A method for improving power factor of users connected to distributed photovoltaics

Abstract

The present invention proposes a method for improving the power factor of users connected to distributed photovoltaics, comprising the following steps: real-time monitoring of the active power and reactive power of the mains load on the user side, the reactive power provided by the reactive compensation device, the active power and reactive power provided by the photovoltaic power generation device, and the active power and reactive power in the user's actual power load. When the power factor of the mains load on the user side does not meet the assessment index of the power supply department, the energy management system sends a control instruction to the reactive compensation device and the photovoltaic power generation device installed on the user side, and controls the photovoltaic power generation device and the reactive compensation device to output corresponding reactive power according to the maximum reactive power that the reactive compensation device can provide and the assessment index, so as to meet the assessment index. This method has a low investment cost and can fundamentally solve the problem of abnormal power factor on the user side under distributed power supply access, and the reactive compensation device will no longer malfunction.

Description

Technical Field

[0001] The invention relates to the technical field of improving power factor in an electric power system, and in particular to a method for improving power factor of a user connected to distributed photovoltaics. Background Art

[0002] Figure 1 (a) is a schematic diagram of the four quadrants of electric energy. The input active power is the power grid supplying electricity to the user; the output active power is the power supplying electricity to the grid by the user; the input reactive power is the reactive power supplied by the grid to the user; and the output reactive power is the reactive power supplied by the user to the grid. For traditional power users, they are generally resistive and inductive loads, that is, in the first quadrant of electric energy, the grid inputs active power to the user and reactive power. The gateway metering point of the power grid company is usually set on the 10kV high-voltage side of the user, and the power factor assessment index is 0.9 (leading or lagging). Since the reactive compensation device of the power user is installed on the low-voltage side (user side), and the sampling point is set below the low-voltage bus circuit breaker, the reactive compensation device cannot sense the reactive power consumed by the transformer. Therefore, the adjustment standard of the power factor on the low-voltage side must be higher than 0.9 (leading or lagging), and is usually set at 0.95 (leading or lagging), such as Figure 1 The shaded part in (b) is shown.

[0003] Figure 2 In the figure, S1 is the actual power load of the user, P1 and Q1 are the active power and reactive power of the power load respectively; S2 is the mains load, P2 and Q2 are the active power and reactive power provided by the mains respectively; Q3 is the reactive power provided by the reactive compensation device. The sampling point of the reactive compensation device monitors the active power P2 and reactive power Q2 of the mains on the low-voltage side. When the reactive compensation device is not installed, the user load comes from the power grid, that is, when Q3=0, S1=S2. When the user side uses electricity normally, the load is usually resistive and inductive, and COSθ1=P1 / S1=P2 / S2>0.95( Figure 2 (not shown in the figure). After the reactive power compensation equipment is installed, the active power of the user load is all derived from the power grid, while the reactive power is provided by the power grid and the reactive power compensation equipment, that is, S1=S2+jQ3, P1+jQ1=P2+j(Q2+Q3). ​​Since the sampling position of the reactive power compensation equipment is below the low-voltage bus circuit breaker, the power factor at the sampling point after compensation is consistent with the low-voltage assessment standard of the power grid. During reactive power compensation, the required reactive power is obtained through the internal calculation of the equipment through the electrical quantities such as current and voltage at the sampling point, and the switching of the capacitor group is controlled. Before and after the compensation at the sampling point, the active power at that point will not be affected, P1=P2. When the sampling point detects that the power factor COSθ1=P2 / S2 is less than 0.95 and does not meet the standard, the reactive power compensation equipment works, increases Q3, and adjusts COSθ1=P2 / S2∈[0.95,1]. This is the basic principle of reactive power compensation on the user side.

[0004] Before the distributed photovoltaic power source is connected, the sampling point of the reactive power compensation equipment monitors the active power P2 and reactive power Q2 of the low-voltage side mains. Figure 3 As shown in the figure, after the distributed power source is connected, since the access point is behind the sampling point, the monitoring data of the reactive compensation equipment is still the low-voltage mains load. When the distributed photovoltaic power source is connected, the actual power load (P1, Q1) of the plant is provided by the mains load (P2, Q2) and the photovoltaic load (P3, Q3). In order to obtain the maximum benefit of photovoltaic power generation, the power factor output by the photovoltaic inverter is usually set to 1, that is, the photovoltaic part outputs pure active power, Q3 = 0. The distributed power source shares the active power P1 in the actual load of the user, but the reactive power Q1 of the actual load still comes from the mains. At this time, the active power monitored at the sampling point of the reactive compensation equipment becomes smaller, the reactive power remains unchanged, and the power factor of the sampling point is consistent with the assessment standard of the State Grid. Therefore, compared with before the distributed power source is connected, the compensation equipment must provide more reactive power to meet the assessment requirements of the power factor.

[0005] The actual power load of users is constantly fluctuating. With the access of distributed power sources, as photovoltaic power generation continues to increase, the user-side demand for the active power P2 of the mains will decrease. Since the compensation amount of the user's original reactive compensation equipment is configured according to the power consumption of the factory, when the distributed photovoltaic power source is connected, no new capacitor group is added, but the required reactive compensation amount increases a lot compared to before the access. Even if the reactive compensation equipment is fully invested, the power factor cannot be adjusted to the assessment standard.

[0006] If the reactive power compensation equipment does not have the four-quadrant reactive power compensation function, when the photovoltaic power generation is in excess, the mains will convert the input active power and input reactive power into output active power and input reactive power, and the reactive power compensation equipment will exit and not operate. At this time, the power factor measured by the mains is a negative value, and the mains must provide all reactive power to the user, Q1 = Q2, and the power factor is difficult to reach the assessment standard of [-1, -0.95].

[0007] To solve the problem of abnormal power factor on the user side under distributed photovoltaic access, there are several engineering solutions as follows.

[0008] (1) The access point of the photovoltaic system is moved to the front end of the reactive power compensation sampling point

[0009] This is the most commonly used solution in engineering design. The access point of the photovoltaic system is moved to the front end of the reactive power compensation point. The reactive power compensation equipment sampling point monitors the sum of the mains load (P1, Q2) and the photovoltaic load P3, that is, the actual power load value of the user (P1, Q1). Regardless of whether the photovoltaic power generation power can be fully absorbed by the user, the load direction monitored at the reactive power compensation equipment sampling point will not change, and it will always be in the state of inputting active power and inputting reactive power. Figure 4 As shown in the figure, when the photovoltaic system generates less power, the user consumes it normally. The reactive power compensation device makes reactive power compensation for the power load (P1, Q1), the compensation amount is Q4, and the power factor at the sampling point reaches 0.95. However, after the photovoltaic access point is moved forward, the power factor at the sampling point of the reactive power compensation device does not correspond to the power factor of the low-voltage assessment of the mains. That is, the power factor at the sampling point of the reactive power compensation device meets the requirement of 0.95, but the actual power factor at the mains is less than 0.95. The greater the photovoltaic power generation, the lower the actual power factor of the mains will be, and it cannot be compensated by the reactive power compensation device. When the user does not consume enough and the photovoltaic reverses the power, the reactive power compensation device operates normally and can adjust the power factor at its sampling point to -0.95. However, since the power factor at the sampling point is not equal to the mains power factor at this time, it may not meet the assessment requirements. In summary, moving the access point of the photovoltaic system to the front of the reactive power compensation sampling point does not fundamentally solve the problem of the mains power factor not meeting the standard. This method solves the problem of frequent switching on or off of reactive compensation equipment, and the power factor dial reading on the equipment will also fluctuate normally between 0.95 and 1.

[0010] (2) Add a set of sampling CT in the photovoltaic grid-connected cabinet and connect it to the reactive power compensation equipment together with the original sampling CT.

[0011] The principle of this processing method is the same as that of moving the access point forward. The reactive power compensation equipment ultimately still performs reactive power compensation based on the actual power load (P1, Q1), and cannot solve the problem of the AC power factor not meeting the standard.

[0012] (3) Set the power factor of the photovoltaic inverter output and the reactive power output of the photovoltaic system

[0013] By adjusting the power factor of the photovoltaic inverter output, the photovoltaic system can output reactive power, but the compensation amount of the reactive compensation device does not change before and after the photovoltaic connection, and the power factor at the sampling point of the reactive compensation device is the mains power factor. Similar to this solution, a reactive compensation device is connected in parallel on the photovoltaic side to perform reactive power compensation on the photovoltaic system. However, this method does not solve the problem of frequent switching on or off of reactive compensation equipment. When the photovoltaic output is large and the power is reversed, the reactive compensation device will still not work.

[0014] (4) Replace equipment with four-quadrant reactive power compensation function

[0015] This method can fundamentally solve the problems of abnormal operation of reactive power compensation equipment and substandard mains power factor, but the cost of equipment replacement is expensive and is generally not used in engineering design. Summary of the invention

[0016] The technical problem to be solved by the present invention is that after the photovoltaic power generation source is installed on the user side, the power factor of the mains load cannot meet the assessment index of the power supply department, and the solution in the background technology cannot fundamentally solve the problem of the mains power factor not meeting the standard, or the equipment cost is too high and is not suitable for application. In order to solve this technical problem, the present invention proposes a method for improving the power factor of users connected to distributed photovoltaics, comprising the following steps:

[0017] S1, real-time monitoring of the active power and reactive power of the user-side mains load, the reactive power provided by the reactive compensation equipment, the active power and reactive power provided by the photovoltaic power generation device, and the active power and reactive power in the user's actual power load;

[0018] S2, when the power factor of the mains load on the user side does not meet the assessment index of the power supply department, the energy management system sends control instructions to the reactive compensation equipment and photovoltaic power generation device installed on the user side, and controls the photovoltaic power generation device and the reactive compensation equipment to output corresponding reactive power according to the maximum reactive power that the reactive compensation equipment can provide and the assessment index, so as to meet the assessment index.

[0019] As a further improvement of the power factor improvement method for users connected to distributed photovoltaics of the present invention: Step S1 includes obtaining the active power P1 and reactive power Q1 in the actual power load of the user, as well as the active power P2 of the mains load on the user side and the active power P3 of the photovoltaic power generation on the user side, and the maximum reactive power X that the reactive compensation device can provide; wherein P1=P2+P3. Assume that the reactive power of the mains load on the user side is Q2, the reactive power of the photovoltaic power generation on the user side is Q3, and the reactive power provided by the reactive compensation device at a certain moment is Q4, wherein Q4=Q1-Q2-Q3, and Q1, Q2, Q3 and Q4 are all ≥0. Step S2 includes: the power factor of the mains load on the user side is

[0020]

[0021] Assuming that the assessment index of the power factor cosθ of the user-side mains load is |cosθ|≥A, then

[0022]

[0023] Since Q4≤X, Q1-Q2-Q3≤X, the reactive power of photovoltaic power generation is controlled as follows:

[0024]

[0025] The power factor of the mains load is such that the absolute value of cosθ reaches above A, meeting the assessment index.

[0026] As a further improvement of the method for improving the power factor of users connected to distributed photovoltaic power generation according to the present invention: the assessment index A of the power factor of the user-side mains load is 0.95, then

[0027]

[0028]

[0029] The reactive power of photovoltaic power generation is controlled to Q3 through the energy management system, so that inequality (I) holds true, and the power factor of the mains load can be the absolute value of cosθ ≥ 0.95, meeting the assessment indicators.

[0030] As a further improvement of the method for improving the power factor of users connected to distributed photovoltaic power generation of the present invention: assuming that the power factor of photovoltaic power generation is Y, then

[0031]

[0032] Under the premise of satisfying inequality (I), the photovoltaic power generation device is controlled to output power at Y = A = 0.95, then

[0033]

[0034] Since Q4 = Q1-Q2-Q3, when Q2 reaches its maximum value, Q4 reaches its minimum value. Control Q4 not less than its minimum value, that is, control Then the power factor of the mains load meets the assessment indicators.

[0035] As a further improvement of the power factor improvement method for users connected to distributed photovoltaics of the present invention: an energy management system is used to monitor the active power P1 and reactive power Q1 in the user's actual power load, as well as to monitor the active power P2 and photovoltaic power generation power P3 of the mains load, and to obtain the maximum reactive power X that the reactive compensation equipment can provide.

[0036] As a further improvement of the method for improving the power factor of users connected to distributed photovoltaics of the present invention: the energy management system can start the reactive power compensation device to provide reactive power when the photovoltaic power generation at the user end feeds power back to the power grid.

[0037] As a further improvement of the method for improving the power factor of a user connected to distributed photovoltaic power generation according to the present invention, the method specifically comprises the following steps:

[0038] First, obtain the active power P1 and reactive power Q1 of the user's actual power load, as well as the active power P2 of the user-side mains load and the active power P3 of the user-side photovoltaic power generation; the assessment index A of the power factor of the user-side mains load is 0.95;

[0039] Determine whether the active power P2 of the user-side mains load is input or output. When the active power is input, P2>0, and when the active power is output, P2<0;

[0040] If P2>0, it is further determined whether the power factor cosθ of the mains load is ≥0.95. If so, no action is taken. Otherwise, with the goal of controlling cosθ≥0.95, the energy management system is first used to start the reactive compensation device to output the maximum reactive power X. Then the energy management system also issues a control instruction to control the photovoltaic inverter in the photovoltaic power generation device to output power with a power factor of 0.95 to obtain the value of Q3. Then the reactive compensation device refreshes the action so that the reactive power Q4 output by the reactive compensation device is Q1-Q2-Q3. When cosθ=0.95, Q2 obtains the maximum value and Q4 obtains the minimum value. Q4 is controlled not to be less than its minimum value, and the power factor of the mains load meets the assessment index.

[0041] As a further improvement of the method for improving the power factor of a user connected to distributed photovoltaic power generation according to the present invention, the method further includes the following steps:

[0042] If P2<0, it means that photovoltaic power generation feeds electricity back to the power grid, the reactive compensation device itself does not act, Q4=0, and the output of the reactive compensation device is controlled by the energy management system; first, determine whether the power factor cosθ of the mains load is ≤-0.95, if so, no action is taken, otherwise, with the goal of regulating cosθ≤-0.95, first use the energy management system to start the reactive compensation device to output the maximum reactive power X, and then the energy management system also issues a control instruction to control the photovoltaic inverter in the photovoltaic power generation device to output power with a power factor of 0.95 to obtain the value of Q3, and then the reactive compensation device refreshes the action, so that the reactive power output by the reactive compensation device Q4=Q1-Q2-Q3, when cosθ=-0.95, Q2 obtains the maximum value, Q4 obtains the minimum value, and Q4 is controlled not to be less than its minimum value, then the power factor of the mains load meets the assessment index.

[0043] The beneficial effects of the present invention are as follows: control instructions are issued to the reactive power compensation equipment and photovoltaic power generation device installed on the user side through the energy management system (EMS), and the photovoltaic power generation device and the reactive power compensation device are controlled to output corresponding reactive power according to the maximum reactive power that the reactive power compensation device can provide and the assessment index, so as to achieve the assessment index. This can fundamentally solve the problem of abnormal power factor on the user side under the access of distributed power sources, and the reactive power compensation device will no longer work abnormally. At a relatively low cost, the metering assessment of the city electricity can meet the requirements, and unnecessary losses to users due to failure to meet the assessment requirements can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the four quadrants of electric energy and power factor assessment indicators in the background technology.

[0045] Figure 2 It is a traditional electric power user electrical diagram and reactive power compensation vector diagram in the background technology.

[0046] Figure 3 This is a load distribution diagram after the photovoltaic power generation system in the background technology is connected to the user side.

[0047] Figure 4 The power distribution diagram of the photovoltaic power generation system in the background technology is moved from the access point to the front end of the reactive power compensation sampling point.

[0048] Figure 5 It is a structural principle diagram of using EMS to control reactive power compensation in an implementation method.

[0049] Figure 6 Flow chart of reactive power compensation control using EMS in an implementation method. DETAILED DESCRIPTION

[0050] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0051] The traditional solution cannot perfectly solve the problem of abnormal operation of reactive power compensation equipment and non-standard power factor of mains. Therefore, the present invention proposes a comprehensive solution to the problem of abnormal operation of reactive power compensation equipment and non-standard power factor of mains, such as Figure 5 As shown, the preset target is achieved by using the energy management system (EMS) to control the reactive compensation equipment and photovoltaic inverter in real time.

[0052] A method for improving the power factor of a user connected to distributed photovoltaic power generation comprises the following steps:

[0053] S1, real-time monitoring of the active power and reactive power of the user-side mains load, the reactive power provided by the reactive compensation equipment, the active power and reactive power provided by the photovoltaic power generation device, and the active power and reactive power in the user's actual power load.

[0054] S2, when the power factor of the mains load on the user side does not meet the assessment index of the power supply department, the energy management system sends control instructions to the reactive compensation equipment and photovoltaic power generation device installed on the user side, and controls the photovoltaic power generation device and the reactive compensation equipment to output corresponding reactive power according to the maximum reactive power that the reactive compensation equipment can provide and the assessment index, so as to meet the assessment index.

[0055] Among them, step S1 includes obtaining the active power P1 and reactive power Q1 in the user's actual power load, as well as the active power P2 of the user-side mains load and the active power P3 of the user-side photovoltaic power generation, and the maximum reactive power X that the reactive compensation equipment can provide; where P1 = P2 + P3. Suppose the reactive power of the user-side mains load is Q2, the reactive power of the user-side photovoltaic power generation is Q3, and the reactive power provided by the reactive compensation equipment at a certain moment is Q4, where Q4 = Q1-Q2-Q3, and Q1, Q2, Q3 and Q4 are all ≥ 0. Step S2 includes: the power factor of the user-side mains load is

[0056]

[0057] Assuming that the assessment index of the power factor cosθ of the user-side mains load is |cosθ|≥A, then

[0058]

[0059] Since Q4≤X, Q1-Q2-Q3≤X, the reactive power of photovoltaic power generation is controlled as follows:

[0060]

[0061] The power factor of the mains load is such that the absolute value of cosθ reaches above A, meeting the assessment index.

[0062] Usually, the power factor assessment index of the user-side mains load is A = 0.95, then

[0063]

[0064]

[0065] The reactive power of photovoltaic power generation is controlled to Q3 through the energy management system, so that inequality (I) holds true, and the power factor of the mains load can be the absolute value of cosθ ≥ 0.95, meeting the assessment indicators.

[0066] In the control method of the energy management system, assuming that the power factor of photovoltaic power generation is Y, then

[0067]

[0068] Under the premise of satisfying inequality (I), the photovoltaic power generation device is controlled to output power at Y = A = 0.95, then

[0069]

[0070] Since Q4 = Q1-Q2-Q3, when Q2 reaches its maximum value, Q4 reaches its minimum value. Control Q4 not less than its minimum value, that is, control Then the power factor of the mains load meets the assessment indicators.

[0071] In the method for improving the power factor of users connected to distributed photovoltaics, the energy management system can be used to monitor the active power P1 and reactive power Q1 in the actual power load of the user, as well as the active power P2 and photovoltaic power generation power P3 of the mains load, and obtain the maximum reactive power X that the reactive compensation device can provide. The energy management system EMS can also start the reactive compensation device to provide reactive power when the photovoltaic power generation at the user end feeds back power to the power grid.

[0072] Figure 6 This is a flow chart of the reactive power compensation control method using the energy management system EMS at a certain moment. The specific steps of the method for improving the power factor of users connected to distributed photovoltaics are as follows:

[0073] First, obtain the active power P1 and reactive power Q1 of the user's actual power load, as well as the active power P2 of the user-side mains load and the active power P3 of the user-side photovoltaic power generation; the assessment index A of the power factor of the user-side mains load is 0.95;

[0074] Determine whether the active power P2 of the user-side mains load is input or output. When the active power is input, P2>0, and when the active power is output, P2<0;

[0075] If P2>0, it is further determined whether the power factor cosθ of the mains load is ≥0.95. If so, no action is taken. Otherwise, with the goal of controlling cosθ≥0.95, the energy management system is first used to start the reactive compensation device to output the maximum reactive power X. Then the energy management system also issues a control instruction to control the photovoltaic inverter in the photovoltaic power generation device to output power with a power factor of 0.95 to obtain the value of Q3. Then the reactive compensation device refreshes the action so that the reactive power Q4 output by the reactive compensation device is Q1-Q2-Q3. When cosθ=0.95, Q2 obtains the maximum value and Q4 obtains the minimum value. Q4 is controlled not to be less than its minimum value, and the power factor of the mains load meets the assessment index.

[0076] If P2<0, it means that photovoltaic power generation feeds electricity back to the power grid, the reactive compensation device itself does not act, Q4=0, and the output of the reactive compensation device is controlled by the energy management system; first, determine whether the power factor cosθ of the mains load is ≤-0.95, if so, no action is taken, otherwise, with the goal of regulating cosθ≤-0.95, first use the energy management system to start the reactive compensation device to output the maximum reactive power X, and then the energy management system also issues a control instruction to control the photovoltaic inverter in the photovoltaic power generation device to output power with a power factor of 0.95 to obtain the value of Q3, and then the reactive compensation device refreshes the action, so that the reactive power output by the reactive compensation device Q4=Q1-Q2-Q3, when cosθ=-0.95, Q2 obtains the maximum value, Q4 obtains the minimum value, and Q4 is controlled not to be less than its minimum value, then the power factor of the mains load meets the assessment index.

[0077] The energy management system (EMS) issues control instructions to the reactive power compensation equipment and photovoltaic power generation device installed on the user side. According to the maximum reactive power that the reactive power compensation equipment can provide and the assessment index, the photovoltaic power generation device and the reactive power compensation equipment are controlled to output corresponding reactive power to achieve the assessment index. This can fundamentally solve the problem of abnormal power factor on the user side under distributed power supply access, and the reactive power compensation equipment will no longer work abnormally. At a relatively low cost, the metering assessment of the city electricity can meet the requirements, and unnecessary losses to users due to failure to meet the assessment requirements can be avoided.

[0078] The following is an example of a method for improving the power factor of a user connected to distributed photovoltaics in this embodiment.

[0079] Assume that a user's factory uses a 315KVA transformer, originally equipped with 80kvar reactive power compensation equipment, and now newly connected to a 300kW distributed photovoltaic power generation system. At time t1, EMS monitors the user's actual power load P1(t1) = 160kW, Q1(t1) = 120kvar, the active power of the mains P2(t1) = 30kW, the photovoltaic power generation power P3(t1) = 130kW, Q3(t1) = 0kvar. At this time, the reactive power compensation equipment performs reactive power compensation on the mains load, and at least 110.14kvar of reactive power must be compensated to make the power factor of the mains load reach 0.95. However, the reactive power compensation equipment can only provide a maximum of 80kvar of reactive power, so the reactive power provided by the mains Q2(t1) = 40kvar, and the power factor of the mains load is 0.6, which is far below the assessment standard of 0.95. According to a control method proposed in an embodiment of the present invention, the EMS issues a control instruction to control the photovoltaic inverter to output at a power factor of 0.95, that is, the photovoltaic power generation power is adjusted to P3(t1)=130kW, Q3(t1)=42.73kvar. Then the power factor of the mains load is compensated to at least 0.95, P2(t1)=30kW, Q2(t1)=9.86kvar, and the reactive power compensation device needs to provide Q4(t1)=120-42.73-9.86=67.41kvar reactive power to meet the requirement.

[0080] If at time t2, EMS monitors the user's actual power load P1(t2) = 240kW, Q1(t2) = 150kvar, the active power of the mains P2(t2) = -10kW, the photovoltaic power generation power P3(t2) = 250kW, Q3(t2) = 0kvar. At this time, photovoltaic power generation is in excess and users cannot fully absorb it. The excess power flows to the grid side. Since the reactive compensation equipment does not have a four-quadrant reactive compensation function, the active power at its sampling point is reversed and the equipment does not operate. Using the control method of the embodiment of the present invention, in order to compensate the power factor of the mains load to -0.95, P2(t2) = -10kW, then Q2(t2) = 3.29kvar, the reactive compensation equipment needs to provide a reactive power of 150-3.29 = 146.71kvar, which is obviously impossible for the reactive compensation equipment to provide. The power factor of the mains load does not meet the assessment requirements. At this time, the EMS issues a control command to control the photovoltaic inverter to output at a power factor of 0.95, that is, the photovoltaic power generation power is P3(t2)=250kW, Q3(t2)=82.17kvar. In the case of photovoltaic output reactive power, the reactive compensation equipment only needs to provide Q4(t2)=150﹣3.29﹣82.17=64.54kvar to make the power factor of the mains load meet the assessment standards.

[0081] Through the EMS reactive power compensation control of this solution, the problem of abnormal power factor on the user side under the access of distributed power sources has been fundamentally solved, and the reactive power compensation equipment will no longer malfunction. The application of this solution is low-cost and the metering and assessment of the city electricity meets the requirements, so as to avoid unnecessary losses to customers or owners.

[0082] The above specific embodiments are only exemplary, and are intended to enable those skilled in the art to better understand the present invention, and should not be construed as limiting the scope of protection claimed by the present invention. Any equivalent changes or modifications made based on the spirit disclosed by the present invention should fall within the scope of protection claimed by the present invention.

Claims

1. A method for improving the power factor of a user connected to distributed photovoltaic power generation, characterized in that: The following steps are involved: S1, real-time monitoring of the active power and reactive power of the user-side mains load, the reactive power provided by the reactive compensation equipment, the active power and reactive power provided by the photovoltaic power generation device, and the active power and reactive power in the user's actual power load; S2, when the power factor of the mains load on the user side does not reach the assessment index of the power supply department, the energy management system issues a control instruction to the reactive power compensation equipment and photovoltaic power generation device installed on the user side, and controls the photovoltaic power generation device and the reactive power compensation equipment to output corresponding reactive power according to the maximum reactive power that the reactive power compensation equipment can provide and the assessment index, so as to reach the assessment index; Step S1 includes: obtaining the active power P1 and reactive power Q1 of the user's actual power load, the active power P2 of the user-side mains load and the active power P3 of the user-side photovoltaic power generation, and the maximum reactive power X that the reactive compensation device can provide; wherein P1 = P2 + P3; Assume that the reactive power of the fixed mains load on the user side is Q2, the reactive power of the photovoltaic power generation on the user side is Q3, and the reactive power provided by the reactive compensation device at a certain moment is Q4, where Q4 = Q1-Q2-Q3, and Q1, Q2, Q3 and Q4 are all ≥ 0; Step S2 includes: the power factor of the user-side mains load is Assuming that the assessment index of the power factor cosθ of the user-side mains load is |cosθ|≥A, then Since Q4≤X, Q1-Q2-Q3≤X, the reactive power of photovoltaic power generation is controlled as follows: The power factor of the mains load is the absolute value of cosθ reaching A or above, meeting the assessment index; the assessment index of the power factor of the mains load on the user side is A = 0.95, then The reactive power of photovoltaic power generation is controlled by the energy management system to be Q3, so that inequality (I) holds true, and the power factor of the mains load can be the absolute value of cosθ ≥ 0.95, meeting the assessment index; assuming that the power factor of photovoltaic power generation is Y, then Under the premise of satisfying inequality (I), the photovoltaic power generation device is controlled to output power at Y = A = 0.95, then Since Q4 = Q1-Q2-Q3, when Q2 reaches its maximum value, Q4 reaches its minimum value. Control Q4 not less than its minimum value, that is, control Then the power factor of the mains load meets the assessment indicators.

2. The method for improving the power factor of a user connected to distributed photovoltaic power generation according to claim 1, characterized in that: The energy management system is used to monitor the active power P1 and reactive power Q1 in the user's actual power load, as well as the active power P2 and photovoltaic power generation power P3 of the mains load, and to obtain the maximum reactive power X that the reactive compensation equipment can provide.

3. The method for improving the power factor of a user connected to distributed photovoltaic power generation according to claim 1, characterized in that: The energy management system can start the reactive power compensation device to provide reactive power when the photovoltaic power generation at the user end feeds back power to the power grid.

4. The method for improving the power factor of a user connected to distributed photovoltaic power generation according to claim 3, characterized in that: The specific steps include: First, obtain the active power P1 and reactive power Q1 of the user's actual power load, as well as the active power P2 of the user-side mains load and the active power P3 of the user-side photovoltaic power generation; the assessment index A of the power factor of the user-side mains load is 0.95; Determine whether the active power P2 of the user-side mains load is input or output. When the active power is input, P2>0, and when the active power is output, P2<0; If P2>0, then further determine whether the power factor cosθ of the mains load is ≥0.

95. If yes, no action is taken. Otherwise, cosθ is adjusted. ≥ 0.95 is the target. First, the energy management system is used to start the reactive power compensation device to output the maximum reactive power X. Then, the energy management system also issues a control instruction to control the photovoltaic inverter in the photovoltaic power generation device to output power with a power factor of 0.95 to obtain the value of Q3. Then, the reactive power compensation device refreshes the action so that the reactive power output by the reactive power compensation device is Q4=Q1-Q2-Q3. When cosθ=0.95, Q2 obtains the maximum value and Q4 obtains the minimum value. Q4 is controlled not to be less than its minimum value, and the power factor of the mains load meets the assessment index.

5. The method for improving the power factor of a user connected to distributed photovoltaic power generation according to claim 4, characterized in that: The following steps are also included: If P2<0, the photovoltaic power generation is feeding back the power grid, the reactive power compensation device itself does not work, Q4=0, and the output of the reactive power compensation device is controlled by the energy management system; first determine whether the power factor cosθ of the mains load is ≤-0.95, if yes, no action is taken, otherwise, cosθ is regulated. ≤ -0.95 is the target. First, the energy management system is used to start the reactive compensation device to output the maximum reactive power X. Then, the energy management system also issues a control instruction to control the photovoltaic inverter in the photovoltaic power generation device to output power with a power factor of 0.95 to obtain the value of Q3. Then, the reactive compensation device refreshes the action so that the reactive power Q4 output by the reactive compensation device is Q1-Q2-Q3. When cosθ=-0.95, Q2 obtains the maximum value and Q4 obtains the minimum value. Q4 is controlled not to be less than its minimum value, and the power factor of the mains load meets the assessment index.

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