Photovoltaic area reverse heavy load and photovoltaic point overvoltage treatment method

Abstract

The invention provides a photovoltaic area reverse heavy load and photovoltaic point overvoltage treatment method. The method comprises the following steps: S1, setting two transformer regulation and control threshold parameters and two photovoltaic regulation and control threshold parameters; s2, performing data acquisition on the transformer at the gateway of the transformer area and the connected photovoltaic inverter, calculating the load rate Lall of the transformer and the maximum photovoltaic three-phase voltage Umax, and judging the state quantity St of the transformer area; and S3, after the execution of the current strategy is completed, waiting for time T and then executing the next round of data acquisition, calculation, transformer area state judgment and strategy execution. The transformer area real-time state is judged according to the current transformer area load rate and the photovoltaic point voltage, photovoltaic output is adjusted in real time through the transformer area intelligent fusion terminal, the transformer area self-governance capacity is enhanced, meanwhile, faults caused by reverse heavy loads of power equipment such as a transformer are prevented, and the situation that due to the large photovoltaic power generation amount, the transformer area self-governance capacity is affected is avoided. Therefore, the power supply reliability is improved, and the power utilization demand of the user is guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a method for controlling reverse overload in a photovoltaic area and overvoltage at a photovoltaic point. Background Art

[0002] As the world's pursuit of sustainable energy solutions continues to deepen, photovoltaic power generation and grid connection have quickly become hot topics in the new energy industry. This technology is expected to provide an innovative and efficient way to solve problems such as dependence on traditional energy and environmental pollution. At the same time, photovoltaic stations will face many problems during operation. If the light conditions are good and the photovoltaic power generation in the station is large, the excess electricity generated cannot be fully absorbed by the power system, which will cause excessive pressure on the power grid, reverse heavy overload and photovoltaic point overvoltage problems, posing hidden dangers to the power system. Summary of the invention

[0003] The present invention discloses a method for controlling reverse overload in photovoltaic areas and overvoltage at photovoltaic points. Based on the real-time load rate of the area, the method comprehensively coordinates the adjustable resources in the area to effectively control the problems of reverse overload of transformers and overvoltage at photovoltaic points caused by the inability to absorb distributed photovoltaics in the area.

[0004] The specific plan is as follows:

[0005] A method for controlling reverse overload and overvoltage at a photovoltaic area, characterized in that it is executed by an intelligent fusion terminal in the area and only controls the photovoltaic inverters in the area that have been connected to the intelligent fusion terminal, including the following steps:

[0006] S1. Set two transformer control threshold parameters and two photovoltaic control threshold parameters, where the two transformer control threshold parameters include a load rate drop threshold L down The load rate rise threshold L up , the two photovoltaic control threshold parameters include the voltage drop threshold U down With the voltage rising threshold U up ;

[0007] S2. Collect data on the gateway transformers in the substation area and the photovoltaic inverters connected to it, and calculate the transformer load rate L all The maximum photovoltaic three-phase voltage U max And determine the station state quantity St;

[0008] If L all <L down , and all photovoltaic points U max down , it means that there is only a reverse overload problem of the transformer at present, St=1, and the reverse overload control strategy is executed;

[0009] If L all ​>L down , and there is a photovoltaic point U max >U down , it means that there is only an overvoltage problem at the photovoltaic point, St=2, and the overvoltage control strategy is implemented;

[0010] If L all >L down , and all photovoltaic points U max >U down , it means that there is both a transformer reverse overload problem and a photovoltaic point overvoltage problem, St = 3, and a multi-objective governance strategy is implemented;

[0011] If L all <L down , and all photovoltaic points U max up , it means that it is currently in a safe operating state, St = 4, and the recovery strategy is executed;

[0012] In other states, St = 0, and no strategy is executed;

[0013] S3. After the current strategy is executed, wait for a period of time T before executing the next round of data collection, calculation, area status judgment and strategy execution.

[0014] Furthermore, the intelligent fusion terminal in the substation area obtains transformer gateway data, including the real-time total active power P all , real-time power factor PF, transformer capacity S c ; The photovoltaic inverter supports obtaining the three-phase voltage U of the photovoltaic grid-connected point a , U b , U c , inverter capacity P pv , real-time output active power P re ; The photovoltaic inverter supports obtaining the current set power percentage Prt pvcur , and supports the intelligent fusion terminal in the area to set the power percentage Prt pv After the PV inverter output power percentage is issued, it is not higher than Prt pv .

[0015] Furthermore, in step S1, the load rate decreases to a threshold value L down , the default value is -80%, the setting value is not greater than -50%; the load rate rise threshold L up , the default is L down +20%, set value not greater than L down +30%, should not be less than L down +10%; voltage drop threshold U down ​The default value is 110% of the rated voltage of the photovoltaic grid, that is, 242V; the voltage rise threshold U up The default value is 107% of the rated voltage of the photovoltaic grid, that is, 237.6V.

[0016] In step S2, the transformer load factor L all The calculation formula is:

[0017]

[0018] Photovoltaic three-phase maximum voltage U max The voltage value of the highest phase among the three-phase voltages is collected in real time for each photovoltaic inverter, that is, max(U a ,U b ,U c ).

[0019] Furthermore, in step S2, the reverse overload management strategy limits the output power of the photovoltaic inverter and is performed according to the following steps:

[0020] (1) Calculate the total difference of reverse heavy load active power P in the substation area df ;

[0021] (2) Calculate the theoretical value of the inverter output power percentage Prt cal ;

[0022] (3) Determine the actual inverter output power percentage Prt that needs to be issued pv , and sent to each inverter;

[0023] The total reverse heavy load active power difference P df , taking into account a 2% margin, the calculation is as follows:

[0024] P df =(L down +2%)×S c ×PF-P all

[0025] The inverter output power limit percentage theoretical value Prt cal , distribute the output reduction percentage in equal proportion; assuming that there are n inverters on site, numbered 1, 2, ...n, the Prt of the i-th inverter cal , that is, Prt cal(i) The calculation is as follows:

[0026]

[0027] The inverter output power percentage Prt pv , Prt of the i-th inverter pv , that is, Prtpv(i) The calculation is as follows:

[0028]

[0029] Furthermore, in step S2, the overvoltage control strategy limits the output power of the photovoltaic inverter and is performed according to the following steps:

[0030] (1) Calculate the theoretical value of inverter output power percentage Prt cal ;

[0031] (2) Determine the actual inverter output power percentage Prt that needs to be issued pv , and sent to each inverter;

[0032] The inverter output power percentage theoretical value Prt cal , Prt of the i-th inverter cal , that is, Prt cal(i) The calculation is as follows:

[0033]

[0034] The inverter output power percentage Prt pv , and the reverse overload management strategy Prt pv The calculation is the same.

[0035] Furthermore, in step S2, the multi-objective governance strategy limits the output power of the photovoltaic inverter and is performed according to the following steps:

[0036] (1) Calculate the total difference of reverse heavy load active power P in the substation area df ;

[0037] (2) Determine the control characteristic quantity X of each inverter;

[0038] (3) Calculate the absolute value of active power reduction P of each inverter pvdown ;

[0039] (4) Calculate the theoretical value of inverter output power percentage Prt cal ;

[0040] (5) Determine the actual inverter output power percentage Prt pv , and sent to each inverter;

[0041] The total reverse heavy load active power difference P df , and the reverse overload governance strategy P df The calculation method is the same;

[0042] The control characteristic quantity X of the inverter, X of the i-th inverter, that is, X(i) The calculation is as follows:

[0043]

[0044] The absolute value of the inverter's active power decreases P pvdown , P pvdown , P df There is the following relationship between X:

[0045]

[0046] The solution is:

[0047]

[0048] The inverter output power percentage theoretical value Prt cal , Prt of the i-th inverter cal , that is, Prt cal(i) The calculation is as follows:

[0049]

[0050] The inverter output power percentage Prt pv , and the reverse overload management strategy Prt pv The calculation is the same.

[0051] Furthermore, in step S2, the recovery strategy is to restore the output power of the photovoltaic inverter, and is performed according to the following steps:

[0052] (1) Calculate the total difference P of active power recovery in the substation area df2 ;

[0053] (2) Calculate the theoretical value of the inverter output power percentage Prt cal ;

[0054] (3) Determine the actual inverter output power percentage Prt that needs to be issued pv , and sent to each inverter;

[0055] The total active power recovery difference P df2 , taking into account a 2% margin, the calculation is as follows:

[0056] P df2 =P all -(L up -2%)×S c ×PF

[0057] The inverter output power recovery percentage theoretical value Prt cal , Prt of the i-th inverter cal , that is, Prtcal(i) The calculation is as follows:

[0058]

[0059] The inverter output power percentage Prt pv , calculated as follows:

[0060]

[0061] Furthermore, in step S3, a collection and control cycle T is set, and the substation intelligent fusion terminal performs data collection, status judgment and strategy control every T time interval.

[0062] The beneficial effects of the present invention are:

[0063] The present invention determines the real-time status of the substation according to the current load rate of the substation and the voltage of the photovoltaic point, and adjusts the photovoltaic output in real time by the intelligent fusion terminal of the substation, thereby enhancing the autonomous capability of the substation. At the same time, it prevents the failure of power equipment such as transformers due to reverse overload, avoids serious consequences such as equipment damage and short circuit caused by the large amount of photovoltaic power generation that cannot be absorbed by the substation, thereby improving the power supply reliability and ensuring the electricity demand of users. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 Flow chart of the method of the present invention.

[0065] Figure 2 This is an execution flow chart of the reverse overload management strategy in the present invention.

[0066] Figure 3 This is a flowchart for executing the overvoltage control strategy in the present invention.

[0067] Figure 4 This is an execution flow chart of the reverse overload management strategy in the present invention.

[0068] Figure 5 This is a flowchart of the execution of the recovery strategy in the present invention. DETAILED DESCRIPTION

[0069] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0070] like Figure 1 As shown, in the embodiment of the present invention, a method for managing reverse overload and overvoltage at photovoltaic points in a photovoltaic area is provided, and all data collection, identification, calculation and management of the area are performed by the intelligent fusion terminal of the area. The specific steps are as follows:

[0071] First, set the transformer control threshold parameters, load rate drop threshold Ldown The load rate rise threshold L up , and two photovoltaic control threshold parameters, voltage drop threshold U down With the voltage rising threshold U up Then, data is collected on the gateway transformers in the substation area and the photovoltaic inverters connected to it, and the transformer load rate and the maximum photovoltaic three-phase voltage U are calculated. max And judge the status of the area. all <L down , and all photovoltaic points U max down , it means that there is only a reverse overload problem of the transformer at present, St=1, and the reverse overload control strategy is executed; if L all >L down , and there is a photovoltaic point U max >U down , it means that there is only an overvoltage problem at the photovoltaic point, St=2, and the overvoltage control strategy is implemented; if L all >L down , and all photovoltaic points U max >U down , it means that there is both a transformer reverse overload problem and a photovoltaic point overvoltage problem. St=3, and a multi-objective governance strategy is implemented. If L all <L down , and all photovoltaic points U max up , it means that it is currently in a safe operation state, St = 4, and the recovery strategy is executed; in other states, St = 0, and no strategy is executed. After the current strategy is executed, the next round of data collection, calculation, station status judgment and strategy execution will be executed after waiting for time T.

[0072] When the station state quantity St=1, the execution process is as follows Figure 2 As shown, first calculate the total power of the current area and the transformer load rate at L down The power difference P df , consider a 2% margin when calculating. Then calculate the theoretical value of the inverter output power percentage Prt cal The calculation principle is to distribute the output power reduction percentage to each inverter in equal proportion. Then determine the actual inverter output power percentage Prt pv , if Prt cal <0, then Prt pv Take 0, otherwise take Prt cal Finally, the output power percentage Prt pv Send it to each inverter.

[0073] When the station state quantity St = 2, the execution process is as follows Figure 3 ​​As shown, first calculate the theoretical value of the inverter output power percentage Prt cal , according to the U max Determine the percentage of power reduction, exceeding U down The output power drops by 20%, U up with U down Between 10% decline, U up The actual inverter output power percentage Prt to be issued is then determined. pv , if Prt cal <0, then Prt pv Take 0, otherwise take Prt cal Finally, the output power percentage Prt pv Send it to each inverter.

[0074] When the station state quantity St = 3, the execution process is as follows Figure 4 As shown, first calculate the total power of the current area and the transformer load rate at L down The power difference P df , a 2% margin is considered in the calculation. Then determine the control characteristic value X of each inverter, which is determined by the inverter's U max Decision, U max The larger the value, the larger the X. The ratio between X is the ratio between the percentage of inverter power reduction. The absolute value of the power reduction of all inverters is P. pvdown The sum is P df After listing the relationship, we can solve the absolute value of active power drop of each inverter P pvdown Then determine the actual inverter output power percentage Prt that needs to be sent. pv , if Prt cal <0, then Prt pv Take 0, otherwise take Prt cal Finally, the output power percentage Prt pv Send it to each inverter.

[0075] When the station state quantity St = 3, the execution process is as follows Figure 5 As shown. First, calculate the current area power and transformer load rate at L up The power difference P df2 , consider a 2% margin when calculating. Then calculate the theoretical value of the inverter output power percentage Prt cal The calculation principle is to distribute the output power recovery percentage to each inverter in equal proportion. Then determine the actual inverter output power percentage Prt that needs to be issued pv , if Prt cal <Prt pvcur , then take Prt pvcur ; If Prtcal ≥100%, then take 100%, otherwise take Prt cal Finally, the output power percentage Prt pv Send it to each inverter.

[0076] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above-mentioned technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A method for controlling reverse overload in photovoltaic area and overvoltage in photovoltaic point, characterized in that: It is executed by the intelligent fusion terminal in the substation area, and only controls the photovoltaic inverters that have been connected to the intelligent fusion terminal in the substation area, including the following steps: S1. Set two transformer control threshold parameters and two photovoltaic control threshold parameters, where the two transformer control threshold parameters include a load rate drop threshold L down The load rate rise threshold L up , the two photovoltaic control threshold parameters include the voltage drop threshold U down With the voltage rising threshold U up ; S2. Collect data on the gateway transformers in the substation area and the photovoltaic inverters connected to it, and calculate the transformer load rate L all The maximum photovoltaic three-phase voltage U max And determine the station state quantity St; If L all <L down , and all photovoltaic points U max down , it means that there is only a reverse overload problem of the transformer at present, St=1, and the reverse overload control strategy is executed;​ If L all >L down , and there is a photovoltaic point U max >U down , it means that there is only an overvoltage problem at the photovoltaic point, St=2, and the overvoltage control strategy is implemented; If L all >L down , and all photovoltaic points U max >U down , it means that there is both a transformer reverse overload problem and a photovoltaic point overvoltage problem, St = 3, and a multi-objective governance strategy is implemented; If L all <L down , and all photovoltaic points U max up , it means that it is currently in a safe operating state, St = 4, and the recovery strategy is executed;​ In other states, St = 0, and no strategy is executed; S3. After the current strategy is executed, wait for a period of time T before executing the next round of data collection, calculation, area status judgment and strategy execution.

2. A method for controlling reverse overload in photovoltaic area and overvoltage in photovoltaic point according to claim 1, characterized in that: The intelligent fusion terminal in the substation area obtains the transformer gateway data, including the real-time total active power P of the substation area. all , real-time power factor PF, transformer capacity S c The photovoltaic inverter supports obtaining the three-phase voltage U of the photovoltaic grid-connected point a , U b , U c , inverter capacity P pv , real-time output active power P re ; The photovoltaic inverter supports obtaining the current set power percentage Prt pvcur , and supports the intelligent fusion terminal in the area to set the power percentage Prt pv After the PV inverter output power percentage is issued, it is not higher than Prt pv .

3. A method for controlling reverse overload in photovoltaic area and overvoltage in photovoltaic point according to claim 2, characterized in that: In step S1, the load rate decreases to a threshold value L down , the default value is -80%, the setting value is not greater than -50%; the load rate rise threshold L up , the default is L down +20%, set value not greater than L down +30%, should not be less than L down +10%; voltage drop threshold U down The default value is 110% of the rated voltage of the photovoltaic grid, that is, 242V; the voltage rise threshold U up The default value is 107% of the rated voltage of the photovoltaic grid, that is, 237.6V.

4. A method for controlling reverse overload in photovoltaic area and overvoltage in photovoltaic point according to claim 3, characterized in that: In step S2, the transformer load factor L all The calculation formula is: The photovoltaic three-phase maximum voltage U max The voltage value of the highest phase among the three-phase voltages is collected in real time for each photovoltaic inverter, that is, max(U a ,U b ,U c ).

5. A method for controlling reverse overload and overvoltage in photovoltaic areas according to claim 4, characterized in that: In step S2, the reverse overload management strategy limits the output power of the photovoltaic inverter and is performed according to the following steps: (1) Calculate the total difference of reverse heavy load active power P in the substation area df ; (2) Calculate the theoretical value of the inverter output power percentage Prt cal ; (3) Determine the actual inverter output power percentage Prt that needs to be issued pv , and sent to each inverter; The total reverse heavy load active power difference P df , taking into account a 2% margin, the calculation is as follows: P df =(L down +2%)×S c ×PF-P all The inverter output power limit percentage theoretical value Prt cal , distribute the output reduction percentage in equal proportion; assuming that there are n inverters on site, numbered 1, 2, ...n, the Prt of the i-th inverter cal , that is, Prt cal(i) The calculation is as follows: The inverter output power percentage Prt pv , Prt of the i-th inverter pv , that is, Prt pv(i) The calculation is as follows:

6. A method for controlling reverse overload in photovoltaic area and overvoltage in photovoltaic point according to claim 5, characterized in that: In step S2, the overvoltage control strategy limits the output power of the photovoltaic inverter and is performed according to the following steps: (1) Calculate the theoretical value of inverter output power percentage Prt cal ; (2) Determine the actual inverter output power percentage Prt that needs to be issued pv , and sent to each inverter; The inverter output power percentage theoretical value Prt cal , Prt of the i-th inverter cal , that is, Prt cal(i) The calculation is as follows: The inverter output power percentage Prt pv , and the reverse overload management strategy Prt pv The calculation is the same.

7. A method for controlling reverse overload in photovoltaic area and overvoltage in photovoltaic point according to claim 6, characterized in that: In step S2, the multi-objective governance strategy limits the output power of the photovoltaic inverter and is performed according to the following steps: (1) Calculate the total difference of reverse heavy load active power P in the substation area df ; (2) Determine the control characteristic quantity X of each inverter; (3) Calculate the absolute value of active power reduction P of each inverter pvdown ; (4) Calculate the theoretical value of inverter output power percentage Prt cal ; (5) Determine the actual inverter output power percentage Prt pv , and sent to each inverter; The total reverse heavy load active power difference P df , and the reverse overload governance strategy P df The calculation method is the same; The control characteristic quantity X of the inverter, X of the i-th inverter, that is, X (i) The calculation is as follows: The absolute value of the inverter's active power decreases P pvdown , P pvdown , P df There is the following relationship between X: The solution is: The inverter output power percentage theoretical value Prt cal , Prt of the i-th inverter cal , that is, Prt cal(i) The calculation is as follows: The inverter output power percentage Prt pv , and the reverse overload management strategy Prt pv The calculation is the same.

8. A method for controlling reverse overload in photovoltaic area and overvoltage in photovoltaic point according to claim 7, characterized in that: In step S2, the recovery strategy is to restore the output power of the photovoltaic inverter, and is performed according to the following steps: (1) Calculate the total difference P of active power recovery in the substation area df2 ; (2) Calculate the theoretical value of the inverter output power percentage Prt cal ; (3) Determine the actual inverter output power percentage Prt that needs to be issued pv , and sent to each inverter; The total active power recovery difference P df2 , taking into account a 2% margin, the calculation is as follows: P df2 =P all -(L up -2%)×S c ×PF The inverter output power recovery percentage theoretical value Prt cal , Prt of the i-th inverter cal , that is, Prt cal(i) The calculation is as follows: The inverter output power percentage Prt pv , calculated as follows:

9. A method for controlling reverse overload in photovoltaic area and overvoltage in photovoltaic point according to claim 1, characterized in that: In step S3, a collection and control cycle T is set, and the intelligent fusion terminal in the substation performs data collection, status judgment and strategy control every time T.

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