A control method of a light storage system and a system thereof

Abstract

The application discloses a control method and system of a light storage system. The control method comprises the following steps: determining whether a bus voltage loop is saturated based on the state of the bus voltage loop of an inverter bus voltage loop within a certain period every interval of a first time, and sending the determination result to a direct-current converter; when the result is yes, increasing the charging power or reducing the discharging power of the energy storage side direct-current converter, so as to realize the reduction of the total output power of the light storage system; and repeating the operation until the bus voltage loop and the power loop of the inverter compete successfully, the inverter performs constant voltage control to control the bus voltage of the light storage system, and the inverter can keep maximum power tracking of photovoltaic modules, thereby ensuring the maximum utilization of photovoltaic energy.

Description

Technical Field

[0001] This invention relates to the field of automation control technology, and specifically to a control method and system for a photovoltaic energy storage system. Background Technology

[0002] With the development of photovoltaic technology, photovoltaic power generation technology has become increasingly mature, and installed capacity has increased rapidly. However, due to the intermittency and uncontrollability of photovoltaic power generation, photovoltaic power generation systems suffer from problems such as large fluctuations in output power. If the power output of a photovoltaic power generation system is directly output to the grid without processing, it will cause fluctuations in grid voltage and frequency, affecting the stability of the entire grid.

[0003] A photovoltaic (PV) system combined with an energy storage system can effectively mitigate fluctuations in output power. When the PV system outputs excessive energy, the energy storage system charges, reducing the total output power and preventing energy waste. When the PV system's energy is insufficient, the energy storage system discharges to ensure a smooth total power output. However, in actual operation, energy storage systems often operate in constant power charging or discharging modes. When the PV system's output energy changes over time or when the grid's dispatch power changes, the energy storage system operating in constant power mode can easily lead to inefficient utilization of the PV system's energy. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects or problems in the background art and provide a control method and system for a photovoltaic energy storage system, which enables the DC converter on the energy storage side to adjust the output power in real time, and enables the inverter to maintain maximum power tracking of the photovoltaic module, thereby ensuring the maximum utilization of photovoltaic energy.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] Technical Solution 1: A control method for a photovoltaic-storage system, characterized in that the photovoltaic modules in the system output power to the inverter before the energy storage system; the inverter and the photovoltaic modules are directly connected; the inverter and the energy storage-side DC-DC converter are communicatively connected; and the maximum allowable operating power of the energy storage-side DC-DC converter is P. d_set The current operating power of the energy storage-side DC converter is P. dcdc ,P dcdc =P d_set *K mppt -1≤K mppt ≤1, K mppt When K is positive, the DC-DC converter on the energy storage side discharges; mppt When the value is negative, the energy storage-side DC-DC converter is charged, and the energy storage-side DC-DC converter is charged according to the set operating power P. dcdcAdjust its output power; the method includes: the inverter, at each interval, firstly determines whether the bus voltage loop is saturated based on the inverter bus voltage loop state within a certain period and sends the determination result to the energy storage side DC converter; if the result is yes, the energy storage side DC converter, if the K of the previous cycle... mppt If K > -1, then decrease by one step value. mppt If K <-1, then K mppt =-1, if K is reduced by the step value mppt If K is ≥-1, then keep the value after decreasing the step size. mppt If the K of the previous period mppt =-1, then it remains unchanged; 0 < step value < 1.

[0007] Based on technical solution one, there is also technical solution two. In technical solution two, when the result of the DC converter on the energy storage side is negative, if K of the previous cycle... mppt If K is less than 1, then increase the step value by one. If the K value after increasing the step value is less than 1, then increase the step value by one. mppt >1, then K mppt =1, if K is increased by the step value mppt If ≤1, then keep K after increasing the step value. mppt If the K of the previous period mppt If the value is 1, then it remains unchanged.

[0008] Based on technical solution two, there is also technical solution three. In technical solution three, when the grid dispatch power is greater than the sum of the photovoltaic module's power generation and the DC converter's maximum discharge power, K... mppt =1.

[0009] Based on technical solution three, there is also technical solution four. In technical solution four, the inverter determines whether the bus voltage loop is saturated by the following method: the inverter obtains the bus voltage loop reference value, the DC bus voltage value, and the DC bus current value at manually set intervals, and includes the cumulative error between the bus voltage loop reference value and the DC bus voltage value into the DC bus current value to obtain the current set value. The inverter determines whether the current set value exceeds the set current threshold range. If the result is yes, the bus voltage loop is saturated.

[0010] Based on technical solution four, there is also technical solution five. In technical solution five, the method further includes disconnecting the photovoltaic module from the inverter when the output power of the photovoltaic module is less than a set first value.

[0011] Technical Solution Six: The present invention also provides a photovoltaic-storage system, including a photovoltaic module, an inverter, an energy storage system, and an energy storage-side DC-DC converter; the inverter is communicatively connected to the DC-DC converter; the output terminal of the photovoltaic module is directly connected to the DC side of the inverter; the energy storage system is connected to the DC bus of the inverter through the DC-DC converter; the photovoltaic-storage system is used to execute the control method as described in any one of Technical Solutions One to Four.

[0012] Based on technical solution six, there is also technical solution seven. In technical solution seven, the output terminal of the photovoltaic module is connected to the DC side of the inverter through a DC circuit breaker; the DC circuit breaker is used to disconnect when the output power of the photovoltaic module is less than a set first value.

[0013] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. In technical solution one, since the inverter and the energy storage-side DC-DC converter are communicatively connected, the inverter determines whether the bus loop is saturated based on the inverter bus loop status within a certain period at regular intervals and sends the result to the energy storage-side DC-DC converter. If the bus voltage loop is saturated, it indicates that the bus voltage loop has failed to compete with the power loop, and the inverter operates in a limited power mode, that is, the total output power of the photovoltaic-storage system exceeds the grid dispatch power; when the result is yes, the energy storage-side DC-DC converter adjusts K... mppt The value can be adjusted to decrease the set discharge power or increase the set charging power of the DC-DC converter. The energy storage-side DC-DC converter operates according to the set operating power P. dcdc The inverter adjusts its output power to reduce the total output power of the photovoltaic-storage system. This process is repeated until the inverter's bus voltage loop and power loop successfully compete. The inverter then performs constant voltage control to control the bus voltage of the photovoltaic-storage system. Therefore, by adopting this technical solution, the DC-DC converter on the energy storage side can adjust its output power in real time according to the state of the inverter's bus voltage loop, thereby changing the total output power of the photovoltaic-storage system. This allows the inverter to maintain maximum power tracking of the photovoltaic modules, ensuring maximum utilization of photovoltaic energy.

[0015] 2. In technical solution two, if the bus voltage is not saturated, it indicates that the bus voltage loop and power loop have successfully competed. The inverter performs constant voltage control to control the bus voltage of the photovoltaic-storage system, meaning that the total output power of the photovoltaic-storage system does not exceed the grid dispatch power. The DC converter on the energy storage side adjusts K... mppt The value can be adjusted to increase or decrease the set discharge power or charge power of the DC-DC converter. The energy storage-side DC-DC converter operates according to the set operating power P. dcdc Adjusting its output power increases the total output power of the photovoltaic-storage system, thereby meeting the power requirements of grid dispatch.

[0016] 3. In technical solution three, when the grid dispatch power is greater than the sum of the photovoltaic module's power generation and the DC converter's maximum discharge power, K mppt =1, thereby maximizing the total output power of the photovoltaic-storage system and meeting the power requirements of the power grid dispatch.

[0017] 4. In technical solution four, the method for judging bus voltage loop saturation is simple and accurate.

[0018] 5. In technical solution five, when the output power of the photovoltaic module is less than the set first value, the connection between the photovoltaic module and the inverter is disconnected, which avoids the photovoltaic module being without power at night or when the photovoltaic output power is too low, and prevents the grid energy or energy storage system energy from flowing back into the photovoltaic module.

[0019] 6. In technical solution six, the present invention also discloses a photovoltaic-storage system that performs the above control method. The photovoltaic-storage system can adjust the working power and power supply relationship of the energy storage system according to the state of the inverter's bus voltage loop, so that the inverter can maintain maximum power tracking of the photovoltaic modules and ensure the maximum utilization of photovoltaic energy; at the same time, it can also meet the power dispatch requirements of the grid.

[0020] 7. In technical solution seven, the DC circuit breaker is simple to set up and use. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments are briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of the photovoltaic energy storage system according to an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram illustrating the simultaneous power output of a photovoltaic module and an energy storage system to an inverter according to an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram illustrating the power output of a photovoltaic module to an inverter and an energy storage system according to an embodiment of the present invention.

[0025] Figure 4 This is a schematic diagram illustrating the power output of the energy storage system to the inverter when the photovoltaic module is disconnected, according to an embodiment of the present invention.

[0026] Figure 5 This is a schematic diagram illustrating the power output from the power grid to the energy storage system when the photovoltaic module is disconnected, according to an embodiment of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise expressly defined, the use of terms such as "first," "second," or "third" in the claims, description, and accompanying drawings of this invention is for distinguishing different objects and not for describing a specific order.

[0029] In the claims, description and accompanying drawings of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0030] The optical storage system of this application is described below. Figure 1 This is a schematic diagram of a photovoltaic energy storage system according to this application. Figure 1 The photovoltaic-storage system includes photovoltaic modules, an inverter, an energy storage system, and a DC-DC converter on the energy storage side. The output of the photovoltaic modules is directly connected to the DC side of the inverter via a DC disconnect switch, meaning the inverter is a single-stage inverter. The energy storage system is connected to the DC bus of the inverter via the DC-DC converter. The inverter and the DC-DC converter are communicatively connected. The power output from the DC-DC converter to the inverter is generated by the energy storage system, and the DC-DC converter can control the output power of the energy storage system.

[0031] Photovoltaic modules convert solar energy into electrical energy, and energy storage systems store this electrical energy. Optionally, the photovoltaic modules can output power to the grid independently, the energy storage system can output power to the grid independently, or both the photovoltaic modules and the energy storage system can output power to the grid together; the specific method is not limited here. In this application, the photovoltaic modules preferentially output power to the inverter. When energy is insufficient, the DC-DC converter controls the energy storage system to supplement the discharge. The inverter operates in inverter mode.

[0032] In this application, the inverter outer loop includes a power loop and a bus voltage loop, with the power loop receiving power dispatch commands from the grid. The inner loop is a current loop. The DC-DC converter outer loop includes a power control loop and a bus voltage loop, with the inner loop being a current loop.

[0033] In this application, it is assumed that Ppv refers to the maximum discharge power of the photovoltaic module, and A is the grid dispatch power. The grid dispatch power A is issued by the dispatch center. The grid dispatch power A and the power generation power Ppv of the photovoltaic module are both short-term variable.

[0034] The maximum allowable operating power of the DC-DC converter on the energy storage side is P. d_setThe operating power of the DC-DC converter on the energy storage side is set to P. dcdc ,P dcdc =P d_set *K mppt -1≤K mppt ≤1, K mppt When K is positive, the DC-DC converter on the energy storage side discharges; mppt When the value is negative, the DC-DC converter on the energy storage side is charged; Pbat_chargeMax is the maximum allowed charging power of the energy storage system, and Pbat_DischargeMax is the maximum allowed discharging power of the energy storage system.

[0035] The control method of this application includes: at each interval, the inverter determines whether the bus voltage loop is saturated based on the inverter bus voltage loop state within a certain period and sends the determination result to the energy storage-side DC converter; the energy storage-side DC converter adjusts K accordingly. mppt The value is ms. The units for both the first time and a certain period are ms.

[0036] In practice, the inverter determines whether the bus voltage loop is saturated using the following method: The inverter acquires the bus voltage loop reference value, DC bus voltage value, and DC bus current value at manually set intervals, and includes the cumulative error between the bus voltage loop reference value and the DC bus voltage value in the DC bus current value to obtain the current set value. The inverter then determines whether the current set value exceeds the set current threshold range. If the result is yes, the bus voltage loop is saturated. This method for determining bus voltage loop saturation is simple and accurate.

[0037] When the result of the DC-DC converter on the energy storage side is yes, if K in the previous cycle... mppt If K > -1, then decrease by one step value. mppt If K <-1, then K mppt =-1, if K is reduced by the step value mppt If K is ≥-1, then keep the value after decreasing the step size. mppt If the K of the previous period mppt =-1, then remain unchanged; 0 < step value < 1;

[0038] If the result of the DC-DC converter on the energy storage side is negative, then if K in the previous cycle... mppt If K is less than 1, then increase the step value by one. If the K value after increasing the step value is less than 1, then increase the step value by one. mppt >1, then K mppt =1, if K is increased by the step value mppt If ≤1, then keep K after increasing the step value. mppt If the K of the previous period mppt If the value is 1, then it remains unchanged. In this application, the DC-DC converter adjusts its output power according to the inverter's bus voltage loop state.

[0039] In practice, K mppt After the change, P dcdc The value of changes, but at this time P dcdc It is still a theoretical setpoint; the DC-DC converter on the energy storage side operates according to the set power P. dcdc Adjusting its output power, specifically, the DC-DC converter adjusts its output power using a theoretical setpoint P. dcdc The theoretical current value can be calculated by combining the voltage value of the DC-DC converter. The actual current value can be obtained by adjusting the current loop of the DC-DC converter. Thus, the actual operating power can be obtained by combining the voltage value of the DC-DC converter.

[0040] In actual operation, the following scenarios exist:

[0041] Scenario 1: Power A > (Ppv + Pbat_DischargeMax)

[0042] K mppt When Pbat = 1, the DC-DC converter operates at maximum discharge power (Pbat_DischargeMax). In this case, even if the photovoltaic modules and DC-DC converter output maximum power, they cannot meet the grid dispatch power requirements. The photovoltaic-storage system can only try its best to output maximum power to meet the grid dispatch needs. The inverter bus voltage loop operates, and the inverter performs constant voltage control to control the bus voltage. The inverter bus voltage loop is not in a saturated state, i.e., the result is negative.

[0043] At this point, if K from the previous period mppt If K is less than 1, then increase the step value by one. If the K value after increasing the step value is less than 1, then increase the step value by one. mppt >1, then K mppt =1, if K is increased by the step value mppt If ≤1, then keep K after increasing the step value. mppt If the K of the previous period mppt If the value is 1, then it remains unchanged.

[0044] That is, such as Figure 2 As shown, if the DC-DC converter operates in discharge power mode and has not reached the maximum discharge power, the discharge power of the DC-DC converter is increased. If the increased discharge power reaches or exceeds the maximum discharge power, the DC-DC converter is set to operate in maximum discharge power mode. If the increased discharge power does not reach the maximum discharge power, the DC-DC converter is set to operate in the increased discharge power mode. Figure 3 As shown, if the DC-DC converter operates in charging power mode, its charging power is reduced; this increases the total output power of the photovoltaic-storage system, thereby meeting the power demand of the grid dispatch. It should be understood that the increase in the DC-DC converter's charging power corresponds to K... mpptThe absolute value increases.

[0045] Scenario 2: If Max(Ppv, Pbat_DischargeMax) < power A < (Ppv + Pbat_DischargeMax)

[0046] In this scenario, the output power of the photovoltaic modules and DC-DC converter alone is less than the grid dispatch power, failing to meet grid demand. Therefore, the photovoltaic-storage system needs to prioritize power output from the photovoltaic modules to the inverter, with the DC-DC converter providing the remaining power. The inverter bus voltage loop saturates, failing to compete with the power loop. The DC-DC converter's bus voltage loop then operates, successfully competing with the power loop, and performs constant voltage control to regulate the bus voltage.

[0047] The result at this point is that if K in the previous period... mppt If K > -1, then decrease by one step value. mppt If K <-1, then K mppt =-1, if K is reduced by the step value mppt If K is ≥-1, then keep the value after decreasing the step size. mppt If the K of the previous period mppt If the value is -1, then it remains unchanged.

[0048] That is, such as Figure 2 As shown, if the DC-DC converter operates in discharge power mode, then the discharge power of the DC-DC converter should be reduced; for example... Figure 3 As shown, if the DC-DC converter operates in charging power mode but has not reached the maximum charging power, the charging power is increased. If the increased charging power exceeds or reaches the maximum charging power, the DC-DC converter operates in the maximum charging power mode. If the increased charging power does not reach the maximum charging power, the DC-DC converter operates in the increased charging power mode. If the DC-DC converter operates in the maximum charging power mode, the DC-DC converter is kept in the maximum charging power mode, thereby reducing the total output power of the photovoltaic-storage system to meet the power demand of the grid dispatch.

[0049] Similarly, after several cycles, the DC converter operates in charging power mode, or the sum of the DC converter's discharge power and the photovoltaic module's output power is less than or equal to the grid dispatch power. The bus voltage loop may exit the saturation state. At this time, the output power of the photovoltaic-storage system may be less than the grid dispatch power due to the DC converter's charging power being too high or its discharge power being too low.

[0050] If the result in the next cycle is negative, then the K value in the previous cycle will be negative. mppt If K is less than 1, then increase the step value by one. If the K value after increasing the step value is less than 1, then increase the step value by one. mppt >1, then K mppt=1, if K is increased by the step value mppt If ≤1, then keep K after increasing the step value. mppt If the K of the previous period mppt If the value is 1, then it remains unchanged.

[0051] In other words, if the DC-DC converter operates in charging power mode, its charging power is reduced; or if it operates in discharging power mode, its discharging power is increased, thus bringing the total output power of the photovoltaic-storage system closer to the grid dispatch power. When the DC-DC converter's discharging power reaches its maximum, the bus voltage loop re-enters saturation, and the result is the same in the next cycle.

[0052] Scenario 3: Pbat_DischargeMax < Power A <Ppv。

[0053] In this scenario, the maximum output power (Ppv) of the photovoltaic modules exceeds the grid dispatch power, thus meeting grid demand. The inverter bus voltage loop saturates, failing to compete with the power loop, and the inverter implements constant current control. The following two scenarios exist:

[0054] 3.1: Ppv - Pbat_chargeMax < Power A <Ppv;

[0055] When the remaining power of the photovoltaic module (Ppv - power A) is less than the maximum allowable charging power Pbat_chargeMax of the DC converter, the photovoltaic module outputs its maximum power Ppv. At this time, the inverter's bus voltage loop saturates, the DC converter's bus voltage loop operates, successfully competing with the power loop, and controls the bus voltage to maintain constant voltage.

[0056] The result is that the control method is the same as in scenario 2; after several cycles, the DC converter operates in the charging power state, and the bus voltage loop may exit the saturation state. At this time, the power output of the photovoltaic-storage system may be less than the grid dispatch power due to the excessive charging power of the DC converter.

[0057] If the result in the next cycle is negative, then the K value in the previous cycle will be negative. mppt If K is less than 1, then increase the step value by one. If the K value after increasing the step value is less than 1, then increase the step value by one. mppt >1, then K mppt =1, if K is increased by the step value mppt If ≤1, then keep K after increasing the step value. mppt In other words, if the DC-DC converter operates in charging power mode, the charging power of the DC-DC converter is reduced, so that the total output power of the photovoltaic-storage system is close to the grid dispatch power.

[0058] Therefore, in this situation, when the difference between Ppv and the charging power of the DC converter is less than or equal to the grid dispatch power A, the inverter's bus voltage loop will exit the saturation state, and after several cycles, the total output power of the photovoltaic-storage system will approach the grid dispatch power.

[0059] 3.2: Pbat_DischargeMax < Power A <Ppv-Pbat_chargeMax

[0060] When the remaining power of the photovoltaic module (Ppv - power A) is greater than the maximum allowable charging power Pbat_chargeMax of the DC converter, the photovoltaic module outputs the maximum power Ppv, and the inverter's bus voltage loop saturates.

[0061] When the result is yes, the control method is the same as in scenario 2. However, in this case, no matter how the operating power of the DC-DC converter is adjusted, the inverter's bus voltage loop will always be in a saturated state.

[0062] Scenario 4: Ppv <A<Pbat_DischargeMax

[0063] In this case, the power output situation is the same as... Figure 2 The situation is similar. The maximum output power Ppv of the photovoltaic module is less than the grid dispatch power (power A), and the output power of the photovoltaic module alone cannot meet the grid demand. Therefore, the photovoltaic-storage control module needs to output power to the inverter through the photovoltaic module and the DC-DC converter. The inverter bus voltage loop saturates, failing to compete with the power loop, and the inverter performs constant current control to ensure the output grid dispatch power. The photovoltaic module outputs its maximum power Ppv. The DC-DC converter bus voltage loop operates, successfully competing with the power loop, and performs constant voltage control to control the bus voltage.

[0064] When the result is yes, the control method is the same as in scenario 2 above. After several cycles, if the DC-DC converter operates in charging mode or the sum of the DC-DC converter's discharge power and the photovoltaic module's output power is less than or equal to the grid dispatch power, the bus voltage loop may exit the saturation state. That is, during operation, as long as the DC-DC converter operates in charging power mode, the inverter's bus voltage loop will exit the saturation state; as long as the sum of the DC-DC converter's discharge power and Ppv is less than or equal to the grid dispatch power, the inverter's bus voltage loop will exit the saturation state.

[0065] If the result in the next cycle is negative, then the K value in the previous cycle will be negative. mppt If K is less than 1, then increase the step value by one. If the K value after increasing the step value is less than 1, then increase the step value by one. mppt >1, then K mppt =1, if K is increased by the step value mppt If ≤1, then keep K after increasing the step value. mpptIn other words, if the DC-DC converter operates in charging power mode, its charging power is reduced; if it operates in discharging power mode, its discharging power is increased. When the DC-DC converter's discharging power increases to the point that the total output power of the photovoltaic-storage system exceeds the grid dispatch power, the bus voltage loop re-enters saturation, and the result is the same in the next cycle.

[0066] This cycle repeats itself until the total output power of the photovoltaic-storage system approaches the grid dispatch power.

[0067] Scenario 5: Power A <Ppv<Pbat_DischargeMax。

[0068] Please see Figure 3 In this scenario, the maximum output power Ppv of the photovoltaic modules exceeds the grid dispatch power, thus meeting grid demand. The inverter bus voltage loop saturates and fails to compete with the power loop; the inverter then uses the grid dispatch power for constant current control.

[0069] When the result is yes, the control method is the same as in scenario 2 above. After several cycles, the DC converter operates in the charging power state, and the bus voltage loop may exit the saturation state. At this time, the power output of the photovoltaic-storage system may be less than the grid dispatch power due to the excessive charging power of the DC converter.

[0070] If the result in the next cycle is negative, then the K value in the previous cycle will be negative. mppt If K is less than 1, then increase the step value by one. If the K value after increasing the step value is less than 1, then increase the step value by one. mppt >1, then K mppt =1, if K is increased by the step value mppt If ≤1, then keep K after increasing the step value. mppt In other words, if the DC-DC converter operates in charging power mode, the charging power of the DC-DC converter is reduced, so that the total output power of the photovoltaic-storage system is close to the grid dispatch power.

[0071] Therefore, in this situation, when the difference between Ppv and the charging power of the DC converter is less than or equal to the grid dispatch power A, the inverter's bus voltage loop will exit the saturation state, and after several cycles, the total output power of the photovoltaic-storage system will approach the grid dispatch power.

[0072] like Figure 4 and Figure 5 As shown, the control method of this application also includes disconnecting the photovoltaic module from the inverter when the output power of the photovoltaic module is less than a set first value, thus preventing grid energy or energy from the energy storage system from flowing back into the photovoltaic module when the photovoltaic module is out of power at night or when the photovoltaic output power is too low. The first value can be set according to actual needs and is not limited here.

[0073] In this application, photovoltaic modules prioritize power output to the inverter over the energy storage system. At regular intervals, the inverter determines whether the bus loop is saturated based on the inverter bus loop status over a certain period and sends the result to the energy storage-side DC converter. If the bus voltage loop is saturated, it indicates that the competition between the bus voltage loop and the power loop has failed, and the inverter operates in a limited-power mode, meaning the total output power of the photovoltaic-energy storage system exceeds the grid dispatch power. When the result is yes, the energy storage-side DC converter adjusts K... mppt The value can be adjusted to decrease the set discharge power or increase the set charging power of the DC-DC converter. The energy storage-side DC-DC converter operates according to the set operating power P. dcdc The output power is adjusted to reduce the total output power of the photovoltaic-storage system. This process is repeated until the inverter's bus voltage loop and power loop successfully compete. The inverter then performs constant voltage control to regulate the bus voltage of the photovoltaic-storage system. Therefore, using this technical solution, the energy storage-side DC converter can adjust its output power in real time according to the inverter's bus voltage loop status, thereby changing the total output power of the photovoltaic-storage system. This allows the inverter to maintain maximum power tracking of the photovoltaic modules, ensuring maximum utilization of photovoltaic energy. If the bus voltage is not saturated, it indicates that the bus voltage loop and power loop have successfully competed. The inverter performs constant voltage control to regulate the bus voltage of the photovoltaic-storage system, meaning the total output power of the photovoltaic-storage system does not exceed the grid dispatch power. If the result is negative, the energy storage-side DC converter adjusts K... mppt The value can be adjusted to increase the set discharge power of the DC-DC converter or decrease the set charging power of the DC-DC converter. The energy storage-side DC-DC converter operates according to the set operating power P. dcdc Adjusting its output power increases the total output power of the photovoltaic-storage system, thereby meeting the power requirements of grid dispatch.

[0074] The foregoing description of the specifications and embodiments is intended to explain the scope of protection of this invention, but does not constitute a limitation on the scope of protection of this invention. Modifications, equivalent substitutions, or other improvements to the embodiments of this invention or a portion thereof that can be obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this invention or the foregoing embodiments, in conjunction with common knowledge, general technical knowledge, and / or existing technology, should all be included within the scope of protection of this invention.

Claims

1. A control method for a photovoltaic-energy storage system, characterized in that, In the photovoltaic-storage system, the photovoltaic modules prioritize power output to the inverter over the energy storage system. The inverter and photovoltaic modules are directly connected, and the inverter and the energy storage-side DC-DC converter are communicatively connected. The maximum allowable operating power of the energy storage-side DC-DC converter is P. d_set The operating power of the energy storage-side DC-DC converter is set to P. dcdc ,P dcdc =P d_set *K mppt -1≤K mppt ≤1, K mppt When K is positive, the DC-DC converter on the energy storage side discharges; mppt When the value is negative, the energy storage-side DC-DC converter is charged, and the energy storage-side DC-DC converter is charged according to the set operating power P. dcdc Adjust its output power; The method includes: at each interval, the inverter determines whether the bus voltage loop is saturated based on the inverter bus voltage loop status within a certain period, and sends the determination result to the energy storage side DC converter. When the result of the DC-DC converter on the energy storage side is yes, if K in the previous cycle... mppt If K > -1, then decrease by one step value. mppt If K <-1, then K mppt =-1, if K is reduced by the step value mppt If K is ≥-1, then keep the value after decreasing the step size. mppt If the K of the previous period mppt =-1, then it remains unchanged; 0 < step value < 1.

2. The control method for a photovoltaic energy storage system as described in claim 1, characterized in that, If the result of the DC-DC converter on the energy storage side is negative, then if K in the previous cycle... mppt If K is less than 1, then increase the step value by one. If the K value after increasing the step value is less than 1, then increase the step value by one. mppt >1, then K mppt =1, if K is increased by the step value mppt If ≤1, then keep K after increasing the step value. mppt If the K of the previous period mppt If the value is 1, then it remains unchanged.

3. The control method for a photovoltaic energy storage system as described in claim 2, characterized in that, When the grid dispatch power is greater than the sum of the photovoltaic module's power generation and the DC converter's maximum discharge power, K mppt =1.

4. The control method for a photovoltaic energy storage system as described in claim 3, characterized in that, The inverter determines whether the bus voltage loop is saturated by the following method: The inverter obtains the bus voltage loop reference value, DC bus voltage value, and DC bus current value at manually set intervals, and adds the cumulative error between the bus voltage loop reference value and the DC bus voltage value to the DC bus current value to obtain the current set value. The inverter determines whether the current set value exceeds the set current threshold range. If the result is yes, the bus voltage loop is saturated.

5. The control method for a photovoltaic energy storage system as described in claim 4, characterized in that, The method also includes disconnecting the photovoltaic module from the inverter when the output power of the photovoltaic module is less than a set first value.

6. A photovoltaic energy storage system, characterized in that, This includes photovoltaic modules, inverters, energy storage systems, and DC-DC converters for the energy storage side; The inverter is communicatively connected to the DC-DC converter; The output terminal of the photovoltaic module is directly connected to the DC side of the inverter. The energy storage system is connected to the DC bus of the inverter via the DC converter; The optical storage system is used to perform the control method as described in any one of claims 1-4.

7. A photovoltaic energy storage system as described in claim 6, characterized in that, The output terminal of the photovoltaic module is connected to the DC side of the inverter via a DC circuit breaker; the DC circuit breaker is used to disconnect when the output power of the photovoltaic module is less than a set first value.

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