Single-step prediction active arc extinction control method and device for high-proportion photovoltaic access

Abstract

The invention provides a single-step prediction active arc extinction control method and device for high-proportion photovoltaic access, and relates to the technical field of power electronic technology control application. The method comprises the following steps: acquiring a reference compensation current when a single-phase grounding short circuit fault occurs; obtaining all switching states of the three-level cascaded H-bridge converter, wherein each switching state corresponds to the conduction condition of one group of H-bridge units; a Riemann-Liouville non-integer order derivative is utilized to establish a non-integer order inductance model, and the non-integer order inductance model is utilized to update the three-level H-bridge converter; predicting a current output value of the three-stage cascaded H-bridge converter in each switching state at the next moment based on the updated three-stage cascaded H-bridge converter, and taking each current output value as a predicted compensation current; and determining a target switching state based on the predicted compensation current and the reference compensation current of each switching state so as to control the conduction of the three-stage H-bridge converter. The method can effectively extinguish the arc, and improves the safety and reliability of the power system.

Description

Technical Field

[0001] The present application relates to the technical field of power electronics technology control applications, and particularly to a single-step prediction active arc suppression control method and device for high-proportion photovoltaic access. Background Art

[0002] With the increase in the grid connection ratio of new energy power generation and the widespread use of nonlinear loads, the installed capacity of the new power system is continuously improving. The access of large-scale distributed photovoltaic systems leads to the introduction of harmonics into the distribution network. During a single-phase grounding fault, the interaction between harmonics and the ground capacitance causes a high-frequency capacitive fault current, making it difficult for the traditional distribution network to extinguish the grounding fault arc. The arc will affect the production and operation of enterprises with high requirements for power quality, and may even cause fires in some areas, which is not conducive to the development of local high-tech industries and the improvement of grid reliability. Summary of the Invention

[0003] The present application provides a single-step prediction active arc suppression control method and device for high-proportion photovoltaic access to solve the problem that it is difficult for the distribution network system to extinguish the arc during a single-phase grounding fault under the condition of high-proportion photovoltaic system grid connection in the prior art.

[0004] In a first aspect, the present application provides a single-step prediction active arc suppression control method for high-proportion photovoltaic access, including:

[0005] Obtaining a reference compensation current when a single-phase grounding short-circuit fault occurs;

[0006] Obtaining all switch states of a three-level cascaded H-bridge converter, and each switch state corresponds to a set of conduction conditions of the H-bridge units;

[0007] Using the Riemann-Liouville non-integer order derivative to establish a non-integer order inductor model, and updating the three-level cascaded H-bridge converter by using the non-integer order inductor model;

[0008] Based on the updated three-level cascaded H-bridge converter, predicting the current output value of the three-level cascaded H-bridge converter at each switch state at the next moment, and using each current output value as a predicted compensation current;

[0009] Based on the predicted compensation current at each switch state and the reference compensation current, determining a target switch state to control the conduction of the three-level cascaded H-bridge converter.

[0010] In a second aspect, the present application provides a single-step prediction active arc suppression control device for high-proportion photovoltaic access, including:

[0011] A first acquisition module for obtaining a reference compensation current when a single-phase grounding short-circuit fault occurs;

[0012] A second acquisition module, configured to acquire all switch states of a three - stage cascaded H - bridge converter, where each switch state corresponds to a conduction condition of a group of H - bridge units;

[0013] An update module, configured to establish a non - integer - order inductor model by using Riemann - Liouville non - integer - order derivatives, and update the three - stage cascaded H - bridge converter by using the non - integer - order inductor model;

[0014] A current calculation module, configured to predict the current output value of the three - stage cascaded H - bridge converter at each switch state at the next moment based on the updated three - stage cascaded H - bridge converter, and use each current output value as a predicted compensation current;

[0015] A determination module, configured to determine a target switch state based on the predicted compensation current at each switch state and the reference compensation current, so as to control the conduction of the three - stage cascaded H - bridge converter.

[0016] This application provides a single - step prediction active arc suppression control method and device for high - proportion photovoltaic access. By acquiring the reference compensation current when a single - phase grounding short - circuit fault occurs; acquiring all switch states of a three - stage cascaded H - bridge converter, where each switch state corresponds to a conduction condition of a group of H - bridge units; establishing a non - integer - order inductor model by using Riemann - Liouville non - integer - order derivatives, and updating the three - stage cascaded H - bridge converter by using the non - integer - order inductor model; predicting the current output value of the three - stage cascaded H - bridge converter at each switch state at the next moment based on the updated three - stage cascaded H - bridge converter, and using each current output value as a predicted compensation current; determining a target switch state based on the predicted compensation current at each switch state and the reference compensation current, so as to control the conduction of the three - stage cascaded H - bridge converter. This application updates the three - stage cascaded H - bridge converter through a non - integer - order inductor model, and predicts the current output value at each switch state based on the updated three - stage cascaded H - bridge converter to quickly track the reference compensation current, thereby determining the target switch state for controlling the conduction of the three - stage cascaded H - bridge converter, achieving the purpose of effective arc suppression, and improving the safety and reliability of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is a schematic diagram of the data structure of the single - step prediction active arc suppression control method for high - proportion photovoltaic access provided by the embodiment of the present application;

[0019] Figure 2 It is a schematic structural diagram of a parallel hybrid arc suppression system provided by an embodiment of the present application;

[0020] Figure 3 It is a schematic structural diagram of a three - stage cascaded H - bridge topology provided by an embodiment of the present application;

[0021] Figure 4 It is a schematic structural diagram of a non - integer - order inductor model provided by an embodiment of the present application;

[0022] Figure 5 It is a schematic diagram of piece - wise broken - line approximation of a rational approximation method provided by an embodiment of the present application;

[0023] Figure 6 It is a schematic diagram of the construction of a non - integer - order inductor model provided by an embodiment of the present application;

[0024] Figure 7 It is a schematic structural diagram of a three - stage cascaded H - bridge converter based on a non - integer - order inductor provided by an embodiment of the present application;

[0025] Figure 8 It is a flowchart of the predicted operation based on a non - integer - order inductor provided by an embodiment of the present application;

[0026] Figure 9 It is a schematic diagram of the tracking effect of the predicted compensation current provided by an embodiment of the present application;

[0027] Figure 10 It is a schematic diagram of the segmented compensation effect of the residual current in a single - phase grounding fault provided by an embodiment of the present application;

[0028] Figure 11 It is a schematic structural diagram of a 6060 simulator and a 1070 controller for hardware - in - the - loop simulation provided by an embodiment of the present application;

[0029] Figure 12 It is a hardware - in - the - loop simulation effect diagram of the tracking of the predicted compensation current provided by an embodiment of the present application;

[0030] Figure 13 It is a hardware - in - the - loop simulation effect diagram of the segmented compensation of the residual current in a single - phase grounding fault provided by an embodiment of the present application;

[0031] Figure 14 It is a schematic structural diagram of a single - step prediction active arc suppression control device for high - proportion photovoltaic access provided by an embodiment of the present application. Specific implementation manners

[0032] In the following description, specific details such as specific system structures and technologies are provided for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from obstructing the description of the present application.

[0033] To make the objectives, technical solutions, and advantages of the present application clearer, the following will be described through specific embodiments in conjunction with the accompanying drawings.

[0034] Aiming at the problem that traditional distribution networks are difficult to extinguish the arc of single-phase grounding faults after a high proportion of photovoltaic power is connected, in order to reduce the adverse effects of single-phase grounding faults on the distribution network system under the grid connection of a high proportion of photovoltaic systems and improve the power supply reliability of the grid, the present application studies a flexible grounding fault protection device adapted to the current changes in the distribution network to achieve fast and accurate compensation current tracking, thereby realizing the control technology of reliable arc extinguishing. That is, the present application proposes a single-step prediction active arc extinguishing control method for active arc extinguishing based on non-integer-order inductance and applicable to high-proportion photovoltaic access. Based on the traditional integer-order three-level cascaded H-bridge converter, this method uses non-integer-order inductance for current filtering; and on this basis, the definition of Riemann-Liouville non-integer-order derivative is introduced to construct a more accurate three-level cascaded H-bridge non-integer-order basic mathematical model, and the prediction model controller is derived through discretization. The minimum error function is used as the objective function to quickly track the reference compensation current, thereby achieving the purpose of effective arc extinguishing and improving the safety and reliability of the power system.

[0035] Aiming at the optimization requirements of the arc extinguishing control technology for the three-level cascaded H-bridge converter, the present application starts from the basic topology structure of the H-bridge and combines non-integer-order calculus theory to construct a new control strategy applicable to the three-level cascaded H-bridge converter. Based on its wide model practicability, high refinement degree, and easy adjustment of controller parameters, it can quickly track the reference compensation current, thereby effectively extinguishing the arc. The corresponding solution idea is as follows:

[0036] First, it is necessary to improve the basic structure of the three-level cascaded H-bridge converter. Each unit of the H-bridge consists of four switches. By controlling the conduction and cut-off of these switches, the control of the output compensation current is realized. On this basis, the definition of Riemann-Liouville non-integer-order derivative applicable to continuous and discrete systems is introduced to construct the non-integer-order basic mathematical model of the H-bridge, so as to effectively describe the dynamic system with non-integer-order characteristics.

[0037] Based on the non-integer order basic mathematical model, a non-integer order prediction model is further constructed. This non-integer order prediction model can utilize the known input signal and the current and historical system states to predict the predicted value of the output current for a future time period, providing a reference for the controller. Using the non-integer order prediction model, the output currents in different switch states of the H-bridge are predicted. By changing the switch state combinations, different output current waveforms are obtained. Comparing the currents in different switch states can evaluate the effect of the control strategy, and a minimum error objective function is established. At each sampling period, according to the current switch state and the converter output current value, the non-integer order prediction model is used to predict the output currents in various switch states and compare them with the reference compensation current, so as to select the optimal switch combination to achieve precise tracking of the compensation current.

[0038] Through the above comprehensive non-integer order model prediction optimization method, the purposes of high-precision model refinement, precise tracking of current, and improvement of capacitive current compensation accuracy can be achieved, thereby effectively eliminating arc and improving the reliability of the power system.

[0039] Figure 1 The following is a detailed implementation flowchart of the single-step prediction active arc suppression control method for high-proportion photovoltaic access provided by the embodiments of the present application:

[0040] In step 101, the reference compensation current when a single-phase grounding short-circuit fault occurs is obtained.

[0041] In the embodiments of the present application, for a power system with high-proportion photovoltaic access, when a single-phase grounding short-circuit fault occurs, the reference compensation current at that time is obtained.

[0042] In a possible implementation manner, obtaining the reference compensation current when a single-phase grounding short-circuit fault occurs includes:

[0043] Obtaining the short-circuit fault current when a single-phase grounding short-circuit fault occurs, where the short-circuit fault current includes a fundamental frequency component and a high-frequency component;

[0044] Inputting the fundamental frequency component and the high-frequency component into the first formula to calculate the reference compensation current. The first formula is:

[0045] i * =-(i b +i h )

[0046] Where, i * is the reference compensation current, i b is the fundamental frequency component, and i h is the high-frequency component.

[0047] Optionally, when a single-phase grounding short-circuit fault occurs, its short-circuit fault current mainly includes the fundamental frequency component ib and the high-frequency component i h , to compensate for the short-circuit fault current, a compensation current with the same amplitude and opposite direction to the fault current needs to be injected from the neutral point to achieve the purpose of zero single-phase grounding current, thereby effectively eliminating the arc.

[0048] To inject a more accurate compensation current, the embodiment of the present application needs to obtain the reference compensation current i * , and then feedback it to the controller to provide a reference for the output current at the next control moment.

[0049] In step 102, obtain all the switching states of the three-level cascaded H-bridge converter, and each switching state corresponds to a set of conduction conditions of the H-bridge unit.

[0050] Before obtaining the switching state, the embodiment of the present application also needs to perform topology selection and set the arc suppression system, that is: for the problem that the high-frequency capacitive fault current caused by the interaction of harmonics and the ground capacitance in the power system is difficult to compensate during single-phase grounding faults, a parallel hybrid arc suppression system is adopted, and its structural schematic diagram is referred to Figure 2 as shown. This system is composed of a parallel connection of an arc suppression inverter and a converter connected to the neutral point through a transformer. Both are connected between the neutral point and the ground. The arc suppression inverter performs the main compensation, and the power electronic device performs the auxiliary compensation to eliminate the fault current, thereby achieving the purpose of arc suppression.

[0051] In addition, the power electronic topology adopts a single-phase three-level cascaded H-bridge topology, which can achieve the purpose of multi-level output, thereby reducing the harmonic content of the output current and improving the power utilization rate. The structural schematic diagram of the single-phase three-level cascaded H-bridge topology is referred to Figure 3 as shown, and it includes three H-bridge units.

[0052] Since each H-bridge unit has four switching states, its specific switching conditions are shown in Table 1.

[0053] Table 1 Switching state group table of a single cascaded H-bridge unit

[0054]

[0055] Among them, arm 1 is the left arm of the H-bridge unit, and arm 2 is the right arm of the H-bridge unit. When the arm state is 0, the lower arm conducts and the upper arm is turned off, representing that the arm outputs zero level; when the arm state is 1, the upper arm conducts and the lower arm is turned off, representing that the arm outputs the DC side voltage value.

[0056] The embodiment of the present application adopts a three-level cascaded H-bridge converter, and there are actually 64 kinds of its switching state combinations. After eliminating the redundant switching state combinations, there are 7 effectively usable switching state combinations, and the specific states of its switching state combinations and the output levels under different states are shown in Table 2.

[0057] Table 2 Switching State Group Table of a Single Cascade H-Bridge Unit

[0058]

[0059] Among them, for s i , when i is odd, it represents the left arm of the H-bridge unit, and when i is even, it represents the right arm of the H-bridge unit.

[0060] All the switching states of the three-cascade H-bridge converter obtained in the embodiments of this application can be referred to as shown in Table 2.

[0061] In step 103, using the Riemann-Liouville non-integer order derivative, a non-integer order inductor model is established, and the three-cascade H-bridge converter is updated using the non-integer order inductor model.

[0062] In the embodiments of this application, using the Riemann-Liouville non-integer order derivative, a non-integer order inductor model is established, and based on the non-integer order inductor model, a topological structure model of the three-cascade H-bridge converter based on the non-integer order inductor is established.

[0063] In a possible implementation, using the Riemann-Liouville non-integer order derivative to establish a non-integer order inductor model includes:

[0064] Using the Riemann-Liouville non-integer order derivative to calculate the values of a preset number of components, where the components include inductors and resistors;

[0065] Connecting the inductor components and resistor components in series for each group, and connecting the series-connected components in parallel for each group to obtain a non-integer order inductor model.

[0066] Optionally, as shown in Figure 4 , the relationship between the voltage and current at both ends of the non-integer order inductor model is as shown in formula (1):

[0067]

[0068] Among them, u L is the voltage at both ends of the non-integer order inductor, L α is the non-integer order inductance value, i L is the current value flowing through the non-integer order inductor, and α is the inductor order.

[0069] Performing Laplace transform on formula (1), formula (2) can be obtained:

[0070] u L (s) = s α L α i L(s) (2)

[0071] Among them, u L (s) is the voltage across the non-integer order inductor after Laplace transform, and s α is a non-integer order operator.

[0072] The admittance calculation formula of the non-integer order inductor L α is as shown in formula (3):

[0073]

[0074] Among them, Y L (s) is the admittance of the non-integer order inductor.

[0075] Then, a non-integer order inductor model is constructed. Based on the piecewise linear approximation principle, this application embodiment is applied to determine the approximate circuit parameters of the non-integer order inductor. For the non-integer order operator s α (where α > 0) is approximated within a specific frequency range (ω b , ω h ). The specific approximation process can be understood from the approximation schematic diagram as shown in Figure 5 .

[0076] Referring to Figure 5 , with the help of piecewise broken line approximation, the dynamic performance of the approximate function in a specific frequency band can be intuitively analyzed. The zero and pole distributions of H(s) are as shown in formula (4):

[0077]

[0078] Among them, H(s) is, ω k is the k-th zero, ω′ k is the k-th pole, K is the gain, and N is the number of zeros or poles.

[0079] The calculation formulas for the zero ω k , the pole ω′ k and the gain K are formula (5):

[0080]

[0081] Among them, ω b is the lowest approximation frequency, and ω h is the highest approximation frequency.

[0082] According to formula (4) and formula (5), within the specified frequency range and the determined order, the rational approximation form H1(s) of the non-integer order capacitance impedance function is calculated, and its detailed expression is as shown in formula (6):

[0083]

[0084] Among them, H1(s) is the rational approximation form of the impedance function of the fractional-order capacitor, and r i = 1 / L1,

[0085] Among them, Figure 6 is the schematic diagram of the structure of the α-order fractional-order inductor. The fractional-order inductor model is built through the Figure 6 shown RL parallel circuit configuration. The mathematical expression of its admittance is formula (7):

[0086]

[0087] Among them, L n is the inductance value of the nth parallel branch, is the resistance value of the nth parallel branch.

[0088] By combining formula (6) and formula (7), the fractional-order inductor model can be obtained:

[0089]

[0090] Among them, L i is the value of the ith inductor element, is the value of the ith resistor element, p i is the pole of the rational approximation formula, and r i is the zero of the rational approximation formula.

[0091] Correspondingly, substituting Figure 6 and into Figure 3 obtains Figure 7 , that is, the schematic diagram of the topological structure of the three-level cascaded H-bridge converter based on the fractional-order inductor.

[0092] In step 104, based on the updated three-level cascaded H-bridge converter, predict the current output value of the three-level cascaded H-bridge converter in each switching state at the next moment, and use each current output value as the predicted compensation current.

[0093] In the embodiment of the present application, according to the three-level cascaded H-bridge converter updated in step 103, predict the current output value of the three-level cascaded H-bridge converter in each switching state at the next moment, that is, use the current output value in each switching state as the predicted compensation current.

[0094] In a possible implementation manner, based on the updated three-level cascaded H-bridge converter, predict the current output value of the three-level cascaded H-bridge converter in each switching state at the next moment, and use each current output value as the predicted compensation current, including:

[0095] Calculate the current output value at the next moment by using the updated three - stage cascaded H - bridge converter;

[0096] Based on the current output value at the next moment, calculate the current output value of the three - stage cascaded H - bridge converter in each switching state at the next moment.

[0097] Optionally, according to Figure 6 It can be obtained that:

[0098]

[0099] Among them, u0(t) is the output voltage of the three - stage cascaded H - bridge arm side, u′ N (t) is the output voltage value of the primary side of the transformer, u′ N (t)=n·u N (t), n is the transformer turns ratio, u N (t) is the neutral point voltage.

[0100] Further simplification gives:

[0101]

[0102] Among them, Δ α i(t) is the α - th derivative of i(t).

[0103] Performing α - order integration on both sides of formula (9) gives:

[0104]

[0105] Among them, t0 is the previous moment, and i(t0) is the current value at the previous moment.

[0106] Let Based on the Riemann - Liouville non - integer order derivative definition Substituting into formula (10) gives:

[0107]

[0108] Among them,

[0109] Discretizing formula (11) gives:

[0110]

[0111] Among them, i(t k+1 ) is the current value at the next moment, i(t k ) is the current value at the previous moment.

[0112] When the unit control interval h = t k+1 -t kWhen, further calculations yield:

[0113]

[0114] Substituting into formula (13) gives:

[0115]

[0116] Further obtain the second formula, that is, calculate the current output value at the next moment through the second formula. The second formula is:

[0117]

[0118] where i(k + 1) is the current output value at the (k + 1)-th moment, i(k) is the current output value at the k-th moment, K is a constant coefficient, F is the reciprocal coefficient of time, G is the reciprocal coefficient of inductance, u(k) is the switching function, and its value can be -3, -2, -1, 0, 1, 2, 3; U N (k) is the voltage value of the neutral point of the system at the k-th moment, h is the time interval, R is the resistance value of the output side, L α is the non-integer order inductance value of the output side, and k is the moment.

[0119] It can be seen from the second formula that the non-integer order model has memory. When the system shows non-linearity, historical data within the range of the previous control moment can be considered for reliable prediction.

[0120] A single H-bridge unit predicts the current output value at the next moment in each switching state based on the feedback signal of the current control point, and then determines the predicted current value of the next control point. In the embodiment of the present application, when a three-stage cascaded H-bridge converter is adopted, the calculation formula for the current output value at the next moment in each switching state is the third formula. The third formula is:

[0121]

[0122] where i(k + 1)|S0 is the output current value of the switching state S0 at the (k + 1)-th moment, i(k + 1)|S1 is the output current value of the switching state S1 at the (k + 1)-th moment, i(k + 1)|S2 is the output current value of the switching state S2 at the (k + 1)-th moment, i(k + 1)|S3 is the output current value of the switching state S3 at the (k + 1)-th moment, i(k + 1)|S4 is the output current value of the switching state S4 at the (k + 1)-th moment, i(k + 1)|S5 is the output current value of the switching state S5 at the (k + 1)-th moment, i(k + 1)|S6 is the output current value of the switching state S6 at the (k + 1)-th moment, U N (k) is the voltage value of the neutral point of the system at the k-th moment, U dc$V_{dc}$ is the DC-side voltage value of the H-bridge unit, $i(k)$ is the current output value at the $k$-th moment, $K$ is a constant coefficient, $F$ is the reciprocal coefficient of time, and $G$ is the reciprocal coefficient of inductance.

[0123] In step 105, based on the predicted compensation current and the reference compensation current in each switching state, the target switching state is determined to control the conduction of the three-level cascaded H-bridge converter.

[0124] In the embodiment of the present application, the predicted compensation current in each switching state and the reference compensation current obtained in step 101 are respectively used to determine the target switching state, so that the parallel hybrid arc suppression system controls the three-level cascaded H-bridge converter to conduct according to the target switching state combination for arc suppression.

[0125] In a possible implementation manner, determining the target switching state based on the predicted compensation current and the reference compensation current in each switching state includes:

[0126] Using the predicted compensation current and the reference compensation current in each switching state, calculate the error value corresponding to each switching state;

[0127] Select the minimum error value from all the error values as the target error value, and use the switching state corresponding to the target error value as the target switching state.

[0128] Optionally, use the predicted compensation current and the reference compensation current in each switching state to calculate the error value corresponding to each switching state, then select the minimum error value from all the error values as the target error value, and use the switching state combination corresponding to the target error value as the target switching state for operation to track the reference compensation current to the greatest extent, so as to achieve the purpose of effective arc suppression.

[0129] Exemplarily, for the conduction conditions of various switching state combinations in Table 2, if the error value corresponding to S1 is the smallest, then S1 is used as the target switching state.

[0130] In a possible implementation manner, using the predicted compensation current and the reference compensation current in each switching state to calculate the error value corresponding to each switching state includes:

[0131] For each switching state, calculate the difference between the predicted compensation current and the reference compensation current in this switching state, and take the absolute value of the difference as the error value corresponding to this switching state.

[0132] Optionally, the method for calculating the error value corresponding to each switching state is: for each switching state, calculate the difference between the predicted compensation current and the reference compensation current in this switching state, take the absolute value of the difference, and use the corresponding absolute value as the error value.

[0133] Specifically, it is implemented by the following steps:

[0134] Using the reference compensation current and the possible predicted compensation currents under different switching states at the next moment, the difference between the two is calculated respectively, as shown in formula (15):

[0135] Δe(k + 1) = |i * (k + 1) - i(k + 1)| (15)

[0136] Where, Δe(k + 1) is the error value at the (k + 1)-th moment, i * (k + 1) is the reference compensation current, and i(k + 1) is the predicted compensation current.

[0137] The error value Δe(k + 1) can be obtained from formula (15), laying a foundation for the subsequent rolling optimization stage, thereby effectively eliminating the arc.

[0138] Also, because the goal of the arc suppression system in the embodiment of this application is to make the compensation current output by the three-level cascaded H-bridge converter accurately follow the reference current, achieving the goal of minimizing the error, an error objective function J is established:

[0139] J = Δe(k + 1) = |i * (k + 1) - i(k + 1)| (16)

[0140] Substitute the error value Δe(k + 1) under different switching states into formula (16). By comparing the values of the error objective function J under different switching states, select the switching state with the minimum J for operation, tracking the reference compensation current to the greatest extent, thereby achieving the goal of effective arc suppression.

[0141] Exemplarily, referring to Figure 8 , input the predicted compensation current and the reference compensation current, and the error objective function J corresponding to each predicted compensation current can be obtained. The schematic diagram of the error objective function J is referred to Figure 9 As shown, select the switching state corresponding to the minimum error value for operation to eliminate the arc. The arc suppression result is as shown in Figure 10 As shown, it can be seen that the arc suppression effect is very good.

[0142] Also exemplarily, Figure 11 For the 6060 simulator and 1070 controller of the hardware-in-the-loop simulation, on the basis of Figure 11 , input the predicted compensation current and the reference compensation current, and the error objective function J corresponding to each predicted compensation current can be obtained. The schematic diagram of the error objective function J is referred to Figure 12 As shown, select the switching state corresponding to the minimum error value for operation to eliminate the arc. The arc suppression result is as shown in Figure 13 As shown, it can also be seen that the arc suppression effect is very good.

[0143] The present application provides a single-step prediction active arc suppression control method for high-proportion photovoltaic access. The method includes obtaining a reference compensation current when a single-phase grounding short-circuit fault occurs; obtaining all switching states of a three-level cascaded H-bridge converter, where each switching state corresponds to a conduction situation of a group of H-bridge units; using the Riemann-Liouville non-integer order derivative to establish a non-integer order inductor model, and updating the three-level cascaded H-bridge converter using the non-integer order inductor model; based on the updated three-level cascaded H-bridge converter, predicting the current output value of the three-level cascaded H-bridge converter at each switching state at the next moment, and using each current output value as a predicted compensation current; based on the predicted compensation current and the reference compensation current at each switching state, determining a target switching state to control the conduction of the three-level cascaded H-bridge converter. Through the non-integer order inductor model, the present application updates the three-level cascaded H-bridge converter, and based on the updated three-level cascaded H-bridge converter, predicts the current output value at each switching state to quickly track the reference compensation current, thereby determining the target switching state for controlling the conduction of the three-level cascaded H-bridge converter, achieving the purpose of effective arc suppression, and improving the safety and reliability of the power system.

[0144] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0145] The following is the device embodiment of the present application. For the details not described in detail, reference may be made to the corresponding method embodiment above.

[0146] Figure 14 The structural schematic diagram of the single-step prediction active arc suppression control device for high-proportion photovoltaic access provided by the embodiment of the present application is shown. For the convenience of description, only the parts related to the embodiment of the present application are shown and are described in detail as follows:

[0147] As Figure 14 shown, the single-step prediction active arc suppression control device 14 for high-proportion photovoltaic access includes:

[0148] A first acquisition module 141, configured to acquire a reference compensation current when a single-phase grounding short-circuit fault occurs;

[0149] A second acquisition module 142, configured to acquire all switching states of a three-level cascaded H-bridge converter, where each switching state corresponds to a conduction situation of a group of H-bridge units;

[0150] An update module 143, configured to use the Riemann-Liouville non-integer order derivative to establish a non-integer order inductor model, and update the three-level cascaded H-bridge converter using the non-integer order inductor model;

[0151] The current calculation module 144 is configured to predict the current output values of the three - stage cascaded H - bridge converter at the next moment in each switching state based on the updated three - stage cascaded H - bridge converter, and use each current output value as the predicted compensation current;

[0152] The determination module 145 is configured to determine the target switching state based on the predicted compensation current and the reference compensation current in each switching state, so as to control the conduction of the three - stage cascaded H - bridge converter.

[0153] This application provides a network measurement device based on a two - order three - stage sketch. By obtaining the reference compensation current when a single - phase ground short - circuit fault occurs; obtaining all the switching states of the three - stage cascaded H - bridge converter, and each switching state corresponds to a set of conduction conditions of the H - bridge units; using the Riemann - Liouville non - integer - order derivative to establish a non - integer - order inductance model, and using the non - integer - order inductance model to update the three - stage cascaded H - bridge converter; predicting the current output values of the three - stage cascaded H - bridge converter at the next moment in each switching state based on the updated three - stage cascaded H - bridge converter, and using each current output value as the predicted compensation current; determining the target switching state based on the predicted compensation current and the reference compensation current in each switching state, so as to control the conduction of the three - stage cascaded H - bridge converter. This application updates the three - stage cascaded H - bridge converter through the non - integer - order inductance model, and predicts the current output values in each switching state based on the updated three - stage cascaded H - bridge converter to quickly track the reference compensation current, thereby determining the target switching state for controlling the conduction of the three - stage cascaded H - bridge converter, achieving the purpose of effective arc suppression and improving the safety and reliability of the power system.

[0154] In a possible implementation manner, the first acquisition module can be configured to:

[0155] Obtain the short - circuit fault current when a single - phase ground short - circuit fault occurs, and the short - circuit fault current includes a fundamental - frequency component and a high - frequency component;

[0156] Input the fundamental - frequency component and the high - frequency component into the first formula to calculate the reference compensation current, and the first formula is:

[0157] i * =-(i b +i h )

[0158] Wherein, i * is the reference compensation current, i b is the fundamental - frequency component, and i h is the high - frequency component.

[0159] In a possible implementation manner, the update module can be configured to:

[0160] Calculate the values of a preset number of components, including inductors and resistors, using Riemann-Liouville non-integer order derivatives;

[0161] Connect the inductor components and resistor components in series for each group, and connect the series-connected components of each group in parallel to obtain a non-integer order inductor model.

[0162] In a possible implementation, the non-integer order inductor model is:

[0163]

[0164] where L i is the value of the i-th inductor component, is the value of the i-th resistor component, p i is the pole of the rational approximation, r i is the zero of the rational approximation.

[0165] In a possible implementation, the current calculation module can be used to:

[0166] Calculate the current output value at the next moment using the updated three-level cascaded H-bridge converter;

[0167] Based on the current output value at the next moment, calculate the current output value of the three-level cascaded H-bridge converter in each switching state at the next moment.

[0168] In a possible implementation, the current calculation module can also be used to:

[0169] Calculate the current output value at the next moment through the second formula, and the second formula is:

[0170]

[0171] where i(k + 1) is the current output value at the (k + 1)-th moment, i(k) is the current output value at the k-th moment, K is a constant coefficient, F is the reciprocal of time coefficient, G is the reciprocal of inductance coefficient, u(k) is the switching function, U N (k) is the voltage value of the neutral point of the system at the k-th moment, h is the time interval, R is the output side resistance value, L α is the non-integer order inductance value of the output side, and k is the moment.

[0172] In a possible implementation, the current calculation module can also be used to:

[0173] Calculate the current output value of the three-level cascaded H-bridge converter in each switching state at the next moment through the third formula, and the third formula is:

[0174]

[0175] Among them, i(k + 1)|S0 is the output current value of the switch state S0 at the (k + 1)-th moment, i(k + 1)|S1 is the output current value of the switch state S1 at the (k + 1)-th moment, i(k + 1)|S2 is the output current value of the switch state S2 at the (k + 1)-th moment, i(k + 1)|S3 is the output current value of the switch state S3 at the (k + 1)-th moment, i(k + 1)|S4 is the output current value of the switch state S4 at the (k + 1)-th moment, i(k + 1)|S5 is the output current value of the switch state S5 at the (k + 1)-th moment, i(k + 1)|S6 is the output current value of the switch state S6 at the (k + 1)-th moment, U N (k) is the voltage value of the neutral point of the system at the k-th moment, U dc is the DC-side voltage value of the H-bridge unit, i(k) is the current output value at the k-th moment, K is a constant coefficient, F is the reciprocal coefficient of time, and G is the reciprocal coefficient of inductance.

[0176] In a possible implementation manner, the determination module can be used to:

[0177] Calculate the error value corresponding to each switch state by using the predicted compensation current and the reference compensation current in each switch state;

[0178] Select the minimum error value from all the error values as the target error value, and use the switch state corresponding to the target error value as the target switch state.

[0179] In a possible implementation manner, the determination module can also be used to:

[0180] For each switch state, calculate the difference between the predicted compensation current and the reference compensation current in this switch state, and take the absolute value of the difference as the error corresponding to this switch state.

[0181] In the above embodiments, the descriptions of the various embodiments have their own focuses. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0182] Those of ordinary skill in the art can realize that the templates, units, and algorithm steps of the various examples described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professionals can use different methods for each specific application to implement the described functions, but such implementation should not be considered to exceed the scope of the present invention.

[0183] If the above-mentioned module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, to implement all or part of the processes in the above-mentioned method embodiments of the present invention, it can also be completed by a computer program instructing relevant hardware. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, it can implement the steps of the above-mentioned various embodiments of the single-step prediction active arc suppression control method for high-proportion PV access. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file, or some intermediate form, etc. The computer-readable medium can include: any entity or device that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0184] The above-mentioned embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A single-step prediction active arc suppression control method for high-proportion photovoltaic access, characterized in that, The method includes: Obtaining a reference compensation current when a single-phase grounding short-circuit fault occurs; obtaining all switching states of a three-level cascaded H-bridge converter, where each switching state corresponds to a conduction situation of a group of H-bridge units; using the Riemann-Liouville non-integer order derivative to establish a non-integer order inductance model, and updating the three-level cascaded H-bridge converter using the non-integer order inductance model; based on the updated three-level cascaded H-bridge converter, predicting the current output value of the three-level cascaded H-bridge converter in each switching state at the next moment, and taking each current output value as a predicted compensation current; based on the predicted compensation current and the reference compensation current in each switching state, determining a target switching state to control the conduction of the three-level cascaded H-bridge converter.

2. The single-step prediction active arc suppression control method for high-proportion photovoltaic access according to claim 1, wherein The obtaining of the reference compensation current when a single-phase grounding short-circuit fault occurs includes: Obtaining a short-circuit fault current when a single-phase grounding short-circuit fault occurs, where the short-circuit fault current includes a fundamental frequency component and a high-frequency component; Inputting the fundamental frequency component and the high-frequency component into a first formula to calculate the reference compensation current, and the first formula is: i * = -(i b + i h ) where i * is the reference compensation current, i b is the fundamental frequency component, and i h is the high frequency component.

3. The single-step prediction active arc suppression control method for high-proportion PV access according to claim 1, wherein The using of the Riemann-Liouville non-integer order derivative to establish a non-integer order inductance model includes: Using the Riemann-Liouville non-integer order derivative to calculate the values of a preset number of components, where the components include inductors and resistors; Connecting each group of inductor elements and resistor elements in series, and connecting the series-connected groups of elements in parallel to obtain the non-integer order inductance model.

4. The single-step prediction active arc suppression control method for high-proportion photovoltaic access according to claim 3, wherein, The non-integer order inductance model is: Among them, L i is the value of the i-th inductive element, is the value of the i-th resistive element, p i is the pole of the rational approximation, r i is the zero of the rational approximation.

5. The single-step prediction active arc suppression control method for high-proportion photovoltaic access according to claim 1, characterized in that The predicting of the current output value of the three-level cascaded H-bridge converter in each switching state at the next moment based on the updated three-level cascaded H-bridge converter and taking each current output value as a predicted compensation current includes: Using the updated three-level cascaded H-bridge converter to calculate the current output value at the next moment; Based on the current output value at the next moment, calculating the current output value of the three-level cascaded H-bridge converter in each switching state at the next moment.

6. The single-step prediction active arc suppression control method for high-proportion PV access according to claim 5, characterized in that The using of the updated three-level cascaded H-bridge converter to calculate the current output value at the next moment includes: Calculating the current output value at the next moment through a second formula, and the second formula is: Among them, i(k + 1) is the current output value at the (k + 1)-th moment, i(k) is the current output value at the k-th moment, K is a constant coefficient, F is the reciprocal of time coefficient, G is the reciprocal of inductance coefficient, u(k) is the switching function, U N (k) is the voltage value of the neutral point of the system at the k-th moment, h is the time interval, R is the output side resistance, L α is the non-integer order inductor on the output side, and k is the moment.

7. The single-step prediction active arc suppression control method for high-proportion PV access according to claim 5, characterized in that The calculating of the current output value of the three-level cascaded H-bridge converter in each switching state at the next moment based on the current output value at the next moment includes: Calculating the current output value of the three-level cascaded H-bridge converter in each switching state at the next moment through a third formula, and the third formula is: Among them, i(k + 1)|S0 is the output current value of the switch state S0 at the (k + 1)-th moment, i(k + 1)|S1 is the output current value of the switch state S1 at the (k + 1)-th moment, i(k + 1)|S2 is the output current value of the switch state S2 at the (k + 1)-th moment, i(k + 1)|S3 is the output current value of the switch state S3 at the (k + 1)-th moment, i(k + 1)|S4 is the output current value of the switch state S4 at the (k + 1)-th moment, i(k + 1)|S5 is the output current value of the switch state S5 at the (k + 1)-th moment, i(k + 1)|S6 is the output current value of the switch state S6 at the (k + 1)-th moment, U N (k) is the voltage value of the neutral point of the system at the k-th moment, U dc is the DC-side voltage value of the H-bridge unit, i(k) is the current output value at the k-th moment, K is a constant coefficient, F is the reciprocal-of-time coefficient, and G is the reciprocal-of-inductance coefficient.

8. The single-step prediction active arc suppression control method for high-proportion PV access according to claim 1, wherein The determining of the target switching state based on the predicted compensation current and the reference compensation current in each switching state includes: Using the predicted compensation current and the reference compensation current in each switching state to calculate the error value corresponding to each switching state; Selecting the minimum error value from all the error values as the target error value, and taking the switching state corresponding to the target error value as the target switching state.

9. The single-step prediction active arc suppression control method for high-proportion photovoltaic access according to claim 8, wherein, The using of the predicted compensation current and the reference compensation current in each switching state to calculate the error value corresponding to each switching state includes: For each switch state, calculate the difference between the predicted compensation current in this switch state and the reference compensation current, and take the absolute value of the difference as the error value corresponding to this switch state.

10. A single-step prediction active arc suppression control device for high-proportion photovoltaic access, characterized in that, The method includes: A first acquisition module, configured to acquire the reference compensation current when a single-phase grounding short-circuit fault occurs; A second acquisition module, configured to acquire all switch states of the three-level cascaded H-bridge converter, and each switch state corresponds to a set of conduction conditions of the H-bridge units; An update module, configured to establish a non-integer order inductor model by using the Riemann-Liouville non-integer order derivative, and update the three-level cascaded H-bridge converter by using the non-integer order inductor model; A current calculation module, configured to predict the current output value of the three-level cascaded H-bridge converter at the next moment in each switch state based on the updated three-level cascaded H-bridge converter, and use each current output value as the predicted compensation current; A determination module, configured to determine a target switch state based on the predicted compensation current and the reference compensation current in each switch state, so as to control the conduction of the three-level cascaded H-bridge converter.

Images