A photovoltaic active power up-regulation method based on P-U curve interpolation variable universe fuzzy control

Abstract

The present application relates to photovoltaic power generation technology field, disclose a kind of based on P-U curve interpolation variable domain fuzzy control's photovoltaic active up-regulation method, the method comprises the following steps: step 1: estimate photovoltaic power generation unit current maximum output power can be generated, then photovoltaic array receives active up-regulation instruction;Step 2: by the variable domain fuzzy control of P-U curve interpolation is quickly up-regulated photovoltaic power generation unit current operating point to active up-regulation instruction nearby;Step 3: in active instruction nearby by small step size's perturbation observation method accurate smooth tracking to active up-regulation instruction.Compared with prior art, the method proposed in the present application can effectively improve the speed and accuracy of photovoltaic power generation unit tracking active up-regulation instruction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic power generation, in particular to a photovoltaic active power up-regulation method based on P-U curve interpolation variable universe fuzzy control. BACKGROUND

[0002] By the end of 2021, the cumulative installed capacity of photovoltaic in China reached 306 million kilowatts, accounting for 12.9% of the total installed capacity of the country. Due to the intermittency and volatility of photovoltaic energy itself, although photovoltaic maximum power point tracking can ensure the maximization of photovoltaic resources, it is easy to cause the adverse phenomenon of full power generation with light and no power generation without light, which is easy to affect the stability of the power grid. With the continuous increase of photovoltaic penetration rate, in addition to the conventional requirements of providing power, the power system also needs photovoltaic to provide some auxiliary functions, including frequency response.

[0003] There are mainly two ways for photovoltaic to participate in power grid frequency regulation, one is to increase energy storage on the photovoltaic side, but the cost of energy storage device is high. The other method is to make the photovoltaic power generation unit work in the power grid dispatching mode, and its output power continuously tracks the active power instruction of the system. The present application proposes a photovoltaic active power fast up-regulation method aiming at the requirement of increasing active power output when the frequency of the power system is lower than the rated frequency. In view of the problem of slow power tracking speed existing in the prior art, a variable universe fuzzy control method based on P-U curve interpolation is proposed, which can realize fast and accurate tracking of the specified active power up-regulation instruction. SUMMARY

[0004] In order to solve the problems mentioned in the background art, the purpose of the present application is to provide a photovoltaic active power up-regulation method based on P-U curve interpolation variable universe fuzzy control.

[0005] The purpose of the present application can be realized by the following technical solutions:

[0006] A photovoltaic active power up-regulation method based on P-U curve interpolation variable universe fuzzy control, characterized in that the method comprises the following steps:

[0007] Step 1: estimate the maximum output power of the photovoltaic power generation unit at present, and then the photovoltaic array receives the active power up-regulation instruction;

[0008] Step 2: quickly up-regulate the current operating point of the photovoltaic power generation unit to the vicinity of the active power up-regulation instruction by variable universe fuzzy control based on P-U curve interpolation;

[0009] Step 3: accurately and smoothly track to the active power up-regulation instruction by small step perturbation observation method in the vicinity of the active power instruction.

[0010] Further, the step 1 by setting the main inverter, so that it is always working in the maximum power point tracking mode, the current photovoltaic power generation unit can be obtained by the maximum power P M .

[0011] Further, the step 1 active up instruction and the maximum power point should satisfy the following relationship to carry out photovoltaic active fast up,

[0012] P PV <P ref <P M

[0013] Where, P PV is the power of the current actual working point of photovoltaic power generation unit, P ref is the active up instruction, P M is the maximum output power of photovoltaic power generation unit.

[0014] Further, the step 2 based on the perturbation voltage step fuzzy control proposes a kind of photovoltaic active fast up method, mark k-1 step voltage variation and k-1 step power variation respectively as follows:

[0015] ΔU k-1 =U k-1 -U k-2 , ΔP k-1 =P k-1 -P ref

[0016] Where, ΔU k-1 is the voltage variation of k-1 step, U k-1 is the voltage of k-1 step, U k-2 is the voltage of k-2 step, ΔP k-1 is the power variation of k-1 step, P k-1 is the power of k-1 step, P ref is the active up instruction.

[0017] Further, the ΔU k-1 and ΔP k-1 are fuzzed as the input of fuzzy controller, and the fuzzy output quantity is obtained according to the designed fuzzy rule, and then the de-fuzzing can obtain the voltage perturbation quantity ΔU k of k step.

[0018] Further, the design of fuzzy rule is as follows: first, the adjustment direction of voltage, i.e. the positive and negative of ΔU k , when increasing voltage leads to P PV close to P ref , or when voltage decreases leads to P PV far away from P refWhen the voltage decreases, the voltage should be increased, i.e. ΔU k > 0; when the voltage decreases, the voltage should be increased, i.e. ΔU PV > 0. ref When the voltage increases, the voltage should be decreased, i.e. ΔU PV < 0. ref < 0. Second, the adjustment range of the voltage, i.e. the size of |ΔU k |, when |ΔP k / ΔU k-1 | is larger, the current working point is still far away from the target point corresponding to the active power up command, at this time, a larger disturbance voltage step |ΔU k-1 | and a larger disturbance voltage domain should be set; when |ΔP k / ΔU k-1 | is smaller, the current working point is already close to the target point corresponding to the active power up command, at this time, a smaller disturbance voltage step |ΔU k-1 | should be set, and the disturbance voltage domain should also be set smaller. k

[0019] Further, the domain contraction method of ΔU k-1 and ΔU k is to perform linear interpolation on the P-U curve to realize variable domain:

[0020]

[0021] wherein U k is the voltage of the kth step, U k-1 is the voltage of the (k-1)th step, U k-2 is the voltage of the (k-2)th step, P k-1 is the power of the (k-1)th step, P k-2 is the power of the (k-2)th step, and P ref is the active power up command.

[0022] Further, the specific method of the variable domain is as follows:

[0023] S1, the first step control, with the known points (U M , P M ) and (U0, P0) on the P-U curve as the base points, a straight line is drawn, and the intersection point of the straight line and the horizontal line P=P ref is (U1, P1), wherein U1 is the first step ΔU k , and the domain interval length is |U0-U1|.

[0024] S2, the kth step control (k>1, k∈N), with the known points (U k-1 , P k-1 ) and (U k-2 , P k-2 ​Draw a straight line with point P as the base point, intersecting the horizontal line P = P. ref The x-coordinate of the intersection point is U k ΔU at step k k The length of the domain interval is |U k-1 -U k |

[0025] Furthermore, in step 3, the condition for switching from variable universe fuzzy control to small-step perturbation observation method to track the power increase command is satisfied by the following equation:

[0026] |ΔP k-1 / ΔU k-1 |<γ

[0027] Wherein, ΔP k-1 Let ΔU be the power change at step k-1. k-1 Let γ be the voltage change at step k-1, and γ be the threshold value for the change. If this formula holds, then the current operating point has been tracked to the vicinity of the target point corresponding to the active power increase command.

[0028] The beneficial effects of this invention are:

[0029] Compared with existing technologies, this invention proposes a photovoltaic active power up-regulation method based on PU curve interpolation and variable universe of discourse fuzzy control, which can effectively improve the speed and accuracy of photovoltaic power generation units in tracking active power up-regulation commands. Specifically, by performing linear interpolation on the PU curve to adaptively modify the disturbance voltage universe of discourse, this method avoids the problem of inaccurate voltage step size generation in the later stages of tracking, which can easily lead to inaccurate power tracking, as is common with traditional fuzzy control with a fixed universe of discourse. Furthermore, it ensures accurate tracking of P at the actual operating point. ref After moving to the vicinity, switch to the small step perturbation observation method to achieve P ref Smooth and accurate tracking. Attached Figure Description

[0030] The invention will now be further described with reference to the accompanying drawings.

[0031] Figure 1 This is a flowchart illustrating the photovoltaic active power up-adjustment method based on PU curve interpolation variable universe fuzzy control as described in this invention.

[0032] Figure 2 This is a schematic diagram illustrating the implementation of variable universe of discourse by linear interpolation on the PU curve according to an embodiment of the present invention;

[0033] Figure 3 This is a structural diagram of a photovoltaic active power rapid up-adjustment based on variable universe fuzzy control using PU curve interpolation, according to an embodiment of the present invention.

[0034] Figure 4 This is a simulation topology diagram of an embodiment of the present invention;

[0035] Figure 5 Power tracking target curve set for the embodiment of the present application;

[0036] Figure 6 Output power curve chart for the embodiment of the present application. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0038] The photovoltaic array of the embodiment is composed of two photovoltaic modules in parallel, and the parameters of a single photovoltaic module are shown in Table 1. A Boost converter is used to realize power control, and the Boost converter includes an input capacitor, an inductor, a switch tube, a diode, an output capacitor and a load, and the specific parameters are shown in Table 2.

[0039] Table 1 Parameters of a single photovoltaic module

[0040]

[0041] Table 2 Parameters of the Boost converter

[0042]

[0043] As shown in Figures 1-4 , a photovoltaic active power up-regulation method based on P-U curve interpolation variable universe fuzzy control, characterized in that the method comprises the following steps:

[0044] Step 1: Estimate the maximum output power that the photovoltaic power generation unit can generate at present, and then the photovoltaic array receives an active power up-regulation instruction;

[0045] Step 2: Quickly up-regulate the current operating point of the photovoltaic power generation unit to the vicinity of the active power up-regulation instruction through variable universe fuzzy control based on P-U curve interpolation;

[0046] Step 3: Accurately and smoothly track to the active power up-regulation instruction through a small-step perturbation observation method in the vicinity of the active power instruction.

[0047] Further, in the step 1, the maximum power P M that the photovoltaic power generation unit can generate at present is obtained by setting the main inverter to always work in the maximum power point tracking mode.

[0048] Further, the active power up-regulation instruction in step 1 and the maximum power point should satisfy the following relationship to perform the fast active power up-regulation of the photovoltaic power generation unit,

[0049] P PV <P ref <P M

[0050] P PV is the power of the current actual working point of the photovoltaic power generation unit, P ref is the active power up-regulation instruction, and P M is the maximum output power of the photovoltaic power generation unit.

[0051] Further, the step 2 proposes a fast active power up-regulation method based on the fuzzy control of the perturbation voltage step, where the voltage change amount of the k-1 step and the power change amount of the k-1 step are respectively:

[0052] ΔU k-1 = U k-1 - U k-2 , and ΔP k-1 = P k-1 - P ref

[0053] ΔU k-1 is the voltage change amount of the k-1 step, U k-1 is the voltage of the k-1 step, U k-2 is the voltage of the k-2 step, ΔP k-1 is the power change amount of the k-1 step, P k-1 is the power of the k-1 step, and P ref is the active power up-regulation instruction.

[0054] Further, after the ΔU k-1 and ΔP k-1 are fuzzified as the inputs of the fuzzy controller, the fuzzy output amount is obtained according to the designed fuzzy rule, and the voltage perturbation amount ΔU k of the k step is obtained after the defuzzification.

[0055] Further, the design of the fuzzy rule is as follows: first, the adjustment direction of the voltage, i.e., the positive and negative of ΔU k , when the increase of the voltage causes P PV to be close to P ref or when the decrease of the voltage causes P PV to be far away from P ref , the voltage should be increased, i.e., ΔU k > 0; when the decrease of the voltage causes P PV to be close to P ref or the increase of the voltage causes P PV to be far away from P refWhen the voltage should be reduced, i.e. ΔU k <0。Second, the adjustment range of the voltage, i.e. |ΔU k |, when |ΔP k-1 / ΔU k-1 | is large, the current operating point is still far from the target point corresponding to the active power up command, at this time, a larger disturbance voltage step |ΔU k | and a larger disturbance voltage domain should be set; when |ΔP k-1 / ΔU k-1 | is small, the current operating point is already close to the target point corresponding to the active power up command, at this time, a smaller disturbance voltage step |ΔU k | should be set, and the disturbance voltage domain should also be set smaller.

[0056] Further, the ΔU k-1 and the domain contraction method of ΔU k , the linear interpolation is implemented on the P-U curve to realize the variable domain:

[0057]

[0058] Wherein, U k is the voltage of the kth step, U k-1 is the voltage of the k-1th step, U k-2 is the voltage of the k-2th step, P k-1 is the power of the k-1th step, P k-2 is the power of the k-2th step, and P ref is the active power up command.

[0059] Further, the specific method of the variable domain is:

[0060] S1, the first step control, with the known points (U M , P M ) and (U0, P0) on the P-U curve as the base points, a straight line is drawn, and the intersection point of the horizontal line P=P ref is U1, the first step ΔU k domain interval length is |U0-U1|;

[0061] S2, the kth step control (k>1, k∈N), with the known points (U k-1 , P k-1 ) and (U k-2 , P k-2 ) on the P-U curve as the base points, a straight line is drawn, and the intersection point of the horizontal line P=P ref is U k , the kth step ΔU k domain interval length is |U k-1 -U k |.

[0062] Furthermore, in step 3, the condition for switching from variable universe fuzzy control to small-step perturbation observation method to track the power increase command is satisfied by the following equation:

[0063] |ΔP k-1 / ΔU k-1 |<γ

[0064] Wherein, ΔP k-1 Let ΔU be the power change at step k-1. k-1 Let γ be the voltage change at step k-1, and γ be the threshold value for the change. If this formula holds, then the current operating point has been tracked to the vicinity of the target point corresponding to the active power increase command.

[0065] like Figure 5 The power tracking target curve shown indicates that the photovoltaic array output power remains at 450W from 0 to 0.5s, and a power increase command is received at 0.5s, requiring the power to be increased to 480W.

[0066] like Figure 6 The diagram shows a comparison of the output curves of a photovoltaic active power increase method based on PU curve interpolation with a variable universe of discourse, and a traditional perturbation-observation method for tracking active power increase commands. The method proposed in this invention can track active power increase commands more quickly compared to the perturbation-observation method.

[0067] In summary, the photovoltaic active power up-regulation method based on PU curve interpolation and variable universe of discourse fuzzy control proposed in this invention can effectively improve the speed and accuracy of photovoltaic power generation units in tracking active power up-regulation commands. By performing linear interpolation on the PU curve to adaptively modify the disturbance voltage universe of discourse, it avoids the problem of inaccurate voltage step size generation in the later stages of tracking, which easily leads to inaccurate power tracking, in traditional fuzzy control with a fixed universe of discourse. Furthermore, it achieves accurate tracking of P at the actual operating point. ref After moving to the vicinity, switch to the small step perturbation observation method to achieve P ref Smooth and accurate tracking.

[0068] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for photovoltaic active power up-adjustment based on PU curve interpolation variable universe fuzzy control, characterized in that, The method includes the following steps: Step 1: Estimate the maximum output power that the photovoltaic power generation unit can currently generate, and then the photovoltaic array receives the active power up-adjustment command; Step 2: Quickly adjust the current operating point of the photovoltaic power generation unit to near the active power increase command by using variable universe fuzzy control based on PU curve interpolation; Step 3: Accurately and smoothly track the active power increase command near the active power command using a small-step perturbation observation method; ΔU k-1 With ΔU k The universe of discourse shrinkage method achieves variable universe of discourse by performing linear interpolation on the PU curve: Where, ΔU k-1 Let ΔU be the voltage change at step k-1. k U is the voltage change at step k. k U is the voltage at step k. k-1 U is the voltage at step k-1. k-2 P is the voltage at step k-2. k-1 P is the power at step k-1. k-2 P is the power at step k-2. ref The order to adjust the position upwards is valid; The specific method for changing the universe of discourse is as follows: S1, First step control, using known points on the PU curve (U M ,P M Draw a straight line with (U0, P0) as the base point, intersecting the horizontal line P = P ref The x-coordinate of the resulting intersection point is U1, and the first step's ΔU k The length of the domain interval is |U0-U1|; S2, Step k control, k>1, k∈N, using the known point (U) on the PU curve. k-1 ,P k-1 ) and (U k-2 ,P k-2 Draw a straight line with point P as the base point, intersecting the horizontal line P = P. ref The x-coordinate of the intersection point is U k ΔU at step k k The length of the domain interval is |U k-1 -U k | 2. The photovoltaic active power up-adjustment method based on PU curve interpolation variable universe fuzzy control according to claim 1, characterized in that, In step 1, the maximum power P that the current photovoltaic power generation unit can generate is obtained by setting the main inverter to always operate in maximum power point tracking mode. M .

3. The photovoltaic active power up-adjustment method based on PU curve interpolation variable universe fuzzy control according to claim 1, characterized in that, In step 1, the active power increase command and the maximum power point should satisfy the following relationship for rapid photovoltaic active power increase: P PV <P ref <P M Among them, P PV P represents the power at the current actual operating point of the photovoltaic power generation unit. M This represents the maximum output power of the photovoltaic power generation unit.

4. The photovoltaic active power up-adjustment method based on PU curve interpolation variable universe fuzzy control according to claim 1, characterized in that, In step 2, a method for rapid up-adjustment of photovoltaic active power is proposed based on fuzzy control of perturbation voltage step size. The voltage change and power change in step k-1 are denoted as follows: DU k-1 = U k-1 -U k-2 ΔP k-1 =P k-1 -P ref Among them, U k-1 U is the voltage at step k-1. k-2 Let ΔP be the voltage at step k-2. k-1 Let P be the power change at step k-1. k-1 This represents the power at step k-1.

5. The photovoltaic active power up-adjustment method based on PU curve interpolation variable universe fuzzy control according to claim 4, characterized in that, The ΔU k-1 and ΔP k-1 After being fuzzified as input to the fuzzy controller, the fuzzy output is obtained according to the designed fuzzy rules. After defuzzification, the voltage disturbance ΔU at step k can be obtained. k .

6. The photovoltaic active power up-adjustment method based on PU curve interpolation variable universe fuzzy control according to claim 5, characterized in that, The design of the fuzzy rule is as follows: First, the direction of voltage adjustment, i.e., ΔU k The sign of P, when the voltage is increased, causes PV Near P ref When or when the voltage decreases, causing P PV Stay away from P ref When this happens, the voltage should be increased, i.e., ΔU k >0; when the voltage decreases, P PV Near P ref When or when the voltage increases, P PV Stay away from P ref When this happens, the voltage should be reduced, i.e., ΔU k <0; Second, the adjustment range of the voltage, i.e., |ΔU k The magnitude of | when |ΔP k-1 / ΔU k-1 When the value is large, the current operating point is still far from the target point corresponding to the active power increase command. In this case, a larger disturbance voltage step size should be set. k |and a larger disturbance voltage domain; when |ΔP k-1 / ΔU k-1 When the value is small, the current operating point is already close to the target point corresponding to the active power increase command. In this case, a smaller disturbance voltage step size should be set. k Its disturbance voltage domain should also be set to a smaller value.

7. The photovoltaic active power up-adjustment method based on PU curve interpolation variable universe fuzzy control according to claim 1, characterized in that, In step 3, the condition for switching from variable universe fuzzy control to small-step perturbation observation method to track the power increase command is that the following equation is satisfied: |ΔP k-1 / D k-1 |<c Where, ΔP k-1 Let ΔU be the power change at step k-1. k-1 Let γ be the voltage change at step k-1, and γ be the threshold value for the change. If this formula holds, then the current operating point has been tracked to the vicinity of the target point corresponding to the active power increase command.

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