of the power flow controller under the target power according to the phase shift duty cycle; then based on the The output duty cycle calculates the current difference between the two DC bus bars in the power flow controller, and compares the current difference with the maximum regulation capacity to obtain a comparison result. Finally, the power flow control boundary under the current working condition can be determined based on the comparison result. Subsequently, the present application can continue to select other groups of output power from the output power set as the target power, and determine the power flow control boundary under the corresponding working condition until the power flow control boundary under the corresponding working condition of all output powers in the output power set is determined. In this way, the output duty cycle can be effectively controlled by traversing different working conditions, testing and calculating the power flow control boundary of the power flow controller, and stable operation of the system can be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0044] Figure 1 A schematic diagram of a topological structure of a DC transformer with a power flow controller provided in the prior art;

[0045] Figure 2 A schematic diagram of the topological structure of a power flow controller circuit after adding an output terminal provided by the prior art;

[0046] Figure 3 A flow chart of a method for determining a power flow boundary of a DC transformer with a power flow control function provided in an embodiment of the present application;

[0047] Figure 4 A schematic diagram of the structure of a power flow control boundary determination device for a DC transformer with a power flow control function provided in an embodiment of the present application;

[0048] Figure 5 A schematic diagram of the internal structure of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0050] In one embodiment, Figure 3 As shown, Figure 3 A flow chart of a method for determining a power flow boundary of a DC transformer with a power flow control function provided in an embodiment of the present application; the present application provides a method for determining a power flow control boundary of a DC transformer with a power flow control function, and the method may include:

[0051] S110: Obtain an output power set of a power flow controller in a DC transformer.

[0052] In this step, when determining the power flow control boundary of a DC transformer with power flow control function, the output power set of the power flow controller in the DC transformer can be obtained first. The output power set contains multiple groups of output powers with different power values, and each group of output power comes from the upper-level operator of the power system.

[0053] Among them, Figure 1 , 2 As shown, the flow controller of the present application mainly includes a flow control module A and a flow control module B. Therefore, the present application can pre-set the output power of the flow control module A and the flow control module B under different working conditions. The working condition type here mainly considers the forward and reverse power working conditions of the two flow control ports, and the per-unit value is [-1, 1]. The change of the working condition input parameter is mainly achieved by fixing the power of one port first and adjusting the power value of the other port.

[0054] S120: Select any set of output powers from the output power set as the target power, and calculate the output duty cycle of the power flow controller and the DC voltage output by the DC transformer according to the target power.

[0055] In this step, after obtaining the output power set of the power flow controller in the DC transformer through S110, since each group of output power corresponds to an operating condition, when traversing each group of output power in the output power set, the present application can first select any group of uncalculated output power from the output power set, and use it as the target power, and then calculate the output duty cycle of the power flow controller and the DC voltage output by the DC transformer according to the target power. In this way, the phase shift duty cycle of the DC transformer can be calculated according to the output duty cycle of the power flow controller and the DC voltage output by the DC transformer, and the maximum adjustment capability of the power flow controller under the current operating condition can be determined through the phase shift duty cycle.

[0056] S130: Calculating the phase shift duty ratio of the DC transformer when the power flow controller is in an uncontrolled state according to the DC voltage, and calculating the maximum regulation capability of the power flow controller at the target power according to the phase shift duty ratio.

[0057] In this step, after calculating the output duty cycle of the power flow controller and the DC voltage output by the DC transformer through S120, since the sum of the currents at each port is constant when the system is working stably, and when the power flow controller is in an uncontrolled state, the DC transformer still works normally, and the power can only be adjusted by the phase-shift duty cycle. Therefore, after the present application calculates the phase-shift duty cycle of the power flow controller when it is in an uncontrolled state through the DC voltage output by the DC transformer, the maximum adjustment capacity of the power flow controller at the target power can be calculated through the phase-shift duty cycle.

[0058] S140: Calculate the current difference between two DC buses in the power flow controller based on the output duty cycle, and compare the current difference with the maximum regulation capability to obtain a comparison result.

[0059] In this step, after calculating the maximum regulation capacity of the power flow controller under the target power through S130, the present application can also calculate the current difference between the two DC buses through the duty cycle of the output end of the power flow controller. The current difference indicates the current actual working condition of the power flow controller. Therefore, after comparing the current difference with its maximum regulation capacity, it can be determined whether the system is operating stably under the current working condition, and then determine the power flow control boundary under the current working condition.

[0060] S150: After determining the power flow control boundary under the current working condition according to the comparison result, continue to select other groups of output power from the output power set as the target power, and determine the power flow control boundary under the corresponding working condition until the power flow control boundary under the corresponding working condition of all output powers in the output power set is determined.

[0061] In this step, after the current difference is compared with the maximum regulation capacity through S140, the flow control boundary under the current operating condition can be determined based on the comparison result. Furthermore, in order to determine the flow control boundary of the flow controller under different operating conditions, the present application can continue to select other uncalculated output powers from the output power set as the target power, and use the above-mentioned calculation method of S120~S150 to determine the flow control boundary under the corresponding operating condition until all the output powers in the output power set are calculated. In this way, the flow control boundary under all operating conditions can be obtained.

[0062] In the above embodiment, first, an output power set of the power flow controller in the DC transformer can be obtained, and the output power set includes multiple groups of output powers with different power values. Therefore, any group of output powers can be selected from the output power set as the target power, and the output duty cycle of the power flow controller and the DC voltage output by the DC transformer can be calculated according to the target power; then, the present application can calculate the phase shift duty cycle of the DC transformer when the power flow controller is in an uncontrolled state according to the DC voltage, and calculate the maximum adjustment capacity of the power flow controller under the target power according to the phase shift duty cycle; then, the power flow controller is calculated based on the output duty cycle. The current difference between the two DC bus bars in the device is obtained, and the current difference is compared with the maximum regulation capacity to obtain a comparison result. Finally, the power flow control boundary under the current working condition can be determined according to the comparison result. Then, the application can continue to select other groups of output power from the output power set as the target power, and determine the power flow control boundary under the corresponding working condition until the power flow control boundary under the corresponding working condition of all output powers in the output power set is determined. In this way, the power flow control boundary of the power flow controller can be tested and calculated by traversing different working conditions, thereby effectively controlling the output duty cycle and ensuring stable operation of the system.

[0063] In one embodiment, calculating the output duty cycle of the power flow controller according to the target power in S120 may include:

[0064] S121: Calculate the output current of the power flow controller according to the target power.

[0065] S122: Obtain the capacitor voltage inside the power flow controller and the equivalent resistance at the output end.

[0066] S123: Calculate the output duty cycle of the power flow controller according to the output current, the capacitor voltage and the equivalent resistance.

[0067] In this embodiment, when calculating the output duty cycle of the power flow controller according to the target power, the output current of the power flow controller can be calculated according to the target power first, and then the capacitor voltage inside the power flow controller and the equivalent resistance of the output end are obtained. In this way, the output duty cycle of the power flow controller can be calculated based on the output current, capacitor voltage and equivalent resistance.

[0068] In a specific implementation, the present application can determine the calculation formula of the target power according to Kirchhoff's voltage law KVL equation after a set of working states is given, that is, after determining that the target powers of the power flow controller are P1 and P2 respectively:

[0069]

[0070] Where P1 is the output power of DC port 1 of the power flow controller, P2 is the output power of DC port 2 of the power flow controller, and U o1 is the voltage of DC port 1, I out1 is the current of DC port 1, U dc2 is the DC voltage on the high-voltage side of the current transformer. Considering the resistance of the DC line, R out1 is the equivalent resistance on DC bus 1, U CO is the capacitor voltage inside the power flow controller.

[0071] The output voltage and output current of the power flow controller can be solved from the above formula. The output duty cycle of the power flow controller can be calculated through the output voltage and output current. The specific formula is as follows:

[0072]

[0073] Among them, I out2 is the current of DC port 2, R out2 is the equivalent resistance on DC bus 2, d PFC_out is the duty cycle of the output of the power flow controller.

[0074] In one embodiment, calculating the DC voltage output by the DC transformer according to the target power in S120 may include:

[0075] S124: Obtaining a high-voltage side DC voltage of the DC transformer.

[0076] S125: Calculate the DC voltage output by the DC transformer according to the output end current, the capacitor voltage, the equivalent resistance, and the high-voltage side DC voltage.

[0077] In this embodiment, when calculating the DC voltage output by the DC transformer according to the target power, the output current of the power flow calculator can be calculated by the above embodiment first, and then the capacitor voltage inside the power flow controller, the equivalent resistance at the output end, and the DC voltage on the high-voltage side of the DC transformer can be obtained. In this way, the DC voltage output by the DC transformer can be calculated.

[0078] The DC transformer of the present application may be a MMDCT (Modular Multilevel DC-DC Transformer). For this type of DC transformer, the calculation formula for its DC voltage is as follows:

[0079]

[0080] Where U MMDC is the DC voltage of the DC transformer, d PFC_out1 is the duty cycle of the output of the power flow controller.

[0081] In one embodiment, calculating the phase shift duty ratio of the DC transformer when the power flow controller is in an uncontrolled state according to the DC voltage in S130 may include:

[0082] S131: Obtain the transmission power, secondary and primary DC voltages, total equivalent inductance of the AC circuit, transformation ratio of the isolation transformer, and switching frequency of the switching device of the DC transformer when the DC transformer is in an uncontrolled state and the power is regulated only by the phase shift duty cycle.

[0083] S132: Calculate the phase shift duty cycle of the DC transformer according to the transmission power of the DC transformer, the DC voltages on the secondary side and the primary side, the total equivalent inductance of the AC circuit, the transformation ratio of the isolation transformer, and the switching frequency of the switching device.

[0084] In this embodiment, when calculating the phase-shift duty cycle of the DC transformer, the transmission power, secondary and primary DC voltages, total equivalent inductance of the AC circuit, transformation ratio of the isolation transformer, and switching frequency of the switching device of the DC transformer when the power flow controller is in an uncontrolled state and the power is only adjusted by the phase-shift duty cycle can be obtained first. These are all known quantities and can be directly obtained. After obtaining the above-mentioned known quantities, they can be substituted into the transmission power calculation formula of the DC transformer to calculate its phase-shift duty cycle.

[0085] Therefore, when there is no embedded power flow controller, the MMDCT has a phase shift duty cycle of d DAB The transmission power at this time is:

[0086]

[0087] Where U p is the DC voltage on the secondary side of the DC transformer, U S is the DC voltage on the primary side of the DC transformer, L ac is the total equivalent inductance of the AC circuit, N is the ratio of the isolation transformer, f is the switching frequency of the switching device, and d DAB is the phase shift duty cycle, P MMDC is the transmission power of the DC transformer when the power flow controller is in an uncontrolled state (i.e., when the power flow controller is not embedded). In this application, when the imbalance of the upper and lower bridge arms is ignored, the DC voltage on the primary side of the DC transformer is , therefore, U MMDC Substituting this into the above formula, we can solve for the phase shift duty cycle of the DC transformer.

[0088] In one embodiment, calculating the maximum regulation capability of the power flow controller at the target power according to the phase shift duty cycle in S130 may include:

[0089] S133: Determine the energy balance condition of the power flow controller according to the phase shift duty cycle.

[0090] S134: Determine, according to the energy balance condition, the adjustment capability boundary that the power flow controller can reach when the duty cycle of the input end of the power flow controller is 0 or 1.

[0091] S135: Calculate the maximum regulation capability of the power flow controller at the target power according to the energy balance condition and the regulation capability boundary that the power flow controller can reach.

[0092] In this embodiment, when determining the maximum regulation capacity of the power flow controller based on the phase-shift duty cycle, the energy balance condition of the power flow controller can be determined based on the phase-shift duty cycle first, and then the energy balance condition can be used to determine the regulation capacity boundary that the power flow controller can reach when the duty cycle of the input end of the power flow controller is 0 or 1. In this way, the maximum regulation capacity of the power flow controller at the target power can be calculated.

[0093] Among them, when When , the energy balance condition of the power flow controller is:

[0094]

[0095] In the formula, I O1 is the current of DC bus 1, I O2 is the current of DC bus 2, I S is the DC current on the primary side of the DC transformer, d PFC_in is the duty cycle of the input end of the power flow controller. It should be noted that the main consideration here is the adjustment range of the power flow control module, and dDAB The analysis method when it is less than 0 is the same as that when it is greater than 0, so it will not be repeated. In addition, the forward or reverse power transmission characteristics of MMDC are rotationally symmetric, so there is no need to calculate the corresponding regulation capacity.

[0096] From the above formula, we can conclude that: PFC_in When it is 0 or 1, the power flow controller reaches the limit of regulation capacity. Substituting it into the above formula for calculation, the relationship of maximum regulation capacity can be obtained:

[0097]

[0098] In one embodiment, calculating the current difference between two DC buses in the power flow controller based on the output end duty cycle in S140 may include:

[0099] S141: Calculate the output current of the power flow controller according to the target power.

[0100] S142: Calculate a current difference between two DC buses in the power flow controller according to the output end current and the output end duty cycle.

[0101] In this embodiment, when calculating the current difference between the two DC buses in the power flow controller, the output current of the power flow controller can be calculated first. For the specific calculation process, please refer to the above embodiment, which will not be repeated here. After the output current of the power flow controller is obtained, the current difference between the two DC buses can be calculated according to the output current and the output duty cycle. The specific formula is as follows:

[0102]

[0103] In one embodiment, determining the power flow control boundary under the current working condition according to the comparison result in S150 may include:

[0104] S151: Determine the operating status of the system under the current working condition according to the comparison result.

[0105] S152: Determine the power flow control boundary under the current working condition according to the operating conditions of the system.

[0106] In this embodiment, under the premise of a given output power, the current difference between the two DC buses can be obtained through the calculation formula of the above embodiment. The current difference is the actual working condition of the power flow controller. At this time, it can be compared with the maximum regulation capability. If the current difference falls within the maximum regulation capability, it means that the system can operate stably, otherwise it cannot achieve stable operation.

[0107] When it is determined that the system is operating stably, it means that the power flow control boundary corresponding to the current maximum regulation capacity is feasible. When the system cannot operate stably, it means that the current power flow control boundary needs to be adjusted so that the actual current difference falls within the adjusted maximum regulation capacity range.

[0108] The following describes a device for determining a flow control boundary of a DC transformer with a flow control function provided in an embodiment of the present application. The device for determining a flow control boundary of a DC transformer with a flow control function described below and the method for determining a flow control boundary of a DC transformer with a flow control function described above can be referenced to each other.

[0109] In one embodiment, Figure 4 As shown, Figure 4 A schematic diagram of the structure of a power flow control boundary determination device for a DC transformer with a power flow control function provided in an embodiment of the present application; the present application also provides a power flow control boundary determination device for a DC transformer with a power flow control function, which may include an output power acquisition module 210, a first calculation module 220, a second calculation module 230, a third calculation module 240 and a power flow control boundary determination module 250, which are specifically as follows:

[0110] The output power acquisition module 210 is used to acquire an output power set of a power flow controller in a DC transformer, wherein the output power set includes a plurality of groups of output powers with different power values.

[0111] The first calculation module 220 is used to select any set of output powers from the output power set as the target power, and calculate the output duty cycle of the power flow controller and the DC voltage output by the DC transformer according to the target power.

[0112] The second calculation module 230 is used to calculate the phase shift duty ratio of the DC transformer when the power flow controller is in an uncontrolled state according to the DC voltage, and calculate the maximum regulation capability of the power flow controller under the target power according to the phase shift duty ratio.

[0113] The third calculation module 240 is used to calculate the current difference between two DC buses in the power flow controller based on the output end duty cycle, and compare the current difference with the maximum regulation capability to obtain a comparison result.

[0114] The flow control boundary determination module 250 is used to determine the flow control boundary under the current operating condition according to the comparison result, continue to select other groups of output power from the output power set as the target power, and determine the flow control boundary under the corresponding operating condition until the flow control boundary under the corresponding operating condition of all output powers in the output power set is determined.

[0115] In the above embodiment, first, an output power set of the power flow controller in the DC transformer can be obtained, and the output power set includes multiple groups of output powers with different power values. Therefore, any group of output powers can be selected from the output power set as the target power, and the output duty cycle of the power flow controller and the DC voltage output by the DC transformer can be calculated according to the target power; then, the present application can calculate the phase shift duty cycle of the DC transformer when the power flow controller is in an uncontrolled state according to the DC voltage, and calculate the maximum adjustment capacity of the power flow controller under the target power according to the phase shift duty cycle; then, the power flow controller is calculated based on the output duty cycle. The current difference between the two DC bus bars in the device is obtained, and the current difference is compared with the maximum regulation capacity to obtain a comparison result. Finally, the power flow control boundary under the current working condition can be determined according to the comparison result. Then, the application can continue to select other groups of output power from the output power set as the target power, and determine the power flow control boundary under the corresponding working condition until the power flow control boundary under the corresponding working condition of all output powers in the output power set is determined. In this way, the power flow control boundary of the power flow controller can be tested and calculated by traversing different working conditions, thereby effectively controlling the output duty cycle and ensuring stable operation of the system.

[0116] In one embodiment, the present application also provides a computer-readable storage medium, which stores computer-readable instructions. When the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the method for determining the flow control boundary of a DC transformer with a flow control function as described in any of the above embodiments.

[0117] In one embodiment, the present application also provides a computer device, including: one or more processors, and a memory.

[0118] The memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the method for determining the power flow control boundary of a DC transformer with a power flow control function as described in any one of the above embodiments are performed.

[0119] Indicatively, Figure 5 As shown, Figure 5 This is a schematic diagram of the internal structure of a computer device provided in an embodiment of the present application. The computer device 300 may be provided as a server. Figure 5The computer device 300 includes a processing component 302, which further includes one or more processors, and a memory resource represented by a memory 301, for storing instructions executable by the processing component 302, such as an application. The application stored in the memory 301 may include one or more modules, each corresponding to a set of instructions. In addition, the processing component 302 is configured to execute instructions to perform the power flow control boundary determination method of the DC transformer with power flow control function of any of the above embodiments.

[0120] The computer device 300 may further include a power supply component 303 configured to perform power management of the computer device 300, a wired or wireless network interface 304 configured to connect the computer device 300 to a network, and an input / output (I / O) interface 305. The computer device 300 may operate based on an operating system stored in the memory 301, such as Windows Server TM, Mac OS X TM, Unix TM, Linux TM, Free BSD TM, or the like.

[0121] Those skilled in the art will understand that Figure 5 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0122] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0123] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can refer to each other.

[0124] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining a power flow control boundary of a DC transformer with a power flow control function, characterized in that: The method comprises: Acquire an output power set of a power flow controller in a DC transformer, wherein the output power set includes multiple groups of output powers with different power values; Selecting any set of output powers from the output power set as the target power, and calculating the output duty cycle of the power flow controller and the DC voltage output by the DC transformer according to the target power; Calculating the phase shift duty ratio of the DC transformer when the power flow controller is in an uncontrolled state according to the DC voltage, and calculating the maximum regulation capability of the power flow controller under the target power according to the phase shift duty ratio; Calculating a current difference between two DC buses in the power flow controller based on the output end duty cycle, and comparing the current difference with the maximum regulation capability to obtain a comparison result; After determining the power flow control boundary under the current working condition according to the comparison result, continue to select other groups of output power from the output power set as the target power, and determine the power flow control boundary under the corresponding working condition, until the power flow control boundary under the corresponding working condition of all output powers in the output power set is determined.

2. The method for determining the power flow control boundary of a DC transformer with power flow control function according to claim 1, characterized in that: The calculating the output duty cycle of the power flow controller according to the target power includes: Calculating the output current of the power flow controller according to the target power; Obtaining the capacitor voltage inside the power flow controller and the equivalent resistance at the output end; The output duty cycle of the power flow controller is calculated according to the output current, the capacitor voltage and the equivalent resistance.

3. The method for determining the power flow control boundary of a DC transformer with power flow control function according to claim 2, characterized in that: The step of calculating the DC voltage output by the DC transformer according to the target power includes: Obtaining a high-voltage side DC voltage of the DC transformer; The DC voltage output by the DC transformer is calculated according to the output end current, the capacitor voltage, the equivalent resistance, and the high-voltage side DC voltage.

4. The method for determining the power flow control boundary of a DC transformer with power flow control function according to claim 1, characterized in that: The step of calculating the phase shift duty ratio of the DC transformer when the power flow controller is in an uncontrolled state according to the DC voltage includes: Obtaining the transmission power, the secondary side and the primary side DC voltages, the total equivalent inductance of the AC circuit, the transformation ratio of the isolation transformer, and the switching frequency of the switching device of the DC transformer when the power flow controller is in an uncontrolled state and the power is regulated only by the phase shift duty cycle; The phase shift duty cycle of the DC transformer is calculated according to the transmission power of the DC transformer, the DC voltages on the secondary side and the primary side, the total equivalent inductance of the AC circuit, the transformation ratio of the isolation transformer, and the switching frequency of the switching device.

5. The method for determining the power flow control boundary of a DC transformer with power flow control function according to claim 1, characterized in that: The calculating the maximum regulation capability of the power flow controller at the target power according to the phase shift duty cycle includes: Determining an energy balance condition of the power flow controller according to the phase shift duty cycle; Determine, according to the energy balance condition, the adjustment capacity boundary that the power flow controller can reach when the duty cycle of the input end of the power flow controller is 0 or 1; According to the energy balance condition and the regulation capability boundary that the power flow controller can reach, the maximum regulation capability of the power flow controller under the target power is calculated.

6. The method for determining the power flow control boundary of a DC transformer with power flow control function according to claim 1, characterized in that: The calculating the current difference between two DC buses in the power flow controller based on the output end duty cycle includes: Calculating the output current of the power flow controller according to the target power; The current difference between two DC buses in the power flow controller is calculated according to the output terminal current and the output terminal duty cycle.

7. The method for determining the power flow control boundary of a DC transformer with power flow control function according to any one of claims 1 to 6, characterized in that: Determining the power flow control boundary under the current working condition according to the comparison result includes: Determine the operating status of the system under the current working condition according to the comparison result; The power flow control boundary under the current working condition is determined according to the operating conditions of the system.

8. A device for determining a power flow control boundary of a DC transformer with a power flow control function, characterized in that: include: An output power acquisition module, used to acquire an output power set of a power flow controller in a DC transformer, wherein the output power set includes a plurality of groups of output powers with different power values; A first calculation module, used for selecting any set of output powers from the output power set as the target power, and calculating the output duty cycle of the power flow controller and the DC voltage output by the DC transformer according to the target power; a second calculation module, configured to calculate, according to the DC voltage, a phase-shift duty ratio of the DC transformer when the power flow controller is in an uncontrolled state, and to calculate, according to the phase-shift duty ratio, a maximum regulation capability of the power flow controller at the target power; A third calculation module, configured to calculate a current difference between two DC buses in the power flow controller based on the output end duty cycle, and compare the current difference with the maximum regulation capability to obtain a comparison result; The power flow control boundary determination module is used to determine the power flow control boundary under the current working condition according to the comparison result, continue to select other groups of output power from the output power set as the target power, and determine the power flow control boundary under the corresponding working condition until the power flow control boundary under the corresponding working condition of all the output powers in the output power set is determined.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-readable instructions, and when the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the method for determining the power flow control boundary of a DC transformer with a power flow control function as described in any one of claims 1 to 7.

10. A computer device, characterized in that: include: one or more processors, and memory; The memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the method for determining the power flow control boundary of a DC transformer with a power flow control function as described in any one of claims 1 to 7 are performed.

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