Optimization method of distribution network distributed photovoltaic output considering photovoltaic inverter life

Abstract

The application discloses a distributed photovoltaic output optimization method of a power distribution network considering photovoltaic inverter service life, and can realize distributed photovoltaic power output optimization of the power distribution network while considering IGBT service life in the photovoltaic inverter.

Description

Technical Field

[0001] This invention belongs to the field of distributed power generation output optimization technology in distribution networks, and specifically relates to a method for optimizing distributed photovoltaic power generation in distribution networks that takes into account the lifespan of photovoltaic inverters. Background Technology

[0002] The distribution network is a core component of the power system, serving as the link between the transmission system and end users. In recent years, with the introduction of the "dual-carbon" target, a high proportion of distributed power sources (photovoltaics, wind turbines, etc.) have been integrated into the distribution network. When a high proportion of photovoltaic power is integrated into the distribution network, the network's capacity to absorb new energy sources can be improved. However, the integration of distributed photovoltaic power into the distribution network alters the traditional single-source radial power system structure, potentially causing bidirectional power flow. Simultaneously, photovoltaic power generation exhibits volatility and randomness, which may lead to voltage exceeding upper limits at certain nodes in the distribution network, thereby reducing the reliability and security of the distribution network operation. To address this issue, the non-functionality of distributed photovoltaic power can be used to quickly respond to the volatility of new energy power output and maintain stable node voltages.

[0003] Reactive power output from distributed photovoltaic (PV) systems impacts power flow, network losses, and power quality in the distribution network. Therefore, optimizing distributed PV output is crucial to meet the operational demands of the distribution network. Currently, reactive power optimization technology is a vital component of active distribution network operation optimization. It primarily aims to reduce network losses and improve power quality, using reactive power output as the decision variable and power flow and voltage limits as constraints. Optimization algorithms are used to find the optimal reactive power output that satisfies the operating conditions of the distribution network system. However, current distributed PV reactive power optimization fails to consider the impact of reactive power output from distributed PV inverters on the lifespan of the IGBTs within them. When the inverter outputs reactive power, the current flowing through the IGBTs increases, leading to more severe fluctuations in IGBT junction temperature and ultimately affecting IGBT lifespan.

[0004] To address the existing problems, this invention proposes a distributed photovoltaic (PV) output optimization method for distribution networks that considers the lifespan of PV inverters. A multi-objective optimization model is established, which considers distribution network losses, active power reduction of PV power generation systems, and minimizing the maximum junction temperature of IGBTs. This allows for the consideration of the impact of reactive power output on the operating lifespan of IGBTs in PV inverters when optimizing reactive power in distributed PV systems. Summary of the Invention

[0005] The purpose of this invention is to propose a method for optimizing distributed photovoltaic (PV) output in distribution networks that considers the lifespan of PV inverters. This method mainly includes the following steps:

[0006] S1. Determine the IGBT model in the photovoltaic inverter of the distribution network;

[0007] S2. Establish a model for calculating the maximum power of a photovoltaic array;

[0008] S3. Establish an IGBT thermoelectric coupling model;

[0009] S4. Set the ambient temperature to [-5 0 5 10 15 20 25 30 35 40]℃ and the photovoltaic inverter input power to [0 1 2 3 4 5 6 7 8 9 10 11]kW respectively, and obtain the maximum junction temperature curve of IGBT;

[0010] S5. Perform quadratic polynomial fitting based on the maximum junction temperature curve of the IGBT;

[0011] S6. Extract task profile data of light intensity and ambient temperature, distribution network topology, line parameters, and load data of each node in the distribution network;

[0012] S7. Establish a multi-objective optimization model that minimizes distribution network losses, active power reduction, and the maximum junction temperature of IGBTs;

[0013] S8. Convert the multi-objective optimization model established in step 7 into a second-order cone programming model, so that the optimization problem is transformed from a non-convex optimization problem into a convex optimization problem;

[0014] S9. Use the particle swarm optimization algorithm to solve the convex optimization model in S8 to obtain the optimal reactive power output of the distributed power source in the distribution network considering the IGBT lifetime in the photovoltaic inverter.

[0015] This invention proposes a method for optimizing distributed photovoltaic output in distribution networks that takes into account the lifespan of photovoltaic inverters. It determines the IGBT model in the photovoltaic inverters of the distribution network, and the corresponding IGBT datasheet can be consulted based on the IGBT model to obtain the relevant IGBT parameters.

[0016] This invention proposes a method for optimizing distributed photovoltaic (PV) output in distribution networks, considering the lifespan of PV inverters. The PV array maximum power calculation model first utilizes a PV power generation engineering calculation model to obtain the PV array output characteristics. Secondly, considering the long simulation time, a numerical calculation method for the PV array maximum output power based on a short-step traversal search is proposed to calculate the maximum output power of the PV array under a one-year task profile in a short time. Without considering local shading, the PV array output PU characteristic has a strictly concave function property, meaning there is only one global maximum power point. Therefore, this maximum power point can be obtained through a traversal search. During the traversal search, the initial voltage of the PV array output is set to 0, and the iteration step size is 0.01V. Therefore, the feasible region of the PV array output voltage is...

[0017] Upv ∈{0,0.01,0.02,…U mpp …,U oc}

[0018] Using the photovoltaic power generation engineering calculation model, the feasible region of the photovoltaic array output power can be obtained as follows:

[0019] P pv ∈{P1,P2,P3,…P mpp …,P n}

[0020] This invention proposes a method for optimizing distributed photovoltaic (PV) output in distribution networks that considers the lifespan of PV inverters, and establishes an IGBT thermoelectric coupling model, in which IGBT electrical losses are divided into switching losses and conduction losses.

[0021]

[0022]

[0023]

[0024] in, δ(t) represents the IGBT conduction loss; δ(t) represents the duty cycle; i a T is the inverter output current; j_T V is the junction temperature of the IGBT; CE_25℃ This refers to the rated on-state voltage drop of the IGBT at 25°C; r CE_25℃ K is the rated on-state resistance of the IGBT at 25°C. V_T K is the temperature influence coefficient of the IGBT on-state voltage drop. r_T f is the temperature effect coefficient of the IGBT on-state resistance; sw For the IGBT module's turn-on and turn-off frequencies; K sw K1(V) is the temperature influence coefficient of IGBT switching losses. dc K2(R) represents the voltage coefficient that influences the grid-connected DC voltage of photovoltaic systems on the power loss of IGBT switches; g ) is the gate resistance R g The resistivity that affects the power loss of IGBT switches;

[0025]

[0026] Among them, T j T represents the junction temperature of the IGBT. a Ambient temperature; This represents the electrical losses of the IGBT and the anti-parallel diode.

[0027] The present invention provides a method for optimizing distributed photovoltaic output in power distribution networks that considers the lifespan of photovoltaic inverters. The method is characterized by setting the ambient temperature to [-5 0 5 10 15 20 25 30 35 40]℃ and the input power of the photovoltaic inverter to [0 12 3 4 5 6 7 8 9 10 11]kW, thereby obtaining the IGBT junction temperature curves under the corresponding ambient temperatures.

[0028] This invention proposes a method for optimizing distributed photovoltaic (PV) output in distribution networks that considers the lifespan of PV inverters. Based on the maximum junction temperature curve of IGBTs, a quadratic polynomial fitting is performed.

[0029]

[0030] Among them, T IGBT_max denoted as the maximum junction temperature of the IGBT, p is the input power of the photovoltaic inverter, and a, b, and c are fitting coefficients.

[0031] This invention proposes a method for optimizing distributed photovoltaic output in distribution networks that takes into account the lifespan of photovoltaic inverters. It extracts task profile data of irradiance and ambient temperature in the distribution network, distribution network topology, line parameters, and load data of each node in the distribution network.

[0032] This invention presents a method for optimizing distributed photovoltaic (PV) output in distribution networks that considers the lifespan of PV inverters. It establishes a multi-objective optimization model that minimizes distribution network losses, active power reduction, and the maximum junction temperature of IGBTs.

[0033] Objective function:

[0034] minω1P net,loss +ω2P curt,loss +ω3T IGBT_max

[0035]

[0036]

[0037] Constraints:

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] Among them, P net,loss For distribution network line losses; P curt,loss For photovoltaic active power reduction; T IGBT_max P represents the maximum junction temperature of the IGBT; j, k, and l are the bus indices of the distribution network; J(k) and L(k) are the parent node and child node, respectively; P jk,t Q jk,t r jk,t x jk,t with I jk,t Let be the active power, reactive power, line resistance, line inductance, and line current from bus j to bus k at time t, respectively. V k,t The active power of the photovoltaic system at bus k, the reactive power of the photovoltaic inverter, the active load, the reactive load, and the bus voltage are respectively at time t. V represents the upper limit of the line current between bus j and bus k; min V max These are the upper and lower limits of the distribution network voltage. Let K be the photovoltaic capacity connected at busbar k.

[0048] This invention proposes a method for optimizing distributed photovoltaic (PV) output in distribution networks that considers the lifespan of PV inverters. It transforms the established multi-objective optimization model into a second-order cone programming model, thus changing the optimization problem from non-convex to convex.

[0049] Introduce two variables i jk,t v k,t

[0050]

[0051]

[0052] The established multi-objective optimization model is converted into a second-order cone programming model, with the objective function and constraints as follows:

[0053] objective function

[0054] minω1P net,loss +ω2P curt,loss +ω3T IGBT_max

[0055]

[0056]

[0057] Constraints

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] Among them, P net,loss For distribution network line losses; P curt,loss For photovoltaic active power reduction; T IGBT_max P represents the maximum junction temperature of the IGBT; j, k, and l are the bus indices of the distribution network; J(k) and L(k) are the parent node and child node, respectively; P jk,t Q jk,t r jk,t x jk,t with i jk,t Let be the active power, reactive power, line resistance, line inductance, and square of the line current from bus j to bus k at time t. v k,t Let t represent the active power of the photovoltaic system at bus k, the reactive power of the photovoltaic inverter, the active load, the reactive load, and the square of the bus voltage, respectively. V represents the upper limit of the line current between bus j and bus k; min V max These are the upper and lower limits of the distribution network voltage. Let K be the photovoltaic capacity connected at busbar k.

[0067] This invention proposes a method for optimizing distributed photovoltaic power output in distribution networks that considers the lifespan of photovoltaic inverters. The method uses particle swarm optimization to solve the convex optimization model in S8, and obtains the optimal reactive power output of distributed power sources in distribution networks that takes into account the lifespan of IGBTs in photovoltaic inverters.

[0068] The proposed optimization method for distributed photovoltaic power generation output in distribution networks that considers the lifespan of IGBTs in photovoltaic inverters is a widely applicable optimization method that can optimize the output of distributed power generation in distribution network systems at different locations. Attached Figure Description

[0069] Figure 1IGBT thermoelectric coupling model

[0070] Figure 2 IGBT maximum junction temperature curve

[0071] Figure 3 Light intensity

[0072] Figure 4 Ambient temperature

[0073] Figure 5 Distribution network topology

[0074] Figure 6 IGBT maximum junction temperature suppression effect Detailed Implementation

[0075] 1. Determine the IGBT model in the photovoltaic inverter of the distribution network. In this paper, the IGBT model selected is FS25R12W1T4_B11.

[0076] 2. Establish an engineering calculation model for the maximum power of the photovoltaic array.

[0077] 3. Establish an IGBT thermoelectric coupling model, as shown in the figure below. Figure 1 As shown in the figure, the relevant parameters are shown in the table.

[0078] 4. Set the ambient temperature to [-5 0 5 10 15 20 25 30 35 40]℃ and the photovoltaic inverter input power to [0 1 2 3 4 5 6 7 8 9 10 11]kW respectively, and obtain the maximum junction temperature curve of the IGBT, as shown below. Figure 2 As shown;

[0079] 5. Perform quadratic polynomial fitting based on the maximum junction temperature curve of the IGBT;

[0080]

[0081] 6. Extract task profile data of light intensity and ambient temperature, distribution network topology, line parameters, and load data of each node in the distribution network. Light intensity, ambient temperature, and distribution network topology data are as follows: Figure 3 , 4 As shown in Figure 5;

[0082] 7. Establish a multi-objective optimization model that minimizes distribution network losses, active power reduction, and the maximum junction temperature of IGBTs;

[0083] 8. Convert the multi-objective optimization model established in step 7 into a second-order cone programming model, so that the optimization problem is transformed from a non-convex optimization problem into a convex optimization problem;

[0084] 9. Using the particle swarm optimization algorithm to solve the convex optimization model in S8, the optimal reactive power output of the distributed generation in the distribution network considering the IGBT lifetime in the photovoltaic inverter is obtained, and the maximum junction temperature suppression effect of the IGBT is as follows: Figure 6 As shown.

[0085] As described above, the present invention has been explained in detail. Obviously, any modifications that do not substantially depart from the inventive point and effect of the present invention and are obvious to those skilled in the art are also included within the protection scope of the present invention.

Claims

1. A method for optimizing distributed photovoltaic output in a distribution network considering the lifespan of photovoltaic inverters, characterized in that, This method mainly includes the following steps: S1. Determine the IGBT model in the photovoltaic inverter of the distribution network; S2. Establish an engineering calculation model for the maximum power of the photovoltaic array; S3. Establish an IGBT thermoelectric coupling model; S4. Set the ambient temperature to [-5 0 5 10 15 20 25 30 35 40]℃ and the photovoltaic inverter input power to [0 12 3 4 5 6 7 8 9 10 11]kW respectively, and obtain the maximum junction temperature curve of IGBT; S5. Perform quadratic polynomial fitting based on the maximum junction temperature curve of the IGBT; S6. Extract task profile data of light intensity and ambient temperature in the distribution network, distribution network topology, line parameters and load data of each node in the distribution network; S7. Establish a multi-objective optimization model with the objectives of minimizing distribution network losses, active power reduction, and maximum junction temperature of IGBTs. S8. Convert the multi-objective optimization model established in step 7 into a second-order cone programming model, so that the optimization problem is transformed from a non-convex optimization problem into a convex optimization problem; S9. Use the particle swarm optimization algorithm to solve the convex optimization model in S8 to obtain the optimal reactive power output of the distributed power source in the distribution network considering the IGBT lifetime in the photovoltaic inverter.

2. The method for optimizing distributed photovoltaic output in a distribution network considering the lifespan of photovoltaic inverters according to claim 1, characterized in that, Determine the IGBT model in the photovoltaic inverter of the distribution network. Based on the IGBT model, you can look up the corresponding IGBT datasheet to obtain the relevant IGBT parameters.

3. The method for optimizing distributed photovoltaic output in a distribution network considering the lifespan of photovoltaic inverters according to claim 1, characterized in that, The photovoltaic array maximum power calculation model first uses the photovoltaic power generation engineering calculation model to obtain the output characteristics of the photovoltaic array. Secondly, considering the long simulation time, in order to calculate the maximum output power of the photovoltaic array under the one-year task profile in a short time, a numerical calculation method for the maximum output power of the photovoltaic array based on short step size traversal search is proposed, and the maximum power point is obtained by traversal search.

4. The method for optimizing distributed photovoltaic output in a distribution network considering the lifespan of photovoltaic inverters according to claim 1, characterized in that, Establish an IGBT thermoelectric coupling model, in which IGBT electrical losses are divided into switching losses and conduction losses. in, For IGBT conduction loss and switching loss; δ(t) is the duty cycle; i a T is the inverter output current; j_T V is the junction temperature of the IGBT; CE_25℃ This refers to the rated on-state voltage drop of the IGBT at 25°C; r CE_25℃ K is the rated on-state resistance of the IGBT at 25°C. V_T K is the temperature influence coefficient of the IGBT on-state voltage drop. r_T f is the temperature effect coefficient of the IGBT on-state resistance; sw For the IGBT module's turn-on and turn-off frequencies; K sw K1(V) is the temperature influence coefficient of IGBT switching losses. dc K2(R) represents the voltage coefficient that influences the grid-connected DC voltage of photovoltaic systems on the power loss of IGBT switches; g ) is the gate resistance R g The resistivity that affects the power loss of IGBT switches; Among them, T j T represents the junction temperature of the IGBT. a Ambient temperature; This represents the electrical losses of the IGBT and the anti-parallel diode.

5. The method for optimizing distributed photovoltaic output in a distribution network considering the lifespan of photovoltaic inverters according to claim 1, characterized in that, The ambient temperature was set to [-5 0 5 10 15 20 25 30 35 40]℃, and the photovoltaic inverter input power was set to [0 1 2 3 45 6 7 8 9 10 11]kW, and the IGBT junction temperature curves were obtained at the corresponding ambient temperatures.

6. The method for optimizing distributed photovoltaic output in a distribution network considering the lifespan of photovoltaic inverters according to claim 1, characterized in that, based on the maximum junction temperature curve of the IGBT, a quadratic polynomial fitting is performed. in, T IGBT_max denoted as the maximum junction temperature of the IGBT, p is the input power of the photovoltaic inverter, and a, b, and c are fitting coefficients.

7. The method for optimizing distributed photovoltaic output in a distribution network considering the lifespan of photovoltaic inverters as described in claim 1, characterized in that it extracts task profile data of irradiance and ambient temperature in the distribution network, distribution network topology, line parameters, and load data of each node in the distribution network.

8. The method for optimizing distributed photovoltaic output in a distribution network considering the lifespan of photovoltaic inverters as described in claim 1, characterized in that a multi-objective optimization model is established to minimize distribution network losses, active power reduction, and the maximum junction temperature of IGBTs. Objective function: minω1P net,loss +ω2P curt,loss +ω3T IGBT_max Constraints: in, P net,loss For distribution network line losses; P curt,loss For photovoltaic active power reduction; T IGBT_max P represents the maximum junction temperature of the IGBT; j, k, and l are the bus indices of the distribution network; J(k) and L(k) are the parent node and child node, respectively; P jk,t Q jk,t r jk,t x jk,t with I jk,t Let be the active power, reactive power, line resistance, line inductance, and line current from bus j to bus k at time t, respectively. V k,t The active power of the photovoltaic system at bus k, the reactive power of the photovoltaic inverter, the active load, the reactive load, and the bus voltage are respectively at time t. This represents the upper limit of the line current between bus j and bus k. V min V max These are the upper and lower limits of the distribution network voltage. Let K be the photovoltaic capacity connected at busbar k.

9. The method for optimizing distributed photovoltaic output in a distribution network considering the lifespan of photovoltaic inverters according to claim 1, characterized in that the established multi-objective optimization model is converted into a second-order cone programming model, thereby transforming the optimization problem from a non-convex optimization problem into a convex optimization problem. Introduce two variables i jk,t v k,t The established multi-objective optimization model is converted into a second-order cone programming model, whose objective function and constraints are as follows: minω1P net,loss +ω2P curt,loss +ω3T IGBT_max Constraints: in, P net,loss For distribution network line losses; P curt,loss For photovoltaic active power reduction; T IGBT_max P represents the maximum junction temperature of the IGBT; j, k, and l are the bus indices of the distribution network; J(k) and L(k) are the parent node and child node, respectively; P jk,t Q jk,t r jk,t x jk,t with i jk,t Let be the active power, reactive power, line resistance, line inductance, and square of the line current from bus j to bus k at time t. v k,t Let t represent the active power of the photovoltaic system at bus k, the reactive power of the photovoltaic inverter, the active load, the reactive load, and the square of the bus voltage, respectively. This represents the upper limit of the line current between bus j and bus k. V min V max These are the upper and lower limits of the distribution network voltage. Let K be the photovoltaic capacity connected at busbar k.

10. The method for optimizing distributed photovoltaic power output in a distribution network considering the lifespan of photovoltaic inverters according to claim 1, characterized in that the optimal reactive power output of distributed photovoltaic power in a distribution network considering the lifespan of IGBTs in photovoltaic inverters is obtained by solving the convex optimization model in S8 using the particle swarm optimization algorithm.

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