High-voltage limiting control method, system and application based on photovoltaic energy storage system

Abstract

A high-voltage amplitude limiting control method, system, and application based on a photovoltaic energy storage system obtains the photovoltaic voltage, photovoltaic current, and bus voltage of the current control cycle; sets the voltage disturbance step size, bus voltage reference value, bus voltage upper limit value, proportional coefficient 1 and proportional coefficient 2, integral coefficient 1 and integral coefficient 2 of the PID controller, subtracts the bus voltage from the bus voltage reference value to obtain a bus voltage reference error value, and subtracts the bus voltage from the bus voltage upper limit value to obtain a bus voltage upper limit error value; multiplies the battery voltage and the battery current to obtain the photovoltaic power until the bus voltage is controlled within the bus voltage upper limit value. The present invention limits the bus voltage under extreme operating conditions of the energy storage by the sum of the product of the proportional coefficient and the bus voltage upper limit error value and the product of the integral coefficient and the integral value of the bus voltage upper limit error value, thereby achieving system high-voltage amplitude limiting.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaic energy storage control technology, and specifically relates to a high-voltage amplitude limiting control method, system and application based on a photovoltaic energy storage system. Background Art

[0002] With the decreasing fossil energy and the worsening environmental pollution, people are facing an unprecedented crisis. As an emerging green energy, solar energy meets people's requirements for production and life applications and has great development prospects. Among them, photovoltaic power generation is the most widely used.

[0003] Photovoltaic power generation is affected by factors such as temperature and the environment, resulting in random and intermittent output. To ensure maximum power from a photovoltaic system, it is essential to ensure that the system operates at its maximum power point (MPP). MPPT algorithms are typically designed to enable a photovoltaic system to operate at maximum power under varying weather conditions by varying the operating voltage.

[0004] Due to the intermittent and fluctuating output characteristics of household photovoltaic power generation, large-scale household distributed photovoltaic grid connection will bring huge challenges to the stable operation of low-voltage distribution networks, especially the impact on the voltage of distribution networks has become increasingly prominent. In recent years, with the continuous maturity of energy storage technology and its significant cost reduction, the application of distributed energy storage in improving the voltage quality of low-voltage distribution networks and the ability to absorb new energy has received widespread attention. Therefore, in order to solve the voltage over-limit problem caused by the integration of a high proportion of household photovoltaics into the low-voltage distribution network, it is extremely necessary to design and study the voltage coordination control strategy using photovoltaic inverters and distributed energy storage.

[0005] Compared with the prior art, the differences are as follows:

[0006] Technical comparison with patent CN104578043B "A method for coordinated power balance control in a DC microgrid with high penetration of photovoltaic and energy storage";

[0007] Patent CN104578043B specifies a bus rated voltage and controls the system's bus voltage near the rated voltage through energy storage charging and discharging and photovoltaic unloading. This study, however, specifies not only a bus rated voltage but also an upper limit for the bus voltage. Compared to the method of CN104578043B that specifies only a single bus rated voltage, this method has a larger safe operating range for the bus voltage. Furthermore, specifying a safe upper limit for the bus voltage allows for adaptability to changing environments. Maximum power point tracking is performed using a conductance increment method with a dual-step adjustment coefficient. We use a three-stage variable-step maximum power point tracking method based on the conductance increment method. This method is simpler and more effective than the series of initial compensation adjustment coefficients used in CN111259890A. The three-stage variable-step tracking method offers a more flexible tracking speed and is adaptable to changing environments.

[0008] Patent CN104578043B uses the method of calculating the safe time for the bus voltage to deviate from the bus safety offset voltage to determine whether the energy storage has lost control of the bus voltage. This method makes the algorithm more complex. In contrast, this study uses the method of determining whether the DC bus voltage exceeds the specified bus voltage upper limit to determine whether the energy storage has lost control of the bus voltage. This method has the characteristics of simple algorithm and is highly applicable to most environments. Summary of the Invention

[0009] To address the above issues, the present invention proposes a high-voltage amplitude limiting control method, system, and application based on a photovoltaic energy storage system. The present invention determines the bus voltage step size by calculating the sum of the product of the proportional coefficient and the voltage reference / upper limit error value and the product of the integral coefficient and the integral value of the bus voltage reference / upper limit error value in the previous control cycle. When the system bus voltage is about to exceed the upper limit, the system bus voltage is controlled to operate stably within a safe range.

[0010] To achieve the above object, the technical solution adopted by the present invention is:

[0011] The high-voltage amplitude limiting control method based on a photovoltaic energy storage system includes the following steps:

[0012] 1) Obtain the photovoltaic voltage, photovoltaic current and DC bus voltage of the current control cycle;

[0013] 2) Multiply the photovoltaic voltage and photovoltaic current to obtain the photovoltaic power;

[0014] 3) Compare the photovoltaic power of the current control cycle with the photovoltaic power of the previous control cycle;

[0015] If the photovoltaic power of the current control cycle is equal to the photovoltaic power of the previous control cycle, the voltage step size is kept unchanged;

[0016] If the photovoltaic power of the current control cycle is less than the photovoltaic power of the previous control cycle, and the photovoltaic voltage of the current control cycle is less than the photovoltaic voltage of the previous control cycle, reducing the photovoltaic voltage step size;

[0017] If the photovoltaic power of the current control cycle is less than the photovoltaic power of the previous control cycle, and the photovoltaic voltage of the current control cycle is greater than the photovoltaic voltage of the previous control cycle, increasing the photovoltaic voltage step size;

[0018] If the photovoltaic power of the current control cycle is greater than the photovoltaic power of the previous control cycle, and the photovoltaic voltage of the current control cycle is less than the photovoltaic voltage of the previous control cycle, then increasing the photovoltaic voltage step size;

[0019] If the photovoltaic power of the current control cycle is greater than the photovoltaic power of the previous control cycle, and the photovoltaic voltage of the current control cycle is greater than the photovoltaic voltage of the previous control cycle, reducing the photovoltaic voltage step size;

[0020] If the bus voltage is lower than the bus voltage reference value, increasing the bus voltage step size;

[0021] If the bus voltage is higher than the bus voltage reference value and lower than the bus voltage upper limit, the bus voltage step size is reduced; if the bus voltage is higher than the bus voltage upper limit, the photovoltaic voltage step size is reduced;

[0022] 4) Repeat the above steps in each control cycle to track the maximum power point while ensuring that the bus voltage is controlled within the bus voltage upper limit;

[0023] A reference value and an upper limit are specified for the bus voltage. If the energy storage is in normal operating conditions, the bus voltage is controlled near the reference value while the photovoltaic system tracks the maximum power point, combined with the charging and discharging functions of the energy storage. If the energy storage is in extreme operating conditions, continuing to track the photovoltaic maximum power point will cause damage to the energy storage and the bus voltage will exceed the upper limit of the bus voltage for safe operation. The photovoltaic maximum power point should be tracked only after the bus voltage is limited to below the upper limit of the bus voltage to ensure safe operation of the system.

[0024] As a further improvement to the control method of the present invention, the photovoltaic voltage step size is set to a fixed value;

[0025] When the bus voltage is lower than the bus voltage upper limit, the bus voltage step size of the current control cycle is determined by calculating the sum of the product of the proportional coefficient 1 and the bus voltage reference error value of the previous control cycle and the product of the integral coefficient 1 and the integral value of the bus voltage reference error value of the previous control cycle;

[0026] When the bus voltage is higher than the bus voltage upper limit value, the bus voltage step size of the current control cycle is calculated by the sum of the product of the proportional coefficient 2 and the bus voltage upper limit error value of the previous control cycle and the product of the integral coefficient 2 and the integral value of the bus voltage upper limit error value of the previous control cycle;

[0027] Among them, the proportional coefficient 1, proportional coefficient 2, integral coefficient 1, and integral coefficient 2 are respectively set to fixed values, the bus voltage reference error value of the previous control period is the difference between the bus voltage of the previous control period and the bus voltage reference value, and the bus voltage upper limit error value of the previous control period is the difference between the bus voltage of the previous control period and the bus voltage upper limit value;

[0028] The determined photovoltaic voltage step size is ΔUref, and the bus voltage step size when the bus voltage is lower than the bus voltage upper limit is S*(K p1 *ΔU dc1 (k-1)+K i1 *∫ΔU dc1 (k-1)dt), where K p1 , K i1 They are proportional coefficient 1, integral coefficient 1, ΔU dc1 (k-1) is the bus voltage reference error value of the previous control cycle. The bus voltage step size when the bus voltage is higher than the bus voltage upper limit is K. p2 *ΔU dc2 (k-1)+K i2 *∫ΔU dc2 (k-1)dt, where K p2 , K i2 They are proportional coefficient 2, integral coefficient 2, ΔU dc2 (k-1) is the bus voltage upper limit error value of the previous control cycle.

[0029] The present invention provides a system for a high-voltage amplitude limiting control method based on a photovoltaic energy storage system, comprising a real-time voltage acquisition module, a real-time power acquisition module, a bus voltage step acquisition module, a comparison module 1, a comparison module 2, a comparison module 3, an iterative control module 1, and an iterative control module 2:

[0030] A real-time voltage acquisition module is configured to obtain the photovoltaic voltage and bus voltage of the current control cycle;

[0031] A real-time power acquisition module is configured to acquire the photovoltaic power of the current control cycle;

[0032] A bus voltage step length acquisition module is configured to acquire the bus voltage step length of the current control cycle;

[0033] a first comparison module configured to compare the photovoltaic power of a current control cycle with the photovoltaic power of a previous control cycle;

[0034] a second comparison module configured to compare the photovoltaic voltage of a current control cycle with the photovoltaic voltage of a previous control cycle;

[0035] A comparison module three is configured to compare the bus voltage of the previous control cycle with the bus voltage reference value and the bus voltage upper limit value respectively;

[0036] an iterative control module 1, configured to, if the photovoltaic power of the current control cycle is equal to the photovoltaic power of the previous control cycle, maintain the voltage step size unchanged; if the photovoltaic power of the current control cycle is less than the photovoltaic power of the previous control cycle and the photovoltaic voltage of the current control cycle is less than the photovoltaic voltage of the previous control cycle, reduce the photovoltaic voltage step size; if the photovoltaic voltage of the current control cycle is greater than the photovoltaic voltage of the previous control cycle, increase the photovoltaic voltage step size; if the photovoltaic power of the current control cycle is greater than the photovoltaic power of the previous control cycle and the photovoltaic voltage of the current control cycle is less than the photovoltaic voltage of the previous control cycle, increase the photovoltaic voltage step size; if the photovoltaic voltage of the current control cycle is greater than the photovoltaic voltage of the previous control cycle, reduce the photovoltaic voltage step size;

[0037] an iterative control module 2, configured to increase the bus voltage step size if the bus voltage is lower than the bus voltage reference value, decrease the bus voltage step size if the bus voltage is higher than the bus voltage reference value and lower than the bus voltage upper limit, and decrease the photovoltaic voltage step size if the bus voltage is higher than the bus voltage upper limit;

[0038] Repeat the above steps in each control cycle until the bus voltage is controlled within the bus voltage upper limit;

[0039] The photovoltaic power value of the current control cycle is the product of the photovoltaic voltage and the photovoltaic current;

[0040] The photovoltaic voltage step size is ΔUref, and the bus voltage step size when the bus voltage is lower than the bus voltage upper limit is S*(K p1 *ΔU dc1 (k-1)+K i1 *∫ΔU dc1 (k-1)dt), where K p1 , K i1 They are proportional coefficient 1, integral coefficient 1, ΔU dc1 (k-1) is the bus voltage reference error value of the previous control cycle. The bus voltage step size when the bus voltage is higher than the bus voltage upper limit is K. p2 *ΔU dc2 (k-1)+K i2 *∫ΔU dc2 (k-1)dt, where K p2, K i2 They are proportional coefficient 2, integral coefficient 2, ΔU dc2 (k-1) is the bus voltage upper limit error value of the previous control cycle.

[0041] As a further improvement of the control system of the present invention, the iterative control module also includes a bus voltage step calculation module, which is configured to calculate and determine the bus voltage step based on the sum of the product of the proportional coefficient and the voltage reference\upper limit error value and the integral coefficient and the integral value of the bus voltage reference\upper limit error value of the previous control cycle.

[0042] The present invention provides an application of a high-voltage amplitude limiting control method based on a photovoltaic energy storage system, including a computer-readable storage medium, an electronic device, and a photovoltaic system.

[0043] The computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by the processor, the steps in the method described in the present invention are completed.

[0044] The electronic device includes a memory and a processor, and computer instructions stored in the memory and running on the processor. When the computer instructions are run by the processor, the steps of the method described in the present invention are completed.

[0045] The photovoltaic system adopts the steps of the method described in the present invention, and includes the control system described in the present invention, the readable storage medium described in the present invention, or the electronic device described in the present invention.

[0046] The advantages of the present invention are:

[0047] Photovoltaic power generation has intermittent and fluctuating output characteristics. Large-scale household distributed photovoltaic grid connection will bring huge challenges to the stable operation of low-voltage distribution networks. In particular, the impact on the voltage of the distribution network is becoming increasingly prominent. In order to keep the bus voltage of the photovoltaic storage system within a safe range, energy storage is required to participate in controlling the bus voltage. Conventional energy storage constant voltage control technology, when the energy storage is in extreme working conditions, continuing to track the photovoltaic maximum power point will cause damage to the energy storage and the bus voltage will exceed the upper limit of the bus voltage safe operation. Therefore, the present invention stipulates a reference value and an upper limit for the bus voltage. If the energy storage is in normal working conditions, it will prioritize tracking the photovoltaic maximum power point. If the energy storage is in extreme working conditions, it will prioritize controlling the bus voltage to be below the safe operation upper limit before tracking the photovoltaic maximum power point.

[0048] The present invention can solve the problem of bus voltage exceeding the limit when the energy storage is in the extreme working condition, thereby effectively maintaining the stable operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1This is a system structure diagram of the high-voltage amplitude limiting control method based on the photovoltaic energy storage system of the present invention;

[0050] Figure 2 This is a flow chart of a high-voltage amplitude limiting control method based on a photovoltaic energy storage system according to the present invention;

[0051] Figure 3 It is the PU characteristic curve of the photovoltaic array provided in the high-voltage amplitude limiting control method based on the photovoltaic energy storage system of the present invention;

[0052] Figure 4 It is a simulation waveform of the maximum power point tracking method when the energy storage is in an extreme working condition based on the high-voltage amplitude limiting control method of the photovoltaic energy storage system of the present invention;

[0053] Figure 5 It is a simulation waveform of the bus voltage when the energy storage is in the extreme working condition based on the high-voltage amplitude limiting control method of the photovoltaic energy storage system of the present invention. DETAILED DESCRIPTION

[0054] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0055] like Figure 1 The system structure of a high-voltage amplitude limiting control method based on a photovoltaic energy storage system is shown, including: a photovoltaic array, an energy storage device, a sampling module, an MPPT calculation module, a PWM drive module, a boost module, a DC / DC module, a capacitor, and a load. The input of two sampling modules is connected to the output of the photovoltaic array, and the output is connected to the input of the MPPT calculation module. The output of the MPPT calculation module is connected to the input of the PWM drive module. The output of the PWM drive module is connected to the input of the boost module. The output of the boost module is connected to the load module. The output of the energy storage device is connected to the input of the DC / DC module. The input of another sampling module is connected to the load module, and the output is connected to the DC / DC module. The output of the DC / DC module is connected to the load module.

[0056] Among them, the sampling module includes two voltage sampling modules and a current sampling module. The voltage sampling module is connected to the output end of the photovoltaic array and the input end of the load module respectively, and the current sampling module is connected to the output end of the photovoltaic array. It is used to collect the output voltage and output current of the photovoltaic array and the DC bus voltage in real time, and send them to the MPPT calculation module and DC / DC module.

[0057] Photovoltaic power generation has intermittent and fluctuating output characteristics. Large-scale household distributed photovoltaic grid connection will affect the stable operation of the low-voltage distribution network bus voltage. In order to keep the bus voltage of the photovoltaic storage system within a safe range, energy storage is required to participate in bus voltage control. Conventional energy storage constant voltage control technology, when the energy storage is in extreme operating conditions, will continue to track the photovoltaic maximum power point, resulting in damage to the energy storage and the bus voltage exceeding the upper limit of the bus voltage safe operation. Therefore, the present invention specifies a reference value and an upper limit for the bus voltage. If the energy storage is in normal operating conditions, it will prioritize tracking the photovoltaic maximum power point. If the energy storage is in extreme conditions, it will prioritize controlling the bus voltage to below the safe operating upper limit before tracking the photovoltaic maximum power point.

[0058] Specifically, the present invention provides a maximum power point tracking method based on an improved conductance increment method. While controlling the MPPT of photovoltaic cells, a momentum term is introduced according to the principle of the perturbation-observation method and the bidirectional charging and discharging characteristics of energy storage. The method determines whether to continue tracking the photovoltaic maximum power point and whether the energy storage has reached the limit operating condition by comparing the bus voltage with a bus voltage reference value and a bus voltage upper limit, thereby ensuring the stable operation of the bus voltage of the photovoltaic energy storage system.

[0059] like Figure 2 As shown, this method includes the following specific steps:

[0060] Step S1: Detect the current voltage U(k), U dc (k) and current I(k).

[0061] Step S2: According to the detected voltage U(k) and current I(k), the current voltage U(k) is multiplied by the current I(k) to obtain the power P(k), and the voltage U(k-1) at the previous moment is multiplied by the current I(k-1) at the previous moment to obtain the power P(k-1). The fixed photovoltaic voltage step ΔU is specified. ref , bus voltage reference value U dcref , bus voltage upper limit U dcup , proportionality coefficient K p1 and K p2 , integral coefficient K i1 and K i2 , the current voltage U dc (k) and bus voltage reference value U dcref The bus voltage reference error value ΔU is obtained by subtracting dc1 (k), the voltage U at the current moment dc (k) and the bus voltage upper limit U dcup The bus voltage upper limit error value ΔU is obtained by subtracting dc2 (k); the proportional coefficient K p1 And bus voltage reference error value U dcrefThe product of and the integral coefficient K i1 And bus voltage reference error value U dcref The product of the integral value of is added to get the bus voltage step ΔU1, and the proportional coefficient K p2 And the bus voltage upper limit error value U dcup The product of and the integral coefficient K i2 And bus voltage reference error value U dcup The product of the integral values ​​is added to obtain the bus voltage step ΔU2.

[0062] Step S3: Determine the relationship between the power P(k) at the current moment and the power P(k-1) at the previous moment. If P(k) is greater than P(k-1), proceed to step S4; if P(k) is less than P(k-1), proceed to step S5; if P(k) is equal to P(k-1), proceed to step S6.

[0063] Step S4: Determine the relationship between the current voltage U(k) and the previous voltage U(k-1). If U(k) is greater than U(k-1), the output photovoltaic voltage step is a positive value of the fixed photovoltaic voltage step, U(k)=U(k-1)+ΔU ref If U(k) is less than U(k-1), the output photovoltaic voltage step is the negative value of the fixed photovoltaic voltage step, U(k)=U(k-1)-ΔU ref .

[0064] Step S5: Determine the relationship between the current voltage U(k) and the previous voltage U(k-1). If U(k) is greater than U(k-1), the output photovoltaic voltage step is the negative value of the fixed photovoltaic voltage step, U(k) = U(k-1) - ΔU ref If U(k) is less than U(k-1), the output photovoltaic voltage step is a positive value of the fixed photovoltaic voltage step, U(k)=U(k-1)+ΔU ref . Next, proceed to step S6.

[0065] Step S6: Determine the bus voltage U at the previous moment dc (k-1) and the bus voltage upper limit U dcup The size of U dc (k-1) is greater than U dcup , the output photovoltaic voltage step is the positive value of the bus voltage step ΔU1, U(k)=U(k-1)+ΔU1, then enter step S8; if U dc (k-1) is greater than U dcup , then go to step S7.

[0066] Step S7: Determine the bus voltage U at the previous moment dc (k-1) and bus voltage reference value U dcref The size of Udc (k-1) is greater than U dcref , the output bus voltage step is the positive value of the bus voltage step ΔU2, U dc (k)=U dc (k-1)+ΔU2; if U dc (k-1) is less than U dcref , the output bus voltage step is the negative value of the bus voltage step ΔU2, U dc (k)=U dc (k-1)-ΔU2, then proceed to step S8.

[0067] Step S8: Update U(k-1), I(k-1) and U dc (k-1), U(k-1)=U(k), I(k-1)=I(k), U dc (k-1)=U dc (k).

[0068] In the Matlab / Simulink environment, a composite MPPT control model of the photovoltaic array boost circuit is built. The simulation parameters of the photovoltaic array are set as shown in the following table:

[0069] Parameter name Parameter value <![CDATA[Short-circuit current I sc > 313.6A <![CDATA[Open-circuit voltage U oc > 363V <![CDATA[Maximum power point current I mpp > 294A <![CDATA[Maximum power point voltage U mpp > 290V irradiance <![CDATA[1000W / m 2 ]]> temperature 25℃

[0070] In the Matlab / Simulink environment, a high-voltage limiting control model for the DC / DC module of the energy storage device was built. The simulation parameters of the energy storage device are set as shown in the following table:

[0071] Parameter name Parameter value Rated voltage 500V Rated capacity 400Ah Initial capacity status 80％ Battery response time 30s

[0072] The simulation was performed at a temperature of 25°C and a light intensity of 1000W / m 2 The operation condition is set to 1s, when the energy storage device reaches the limit working condition, it is disconnected from the system. The characteristic curve of the photovoltaic array is as follows: Figure 3 As shown, under the simulation conditions of this case, the maximum power point voltage U mpp =460.8V, maximum power point power P mpp =36080.6W.

[0073] In the simulation of a high voltage amplitude limiting control method based on a photovoltaic energy storage system proposed in the present invention, the fixed step size ΔU is first determined. ref , bus voltage reference value U dcref and bus voltage upper limit U dcup Then determine the proportional coefficient K p1 , K p2 , integral coefficient K i1 , K i2The output simulation diagram of the bus voltage high voltage limiting control method proposed by the present invention is as follows: Figure 4 and Figure 5 As shown in FIG, after algorithm control, the bus voltage is stabilized at the upper limit value in about 0.074 seconds, and the photovoltaic power also stops tracking the maximum power point and drops to an output power that can stabilize the bus voltage at the upper limit value.

[0074] The following table shows the simulation results of the above high-voltage amplitude limiting control technology based on the photovoltaic energy storage system. It can be seen that the high-voltage amplitude limiting control technology based on the photovoltaic energy storage system proposed in the present invention has a short control time and small oscillation after reaching the maximum steady state.

[0075] plan Time required to reach steady state / s <![CDATA[Steady-state maximum power (*10 4 ) / W]]> <![CDATA[Steady-state minimum power (*10 4 ) / W]]> Improved 0.074 7.703 7.699

[0076] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent variation based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A high-voltage amplitude limiting control method based on a photovoltaic energy storage system includes the following steps, characterized in that: 1) Obtain the photovoltaic voltage, photovoltaic current and DC bus voltage of the current control cycle; 2) Multiply the photovoltaic voltage and photovoltaic current to obtain the photovoltaic power; 3) Compare the photovoltaic power of the current control cycle with the photovoltaic power of the previous control cycle; If the photovoltaic power of the current control cycle is equal to the photovoltaic power of the previous control cycle, the voltage step size is kept unchanged; If the photovoltaic power of the current control cycle is less than the photovoltaic power of the previous control cycle, and the photovoltaic voltage of the current control cycle is less than the photovoltaic voltage of the previous control cycle, reducing the photovoltaic voltage step size; If the photovoltaic power of the current control cycle is less than the photovoltaic power of the previous control cycle, and the photovoltaic voltage of the current control cycle is greater than the photovoltaic voltage of the previous control cycle, increasing the photovoltaic voltage step size; If the photovoltaic power of the current control cycle is greater than the photovoltaic power of the previous control cycle, and the photovoltaic voltage of the current control cycle is less than the photovoltaic voltage of the previous control cycle, then increasing the photovoltaic voltage step size; If the photovoltaic power of the current control cycle is greater than the photovoltaic power of the previous control cycle, and the photovoltaic voltage of the current control cycle is greater than the photovoltaic voltage of the previous control cycle, reducing the photovoltaic voltage step size; If the bus voltage is lower than the bus voltage reference value, increasing the bus voltage step size; If the bus voltage is higher than the bus voltage reference value and lower than the bus voltage upper limit, the bus voltage step size is reduced; if the bus voltage is higher than the bus voltage upper limit, the photovoltaic voltage step size is reduced; 4) Repeat the above steps in each control cycle to track the maximum power point while ensuring that the bus voltage is controlled within the bus voltage upper limit; A reference value and an upper limit are specified for the bus voltage. If the energy storage is in normal operating conditions, the bus voltage is controlled near the reference value while the photovoltaic system tracks the maximum power point, combining the charging and discharging functions of the energy storage. If the energy storage is in extreme operating conditions, continuing to track the photovoltaic maximum power point will cause damage to the energy storage and the bus voltage will exceed the upper limit of the bus voltage for safe operation. Tracking the photovoltaic maximum power point is performed only after ensuring that the bus voltage is limited below the upper limit of the bus voltage.

2. The high voltage limiting control method based on the photovoltaic energy storage system according to claim 1, It is characterized by: The photovoltaic voltage step size is set to a fixed value; When the bus voltage is lower than the bus voltage upper limit, the bus voltage step size of the current control cycle is determined by calculating the sum of the product of the proportional coefficient 1 and the bus voltage reference error value of the previous control cycle and the product of the integral coefficient 1 and the integral value of the bus voltage reference error value of the previous control cycle; When the bus voltage is higher than the bus voltage upper limit value, the bus voltage step size of the current control cycle is calculated by the sum of the product of the proportional coefficient 2 and the bus voltage upper limit error value of the previous control cycle and the product of the integral coefficient 2 and the integral value of the bus voltage upper limit error value of the previous control cycle; Among them, the proportional coefficient 1, proportional coefficient 2, integral coefficient 1, and integral coefficient 2 are respectively set to fixed values, the bus voltage reference error value of the previous control period is the difference between the bus voltage of the previous control period and the bus voltage reference value, and the bus voltage upper limit error value of the previous control period is the difference between the bus voltage of the previous control period and the bus voltage upper limit value; The determined photovoltaic voltage step size is , the bus voltage step length when the bus voltage is lower than the bus voltage upper limit is ,in, 、 They are proportional coefficient 1, integral coefficient 1, is the bus voltage reference error value of the previous control cycle. The bus voltage step size when the bus voltage is higher than the bus voltage upper limit is ,in, 、 They are proportional coefficient 2, integral coefficient 2, It is the bus voltage upper limit error value of the previous control cycle.

3. A system according to any one of claims 1-2, wherein: It includes real-time voltage acquisition module, real-time power acquisition module, bus voltage step acquisition module, comparison module 1, comparison module 2, comparison module 3, iterative control module 1 and iterative control module 2: A real-time voltage acquisition module is configured to obtain the photovoltaic voltage and bus voltage of the current control cycle; A real-time power acquisition module is configured to acquire the photovoltaic power of the current control cycle; A bus voltage step length acquisition module is configured to acquire the bus voltage step length of the current control cycle; a first comparison module configured to compare the photovoltaic power of a current control cycle with the photovoltaic power of a previous control cycle; a second comparison module configured to compare the photovoltaic voltage of a current control cycle with the photovoltaic voltage of a previous control cycle; A comparison module three is configured to compare the bus voltage of the previous control cycle with the bus voltage reference value and the bus voltage upper limit value respectively; an iterative control module 1, configured to, if the photovoltaic power of the current control cycle is equal to the photovoltaic power of the previous control cycle, maintain the voltage step size unchanged; if the photovoltaic power of the current control cycle is less than the photovoltaic power of the previous control cycle and the photovoltaic voltage of the current control cycle is less than the photovoltaic voltage of the previous control cycle, reduce the photovoltaic voltage step size; if the photovoltaic voltage of the current control cycle is greater than the photovoltaic voltage of the previous control cycle, increase the photovoltaic voltage step size; if the photovoltaic power of the current control cycle is greater than the photovoltaic power of the previous control cycle and the photovoltaic voltage of the current control cycle is less than the photovoltaic voltage of the previous control cycle, increase the photovoltaic voltage step size; if the photovoltaic voltage of the current control cycle is greater than the photovoltaic voltage of the previous control cycle, reduce the photovoltaic voltage step size; an iterative control module 2, configured to increase the bus voltage step size if the bus voltage is lower than the bus voltage reference value, decrease the bus voltage step size if the bus voltage is higher than the bus voltage reference value and lower than the bus voltage upper limit, and decrease the photovoltaic voltage step size if the bus voltage is higher than the bus voltage upper limit; Repeat the above steps in each control cycle until the bus voltage is controlled within the bus voltage upper limit; The photovoltaic power value of the current control cycle is the product of the photovoltaic voltage and the photovoltaic current; The photovoltaic voltage step size is , the bus voltage step length when the bus voltage is lower than the bus voltage upper limit is ,in, 、 They are proportional coefficient 1, integral coefficient 1, is the bus voltage reference error value of the previous control cycle. The bus voltage step size when the bus voltage is higher than the bus voltage upper limit is ,in, 、 They are proportional coefficient 2, integral coefficient 2, It is the bus voltage upper limit error value of the previous control cycle.

4. The system according to claim 3, wherein: The iterative control module also includes a bus voltage step calculation module, which is configured to calculate and determine the bus voltage step based on the sum of the product of the proportional coefficient and the voltage reference / upper limit error value and the product of the integral coefficient and the integral value of the bus voltage reference / upper limit error value in the previous control cycle.

5. A system according to any one of claims 1-2, wherein: The invention comprises a computer-readable storage medium, an electronic device and a photovoltaic system.

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