Collaborative optimization configuration method and system for parameters of current limiting device of direct-current power grid

Abstract

The invention discloses a collaborative optimization configuration method and system for parameters of a current limiting device of a direct-current power grid, and the method comprises the steps: obtaining an actual topological structure of the direct-current power grid, and building a numerical solving model of the direct-current power grid based on the actual topological structure; determining a lower limit and an upper limit of the value of the current limiting reactor based on the direct current power grid numerical solution model; initializing the value of the current-limiting reactor, and determining the reference value of the current-limiting reactor; calculating direct-current power grid fault current under different fault current limiter values under the current reference value of the current limiting reactor, and obtaining a fault current limiter configuration scheme when the direct-current power grid fault current is smaller than or equal to the maximum breaking current; selecting the configuration scheme with the lowest cost as an alternative scheme; updating the reference value of the current-limiting reactor, and judging whether the updated reference value of the current-limiting reactor is greater than the upper value limit of the current-limiting reactor or not; and if yes, selecting an optimal scheme from the alternative schemes based on the configuration requirement, and performing parameter configuration based on the optimal scheme.

Description

Technical Field

[0001] This invention relates to the field of flexible DC grid technology, and more specifically, to a method and system for collaborative optimization configuration of current limiting device parameters in a DC grid. Background Technology

[0002] With the large-scale integration of new energy power sources and their increasing application demands in various scenarios of new power systems, DC power grids, characterized by "low inertia," face severe challenges in short-circuit fault protection. Specifically, fault currents rise rapidly, have high amplitudes, and lack zero-crossing points, requiring relay protection and circuit breakers to interrupt high-amplitude DC currents of several kA or even tens of kA within hundreds of microseconds. This far exceeds the technical capabilities of existing relay protection and circuit breakers. Therefore, it is necessary to add fault current-limiting devices to restrict short-circuit fault currents.

[0003] Currently, commonly used fault current limiting devices in DC power grids include current limiting reactors (CLRs), fault current limiters (FCLs), and direct current circuit breakers (DCCBs). To ensure the DC power grid still has power transmission capacity after a fault occurs, DC circuit breakers should be installed on both sides of the line; when a fault occurs, the faulty line is disconnected, ensuring the normal operation of the non-faulty parts of the grid. However, relying solely on DC circuit breakers to interrupt fault current leads to excessively large opening capacities and high costs. Generally, current limiting reactors and fault current limiters are added to suppress fault current and reduce the cost of DC circuit breakers.

[0004] In current engineering projects, the differences in parameters such as converter stations and transmission lines are generally not considered. A simple average allocation strategy is often adopted. At the same time, the parameter configuration of current-limiting reactors and fault current limiters are generally considered separately, without considering the coordinated design and optimization of the parameters of the two current-limiting devices. This also means that there is still room for optimization in the total cost of current-limiting devices in the current DC power grid.

[0005] To reduce the cost of protection equipment while ensuring the reliability of DC power grid operation, it is necessary to study the coordinated optimization configuration of various fault current limiting devices. Currently, using existing electromagnetic transient simulations to obtain short-circuit current characteristics for the coordinated design of DC power grid fault current limiting device parameters is slow and inefficient. Therefore, a method for coordinated optimization configuration of current limiting device parameters is needed. Summary of the Invention

[0006] This invention proposes a method and system for collaborative optimization configuration of current limiting device parameters in DC power grids, in order to solve the problem of how to collaboratively optimize the configuration of current limiting device parameters in DC power grids.

[0007] To address the aforementioned problems, according to one aspect of the present invention, a method for collaborative optimization configuration of current-limiting device parameters in a DC power grid is provided, the method comprising:

[0008] Step 1: Obtain the actual topology of the DC power grid and establish a numerical solution model of the DC power grid based on the actual topology.

[0009] Step 2: Based on the numerical solution model of the DC power grid, calculate the fault current of the DC power grid under different current-limiting reactor values, determine the upper limit of the fault current according to the lower limit of the converter station blocking current, select the current-limiting reactor value corresponding to the upper limit of the fault current as the lower limit of the current-limiting reactor value, and determine the upper limit of the current-limiting reactor value according to the dynamic performance requirements of the power grid.

[0010] Step 3: Determine the maximum breaking current of the DC circuit breaker, initialize the value of the current limiting reactor based on the lower limit of the current limiting reactor value, and determine the reference value of the current limiting reactor.

[0011] Step 4: Based on the DC grid numerical solution model, calculate the DC grid fault current under different fault current limiter values ​​under the current limiting reactor reference value, and obtain the fault current limiter configuration scheme when the DC grid fault current is less than or equal to the maximum breaking current.

[0012] Step 5: Calculate the cost of different configuration options and select the configuration option with the lowest cost as the alternative.

[0013] Step 6: Increase the current-limiting reactor reference value according to the preset step size, update the current-limiting reactor reference value, and determine whether the updated current-limiting reactor reference value is greater than the upper limit of the current-limiting reactor value. If so, proceed to step 7; otherwise, proceed to step 4 to recalculate.

[0014] Step 7: Select the optimal solution from the alternatives based on the configuration requirements, and configure the parameters based on the optimal solution.

[0015] Preferably, the establishment of a numerical solution model for the DC power grid based on the actual topology includes:

[0016] Based on the actual topology, the converter, transmission line, DC current limiting device, and fault branch are all equivalent to RLC branches, and the current equations of each mesh are written based on the mesh node current method to construct a numerical solution model for the DC power grid.

[0017] Preferably, in the equivalent case, the capacitor parameters of the converter are determined based on the equivalent capacitance correction model; the transmission line uses a lumped parameter model; the current-limiting reactor corresponding to each converter station is simplified to a single value, and the fault current limiter is simplified to a single value; the DC current limiting device is equivalent to an equivalent circuit model that varies with time based on the operating time; for the fault branch, when an inter-pole short-circuit fault occurs, the fault branch is equivalent to a resistor connected between the two fault poles, and each converter station corresponds to one fault point.

[0018] Preferably, the fault current limiter value is an integer multiple of 5mH; the reference value of the current limiting reactor value is an integer multiple of 10mH.

[0019] According to another aspect of the present invention, a collaborative optimization configuration system for current limiting device parameters in a DC power grid is provided, the system comprising:

[0020] The model building unit is used to obtain the actual topology of the DC power grid and establish a numerical solution model of the DC power grid based on the actual topology.

[0021] The current-limiting reactor value determination unit is used to calculate the fault current of the DC power grid under different current-limiting reactor values ​​based on the numerical solution model of the DC power grid, determine the upper limit of the fault current according to the lower limit of the converter station blocking current, select the current-limiting reactor value corresponding to the upper limit of the fault current as the lower limit of the current-limiting reactor value, and determine the upper limit of the current-limiting reactor value according to the dynamic performance requirements of the power grid.

[0022] An initialization unit is used to determine the maximum breaking current of the DC circuit breaker, initialize the value of the current-limiting reactor based on the lower limit of the current-limiting reactor value, and determine the reference value of the current-limiting reactor.

[0023] The configuration scheme determination unit is used to calculate the DC grid fault current under different fault current limiter values ​​under the current current limiting reactor reference value based on the DC grid numerical solution model, and to obtain the fault current limiter configuration scheme when the DC grid fault current is less than or equal to the maximum breaking current.

[0024] The alternative solution determination unit is used to calculate the cost of different configuration options and select the configuration option with the lowest cost as the alternative solution.

[0025] The update unit is used to increase the reference value of the current-limiting reactor according to a preset step size, update the reference value of the current-limiting reactor, and determine whether the updated reference value of the current-limiting reactor is greater than the upper limit of the current-limiting reactor value. If it is, the configuration unit is entered; otherwise, the configuration scheme determination unit is entered to recalculate.

[0026] The configuration unit is used to select the optimal solution from the alternatives based on configuration requirements, and to configure the parameters based on the optimal solution.

[0027] Preferably, the model building unit establishes a numerical solution model for the DC power grid based on the actual topology, comprising:

[0028] Based on the actual topology, the converter, transmission line, DC current limiting device, and fault branch are all equivalent to RLC branches, and the current equations of each mesh are written based on the mesh node current method to construct a numerical solution model for the DC power grid.

[0029] Preferably, the model building unit is further used for:

[0030] In the equivalent phase, the capacitor parameters of the converter are determined based on the equivalent capacitance correction model; the transmission line uses a lumped parameter model; the current-limiting reactor corresponding to each converter station is simplified to a single value, and the fault current limiter is simplified to a single value; the DC current limiting device is equivalent to an equivalent circuit model that varies with time based on the operating time; for the fault branch, when an inter-pole short-circuit fault occurs, the fault branch is equivalent to a resistor connected between the two fault poles, and each converter station corresponds to one fault point.

[0031] Preferably, the fault current limiter value is an integer multiple of 5mH; the reference value of the current limiting reactor value is an integer multiple of 10mH.

[0032] Based on another aspect of the present invention, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any one of the steps in a method for coordinated optimization configuration of current limiting device parameters in a DC power grid.

[0033] According to another aspect of the present invention, the present invention provides an electronic device, comprising:

[0034] The aforementioned computer-readable storage medium; and

[0035] One or more processors for executing a program in the computer-readable storage medium.

[0036] This invention provides a method and system for collaborative optimization configuration of current-limiting device parameters in a DC power grid, comprising: Step 1, obtaining the actual topology of the DC power grid and establishing a numerical solution model of the DC power grid based on the actual topology; Step 2, based on the numerical solution model of the DC power grid, calculating the fault current of the DC power grid under different current-limiting reactor values, determining the upper limit of the fault current according to the lower limit of the converter station blocking current, selecting the current-limiting reactor value corresponding to the upper limit of the fault current as the lower limit of the current-limiting reactor value, and determining the upper limit of the current-limiting reactor value according to the dynamic performance requirements of the power grid; Step 3, determining the maximum breaking current of the DC circuit breaker, initializing the current-limiting reactor value based on the lower limit of the current-limiting reactor value, and determining the current-limiting reactor reference. Step 4: Based on the numerical solution model of the DC power grid, calculate the DC power grid fault current under different fault current limiter values ​​under the current limiting reactor reference value, and obtain the fault current limiter configuration scheme when the DC power grid fault current is less than or equal to the maximum breaking current; Step 5: Calculate the cost of different configuration schemes, and select the configuration scheme with the lowest cost as the alternative scheme; Step 6: Increase the current limiting reactor reference value according to the preset step size, update the current limiting reactor reference value, and determine whether the updated current limiting reactor reference value is greater than the upper limit of the current limiting reactor value. If so, proceed to Step 7; otherwise, proceed to Step 4 to recalculate; Step 7: Select the optimal scheme from the alternative schemes based on the configuration requirements, and configure the parameters based on the optimal scheme. This invention, by considering the coordinated operation of different current limiting devices, selects the configuration scheme with the lowest total cost of current limiting reactor, fault current limiter and DC circuit breaker as the optimal configuration scheme for DC grid current limiting devices under the premise of ensuring the reliability of DC grid operation, thereby reducing the cost of protection equipment; it has a certain degree of versatility and can be applied to the configuration of different types of fault current limiting devices under different DC grid topologies; the coordinated optimization configuration method is simple to implement and easy to expand and promote. Attached Figure Description

[0037] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0038] Figure 1 A flowchart of a current limiting device parameter collaborative optimization configuration 100 for a DC power grid according to an embodiment of the present invention;

[0039] Figure 2 A flowchart illustrating the calculation process of a collaborative optimization configuration method for current limiting device parameters in a DC power grid according to an embodiment of the present invention.

[0040] Figure 3 This is a simulation example of a power grid topology according to an embodiment of the present invention;

[0041] Figure 4This is a schematic diagram of the overall equivalent circuit model of a DC power grid according to an embodiment of the present invention;

[0042] Figure 5 This is an equivalent circuit diagram of a converter valve according to an embodiment of the present invention;

[0043] Figure 6 This is a schematic diagram of a current limiter topology according to an embodiment of the present invention;

[0044] Figure 7 This is an equivalent circuit diagram of a faulty branch according to an embodiment of the present invention;

[0045] Figure 8 This is a schematic diagram of the structure of a DC power grid current limiting device parameter collaborative optimization configuration system 800 according to an embodiment of the present invention. Detailed Implementation

[0046] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0047] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0048] Figure 1 A flowchart illustrating the collaborative optimization configuration 100 of current limiting device parameters for a DC power grid according to an embodiment of the present invention. Figure 1 As shown, the method for collaborative optimization configuration of current limiting device parameters in a DC power grid provided by this invention considers the collaborative operation of different current limiting devices. Under the premise of ensuring the reliability of DC power grid operation, it selects the configuration scheme with the lowest total cost of current limiting reactors, fault current limiters, and DC circuit breakers as the optimal configuration scheme for DC power grid current limiting devices, thus reducing the cost of protection equipment. It has a certain degree of versatility and can be applied to different types of fault current limiting device configurations under different DC power grid topologies. The collaborative optimization configuration method is simple to implement and easy to expand and promote. The method 100 for collaborative optimization configuration of current limiting device parameters in a DC power grid provided by this invention starts from step 101. In step 101, the actual topology of the DC power grid is obtained, and a numerical solution model of the DC power grid is established based on the actual topology.

[0049] Preferably, the establishment of a numerical solution model for the DC power grid based on the actual topology includes:

[0050] Based on the actual topology, the converter, transmission line, DC current limiting device, and fault branch are all equivalent to RLC branches, and the current equations of each mesh are written based on the mesh node current method to construct a numerical solution model for the DC power grid.

[0051] Preferably, in the equivalent case, the capacitor parameters of the converter are determined based on the equivalent capacitance correction model; the transmission line uses a lumped parameter model; the current-limiting reactor corresponding to each converter station is simplified to a single value, and the fault current limiter is simplified to a single value; the DC current limiting device is equivalent to an equivalent circuit model that varies with time based on the operating time; for the fault branch, when an inter-pole short-circuit fault occurs, the fault branch is equivalent to a resistor connected between the two fault poles, and each converter station corresponds to one fault point.

[0052] In this invention, firstly, based on the actual topology of the DC power grid, the converter, transmission line, DC current limiting device, and fault branch are all equivalent to RLC branches, and the current equations of each mesh are written using the mesh node current method to establish a numerical solution model for the DC power grid.

[0053] In the equivalent process, the converter is equivalent to an RLC series branch, and the converter's capacitance parameters are determined using an equivalent capacitance correction model. A lumped parameter model is used for the transmission line. Since the equivalent capacitance values ​​of the line parameters are much smaller than those of the converter valves, the calculation error after line equivalence is within 5%. For ease of calculation, due to the topological symmetry of each converter station, the current-limiting reactor corresponding to each converter station is simplified to a single value, and the fault current limiter is also simplified to a single value. When equivalencing the DC current limiting device, its operating time should be considered, and it should be equivalent to a time-varying equivalent circuit model. The fault branch here only considers the most severe fault scenario, i.e., an inter-pole short-circuit fault in the DC grid. In the event of an inter-pole short-circuit fault, the fault branch is equivalent to a small resistor connected between the two faulty poles. Each converter station corresponds to one fault point.

[0054] In step 102, based on the numerical solution model of the DC power grid, the fault current of the DC power grid under different current-limiting reactor values ​​is calculated. The upper limit of the fault current is determined according to the lower limit of the converter station blocking current. The current-limiting reactor value corresponding to the upper limit of the fault current is selected as the lower limit of the current-limiting reactor value. The upper limit of the current-limiting reactor value is determined according to the dynamic performance requirements of the power grid.

[0055] Combination Figure 2As shown, in this invention, without considering the fault current limiter, the value of the current-limiting reactor is modified, and an approximate numerical solution for the fault current in the DC grid under different current-limiting reactor values ​​is calculated based on the constructed DC grid numerical solution model. Then, according to the DC grid parameters, a lower limit for the converter station blocking current is set, and the current-limiting reactor value corresponding to the fault current in the DC grid being the lower limit of the converter station blocking current is selected as the lower limit for the current-limiting reactor value. Furthermore, an upper limit for the current-limiting reactor value is determined based on the dynamic performance requirements of the grid. Finally, the reference range for the current-limiting reactor value in the current-limiting design scheme is determined based on the lower and upper limits of the current-limiting reactor value.

[0056] In step 103, the maximum breaking current of the DC circuit breaker is determined, the value of the current limiting reactor is initialized based on the lower limit of the current limiting reactor value, and the reference value of the current limiting reactor is determined.

[0057] In step 104, based on the DC grid numerical solution model, the DC grid fault current is calculated under the current current limiting reactor reference value and different fault current limiter values, and the fault current limiter configuration scheme when the DC grid fault current is less than or equal to the maximum breaking current is obtained.

[0058] In step 105, the cost of different configuration schemes is calculated, and the configuration scheme with the lowest cost is selected as the alternative scheme.

[0059] Combination Figure 2 As shown, in this invention, the maximum breaking current of the DC circuit breaker is determined based on the breaking capacity and cost requirements of existing DC circuit breakers. The value L of the current-limiting reactor is determined based on the lower limit of the current-limiting reactor value. CLR This serves as a benchmark value. Based on this benchmark value, the parameters L for the fault current limiter within the power grid are then designed. FCL Set the boundary condition to the maximum breaking current of the DC circuit breaker, and calculate the DC grid fault current under different fault current limiter parameters according to the DC grid numerical solution model in step 101. Obtain the DC grid fault current limiter parameter configuration scheme that makes the fault current no greater than the maximum breaking current of the DC circuit breaker. Then compare the costs of the different fault current limiter parameter configuration schemes obtained, and select the configuration scheme with lower cost as the alternative scheme.

[0060] In this invention, in order to better fit actual engineering conditions and reduce the complexity of equipment manufacturing, the current limiting inductor in the fault current limiter is an integer multiple of 5mH, and the current limiting reactor is an integer multiple of 10mH.

[0061] In step 106, the reference value of the current limiting reactor is increased by a preset step size, the reference value of the current limiting reactor is updated, and it is determined whether the updated reference value of the current limiting reactor is greater than the upper limit of the current limiting reactor value. If it is, proceed to step 107; otherwise, proceed to step 104 to recalculate.

[0062] In step 107, the optimal solution is selected from the alternative solutions based on the configuration requirements, and the parameters are configured based on the optimal solution.

[0063] Preferably, the fault current limiter value is an integer multiple of 5mH; the reference value of the current limiting reactor value is an integer multiple of 10mH.

[0064] Combination Figure 2 As shown, in this invention, according to L CLR =L CLR The value of the current-limiting reactor is increased by +10mH in a fixed step size. It is then determined whether the updated baseline value of the current-limiting reactor is greater than the upper limit of the current-limiting reactor value. If yes, proceed to step 107; otherwise, return to step 104 and repeat the calculation to obtain fault current limiter parameter configuration schemes under different current-limiting reactor values. Finally, based on overall current-limiting performance, operating costs, and other configuration requirements, one parameter configuration scheme is selected as the optimal scheme from the alternative schemes under different current-limiting reactor parameters, and parameter configuration is performed based on the optimal scheme.

[0065] The method of this invention is applicable to the coordinated optimization configuration of current limiting device parameters in DC power grids, and its main advantages are:

[0066] 1. By considering the coordinated operation of different current limiting devices, this invention selects the configuration scheme with the lowest total cost of current limiting reactor, fault current limiter and DC circuit breaker as the optimal configuration scheme of DC grid current limiting device under the premise of ensuring the reliability of DC grid operation, thereby reducing the cost of protection equipment.

[0067] 2. In the calculation process, the method of the present invention establishes a numerical model of the DC power grid, quickly calculates the fault current inside the DC power grid, and obtains the corresponding fault current level under different values ​​of the current limiting device. Based on this, the parameters of the current limiting device are optimized and configured, resulting in high calculation efficiency.

[0068] 3. The method of the present invention has a certain degree of versatility and can be applied to different types of fault current limiting device configurations under different DC grid topologies.

[0069] 4. The method for collaborative optimization configuration of current limiting device parameters proposed in this invention is simple to implement and easy to expand and promote.

[0070] The following specific examples illustrate the embodiments of the present invention.

[0071] In an embodiment of the present invention, the step of collaboratively optimizing the parameters of the current limiting device of the DC power grid within a certain time period includes:

[0072] Step 1: Input DC grid parameters. Based on the actual topology of the DC grid, the converter, transmission line, DC current limiting device, and fault branch are all equivalent to RLC branches. Using the mesh node current method, write the current equations for each mesh and establish a numerical solution model for the DC grid.

[0073] The power grid structure in this example is as follows: Figure 3 As shown, the system consists of four overhead DC transmission lines, interconnected by metal return lines mounted on the same pole. DC circuit breakers are used to quickly clear line faults and isolate faulty poles; the circuit breakers operate within 5ms. The metal return lines are grounded at converter station 4 via a 15Ω resistor. Key simulation parameters are shown in Table 1.

[0074] Table 1 Key parameters of each converter station in the system

[0075] Converter Station 1 Converter Station 2 Converter Station 3 Converter Station 4 Submodule capacitance value (mF) 15 8 8 15 Bridge arm reactance (mH) 50 100 100 50 Transformer rated capacity (MVA) 1700 850 850 1700 Transformer turns ratio (kV) 230 / 291 230 / 291 525 / 291 525 / 291 Pole-line current-limiting reactor (mH) 150 150 150 150 Neutral current-limiting reactor (mH) 300 300 300 300

[0076] For the power grid structure in this example, a total of 8 fault points are set. For each different fault point, the DC power grid is simplified. The equivalent circuit model of the DC power grid fault corresponding to each fault point is as follows: Figure 4 As shown. Each specific part is equivalent to the following description.

[0077] Without the converter being locked out, the modular multilevel converter (Modular) can be used.

[0078] Multilevel Converter (MMC) is simplified to Figure 5 The structure shown is as follows. Where:

[0079]

[0080] In the formula, N SM r and r are the total number of capacitors in a bridge arm and the on-resistance of the switching device, respectively; C0 is the capacitance of a single bridge arm capacitor; R0 and L0 are the resistance and inductance of a bridge arm, respectively; ε is the equivalent capacitance parameter.

[0081]

[0082] m represents the modulation ratio. Depending on the actual situation, the value of the modulation ratio can be selected, thereby calculating ε as the equivalent parameter of the capacitor.

[0083] The transmission line uses a lumped parameter model. Since the equivalent capacitance value of the line parameters is much smaller than the equivalent capacitance value of the converter valve, the calculation error after the line is equivalent is within 5%.

[0084] When a DC current limiting device is equivalent, it should be considered as an equivalent circuit model that varies with time, based on its operating time.

[0085] by Figure 6 Taking the DC current limiting device with the structure shown as an example, we analyze the specific equivalent circuit model of the DC current limiting device. In the figure, D1, D2, D3, and D4 are diodes, G1 is a solid-state switching device, mov is a surge arrester, RS is a buffer resistor, and Cs is a buffer capacitor.

[0086] When the current limiting device is not activated, G1 is in the open state and can be equivalent to a small resistor.

[0087] After the fault occurs, during the initial shutdown phase of G1, the DC current limiting device is equivalent to L. FCL

[0088] After G1 is turned off for a period of time, the voltage across the current limiting device is greater than the reference voltage of the surge arrester. At this time, the current is transferred to the surge arrester branch, and the DC current limiting device is equivalent to a single surge arrester.

[0089] A faulty branch can be equivalent to a fault resistor of different resistance values ​​depending on the actual fault situation. After the equivalence is completed, the different components after equivalence are combined to form the fault.

[0090] In the event of an inter-pole short-circuit fault, an equivalent circuit of the DC power grid is established between the two faulty poles after the short-circuit fault occurs. For example... Figure 7 As shown.

[0091] according to Figure 4 The equivalent circuit model shown is used to write the current equations for each mesh using the mesh node current method, and then organize them to form a set of differential equations for the entire network.

[0092] It can be represented as

[0093]

[0094] In the formula, L is the inductance matrix, R is the resistance matrix, C is the capacitance matrix, and U... FCL This is the voltage matrix across the current limiting device. It can be represented as:

[0095]

[0096] In the formula, R g The on-state impedance of the current limiting device is generally negligible, C. FCL For the buffer branch capacitor, u movThe voltage across the surge arrester in the energy-absorbing branch needs to be determined based on the characteristics of the MOV (Medium-Voltage Transformer) and its corresponding VA (Voltage Amplifier) ​​characteristic curve. The settings are then configured according to this curve. t0 is the time when the current-limiting device switches off, and t1 is the time when the current is completely transferred to the energy-absorbing branch. In this algorithm, to facilitate calculation and improve efficiency, the current is considered to have completely transferred to the energy-absorbing branch when the voltage of the buffer branch is equal to the residual voltage of the surge arrester in the energy-absorbing branch.

[0097] i = [i a (t),i1(t),i b (t),i R1 (t)] T Let u be the line current vector, u = [u a (t),u1(t),u b (t),u R1 (t)] T U is the voltage vector of the equivalent capacitance of the converter station. s and I s These are the second-nearest steady-state input vectors, respectively. Represented as...

[0098]

[0099] The system of equations can be rearranged into the form dx = AX + B, where A is the circuit parameter matrix of the DC power grid, B is the steady-state excitation matrix of the DC power grid, X is the state parameter matrix to be determined, and dx represents the differential matrix of X. In the equation, X = [i, u] T Matrix A and B are shown below.

[0100]

[0101] The differential equations were then solved using the 4th-order 5th-level Runge-Kutta method in MATLAB, where matrix A is a time-varying matrix.

[0102] Step 2: Without considering the fault current limiter, modify the value of the current-limiting reactor and use the fault current calculation method described in Step 1 to calculate the approximate numerical solution of the fault current in the DC grid under different current-limiting reactor values. The value of the current-limiting reactor is reflected in the L matrix of Equation (1). Based on the DC grid parameters, set the lower limit of the converter station blocking current, and constrain the lower limit of the current-limiting reactor value accordingly. Based on the dynamic performance requirements of the grid, set the upper limit of the current-limiting reactor value. Use this as the reference range for the current-limiting reactor value in the current-limiting design scheme.

[0103] In this example, the maximum allowable current of the converter arm is set to 6kA. Through calculation, the lower limit of the current-limiting reactor value is set to 100mH. Since an excessively large reactor value can lead to system instability, in order not to affect the dynamic performance of the DC grid, the upper limit of the current-limiting reactor is set to 300mH in this example.

[0104] Step 3: Determine the maximum breaking current of the DC circuit breaker based on its breaking capacity and cost requirements. According to common capacity values ​​for DC circuit breakers in existing projects, the maximum breaking current of the DC circuit breaker in this example is set to 15kA.

[0105] Set the value of the current-limiting reactor to the lower limit, i.e., 100mH. Based on the DC grid numerical solution model in step 1, calculate the DC grid fault current under different fault current limiter parameters. Obtain a DC grid fault current limiter parameter configuration scheme that ensures the fault current does not exceed the maximum breaking current of the DC circuit breaker.

[0106] Step 4: Compare the costs of different fault current limiter parameter configuration schemes and prioritize the current limiting scheme with lower cost.

[0107] The cost of a current limiting device includes the cost of the current limiting reactor and the cost of the fault current limiter. The total cost of the current limiting device can be approximately expressed as C = C CLR +C FCL The cost of a current-limiting reactor is approximately proportional to its value. The cost of a fault current limiter is mainly concentrated in the high-power IGBT module, and is related to L... FCL Given the low correlation, the current-limiting reactor should be as small as possible, and the number of fault current limiters should be as few as possible.

[0108] Step 5: Increase the value of the current-limiting reactor by a fixed step size, and repeat steps 2-5 to obtain the optimal parameter coordination configuration scheme for the fault current-limiting device under different current-limiting reactor values. The lowest-cost coordinated parameter configuration scheme for the fault current-limiting device can then be selected using a computer.

[0109] Table 2. Configuration Scheme for Coordination Parameters of DC Grid Current Limiting Device

[0110]

[0111] In this example, the four lowest-cost schemes under different current-limiting reactor values ​​are shown in the table below. The cost difference between the four schemes is not significant. Designers can select the final scheme from several current-limiting design schemes according to actual needs. If it is desired to reduce the impact of excessive current-limiting reactor values ​​on the steady state of the power grid, current-limiting scheme 1 can be selected. If it is desired to reduce the number of new current-limiting devices, current-limiting scheme 4 can be selected. Scheme 2 can be considered as a compromise between the two.

[0112] Figure 8 This is a schematic diagram of the structure of a DC power grid current limiting device parameter collaborative optimization configuration system 800 according to an embodiment of the present invention. Figure 8As shown, the DC power grid current limiting device parameter collaborative optimization configuration system 800 provided in the embodiment of the present invention includes: a model building unit 801, a current limiting reactor value determination unit 802, an initialization unit 803, a configuration scheme determination unit 804, an alternative scheme determination unit 805, an update unit 806, and a configuration unit 807.

[0113] Preferably, the model building unit 801 is used to obtain the actual topology of the DC power grid and establish a numerical solution model of the DC power grid based on the actual topology.

[0114] Preferably, the model building unit 801 establishes a numerical solution model for a DC power grid based on the actual topology, including:

[0115] Based on the actual topology, the converter, transmission line, DC current limiting device, and fault branch are all equivalent to RLC branches, and the current equations of each mesh are written based on the mesh node current method to construct a numerical solution model for the DC power grid.

[0116] Preferably, the model building unit 801 is further configured to:

[0117] In the equivalent phase, the capacitor parameters of the converter are determined based on the equivalent capacitance correction model; the transmission line uses a lumped parameter model; the current-limiting reactor corresponding to each converter station is simplified to a single value, and the fault current limiter is simplified to a single value; the DC current limiting device is equivalent to an equivalent circuit model that varies with time based on the operating time; for the fault branch, when an inter-pole short-circuit fault occurs, the fault branch is equivalent to a resistor connected between the two fault poles, and each converter station corresponds to one fault point.

[0118] Preferably, the current-limiting reactor value determination unit 802 is used to calculate the fault current of the DC power grid under different current-limiting reactor values ​​based on the DC power grid numerical solution model, determine the upper limit of the fault current according to the lower limit of the converter station blocking current, select the current-limiting reactor value corresponding to the upper limit of the fault current as the lower limit of the current-limiting reactor value, and determine the upper limit of the current-limiting reactor value according to the dynamic performance requirements of the power grid.

[0119] Preferably, the initialization unit 803 is used to determine the maximum breaking current of the DC circuit breaker, initialize the value of the current limiting reactor based on the lower limit of the current limiting reactor value, and determine the reference value of the current limiting reactor.

[0120] Preferably, the configuration scheme determination unit 804 is used to calculate the DC grid fault current under different fault current limiter values ​​under the current current limiting reactor reference value based on the DC grid numerical solution model, and to obtain the fault current limiter configuration scheme when the DC grid fault current is less than or equal to the maximum breaking current.

[0121] Preferably, the fault current limiter value is an integer multiple of 5mH; the reference value of the current limiting reactor value is an integer multiple of 10mH.

[0122] Preferably, the alternative scheme determination unit 805 is used to calculate the cost of different configuration schemes and select the configuration scheme with the lowest cost as the alternative scheme.

[0123] Preferably, the updating unit 806 is used to increase the current-limiting reactor reference value according to a preset step size, update the current-limiting reactor reference value, and determine whether the updated current-limiting reactor reference value is greater than the upper limit of the current-limiting reactor value. If so, it enters the configuration unit; otherwise, it enters the configuration scheme determination unit to recalculate.

[0124] Preferably, the configuration unit 807 is used to select the optimal solution from the alternative solutions based on configuration requirements, and to configure parameters based on the optimal solution.

[0125] The DC grid current limiting device parameter collaborative optimization configuration system 800 of the present invention corresponds to the DC grid current limiting device parameter collaborative optimization configuration method 100 of another embodiment of the present invention, and will not be described again here.

[0126] Based on another aspect of the present invention, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any one of the steps in a method for coordinated optimization configuration of current limiting device parameters in a DC power grid.

[0127] According to another aspect of the present invention, the present invention provides an electronic device, comprising:

[0128] The aforementioned computer-readable storage medium; and

[0129] One or more processors for executing a program in the computer-readable storage medium.

[0130] The present invention has been described with reference to a few embodiments. However, it will be apparent to those skilled in the art that other embodiments besides those disclosed above fall equivalently within the scope of the present invention.

[0131] Generally, all terms used in this invention are interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

[0132] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied 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.

[0133] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0134] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0135] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A parameter collaborative optimization configuration method of a current limiting device of a direct current power grid, characterized in that, The method comprises: Step 1, obtaining an actual topology structure of a DC power grid, and establishing a numerical solution model of the DC power grid based on the actual topology structure; Step 2, calculating fault currents of the DC power grid under different current-limiting reactor value conditions based on the numerical solution model of the DC power grid, determining an upper limit value of the fault currents according to a lower limit of a blocking current of a converter station, selecting a current-limiting reactor value corresponding to the upper limit value of the fault currents as a lower limit of the current-limiting reactor value, and determining an upper limit of the current-limiting reactor value according to a dynamic performance requirement of the power grid; Step 3, determining a maximum breaking current of a DC circuit breaker, initializing the current-limiting reactor value based on the lower limit of the current-limiting reactor value, and determining a reference value of the current-limiting reactor; Step 4, calculating DC power grid fault currents under different fault current limiter values of the current-limiting reactor reference value based on the numerical solution model of the DC power grid, and obtaining a fault current limiter configuration scheme when the DC power grid fault current is less than or equal to the maximum breaking current; Step 5, calculating the cost of different configuration schemes, and selecting a configuration scheme with the lowest cost as a candidate scheme; Step 6, increasing the current-limiting reactor reference value by a preset step, updating the current-limiting reactor reference value, and determining whether the updated current-limiting reactor reference value is greater than the upper limit of the current-limiting reactor value, if yes, proceeding to Step 7, otherwise, proceeding to Step 4 to recalculate; Step 7, selecting an optimal scheme from the candidate scheme based on a configuration requirement, and configuring parameters based on the optimal scheme.

2. The method of claim 1, wherein, The numerical solution model of the DC power grid is established based on the actual topology structure, comprising: Based on the actual topology structure, the converter, the transmission line, the DC current limiting device and the fault branch are all equivalent to RLC branches, and the current equations of each mesh are written based on the mesh node current method to construct the numerical solution model of the DC power grid.

3. The method of claim 1, wherein, In the equivalent, the capacitor parameters of the converter are determined based on the equivalent capacitor correction model; the transmission line uses a lumped parameter model; the current-limiting reactor corresponding to each converter station is simplified to a numerical value, and the fault current limiter is simplified to a numerical value; in the equivalent, the DC current limiting device is equivalent to a time-varying equivalent circuit model according to the action time; for the fault branch, when a short circuit fault between the two fault poles occurs, the fault branch is equivalent to a resistance connected between the two fault poles, and each converter station corresponds to a fault point.

4. The method of claim 1, wherein, The fault current limiter value is an integer multiple of 5mH; and the current-limiting reactor reference value is an integer multiple of 10mH.

5. A parameter collaborative optimization configuration system for current limiting devices of a direct current power grid, characterized in that, The system comprises: A model construction unit configured to obtain an actual topology structure of a DC power grid, and establish a numerical solution model of the DC power grid based on the actual topology structure; A current-limiting reactor value determination unit configured to calculate fault currents of the DC power grid under different current-limiting reactor value conditions based on the numerical solution model of the DC power grid, determine an upper limit value of the fault currents according to a lower limit of a blocking current of a converter station, select a current-limiting reactor value corresponding to the upper limit value of the fault currents as a lower limit of the current-limiting reactor value, and determine an upper limit of the current-limiting reactor value according to a dynamic performance requirement of the power grid; The initialization unit is configured to determine a maximum breaking current of the DC circuit breaker, initialize a current limiting reactor value based on a lower limit of the current limiting reactor value, and determine a current limiting reactor reference value. The configuration scheme determination unit is configured to calculate DC power grid fault currents at different fault current limiter values under the current limiting reactor reference value based on the DC power grid numerical solution model, and obtain a fault current limiter configuration scheme when the DC power grid fault current is less than or equal to the maximum breaking current. The alternative scheme determination unit is configured to calculate the cost of different configuration schemes and select the configuration scheme with the lowest cost as an alternative scheme. The updating unit is configured to increase the current limiting reactor reference value by a preset step, update the current limiting reactor reference value, and determine whether the updated current limiting reactor reference value is greater than an upper limit of the current limiting reactor value. The configuration unit is configured to select an optimal scheme from the alternative schemes based on configuration requirements and configure parameters based on the optimal scheme.

6. The system of claim 5, wherein, The model construction unit is configured to establish a DC power grid numerical solution model based on the actual topology structure, including: Based on the actual topology structure, the converter, the transmission line, the DC current limiting device, and the fault branch are all equivalent to RLC branches, and current equations of each mesh node are written based on the mesh node current method to construct the DC power grid numerical solution model.

7. The system of claim 6, wherein, The model construction unit is also configured to: When equivalent, the capacitor parameters of the converter are determined based on the equivalent capacitor correction model; the transmission line uses a lumped parameter model; the current limiting reactor corresponding to each converter station is simplified to a numerical value, and the fault current limiter is simplified to a numerical value; when equivalent, the DC current limiting device is equivalent to a time-varying equivalent circuit model according to the action time; for the fault branch, when a short circuit fault between the two fault poles occurs, the fault branch is equivalent to a resistor connected between the two fault poles, and each converter station corresponds to a fault point.

8. The system of claim 5, wherein, The fault current limiter value is an integer multiple of 5mH, and the current limiting reactor reference value is an integer multiple of 10mH.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to implement the steps of the method of any one of claims 1-4.

10. An electronic device, comprising: It includes: The computer readable storage medium of claim 9; and One or more processors for executing the program in the computer readable storage medium.

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