Photovoltaic power station power grid system and harmonic suppression method thereof

Abstract

The invention relates to a photovoltaic power station power grid system and a harmonic suppression method thereof.The photovoltaic power station power grid system comprises a photovoltaic power station, the photovoltaic power station comprises a bus, a photovoltaic power generation unit and a reactive power compensation device, the photovoltaic power generation unit comprises a plurality of array photovoltaic power generation modules connected to the bus, and the reactive power compensation device is connected to one of the photovoltaic power generation modules; each photovoltaic power generation module comprises a current collection wire, a circuit breaker and a power generation loop, the power generation loop is connected to the bus through the current collection wire, and the circuit breaker is used for controlling the on-off of the current collection wire; the power transmission unit is connected with a total power supply grid, and the output end of the bus is connected to the power transmission unit; the harmonic monitoring unit comprises at least one harmonic monitoring device for monitoring a harmonic source; the system further comprises a harmonic suppression unit. The harmonic suppression and treatment of the photovoltaic power station can be realized, the damage of the harmonic to the power grid is reduced, the quality of the output electric energy is improved, and the stability of the power grid is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of harmonic control, and in particular to a photovoltaic power station power grid system and a harmonic control method thereof. Background Art

[0002] Harmonics refer to currents with frequencies that are integer multiples of the fundamental wave. They are divided into odd harmonics, component harmonics, and even harmonics. Harmonics with rated frequencies that are non-integer multiples of the fundamental wave are component harmonics, and harmonics with rated frequencies that are odd multiples of the fundamental wave are odd harmonics. Harmonics in the power supply grid come from harmonic sources, some of which come from the power supply system, and some are generated by nonlinear devices within the system.

[0003] In actual working process, harmonics will cause many hazards. For example, the frequency of fundamental wave is lower than that of harmonic current. Due to the skin effect and proximity effect, the transmission capacity of the line will be reduced, polluting the public power grid. Furthermore, the impact of harmonics on power equipment is mainly manifested in that harmonic current will increase the eddy current loss, hysteresis loss and copper loss of the transformer, and reduce the capacity of the transformer. In addition, harmonics increase the additional loss of power equipment, and mechanical vibration is generated during resonance, causing harmonic overvoltage, accelerating equipment aging, and even damaging the equipment, reducing the service life. At the same time, harmonics will cause relay protection devices to malfunction or refuse to operate, which may cause system failure or expand the scope of failure, reducing the reliability of the power system. In addition, the harmonics in the power line will cause voltage interference to the adjacent communication lines due to electromagnetic coupling, affecting the communication quality.

[0004] In the prior art, there are integrated harmonic suppression devices for the harmonics generated when photovoltaic power stations are working, which can eliminate harmonics locally. However, the device cannot eliminate the harmonics of the entire photovoltaic power station. Therefore, it is urgent to design a harmonic control device and method for photovoltaic power stations to control the harmonics of the entire photovoltaic power station. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a photovoltaic power station power grid system and a harmonic control method thereof, which can suppress and control the harmonics of the photovoltaic power station, reduce the damage caused by the harmonics to the power grid, and thereby improve the output power quality and enhance the stability of the power grid.

[0006] In order to solve the above technical problems, the present invention provides a photovoltaic power station power grid system, comprising: A photovoltaic power station, comprising a busbar, a photovoltaic power generation unit and a reactive power compensation device, wherein the photovoltaic power generation unit comprises a plurality of array photovoltaic power generation modules connected to the busbar, and the reactive power compensation device is connected to one of the photovoltaic power generation modules, wherein each photovoltaic power generation module comprises a collector, a circuit breaker and a power generation circuit, wherein the power generation circuit is connected to the busbar through the collector, and the circuit breaker is used to control the on and off of the collector; A power transmission unit connected to the main power supply grid, wherein the output end of the busbar is connected to the power transmission unit; a harmonic monitoring unit, comprising at least one harmonic monitoring device for monitoring a harmonic source; The harmonic control unit comprises at least one LC passive filtering device, wherein at least one of the LC passive filtering devices is configured to be connected in parallel with the harmonic source, and the LC passive filtering device comprises a load switch and inductor and capacitor components connected in series with each other.

[0007] In one embodiment of the present invention, the photovoltaic power generation module also includes a first monitoring device, which is arranged on the collecting line. The first monitoring device includes a first voltage transformer and a first current transformer. The first voltage transformer is used to monitor the voltage signal of the bus, and the first current transformer is used to monitor the current signal of the bus.

[0008] In one embodiment of the present invention, the LC passive filtering device further comprises a second voltage transformer, and the second voltage transformer is used to monitor the voltage signal of the LC passive filtering device.

[0009] In one embodiment of the present invention, the transmission unit includes a transmission line and a boosting device, the boosting device is installed on the transmission line to boost the output voltage of the photovoltaic power station, the output end of the transmission line is connected to the main power supply grid, and the other end of the transmission line is connected to the bus to output electrical energy to the main power supply grid.

[0010] In one embodiment of the present invention, the harmonic monitoring device includes a first harmonic monitor and a second harmonic monitor installed on the transmission line, the first harmonic monitor is configured between the boost device and the output end of the transmission line to monitor the harmonic source of the transmission unit, and the second harmonic monitor is configured between the boost device and the bus to monitor the harmonic source of the photovoltaic power station.

[0011] In one embodiment of the present invention, the reactive power compensation device comprises a static reactive power generator, and the static reactive power generator is used to balance the active power and reactive power of the photovoltaic power station.

[0012] In one embodiment of the present invention, the power transmission unit further includes a power switch, and the power switch is arranged at one end of the transmission line close to the bus bar.

[0013] In one embodiment of the present invention, the photovoltaic power station also includes an overvoltage protection unit, which includes at least one overvoltage protector and at least one grounding switch. Each photovoltaic power generation module is configured with one overvoltage protector and one grounding switch, and the overvoltage protector is connected in parallel with the grounding switch.

[0014] In one embodiment of the present invention, a control unit is further included, and the control unit is connected to the harmonic monitoring unit and the harmonic control unit to collect and analyze the data monitored by the harmonic monitoring unit and issue execution instructions.

[0015] The present invention also provides a method for harmonic control of a photovoltaic power station grid, the harmonic control method is used to control harmonics of the photovoltaic power station grid system as described above, and the harmonic control method comprises: Step S1, performing a first harmonic monitoring on the photovoltaic power station and the transmission unit, obtaining monitoring results, and confirming the number and location of harmonic sources according to the monitoring results; Step S2, connecting the LC passive filtering device in parallel with the harmonic source, and using the LC passive filtering device to offset the harmonics generated by the harmonic source, so as to perform harmonic control on the harmonic source.

[0016] In one embodiment of the present invention, in step S1, when there is one harmonic source, an LC passive filtering device is connected in parallel with the harmonic source, and the harmonics generated by the harmonic source are offset by the LC passive filtering device; When there is more than one harmonic source, the harmonic sources are sorted according to their influence. First, the harmonic source with the greatest influence is treated by connecting the LC passive filter device in parallel with the harmonic source with the greatest influence to offset the harmonics generated by it. Continue monitoring. When the monitored harmonics are within the specified range, it means that the harmonics of the entire photovoltaic power station have been controlled. When the monitored harmonics are still not within the specified range, it means that the harmonics have not been completely controlled, and the harmonic sources with the second largest impact are controlled. The remaining harmonic sources are continuously monitored and controlled in order from high to low until the monitored harmonics are within the specified range. This means that the harmonics of the entire photovoltaic power station are controlled.

[0017] In one embodiment of the present invention, in step S1 and step S2, harmonic monitoring is performed on the photovoltaic power station and the power transmission unit by a harmonic monitoring device.

[0018] In one embodiment of the present invention, in step S1, a spectrum diagram is analyzed and drawn according to the harmonic monitoring result, and the influence distribution results of different harmonic sources are obtained according to the spectrum diagram, and the different harmonic sources are sorted according to their influence sizes.

[0019] In one embodiment of the present invention, the monitoring of the harmonics needs to distinguish between daytime and nighttime.

[0020] The above technical solution of the present invention has the following advantages compared with the prior art: A photovoltaic power station grid system described in the present invention is provided with a photovoltaic power station, a transmission unit, a harmonic monitoring unit and a harmonic control unit, wherein the photovoltaic power station includes a busbar and a plurality of photovoltaic power generation modules connected to the busbar in an array, a reactive power compensation device is connected to any photovoltaic power generation module, and the output electric energy of the plurality of photovoltaic power generation modules is transmitted to the transmission unit through the busbar, and then transmitted to the main power supply grid after being boosted by the transmission unit. During operation, the photovoltaic power station grid system is monitored by the harmonic monitoring unit to find the location of the harmonic source, and then the LC passive filtering device is connected in parallel with the harmonic source to suppress and eliminate the harmonics, so that the harmonics in the system are reduced to a specified range, thereby reducing the impact of the harmonics on the power grid, improving the output power quality, and enhancing the stability of the power grid, which is conducive to the safe and stable operation of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0022] Figure 1 It is a schematic diagram of the overall structure of a preferred embodiment of the present invention.

[0023] Explanation of the markings in the specification: 1. busbar; 1B. booster; 2. reactive power compensation device; 3. transmission line; 3545. three-position switch; 151. first harmonic monitor; 301. second harmonic monitor; 351. first circuit breaker; 3510. first monitoring module; 352. second circuit breaker; 3520. second monitoring module; 353. third circuit breaker; 3530. third monitoring module; 354. fourth circuit breaker; 3540. fourth monitoring module. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Example

[0025] Reference Figure 1 As shown, the present invention discloses a photovoltaic power station power grid system, including a photovoltaic power station, wherein the photovoltaic power station includes a bus 1, a photovoltaic power generation unit and a reactive compensation device 2, the photovoltaic power generation unit includes a plurality of array photovoltaic power generation modules connected to the bus, and the reactive compensation device 2 is connected to one of the photovoltaic power generation modules.

[0026] Each of the photovoltaic power generation modules includes a collector, a circuit breaker and a power generation circuit. The power generation circuit is connected to the bus 1 through the collector, and the circuit breaker is used to control the on and off of the collector.

[0027] Furthermore, the photovoltaic power station grid system further includes a power transmission unit, which is connected to the main power supply grid, and the output end of the bus 1 is connected to the power transmission unit to transmit the output electric energy of the photovoltaic power station to the power transmission unit; The photovoltaic power station grid system further includes a harmonic monitoring unit, and the harmonic monitoring unit includes at least one harmonic monitoring device for monitoring a harmonic source; Furthermore, the photovoltaic power station grid system also includes a harmonic control unit, which includes at least one LC passive filter device, and at least one of the LC passive filter devices is configured to be connected in parallel with the line where the harmonic source is located.

[0028] In detail, the LC passive filtering device includes a load switch and inductor and capacitor components connected in series.

[0029] It can be known from this that the photovoltaic power station power grid system to be protected by the present invention is provided with a photovoltaic power station, a transmission unit, a harmonic monitoring unit and a harmonic control unit, wherein the photovoltaic power station includes a busbar, and a plurality of photovoltaic power generation modules connected to the busbar in an array, a reactive compensation device is connected to any photovoltaic power generation module, and the output electric energy of the plurality of photovoltaic power generation modules is transmitted to the transmission unit through the busbar, and after the transmission unit is boosted, it is transmitted to the main power supply grid. During operation, the photovoltaic power station power grid system is monitored by the harmonic monitoring unit to find the location of the harmonic source, and then the LC passive filtering device is connected in parallel with the harmonic source to suppress and eliminate the harmonics, so that the harmonics in the system are reduced to a specified range, thereby reducing the impact of the harmonics on the power grid, improving the output power quality, and enhancing the stability of the power grid, which is conducive to the safe and stable operation of the power grid.

[0030] Specifically, each of the photovoltaic power generation modules also includes a first monitoring device, which is arranged on the collecting line. The first monitoring device includes a first voltage transformer and a first current transformer. The first voltage transformer is used to monitor the voltage signal of the bus 1, and the first current transformer is used to monitor the current signal of the bus 1.

[0031] In detail, the LC passive filtering device includes the load switch 3545, the first inductor L, the first capacitor C1, the second capacitor C2, the third capacitor C3, and the fourth capacitor C4 which are sequentially connected in series along the input end.

[0032] The LC passive filtering device further comprises a second voltage transformer TV, and the second voltage transformer TV is used to monitor the voltage signal of the LC passive filtering device.

[0033] As a preferred implementation, the load switch in the LC passive filtering device is configured as a three-position switch 3545, thereby effectively avoiding circuit damage caused by operational errors.

[0034] Furthermore, the transmission unit includes a transmission line 3 and a boosting device 1B, the boosting device 1B is installed on the transmission line 3 to boost the output voltage of the photovoltaic power station, the output end of the transmission line 3 is connected to the main power supply grid, and the other end of the transmission line is connected to the bus to output electric energy to the main power supply grid.

[0035] It should be noted that the boost device 1B includes but is not limited to a transformer.

[0036] In detail, the harmonic monitoring device includes a first harmonic monitor 151 and a second harmonic monitor 301 mounted on the transmission line 3. The first harmonic monitor 151 is arranged between the boost device 1B and the output end of the transmission line 3 to monitor the harmonic source of the power transmission unit. The second harmonic monitor 301 is arranged between the boost device 1B and the bus 1 to monitor the harmonic source of the photovoltaic power station.

[0037] As a preferred embodiment, Figure 1 As shown, the busbar 1 is a 35KV collector, and the photovoltaic power station includes a first photovoltaic power generation module, a second photovoltaic power generation module, a third photovoltaic power generation module and a fourth photovoltaic power generation module.

[0038] In this embodiment, the transformer can increase the voltage from 35KV of the bus 1 to 110KV.

[0039] The first photovoltaic power generation module includes a first collector, a first circuit breaker 351, a first monitoring module 3510, and a first power generation circuit. The first power generation circuit is connected to the bus 1 through the first collector to transmit the electric energy obtained by the first power generation circuit to the bus 1. The first monitoring module includes a first CT (current transformer) and a first PT (voltage transformer) installed on the first collector. The first power generation circuit includes a first photovoltaic panel and a first inverter module matched therewith.

[0040] The second photovoltaic power generation module includes a second collector, a second circuit breaker 352, a second monitoring module 3520 and a second power generation circuit. The second power generation circuit is connected to the bus 1 through the second collector to transmit the electric energy obtained by the second power generation circuit to the bus 1. The second monitoring module includes a second CT (current transformer) and a second PT (voltage transformer) installed on the second collector. The second power generation circuit includes a second photovoltaic panel and a second inverter module matched therewith.

[0041] The third photovoltaic power generation module includes a third collector, a third circuit breaker 353, a third monitoring module 3530 and a third power generation circuit. The third power generation circuit is connected to the bus 1 through the third collector to transmit the electric energy obtained by the third power generation circuit to the bus 1. The third monitoring module includes a third CT (current transformer) and a third PT (voltage transformer) installed on the third collector. The third power generation circuit includes a third photovoltaic panel and a third inverter module matched therewith.

[0042] The fourth photovoltaic power generation module includes a fourth collector, a fourth circuit breaker 354 , and a fourth monitoring module 3540 . The fourth monitoring module includes a fourth CT (current transformer) and a fourth PT (voltage transformer) installed on the fourth collector.

[0043] With such a configuration, the real-time current signal and voltage signal of the bus 1 can be monitored through CT (current transformer) and PT (voltage transformer), and the 35KV voltage can be inducted into low voltage by PT (voltage transformer), so as to facilitate the subsequent harmonic control. CT (current transformer) can convert large current into small current for measurement or protection, and PT (voltage transformer) can convert high voltage into low voltage for measurement or protection.

[0044] The reactive power compensation device 2 is connected to the fourth photovoltaic power generation module. The reactive power compensation device 2 includes a SVG (Static Var Generator), which is a static var generator, and the static var generator is used to balance the active power and reactive power of the photovoltaic power station.

[0045] In principle, the main function of the SVG for the system is to regulate the voltage. It is connected to the bus 1. When the voltage of the entire power system increases, it is necessary to ensure that the line loss is at a low level during the power transmission process. However, during the peak period of power consumption, the overall load of the system increases, which can easily lead to the collapse of the circuit system. Therefore, during the day, it is necessary to generate reactive power through the SVG to increase the voltage and maintain the stability of the circuit. At night, the power system has a small carrying capacity, but the voltage of the entire system increases, and the photovoltaic power station is in a no-load state. If there is an overvoltage in the photovoltaic power station under no-load conditions, it will also have an adverse effect on it. Therefore, at night, it is necessary to absorb part of the reactive power from the system through the SVG to reduce the voltage and achieve a balance between active power and reactive power.

[0046] The second harmonic monitor 301 monitors the harmonic source of the photovoltaic power station and confirms that the reactive compensation device 2 is the main source of harmonics. Therefore, the LC passive filter device is installed in the photovoltaic power station and connected in parallel with the reactive compensation device 2 to change the spectrum characteristics of the photovoltaic power station and achieve harmonic control.

[0047] In principle, harmonic control adopts instantaneous reactive power theory, collects voltage and current signals on the 35kV side of the main transformer in real time, and generates sine and cosine signals of the same phase through a phase-locked link. Sine and cosine are synthesized into a C signal matrix. The three-phase current is transformed orthogonally and synthesized into a C matrix to obtain instantaneous active current and instantaneous reactive current. The two signals are passed through a low-pass filter to obtain a DC component, and the two signals are for fundamental active current and reactive current. The two current signals are squared to finally obtain a three-phase fundamental current. This signal is subtracted from the original signal to obtain a harmonic current signal. The reactive power compensation device outputs a reverse harmonic current through modulation. For example, the 5th reverse harmonic current and the 5th harmonic current generated by the photovoltaic power generation module are superimposed to achieve comprehensive control of the 5th harmonic current.

[0048] By connecting the LC passive filtering device in parallel with the reactive compensation device 2, when the frequency of the input signal changes, the inductance and capacitance in the LC passive filtering device will also respond differently to the signal. When the frequency is low, the inductance has a larger impedance to the signal, while the capacitance has a smaller impedance to the signal. Thus, the inductance plays a role in preventing low-frequency signals from passing through, thereby filtering out the low-frequency signals. When the frequency is high, the inductance has a smaller impedance to the signal, while the capacitance has a larger impedance to the signal. Thus, the capacitance plays a role in preventing high-frequency signals from passing through, thereby filtering out high-frequency signals. Thus, the suppression of harmonics is achieved, thereby reducing the impact of harmonics on the power grid, which is beneficial to the safe and stable operation of the power grid.

[0049] Specifically, the power transmission unit further includes a power supply switch, which is disposed on one end of the transmission line 3 close to the bus bar 1 , and the power supply switch can regulate the on and off of the power transmission unit.

[0050] As a preferred embodiment, the photovoltaic power station also includes an overvoltage protection unit. Specifically, the overvoltage protection unit includes at least one overvoltage protector and at least one grounding switch. In order to perform overvoltage protection on the photovoltaic power station, each photovoltaic power generation module in the photovoltaic power station is configured with an overvoltage protector and a grounding switch. The overvoltage protector is connected in parallel with the grounding switch. At the same time, the first monitoring device of each photovoltaic power generation module is connected in parallel with the overvoltage protection unit. In this way, overvoltage protection can be achieved for each photovoltaic power generation module.

[0051] Specifically, the overvoltage protector includes but is not limited to a lightning arrester.

[0052] It should be noted that the photovoltaic power station power grid system also includes a control unit, which is connected to the harmonic monitoring unit and the harmonic control unit, so that the control unit can collect and analyze the data monitored by the harmonic monitoring unit and issue execution instructions to facilitate the subsequent adoption of corresponding harmonic control measures. Example

[0053] The present invention also discloses a harmonic control method for a photovoltaic power station grid, the harmonic control method is used to control the harmonics of the photovoltaic power station grid system as described in the first embodiment, and the harmonic control method includes: Step S1, performing a first harmonic monitoring on the photovoltaic power station and the transmission unit, obtaining monitoring results, and confirming the number and location of harmonic sources according to the monitoring results; Step S2, connecting the LC passive filtering device in parallel with the harmonic source, and using the LC passive filtering device to offset the harmonics generated by the harmonic source, so as to perform harmonic control on the harmonic source.

[0054] From this, it can be seen that through a harmonic control method to be protected by the present invention, it is possible to suppress and control harmonics in photovoltaic power stations, reduce the damage caused by harmonics to the power grid, and thereby improve the output power quality and enhance the stability of the power grid.

[0055] In terms of implementation details, in step S1, when there is one harmonic source, an LC passive filtering device is connected in parallel with the harmonic source, and the harmonics generated by the harmonic source are offset by the LC passive filtering device; When there is more than one harmonic source, the harmonic sources are sorted according to their influence. First, the harmonic source with the greatest influence is treated by connecting the LC passive filter device in parallel with the harmonic source with the greatest influence to offset the harmonics generated by it. Continue to monitor harmonics; when the monitored harmonics are within the specified range, it means that the harmonics of the entire photovoltaic power station have been controlled; When the monitored harmonics are still not within the specified range, it means that the harmonics have not been completely controlled, and the harmonic source with the second greatest impact is controlled. Specifically, a second LC passive filtering device is connected in parallel with the harmonic source with the second greatest impact. Then, the harmonics are monitored again to determine whether the harmonics in the system are within the specified range. When the monitored harmonics are within the specified range, it means that the harmonics of the entire photovoltaic power station are controlled. When the monitored harmonics are still not within the specified range, it means that the harmonics have not been completely controlled. Then, continue to monitor and control the remaining harmonic sources in order from high to low until the monitored harmonics are within the specified range, which means that the harmonics of the entire photovoltaic power station are controlled.

[0056] As a preferred implementation, in step S1 and step S2, the photovoltaic power station and the power transmission unit are subjected to harmonic monitoring by a harmonic monitoring device. Specifically, in the process of searching for harmonic sources, the harmonic source of the power transmission unit (i.e., the grid side) is monitored by the first harmonic monitor 151, and the harmonic source of the photovoltaic power station side is monitored by the second harmonic monitor 301, and it is determined which device the harmonic source comes from (from the inverter, reactive power compensation unit or other device).

[0057] If the harmonics on the photovoltaic power station side are not effectively controlled, the distorted voltage and current will enter the grid side, which will cause grid side harmonics. The present invention mainly controls the harmonics within the photovoltaic power station.

[0058] In detail, in step S1, according to the harmonic monitoring result, a spectrum diagram is analyzed and drawn, and the influence distribution results of different harmonic sources are obtained according to the spectrum diagram, and the different harmonic sources are sorted according to their influence size.

[0059] It should be noted that the monitoring of harmonics should be distinguished between daytime and nighttime. Due to the power generation properties of the photovoltaic power station itself, it generates electricity during the day, so it is in a full-load state during the day, and does not generate electricity at night, so it is in a no-load state. Therefore, the harmonic monitoring of the transmission unit and the photovoltaic power station should be distinguished between daytime and nighttime, so as to obtain different monitoring results.

[0060] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be 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.

[0061] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0062] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0063] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A photovoltaic power station power grid system, characterized in that: include, A photovoltaic power station, comprising a busbar, a photovoltaic power generation unit and a reactive power compensation device, wherein the photovoltaic power generation unit comprises a plurality of array photovoltaic power generation modules connected to the busbar, and the reactive power compensation device is connected to one of the photovoltaic power generation modules, wherein each photovoltaic power generation module comprises a collector, a circuit breaker and a power generation circuit, wherein the power generation circuit is connected to the busbar through the collector, and the circuit breaker is used to control the on and off of the collector; A power transmission unit connected to the main power supply grid, wherein the output end of the busbar is connected to the power transmission unit; a harmonic monitoring unit, comprising at least one harmonic monitoring device for monitoring a harmonic source; The harmonic control unit comprises at least one LC passive filtering device, wherein at least one of the LC passive filtering devices is configured to be connected in parallel with the harmonic source, and the LC passive filtering device comprises a load switch and inductor and capacitor components connected in series with each other.

2. A photovoltaic power station power grid system according to claim 1, characterized in that: The photovoltaic power generation module also includes a first monitoring device, which is arranged on the collecting line. The first monitoring device includes a first voltage transformer and a first current transformer. The first voltage transformer is used to monitor the voltage signal of the bus, and the first current transformer is used to monitor the current signal of the bus.

3. A photovoltaic power station power grid system according to claim 1, characterized in that: The LC passive filtering device further includes a second voltage transformer, which is used to monitor the voltage signal of the LC passive filtering device.

4. A photovoltaic power station power grid system according to any one of claims 1 to 3, characterized in that: The power transmission unit includes a transmission line and a boosting device, wherein the boosting device is installed on the transmission line to boost the output voltage of the photovoltaic power station, the output end of the transmission line is connected to the main power supply grid, and the other end of the transmission line is connected to the bus to output electrical energy to the main power supply grid.

5. A photovoltaic power station power grid system according to claim 4, characterized in that: The harmonic monitoring device includes a first harmonic monitor and a second harmonic monitor installed on the transmission line. The first harmonic monitor is configured between the boost device and the output end of the transmission line to monitor the harmonic source of the transmission unit, and the second harmonic monitor is configured between the boost device and the bus to monitor the harmonic source of the photovoltaic power station.

6. A photovoltaic power station power grid system according to claim 1, characterized in that: The reactive power compensation device comprises a static reactive power generator, and the static reactive power generator is used to balance the active power and reactive power of the photovoltaic power station.

7. A photovoltaic power station power grid system according to claim 4, characterized in that: The power transmission unit further includes a power supply switch, which is disposed at one end of the transmission line close to the bus bar.

8. A photovoltaic power station power grid system according to claim 1, characterized in that: The photovoltaic power station also includes an overvoltage protection unit, which includes at least one overvoltage protector and at least one grounding switch. Each photovoltaic power generation module is configured with one overvoltage protector and one grounding switch, and the overvoltage protector is connected in parallel with the grounding switch.

9. A photovoltaic power station power grid system according to claim 1, characterized in that: It also includes a control unit, which is connected to the harmonic monitoring unit and the harmonic control unit to collect and analyze the data monitored by the harmonic monitoring unit and issue execution instructions.

10. A method for harmonic control of a photovoltaic power station grid, characterized in that: The harmonic control method is used to control harmonics in the photovoltaic power station power grid system according to any one of claims 1 to 9, and the harmonic control method includes: Step S1, performing a first harmonic monitoring on the photovoltaic power station and the transmission unit, obtaining monitoring results, and confirming the number and location of harmonic sources according to the monitoring results; Step S2, connecting the LC passive filtering device in parallel with the harmonic source, and using the LC passive filtering device to offset the harmonics generated by the harmonic source, so as to perform harmonic control on the harmonic source.

11. A method for harmonic control of a photovoltaic power station grid according to claim 10, characterized in that: In the step S1, when there is one harmonic source, an LC passive filtering device is connected in parallel with the harmonic source, and the harmonics generated by the harmonic source are offset by the LC passive filtering device; When there is more than one harmonic source, the harmonic sources are sorted according to their influence. First, the harmonic source with the greatest influence is treated by connecting the LC passive filter device in parallel with the harmonic source with the greatest influence to offset the harmonics generated by it. Continue monitoring. When the monitored harmonics are within the specified range, it means that the harmonics of the entire photovoltaic power station have been controlled. When the monitored harmonics are still not within the specified range, it means that the harmonics have not been completely controlled, and the harmonic sources with the second largest impact are controlled. The remaining harmonic sources are continuously monitored and controlled in order from high to low until the monitored harmonics are within the specified range. This means that the harmonics of the entire photovoltaic power station are controlled.

12. A method for harmonic control of a photovoltaic power station grid according to claim 11, characterized in that: In the step S1 and the step S2, harmonic monitoring is performed on the photovoltaic power station and the power transmission unit by a harmonic monitoring device.

13. A method for harmonic control of a photovoltaic power station grid according to claim 11, characterized in that: In the step S1, according to the harmonic monitoring result, a frequency spectrum is analyzed and drawn, and the influence distribution results of different harmonic sources are obtained according to the frequency spectrum, and the different harmonic sources are sorted according to their influence sizes.

14. A method for harmonic control of a photovoltaic power station grid according to claim 11, characterized in that: The monitoring of the harmonics needs to be differentiated between daytime and nighttime.

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