CN114418424A - An evaluation method of photovoltaic power generation capacity considering initial inventory configuration - Google Patents

Abstract

The invention discloses a photovoltaic power station power generation amount evaluation method considering initial inventory configuration, which comprises the following steps of: establishing a spare part balance relational expression of the photovoltaic power generation system of the micro inverter considering initial inventory configuration; describing an inventory level state of the micro-inverter photovoltaic power generation system by using a continuous time Markov chain; solving a Markov state transition rate matrix of the photovoltaic power generation system of the micro inverter according to the inventory level state, the fault rate and the delivery rate; determining the steady state time of the inventory level state of the photovoltaic power generation system of the micro inverter, and expressing the relation between the steady state probability and the transfer rate; solving the steady state probability of the inventory level state of the photovoltaic power generation system of the micro inverter; calculating the expected power generation loss of the whole photovoltaic power station according to the calculated steady-state probability of each state; the corresponding expected net amount of power generation is evaluated. The scheme has good applicability and is suitable for all micro-inverter photovoltaic power generation systems with the characteristics and similar products.

Description

An evaluation method of photovoltaic power generation capacity considering initial inventory configuration

technical field

The invention relates to the fields of power generation performance evaluation, inventory theory, continuous-time Markov chain and the like of a micro-inverter photovoltaic power generation system. In particular, it relates to a method for evaluating the power generation capacity of photovoltaic power plants considering the initial inventory configuration.

Background technique

Renewable energy has been paid more and more attention all over the world, and photovoltaic power generation technology is an important field in renewable energy technology. The demand for photovoltaic power generation technology promotes the development and application of new technologies. Micro-inverters with high reliability and long life are one of the new technologies widely used in photovoltaic power generation systems in recent years. Since the micro-inverter is integrated with the photovoltaic panel in one installation space, the system design is very compact, which enhances the flexibility and modularity of the system, and has strong expandability. The micro-inverter photovoltaic power generation system leads the trend of photovoltaic power generation, and the installation scale in the future will become larger and larger. The wide application of this photovoltaic power generation system will relieve the resource, environmental and economic pressure brought by traditional thermal power generation to a certain extent, help to achieve the goal of carbon peaking and carbon neutrality in my country, and promote the energy conservation and emission reduction of the whole society. business process.

The photovoltaic power station is composed of multiple micro-inverter photovoltaic power generation systems, and each micro-inverter photovoltaic power generation system is composed of a photovoltaic module and a micro-inverter. When the photovoltaic power station is put into operation and in use, the failure of the photovoltaic power generation system will bring related maintenance work. When a micro-inverter photovoltaic power generation system fails at a random moment, the power generation capacity of the photovoltaic power station will be reduced. will decline. Therefore, the power generation capacity of the photovoltaic power station has a strong correlation with the normal operation of each micro-inverter photovoltaic power generation system. Due to the large number of micro-inverter photovoltaic power generation systems installed in photovoltaic power stations, the occurrence of faults will increase, and the faults will lead to the shutdown of the micro-inverter photovoltaic power generation system modules, resulting in the loss of power generation of the photovoltaic power station. In order to avoid such losses, it is necessary to set up a warehouse to store spare parts. When the working micro-inverter photovoltaic power generation system fails, the spare parts in the warehouse are used for replacement and maintenance, so as to reduce downtime and reduce the loss caused by power generation. When there are no spare parts in the warehouse, if the working micro-inverter photovoltaic power generation system fails, there will be no spare parts to replace, which will cause a loss of power generation. Therefore, in the spare parts inventory strategy, when the number of spare parts in the warehouse is reduced to a certain threshold, it is necessary to order spare parts to replenish the warehouse inventory. After the ordered spare parts arrive, replace the faulty micro-inverter photovoltaic power generation system to minimize downtime. At this time, it is necessary to consider the spare parts inventory strategy to evaluate the power generation of the micro-inverter photovoltaic power station.

Therefore, the above problems have not attracted people's attention, but the warehouse is managed based on experience to minimize the shutdown of the micro-inverter photovoltaic power generation system due to insufficient storage of spare parts. How to reasonably balance spare parts inventory and inventory control conditions to achieve The evaluation of the power generation of photovoltaic power plants needs to be solved urgently.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to propose a method for evaluating the power generation of photovoltaic power plants considering the initial inventory configuration. Considering the batch order inventory control strategy with the initial inventory configuration, the continuous-time Markov chain method is used to establish a micro-inverter in the photovoltaic power station. The state model of the inventory level of the photovoltaic power generation system, so as to calculate the expectation of the number of shortages of the micro-inverter photovoltaic power generation system in a given period of time, and then calculate the expected power generation loss during this period of time, so as to evaluate the micro-inverter The output of photovoltaic power plants.

To achieve the above object, the technical scheme adopted in the present invention is:

A method for evaluating the power generation capacity of photovoltaic power plants considering the initial inventory configuration, including:

Step 1. Establish a spare parts balance relationship for the micro-inverter photovoltaic power generation system considering the initial inventory configuration;

Step 2. Use continuous-time Markov chain to describe the inventory level state of the micro-inverter photovoltaic power generation system;

Step 3. Obtain the Markov state transition rate matrix of the micro-inverter photovoltaic power generation system according to the inventory level status, failure rate and delivery rate of the micro-inverter photovoltaic power generation system;

Step 4. Determine the steady-state time of the inventory level state of the micro-inverter photovoltaic power generation system, and express the relationship between the steady-state probability and the transfer rate;

Step 5. Solve the steady-state probability of the inventory level state of the micro-inverter photovoltaic power generation system;

Step 6. Calculate the expected power generation loss of the entire photovoltaic power station according to the obtained steady-state probability of each state;

Step 7: Evaluate the corresponding expected net power generation of the photovoltaic power station according to the expected power generation loss.

Further, the step 1 includes:

Set the installed quantity N of the micro-inverter photovoltaic power generation system, the initial inventory quantity S, the current inventory quantity SL, the inventory shortage quantity BO, the order quantity Q of a batch of orders, and the order point s, and construct the inventory control strategy:

Among them, IP represents the inventory potential, OS represents the number of unfinished orders, Q=S-s, according to the relational expression and ordering strategy, the value range of the inventory potential IP is [s+1,S].

Further, the step 2 includes:

X(t) is the inventory level of the micro-inverter photovoltaic power generation system at time t. When the inventory level X(t) is greater than or equal to 0, it indicates the inventory quantity of spare parts in the warehouse. When the inventory level X(t) is less than 0 , indicating that there are no spare parts in stock in the warehouse, and the faulty parts cannot be replaced, and the demand for spare parts cannot be met, that is, the opposite number of X(t) is equal to the number of inventory shortages, and the number of inventory shortages is equal to the number of faulty parts; the micro-inverter of the photovoltaic power station The state of the photovoltaic power generation system is modeled by a continuous-time Markov chain {X(t), t≥0};

When the inventory shortage quantity is N, the photovoltaic power station stops working, and the state represented by X(t) is {X(t)=S, X(t)=S-1,...,X(t)=0, ...,X(t)=-N} a total of N+S+1 states;

A row vector is used to represent the probability of each state at a certain moment, which is π(t)=[p(X(t)=S), p(X(t)=S-1), p(X(t)=S -2),...,p(X(t)=-N)]; where π(t) represents the state probability row vector of the micro-inverter photovoltaic power generation system at time t; The inventory level of the photovoltaic power generation system at time t; m is used to count, record the value when the inventory level is positive or 0, the value range is m∈[0,S], when X(t)=m, it means The inventory quantity of the micro-inverter photovoltaic power generation system at time t is m; r is used to count and record the value when the inventory level is negative. The value range is r∈[-N,-1]. When X(t )=r, it means that the inventory shortage quantity of the micro-inverter photovoltaic power generation system at time t is -r; p(X(t)=m), m∈[0,S] means the inventory level X(t) at time t ) is equal to m, the state probability that the inventory quantity is m; p(X(t)=r), r∈[-N,-1] means that when the inventory level X(t) at time t is equal to r, the inventory shortage quantity is -r State probability.

Further, the step 3 includes:

Let τ represent the delivery rate of the micro-inverter photovoltaic power station, and the failure interval time of the micro-inverter photovoltaic power generation system obeys the exponential distribution with the parameter λ; construct the Markov state transition rate matrix:

A represents the transition rate matrix of the continuous-time Markov chain; i represents the number of rows in matrix A; j represents the number of columns in matrix A; A[i,j] represents the i-th row and j-th column elements in matrix A; N represents the miniature inverse The installed quantity of the inverter photovoltaic power generation system; S represents the initial inventory quantity; Q represents the order quantity of a batch of orders.

Further, the step 4 includes:

Compute the steady state time from the transition rate matrix of the continuous-time Markov chain:

t _a represents the steady-state time, that is, the state probability of each state tends to a fixed value after a period of time from the start of the photovoltaic power station operation, and this period is the steady-state time; ∈ represents the calculation accuracy, and n represents the transfer of the continuous-time Markov chain is the number of eigenvalues of the rate matrix A; ξ _n represents the nth eigenvalue of the transition rate matrix A of the continuous-time Markov chain; R(ξ _n ) represents the real part of the nth zero-removed eigenvalue of the matrix A;

According to the continuous-time Markov chain state transition matrix established by the installed number of photovoltaic power plants and the inventory control strategy, the probability of each state at steady state satisfies the following equation:

0 _[1×(N+S+1)] = π _[1×(N+s+1)] A _{[(N+s+1)×(N+S+1)]}

In the formula, A represents the transition rate matrix of the continuous-time Markov chain, and π represents the steady-state probability row vector of the micro-inverter photovoltaic power generation system.

Further, the step 5 includes:

According to the relational expression in step 4, the steady-state probability of each state is solved, and the steady-state probability is:

π=[p(X=S), p(X=S-1), p(X=S-2),...,p(X=-N)]

In the formula, π represents the steady-state probability row vector of the micro-inverter photovoltaic power generation system; X represents the inventory level of the micro-inverter photovoltaic power generation system in the steady state; m is used to count and record when the inventory level is positive or 0. Value, the value range is m∈[0,S]. When X=m, it means that the inventory quantity of the micro-inverter photovoltaic power generation system in the steady state is m; r is used for counting, and the recorded inventory level is negative. The value of , the value range is r∈[-N,-1], when X=r, it means that the inventory shortage quantity of the micro-inverter photovoltaic power generation system in the steady state is -r; p(X=m), m∈[0,S] indicates the steady-state probability that the stock quantity is m when the stock level X is equal to m; p(X=r),r∈[-N,-1] indicates that when the stock level X is equal to r, the stock is in short supply Steady-state probabilities of quantity -r.

Further, the step 6 includes:

The expected energy loss E[LE] for a given period of time is calculated as follows:

为微型逆变器光伏发电系统每小时的发电量的平均值，采用微型逆变器光伏发电系统发电功率的额定标称值，或采用电站运行过程中收集数据的统计值；T表示一段给定的时间；X表示微型逆变器光伏发电系统在稳态的库存水平；r用以计数，记录库存水平为负值时的取值，取值范围为r∈-N,-1]，当X＝r时，表示微型逆变器光伏发电系统在稳态的库存短缺数量为-r；p(X＝r),r∈[-N,-1]表示微型逆变器光伏发电系统的库存短缺数量为-r时的稳态概率，由于库存短缺数量等于故障数量，p(X＝r),r∈[-N,-1]也就表示了微型逆变器光伏发电系统的故障数量为-r时的稳态概率；LE表示光伏电站的能量损失；E[LE]表示光伏电站在一段给定时间内的预期能量损失。In the above formula

is the average value of the hourly power generation of the micro-inverter photovoltaic power generation system, using the rated nominal value of the power generated by the micro-inverter photovoltaic power generation system, or the statistical value of the data collected during the operation of the power station; T represents a given period of time time; X represents the inventory level of the micro-inverter photovoltaic power generation system in a steady state; r is used to count, record the value when the inventory level is negative, the value range is r∈-N,-1], when X =r, it means that the inventory shortage quantity of the micro-inverter photovoltaic power generation system in the steady state is -r; p(X=r),r∈[-N,-1] means the inventory shortage of the micro-inverter photovoltaic power generation system The steady-state probability when the quantity is -r, since the quantity of inventory shortage is equal to the number of faults, p(X=r), r∈[-N,-1] also means that the number of faults in the micro-inverter photovoltaic power generation system is - Steady-state probability at r; LE represents the energy loss of the PV plant; E[LE] represents the expected energy loss of the PV plant over a given period of time.

Further, the step 7 includes: according to the expected power generation loss, evaluating the expected net power generation E[EG] of the photovoltaic power station in a corresponding given period of time as follows:

N represents the installed capacity of the micro-inverter photovoltaic power generation system; EG represents the net power generation of the photovoltaic power station; E[EH] represents the expected net power generation of the photovoltaic power station in a given period of time.

The beneficial effects of the present invention are:

The invention proposes a method for evaluating the power generation of a photovoltaic power station considering the initial inventory configuration, including: establishing a spare parts balance relation of the micro-inverter photovoltaic power generation system considering the initial inventory configuration; The inventory level state of the inverter photovoltaic power generation system; and according to the inventory level state, failure rate and delivery rate of the micro inverter photovoltaic power generation system, the Markov state transition rate matrix of the micro inverter photovoltaic power generation system is obtained; The steady-state time of the inventory level state of the inverter photovoltaic power generation system, and the relationship between the steady-state probability and the transfer rate is expressed; the steady-state probability of the inventory level state of the micro-inverter photovoltaic power generation system is solved; according to the obtained According to the steady-state probability of each state, the expected power generation loss of the entire photovoltaic power station is calculated; according to the expected power generation loss, the corresponding expected net power generation amount of the photovoltaic power station is evaluated. The method can determine the inventory level state of the micro-inverter photovoltaic power generation system through the continuous-time Markov chain, so as to predict the expected shortage quantity, and based on this, the expected power generation loss in a given period of time can be calculated, so as to determine a given period of time. The amount of electricity generated by the micro-inverter photovoltaic power station within a certain period of time. The scheme has good applicability and is suitable for all micro-inverter photovoltaic power generation systems and similar products with this feature.

Description of drawings

FIG. 1 is a flowchart of a method for evaluating the power generation of a photovoltaic power station considering initial inventory configuration provided by an embodiment of the present invention;

2 is a schematic diagram of an inventory control strategy provided by an embodiment of the present invention;

FIG. 3 is an inventory level state transition diagram provided by an embodiment of the present invention.

Detailed ways

In order to make the technical means, creative features, achievement goals and effects realized by the present invention easy to understand, the present invention will be further described below with reference to the specific embodiments.

In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end" and "the other end" The orientation or positional relationship indicated by etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, with a specific orientation. The orientation configuration and operation are therefore not to be construed as limitations of the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed to indicate or imply relative importance.

In the description of the present invention, it should be noted that, unless otherwise expressly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense, for example, "connected" may be a fixed connection It can also be a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or the internal communication between the two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

A method for evaluating the power generation of a photovoltaic power station considering initial inventory configuration provided by the present invention includes:

Step 1, establishing a spare parts balance relation of the micro-inverter photovoltaic power generation system considering the initial inventory configuration.

The installed capacity of the micro-inverter photovoltaic power generation system is N. A micro-inverter photovoltaic power generation system is composed of PV panels, micro-inverters and assemblies. The initial inventory quantity of the micro-inverter photovoltaic power generation system is S. When a photovoltaic power generation system in a photovoltaic power station that is working normally fails, if there are spare parts in the warehouse, they will be replaced. The current inventory quantity is SL-1, but when there are no spare parts in the warehouse, it means that there is currently a spare part that is not required. Satisfied, that is, the shortage BO+1. Therefore, in the inventory control strategy, when the current inventory quantity SL decreases to a negative number, it means that there are no spare parts in the warehouse and the absolute value of the inventory quantity SL is the shortage BO. The number is less than the installed capacity N. When the current inventory quantity SL is reduced to a certain threshold, an order needs to be issued to order the micro-inverter photovoltaic power generation system for replacement and maintenance, and the order quantity is Q. In this inventory control strategy, an order point s is established, and when the current inventory quantity SL is reduced to s, an order is issued, and the order quantity is Q=S-s, but after the order is issued, the spare parts cannot be sent to the warehouse immediately, so the spare parts are waiting for In the coming time, since the photovoltaic system is still in operation, the failure during operation will also bring new demand for spare parts. When the current inventory quantity SL decreases to the order condition thresholds s-Q, s-2Q, ..., s-kQ (current When the inventory quantity is negative, it means that there is a shortage of spare parts. At this time, the inventory shortage quantity is BO, and BO is equal to the opposite number of SL), and an order with an order quantity of Q will be issued. Among them, k represents the number of orders, which means the kth spare parts order. An order that is not delivered to the power station is an unfulfilled order, and the number of unfulfilled orders is represented by OS. The relationship between the inventory potential IP and the current inventory quantity SL, the single batch order quantity Q, the number of outstanding orders OS and the inventory shortage quantity BO is:

According to the relational expression and ordering strategy, the value range of the stock potential IP is [s+1,S]. When the inventory shortage quantity, that is, BO is not 0, there is a micro-inverter photovoltaic power generation system that has failed but no spare parts can be replaced, and the number W of the currently working micro-inverter photovoltaic power generation system is less than the installed capacity N.

Through the relationship equation between the inventory potential IP and the current inventory quantity SL, the single batch order quantity Q, the number of outstanding orders OS, and the shortage quantity BO, when the micro-inverter photovoltaic power generation system of the photovoltaic power station fails, when the warehouse When the spare parts inventory quantity SL is positive, use spare parts to replace the faulty parts to ensure the normal operation of the micro-inverter photovoltaic power generation system. When the micro-inverter photovoltaic power generation system of the photovoltaic power station fails, when the spare parts inventory quantity SL in the inventory is 0 or a negative value, there is no spare part to replace, then the number W of the currently working micro-inverter photovoltaic power generation system is reduced, and there is a shortage. The quantity BO is the inverse of the inventory quantity SL at this time. Because the installed capacity is N, when the number W of the currently working micro-inverter photovoltaic power generation systems decreases to 0, the photovoltaic power station stops generating electricity.

In step 2, a continuous-time Markov chain is used to describe the inventory level state of the micro-inverter photovoltaic power generation system.

According to the relationship between the inventory potential IP and the current inventory quantity SL, the single batch order quantity Q, the number of outstanding orders OS and the shortage quantity BO in step 1, the system can be described through multiple states. When the inventory quantity SL is a positive number or 0, the shortage BO is 0, and the status of the micro-inverter photovoltaic power generation system includes various stocks ranging from the initial inventory quantity S of the micro-inverter photovoltaic power generation system to the inventory quantity of 0. Quantity status; when the current inventory quantity SL is negative, and the shortage BO is the opposite number, since the number W of the currently working micro-inverter photovoltaic power generation system decreases to 0, the photovoltaic power station stops generating work, so the micro-inverter The state of the photovoltaic power generation system includes a variety of shortage states from the shortage BO of 1 to the reduction of W to 0 (that is, the shortage BO is equal to the installed capacity N). Therefore, for this system, a continuous-time Markov chain is used to describe the inventory level state of the micro-inverter photovoltaic power generation system.

X(t) is the inventory level of the micro-inverter photovoltaic power generation system at time t. When the inventory level X(t) is greater than or equal to 0, it indicates the inventory quantity of spare parts in the warehouse. When the inventory level X(t) is less than 0 , indicating that there are no spare parts in stock in the warehouse, and the faulty parts cannot be replaced, and the demand for spare parts cannot be met, that is, the opposite number of X(t) is equal to the number of inventory shortages, and the number of inventory shortages is equal to the number of faulty parts; the micro-inverter of the photovoltaic power station The state of the photovoltaic power generation system is modeled by a continuous-time Markov chain {X(t), t≥0}. When the inventory is in short supply, the failure of the micro-inverter photovoltaic power generation system cannot be replaced and repaired in time. The current working micro When the number W of inverter photovoltaic power generation systems is reduced to 0 (that is, the shortage BO is equal to the installed capacity N), the photovoltaic power station stops working, so the state represented by X(t) is {X(t)=S, X(t) )=S-1,...,X(t)=0,...,X(t)=-N} a total of N+S+1 states. Next, the continuous-time marathon is carried out with the inventory level state. Koff chain modeling.

A row vector is used to represent the probability of each state at a certain moment, which is π(t)=[p(X(t)=S), p(X(t)=S-1), p(X(t)=S -2),...,p(X(t)=-N)]; where π(t) represents the state probability row vector of the micro-inverter photovoltaic power generation system at time t; The inventory level of the photovoltaic power generation system at time t; m is used to count, record the value when the inventory level is positive or 0, the value range is m∈[0,S], when X(t)=m, it means The inventory quantity of the micro-inverter photovoltaic power generation system at time t is m; r is used to count and record the value when the inventory level is negative. The value range is r∈[-N,-1]. When X(t )=r, it means that the inventory shortage quantity of the micro-inverter photovoltaic power generation system at time t is -r; p(X(t)=m), m∈[0,S] means the inventory level X(t) at time t ) is equal to m, the state probability that the inventory quantity is m; p(X(t)=r), r∈[-N,-1] means that when the inventory level X(t) at time t is equal to r, the inventory shortage quantity is -r State probability.

Step 3, according to the inventory level state, failure rate and delivery rate of the micro-inverter photovoltaic power generation system, a Markov state transition rate matrix of the micro-inverter photovoltaic power generation system is obtained.

After the warehouse issues a replenishment stock order, the order is completed from the time the order is issued to the delivery of the order, and the order delivery time obeys an exponential distribution with a parameter of τ, which is also called the delivery rate. The time between failures of the micro-inverter photovoltaic power generation system obeys an exponential distribution with parameter λ. According to the above conditions, the inventory level state of the micro-inverter photovoltaic power generation system can be modeled using the continuous-time Markov chain under the condition of considering the inventory control strategy of this type of photovoltaic power station. A schematic diagram of this inventory control strategy is shown in Figure 2.

As shown in Figure 3, according to the inventory control strategy, the inventory level of the micro-inverter photovoltaic power generation system represented by each state, the failure rate and the delivery rate, a continuous-time Markov chain is established. Calculate the state transition rate matrix. According to the conditions between different rows and columns of the matrix, the calculation expression of the transition rate is as follows:

This expression represents the law of the value of elements in the transition rate matrix, A represents the transition rate matrix of the continuous-time Markov chain; i represents the number of rows in matrix A; j represents the number of columns in matrix A; A[i,j] represents The elements in the i-th row and the j-th column in matrix A; N represents the installed quantity of the micro-inverter photovoltaic power generation system; S represents the initial inventory quantity; Q represents the order quantity of a batch of orders.

Step 4, determine the steady-state time of the inventory level state of the micro-inverter photovoltaic power generation system, and express the relationship between the steady-state probability and the transfer rate.

Compute the steady state time from the transition rate matrix of the continuous-time Markov chain:

t _a represents the steady-state time, that is, the state probability of each state tends to a fixed value after a period of time since the photovoltaic power station starts to work, and this period is the steady-state time; ∈ represents the calculation accuracy; n represents the transition of the continuous-time Markov chain is the number of eigenvalues of the rate matrix A; ξ _n represents the nth eigenvalue of the transition rate matrix A of the continuous-time Markov chain; R(ξ _n ) represents the real part of the nth zero-removed eigenvalue of the matrix A;

According to the continuous-time Markov chain and state transition matrix established by the scale of the power station and the inventory control strategy, the probability of each state at steady state satisfies the following equation:

0 _[1×(N+S+1)] = π _[1×(N+S+1)] A _{[(N+S+1)×(N+S+1)]}

In the formula, A is the state transition rate matrix, and π represents the steady-state probability row vector of the micro-inverter photovoltaic power generation system.

In addition, the steady-state probability of each state also satisfies the relationship:

m is used to count and record the value when the inventory level is positive or 0. The value range is m∈[0,S]. When X=m, it represents the inventory quantity of the micro-inverter photovoltaic power generation system in the steady state is m; r is used to count, record the value when the inventory level is negative, the value range is r∈[-N,-1], when X=r, it means that the micro-inverter photovoltaic power generation system is in a steady state The inventory shortage quantity is -r; p(X=m), m∈[0,S] represents the steady-state probability that the inventory quantity is m when the inventory level X is equal to m; p(X=r),r∈[- N,-1] represents the steady-state probability that the inventory shortage quantity is -r when the inventory level X is equal to r.

Step 5, solve the steady state probability of the inventory level state of the micro-inverter photovoltaic power generation system.

According to the relationship in step 4, solve the probability of each state when t tends to positive infinity, that is, the steady-state probability:

π=[p(X=S), p(X=S-1), p(X=S-2),...,p(X=-N)]

In the formula, π represents the steady-state probability row vector of the micro-inverter photovoltaic power generation system; X represents the inventory level of the micro-inverter photovoltaic power generation system in the steady state; m is used to count and record when the inventory level is positive or 0. Value, the value range is m∈[0,S]. When X=m, it means that the inventory quantity of the micro-inverter photovoltaic power generation system in the steady state is m; r is used for counting, and the recorded inventory level is negative. The value of , the value range is r∈[-N,-1], when X=r, it means that the inventory shortage quantity of the micro-inverter photovoltaic power generation system in the steady state is -r; p(X=m), m∈[0,S] indicates the steady-state probability that the stock quantity is m when the stock level X is equal to m; p(X=r),r∈[-N,-1] indicates that when the stock level X is equal to r, the stock is in short supply Steady-state probabilities of quantity -r.

Step 6: Calculate the expected power generation loss of the entire photovoltaic power station according to the obtained steady-state probability of each state. The expected power generation loss needs to be calculated from the average power generation per hour of each micro-inverter photovoltaic power generation system. Rated nominal values are obtained.

In order to evaluate the energy production, in the present invention, the hourly power generation amount of the micro-inverter photovoltaic power generation system proposed by the "photovoltaic hourly power generation model" is used to estimate the expected energy loss, and the expected energy loss E[LE ]as follows:

为微型逆变器光伏发电系统每小时的发电量的平均值，可以采用微型逆变器光伏发电系统发电功率的额定标称值，也可以采用电站运行过程中收集数据的统计值；T表示一段给定的时间；X表示微型逆变器光伏发电系统在稳态的库存水平；r用以计数，记录库存水平为负值时的取值，取值范围为r∈[-N,-1]，当X＝r时，表示微型逆变器光伏发电系统在稳态的库存短缺数量为-r；p(X＝r),r∈[-N,-1]表示微型逆变器光伏发电系统的库存短缺数量为-r时的稳态概率，由于库存短缺数量等于故障数量，p(X＝r),r∈[-N,-1]也就表示了微型逆变器光伏发电系统的故障数量为-r时的稳态概率；LE表示光伏电站的能量损失；E[LE]表示光伏电站在一段给定时间内的预期能量损失。In the above formula

is the average value of the hourly power generation of the micro-inverter photovoltaic power generation system, which can be the rated nominal value of the power generated by the micro-inverter photovoltaic power generation system, or the statistical value of the data collected during the operation of the power station; T represents a period of time A given time; X represents the inventory level of the micro-inverter photovoltaic power generation system in a steady state; r is used to count, record the value when the inventory level is negative, and the value range is r∈[-N,-1] , when X=r, it means that the inventory shortage quantity of the micro-inverter photovoltaic power generation system in the steady state is -r; p(X=r),r∈[-N,-1] means that the micro-inverter photovoltaic power generation system The steady-state probability when the inventory shortage quantity is -r, since the inventory shortage quantity is equal to the number of failures, p(X=r),r∈[-N,-1] also represents the failure of the micro-inverter photovoltaic power generation system The steady-state probability when the quantity is -r; LE represents the energy loss of the PV plant; E[LE] represents the expected energy loss of the PV plant over a given period of time.

Step 7: Evaluate the corresponding expected net power generation of the photovoltaic power station according to the expected power generation loss.

According to the expected power generation loss E[LE] of the micro-inverter photovoltaic power generation system in a given period of time obtained in step 6, the expected net power generation amount E[EG] in a given period of time is finally obtained as follows:

N represents the installed capacity of the micro-inverter photovoltaic power generation system; EG represents the net power generation of the photovoltaic power station; E[EG] represents the expected net power generation of the photovoltaic power station in a given period of time.

The specific embodiments of the present invention will be further described in detail below with reference to examples.

Step 1, establishing a spare parts balance relation of the micro-inverter photovoltaic power generation system considering the initial inventory configuration.

It is known that the installed capacity of a photovoltaic power station is N=3000, and the initial inventory quantity is S=300. When the inventory quantity is reduced to s=100, a batch of orders for Q=200 replacement parts will be sent. When the inventory quantity decreases from 100 When the multiple of 200 is reduced (when the inventory quantity is negative, it means out of stock), a batch of orders is sent. From this, it can be seen that the stock potential range is [101,300].

In step 2, a continuous-time Markov chain is used to describe the inventory level state of the micro-inverter photovoltaic power generation system.

X(t) represents the inventory level of the micro-inverter photovoltaic power generation system, and the number W of the currently working micro-inverter photovoltaic power generation system ranges from W∈[0,3000]; when W=0, this The power station stops working, so the state represented by X(t) is {X(t)=300, X(t)=299, X(t)=298,...,X(t)=-3000} a total of 3301 a state.

A row vector is used to represent the probability of each state at time t, which is π(t)=[p(X(t)=300), p(X(t)=299), p(X(t)=298),… ,p(X(t)=-3000]).

Step 3, according to the inventory level state, failure rate and delivery rate of the micro-inverter photovoltaic power generation system, a Markov state transition rate matrix of the micro-inverter photovoltaic power generation system is obtained.

The failure rate of the micro-inverter photovoltaic power generation system of this power station is λ=1×10 ^-5 h ^-1 , the delivery time obeys the exponential distribution of τ=1×10 ^-3 h ^-1 , and h represents hours. The state transition matrix looks like this:

Step 4, determine the steady-state time of the inventory level state of the micro-inverter photovoltaic power generation system, and express the relationship between the steady-state probability and the transfer rate.

Given the calculation accuracy ∈=10 ^-4 , solve the transition rate matrix of the continuous-time Markov chain and calculate the steady-state time:

That is, in the initial state (when the micro-inverter photovoltaic power generation system is completely intact), it enters a stable state after 237.9922 hours.

The steady state probability of each state satisfies the relation:

0 _[1×(3301)] = π _[1×(3301)] A _{[(3301)×(3301)]}

Step 5, solve the steady state probability of the inventory level state of the micro-inverter photovoltaic power generation system.

The steady state probability is:

π=[p(X=300), p(X=299), p(X=298),...,p(X=-3000)]

Step 6: Calculate the expected power generation loss of the entire photovoltaic power station according to the obtained steady-state probability of each state.

Since the steady-state probability has been found, the relation can be used:

为一段给定时间内的微型逆变器光伏发电系统每小时的发电量的平均值，给定为

T为一段给定的时间，给定为8760小时，p为微型逆变器光伏发电系统的状态的稳态概率，X表示微型逆变器光伏发电系统在稳态时的库存水平状态，p(X＝r),r∈[-3000,-1]表示微型逆变器光伏发电系统的库存短缺数量为r时的稳态概率。带入上式得：E[LE]＝1.5742×10⁵kW·h。Find the expected power generation losses for the entire PV plant over a given period of time, where

is the average hourly power generation of the micro-inverter photovoltaic power generation system for a given period of time, given as

T is a given period of time, given as 8760 hours, p is the steady-state probability of the state of the micro-inverter photovoltaic power generation system, X is the inventory level state of the micro-inverter photovoltaic power generation system in the steady state, p( X=r), r∈[-3000,-1] represents the steady-state probability when the inventory shortage quantity of the micro-inverter photovoltaic power generation system is r. Bring in the above formula to get: E[LE]=1.5742×10 ⁵ kW·h.

Step 7: Evaluate the corresponding expected net power generation of the photovoltaic power station according to the expected power generation loss.

和一段给定时间内的预期发电损失E[LE]，最后求出一段给定时间内的预期净发电量E[EG]如下：E[EG]＝2.9674×10⁹kW·h。kW·h表示千瓦时，能量单位。According to the average value of the hourly power generation of the micro-inverter photovoltaic power generation system obtained in step 6

And the expected power generation loss E[LE] in a given period of time, and finally the expected net power generation amount E[EG] in a given period of time is obtained as follows: E[EG]=2.9674×10 ⁹ kW·h. kW·h means kilowatt-hour, a unit of energy.

A method for evaluating the power generation capacity of a photovoltaic power station considering an initial inventory configuration provided by an embodiment of the present invention includes: establishing a spare parts balance relation of a micro-inverter photovoltaic power generation system considering the initial inventory configuration; adopting a continuous-time Markov chain to Describe the inventory level state of the micro-inverter photovoltaic power generation system; and obtain the Markov state transition rate matrix of the micro-inverter photovoltaic power generation system according to the inventory level state, failure rate and delivery rate of the micro-inverter photovoltaic power generation system; Determine the steady-state time of the inventory level state of the micro-inverter photovoltaic power generation system, and express the relationship between the steady-state probability and the transfer rate; solve the steady-state probability of the inventory level state of the micro-inverter photovoltaic power generation system; According to the obtained steady-state probability of each state, the expected power generation loss of the entire photovoltaic power station is calculated; according to the expected power generation loss, the corresponding expected net power generation of the photovoltaic power station is evaluated. The scheme has good applicability and is suitable for all micro-inverter photovoltaic power generation systems and similar products with this feature.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (8)

1. A method for evaluating the power generation capacity of a photovoltaic power station by considering initial inventory configuration is characterized by comprising the following steps:

step 1, establishing a spare part balance relational expression of a photovoltaic power generation system of a micro inverter considering initial inventory configuration;

step 2, describing the stock level state of the photovoltaic power generation system of the micro inverter by adopting a continuous time Markov chain;

step 3, solving a Markov state transition rate matrix of the photovoltaic power generation system of the micro inverter according to the stock level state, the fault rate and the delivery rate of the photovoltaic power generation system of the micro inverter;

step 4, determining the steady state time of the inventory level state of the photovoltaic power generation system of the micro inverter, and expressing the relation between the steady state probability and the transfer rate;

step 5, solving the steady state probability of the inventory level state of the photovoltaic power generation system of the micro inverter;

step 6, calculating the expected power generation loss of the whole photovoltaic power station according to the obtained steady-state probabilities of the states;

and 7, evaluating the corresponding expected net power generation amount of the photovoltaic power station according to the expected power generation loss.

2. The method of claim 1, wherein step 1 comprises:

setting the installed quantity N, the initial inventory quantity S, the current inventory quantity SL, the inventory shortage quantity BO, a batch of order quantity Q and an order point S of the photovoltaic power generation system of the micro inverter, and constructing an inventory control strategy:

wherein, IP represents stock position potential, OS represents unfinished order number, Q is S-S, and the value range of the stock position potential IP is [ S +1, S ] according to the relational expression and the ordering strategy.

3. The method of claim 2, wherein step 2 comprises:

x (t) is the stock level of the micro-inverter photovoltaic power generation system at time t, when the stock level x (t) is greater than or equal to 0, the stock quantity of spare parts stored in the warehouse is represented, and when the stock level x (t) is less than 0, the stock quantity of spare parts in the warehouse is represented, the spare parts cannot be replaced and the requirement of the spare parts cannot be met, namely the opposite number of x (t) is equal to the stock shortage quantity, and the stock shortage quantity is equal to the quantity of the fault parts; the state of a photovoltaic power generation system of a micro inverter of a photovoltaic power station is modeled by adopting a continuous time Markov chain { X (t) > 0 };

when the stock shortage quantity is N, the photovoltaic power station stops working, and the states characterized by X (t) are { X (t) ═ S, X (t) ═ S-1., X (t) · 0., X (t) ═ N } total N + S +1 states;

a row vector is used to represent the probability of each state at a certain time, which is pi (t) ═ p (x (t) ═ S), p (x (t) ═ S-1), p (x (t) ═ S-2., p (x (t) ═ N) ]; wherein pi (t) represents a state probability row vector of the photovoltaic power generation system of the micro inverter at the time t; x (t) represents the inventory level of the microinverter photovoltaic power generation system at time t; m is used for counting, recording the value when the stock level is a positive value or 0, wherein the value range is m belongs to [0, S ], and when X (t) is m, the stock number of the photovoltaic power generation system of the micro inverter at the time t is m; r is used for counting, recording the value when the stock level is a negative value, wherein the value range is r belongs to [ -N, -1], and when X (t) is r, the stock shortage quantity of the photovoltaic power generation system of the micro inverter at the time t is represented as-r; p (x (t) ═ m), where m ∈ [0, S ] denotes a state probability that the stock quantity is m when the stock level x (t) is equal to m at time t; p (x (t) ═ r), r ∈ [ -N, -1] denotes the state probability that the stock shortage number is-r at time t when stock level x (t) equals r.

4. The method of claim 3, wherein step 3 comprises:

let tau represent delivery rate of photovoltaic power station of the micro inverter, the time obeys the exponential distribution of parameter lambda of the fault interval of the photovoltaic power generation system of the said micro inverter; constructing a Markov state transition rate matrix:

a represents a transition rate matrix of a continuous-time Markov chain; i represents the number of rows of the matrix A; j represents the number of columns of matrix A; a [ i, j ] represents the ith row and jth column element in the matrix A; n represents the installed number of the photovoltaic power generation systems of the micro inverters; s represents the initial inventory quantity; q represents the batch order quantity.

5. The method of claim 4, wherein the step 4 comprises:

calculating the steady state time from the transition rate matrix of the continuous time Markov chain:

t_aindicating steady state time, i.e. the time elapsed for the photovoltaic plant to operate from the startThe state probability of each later state tends to a fixed value, and the period of time is steady-state time; e represents the calculation precision; n represents the number of eigenvalues of the transfer rate matrix A of the continuous-time Markov chain; xi_nAn nth eigenvalue of a transition rate matrix A representing a continuous time Markov chain; r (xi)_n) Representing the real part of the nth de-0 eigenvalue of the matrix A;

according to a continuous time Markov chain state transition matrix established by the installed quantity of the photovoltaic power station and the inventory control strategy, each state probability in a steady state satisfies the following equation:

0_[1×(N+S+1)]＝π_[1×(N+S+1)]A_{[(N+S+1)×(N+S+1)]}

in the formula, A represents a transfer rate matrix of a continuous time Markov chain, and pi represents a steady-state probability row vector of the micro-inverter photovoltaic power generation system.

6. The method of claim 5, wherein the step 5 comprises:

and (4) solving the steady-state probability of each state according to the relation in the step 4, wherein the steady-state probability is as follows:

π＝[p(X＝S)，p(X＝S-1)，p(X＝S-2)，...，p(X＝-N)]

in the formula, pi represents a steady-state probability row vector of the photovoltaic power generation system of the micro inverter; x represents the inventory level of the micro-inverter photovoltaic power generation system in a steady state; m is used for counting, recording the value when the stock level is a positive value or 0, wherein the value range is m belongs to [0, S ], and when X is m, the stock number of the photovoltaic power generation system of the micro inverter in a stable state is m; r is used for counting, recording the value when the stock level is a negative value, wherein the value range is r ∈ [ -N, -1], and when X is r, the number of stock shortages of the photovoltaic power generation system of the micro inverter in a steady state is-r; p (X is m), m belongs to [0, S ] represents the steady-state probability that the stock quantity is m when the stock level X is equal to m; p (X ═ r), r ∈ [ -N, -1] represents the steady state probability that the inventory shortage quantity is-r when inventory level X equals r.

7. The method of claim 6, wherein the step 6 comprises:

the expected energy loss E [ LE ] over a given period of time is calculated as follows:

in the above formula

The average value of the hourly generated energy of the photovoltaic power generation system of the micro inverter is the rated nominal value of the generated power of the photovoltaic power generation system of the micro inverter, or the statistical value of the collected data in the running process of the power station is adopted; t represents a given period of time; x represents the inventory level of the micro-inverter photovoltaic power generation system in a steady state; r is used for counting, and recording the value when the stock level is a negative value, wherein the value range is r belongs to [ -N, -1]When the X is equal to r, the inventory shortage quantity of the micro inverter photovoltaic power generation system in a steady state is represented as-r; p (X ═ r), r ∈ [ -N, -1]Representing the steady-state probability of the micro-inverter photovoltaic power generation system when the inventory shortage number is-r, since the inventory shortage number is equal to the fault number, p (X-r), r e [ -N, -1]The steady-state probability when the fault number of the photovoltaic power generation system of the micro inverter is-r is represented; LE represents the energy loss of the photovoltaic plant; e [ LE ]]Representing the expected energy loss of the photovoltaic plant over a given period of time.

8. The method of claim 7, wherein the step 7 comprises: from said expected power loss, evaluating the expected net power generation E [ EG ] of the photovoltaic plant for a corresponding given period of time as follows:

n represents the installed number of the photovoltaic power generation systems of the micro inverters; EG represents the net power generation capacity of the photovoltaic power plant; e [ EG ] represents the expected net power generation of the photovoltaic power plant over a corresponding given period of time.

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