CN108767861B - Two-stage filtering implementation method applied to distributed and centralized coordination of photovoltaic power station - Google Patents
Two-stage filtering implementation method applied to distributed and centralized coordination of photovoltaic power station Download PDFInfo
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- CN108767861B CN108767861B CN201810287196.5A CN201810287196A CN108767861B CN 108767861 B CN108767861 B CN 108767861B CN 201810287196 A CN201810287196 A CN 201810287196A CN 108767861 B CN108767861 B CN 108767861B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract
The invention discloses a two-stage filtering implementation method applied to a photovoltaic power station and used for realizing dispersion and concentration coordination, wherein the photovoltaic power station is provided with a primary filtering station and a secondary filtering station which are formed by an integrated filtering box type transformer and an induction filtering grid-connected transformer; the primary power station is arranged in each box-type split transformer in the power generation area, and the filter reactor is integrated in the transformer to reduce the installation space; the secondary filter station is arranged in the grid-connected booster station, and the grid-connected transformer adopts an inductive filtering technology to damp harmonic resonance; the two-stage filtering stations are mutually coordinated to suppress the characteristic subharmonic, and the method has the characteristics of filtering the harmonic in a distributed manner and improving the electric energy quality in a centralized manner. This photovoltaic power plant simple structure just is convenient for integrate the design, according to actual demand adjusting device parameter, can be applied to in the photovoltaic power plant of different scales.
Description
Technical Field
The invention relates to the technical field of photovoltaic power station electric energy quality control, in particular to a dispersion and concentration coordination two-stage filtering implementation method applied to a photovoltaic power station.
Background
With the gradual maturity of new energy power generation technology, the permeability of the electric energy output by the photovoltaic power generation system in the power system is continuously improved. The large photovoltaic power station adopts an inverter as an interface for alternating current-direct current electric energy conversion between a photovoltaic array and a power grid, and the inverter discharges a large amount of harmonic waves and reactive current to the power grid due to the inherent nonlinear characteristic of the inverter, so that the quality of electric energy of a grid connection point is seriously influenced.
In order to meet the power quality requirement of grid connection of a photovoltaic power station, a conventional method is to connect a passive filter device in series with a low-voltage bus of a 110kV booster station. However, due to the randomness and the wave shape of photovoltaic power generation, the passive filter is easy to match with the impedance of a power grid so as to cause a resonance phenomenon and even cause harmonic amplification. In addition, the output of the photovoltaic power station is not balanced within one day, so that a large margin is needed for the reactive compensation design capacity of the filter. At present, no solution with higher cost performance exists in the field of electric energy quality management of photovoltaic power stations.
Disclosure of Invention
In view of the above, in order to solve the above problems in the prior art, the present invention provides a method for implementing two-stage filtering with coordination between dispersion and concentration applied to a photovoltaic power station, so as to implement distributed filtering of output harmonic waves at a power generation side and centralized improvement of power quality at a grid-connected point.
The invention solves the problems through the following technical means:
a two-stage filtering implementation method with dispersion and concentration coordination applied to a photovoltaic power station is characterized in that two stages of filtering stations with coordination are arranged in the photovoltaic power station and respectively comprise a first-stage filtering station and a second-stage filtering station, and the two-stage filtering station is used for realizing distributed filtering of harmonic waves and improving the quality of electric energy in a centralized mode through coordination;
the primary filtering station is arranged in each integrated filtering box type transformer in a photovoltaic power generation area and comprises a group of three-phase tuning filters and filtering capacitors matched with the three-phase tuning filters, the filtering reactors of the tuning filters are used as transformer windings for decoupling and integrating the three-phase tuning filters in the integrated filtering box type transformer, and the filtering capacitors matched with the three-phase tuning filters are also arranged in the integrated filtering box type transformer;
the secondary filter station is arranged in the grid-connected booster station, an induction filter grid-connected transformer of the grid-connected booster station adopts a three-winding structure and comprises three windings, namely a high winding, a medium winding and a low winding, wherein the high winding and the medium winding are connected with a power generation area and used for grid-connected boosting with a power grid, the low winding is a filter winding with zero equivalent reactance, and a filter device required by the secondary filter station is connected with the grid-connected transformer through the filter winding.
Further, the secondary filtering station comprises a group of tuning filters and SVG devices connected in series with the tuning filters.
Further, the equivalent impedance of the low-voltage winding of the induction filtering grid-connected transformer is obtained by the following formula:
in the formula (II), Z'h12、Zh31、Zh32The short-circuit impedances between the high-voltage winding and the medium-voltage winding, between the high-voltage winding and the low-voltage winding and between the medium-voltage winding and the low-voltage winding are respectively; z is a linear or branched member3hThe low-voltage winding is arranged between the high-voltage winding and the low-voltage winding, and the equivalent impedance of the low-voltage winding can be zero by adjusting the structural size of each winding.
Furthermore, the filter parameters of the first-stage filter station and the second-stage filter station are designed in a coordinated manner according to actual conditions so as to filter out 3, 5 and 7 major order harmonics.
Compared with the prior art, the invention has the beneficial effects that at least:
the two-stage filter stations are arranged in a coordinated manner, so that the grid-connected power quality requirement of the photovoltaic power station is met, and the compensation burden of a reactive compensation device in the grid-connected booster station is reduced; the design of the primary filter station achieves the following objectives: 1) locally lifting the output voltage of the photovoltaic inverter; 2) characteristic subharmonics generated by the photovoltaic inverter are filtered, and the burden of a secondary filtering station is reduced; 3) the box transformer substation and the filter are integrated, so that the floor area is reduced, and the operation management of equipment is simplified; the design of the secondary filtering station achieves the following purposes: 1) lifting the output voltage to a grid-connected voltage; 2) carrying out harmonic suppression and reactive compensation in a centralized manner, and ensuring that the quality of the electric energy of the grid-connected point meets the national standard; 3) and potential harmonic resonance phenomena between the damping tuned filter and the impedance of the power grid.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of an embodiment of a photovoltaic power plant including two stages of filter stations in accordance with the present invention;
FIG. 2 is a schematic diagram of an integrated filter box transformer of the present invention;
fig. 3 is a schematic diagram of an inductive filtering grid-connected transformer according to the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It should be noted that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art without any inventive work based on the embodiments of the present invention belong to the protection scope of the present invention.
Examples
Referring to fig. 1, the photovoltaic power plant of the present invention includes three power generation areas. The two photovoltaic inverters and the integrated filtering reactance type split transformer form a power generation unit. And 20 power generation units form a power generation area, and the output current of the power generation area is converged by a 35kV collecting line and then is sent to a 110kV grid-connected booster station.
The primary filtering station of the invention is arranged at an integrated box type transformer inside a single power generation area. As shown in fig. 2, the integrated filter reactance type split transformer can be regarded as a three-phase five-winding transformer: one high-voltage winding and two low-voltage windings form a split transformer, and the rest two windings are integrated filter reactors which are decoupled from power of other power supply windings. The single integrated filter reactor is formed by reversely connecting two sections of sub-coils with the same number of turns in series, and main magnetic chains of the two sub-coils are mutually offset to realize decoupling. The integrated filter reactor and a filter capacitor arranged in the electric box can be matched to work to filter out specific subharmonics.
The secondary filter station is arranged in the 110kV grid-connected booster station and consists of an induction filter grid-connected transformer and a matched filter device thereof. As shown in fig. 3, the induction filtering grid-connected transformer is a three-phase three-winding transformer, and the high-voltage winding is directly connected with the power grid; the three groups of power generation regions are connected to a medium-voltage winding of the grid-connected booster station through a 35kV overhead line; the specially designed low-voltage winding is in angular connection, and a matched filtering device formed by connecting a group of single-tuned filters and an SVG in parallel is connected to a main transformer through a common connection point of the angular connection winding. According to the basic principle of the induction filtering method, the equivalent impedance of the low-voltage winding for filtering is approximately designed to be zero so as to ensure that harmonic current from a photovoltaic power generation area can be counteracted between the medium-voltage winding and the low-voltage winding in an induction mode.
In the embodiment, the filters of the two-stage filtering station are tuned to 5 th harmonic frequency, and the two harmonic frequencies are coordinated to filter most of characteristic order harmonics, so that the power quality of a grid-connected point is ensured.
The equivalent impedance of the low-voltage winding of the grid-connected transformer can be obtained by the following formula:
in the formula (II), Z'h12、Zh31、Zh32Short-circuit impedances between the high-voltage winding and the medium-voltage winding, between the high-voltage winding and the low-voltage winding, and between the medium-voltage winding and the low-voltage winding respectively; z is a linear or branched member3hIs the equivalent impedance of the low voltage winding. The low-voltage winding is arranged between the high-voltage winding and the low-voltage winding, and the equivalent impedance of the low-voltage winding can be made to be zero by adjusting the structural size of each winding.
In addition, because the tuning filter is connected with the secondary side of the transformer, the high-voltage winding of the transformer acts as system impedance and indirectly increases short-circuit impedance, thereby effectively avoiding the generation of harmonic resonance phenomenon.
The invention provides a method for realizing two-stage filtering with coordination between dispersion and concentration applied to a photovoltaic power station, wherein the photovoltaic power station is provided with two-stage filtering stations with coordination, and the method has the functions of realizing distributed harmonic filtering and improving the electric energy quality in a centralized manner by coordinating operation; the primary filtering station is arranged in each box-type double-split transformer in the photovoltaic power generation area, the primary filtering station is provided with a group of three-phase tuning filters, filter reactors of the tuning filters are used as transformer windings for decoupling and are integrated in the double-split transformers, and filter capacitors matched with the filter reactors are also arranged in an electric box; the secondary filter station is arranged in a boosting and network station of a photovoltaic power station, the boosting and grid-connected transformer adopts a three-winding structure, a high/medium voltage winding is connected with a power generation area and is used for grid-connected boosting with a power grid, a low voltage winding is a filter winding for implementing induction filtering, the equivalent reactance of the low voltage winding is designed to be zero, and a filter device is connected into the grid-connected transformer through the filter winding.
Specifically, in order to meet grid-connection requirements, the secondary filter station comprises a group of tuning filters and SVG devices connected in series with the tuning filters.
The filter parameters of the first-stage filtering station and the second-stage filtering station are designed coordinately according to actual conditions so as to filter out major order harmonics of 3, 5, 7 and the like.
The two-stage filter stations are arranged in a coordinated manner, so that the grid-connected power quality requirement of the photovoltaic power station is met, and the compensation burden of a reactive compensation device in the grid-connected booster station is reduced; the design of the primary filter station achieves the following objectives: 1) locally lifting the output voltage of the photovoltaic inverter; 2) characteristic subharmonics generated by the photovoltaic inverter are filtered, and the burden of a secondary filtering station is reduced; 3) the box transformer substation and the filter are integrated, so that the floor area is reduced, and the operation management of equipment is simplified; the design of the secondary filtering station achieves the following purposes: 1) lifting the output voltage to a grid-connected voltage; 2) carrying out harmonic suppression and reactive compensation in a centralized manner, and ensuring that the quality of the electric energy of the grid-connected point meets the national standard; 3) and potential harmonic resonance phenomena between the damping tuned filter and the impedance of the power grid.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (4)
1. A method for realizing dispersion and concentration coordinated two-stage filtering applied to a photovoltaic power station is characterized in that two stages of coordinated filtering stations are arranged in the photovoltaic power station and are respectively a first-stage filtering station and a second-stage filtering station, and the method is used for realizing dispersion filtering of harmonic waves and improving the quality of electric energy in a centralized mode through coordinated operation;
the primary filtering station is arranged in each integrated filtering box type transformer in a photovoltaic power generation area and comprises a group of three-phase tuning filters and filtering capacitors matched with the three-phase tuning filters, filtering reactors of the tuning filters are used as transformer windings for decoupling and are integrated in the integrated filtering box type transformer, and the filtering capacitors matched with the three-phase tuning filters are also arranged in the integrated filtering box type transformer; the integrated filter box type transformer is a three-phase five-winding transformer: one high-voltage winding and two low-voltage windings form a split transformer, and the rest two windings are filter reactors which are decoupled from power of other power supply windings; the single filter reactor is formed by reversely connecting two sections of sub-coils with the same number of turns in series, and main magnetic chains of the two sub-coils are mutually offset to realize decoupling; the filter reactor and a filter capacitor arranged in the integrated filter box type transformer are matched to filter out specific subharmonic;
The secondary filter station is arranged in the grid-connected booster station, an induction filter grid-connected transformer of the grid-connected booster station adopts a three-winding structure and comprises three windings of high voltage, medium voltage and low voltage, wherein the medium voltage winding is connected with a power generation area, the high voltage winding is connected with a power grid for grid-connected boosting, the low voltage winding is a filter winding with zero equivalent reactance, and a filter device required by the secondary filter station is connected with the grid-connected transformer through the filter winding.
2. The decentralized and centralized coordinated two-stage filtering implementation method applied to photovoltaic power plants according to claim 1, characterized in that said two-stage filtering station comprises a set of tuned filters and SVG devices connected in series thereto.
3. The method for realizing distributed and centralized coordinated two-stage filtering applied to photovoltaic power stations as claimed in claim 1, wherein the equivalent impedance of the low-voltage winding of the induction filtering grid-connected transformer is obtained by the following formula:
in the formula (II), Z'h12、Zh31、Zh32Short-circuit impedances between the high-voltage winding and the medium-voltage winding, between the high-voltage winding and the low-voltage winding, and between the medium-voltage winding and the low-voltage winding respectively; z3hThe low-voltage winding is arranged between the high-voltage winding and the low-voltage winding, and the equivalent impedance of the low-voltage winding can be zero by adjusting the structural size of each winding.
4. The method of claim 1, wherein the filter parameters of the first and second filtering stations are designed to filter out 3, 5, and 7 major harmonics according to practical conditions.
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