Grid-connected self-adaptive energy storage control device for active photovoltaic court of rural power grid

Abstract

The invention provides a grid-connected self-adaptive energy storage control device for an active photovoltaic area of a rural power grid. The grid-connected self-adaptive energy storage control device comprises a photovoltaic unit, a photovoltaic inverter, an energy storage converter, an energy storage unit and an intelligent control cabinet, the intelligent control cabinet comprises a data acquisition module, a mode switching module and a self-adaptive control module; the data acquisition module is used for detecting a voltage value and a current value of a low-voltage outgoing line side of the transformer area; the mode switching module is used for switching three operation modes of grid connection, off-grid and light storage island; the self-adaptive control module is used for dynamically adjusting the energy storage charging and discharging power Pess based on the voltage deviation delta U; according to the invention, the data acquisition module of the intelligent control cabinet can monitor the current and voltage of the active photovoltaic area of the rural power grid in real time, can automatically switch the operation mode according to the state of the power grid, and dynamically adjusts the charging and discharging power of the energy storage unit, thereby improving the power supply quality and reliability. The problems of insufficient power supply capability, low voltage and the like of rural power distribution networks are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power system automation, and particularly relates to a rural network active photovoltaic substation area grid-connected adaptive energy storage control device. BACKGROUND

[0002] After the distributed photovoltaic is accessed to the rural distribution network, the fluctuation of the generated power directly affects the voltage at the access point. When the light is sufficient, the high power may make the voltage exceed the rated range, resulting in voltage rise. When the light is insufficient or at night, the power reduction may cause voltage drop, affecting the power supply quality. The instability of the voltage not only reduces the power quality, but also may cause damage to the power grid equipment, and even trigger the misoperation of the protection device.

[0003] And the rural network active photovoltaic substation area causes the voltage to be lower than 198V at the trough of photovoltaic output due to long line, thin line diameter and large load fluctuation, the transformer is overloaded at the load peak period, and the voltage is out of limit during the noon photovoltaic generation.

[0004] Therefore, it is necessary to design a rural network active photovoltaic substation area grid-connected adaptive energy storage control device capable of solving the problems of insufficient power supply capacity and low voltage of the rural distribution network to solve the technical problems currently faced. SUMMARY

[0005] In view of the deficiencies in the prior art, the application provides a rural network active photovoltaic substation area grid-connected adaptive energy storage control device capable of solving the problems of insufficient power supply capacity and low voltage of the rural distribution network.

[0006] The technical scheme of the application is as follows: the rural network active photovoltaic substation area grid-connected adaptive energy storage control device comprises a photovoltaic unit, a photovoltaic inverter, an energy storage converter, an energy storage unit and an intelligent control cabinet.

[0007] The intelligent control cabinet comprises a data acquisition module, a mode switching module and an adaptive control module.

[0008] The data acquisition module is used to detect the voltage value and the current value at the low-voltage out-line side of the substation area.

[0009] The mode switching module is used to switch three operation modes of grid connection, off-grid and photovoltaic storage island.

[0010] The adaptive control module dynamically adjusts the energy storage charge and discharge power P based on the voltage deviation ΔU. ess .

[0011] Further, the adaptive control module is configured to run the following algorithm when |ΔU|>10% rated voltage U N .

[0012]

[0013] wherein K p is a proportional gain coefficient, K i is an integral gain coefficient.

[0014] Further, the proportional gain coefficient K p and the integral gain coefficient K i satisfy:

[0015]

[0016] wherein S sc is a transformer short-circuit capacity, |Z line | is a line impedance modulus, T resp is a system response time requirement, R eq is an equivalent resistance.

[0017] Further, the adaptive control module is configured to:

[0018] when the real-time voltage U M > 253V, start energy storage charging to absorb surplus power;

[0019] if the voltage still exceeds the limit after the energy storage reaches full capacity, dynamically limit the photovoltaic output.

[0020] Further, in the grid-connected mode, the intelligent control cabinet is switched to connect with the power distribution network to realize bidirectional power interaction; in the off-grid mode, the intelligent control cabinet is switched to disconnect from the power distribution network, and the energy storage unit supports load power supply; in the light-storage island mode, the photovoltaic unit and the energy storage unit cooperate to operate to form a local microgrid.

[0021] Further, the mode switching module switches the control mode according to the following method:

[0022] when U M ∈ [95%U N , 107%U N ] and lasts for > 60s, the grid-connected mode is switched to;

[0023] when U M < 85%U N or Δf > 0.5Hz, the off-grid mode is switched to;

[0024] when U M < 85%U N and , the light-storage island mode is switched to;

[0025] wherein Δf is a frequency deviation, P pv is a real-time photovoltaic output, and P load is a real-time load power.

[0026] Further, the off-grid mode starts the load grading unloading protocol, comprising:

[0027] The primary load keeps supplying power throughout;

[0028] The secondary load is unloaded when U M <80%U N ;

[0029] The tertiary load is unloaded at the moment when the off-grid mode is switched.

[0030] Further, in the light storage island mode, the photovoltaic inverter works in the MPPT mode, and the energy storage converter works in the droop control mode;

[0031] In the droop control mode:

[0032] f ref =f nom -D p ·(P ess -P set );

[0033] Wherein, f ref is a reference frequency, f nom is a rated frequency, D p is an active-frequency droop coefficient, P ess is the real-time output power of the energy storage, and P set is a power set value.

[0034] Further, in the off-grid mode, the energy storage converter adopts the V / f control method:

[0035] U out =220V±1%;

[0036] f out =50Hz±0.1%;

[0037] The voltage frequency is maintained stable by adjusting the output power of the energy storage unit.

[0038] Further, the data acquisition module is connected with a voltage sensor for detecting the voltage value of the low-voltage out-line side of the area and a current sensor for detecting the current value.

[0039] The present application has the following beneficial effects: in the present application, the data acquisition module of the intelligent control cabinet can monitor the current and voltage of the active photovoltaic area of the rural power grid in real time, and can automatically switch the operation mode according to the state of the power grid, dynamically adjust the charging and discharging power of the energy storage unit, thereby improving the power supply quality and reliability, solving the problems of insufficient power supply capacity and low voltage of the rural power distribution network. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The figure is a principle block diagram of the active photovoltaic grid-connected self-adaptive energy storage control device in the rural power grid in the present application. DETAILED DESCRIPTION

[0041] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative in nature and is in no way intended to limit the application, its application, or its uses, except as provided by the appended claims. The application can be embodied in a multitude of different forms and should not be limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art. It should be noted that relative arrangements of components and steps, components of materials, numerical expressions, and values set forth in these embodiments are to be interpreted as merely exemplary, rather than as a limitation, unless otherwise specifically stated.

[0042] The terms "first", "second", and similar terms used in the present application do not indicate any order, number, or importance, but are only used to distinguish different parts. The terms "include" or "contain" and similar terms mean that the elements before the term encompass the elements listed after the term, and do not exclude the possibility of also encompassing other elements. "Up", "down", "left", "right", and the like are only used to indicate relative positional relationships, which may also change accordingly when the absolute position of the described object changes.

[0043] As shown in Figure 1 , a kind of active photovoltaic grid-connected self-adaptive energy storage control device of rural power grid is disclosed, including photovoltaic unit 1, photovoltaic inverter 2, energy storage converter 5, energy storage unit 6 and intelligent control cabinet 3;Intelligent control cabinet 3 includes data acquisition module, mode switching module and adaptive control module;Data acquisition module is used to detect the voltage value and current value of low-voltage out-line side of the area;Mode switching module is used for switching of the three operating modes of grid-connected, off-grid, light storage island;Adaptive control module, based on voltage deviation ΔU dynamically adjusts energy storage charge-discharge power P ess ;In the embodiment, the data acquisition module of intelligent control cabinet 3 can monitor the current and voltage of active photovoltaic grid-connected area of rural power grid in real time, and can automatically switch operating mode according to the state of power grid, dynamically adjust the charge-discharge power of energy storage unit, so as to improve power supply quality and reliability, solve the problems of insufficient power supply capacity and low voltage of rural distribution network.

[0044] In some embodiments, the adaptive control module is configured to run the following algorithm when | ΔU | > 10% rated voltage U N .

[0045]

[0046] Where K p is the proportional gain coefficient, Ki is an integral gain coefficient;

[0047] wherein the proportional gain coefficient K p determines the sensitivity of the control system to the current voltage deviation; if a voltage deviation of 1 V is detected at a certain moment, K p = 5 kW / V means that the energy storage unit will immediately charge at a power of 5 kW to offset this deviation. The integral gain coefficient K i is responsible for eliminating historical accumulated deviations; for example, if the voltage is continuously 0.5 V lower for 10 seconds, K i = 0.1 kW / (V s) will cause the energy storage discharge power to increase by 0.05 kW (0.1 x 0.5) per second until the voltage returns to normal. By combining the proportional term and the integral term, sudden voltage fluctuations can be quickly suppressed, and long-term voltage deviations can be continuously corrected.

[0048] In a specific embodiment, the proportional gain coefficient K p is configured as 5, and the integral gain coefficient K i is configured as 0.1; at this time, if the voltage in a certain area suddenly drops by ΔU = -10 V and lasts for 5 s, the control output P ess = -55 kW, i.e., the energy storage unit discharges at a power of 55 kW, and the voltage returns to the normal range within 5 s.

[0049] In some embodiments, the proportional gain coefficient K p and the integral gain coefficient K i satisfy:

[0050]

[0051] wherein S sc is the short-circuit capacity of the transformer, |Z line | is the line impedance modulus, T resp is the system response time requirement, and R eq is the equivalent resistance.

[0052] In this embodiment, the proportional gain coefficient K p and the integral gain coefficient K i are further defined to be associated with the short-circuit capacity of the transformer, the line impedance, the response time requirement, and the equivalent resistance; according to the actual parameters of the power grid such as the short-circuit capacity and the line impedance, the control parameters are dynamically adjusted, so that the control system adapts to the impedance characteristics of different areas, and the adaptability and stability of the control are improved.

[0053] In some embodiments, the adaptive control module is configured as:

[0054] when the real-time voltage U M > 253 V, the energy storage is started to charge to absorb the surplus power;

[0055] If the voltage is still out of limit after the energy storage reaches the full capacity, i.e., the real-time voltage is still greater than 253V, the photovoltaic output is dynamically limited;

[0056] If the voltage is out of limit, the surplus power is absorbed by starting the energy storage charging to solve the voltage out of limit problem during the period of large photovoltaic generation, and the voltage is avoided to exceed the standard through the cooperative control of the energy storage charging and the photovoltaic output limiting, thereby improving the photovoltaic consumption capacity.

[0057] In some embodiments, in the grid-connected mode, the intelligent control cabinet is connected with the power distribution network to realize bidirectional power interaction; in the off-grid mode, the intelligent control cabinet is disconnected from the power distribution network and is supported by the energy storage unit to supply power to the load 4; in the photovoltaic and energy storage island mode, the photovoltaic unit and the energy storage unit cooperate to operate to form a local microgrid; thus, appropriate operation modes can be provided under different power grid conditions to maintain power supply continuity.

[0058] In some embodiments, the mode switching module switches the control mode according to the following method:

[0059] When U M ∈[95%U N ,107%U N ] and lasts for >60s, the grid-connected mode is switched to;

[0060] When U M <85%U N or Δf>0.5Hz, the off-grid mode is switched to;

[0061] When U M <85%U N and , the photovoltaic and energy storage island mode is switched to;

[0062] Wherein, Δf is the frequency deviation, P pv is the real-time photovoltaic output, and P load is the real-time load power; the intelligent mode switching is realized to quickly switch to the off-grid or island mode when the power grid is abnormal to guarantee the power supply of important loads; and the grid-connected mode is automatically switched to after the power grid is restored to reduce manual intervention.

[0063] In some embodiments, the load grading unloading protocol is started in the off-grid mode, including:

[0064] The primary load is kept powered throughout;

[0065] The secondary load is unloaded when U M <80%U N ;

[0066] The tertiary load is unloaded at the moment of switching to the off-grid mode.

[0067] When the off-grid power supply capability is limited, the power supply reliability is improved and the energy storage utilization efficiency is improved according to the priority of the load; specifically, the first-level load can be defined as lighting, communication equipment, and the second-level load can be defined as water pump equipment, and the third-level load can be defined as some non-essential electrical equipment.

[0068] In some embodiments, in the light storage island mode, the photovoltaic inverter works in the MPPT mode, and the energy storage converter works in the droop control mode.

[0069] In the droop control mode:

[0070] f ref =f nom -D p ·(P ess -P set );

[0071] Wherein, f ref is the reference frequency, f nom is the rated frequency, D p is the active-frequency droop coefficient, P ess is the real-time output power of the energy storage, and P set is the power set value; the droop control makes the energy storage automatically adjust the output according to the load change, realizes the power balance of the light storage, and maintains the frequency stability of the micro-grid.

[0072] In some embodiments, in the off-grid mode, the energy storage converter adopts the V / f control method:

[0073] U out = 220V ± 1%;

[0074] f out = 50Hz ± 0.1%;

[0075] The voltage and frequency stability is maintained by adjusting the output power of the energy storage unit; when the grid is disconnected, the energy storage independently provides voltage and frequency support to ensure the normal operation of the off-grid load.

[0076] In some embodiments, the data acquisition module is connected with a voltage sensor for detecting the voltage value of the low-voltage out-of-line side of the transformer area and a current sensor for detecting the current value; the voltage sensor and the current sensor accurately collect voltage and current data in real time, and provide reliable data basis for mode switching and adaptive control.

[0077] So far, the embodiments of the present application have been described in detail. In order to avoid obscuring the concept of the present application, some details known in the art are not described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein according to the above description.

[0078] The above-described embodiments only express some implementation manners of the present application, which are described in a more specific and detailed manner, but should not be understood as a limitation to the patent scope of the present application. It should be pointed out that, for those skilled in the art, some modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A self-adaptive energy storage control device for grid-connected active photovoltaic power stations in rural areas, characterized in that: It includes photovoltaic units, photovoltaic inverters, energy storage converters, energy storage units, and intelligent control cabinets; The intelligent control cabinet includes a data acquisition module, a mode switching module, and an adaptive control module; The data acquisition module is used to detect the voltage and current values ​​on the low-voltage outgoing side of the transformer area; The mode switching module is used to switch between three operating modes: grid-connected, off-grid, and optical-storage islanding. The adaptive control module dynamically adjusts the energy storage charging and discharging power P based on the voltage deviation ΔU. ess .

2. The rural active photovoltaic power station grid-connected self-adaptive energy storage control device according to claim 1, characterized in that: The adaptive control module is configured such that when |ΔU|>10% of the rated voltage U N At that time, run the following algorithm: Where K p K is the proportional gain coefficient. i This is the integral gain coefficient.

3. The rural active photovoltaic distribution area grid-connected self-adaptive energy storage control device according to claim 2, characterized in that, The proportional gain coefficient K p and the integral gain coefficient K i satisfy: Among them, S sc For the transformer short-circuit capacity, |Z line | represents the magnitude of the line impedance, T resp To meet system response time requirements, R eq This is the equivalent resistance.

4. The rural active photovoltaic power station grid-connected self-adaptive energy storage control device according to claim 1, characterized in that, The adaptive control module is configured as follows: When the real-time voltage U M When the voltage is >253V, the energy storage charging is activated to absorb the excess power. If the voltage still exceeds the limit after the energy storage reaches full capacity, the photovoltaic output will be dynamically limited.

5. The rural active photovoltaic distribution area grid-connected self-adaptive energy storage control device according to claim 1, characterized in that: In the grid-connected mode, the intelligent control cabinet is switched to connect with the power distribution network to achieve bidirectional power interaction; In the off-grid mode, the intelligent control cabinet is disconnected from the power distribution network, and the energy storage unit supports the power supply to the load. In the photovoltaic-storage islanding mode, the photovoltaic unit and the energy storage unit work together to form a local microgrid.

6. The self-adaptive energy storage control device for rural active photovoltaic power station areas according to claim 5, characterized in that, The mode switching module switches the control mode according to the following method: When U M ∈[95%U N 107% U N If the condition persists for more than 60 seconds, switch to the grid connection mode. When U M <85% U N If Δf > 0.5Hz, switch to the off-grid mode; When U M <85% U N and When the time comes, switch to the aforementioned optical storage island mode; Where Δf is the frequency deviation, P pv For real-time photovoltaic power output, P load This represents the real-time power of the load.

7. The rural active photovoltaic distribution area grid-connected self-adaptive energy storage control device according to claim 6, characterized in that, The off-grid mode enables the load grading offloading protocol, including: Level 1 loads maintain continuous power supply; Secondary load in U M <80%U N Uninstall at any time; Level 3 load is unloaded the moment it switches to off-grid mode.

8. The rural active photovoltaic distribution area grid-connected self-adaptive energy storage control device according to claim 1, characterized in that: In the aforementioned photovoltaic-storage islanded mode, the photovoltaic inverter operates in MPPT mode, and the energy storage converter operates in droop control mode. In the droop control mode: f ref =f nom -D p ·(P ess -P set ); Among them, f ref f is the reference frequency. nom For the rated frequency, D p P is the active-frequency droop factor. ess For real-time output power of energy storage, P set This is the power setting value.

9. The self-adaptive energy storage control device for rural active photovoltaic power station areas according to claim 1, characterized in that, In the off-grid mode, the energy storage converter adopts the V / f control method: IN out =220V±1%; f out =50Hz±0.1%; Voltage and frequency stability is maintained by adjusting the output power of the energy storage unit.

10. The rural active photovoltaic distribution area grid-connected self-adaptive energy storage control device according to claim 1, characterized in that: The data acquisition module is connected to a voltage sensor and a current sensor for detecting the voltage and current values ​​on the low-voltage outgoing side of the distribution area.

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