Photovoltaic power generation grid-connected operation balance adjustment method and system

Abstract

The invention relates to the technical field of renewable energy sources, in particular to a photovoltaic power generation grid-connected operation balance adjustment method and system, and the method comprises the steps: respectively collecting the output power of a photovoltaic power generation system, the power grid demand power and the photovoltaic power generation data of a user in a current time period; determining the theoretical output power of the photovoltaic power generation system and the historical same-period monthly generating capacity of the user, and determining the target generating capacity; establishing a target function for adjusting the output power of the photovoltaic power generation system; initializing a weight factor of the objective function, and obtaining a new adjustment value of the output power according to a partial derivative of the output power of the photovoltaic power generation system; and updating the target function, dynamically adjusting the weight factor according to the deviation between the monthly cumulative generating capacity and the target generating capacity, and determining the maximum output power and the target function of the final photovoltaic power generation system. The output power of the photovoltaic power generation system is maximized, the monthly average generating capacity of a user is kept consistent with historical same-period generating capacity data, and the balance and coordination of supply and demand parties of a power grid are realized.

Description

Technical Field

[0001] The present invention relates to the field of renewable energy technology, and in particular to a photovoltaic power generation grid-connected operation balancing regulation method and system. Background Art

[0002] With the rapid development of renewable energy, especially the rise of the photovoltaic industry, photovoltaic grid-connected power generation has become an important direction for energy structure adjustment and green development. However, the randomness and volatility of photovoltaic power generation have brought great challenges to the power grid's absorption. During the peak period of photovoltaic power generation, a large amount of photovoltaic power will flow into the power grid, which may lead to instability in the voltage and frequency of the power grid; while during the off-peak period of photovoltaic power generation, the photovoltaic power generation is not enough to meet the load demand, which may lead to energy waste.

[0003] During the peak period of photovoltaic power generation, in order to ensure the stable operation of the power grid, the existing methods usually take the approach of limiting the inverter power output or directly cutting off the photovoltaic power generation equipment. Although this approach can ensure the stability of the voltage and frequency of the power grid, it also leads to large fluctuations in photovoltaic power generation. This volatility not only affects the power supply quality of the power grid, but also has an unnecessary impact on the power demand of the power grid. At the same time, more importantly, this approach means that the economic interests of the owners of photovoltaic power generation equipment have been damaged. Because the user's photovoltaic power generation equipment cannot operate at full capacity during the most favorable time, it cannot achieve the maximum economic benefits.

[0004] Therefore, studying new methods to balance the randomness and volatility of photovoltaic power generation while protecting the economic interests of photovoltaic power generation equipment owners has become a pressing issue in this field. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a photovoltaic power generation grid-connected operation balance adjustment method, comprising:

[0006] Collect the output power of the photovoltaic power generation system, the power demand of the power grid, and the photovoltaic power generation data of the user in the current period respectively, and obtain the monthly cumulative power generation of the user based on the statistics of the photovoltaic power generation data of the user;

[0007] Determine the theoretical output power of the photovoltaic power generation system and the user's historical monthly power generation in the same period, and determine the target power generation up to the current period based on the user's historical monthly power generation in the same period;

[0008] Based on the output power of the photovoltaic power generation system, the monthly cumulative power generation and the target power generation of the user, an objective function for regulating the output power of the photovoltaic power generation system is established;

[0009] Initialize the weight factor of the objective function, calculate the partial derivative of the objective function with respect to the output power of the photovoltaic power generation system, and obtain a new adjustment value of the output power according to the partial derivative of the output power of the photovoltaic power generation system;

[0010] The new adjusted value of the output power is updated to the objective function, the user's monthly cumulative power generation is obtained, and the weight factor is dynamically adjusted according to the deviation between the monthly cumulative power generation and the target power generation, and iterative calculation is performed to determine the maximum output power and objective function of the final photovoltaic power generation system according to the preset iteration termination condition.

[0011] In a specific implementation, after determining the theoretical output power of the photovoltaic power generation system and the historical monthly power generation of the user in the same period, it also includes setting constraints on the output power and the monthly cumulative power generation according to the theoretical output power and the historical monthly power generation in the same period.

[0012] The constraints include:

[0013] The output power constraint of the photovoltaic power generation system is that the output power of the photovoltaic power generation system is greater than or equal to zero and less than the maximum theoretical output power.

[0014] The constraint condition of the user's monthly cumulative power generation is that the user's monthly cumulative power generation falls within the historical monthly power generation fluctuation range.

[0015] The objective function formula is:

[0016] f=alpha×max(P_{PV})+beta×(G-G_{target})^2,

[0017] Among them, f is the objective function; alpha and beta represent weight factors respectively, P_{PV} represents the output power of the photovoltaic power generation system; G represents the user's monthly cumulative power generation; G_{target} represents the target power generation.

[0018] According to the partial derivative of the output power of the photovoltaic power generation system, the new adjustment value of the output power is obtained, and the formula is:

[0019]

[0020]

[0021] Where P_{PV}^{new} represents the new value of the output power; P_{PV}^{old} represents the original output power; lambda represents the iteration step coefficient; f represents the objective function; max(P_{PV}) represents the maximum output power of the photovoltaic power generation system; is the partial derivative of the objective function with respect to the output power of the photovoltaic power generation system.

[0022] The weight factor is dynamically adjusted according to the deviation between the monthly cumulative power generation and the monthly average power generation, and the specific operation is as follows:

[0023] Compare the monthly cumulative power generation with the target power generation. If the monthly cumulative power generation is less than the target power generation, the monthly cumulative power generation constraint condition adds the allowed power generation fluctuation range; if the monthly cumulative power generation is greater than or equal to the target power generation, the monthly cumulative power generation constraint condition removes the allowed power generation fluctuation range.

[0024] Based on the adjusted monthly cumulative power generation constraint condition, the constraint judgment of the monthly cumulative power generation is performed. If the monthly cumulative power generation is greater than the upper limit of the interval of the monthly cumulative power generation constraint condition, the weight factor of the output power is increased by one step, and the weight factor of the monthly cumulative power generation is reduced by one step; if the monthly cumulative power generation is less than the lower limit of the interval of the monthly cumulative power generation constraint condition, the weight factor of the output power is reduced by one step, and the weight factor of the monthly cumulative power generation is increased by one step;

[0025] According to the dynamically adjusted output power weight factor, the output power of the photovoltaic power generation system is compared with the power demand of the power grid, and the weight factor is adjusted twice.

[0026] In a specific implementation, the output power of the photovoltaic power generation system is compared with the power demanded by the power grid, and a secondary adjustment of the weight factor is performed, specifically:

[0027] If the output power of the photovoltaic power generation system under the weight factor is equal to the power demanded by the power grid, the weight factor of the output power will not be adjusted;

[0028] If the output power is less than the power required by the grid, the weight factor of the output power is increased twice until the output power is equal to the power required by the grid;

[0029] If the output power is greater than the grid demand power, the output power weight factor is reduced twice until the output power P_{PV} is equal to the grid demand power D.

[0030] The iteration termination condition includes that the monthly cumulative power generation falls within the interval range of the monthly cumulative power generation constraint condition, or the number of iterations reaches a preset number, and the change in the objective function is less than the amplitude threshold, then the iteration is stopped.

[0031] On the other hand, a photovoltaic power generation grid-connected operation balancing regulation system is provided, comprising:

[0032] The data collection module collects the output power of the photovoltaic power generation system, the power demand of the power grid, and the photovoltaic power generation data of the user in the current period, and obtains the monthly cumulative power generation of the user based on the statistics of the photovoltaic power generation data of the user;

[0033] The data collection module is also used to determine the theoretical output power of the photovoltaic power generation system and the historical monthly power generation of the user in the same period, and determine the target power generation up to the current period according to the historical monthly power generation of the user in the same period;

[0034] The target module establishes the target function for adjusting the output power of the photovoltaic power generation system based on the output power of the photovoltaic power generation system, the monthly cumulative power generation of the user and the target power generation;

[0035] The calculation module initializes the weight factor of the objective function, calculates the partial derivative of the objective function with respect to the output power of the photovoltaic power generation system, and obtains a new adjustment value of the output power according to the partial derivative of the output power of the photovoltaic power generation system;

[0036] The iterative adjustment module updates the adjusted new value of the output power to the objective function, obtains the user's monthly cumulative power generation, and dynamically adjusts the weight factor according to the deviation between the monthly cumulative power generation and the target power generation, performs iterative calculation, and determines the maximum output power and objective function of the final photovoltaic power generation system according to the preset iteration termination conditions.

[0037] Beneficial effects: The present invention is a photovoltaic power generation grid-connected operation balance adjustment method and system, which can ensure the maximization of the output power of the photovoltaic power generation system under the conditions of stability and safety of the power grid operation. By automatically adjusting the power output of the photovoltaic power generation system to match it with the demand and load changes of the power grid, and taking the user's power generation into consideration, the user's monthly average power generation is maintained consistent with the historical power generation data for the same period, ensuring the stability of photovoltaic power generation in each period, thereby protecting the user's economic benefits and achieving balance and coordination between the supply and demand sides of the power grid. DETAILED DESCRIPTION

[0038] Exemplary embodiments of the present disclosure will be described in more detail below.

[0039] The present embodiment provides a method for balancing and regulating the grid-connected operation of photovoltaic power generation. Under the premise of ensuring the stability and safety of the grid operation, the photovoltaic power generation system inverter is regulated to maximize its output power, and the power generation of the users of the photovoltaic power generation equipment is taken into consideration. The monthly average power generation of the users is regulated to be the same as the power generation data of the same period in history, so as to achieve the balance and coordination of supply and demand of the grid when the photovoltaic power generation system is connected to the grid.

[0040] The specific steps of the method are as follows:

[0041] Step 1: Collect the output power of the photovoltaic power generation system, the power demand of the power grid, and the photovoltaic power generation data of the user in the current period, and obtain the monthly cumulative power generation of the user based on the photovoltaic power generation data of the user;

[0042] When the photovoltaic power generation system operates in parallel with the power grid, the electricity generated by the user's photovoltaic power generation equipment is stored in the energy storage device, and the electric energy of the energy storage device is output to the power grid in parallel through the inverter of the photovoltaic power generation system.

[0043] The whole day is divided into 24-hour periods, and the output power PPV of the photovoltaic power generation system, the real-time demand power D of the power grid, and the photovoltaic power generation amount G(t) of the user to whom the photovoltaic power generation equipment belongs are collected respectively, and the monthly cumulative power generation amount G of the user is statistically obtained according to the photovoltaic power generation amount data of the user.

[0044] Among them, when the power grid is operating, stability constraints are set for the demand power of the power grid, including the maximum demand power Dmax and the minimum demand power Dmin of the power grid, Dmin < D < Dmax, that is, the real-time demand power D of the power grid must be between the minimum demand Dmin and the maximum demand Dmax to ensure the stability of the power grid. If the power grid demand power is lower than the minimum value, it may cause unstable operation or insufficient supply of the power grid; if the demand power exceeds the maximum value, it may cause overload and equipment damage.

[0045] Step 2: Determine the theoretical output power of the photovoltaic power generation system and the user's historical monthly power generation in the same period, and determine the target power generation amount up to the current period according to the user's historical monthly power generation in the same period;

[0046] Determine the theoretical output power PPV,max of the photovoltaic power generation system and the user's historical monthly power generation amount Ghistory through the power grid operation data.

[0047] The said Step 2 also includes setting constraint conditions for the output power and the monthly cumulative power generation amount according to the theoretical output power of the photovoltaic power generation system and the user's historical monthly power generation amount in the same period.

[0048] The constraint condition for the output power of the photovoltaic power generation system is: 0 ≤ PPV < PPV,max. The output power PPV of the photovoltaic power generation system must be greater than or equal to zero, and the real-time output power PPV of the photovoltaic power generation system must be less than its maximum theoretical output power PPV,max.

[0049] The constraint condition for the user's monthly cumulative power generation amount is: Ghistory - epsilon < G < Ghistory + epsilon, where epsilon is the allowable power generation fluctuation range.

[0050] The user's monthly cumulative power generation G must be between the historical monthly power generation G_{history} minus an allowed fluctuation range epsilon and the historical monthly power generation G_{history} plus epsilon. This constraint allows the user's photovoltaic power generation to fluctuate to adapt to different weather conditions and seasonal changes, but overall it still needs to remain near the historical average level.

[0051] Step 3: Based on the output power of the photovoltaic power generation system, the monthly cumulative power generation and the target power generation of the user, an objective function for adjusting the output power of the photovoltaic power generation system is established;

[0052] By setting the goal of maximizing the output power of the photovoltaic power generation system as the first goal and keeping the user's monthly cumulative power generation equal to the monthly average power generation in the same period of the year as the second goal, the objective function is established based on the output power P_{PV} of the photovoltaic power generation system, the user's monthly cumulative power generation G and the target power generation G_{target}, and the formula is as follows:

[0053] f=alpha×max(P_{PV})+beta×(G-G_{target})^2,

[0054] Among them, alpha and beta represent weight factors, which are used to adjust the priority of maximizing photovoltaic power generation and user photovoltaic power generation.

[0055] Step 4, initialize the weight factor of the objective function, calculate the partial derivative of the objective function with respect to the output power of the photovoltaic power generation system, and obtain the new adjustment value of the output power according to the partial derivative of the output power of the photovoltaic power generation system;

[0056] The formula for calculating the partial derivative of the objective function with respect to the output power of the photovoltaic power generation system is:

[0057]

[0058] Where f is the objective function; max(P_{PV}) represents the maximum output power of the photovoltaic power generation system; It is the partial derivative of the objective function with respect to the output power of the photovoltaic power generation system, which represents the conversion rate of the objective function with respect to the output power.

[0059] The output power value is adjusted according to the partial derivative of the output power of the photovoltaic power generation system. The formula is:

[0060]

[0061] Where P_{PV}^{new} represents the new value of the output power; P_{PV}^{old} is the original output power; lambda represents the iteration step coefficient.

[0062] Step 5, updating the adjusted new value of the output power to the objective function, obtaining the user's monthly cumulative power generation, and dynamically adjusting the weight factor according to the deviation between the monthly cumulative power generation and the target power generation, performing iterative calculation, and determining the maximum output power and objective function of the final photovoltaic power generation system according to the preset iteration termination condition;

[0063] The output power of the photovoltaic power generation system is updated according to the new value of the output power adjustment, and the monthly cumulative power generation of the user is monitored and obtained. According to the deviation between the monthly cumulative power generation and the monthly average power generation, the weight factor is dynamically adjusted. The specific operation is as follows:

[0064] S5.1. Compare the monthly cumulative power generation G with the target power generation G_{target}.

[0065] If the monthly cumulative power generation G is less than the target power generation G_{target}, the monthly cumulative power generation constraint condition is added with the allowed power generation fluctuation range;

[0066] If the monthly cumulative power generation G is greater than or equal to the target power generation G_{target}, the monthly cumulative power generation constraint condition removes the additional allowed power generation fluctuation range;

[0067] S5.2. Based on the adjusted monthly cumulative power generation constraint condition, make a constraint judgment on the monthly cumulative power generation.

[0068] If the monthly cumulative power generation G is greater than the upper limit of the interval of the monthly cumulative power generation constraint, it means that the monthly cumulative power generation G exceeds the target power generation G_{target}, then the alpha weight factor is increased by one step, and the beta weight factor is decreased by one step to reduce the increase in power generation and return to the target power generation to ensure the stability of the output power;

[0069] If the monthly cumulative power generation G is less than the lower limit of the interval of the monthly cumulative power generation constraint, it means that the monthly cumulative power generation G is lower than the target power generation G_{target}, then the alpha weight factor is reduced by one step and the beta weight factor is increased by one step to increase the photovoltaic power generation;

[0070] S5.3, according to the dynamically adjusted weight factor alpha, the output power of the photovoltaic power generation system is compared with the power demand of the power grid, and the weight factor is adjusted twice;

[0071] If the output power P_{PV} of the photovoltaic power generation system under the weight factor alpha is equal to the grid demand power D, the weight factor alpha is not adjusted;

[0072] If the output power P_{PV} is less than the grid demand power D, the weight factor alpha is increased twice until the output power P_{PV} is equal to the grid demand power D;

[0073] If the output power P_{PV} is greater than the grid demand power D, the weight factor alpha is reduced quadratically until the output power P_{PV} is equal to the grid demand power D.

[0074] The objective function is updated according to the dynamically adjusted weight factor, and the partial derivative is re-iteratively calculated to update the new adjustment value P_{PV}^{new} of the output power. The iteration is stopped according to the preset iteration termination condition. The iteration termination condition includes that the monthly cumulative power generation G falls within the interval range of the monthly cumulative power generation constraint condition, or the number of iterations reaches the preset number, and the change of the objective function f is less than the amplitude threshold, then the iteration is stopped.

[0075] The objective function after stopping iteration is output, and the adjusted new value of the output power of the objective function is the maximum output power of the photovoltaic power generation system that meets the first objective and the second objective.

[0076] At the same time, the method also includes re-performing steps 1 to 5 when entering the next time period to adjust the objective function.

[0077] In addition, a photovoltaic power generation grid-connected operation balancing regulation system is also provided, including:

[0078] The data collection module collects the output power of the photovoltaic power generation system, the power demand of the power grid, and the photovoltaic power generation data of the user in the current period, and obtains the monthly cumulative power generation of the user based on the statistics of the photovoltaic power generation data of the user;

[0079] The data collection module is also used to determine the theoretical output power of the photovoltaic power generation system and the historical monthly power generation of the user in the same period, and determine the target power generation up to the current period according to the historical monthly power generation of the user in the same period;

[0080] The target module establishes the target function for adjusting the output power of the photovoltaic power generation system based on the output power of the photovoltaic power generation system, the monthly cumulative power generation of the user and the target power generation;

[0081] The calculation module initializes the weight factor of the objective function, calculates the partial derivative of the objective function with respect to the output power of the photovoltaic power generation system, and obtains a new adjustment value of the output power according to the partial derivative of the output power of the photovoltaic power generation system;

[0082] The iterative adjustment module updates the adjusted new value of the output power to the objective function, obtains the user's monthly cumulative power generation, and dynamically adjusts the weight factor according to the deviation between the monthly cumulative power generation and the target power generation, performs iterative calculation, and determines the maximum output power and objective function of the final photovoltaic power generation system according to the preset iteration termination conditions.

Claims

1. A photovoltaic power generation grid-connected operation balance adjustment method, characterized in that: include: Collect the output power of the photovoltaic power generation system, the power demand of the power grid, and the photovoltaic power generation data of the user in the current period respectively, and obtain the monthly cumulative power generation of the user based on the statistics of the photovoltaic power generation data of the user; Determine the theoretical output power of the photovoltaic power generation system and the user's historical monthly power generation in the same period, and determine the target power generation up to the current period based on the user's historical monthly power generation in the same period; Based on the output power of the photovoltaic power generation system, the monthly cumulative power generation and the target power generation of the user, an objective function for regulating the output power of the photovoltaic power generation system is established; Initialize the weight factor of the objective function, calculate the partial derivative of the objective function with respect to the output power of the photovoltaic power generation system, and obtain a new adjustment value of the output power according to the partial derivative of the output power of the photovoltaic power generation system; The new adjusted value of the output power is updated to the objective function, the user's monthly cumulative power generation is obtained, and the weight factor is dynamically adjusted according to the deviation between the monthly cumulative power generation and the target power generation, and iterative calculation is performed to determine the maximum output power and objective function of the final photovoltaic power generation system according to the preset iteration termination condition.

2. The photovoltaic power generation grid-connected operation balance adjustment method according to claim 1, characterized in that: After determining the theoretical output power of the photovoltaic power generation system and the historical monthly power generation of the user in the same period, the method further includes setting constraints on the output power and the monthly cumulative power generation according to the theoretical output power and the historical monthly power generation in the same period.

3. The photovoltaic power generation grid-connected operation balance adjustment method according to claim 2 is characterized in that: The constraints include: The output power constraint of the photovoltaic power generation system is that the output power of the photovoltaic power generation system is greater than or equal to zero and less than the maximum theoretical output power. The constraint condition of the user's monthly cumulative power generation is that the user's monthly cumulative power generation falls within the historical monthly power generation fluctuation range.

4. The photovoltaic power generation grid-connected operation balance adjustment method according to claim 1, characterized in that: The objective function formula is: f=alpha×max(P_{PV})+beta×(G-G_{target})^2, Among them, f is the objective function; alpha and beta represent weight factors respectively, P_{PV} represents the output power of the photovoltaic power generation system; G represents the user's monthly cumulative power generation; G_{target} represents the target power generation.

5. The photovoltaic power generation grid-connected operation balance adjustment method according to claim 4 is characterized in that: The new adjustment value of the output power is obtained according to the partial derivative of the output power of the photovoltaic power generation system, and the formula is: Where P_{PV}^{new} represents the new value of the output power; P_{PV}^{old} represents the original output power; lambda represents the iteration step coefficient; f represents the objective function; max(P_{PV}) represents the maximum output power of the photovoltaic power generation system; is the partial derivative of the objective function with respect to the output power of the photovoltaic power generation system.

6. The photovoltaic power generation grid-connected operation balance adjustment method according to claim 3, characterized in that: The weight factor is dynamically adjusted according to the deviation between the monthly cumulative power generation and the monthly average power generation, and the specific operation is as follows: Compare the monthly cumulative power generation with the target power generation. If the monthly cumulative power generation is less than the target power generation, the monthly cumulative power generation constraint condition adds the allowed power generation fluctuation range; if the monthly cumulative power generation is greater than or equal to the target power generation, the monthly cumulative power generation constraint condition removes the allowed power generation fluctuation range. Based on the adjusted monthly cumulative power generation constraint condition, the constraint judgment of the monthly cumulative power generation is performed. If the monthly cumulative power generation is greater than the upper limit of the interval of the monthly cumulative power generation constraint condition, the weight factor of the output power is increased by one step, and the weight factor of the monthly cumulative power generation is reduced by one step; if the monthly cumulative power generation is less than the lower limit of the interval of the monthly cumulative power generation constraint condition, the weight factor of the output power is reduced by one step, and the weight factor of the monthly cumulative power generation is increased by one step; According to the dynamically adjusted output power weight factor, the output power of the photovoltaic power generation system is compared with the power demand of the power grid, and the weight factor is adjusted twice.

7. The photovoltaic power generation grid-connected operation balance adjustment method according to claim 6, characterized in that: The output power of the photovoltaic power generation system is compared with the power required by the power grid, and the weight factor is adjusted twice, specifically: If the output power of the photovoltaic power generation system under the weight factor is equal to the power demanded by the power grid, the weight factor of the output power will not be adjusted; If the output power is less than the power required by the grid, the weight factor of the output power is increased twice until the output power is equal to the power required by the grid; If the output power is greater than the grid demand power, the output power weight factor is reduced twice until the output power P_{PV} is equal to the grid demand power D.

8. The photovoltaic power generation grid-connected operation balance adjustment method according to claim 1, characterized in that: The iteration termination condition includes that the monthly cumulative power generation falls within the interval range of the monthly cumulative power generation constraint condition, or the number of iterations reaches a preset number, and the change in the objective function is less than the amplitude threshold, then the iteration is stopped.

9. A photovoltaic power generation grid-connected operation balance regulation system, characterized in that: include: The data collection module collects the output power of the photovoltaic power generation system, the power demand of the power grid, and the photovoltaic power generation data of the user in the current period, and obtains the monthly cumulative power generation of the user based on the statistics of the photovoltaic power generation data of the user; The data collection module is also used to determine the theoretical output power of the photovoltaic power generation system and the historical monthly power generation of the user in the same period, and determine the target power generation up to the current period according to the historical monthly power generation of the user in the same period; The target module establishes the target function for adjusting the output power of the photovoltaic power generation system based on the output power of the photovoltaic power generation system, the monthly cumulative power generation of the user and the target power generation; The calculation module initializes the weight factor of the objective function, calculates the partial derivative of the objective function with respect to the output power of the photovoltaic power generation system, and obtains a new adjustment value of the output power according to the partial derivative of the output power of the photovoltaic power generation system; The iterative adjustment module updates the adjusted new value of the output power to the objective function, obtains the user's monthly cumulative power generation, and dynamically adjusts the weight factor according to the deviation between the monthly cumulative power generation and the target power generation, performs iterative calculation, and determines the maximum output power and objective function of the final photovoltaic power generation system according to the preset iteration termination conditions.

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