A method for distributed photovoltaic reactive power compensation

Abstract

The invention discloses a method for distributed photovoltaic reactive power compensation, which belongs to the field of photovoltaics, and the method steps are as follows: S1, investigate the capacitance capacity Q of the capacitor cabinet before the factory; S2, connect the intelligent composite switch in series with each group of capacitors; S3, reliably connect the intelligent composite switch with the four-quadrant functional reactive controller, and realize the automatic adjustment of the four-quadrant functional reactive controller and 18 groups of capacitors; S4, calculate the reactive power compensation capability range value Qi that the photovoltaic inverter can provide; S5, after the four-quadrant functional reactive controller detects the power factor of the second bus, it completes the primary adjustment; S6, when the AVC system detects that the power factor of the first bus meets the standard value, it does not issue instructions to each group of photovoltaic inverters; S7, when the AVC system detects that the standard value is not met, the secondary adjustment of the power factor of the factory is realized. The invention improves the utilization rate of distributed power generation and improves the profit of power generation operation; it has an alarm reminder function, avoids the waste of effective resources, and saves the investment of funds.

Description

Technical Field

[0001] The invention relates to the field of photovoltaics, and in particular to a method for distributed photovoltaic reactive power compensation. Background Art

[0002] With the rapid development of new energy, the installed capacity of distributed photovoltaics has increased year by year and has become the mainstream in recent years. It has the characteristics of adapting to local conditions, decentralized layout, local consumption, and huge market potential. Large factories generally install rooftop distributed photovoltaics, adopting the "self-generation and self-use, surplus power to the grid" operation mode. The reactive power compensation device is an important equipment for the normal operation of factory equipment. Before the distributed photovoltaics are connected to the grid, the reactive power compensation equipment of the factory meets the power factor 0.9 assessment index value. When the distributed photovoltaics are connected to the grid and in the power generation period, the power factor of the factory is lower than 0.9. The main reasons for this phenomenon are as follows: First, when the factory's distributed photovoltaics are in the power generation state, active power is provided to the factory, reducing the 10kV power grid's downstream active power to the factory, and even there is a phenomenon of the factory sending active power back to the 10kV power grid. Because the original controller of the factory's reactive power compensation does not have the power direction judgment defect, that is, the four-quadrant automatic identification function, once the power backflow occurs, the power factor cannot be accurately measured, resulting in the automatic exit of the reactive power compensation equipment, thereby reducing the power factor. Second, the factory basically has multiple step-down transformers and is equipped with a corresponding number of low-voltage reactive compensation devices. The reactive compensation controllers are all installed in the low-voltage 0.38kV distribution room, and the power factor on the 0.38kV bus is tracked, but the power factor at the 10kV distribution network assessment point is not followed up in real time. At the same time, the step-down transformer itself consumes a certain amount of reactive power, which causes a decrease in the power factor. Third, the distributed photovoltaic inverter itself has the ability to dispatch reactive power, but each inverter is currently in an independent fixed operation mode, and there is a lack of a centralized management system to regulate the photovoltaic inverter. Summary of the invention

[0003] With regard to the above problems existing in the prior art, the purpose of the present invention is to provide a method for distributed photovoltaic reactive power compensation to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A method for distributed photovoltaic reactive power compensation, the method steps are as follows:

[0006] S1. Investigate the capacitance Q of each low-voltage 0.38kV power distribution room capacitor cabinet in the factory before the distributed photovoltaic reactive power compensation system is installed;

[0007] S2. According to the capacitance Q of each low-voltage 0.38kV power distribution room capacitor cabinet in step S1, 18 groups are configured according to X kVar and 2X kVar, and each group of capacitors is connected in series with an intelligent composite switch having the functions of no harmonic injection, low power consumption, and no contact sintering;

[0008] The calculation formula is as follows: Q = n1 (X kVar) + n2 (2X kVar), n1 + n2 = 18, X represents the capacitance value, n1 and n2 represent the number of capacitors;

[0009] S3. Reliably connect the intelligent composite switch of the capacitor cabinet in the low-voltage 0.38kV distribution room with the four-quadrant functional reactive controller to achieve automatic adjustment of the four-quadrant functional reactive controller and 18 groups of capacitors;

[0010] S4. According to the power factor adjustment range of the photovoltaic inverter (inductive 0.85 ~ capacitive 0.85) and the photovoltaic inverter capacity Si, calculate the reactive power compensation capacity range Qi that the photovoltaic inverter can provide, that is, -Si*(1-0.85 2 )≤Qi≤Si*(1-0.85 2 );

[0011] S5, after the four-quadrant functional reactive controller detects the power factor of the second bus, the four-quadrant functional controller completes the automatic switching of 18 groups of capacitors and completes the primary regulation of the power factor reactive power of each power distribution room in the factory;

[0012] S6. When the AVC system detects that the power factor of the first bus meets the power factor assessment index value of the power grid, it does not issue instructions to each group of photovoltaic inverters to ensure that each group of photovoltaic inverters generates full active power;

[0013] S7. When the AVC system detects that the power factor of the first bus does not meet the grid power factor assessment index value, and monitors that each group of four-quadrant functional reactive controllers are in the deployment state, the AVC system sends adjustment instructions to each group of photovoltaic inverters to adjust the reactive power size and direction of each group of photovoltaic inverters, thereby realizing secondary adjustment of the factory power factor and making 10kV meet the grid power factor assessment index value.

[0014] As a further solution of the present invention: the distributed photovoltaic reactive power compensation system includes a photovoltaic reactive power compensation module and an AVC system.

[0015] As a further solution of the present invention: the AVC system is connected to the first bus, and the first bus is connected to the distributed photovoltaic grid-connected cable through the first bus current transformer CT and the switch; a voltage transformer PT is installed on the first bus; a plurality of photovoltaic reactive compensation modules are provided, and the plurality of photovoltaic reactive compensation modules are connected to the first bus.

[0016] As a further solution of the present invention: the photovoltaic reactive power compensation module is internally provided with a transformer, a current transformer CT, a photovoltaic inverter group, a photovoltaic component, a capacitor component and a reactive power controller;

[0017] The high voltage side of the transformer is connected to the first busbar, the low voltage side of the transformer is connected to one end of the current transformer CT, and the other end of the current transformer CT is connected to the second busbar;

[0018] The photovoltaic inverter group is connected to the second busbar, and a plurality of photovoltaic inverters are arranged inside the photovoltaic inverter group, and each photovoltaic inverter is connected to a photovoltaic module respectively;

[0019] One end of the capacitor assembly is connected to the second busbar, and the other end of the capacitor assembly is connected to the reactive power controller through a contactor;

[0020] The first busbar is connected to the factory load.

[0021] As a further solution of the present invention: the reactive power controller is a reactive power controller with four-quadrant function.

[0022] As a further solution of the present invention: the first busbar is a 10kV busbar.

[0023] As a further solution of the present invention: the second busbar is a 0.38kV busbar

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention adjusts reactive power through a four-quadrant functional reactive controller, and does not adjust each group of photovoltaic inverters after meeting the grid-connected power factor, thereby improving the utilization rate of each group of distributed power generation and the operating profit of distributed photovoltaic power generation; the AVC system directly monitors the 10kV bus grid-connected power factor, and grasps in real time whether it is assessed by the power grid; and increases the alarm reminder function when the AVC system monitors that the 10kV power factor is lower than the grid assessment index value. The present invention makes full use of the original capacitor bank, avoids the waste of effective resources, and saves capital investment compared to the SVG reactive compensation device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A system framework diagram of a distributed photovoltaic reactive power compensation method is disclosed as an embodiment. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", and "connected" should be understood in a broad sense; for example, it can be a fixed connection, a detachable connection, or an integral connection, a mechanical connection, or an electrical connection, a direct connection, or an indirect connection through an intermediate medium, or the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] See also Figure 1 , a distributed photovoltaic reactive power compensation method, wherein the distributed photovoltaic reactive power compensation system includes a photovoltaic reactive power compensation module and an AVC system;

[0030] The AVC system is connected to the first busbar, and the first busbar is connected to the distributed photovoltaic grid-connected cable through the first busbar current transformer CT and the switch; the first busbar is equipped with a voltage transformer PT; there are multiple groups of photovoltaic reactive power compensation modules, and the multiple groups of photovoltaic reactive power compensation modules are connected to the first busbar;

[0031] The photovoltaic reactive power compensation module is internally provided with a transformer, a current transformer CT, a photovoltaic inverter group, a photovoltaic module, a capacitor module and a reactive power controller;

[0032] The high voltage side of the transformer is connected to the first busbar, the low voltage side of the transformer is connected to one end of the current transformer CT, and the other end of the current transformer CT is connected to the second busbar, i.e., the 0.38 kV busbar;

[0033] The photovoltaic inverter group is connected to the second busbar, and a plurality of photovoltaic inverters are arranged inside the photovoltaic inverter group, and each photovoltaic inverter is connected to a photovoltaic module respectively;

[0034] One end of the capacitor assembly is connected to the second busbar, and the other end of the capacitor assembly is connected to the reactive power controller through a contactor;

[0035] The first busbar is connected to the factory load;

[0036] The reactive power controller is a reactive power controller with four-quadrant function.

[0037] The first busbar is a 10kV busbar. The second busbar is a 0.38kV busbar.

[0038] The current of the reactive controller is taken from the secondary current of the current transformer CT on the low-voltage side of the transformer, and the voltage of the reactive controller is taken from the voltage on the second bus. Pay attention to the polarity to ensure that the reactive power direction of the reactive controller on the 0.38kV side is consistent.

[0039] The current of the AVC system is taken from the secondary current of the 10kV first bus current transformer CT, and the voltage is taken from the secondary voltage of the 10kV first bus voltage transformer PT.

[0040] Through a dedicated communication network line, combined with the communication protocols of the four-quadrant reactive power controller and photovoltaic inverter, reliable communication can be achieved with the AVC system, and the power factor (reactive output) of the controllable photovoltaic inverter of the AVC system can be realized, and the AVC system can automatically read the reactive power adjustment status of the four-quadrant reactive power controller, and increase the alarm reminder function when the power factor of the AVC system is lower than the assessment value.

[0041] The four-quadrant functional reactive controller is used to preferentially adjust the reactive power of the 0.38kV bus, i.e., the second bus, to try to meet the power factor of 0.9 or above, and realize the first adjustment of the power factor of the factory. The AVC system detects the power factor of the 10kV bus, i.e., the first bus. When the AVC system detects that the power factor meets the power factor assessment index value of the power grid, the AVC system does not issue an adjustment command to the photovoltaic inverter to ensure that the photovoltaic inverter generates full active power. When the AVC system detects that the power factor does not meet the power factor assessment index value of the power grid, the AVC system automatically alerts the alarm to remind the on-duty personnel of the factory centralized control center to pay attention, and after monitoring that each group of four-quadrant functional reactive controllers are in the deployment state, the AVC system issues an adjustment command to the photovoltaic inverter to adjust the reactive power size and direction of the photovoltaic inverter, and realizes the secondary adjustment of the power factor of the factory to meet the power factor assessment index value of the power grid.

[0042] The method and steps for distributed photovoltaic reactive power compensation are as follows:

[0043] S1. Investigate the capacitance Q of each low-voltage 0.38kV power distribution room capacitor cabinet in the factory before the distributed photovoltaic reactive power compensation system is installed;

[0044] S2, according to the capacitance Q of each low voltage 0.38kV power distribution room capacitor cabinet in step S1, they are combined and configured into 18 groups according to X kVar and 2X kVar, and each group of capacitors is connected in series with an intelligent composite switch having the functions of no harmonic injection, low power consumption, and no contact sintering;

[0045] The calculation formula is as follows: Q = n1 (X kVar) + n2 (2X kVar), n1 + n2 = 18, X represents the capacitance value, n1 and n2 represent the number of capacitors;

[0046] S3. Reliably connect the intelligent composite switch of the capacitor cabinet in the low-voltage 0.38kV distribution room with the four-quadrant functional reactive controller to achieve automatic adjustment of the four-quadrant functional reactive controller and 18 groups of capacitors;

[0047] S4. According to the power factor adjustment range of the photovoltaic inverter (inductive 0.85 ~ capacitive 0.85) and the photovoltaic inverter capacity Si, calculate the reactive power compensation capacity range Qi that the photovoltaic inverter can provide, that is, -Si*(1-0.85 2 )≤Qi≤Si*(1-0.85 2 );

[0048] S5, after the four-quadrant functional reactive controller detects the power factor of the second bus, the four-quadrant functional controller completes the automatic switching of 18 groups of capacitors and completes the primary regulation of the power factor reactive power of each power distribution room in the factory;

[0049] S6. When the AVC system detects that the power factor of the 10kV bus meets the power factor assessment index value of the power grid, it will not issue instructions to each group of photovoltaic inverters to ensure that each group of photovoltaic inverters generates full active power;

[0050] S7. When the AVC system detects that the power factor of the 10kV bus does not meet the grid power factor assessment index value, and monitors that each group of four-quadrant functional reactive controllers are in the deployment state, the AVC system sends an adjustment instruction to each group of photovoltaic inverters to adjust the reactive power size and direction of each group of photovoltaic inverters, thereby realizing secondary adjustment of the factory power factor and making 10kV meet the grid power factor assessment index value.

[0051] The present invention preferentially adjusts the reactive power of the four-quadrant functional reactive controller of the capacitor cabinet in the low-voltage 0.38kV distribution room, and does not adjust each group of photovoltaic inverters after meeting the grid-connected power factor, thereby improving the utilization rate of each group of distributed power generation and improving the operating profit of distributed photovoltaic power generation;

[0052] The AVC system of the present invention directly monitors the 10kV bus grid-connected power factor, and grasps in real time whether it is assessed by the power grid; an alarm reminder function is added when the AVC system monitors that the 10kV power factor is lower than the power grid assessment index value.

[0053] The present invention renovates the original low-voltage 0.38kV power distribution room capacitor cabinet and updates the four-quadrant functional reactive controller, fully utilizes the original capacitor bank, avoids the waste of effective resources, and saves capital investment compared with the SVG reactive compensation device.

[0054] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive from any point of view. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention, and any reference numerals in the claims should not be considered as limiting the claims involved.

[0055] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for distributed photovoltaic reactive power compensation, characterized in that: The method steps are as follows: S1. Investigate the capacitance Q of each low-voltage 0.38kV power distribution room capacitor cabinet in the factory before the distributed photovoltaic reactive power compensation system is installed; S2. According to the capacitance Q of each low-voltage 0.38kV power distribution room capacitor cabinet in step S1, 18 groups are configured according to X kVar and 2X kVar, and each group of capacitors is connected in series with an intelligent composite switch having the functions of no harmonic injection, low power consumption, and no contact sintering; The calculation formula is as follows: Q = n1 (X kVar) + n2 (2X kVar), n1 + n2 = 18, X represents the capacitance value, n1 and n2 represent the number of capacitors; S3. Reliably connect the intelligent composite switch of the capacitor cabinet in the low-voltage 0.38kV distribution room with the four-quadrant functional reactive controller to achieve automatic adjustment of the four-quadrant functional reactive controller and 18 groups of capacitors; S4. According to the power factor adjustment range of the photovoltaic inverter (inductive 0.85 ~ capacitive 0.85) and the photovoltaic inverter capacity Si, calculate the reactive power compensation capacity range Qi that the photovoltaic inverter can provide, that is, -Si*(1-0.85 2 )≤Qi≤Si*(1-0.85 2 ); S5, after the four-quadrant functional reactive controller detects the power factor of the second bus, the four-quadrant functional controller completes the automatic switching of 18 groups of capacitors and completes the primary regulation of the power factor reactive power of each power distribution room in the factory; S6. When the AVC system detects that the power factor of the first bus meets the power factor assessment index value of the power grid, it does not issue instructions to each group of photovoltaic inverters to ensure that each group of photovoltaic inverters generates full active power; S7. When the AVC system detects that the power factor of the first bus does not meet the grid power factor assessment index value, and monitors that each group of four-quadrant functional reactive controllers are in the deployment state, the AVC system sends adjustment instructions to each group of photovoltaic inverters to adjust the reactive power size and direction of each group of photovoltaic inverters, thereby realizing secondary adjustment of the factory power factor and making 10kV meet the grid power factor assessment index value.

2. A distributed photovoltaic reactive power compensation method according to claim 1, characterized in that: The distributed photovoltaic reactive power compensation system comprises a photovoltaic reactive power compensation module and an AVC system.

3. A distributed photovoltaic reactive power compensation method according to claim 2, characterized in that: The AVC system is connected to the first bus, and the first bus is connected to the distributed photovoltaic grid-connected cable through the first bus current transformer CT and the switch; the first bus is installed with a voltage transformer PT; a plurality of photovoltaic reactive compensation modules are provided, and the plurality of photovoltaic reactive compensation modules are connected to the first bus.

4. A distributed photovoltaic reactive power compensation method according to claim 3, characterized in that: The photovoltaic reactive power compensation module is internally provided with a transformer, a current transformer CT, a photovoltaic inverter group, a photovoltaic module, a capacitor module and a four-quadrant functional reactive power controller; The high voltage side of the transformer is connected to the first busbar, the low voltage side of the transformer is connected to one end of the current transformer CT, and the other end of the current transformer CT is connected to the second busbar; The photovoltaic inverter group is connected to the second busbar, and a plurality of photovoltaic inverters are arranged inside the photovoltaic inverter group, and each photovoltaic inverter is connected to a photovoltaic module respectively; One end of the capacitor assembly is connected to the second busbar, and the other end of the capacitor assembly is connected to the four-quadrant functional reactive controller through a contactor; The first busbar is connected to the factory load.

5. A distributed photovoltaic reactive power compensation method according to claim 4, characterized in that: The first busbar is a 10kV busbar.

6. A distributed photovoltaic reactive power compensation method according to claim 5, characterized in that: The second busbar is a 0.38kV busbar.

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