Method and system for solving standard exceeding of force regulation electric charge of centralized photovoltaic power station

Abstract

The invention discloses a centralized photovoltaic power station force regulation electric charge standard exceeding solving method, which comprises the following steps of: obtaining a mathematical model of a power transmission line L based on historical data obtained by a centralized photovoltaic power station grid-connected measurement meter and the mathematical model of the power transmission line L; calculating to obtain monthly four-quadrant calculated active electric quantity and monthly four-quadrant calculated reactive electric quantity of a photovoltaic power station metering gateway meter in front of a grid-connected bus G of a superior substation; calculating an estimated value of the charging power of the power transmission line by using a weighted least square method according to monthly four-quadrant calculation active electric quantity, monthly four-quadrant calculation reactive electric quantity and actual values of the monthly four-quadrant calculation active electric quantity and the monthly four-quadrant calculation reactive electric quantity of the photovoltaic power station metering gateway meter; according to the estimated value of the charging power of the power transmission line, reactive power is given out by a reactive power compensation device in the centralized photovoltaic power station, and it is guaranteed that the force adjustment electric charge of the centralized photovoltaic power station does not exceed the standard. The invention further discloses a system for solving the problem that the force regulation electric charge of the centralized photovoltaic power station exceeds the standard. According to the invention, the operation economy of the centralized photovoltaic power station is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of optimized operation in the field of comprehensive new energy power generation, and in particular to a solution to excessive power regulation charges in a centralized photovoltaic power station and a system thereof. Background Art

[0002] At present, with the gradual decline in the cost of photovoltaic power generation, centralized photovoltaic power stations have been rapidly developed in rural areas of my country. However, these photovoltaic power stations are mostly built in remote rural areas far away from the upper substations, and have high grid-connected voltages, generally 35kV and above, large grid-connected capacity, generally more than 100MW, and long grid-connected distances, generally several kilometers or even tens of kilometers away from the upper substation. Therefore, it is particularly important to reasonably plan and design the reactive power compensation of photovoltaic power stations, otherwise it will lead to excessive power charges for photovoltaic power stations.

[0003] The situation of excessive power-adjustment charges in photovoltaic power plants is usually related to the power factor management of the power plant. Power factor refers to the ratio of useful work (active power) to apparent power (i.e., the vector sum of active power and reactive power). When the power factor of a photovoltaic power plant is lower than the threshold specified by the power company, power-adjustment charges will be incurred. The current status of research on power-adjustment charges includes the following aspects: 1) Power factor control. With the development of technology, most modern photovoltaic grid-connected inverters have adjustable power factor functions, which can provide reactive power support to a certain extent to improve the power factor of the overall system. Some research focuses on how to better utilize these functions to avoid power-adjustment charges. 2) Reactive compensation technology. In addition to utilizing the characteristics of the inverter itself, the power factor of the system can be improved by installing a static VAR compensator (SVC), a static VAR generator (SVG) or other reactive compensation equipment, thereby reducing or eliminating power-adjustment charges. 3) Data analysis and prediction: Through in-depth analysis of power plant operation data, it is possible to predict when the power-regulated electricity fee will exceed the standard and take measures to adjust it in advance. Research in this area may involve the application of big data processing and machine learning algorithms. 4) Policies and standards: With the popularization of photovoltaic power plants, local governments and power companies are also constantly adjusting relevant policies and technical specifications to adapt to the new energy situation. These policy changes will also affect how photovoltaic power plant operators manage and deal with the problem of power-regulated electricity fees.

[0004] In summary, current research focuses on optimizing the operating status of photovoltaic power plants through technical and economic means to reduce or even eliminate the additional electricity costs caused by insufficient power factor. At the same time, with the advancement of technology and changes in policies, research in this field is also continuing to develop.

[0005] Therefore, it is urgent to provide a new centralized photovoltaic power station power regulation method to solve the above problem. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a solution and system for the problem of excessive power-adjusting electricity charges in a centralized photovoltaic power station, which can effectively improve the power factor at the gateway meter, avoid the grid company's assessment of the power-adjusting electricity charges of the photovoltaic power station, and greatly improve the economy of the operation of the photovoltaic power station.

[0007] In order to solve the above technical problems, a technical solution adopted by the present invention is to provide a solution to the excessive power regulation fee of a centralized photovoltaic power station, comprising the following steps:

[0008] Step 1: Based on the historical data obtained from the grid-connected measurement meter of the centralized photovoltaic power station and the mathematical model of the transmission line L, the monthly four-quadrant calculated active power and the monthly four-quadrant calculated reactive power of the photovoltaic power station metering gateway meter in front of the grid-connected bus G of the upper-level substation are calculated.

[0009] Step 2: Using the weighted least squares method, the monthly four-quadrant calculation of active power and the monthly four-quadrant calculation of reactive power and their actual values ​​of the photovoltaic power station metering gateway table are used to calculate the estimated value of the charging power of the transmission line.

[0010] Step 3: Estimated value of charging power based on transmission line The reactive power Q generated by the reactive power compensation device in the centralized photovoltaic power station is given as C , to ensure that the power adjustment fee of centralized photovoltaic power stations does not exceed the standard; the specific steps include:

[0011] Real-time monitoring of the size and direction of the active power Ps sent by the centralized photovoltaic power station. Once Ps>0 and is lower than the set threshold, the reactive power Q generated by the reactive power compensation device in the substation is controlled. C , so that it satisfies the following formula:

[0012]

[0013] That is, to ensure that the power factor of the photovoltaic power station metering gateway meets the requirements of the power grid company, so that the power adjustment fee of the centralized photovoltaic power station does not exceed the standard;

[0014] When Ps<0, no requirements are made on the reactive power compensation device.

[0015] In a preferred embodiment of the present invention, the specific steps of step 1 include:

[0016] Step 1.1: Assume that the grid-connected meter uses Δt as the sampling interval to measure the power P delivered by the centralized photovoltaic power station. S +jQ S Sampling and storage, where: P S and Q Sare the active power and reactive power delivered by the centralized photovoltaic power station respectively; assuming that the positive direction of power is from the centralized photovoltaic power station to the upper substation, then according to the measured Ps and Q S The power flowing out of the photovoltaic power generation system grid-connected bus S is divided into four quadrants, among which: in the first quadrant, Ps>0, Q S >0 is established; in the second quadrant, Ps < 0, Q S >0 is established; in the third quadrant, Ps <0, QS <0 is established; in the fourth quadrant, Ps > 0, Q S <0 is established;

[0017] Step 1.2: Let Δt be the sampling time interval of the grid-connected meter, and according to Ps and Q S In the direction of , the number of duration periods in the four quadrants in the i-th month is counted as T1, T2, T3 and T4 respectively;

[0018] Assume that in the first quadrant period t in the i-th month, the active power and reactive power delivered by the centralized photovoltaic power station are and Based on the mathematical model of the transmission line L, the monthly first quadrant calculated active power and monthly first quadrant calculated reactive power of the photovoltaic power station metering gateway in the i-th month are calculated by calculation. The specific expressions are as follows:

[0019]

[0020] in: and They are respectively the monthly first quadrant calculated active power and monthly first quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the first quadrant period t in the i-th month; is the current delivered by the centralized photovoltaic power station in the first quadrant during period t in month i; R L , X L and Q LC are the resistance, reactance and charging power to the ground of the transmission line L, which are regarded as constants;

[0021] Similarly, similar methods are used to obtain the monthly calculated active power and monthly calculated reactive power of other quadrants in the ith month of the photovoltaic power station metering gateway table. The calculation formulas are as follows:

[0022]

[0023] in: and They are respectively the monthly second quadrant calculated active power and monthly second quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the second quadrant period t in the i-th month; is the current delivered by the centralized photovoltaic power station in the second quadrant during period t in month i;

[0024]

[0025] in: and They are respectively the monthly third quadrant calculated active power and the monthly third quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the third quadrant period t in the i-th month; is the current delivered by the centralized photovoltaic power station in the third quadrant period t in the i-th month;

[0026]

[0027] in: and They are respectively the monthly fourth quadrant calculated active power and the monthly fourth quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the fourth quadrant period t in the i-th month; It is the current delivered by the centralized photovoltaic power station in the fourth quadrant period t in the i-th month.

[0028] In a preferred embodiment of the present invention, the specific steps of step 2 include:

[0029] set up and are the calculated active power and reactive power of the i-th month and j-th quadrant respectively. and They are the monthly settled active power and monthly settled reactive power of the power grid company in the i-th month and the j-th quadrant respectively;

[0030] Step 2.1: Construct the objective function of the weighted least squares method, as shown in the following formula:

[0031]

[0032] Where n is the number of historical months; Solving the above optimization problem, we can get the estimated value Q′ of the charging power of the transmission line: LC ;

[0033] Step 2.2: Construct the objective function of the weighted least squares method, as shown in the following formula:

[0034]

[0035] Where n is the number of historical months. Solving the above optimization problem, we can get the estimated value Q″ of the charging power of the transmission line: LC ;

[0036] Step 2.3: Based on the estimated values ​​of the transmission line charging power obtained in steps 2.1 and 2.2, further calculate the estimated value of the transmission line charging power The specific formula is as follows:

[0037]

[0038] In order to solve the above technical problems, another technical solution adopted by the present invention is: to provide a system for solving the problem of excessive power regulation electricity charges in a centralized photovoltaic power station, adopting the solution to the problem of excessive power regulation electricity charges in a centralized photovoltaic power station as described in any of the above items, including:

[0039] The photovoltaic power station metering gateway meter power calculation module is used to calculate the monthly four-quadrant calculated active power and the monthly four-quadrant calculated reactive power of the photovoltaic power station metering gateway meter before the upper-level substation grid-connected bus G based on the historical data obtained from the centralized photovoltaic power station grid-connected measurement meter and the mathematical model of the transmission line L;

[0040] The transmission line charging power estimation calculation module is used to calculate the estimated value of the transmission line charging power by using the weighted least squares method, based on the monthly four-quadrant calculated active power and monthly four-quadrant calculated reactive power of the photovoltaic power station metering gateway meter calculated by the photovoltaic power station metering gateway meter power calculation module and their actual values.

[0041] Centralized photovoltaic power station power adjustment fee module, used to estimate the charging power of the transmission line The reactive power Q generated by the reactive power compensation device in the centralized photovoltaic power station is given as C , to ensure that the electricity charges of centralized photovoltaic power stations do not exceed the standards.

[0042] In a preferred embodiment of the present invention, the method for the centralized photovoltaic power station power adjustment electricity fee module to ensure that the centralized photovoltaic power station power adjustment electricity fee does not exceed the standard includes:

[0043] Real-time monitoring of the size and direction of the active power Ps sent by the centralized photovoltaic power station. Once Ps>0 and is lower than the set threshold, the reactive power Q generated by the reactive power compensation device in the substation is controlled. C, so that it satisfies the following formula:

[0044]

[0045] That is, to ensure that the power factor of the photovoltaic power station metering gateway meets the requirements of the power grid company, so that the power adjustment fee of the centralized photovoltaic power station does not exceed the standard;

[0046] When Ps<0, no requirements are made on the reactive power compensation device.

[0047] The beneficial effects of the present invention are:

[0048] (1) The present invention creatively utilizes the historical real-time measurement data of the centralized photovoltaic power station itself and the monthly data provided by the upper-level substation, and adopts mathematical and statistical analysis methods to achieve the estimation of the operation data of high-voltage and long-distance transmission lines, thus overcoming the defect that it is difficult to obtain non-self-data such as line operation data;

[0049] (2) The present invention proposes a weighted least squares method, based on the data that can be obtained by itself, creatively regards the line operation as a linear characteristic, and estimates the line operation data, which significantly improves the accuracy of the power system operation state estimation;

[0050] (3) The present invention proposes an action strategy suitable for the reactive power compensation device inside a centralized photovoltaic power station, which effectively improves the power factor at the gateway meter, avoids the grid company's assessment of the photovoltaic power station's power regulation fee, and greatly improves the economic efficiency of the photovoltaic power station's operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a flow chart of a solution to excessive power charges in centralized photovoltaic power stations according to the present invention;

[0052] Figure 2 It is a schematic diagram of the connection relationship between a centralized photovoltaic power station and its upper-level substation;

[0053] Figure 3 It is the reactive power compensation flow chart of the substation in step 3;

[0054] Figure 4 It is a structural block diagram of the system for solving the problem of excessive power charges in centralized photovoltaic power stations. DETAILED DESCRIPTION

[0055] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0056] First, a detailed description of centralized photovoltaic power plants and their related power is given:

[0057] like Figure 2 As shown, the centralized photovoltaic power station consists of a photovoltaic power generation system, a station power system and a reactive power compensation device, which is connected to the transmission line L through the photovoltaic power generation system grid-connected bus S. At the same time, the other end of the transmission line L is also connected to the upper-level substation grid-connected bus G.

[0058] The output power of the photovoltaic power generation system is determined by the Figure 2 The measurement meter 2 shown in the figure measures in real time. Assume that the output power of the photovoltaic power generation system at a certain moment is P PV +jQ PV , where P PV and Q PV They are respectively the active power and reactive power output by the photovoltaic power generation system. The photovoltaic power generation system includes not only photovoltaic power generation equipment, but also power lines (mostly power cable lines) used to connect photovoltaic power generation equipment scattered in different locations. Since photovoltaic power generation equipment generally adopts maximum power point tracking control, photovoltaic power generation equipment does not emit reactive power, and the power lines of photovoltaic power generation systems are generally long, and the reactive power emitted by the power lines is relatively large. Therefore, when the photovoltaic power generation system is connected to the grid for power generation, the reactive power Q output by the photovoltaic power generation system obtained by measuring meter 2 in real time is PV It is usually a larger fixed value.

[0059] The output power P of a centralized photovoltaic power station S +jQ S (ie: outflow Figure 2 The power of the grid-connected busbar S of the photovoltaic power generation system is provided by the Figure 2 The measurement meter 1 in the real-time measurement is obtained, where P S and Q S They are respectively the active power and reactive power delivered by the centralized photovoltaic power station.

[0060] In actual operation, a centralized photovoltaic power station needs to provide electricity for its internal production and life. Assuming that the power required by the power system of the station is P Z +jQ Z , where P Z and Q Z are active power and reactive power respectively.

[0061] At the same time, in order to ensure the voltage stability of centralized photovoltaic power stations, reactive power compensation devices are generally installed. Assuming that the power generated by the reactive power compensation device is jQ C .

[0062] Therefore, the balance relationship between the power delivered by the centralized photovoltaic power station, the output power of the photovoltaic power generation system, the power generated by the reactive power compensation device, and the power required by the station power system can be obtained, as follows:

[0063]

[0064] Since centralized photovoltaic power stations are usually large-scale and far away from the upper substation, it is necessary to transmit the output power of the centralized photovoltaic power station to the grid-connected bus G of the upper substation through the transmission line L at a high voltage (mostly 110kV and above) and a long distance (often tens of kilometers). However, due to the impedance R of the transmission line L, the output power of the centralized photovoltaic power station needs to be transmitted to the grid-connected bus G of the upper substation at a high voltage (mostly 110kV and above) and a long distance (often tens of kilometers). L +jX L Its earth-to-ground susceptance jB L / 2, resulting in the inevitable transmission power loss ΔP of the transmission line L L +jΔQ L , its active power loss ΔP L and reactive power loss ΔQ L They are:

[0065]

[0066] Where: Q LC is called the charging power of the line, In actual operation, due to the voltage U of the busbars at both ends of line L S and U G is approximately equal to the rated voltage of the line, so the charging power Q LC Approximately regarded as a constant.

[0067] In this way, the power P measured by the photovoltaic power station metering gateway installed in front of the grid-connected bus G of the upper substation and at the end of the transmission line L is G +jQ G It can be expressed by the following formula:

[0068]

[0069] The grid company's assessment basis for the power regulation fee of photovoltaic power stations is: the power factor of the photovoltaic power station metering gateway It must be greater than the grid company's requirement (usually 0.9), and P G +jQ G The power factor can be calculated The specific formula is as follows:

[0070]

[0071] Note that the power generated by the reactive power compensation device in the centralized photovoltaic power station is C Based on the photovoltaic power station output power P obtained by measuring meter 1 S +jQ S , through closed-loop feedback control, Q Sis 0, and the following equation holds true.

[0072]

[0073] Substituting formulas (1) to (3) and formula (5) into formula (4), we can obtain the power factor of the photovoltaic power station metering gateway table used by the power supply company for power regulation electricity fee assessment: The detailed expression of:

[0074]

[0075] When the sunshine is strong and the photovoltaic power generation is strong, the output active power P of the photovoltaic power generation system PV Very large, much larger than the active power required by the station power system, that is, P PV >>P Z Moreover, the active power output of the photovoltaic power generation system is much greater than the active power loss on the line, that is, P PV >>ΔP L .

[0076] Therefore, formula (6) can be simplified as:

[0077]

[0078] At this time, the charging power of the line is Q LC Much smaller than P PV , the power factor at the photovoltaic power station metering gateway The value is higher than the grid company’s assessment value of 0.8, and the photovoltaic power station is unable to adjust the electricity fee assessment fine.

[0079] However, when the photovoltaic power generation is small or non-existent, the output active power P of the photovoltaic power generation system PV It can be regarded as 0, and formula (6) is simplified to:

[0080]

[0081] Generally speaking, the active power P required by the power system in a photovoltaic power station is Z is very small, so further simplifying formula (8) yields the following formula:

[0082]

[0083] As mentioned above, due to the voltage U across the transmission line L S and U G Approximately equal to the rated voltage of the line, the charging power of the line is Q LC Approximately regarded as a constant. Since the active power P required by the photovoltaic power station power system Z Q LCTherefore, the power factor of the photovoltaic power station metering gateway obtained by the above formula is Small, lower than the grid company's assessment value of 0.8, needs to pay a certain amount of power dispatching electricity fee assessment penalty.

[0084] Obviously, the power factor at the photovoltaic power station metering gateway is The main reason for failure is that due to the failure to understand the line parameters in detail, the active power loss ΔP generated on line L L and reactive power loss ΔQ L It is impossible to calculate, and thus it is impossible to effectively guide the reactive power compensation device in the photovoltaic power station to perform effective reactive power compensation, which in turn causes the power factor of the photovoltaic power station metering gateway in the superior substation to be unqualified.

[0085] Therefore, in order to effectively solve the above problems, the present invention proposes a solution and system for the excessive power charges of centralized photovoltaic power stations, such as Figure 1 As shown, the solution includes the following steps:

[0086] Step 1: Based on the historical data obtained from the centralized photovoltaic power station grid-connected measurement meter 1 and the mathematical model of the transmission line L, the monthly four-quadrant calculated active power and monthly four-quadrant calculated reactive power of the photovoltaic power station metering gateway meter before the upper-level substation grid-connected bus G are calculated. The specific steps include:

[0087] Step 1.1: Assume that the grid-connected meter 1 takes Δt as the sampling time interval. Figure 2 The centralized photovoltaic power station output power P S +jQ S Sampling and storage, where: P S and Q S are the active power and reactive power delivered by the centralized photovoltaic power station. Assuming that the positive direction of power is from the centralized photovoltaic power station to the upper substation, according to the measured Ps and Q S The power flowing out of bus S is divided into four quadrants, among which: in the first quadrant, Ps>0, Q S >0 is established; in the second quadrant, Ps < 0, Q S >0 is established; in the third quadrant, Ps < 0, Q S <0 is established; in the fourth quadrant, Ps>0, Q S <0 is established;

[0088] Step 1.2: Let Δt be the sampling time interval of meter 1, according to Ps and Q S In the direction of , the number of duration periods in the four quadrants in the i-th month is counted as T1, T2, T3 and T4 respectively;

[0089] Assume that in the first quadrant period t in the i-th month, the active power and reactive power delivered by the centralized photovoltaic power station are and Based on the mathematical model of the transmission line L (such as Figure 2 The transmission line L is shown in the dotted box), and the monthly first quadrant calculated active power and monthly first quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month can be obtained by calculation. The specific expressions are as follows:

[0090]

[0091] in: and They are respectively the monthly first quadrant calculated active power and monthly first quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the first quadrant period t in the i-th month; is the current delivered by the centralized photovoltaic power station in the first quadrant during period t in month i; R L , X L and Q LC They are the resistance, reactance and charging power to the ground of the transmission line L, and these three quantities can be regarded as constants.

[0092] Similarly, similar methods can be used to obtain the monthly calculated active power and monthly calculated reactive power of other quadrants in the ith month of the photovoltaic power station metering gateway table. The calculation formulas are as follows:

[0093]

[0094] in: and They are respectively the monthly second quadrant calculated active power and monthly second quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the second quadrant period t in the i-th month; It is the current delivered by the centralized photovoltaic power station in the second quadrant during period t in the i-th month.

[0095]

[0096] in: and They are respectively the monthly third quadrant calculated active power and the monthly third quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the third quadrant period t in the i-th month; It is the current delivered by the centralized photovoltaic power station in the third quadrant period t in the i-th month.

[0097]

[0098] in: and They are respectively the monthly fourth quadrant calculated active power and the monthly fourth quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the fourth quadrant period t in the i-th month; It is the current delivered by the centralized photovoltaic power station in the fourth quadrant period t in the i-th month.

[0099] Step 2: Using the weighted least squares method, the monthly four-quadrant active power calculation and the monthly four-quadrant reactive power calculation of the photovoltaic power station metering gateway table and their actual values ​​are used to calculate the charging power of the transmission line;

[0100] Based on the monthly four-quadrant calculation of active power and monthly four-quadrant calculation of reactive power and their real measurement value historical data of the photovoltaic power station metering gateway table, the charging power of the transmission line is calculated using the weighted least squares method. and are the calculated active power and reactive power of the i-th month and j-th quadrant respectively, and and They are the monthly settled active power and monthly settled reactive power of the power grid company in the i-th month and the j-th quadrant respectively. These two values ​​can be regarded as the real measurement values ​​of the metering gateway of the photovoltaic power station.

[0101] because With R L Linearly related, With X L and Q LC Therefore, the least squares method based on historical data can be used to estimate R L , X L and Q LC The value of .

[0102] Step 2.1: Construct the objective function of the weighted least squares method, as shown in the following formula:

[0103]

[0104] Where: n is the number of historical months.

[0105] Solving the above optimization problem, we can get the estimated value Q′ of the charging power of the transmission line: LC In practical applications, commercial optimization software such as Cplex and Gurobi can be used to solve the above optimization problems.

[0106] Step 2.2: Construct the objective function of the weighted least squares method, as shown in the following formula:

[0107]

[0108] Where: n is the number of historical months.

[0109] Solving the above optimization problem, we can get the estimated value Q of the charging power of the transmission line: LC In practical applications, commercial optimization software such as Cplex and Gurobi can be used to solve the above optimization problems.

[0110] Step 2.3: Based on the estimated values ​​of the transmission line charging power obtained in steps 2.1 and 2.2, further calculate the estimated value of the transmission line charging power The specific formula is as follows:

[0111]

[0112] Step 3: According to the charging power of the transmission line, the reactive power generated by the reactive power compensation device in the centralized photovoltaic power station is given to ensure that the power regulation fee of the centralized photovoltaic power station does not exceed the standard.

[0113] Real-time monitoring of the size and direction of the active power Ps delivered by the centralized photovoltaic power station, such as Figure 3 As shown in Figure 2, once Ps is greater than 0 and lower than a certain threshold, the reactive power Q generated by the reactive power compensation device in the substation is controlled. c , so that it satisfies the following formula:

[0114]

[0115] In this way, the power factor of the photovoltaic power station metering gateway can be guaranteed to meet the requirements of the power grid company, so that the power adjustment fee of the centralized photovoltaic power station does not exceed the standard. Preferably, the threshold can be set to be lower than 10% of the rated installed capacity of the photovoltaic power station.

[0116] When Ps is located in the second or third quadrant, no requirements are made on the reactive power compensation device, and the reactive power compensation device can execute other instructions.

[0117] The present invention is only based on the statistical analysis of the historical operation data of the centralized photovoltaic power station itself, and can realize the estimation of the charging power of the high-voltage long-distance transmission line of the centralized photovoltaic power station to the ground. The larger the amount of data, the higher the analysis accuracy, which provides an accurate and effective theoretical guidance basis for the operation of the reactive compensation device in the centralized photovoltaic power station, thereby significantly improving the power factor at the gateway meter of the photovoltaic power station, overcoming the drawbacks of blind adjustment of reactive compensation in traditional photovoltaic power stations, and effectively improving the economy of the operation of the centralized photovoltaic power station.

[0118] See also Figure 4 The example of the present invention also provides a system for solving the problem of excessive power charges in a centralized photovoltaic power station, including:

[0119] The photovoltaic power station metering gateway meter power calculation module is used to calculate the monthly four-quadrant calculated active power and the monthly four-quadrant calculated reactive power of the photovoltaic power station metering gateway meter before the upper-level substation grid-connected bus G based on the historical data obtained from the centralized photovoltaic power station grid-connected measurement meter and the mathematical model of the transmission line L;

[0120] The transmission line charging power estimation calculation module is used to calculate the estimated value of the transmission line charging power by using the weighted least squares method, based on the monthly four-quadrant calculated active power and monthly four-quadrant calculated reactive power of the photovoltaic power station metering gateway meter calculated by the photovoltaic power station metering gateway meter power calculation module and their actual values.

[0121] Centralized photovoltaic power station power adjustment fee module, used to estimate the charging power of the transmission line The reactive power Q generated by the reactive power compensation device in the centralized photovoltaic power station is given as C , to ensure that the electricity charges of centralized photovoltaic power stations do not exceed the standards.

[0122] The method for the centralized photovoltaic power station power adjustment electricity fee module to ensure that the centralized photovoltaic power station power adjustment electricity fee does not exceed the standard includes:

[0123] Real-time monitoring of the size and direction of the active power Ps sent by the centralized photovoltaic power station. Once Ps>0 and is lower than the set threshold, the reactive power Q generated by the reactive power compensation device in the substation is controlled. C , so that it satisfies the following formula:

[0124]

[0125] That is, to ensure that the power factor of the photovoltaic power station metering gateway meets the requirements of the power grid company, so that the power adjustment fee of the centralized photovoltaic power station does not exceed the standard;

[0126] When PS < 0, no requirements are made on the reactive power compensation device.

[0127] The system for solving the problem of excessive power regulation electricity charges in a centralized photovoltaic power station in this example can execute the solution to the problem of excessive power regulation electricity charges in a centralized photovoltaic power station provided by the present invention, can execute any combination of implementation steps in the method example, and has the corresponding functions and beneficial effects of the method.

[0128] It can be seen from the above technical scheme that the beneficial effects of the present invention are: first, the present invention creatively utilizes the historical real-time measurement data of the centralized photovoltaic power station itself and the monthly data provided by the superior substation, and adopts mathematical and statistical analysis methods to realize the estimation of the operation data of high-voltage and long-distance transmission lines, and overcomes the defect that non-self-data such as line operation data are difficult to obtain; second, a weighted least squares method is proposed, based on the data that can be obtained by itself, the line operation is creatively regarded as a linear characteristic, and the line operation data is estimated, which significantly improves the accuracy of the power system operation state estimation; third, the present invention proposes an action strategy suitable for the reactive compensation device inside the centralized photovoltaic power station, which effectively improves the power factor at the gateway meter, avoids the power grid company's assessment of the photovoltaic power station's power regulation electricity fee, and greatly improves the economy of the photovoltaic power station operation.

[0129] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A solution to excessive power charges in centralized photovoltaic power stations, characterized in that: The following steps are involved: Step 1: Based on the historical data obtained from the grid-connected measurement meter of the centralized photovoltaic power station and the mathematical model of the transmission line L, the monthly four-quadrant calculated active power and the monthly four-quadrant calculated reactive power of the photovoltaic power station metering gateway meter in front of the grid-connected bus G of the upper-level substation are calculated. Step 2: Using the weighted least squares method, the monthly four-quadrant calculation of active power and the monthly four-quadrant calculation of reactive power and their actual values ​​of the photovoltaic power station metering gateway table are used to calculate the estimated value of the charging power of the transmission line. Step 3: Estimated value of charging power based on transmission line The reactive power Q generated by the reactive power compensation device in the centralized photovoltaic power station is given as C , to ensure that the power adjustment fee of centralized photovoltaic power stations does not exceed the standard; the specific steps include: Real-time monitoring of the size and direction of the active power Ps sent by the centralized photovoltaic power station. Once Ps>0 and is lower than the set threshold, the reactive power Q generated by the reactive power compensation device in the substation is controlled. C , so that it satisfies the following formula: That is, to ensure that the power factor of the photovoltaic power station metering gateway meets the requirements of the power grid company, so that the power adjustment fee of the centralized photovoltaic power station does not exceed the standard; When Ps<0, no requirements are made on the reactive power compensation device.

2. The solution to excessive power charges in centralized photovoltaic power plants according to claim 1 is characterized in that: The specific steps of step 1 include: Step 1.1: Assume that the grid-connected meter uses Δt as the sampling interval to measure the power P delivered by the centralized photovoltaic power station. S +jQ S Sampling and storage, where: P S and Q S are the active power and reactive power delivered by the centralized photovoltaic power station respectively; assuming that the positive direction of power is from the centralized photovoltaic power station to the upper substation, then according to the measured Ps and Q S The power flowing out of the photovoltaic power generation system grid-connected bus S is divided into four quadrants, among which: in the first quadrant, Ps>0, Q S >0 is established; in the second quadrant, Ps<0, Q S >0 is true; in the third quadrant, Ps<0, QS<0 is true; in the fourth quadrant, Ps>0, Q S <0 holds true; Step 1.2: Let Δt be the sampling time interval of the grid-connected meter, and according to Ps and Q S In the direction of , the number of duration periods in the four quadrants in the i-th month is counted as T1, T2, T3 and T4 respectively; Assume that in the first quadrant period t in the i-th month, the active power and reactive power delivered by the centralized photovoltaic power station are and Based on the mathematical model of the transmission line L, the monthly first quadrant calculated active power and monthly first quadrant calculated reactive power of the photovoltaic power station metering gateway in the i-th month are calculated by calculation. The specific expressions are as follows: in: and They are respectively the monthly first quadrant calculated active power and monthly first quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the first quadrant period t in the i-th month; is the current delivered by the centralized photovoltaic power station in the first quadrant during period t in month i; R L , X L and Q LC are the resistance, reactance and charging power to the ground of the transmission line L, which are regarded as constants; Similarly, similar methods are used to obtain the monthly calculated active power and monthly calculated reactive power of other quadrants in the ith month of the photovoltaic power station metering gateway table. The calculation formulas are as follows: in: and They are respectively the monthly second quadrant calculated active power and monthly second quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the second quadrant period t in the i-th month; is the current delivered by the centralized photovoltaic power station in the second quadrant during period t in month i; in: and They are respectively the monthly third quadrant calculated active power and the monthly third quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the third quadrant period t in the i-th month; is the current delivered by the centralized photovoltaic power station in the third quadrant period t in the i-th month; in: and They are respectively the monthly fourth quadrant calculated active power and the monthly fourth quadrant calculated reactive power of the photovoltaic power station metering gateway table in the i-th month; and are the active power and reactive power delivered by the centralized photovoltaic power station in the fourth quadrant period t in the i-th month; It is the current delivered by the centralized photovoltaic power station in the fourth quadrant period t in the i-th month.

3. The solution to excessive power charges in centralized photovoltaic power stations according to claim 1 is characterized in that: The specific steps of step 2 include: set up and are the calculated active power and reactive power of the i-th month and j-th quadrant respectively, and They are the monthly settled active power and monthly settled reactive power of the power grid company in the i-th month and the j-th quadrant respectively; Step 2.1: Construct the objective function of the weighted least squares method, as shown in the following formula: Where n is the number of historical months; Solving the above optimization problem, we can get the estimated value Q′ of the charging power of the transmission line: LC . Step 2.2: Construct the objective function of the weighted least squares method, as shown in the following formula: Where n is the number of historical months. Solving the above optimization problem, we can get the estimated value Q″ of the charging power of the transmission line: LC ; Step 2.3: Based on the estimated values ​​of the transmission line charging power obtained in steps 2.1 and 2.2, further calculate the estimated value of the transmission line charging power The specific formula is as follows:

4. A system for solving the problem of excessive power regulation fees in centralized photovoltaic power plants, adopting the solution to the problem of excessive power regulation fees in centralized photovoltaic power plants as claimed in any one of claims 1 to 3, characterized in that: include: The photovoltaic power station metering gateway meter power calculation module is used to calculate the monthly four-quadrant calculated active power and the monthly four-quadrant calculated reactive power of the photovoltaic power station metering gateway meter before the upper-level substation grid-connected bus G based on the historical data obtained from the centralized photovoltaic power station grid-connected measurement meter and the mathematical model of the transmission line L; The transmission line charging power estimation calculation module is used to calculate the estimated value of the transmission line charging power by using the weighted least squares method, based on the monthly four-quadrant calculated active power and monthly four-quadrant calculated reactive power of the photovoltaic power station metering gateway meter calculated by the photovoltaic power station metering gateway meter power calculation module and their actual values. Centralized photovoltaic power station power adjustment fee module, used to estimate the charging power of the transmission line The reactive power Q generated by the reactive power compensation device in the centralized photovoltaic power station is given as C , to ensure that the electricity charges of centralized photovoltaic power stations do not exceed the standards.

5. The system for solving the problem of excessive power charges in centralized photovoltaic power stations according to claim 4 is characterized in that: The method for the centralized photovoltaic power station power adjustment electricity fee module to ensure that the centralized photovoltaic power station power adjustment electricity fee does not exceed the standard includes: Real-time monitoring of the size and direction of the active power Ps sent by the centralized photovoltaic power station. Once Ps>0 and is lower than the set threshold, the reactive power Q generated by the reactive power compensation device in the substation is controlled. C , so that it satisfies the following formula: That is, to ensure that the power factor of the photovoltaic power station metering gateway meets the requirements of the power grid company, so that the power adjustment fee of the centralized photovoltaic power station does not exceed the standard; When Ps<0, no requirements are made on the reactive power compensation device.

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