Optical storage new energy station distributed flexible load inertia optimization control strategy

Abstract

The invention discloses a distributed flexible load inertia optimization control strategy for a light storage new energy field station, and belongs to the field of photovoltaic energy storage system cooperative network construction control, and the strategy comprises the following steps: S1, measuring and obtaining the input power, the network side output power and the frequency information of each light storage converter in the current field station; s2, according to the network side frequency change, the required source side input power is adjusted in real time in combination with a network construction control strategy adopted by the optical storage converter; s3, adjusting the input power of the source side in real time through the access and cut-out of the flexible load, and achieving the inertia support of the frequency of the network side under the frequency event; and S4, according to the steps S2 and S3, flexible load inertia optimization control based on energy balance is realized. According to the method, the problem that the power grid frequency supporting capacity is weak due to large energy storage power fluctuation and slow response is effectively solved, the situation of frequent charging and discharging during energy storage stabilizing power fluctuation is avoided through the flexible load access / cut-out control logic, and the operation reliability of a new energy station is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic energy storage system collaborative networking control, and in particular to a distributed flexible load inertia optimization control strategy for photovoltaic energy storage new energy stations. Background Art

[0002] At present, renewable energy is gradually replacing traditional fossil energy, and the scale of new energy power generation in new power systems is rapidly expanding. The large-scale integration of new energy represented by photovoltaics has caused the power system to gradually shift from a system dominated by synchronous machines to a system dominated by power electronics. In order to cope with the problems such as low inertia caused by large-scale integration of photovoltaics and provide the necessary frequency support for the power grid, network control has been widely used due to its unique advantages. In addition, photovoltaic systems are easily affected by environmental changes, and there is a large uncertainty in their output power. Therefore, energy storage systems are usually used to suppress power fluctuations in photovoltaic systems and provide additional energy for frequency support.

[0003] However, under this system architecture, when a frequency event occurs on the grid side, its output power is completely determined by the power response curve introduced by the grid control structure. It is easy for the input on the source side to not match the power supplied on the grid side, which in turn causes drastic changes in the grid side frequency, which is not conducive to the stable operation of the system. Summary of the invention

[0004] The purpose of the present invention is to provide a distributed flexible load inertia optimization control strategy for photovoltaic and energy storage new energy stations, which can solve the problem of lack of effective controllable inertia support in new energy stations in the prior art, and effectively improve the problem of weak grid frequency support capability caused by large fluctuations in energy storage power and slow response. At the same time, the control logic of flexible load access / disconnection can avoid frequent charging and discharging when energy storage is used to smooth power fluctuations, effectively improving the reliability of new energy station operation.

[0005] To achieve the above objectives, the present invention provides a distributed flexible load inertia optimization control strategy for a photovoltaic energy storage new energy station, comprising the following steps: S1. Measure and obtain the input power, grid-side output power and frequency information of each photovoltaic storage converter in the current station; S2, according to the frequency change on the grid side, combined with the grid control strategy adopted by the photovoltaic storage converter, the required source side input power is adjusted in real time; S3: By connecting and disconnecting flexible loads, the source-side input power is adjusted in real time to achieve inertia support of the grid-side frequency during frequency events; S4. According to steps S2 and S3, flexible load inertia optimization control based on energy balance is implemented.

[0006] Preferably, in S2, the method for real-time calculation of source-side input power based on grid-side frequency change specifically includes the following steps: S21, by measuring the grid-side output voltage and current , calculate the instantaneous active power output on the grid side p o , the formula is as follows: ; S22. Combined with the network control strategy containing virtual inertia support, the frequency curve of the station is constrained when a frequency event occurs on the grid side; S23. Based on the site frequency curve and the power-frequency support relationship, adjust the required source-side input power.

[0007] Preferably, in S22, when a frequency event occurs on the grid side, the instantaneous rate of change of the frequency is calculated by the virtual synchronous machine control structure. , the change rate is related to the active reference value P * and the actual output active p o The difference is positively correlated with the virtual moment of inertia J Inversely proportional to the frequency; To ensure the safe operation of the network equipment, the absolute value of the instantaneous change rate of the network side frequency does not exceed the set value, which is recorded as .

[0008] Preferably, in S23, in order to ensure that the instantaneous rate of change of the grid-side frequency is controllable, the output power needs to be adjusted in multiple stages, and the actual output active power is controlled by adjusting the source-side input power.

[0009] Preferably, in S3, the flexible load connection and disconnection scheme specifically includes the following steps: S31. By comparing the original input power on the source side with the required input power, the value of the flexible load connection or cut-out power is determined to achieve virtual inertia support under frequency drop and avoid excessive frequency changes causing system instability; S32. Based on the current working status of each converter and flexible load in the station, determine the specific flexible load connection or disconnection plan.

[0010] Preferably, in S32, to ensure that the absolute value of the instantaneous change rate of the grid-side frequency does not exceed the set value , multiple access or disconnection operations are required at regular intervals.

[0011] Therefore, the beneficial effects of the above-mentioned distributed flexible load inertia optimization control strategy of the photovoltaic storage new energy station adopted by the present invention are as follows: (1) This control solves the problem of the lack of effective controllable inertia support in new energy stations in the existing technology, and effectively improves the problem of weak grid frequency support capability caused by large fluctuations in energy storage power and slow response.

[0012] (2) The control logic of flexible load connection / disconnection avoids the frequent charging and discharging of energy storage to smooth power fluctuations, effectively improving the reliability of new energy station operation.

[0013] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a step diagram of an embodiment of a distributed flexible load inertia optimization control strategy for a photovoltaic energy storage new energy station of the present invention; Figure 2 This is a schematic diagram of the photovoltaic storage new energy station architecture of the present invention; Figure 3 It is a block diagram of the active power control loop of the virtual synchronous machine of the present invention; Figure 4 Schematic diagram of the flexible load switching-in and switching-out scheme under frequency events of the present invention, wherein (a) is a frequency drop; (b) is a frequency increase; Figure 5 The frequency response curve of the station when the frequency drops, where (a) is the traditional solution; (b) is the solution of this embodiment; Figure 6 The power response curve of the station when the frequency drops, where (a) is the traditional solution; (b) is the solution of this embodiment; Figure 7 The frequency response curve of the station when the frequency rises, where (a) is the traditional solution; (b) is the solution of this embodiment; Figure 8 The power response curve of the station when the frequency rises, where (a) is the traditional solution and (b) is the solution of this embodiment. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0016] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0017] Embodiment 1 The present invention provides a distributed flexible load inertia optimization control strategy for photovoltaic and energy storage new energy stations. Figure 1 In the station architecture shown in the figure, the DC / AC converter adopts Figure 2 The virtual synchronous machine control strategy shown in FIG. 1 includes the following steps: Figure 3 As shown: S1. Measure and obtain the input power, grid-side output power and frequency information of each photovoltaic storage converter in the current site.

[0018] S2. According to the frequency change on the grid side and combined with the network control strategy adopted by the photovoltaic storage converter, the required source side input power is adjusted in real time.

[0019] The real-time calculation method of the source side input power based on the grid side frequency change specifically includes the following steps: S21, by measuring the grid-side output voltage and current , calculate the instantaneous active power output on the grid side p o , the formula is as follows: ; S22, combined with the network control strategy containing virtual inertia support (such as virtual synchronous machine control, its structure is as follows Figure 2 As shown, the active power reference value P * Given by the superior dispatcher, and ω Represent the rated angular frequency and actual angular frequency of the power grid respectively, J , D p denote the virtual moment of inertia and damping coefficient respectively, θis the grid voltage phase angle), and constrains the frequency curve of the station when a frequency event occurs on the grid side. When a frequency event occurs on the grid side, the instantaneous rate of change of the frequency is calculated through the virtual synchronous machine control structure. , the change rate is related to the active reference value P * and the actual output active p o The difference is positively correlated with the virtual moment of inertia J Inversely proportional to the frequency; To ensure the safe operation of the network equipment, the absolute value of the instantaneous change rate of the network side frequency does not exceed the set value, which is recorded as .

[0020] S23. Based on the site frequency curve and the power-frequency support relationship, adjust the required source-side input power.

[0021] In order to ensure that the instantaneous change rate of the grid-side frequency is controllable, the output power needs to be adjusted in multiple stages, and the actual output active power can be controlled by adjusting the input power on the source side.

[0022] S3. By connecting and disconnecting flexible loads, the input power on the source side is adjusted in real time to achieve inertia support for the grid-side frequency during frequency events.

[0023] The flexible load connection and disconnection scheme specifically includes the following steps: S31. By comparing the original input power on the source side with the required input power, the value of the flexible load connection or cut-out power is determined to achieve virtual inertia support under frequency drop and avoid system instability caused by excessive frequency changes.

[0024] S32. Based on the current working status of each converter and flexible load in the station, determine the specific flexible load connection or disconnection plan.

[0025] To ensure that the absolute value of the instantaneous change rate of the grid-side frequency does not exceed the set value , multiple access or cut-out operations need to be performed at regular intervals. The schematic diagram of this solution is as follows Figure 4 shown.

[0026] S4. According to steps S2 and S3, flexible load inertia optimization control based on energy balance is implemented.

[0027] For comparison, Figure 5-8 The conventional solution and the solution of this embodiment are respectively given (such as Figure 4 (as shown in the figure) shows the frequency response curve and power response curve of the station when a frequency event occurs.

[0028] (1) Frequency drop: When the time is 20 s, a frequency event occurs on the grid side due to the connection of additional loads, and the station frequency starts to drop from 50 Hz in the normal working mode. Under the traditional scheme, the station does not constrain the input power curve on the source side. Therefore, the actual output power on the grid side is completely determined by the virtual synchronous machine control strategy, which causes a large transient overshoot in the output power of the station and causes the lowest point of the frequency curve to drop, such as Figure 5 a and Figure 6 As shown in a in . In this embodiment, the station constrains the input power curve on the source side, and the actual output power on the grid side is determined by the virtual synchronous machine control and the input power curve on the source side. When a frequency event occurs, the flexible load on the source side is switched on and off to achieve a smooth response of the station frequency and output power while ensuring the same inertia support (i.e., almost the same frequency change rate). Compared with the traditional solution, this embodiment significantly improves the lowest frequency point and suppresses power overshoot, see Figure 5 b and Figure 6 b in.

[0029] (2) Frequency rise: When the time is 20 s, a frequency event occurs on the grid side due to load shedding, and the station frequency starts to rise from 50 Hz in the normal working mode. Under the traditional scheme, the output power of the station still has a large transient overshoot, which causes the highest point of the frequency curve to climb, such as Figure 7 a and Figure 8 As shown in a in . In this embodiment, the station constrains the input power curve on the source side. When a frequency event occurs, the station frequency and output power are smoothly responded by switching in and out of the flexible load on the source side while ensuring the same inertia support (i.e., almost the same frequency change rate). Compared with the traditional solution, this embodiment significantly lowers the highest frequency point and suppresses power overshoot, see Figure 7 b and Figure 8 b in.

[0030] In summary, this embodiment plans the flexible load access / disconnection through the station-level inertia demand, and can ensure the balance between the power input on the source side and the power output on the grid side while avoiding drastic frequency changes, thereby realizing the flexible load inertia optimization control based on energy balance.

[0031] Therefore, the present invention adopts the above-mentioned distributed flexible load inertia optimization control strategy for photovoltaic and energy storage new energy stations, which solves the problem of lack of effective controllable inertia support in new energy stations in the prior art, and effectively improves the problem of weak grid frequency support capability caused by large fluctuations in energy storage power and slow response. At the same time, the control logic of flexible load access / disconnection avoids frequent charging and discharging when energy storage smoothes power fluctuations, effectively improving the reliability of new energy station operation.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A distributed flexible load inertia optimization control strategy for photovoltaic and energy storage new energy stations, characterized in that: The following steps are involved: S1. Measure and obtain the input power, grid-side output power and frequency information of each photovoltaic storage converter in the current station; S2, according to the frequency change on the grid side, combined with the grid control strategy adopted by the photovoltaic storage converter, the required source side input power is adjusted in real time; S3: By connecting and disconnecting flexible loads, the source-side input power is adjusted in real time to achieve inertia support of the grid-side frequency during frequency events; S4. According to steps S2 and S3, flexible load inertia optimization control based on energy balance is implemented.

2. According to claim 1, a distributed flexible load inertia optimization control strategy for photovoltaic and energy storage stations is characterized by: In S2, the real-time calculation method of the source side input power based on the grid side frequency change specifically includes the following steps: S21, by measuring the grid-side output voltage and current , calculate the instantaneous active power output on the grid side p o , the formula is as follows: ； S22. Combined with the network control strategy containing virtual inertia support, the frequency curve of the station is constrained when a frequency event occurs on the grid side; S23. Based on the site frequency curve and the power-frequency support relationship, adjust the required source-side input power.

3. According to claim 2, a distributed flexible load inertia optimization control strategy for photovoltaic and energy storage stations is characterized by: In S22, when a frequency event occurs on the grid side, the instantaneous rate of change of frequency is calculated through the virtual synchronous machine control structure. , the change rate is related to the active reference value P * and the actual output active p o The difference is positively correlated with the virtual moment of inertia J Inversely proportional to the frequency; To ensure the safe operation of the network equipment, the absolute value of the instantaneous change rate of the network side frequency does not exceed the set value, which is recorded as .

4. According to claim 2, a distributed flexible load inertia optimization control strategy for photovoltaic and energy storage stations is characterized by: In S23, in order to ensure that the instantaneous change rate of the grid-side frequency is controllable, the output power needs to be adjusted in multiple stages, and the actual output active power is controlled by adjusting the input power on the source side.

5. According to claim 1, a distributed flexible load inertia optimization control strategy for photovoltaic and energy storage stations is characterized by: In S3, the flexible load connection and disconnection scheme specifically includes the following steps: S31. By comparing the original input power on the source side with the required input power, the value of the flexible load connection or cut-out power is determined to achieve virtual inertia support under frequency drop and avoid excessive frequency changes causing system instability; S32. Based on the current working status of each converter and flexible load in the station, determine the specific flexible load connection or disconnection plan.

6. According to claim 5, a distributed flexible load inertia optimization control strategy for photovoltaic and energy storage stations is characterized by: In S32, to ensure that the absolute value of the instantaneous change rate of the grid-side frequency does not exceed the set value , multiple access or disconnection operations are required at regular intervals.

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