Regional power grid primary frequency modulation-oriented photovoltaic reserve capacity fine management control strategy

Abstract

The invention belongs to the technical field of power systems, and particularly relates to a photovoltaic reserve capacity fine management control strategy for primary frequency modulation of a regional power grid. The invention provides a regional power grid primary frequency modulation-oriented photovoltaic reserve capacity fine management control strategy aiming at the problems of reserve capacity redundancy, insufficient frequency modulation capability and the like of the current photovoltaic load shedding frequency modulation control strategy. Firstly, a photovoltaic load shedding system participates in a control architecture of primary frequency modulation of a regional power grid; secondly, proposing a primary frequency modulation required power calculation method of the photovoltaic load shedding system, and proposing a fine management strategy that the photovoltaic reserve capacity participates in primary frequency modulation based on the calculation method; and finally, providing a photovoltaic load shedding control strategy solving method.

Description

Technical Field

[0001] The present invention belongs to the technical field of power systems, and in particular relates to a refined management and control strategy for photovoltaic backup capacity for primary frequency regulation of a regional power grid. Background Art

[0002] Renewable energy technologies are rapidly developing, with the continued decline in photovoltaic power generation costs showing strong growth potential in the power sector. However, photovoltaic power generation faces a series of new challenges when connecting to the grid. Because it is a stationary component connected to the grid through power electronics, it lacks rotating elements like generators. This leads to the loss of rotational kinetic energy, reduced energy reserves, and potential problems with system transient stability. Furthermore, the increasing number of distributed generators (DGs) is also putting pressure on the stability of traditional power grids.

[0003] To overcome these problems, current research, both domestically and internationally, falls into two main categories: one is to pair photovoltaic systems with energy storage systems, creating a virtual synchronous generator (VSG). This allows the photovoltaic system to mimic a traditional rotating synchronous generator, exhibiting high inertia and strong damping. This allows the photovoltaic system to spontaneously provide inertia support without relying on a frequency controller. However, energy storage is relatively expensive and uneconomical, making large-scale investment unviable. The other is to operate the photovoltaic system in a load-shedding manner, where the photovoltaic system outputs power at a ratio of a reserved fixed capacity or maximum power. While this reduces investment costs, it also increases curtailed economic light losses and reduces the utilization rate of renewable energy. Therefore, to address these issues, developing a primary frequency modulation control strategy for photovoltaic load shedding has practical application value. Summary of the Invention

[0004] In response to the above, the technical problem addressed by this invention is to provide a photovoltaic load-shedding control strategy for regional power grid primary frequency regulation. To this end, we first propose a control architecture for a photovoltaic load-shedding system participating in regional power grid primary frequency regulation. Next, we propose a method for calculating the power required for primary frequency regulation in the photovoltaic load-shedding system. Based on this, we propose a method for solving the photovoltaic load-shedding control strategy.

[0005] In order to achieve the above object, the technical solution provided by the present invention is as follows:

[0006] A photovoltaic load reduction control strategy for primary frequency regulation of a regional power grid, the method comprising the following steps:

[0007] Step (1) proposes a control architecture for the photovoltaic load reduction system to participate in the primary frequency regulation of the regional power grid;

[0008] Step (2) proposes a method for calculating the primary frequency regulation power requirement of the photovoltaic load reduction system;

[0009] Step (3) proposes a refined management strategy for photovoltaic reserve capacity to participate in primary frequency regulation;

[0010] Step (4) proposes a solution method for photovoltaic load reduction control strategy;

[0011] The specific method of the control architecture of the photovoltaic load reduction system participating in the primary frequency regulation of the regional power grid in step (1) is as follows:

[0012] 1. Equipment level

[0013] Photovoltaics are connected to the public bus through converters and transformers to cope with frequency fluctuations caused by load changes.

[0014] 2. Control plane

[0015] The system's required photovoltaic power P is calculated based on the frequency signal f after primary frequency modulation of the traditional power supply and the active power-frequency characteristic curve of the photovoltaic backup capacity.

[0016] By real-time monitoring of environmental factors and considering the impact of uncertainty on photovoltaic output, the photovoltaic reserve capacity, that is, the photovoltaic load reduction power, and the photovoltaic load reduction rate x at each moment are determined. i According to the photovoltaic frequency regulation integrated control strategy and the system frequency signal f, combined with the required power P, the actual photovoltaic output P is determined. a .

[0017] The specific method for calculating the primary frequency regulation power requirement of the photovoltaic load reduction system in step (2) is as follows:

[0018] The PV reserve capacity is calculated by simulating the droop characteristics of the synchronous machine to determine the PV primary frequency regulation power requirement. That is, the output requirement is determined based on the system frequency deviation and the PV reserve load shedding-droop characteristic curve. This yields the functional relationship between the system's PV reserve power requirement and the frequency deviation:

[0019]

[0020] Where: P i is the photovoltaic primary frequency regulation power required at the i-th moment; f i is the frequency at the i-th moment; f db2 、f db1 is the upper and lower limits of the frequency regulation dead zone; k is the photovoltaic load reduction droop coefficient. From this formula, we can see that when f i <f db1 When P i >0, photovoltaic power generation should be increased; when f i >f db2 When P i <0, photovoltaic power output should be reduced.

[0021] The specific method of the refined management strategy of photovoltaic spare capacity participating in primary frequency regulation in step (3) is as follows:

[0022] First, the light intensity within a frequency modulation cycle is given, and then the maximum photovoltaic output P at the corresponding moment is obtained. pvi , Secondly, five modes of power control strategy for photovoltaic backup capacity are designed, and the variable P is introduced low 、P high , indicating the lower and upper values of the PV backup capacity, the following control strategies are adopted in each mode:

[0023] Normal FM mode: When the frequency f i <f db1 When P pvi ·x i >P low And P i <P pvi ·x i When the frequency f i >f db2 When P pvi ·x i >P low And-P i <P pvi ·(0.9-x i ), the photovoltaic power is controlled to reduce output, and its power instruction is shown in formula (1).

[0024] Economic penalty mode: When the frequency f i <f db1 When P pvi ·x i >P low And P i >P pvi ·x i When all the photovoltaic reserve capacity participates in the primary frequency regulation, it will then operate at maximum power. For the remaining load, the photovoltaic reserve capacity cannot participate in the primary frequency regulation and must accept the relevant power shortage economic penalty. When the frequency f i >f db2 When P pvi ·x i >P low And-P i >P pvi ·(0.9-x i ), the photovoltaic power station should reduce its output to the maximum extent possible and then operate at the specified minimum power. The remaining load should be absorbed by energy-consuming resistors, and the photovoltaic power station should accept the relevant economic penalties for power abandonment.

[0025] Add discharge mode: If f i In the FM dead zone fdb Internal time, that is, f db1 <f i <f db2 When P high <P pvi ·x i <P N When f i <0, control the photovoltaic power to increase output, the power is recorded as P d , need to optimize the selection.

[0026] Reduced discharge mode: If f i In the FM dead zone f db Internal time, that is, f db1 <f i <f db2 When 0 <P pvi ·x i <P low When f i >0, control the photovoltaic power to reduce output, the power is recorded as P c , need to optimize the selection.

[0027] Photovoltaic standby mode: If f i In the FM dead zone f db Internal time, that is, f db1 <f i <f db2 When P high <P pvi ·x i <P N When f i >0, control photovoltaic not to participate in frequency regulation; when 0 <P pvi ·x i <P low When f i <0, control photovoltaic not to participate in frequency regulation. low <P pvi ·x i <P high When , the photovoltaic power is controlled not to participate in frequency regulation.

[0028] The specific method for solving the photovoltaic load reduction control strategy in step (4) is as follows:

[0029] The particle swarm algorithm is used to solve the optimized frequency sequence, load reduction rate curve and other related parameters.

[0030] Compared with existing technical solutions, this invention offers the advantage of enabling refined management of PV reserve capacity while meeting the frequency regulation requirements of the regional power grid system. This approach not only addresses frequency disturbances in the system but also enables additional frequency regulation when the frequency falls within dead zones to ensure frequency regulation margin, thus possessing considerable practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of photovoltaic primary frequency regulation system structure

[0032] Figure 2 Photovoltaic load shedding-droop characteristic curve

[0033] Figure 3 Light intensity curve DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0035] To address the problems of redundant spare capacity and insufficient frequency modulation capacity in traditional photovoltaic spare capacity frequency modulation control strategies, the present invention designs a photovoltaic spare capacity refined management and control strategy for primary frequency modulation of regional power grids, including the following steps:

[0036] Step (1) proposes a control architecture for the photovoltaic load reduction system to participate in the primary frequency regulation of the regional power grid;

[0037] Step (2) proposes a method for calculating the primary frequency regulation power requirement of the photovoltaic load reduction system;

[0038] Step (3) proposes a refined management strategy for photovoltaic reserve capacity to participate in primary frequency regulation;

[0039] Step (4) proposes a solution method for photovoltaic load reduction control strategy;

[0040] The specific method of the control architecture of the photovoltaic load reduction system participating in the primary frequency regulation of the regional power grid in step (1) is as follows:

[0041] 1. Equipment level

[0042] The regional power grid system with photovoltaic as the main power source has a system structure such as Figure 1 Photovoltaic power is connected to the public bus through converters and transformers to cope with frequency fluctuations caused by load changes.

[0043] 2. Control plane

[0044] The system's required photovoltaic power P is calculated based on the frequency signal f after primary frequency modulation of the traditional power supply and the active power-frequency characteristic curve of the photovoltaic backup capacity.

[0045] By real-time monitoring of environmental factors and considering the impact of uncertainty on photovoltaic output, the photovoltaic reserve capacity, that is, the photovoltaic load reduction power, and the photovoltaic load reduction rate x at each moment are determined. i According to the photovoltaic frequency regulation integrated control strategy and the system frequency signal f, combined with the required power P, the actual photovoltaic output P is determined.a .

[0046] The specific method for calculating the primary frequency regulation power requirement of the photovoltaic load reduction system in step (2) is as follows:

[0047] The primary frequency of the photovoltaic system mainly uses the photovoltaic reserve capacity to simulate the active power droop characteristics of the synchronous machine primary frequency regulation. The specific principle is as follows: Figure 2 As shown. P1 is the maximum power that photovoltaic power can provide; P2 is the output power after load reduction operation; P3 is the minimum power that photovoltaic power can provide; Δf db2 , Δf db1 are the upper and lower limits of the frequency dead zone; Δf2 and Δf1 are the upper and lower limits of the frequency regulation output set for PV standby frequency regulation. The PV standby capacity is calculated by simulating the droop characteristics of the synchronous machine to calculate the PV primary frequency regulation power demand. This means that the output demand is determined based on the system frequency deviation and the PV standby load shedding-droop characteristic curve. This yields the functional relationship between the system's PV standby power demand and the frequency deviation:

[0048]

[0049] Where: P i is the photovoltaic primary frequency regulation power required at the i-th moment; f i is the frequency at the i-th moment; f db2 、f db1 is the upper and lower limits of the frequency regulation dead zone; k is the photovoltaic load reduction droop coefficient. From this formula, we can see that when f i <f db1 When P i >0, photovoltaic power generation should be increased; when f i >f db2 When P i <0, photovoltaic power output should be reduced.

[0050] The specific method of the refined management strategy of photovoltaic spare capacity participating in primary frequency regulation in step (3) is as follows:

[0051] First, the light intensity within a frequency modulation cycle is given, such as Figure 3 Take the example, and then find the maximum photovoltaic output P at the corresponding moment. pvi , Secondly, five modes of power control strategy for photovoltaic backup capacity are designed, and the variable P is introduced low 、P high , indicating the lower and upper values of the PV backup capacity, the following control strategies are adopted in each mode:

[0052] Normal FM mode: When the frequency f i <f db1 When P pvi ·x i >Plow And P i <P pvi ·x i When the frequency f i >f db2 When P pvi ·x i >P low And-P i <P pvi ·(0.9-x i ), the photovoltaic power is controlled to reduce output, and its power instruction is shown in formula (1).

[0053] Economic penalty mode: When the frequency f i <f db1 When P pvi ·x i >P low And P i >P pvi ·x i When all the photovoltaic reserve capacity participates in the primary frequency regulation, it will then operate at maximum power. For the remaining load, the photovoltaic reserve capacity cannot participate in the primary frequency regulation and must accept the relevant power shortage economic penalty. When the frequency f i >f db2 When P pvi ·x i >P low And-P i >P pvi ·(0.9-x i ), the photovoltaic power station should reduce its output to the maximum extent possible and then operate at the specified minimum power. The remaining load should be absorbed by energy-consuming resistors, and the photovoltaic power station should accept the relevant economic penalties for power abandonment.

[0054] Add discharge mode: If f i In the FM dead zone f db Internal time, that is, f db1 <f i <f db2 When P high <P pvi ·x i <P N When f i <0, control the photovoltaic power to increase output, the power is recorded as P d , need to optimize the selection.

[0055] Reduced discharge mode: If f i In the FM dead zone f db Internal time, that is, f db1 <f i <f db2 When 0 <Ppvi ·x i <P low When f i >0, control the photovoltaic power to reduce output, the power is recorded as P c , need to optimize the selection.

[0056] Photovoltaic standby mode: If f i In the FM dead zone f db Internal time, that is, f db1 <f i <f db2 When P high <P pvi ·x i <P N When f i >0, control photovoltaic not to participate in frequency regulation; when 0 <P pvi ·x i <P low When f i <0, control photovoltaic not to participate in frequency regulation. low <P pvi ·x i <P high When , the photovoltaic power is controlled not to participate in frequency regulation.

[0057] The specific method for solving the photovoltaic load reduction control strategy in step (4) is as follows:

[0058] The particle swarm algorithm is used to solve the optimized frequency sequence, load reduction rate curve and other related parameters.

[0059] In summary, after adopting the photovoltaic backup capacity refined management and control strategy proposed in this paper, the backup capacity of the photovoltaic frequency regulation system is optimized and the frequency regulation stability of the system is improved to a certain extent.

[0060] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A refined management and control strategy for photovoltaic backup capacity for primary frequency regulation of regional power grids, characterized by: The method comprises the following steps: Step (1) proposes a control architecture for the photovoltaic load reduction system to participate in the primary frequency regulation of the regional power grid; Step (2) proposes a method for calculating the primary frequency regulation power requirement of the photovoltaic load reduction system; Step (3) proposes a refined management strategy for photovoltaic reserve capacity to participate in primary frequency regulation; Step (4) proposes a solution method for photovoltaic load reduction control strategy.

2. The method according to claim 1, wherein: The specific method of the control architecture of the photovoltaic load reduction system participating in the primary frequency regulation of the regional power grid in step (1) is as follows: (1) Equipment level Photovoltaics are connected to the public bus through converters and transformers to cope with frequency fluctuations caused by load changes. (2) Control layer The system's required photovoltaic power P is calculated based on the frequency signal f after primary frequency modulation of the traditional power supply and the active power-frequency characteristic curve of the photovoltaic backup capacity. By real-time monitoring of environmental factors and considering the impact of uncertainty on photovoltaic output, the photovoltaic reserve capacity, that is, the photovoltaic load reduction power, and the photovoltaic load reduction rate x at each moment are determined. i According to the photovoltaic frequency regulation integrated control strategy and the system frequency signal f, combined with the required power P, the actual photovoltaic output P is determined. a .

3. The method according to claim 1, wherein: The specific method for calculating the primary frequency regulation power requirement of the photovoltaic load reduction system in step (2) is as follows: The PV reserve capacity is calculated by simulating the droop characteristics of the synchronous machine to determine the PV primary frequency regulation power requirement. That is, the output requirement is determined based on the system frequency deviation and the PV reserve load shedding-droop characteristic curve. From this, the functional relationship between the system's PV reserve power requirement and the frequency deviation can be obtained: Where: P i is the photovoltaic primary frequency regulation power required at the i-th moment; f i is the frequency at the i-th moment; f db2 、f db1 is the upper and lower limits of the frequency regulation dead zone; k is the photovoltaic load reduction droop coefficient. From this formula, we can see that when f i <f db1 When P i >0, photovoltaic power generation should be increased; when f i >f db2 When P i <0, photovoltaic power output should be reduced.

4. The method according to claim 1, wherein: The specific method of the refined management strategy for the photovoltaic reserve capacity to participate in primary frequency regulation in step (3) is as follows: First, the light intensity within a frequency modulation cycle is given, and then the maximum photovoltaic output P at the corresponding moment is obtained. pvi , Secondly, five modes of power control strategy for photovoltaic backup capacity are designed, and the variable P is introduced low 、P high , indicating the lower and upper values of the PV backup capacity, the following control strategies are adopted in each mode: Normal FM mode: When the frequency f i <f db1 When P pvi ·x i >P low And P i <P pvi ·x i When the frequency f i >f db2 When P pvi ·x i >P low And-P i <P pvi ·(0.9-x i ), the photovoltaic power is controlled to reduce output, and its power instruction is specifically shown in formula (1). Economic penalty mode: When the frequency f i <f db1 When P pvi ·x i >P low And P i >P pvi ·x i When all the photovoltaic reserve capacity participates in the primary frequency regulation, it will then operate at maximum power. For the remaining load, the photovoltaic reserve capacity cannot participate in the primary frequency regulation and must accept the relevant power shortage economic penalty. When the frequency f i >f db2 When P pvi ·x i >P low And-P i >P pvi ·(0.9-x i ), the photovoltaic power station should reduce its output to the maximum extent possible and then operate at the specified minimum power. The remaining load should be absorbed by energy-consuming resistors, and the photovoltaic power station should accept the relevant economic penalties for power abandonment. Add discharge mode: If f i In the FM dead zone f db Internal time, that is, f db1 <f i <f db2 , when P high <P pvi ·x i <P N When f i <0, control the photovoltaic power to increase output, the power is recorded as P d , need to optimize the selection. Reduced discharge mode: If f i In the FM dead zone f db Internal time, that is, f db1 <f i <f db2 , when 0 <P pvi ·x i <P low When f i >0, control the photovoltaic power to reduce output, the power is recorded as P c , need to optimize the selection. Photovoltaic standby mode: If f i In the FM dead zone f db Internal time, that is, f db1 <f i <f db2 , when P high <P pvi ·x i <P N When f i >0, control photovoltaic not to participate in frequency regulation; when 0 <P pvi ·x i <P low When f i <0, control photovoltaic not to participate in frequency regulation. low <P pvi ·x i <P high When , the photovoltaic power is controlled not to participate in frequency regulation.

5. The method according to claim 1, wherein: The specific method for solving the photovoltaic load reduction control strategy in step (4) is as follows: The particle swarm algorithm is used to solve the optimized frequency sequence, load reduction rate curve and other related parameters.

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