Energy generation evaluation method of microinverter photovoltaic power station under replacement and repair strategy

Abstract

The present invention discloses a method for estimating the power generation of a microinverter photovoltaic power station under a replacement and repair strategy, comprising the following steps: simulating the operating state space of the photovoltaic power station under the repair strategy based on a continuous-time Markov chain, and describing the fault and repair state transition process in the operating state space; constructing a state transition rate matrix for the photovoltaic power station based on the fault and repair state transition process; determining the number of faults in the microinverter photovoltaic systems in the photovoltaic power station based on the state transition rate matrix; calculating the expected power generation loss of the photovoltaic power station based on the number of faults and the average hourly power generation of each microinverter photovoltaic system; and calculating the expected net power generation of the photovoltaic power station based on the expected power generation loss. By describing the fault and repair process of the photovoltaic power station through a continuous-time Markov chain, the present invention more accurately determines the expected power generation of the photovoltaic power station and the power generation loss of the photovoltaic power station under fault conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and more particularly to a method for estimating power generation of a micro-inverter photovoltaic power station under a replacement and repair strategy. Background Art

[0002] Photovoltaic power generation features low operating costs and high priority for grid access. With the increasing demand and output of photovoltaic power plants in recent years, high-reliability and long-life photovoltaic power plants have become a hot topic in research and application. The application of microinverters in photovoltaic power plants is one such application. Microinverters offer advantages such as compact system design, strong energy collection capabilities, high system efficiency, low mismatch losses between photovoltaic modules, and plug-and-play functionality. These advantages facilitate the expansion of photovoltaic power plants and provide technical support for the construction of large-scale photovoltaic power plants.

[0003] When a microinverter PV system fails at a random moment, spare parts must be ordered from the manufacturer to replace the faulty PV system in order to maintain the plant's power generation capacity. If spare parts cannot be promptly replaced, the PV plant's power production capacity will decline, and the system will lose a certain amount of power from the time the fault occurs until the replacement and repair are completed. Although PV systems are relatively reliable, as the scale of PV plants expands, the number of PV systems that fail over time will increase, and the power loss caused by downtime for replacement and repair will also increase.

[0004] Therefore, in order to more accurately evaluate the power generation capacity of a micro-inverter photovoltaic power station, how to provide a method for evaluating the power generation capacity of a micro-inverter photovoltaic power station while taking into account photovoltaic system fault repair is a technical problem that technicians in this field urgently need to solve. Summary of the Invention

[0005] In view of this, the present invention provides a method for estimating the power generation of a micro-inverter photovoltaic power station under a replacement and repair strategy. By describing the failure and repair process of the photovoltaic power station through a continuous-time Markov chain, the expected power generation of the photovoltaic power station and the power generation loss of the photovoltaic power station under a fault state can be more accurately determined.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for estimating power generation of a micro-inverter photovoltaic power station under a replacement and repair strategy includes the following steps:

[0008] The operating state space of the photovoltaic power station under the repair strategy is simulated based on the continuous-time Markov chain, and the fault and repair state transition process of the operating state space is described;

[0009] Based on the fault and repair state transition process, a state transition rate matrix of the photovoltaic power station is constructed;

[0010] determining the number of faults in the microinverter photovoltaic system in the photovoltaic power station based on the state transition rate matrix;

[0011] Calculating the expected power generation loss of the photovoltaic power station based on the number of faults and the average power generation per hour of each microinverter photovoltaic system;

[0012] Based on the expected power generation loss, the expected net power generation of the photovoltaic power station is calculated.

[0013] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a method for estimating the power generation of a micro-inverter photovoltaic power station under a replacement and repair strategy. The method can describe the fault repair random process of the micro-inverter photovoltaic power station through a continuous-time Markov chain, determine the mean number of photovoltaic system faults, and thus predict the expected power generation loss caused by the fault, and evaluate the power generation of the micro-inverter photovoltaic power station. The method has good applicability and is suitable for all micro-inverter photovoltaic power generation systems and similar products with this feature.

[0014] Furthermore, in the method for estimating power generation of a micro-inverter photovoltaic power station under the above replacement and repair strategy, the state transition rate matrix is ​​expressed as:

[0015]

[0016] Where N is the total number of micro-inverter photovoltaic systems in the photovoltaic power station; λ is the failure rate of the micro-inverter photovoltaic system in the photovoltaic power station; μ is the repair rate of the micro-inverter photovoltaic system in the photovoltaic power station; A is the state transition rate matrix of the continuous-time Markov chain; A[n,m] is the element in the nth row and mth column of the state transition rate matrix A.

[0017] Furthermore, in the above-mentioned method for estimating power generation of a micro-inverter photovoltaic power station under the replacement and repair strategy, the determining the number of faults of the micro-inverter photovoltaic system in the photovoltaic power station based on the state transition rate matrix includes:

[0018] determining a steady-state probability of the photovoltaic power station according to the state transition rate matrix;

[0019] The mean value of the number of failures of the micro-inverter photovoltaic system in the photovoltaic power station is obtained according to the steady-state probability.

[0020] Furthermore, in the method for estimating power generation of a micro-inverter photovoltaic power station under the above replacement and repair strategy, the steady-state probability satisfies the following equation:

[0021] πA=0

[0022] π0+π1+…+πN =1

[0023] Where, π=[π0,π1,…,π N ] represents the row vector of the steady-state probability of the micro-inverter photovoltaic system in the photovoltaic power station, π x , x=0,1,2…N, represents the probability of the microinverter photovoltaic system in state x, and x is the number of faults in the microinverter photovoltaic system under the repair strategy.

[0024] Furthermore, in the method for estimating the power generation of a micro-inverter photovoltaic power station under the above replacement and repair strategy, the calculation formula for the mean number of faults of the micro-inverter photovoltaic system in the photovoltaic power station is:

[0025] E(F)=π·[0,1,2,…,N]'

[0026] Where E(F) represents the mean number of microinverter photovoltaic system failures; [0,1,2,…,N]' represents the column vector consisting of the number of microinverter photovoltaic system failures in the photovoltaic power station; and ' represents the matrix transpose.

[0027] Furthermore, in the method for estimating power generation of a micro-inverter photovoltaic power station under the above replacement and repair strategy, the calculation formula for the expected power generation loss is as follows:

[0028]

[0029] Where E[LE] represents the expected power generation loss of the microinverter photovoltaic system; It represents the average power generated per hour by the micro-inverter system in the photovoltaic power station; T represents the duration of power generation by the micro-inverter photovoltaic system.

[0030] Furthermore, in the method for estimating power generation of a micro-inverter photovoltaic power station under the above replacement and repair strategy, the calculation formula for the expected net power generation is as follows:

[0031]

[0032] Where E[PP] represents the expected net power generation of the PV power station per hour. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0034] Figure 1The accompanying figure is a flow chart of a method for estimating power generation of a micro-inverter photovoltaic power station under a replacement and repair strategy provided by the present invention;

[0035] Figure 2 The accompanying drawing is a Markov state transition diagram of a micro-inverter photovoltaic system in a photovoltaic power station under the repair strategy provided by the present invention;

[0036] Figure 3 The accompanying drawing is a Markov state transition diagram of a micro-inverter photovoltaic system in a photovoltaic power station under a repair strategy in a specific application scenario provided by the present invention. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] like Figure 1 As shown, an embodiment of the present invention discloses a method for estimating power generation of a micro-inverter photovoltaic power station under a replacement and repair strategy, comprising the following steps:

[0039] S1. Based on the continuous-time Markov chain simulation, the operating state space of the photovoltaic power station under the repair strategy is simulated, and the fault and repair state transition process in the operating state space is described.

[0040] In this embodiment of the present invention, the installed capacity of a photovoltaic power station is N, meaning that the photovoltaic power station is composed of N microinverter photovoltaic systems. A microinverter photovoltaic system in this invention comprises components such as microinverters, photovoltaic solar panels, and assemblies. In this embodiment of the present invention, if a microinverter photovoltaic system fails, it will be repaired through replacement and maintenance. If repairs are made promptly, the number of microinverter photovoltaic systems can be maintained at the initial installed capacity, N. If system failures persist, the number of working microinverter photovoltaic systems will decrease as the number of failures increases.

[0041] The operating state space of the photovoltaic power station under the repair strategy can be simulated using a continuous-time Markov chain. The operating state space of the photovoltaic power station can be expressed as Ω, where Ω is {i|0≤i≤N,i=0,1,2…N}, and i is the number of micro-inverter photovoltaic systems that can currently operate in the micro-inverter photovoltaic power station under the repair strategy.

[0042] like Figure 2As shown in Figure 1, the initial inventory state of a PV power station is represented by N, which is the installed capacity of the PV power station. When a microinverter PV system fails, the number of working microinverter PV systems in the PV power station decreases by 1, and the PV power station transitions to state N-1. If the faulty microinverter PV system is repaired, the PV power station transitions back to state N. The failure rate is iλ, where i (0≤i≤N) is the number of working microinverter PV systems. The repair rate is (Ni)μ, and the PV power station ends at state 0.

[0043] S2. Based on the fault and repair state transition process, a state transition rate matrix of the photovoltaic power station is constructed.

[0044] Based on the obtained continuous-time Markov chain, the state transition rate matrix of the photovoltaic power station is abstracted. Based on the photovoltaic power station state transition process constructed by S1, the transition rate matrix A is established. The specific form is as follows:

[0045]

[0046] Where N is the total number of micro-inverter photovoltaic systems in the photovoltaic power station; λ is the failure rate of the micro-inverter photovoltaic system in the photovoltaic power station; μ is the repair rate of the micro-inverter photovoltaic system in the photovoltaic power station; A is the state transition rate matrix of the continuous-time Markov chain; A[n,m] is the element in the nth row and mth column of the state transition rate matrix A.

[0047] S3. Determine the number of faults in the micro-inverter photovoltaic system in the photovoltaic power station based on the state transition rate matrix. Specifically:

[0048] S31. Determine the steady-state probability of the photovoltaic power station according to the state transition rate matrix.

[0049] Use π=[π0,π1,…,π N ] represents the row vector of the steady-state probability of the micro-inverter photovoltaic system in the photovoltaic power station, π x (x=0,1,2…N), represents the probability of the microinverter photovoltaic system in state x, and x is the number of faults in the photovoltaic system under the repair strategy.

[0050] The steady-state probability π satisfies the following equation:

[0051] πA=0

[0052] π0+π1+…+π N =1

[0053] S32. Obtain the mean number of faults in the micro-inverter photovoltaic system in the photovoltaic power station based on the steady-state probability. The specific calculation formula is as follows:

[0054] E(F)=π·[0,1,2,…,N]'

[0055] Where E(F) represents the mean number of microinverter photovoltaic system failures; [0,1,2,…,N]' represents the column vector consisting of the number of microinverter photovoltaic system failures in the photovoltaic power station; and ' represents the matrix transpose.

[0056] S4. Calculate the expected power generation loss of the photovoltaic power station based on the number of faults and the average power generation per hour of each micro-inverter photovoltaic system.

[0057] In the embodiment of the present invention, the expected power generation loss of the micro-inverter photovoltaic system is related to the hourly power generation of the photovoltaic system and the average number of system failures. Therefore, the expected power generation loss E[LE] can be calculated. The specific formula is as follows:

[0058]

[0059] In the above formula, is the average hourly power generation of the microinverter photovoltaic system, It can be obtained based on the annual power generation statistics of the micro-inverter photovoltaic power generation system or the rated nominal power of the micro-inverter photovoltaic system. x is the steady-state probability when the number of failures of the microinverter photovoltaic system is x, and T is the power generation duration of the microinverter photovoltaic system.

[0060] S5. Calculate the expected net power generation of the photovoltaic power station based on the expected power generation loss. The calculation formula for the expected net power generation is as follows:

[0061]

[0062] Where E[PP] represents the expected net power generation of the PV power station per hour.

[0063] The specific embodiments of the present invention are further described below with reference to specific examples.

[0064] S1. Establish the operating state space of the PV power station under the replacement and repair strategy. The installed capacity of the PV system is N = 100,000. Use a continuous-time Markov chain to simulate the operating state space of the PV power station under the repair strategy. The operating state space of the PV power station can be expressed as Ω, where Ω is {i|0≤i≤100,000, i=0,1,2…N}, and i is the number of microinverter PV systems currently capable of operation in the microinverter PV power station under the repair strategy.

[0065] A continuous-time Markov chain is used to describe the random process of failure and repair of the microinverter photovoltaic system. The state transition rates in this example are shown in Table 1:

[0066] Table 1 Equipment state transition rate

[0067]

[0068] The state transfer process is as follows Figure 3 As shown, the initial state of the PV power station is N = 100,000, which is the installed capacity of the PV power station. When a unit fails, the number of working units in the PV power station decreases by 1, and the PV power station transitions to state N-1. If the failed unit is repaired at this time, the PV power station transitions back to state N. The failure rate is iλ, where i (0 ≤ i ≤ 100,000) is the number of working units. The repair rate is (Ni)μ. The system ends at state 0.

[0069] S2, based on the obtained continuous-time Markov chain, the state transition rate matrix of the photovoltaic system is calculated. The transition rate matrix A is established based on the constructed photovoltaic power station state transition process. The specific form is as follows:

[0070]

[0071] Where A[n,m] represents the element in the nth row and mth column of the transfer rate matrix A.

[0072] S3, according to the state transition rate matrix obtained in S2, determine the state probability of the micro-inverter photovoltaic system. 100000 ] represents the row vector of steady-state probability, π x (x=0,1,2…100000) represents the probability of the microinverter photovoltaic system in state x, and x is the number of faults in the photovoltaic system under the repair strategy.

[0073] The steady-state probability π satisfies the following equation:

[0074] πA=0

[0075] π0+π1+…+π 100000 =1

[0076] Where A is the transition rate matrix of the continuous-time Markov chain.

[0077] According to the steady-state probability π of the micro-inverter photovoltaic system, the mean number of faults E(F) of the photovoltaic system is obtained:

[0078] E(F)=π·[0,1,2,…,100000] T

[0079] Among them, [0,1,2,…,100000] T is a column vector consisting of the number of PV system faults.

[0080] Substituting the steady-state distribution π obtained in S3 into the calculation formula of E(F) yields the following result:

[0081] E(F)=16666.7

[0082] S4, calculate the expected power generation loss E[LE] of the micro-inverter photovoltaic system. The expected power generation loss E[LE] of the photovoltaic system is expressed as follows:

[0083]

[0084] In the above formula is the average hourly power generation of the micro-inverter photovoltaic system, which is obtained based on the annual power generation statistics of the micro-inverter photovoltaic system. T=8760h is the duration of photovoltaic system power generation. This is the E(F) required by S3. Substituting it into the above formula, we can get: E[LE]=1.6486×10 7 kWh.

[0085] S5, calculate the expected net power generation E[PP] of the photovoltaic power station.

[0086] The expected net power generation E[PP] of a photovoltaic power station is shown as follows:

[0087]

[0088] The average hourly power generation of the microinverter photovoltaic system obtained in S4 is Substituting the expected power generation loss E[LE] of the micro-inverter photovoltaic system into the above formula, the expected net power generation of the photovoltaic power station is E[PP]=8.2432×10 7 kWh.

[0089] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0090] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for estimating power generation of a micro-inverter photovoltaic power station under a replacement and repair strategy, characterized in that: The following steps are involved: The operating state space of the photovoltaic power station under the repair strategy is simulated based on the continuous-time Markov chain, and the fault and repair state transition process of the operating state space is described; Based on the fault and repair state transition process, a state transition rate matrix of the photovoltaic power station is constructed; the state transition rate matrix is ​​expressed as: Where N is the total number of micro-inverter photovoltaic systems in the photovoltaic power station; λ is the failure rate of the micro-inverter photovoltaic system in the photovoltaic power station; μ is the repair rate of the micro-inverter photovoltaic system in the photovoltaic power station; A is the state transition rate matrix of the continuous-time Markov chain; A[n,m] is the element in the nth row and mth column of the transition rate matrix A; determining the number of faults in the microinverter photovoltaic system in the photovoltaic power station based on the state transition rate matrix; Calculating the expected power generation loss of the photovoltaic power station based on the number of faults and the average power generation per hour of each microinverter photovoltaic system; Calculating the expected net power generation of the photovoltaic power station based on the expected power generation loss; The determining the number of faults of the micro-inverter photovoltaic system in the photovoltaic power station based on the state transition rate matrix includes: The steady-state probability of the photovoltaic power station is determined according to the state transition rate matrix; the steady-state probability satisfies the following equation: πA＝0 π0+π1+…+π N ＝1 Where, π=[π0,π1,…,π N ] represents the row vector of the steady-state probability of the micro-inverter photovoltaic system in the photovoltaic power station, π x , x=0,1,2…N, represents the probability of the microinverter photovoltaic system in state x, and x is the number of faults in the microinverter photovoltaic system under the repair strategy; According to the steady-state probability, the mean number of failures of the micro-inverter photovoltaic system in the photovoltaic power station is obtained, and the calculation formula is: E(F)=π·[0,1,2,…,N]' Where E(F) represents the mean number of faults in the microinverter photovoltaic system; [0, 1, 2, …, N]' represents the column vector consisting of the number of faults in the microinverter photovoltaic system in the photovoltaic power station; ' represents the matrix transpose; The calculation formula of the expected power generation loss is as follows: Where E[LE] represents the expected power generation loss of the microinverter photovoltaic system; It represents the average power generated per hour by the micro-inverter system in the photovoltaic power station; T represents the duration of power generation by the micro-inverter photovoltaic system; The calculation formula for the expected net power generation is as follows: Where E[PP] represents the expected net power generation of the PV power station per hour.

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