CN106786585A - Based on the autonomous photovoltaic poverty alleviation rural power grids electric energy quality optimizing device and method of collaboration - Google Patents
Based on the autonomous photovoltaic poverty alleviation rural power grids electric energy quality optimizing device and method of collaboration Download PDFInfo
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The present invention is in order in solving existing photovoltaic anti-poverty project rural power grids, conventional power quality controlling device function is more single, regulation effect problem preferable not to the utmost, there is provided a kind of photovoltaic poverty alleviation rural power grids electric energy quality optimizing device and method autonomous based on collaboration.The device, including：Quality of power supply tuning controller, its ABC three-phase for being connected to Rural Low-Voltage Power Network platform area total input-wire position detects control circuit of the concurrent power transmission energy quality information to single-phase electric energy quality controlling device；Single-phase electric energy quality controlling device, including inverter circuit and control circuit, the DC side of inverter circuit connects an energy storage device, a phase line and zero line in the AC and control circuit connection ABC three-phases of inverter circuit, control the quality of power supply information of electric circuit inspection access point, the quality of power supply information of tuning controller is received simultaneously, and control IGBT switching devices carry out electric current output.The present invention is obviously improved the quality of power supply operation level of low-voltage platform area, improves the operational efficiency and economy of power distribution network, while also reducing the cost of low-voltage platform area quality of power supply construction retrofit, is generally applicable to vast rural power grids.
Description
Technical Field
The invention relates to the technical field related to power quality control, in particular to a photovoltaic poverty-relief rural power grid power quality optimization device and a control method based on cooperative autonomy, which are an optimization device and a control method for comprehensively treating the power quality of a photovoltaic poverty-relief rural power grid, can effectively solve the power quality problem of the rural power grid, remarkably improve the power quality operation level of a low-voltage platform area, improve the operation efficiency and economy of a power distribution network, and simultaneously can reduce the cost of power quality construction and reconstruction of the low-voltage platform area.
Background
In recent years, with the continuous investment of national power grids and southern power grid companies in the construction and transformation of power distribution networks, the problems of power supply reliability and low voltage of the power distribution networks are improved to a certain extent. However, in rural areas, the land is wide, people are rare, the load is dispersed, the conditions of few distribution points in a distribution area, long distribution distance and small line diameter design are common in consideration of the economical efficiency of distribution network construction, and particularly, the power quality problem of rural networks is further worsened along with the wide promotion of the national photovoltaic poverty-relief project in the rural areas. The electric energy quality problem after the photovoltaic poverty alleviation project is connected to the rural power grid mainly has the following aspects:
1) voltage deviation problem. Because rural area is extensive and rare, and the power consumption load dispersion, consider the economic nature of joining in marriage net construction, the distribution station is few, distribution distance is long, the line footpath design condition on the small side is comparatively general, causes the distribution lines voltage drop to be on the large side, and the power supply terminal voltage phenomenon on the low side is comparatively serious. In addition, after the photovoltaic poverty alleviation project is connected into the rural power grid, the power flow of the power distribution network can be changed, the voltage of some load nodes is raised, and the problem of high voltage is caused. How much the voltage is raised is related to the location and capacity of access to the distributed photovoltaic. The low or high voltage is not favorable for the safe and stable operation of the low-voltage transformer area.
2) The problem of insufficient reactive power. Resistive and inductive loads such as asynchronous motors, distribution transformers and the like in rural power networks occupy a large reactive proportion, and when reactive power required by the operation of the resistive and inductive loads cannot be balanced in place, the reactive power can be drawn from a superior power network, so that the power supply power factor of a distribution line is low, the reactive loss is increased, and the problem of low voltage at the power supply end is aggravated.
3) Three-phase unbalance problem. With the improvement of the living standard of rural areas, the number of high-power household appliances accessed to a rural power grid is continuously increased, and the problem of unbalanced load power utilization of the rural power grid is caused by the disordered access of the household appliances. And as the single-phase photovoltaic poverty-relief is randomly accessed in the low-voltage distribution network, the problem of unbalanced three-phase power flow of the rural power grid is further aggravated. The low-voltage rural power grid has less consideration to the problem of three-phase imbalance during planning and design, the selection of the neutral line diameter is usually smaller, the zero-sequence current loop impedance is larger, and the imbalance of three-phase power utilization easily causes the imbalance of three-phase power supply voltage. Three-phase imbalance can increase low-voltage grid loss, worsening the low-voltage problem at the end of the power supply.
4) The harmonic problem. Harmonic sources in the rural power grid are mainly electric equipment with nonlinear characteristics, namely a generator, a motor, a transformer and the like, and harmonic current can be generated due to the nonlinear excitation characteristics of the electric equipment; and secondly, the energy-saving lamps, household appliances and other equipment are large in quantity and dispersed, and harmonic pollution can be generated to the system. The power harmonic wave not only causes the distortion of voltage waveform and the increase of power loss, but also can affect the normal operation of the power equipment and even destroy the power equipment. With the application of the photovoltaic poverty-alleviation project in the rural power grid, the high-order harmonic current generated by the photovoltaic inverter can also cause the electromagnetic compatibility problem of the household appliance.
Therefore, the power quality problem in the rural power grid is frequently that multiple factors coexist and influence each other, multiple measures are needed and taken when the power quality is controlled, and the conventional power quality control device in the current market is often single in function and not ideal in control effect in practical application.
Disclosure of Invention
The invention provides a photovoltaic poverty-alleviation rural power grid electric energy quality optimization device and method based on cooperative autonomy, and aims to solve the problems that in the existing rural power grid for developing photovoltaic poverty-alleviation projects, the electric energy quality problems are frequently caused by coexistence and mutual influence of multiple factors, multiple measures are needed and taken when the electric energy quality is improved, and the conventional electric energy quality improvement device in the existing market is often single in function and not ideal in improvement effect in practical application.
The technical problem to be solved by the invention can be realized by the following technical scheme:
in a first aspect of the invention, a photovoltaic poverty-alleviation rural power grid electric energy quality optimization device based on cooperative autonomy is applied to a rural power grid connected with a poverty-alleviation photovoltaic device in a low-voltage platform area, and is characterized by comprising:
the electric energy quality coordination controller is connected with the ABC three phases at the main incoming line position of the rural power grid low-voltage transformer area, detects the electric energy quality of the ABC three phases and sends the electric energy quality information;
the single-phase electric energy quality treatment device comprises an inverter circuit and a control circuit, wherein the inverter circuit and the control circuit are formed by IGBT switching devices, an energy storage device is connected to the direct current side of the inverter circuit, a phase line and a zero line in ABC three phases are connected to the alternating current side of the inverter circuit, the control circuit is connected with the phase line and the zero line in the ABC three phases connected to the alternating current side of the inverter circuit, electric energy quality information of an access point is detected, and meanwhile, the electric energy quality information sent by the electric energy quality coordination controller is received to control the IGBT switching devices to output current.
In the invention, at least 3 single-phase power quality control devices are respectively and correspondingly connected with each phase line and zero line in the ABC three phases.
In the invention, the single-phase power quality treatment device is arranged at a position which is far from a main incoming line 1/2-2/3 from a power supply line of a rural power grid low-voltage transformer area.
In the invention, the electric energy quality information detected and sent by the electric energy quality coordination controller comprises reactive power information and three-phase imbalance information.
In a second aspect of the invention, a photovoltaic poverty-alleviation rural power grid electric energy quality optimization method based on cooperative autonomy is characterized by comprising the following steps:
1) determining a control function module which is required to be possessed by the single-phase power quality management device;
2) calculating the compensation current or the compensation capacity of the single-phase power quality treatment device according to the content of the power quality index of the power distribution network in the rural power grid low-voltage transformer area and the control function of the single-phase power quality treatment device;
3) the electric energy quality coordination controller detects the electric energy quality of ABC three phases and sends electric energy quality information to the control circuit, the control circuit controls the on-off of the IGBT switching device, and then the single-phase electric energy quality control device is controlled to control whether to compensate the rural power grid or not, and the optimal control of the electric energy quality of the rural power grid is realized.
In the invention, the control function module required by the single-phase power quality control device is determined by one or more of the following contents:
1) a grid structure of the photovoltaic poverty-alleviation rural net;
2) system parameters of the light poverty-relief rural power grid;
3) the load type of the light poverty-relief rural power grid;
4) the existing electric energy quality problem of the light poverty-relief rural power grid.
In the invention, the content of each power quality index of the distribution network in the rural power grid low-voltage transformer area comprises the following steps: harmonic content and reactive power content of the single-phase electric energy quality control device at a rural power grid access point, three-phase unbalanced content indicated by three-phase load current and maximum power generation power of the rural power grid access poverty-facilitating photovoltaic device.
The harmonic content and the reactive power content of the single-phase power quality control device at the rural power grid access point are obtained through direct measurement or estimation.
The harmonic content of the single-phase power quality control device at the rural power grid access point is estimated through the maximum load capacity of the access point, the total current harmonic distortion rate of the electric equipment and the harmonic compensation rate.
And the reactive power content is estimated through the maximum load active power of each phase and the power factors before and after reactive compensation.
In the invention, the compensating current of the single-phase power quality control deviceWherein, IHHarmonic compensation current, I, required for the harmonic content of a single-phase power quality management device at a rural power grid access pointQReactive compensation current required by the electric energy quality control device aiming at the reactive power content and compensation current I required by three-phase unbalance ，IPAnd the maximum power generation power of the poverty-alleviation photovoltaic device is accessed to the rural power grid, and the required active compensation current is obtained.
Compensation capacity of single-phase power quality control deviceWherein U isNNominal line voltage, I, being the access point of a single-phase power quality management devicePQThe compensation current of the single-phase power quality control device.
In the invention, the voltage of the power supply tail end of the rural power grid is controlled to be 198V to 235V, and when the bus voltage of the access point of the single-phase power quality control device is lower than 205V, the control circuit controls the on-off of the IGBT switching device to enable the energy storage device to start discharging; when the bus voltage of the access point of the single-phase power quality control device is higher than 230V, the control circuit controls the IGBT switching device to be switched on and off, so that the energy storage device starts to charge.
In the invention, when the power quality coordination controller detects that the three-phase current is unbalanced, the power quality coordination controller sends the three-phase unbalanced compensation current index to the control circuit, and then the calculated unbalanced current is distributed to the single-phase power quality control device.
In the invention, when the electric energy quality coordination controller detects that the power supply power factor of the main incoming line of the rural power grid low-voltage transformer area is less than 0.98, the electric energy quality coordination controller sends the reactive compensation current index to the control circuit, and then the calculated reactive compensation current is distributed to the single-phase electric energy quality control device.
The photovoltaic poverty-relief rural power grid electric energy quality optimization device and method based on cooperative autonomy are provided by carrying out comprehensive treatment on the electric energy quality of the photovoltaic poverty-relief rural power grid, can effectively solve the electric energy quality problem of the rural power grid, remarkably improve the electric energy quality operation level of a low-voltage platform area, improve the operation efficiency and economy of a power distribution network, and simultaneously can reduce the cost of electric energy quality construction and reconstruction of the low-voltage platform area; through the autonomous control of the single-phase power quality management device and the cooperative control of the power quality coordination controller, the control of harmonic wave, reactive power, active power, voltage and three-phase unbalance of the low-voltage transformer area is realized, the aim of comprehensively controlling multiple power quality indexes is achieved, the defect of single function of the traditional power quality management device is overcome, the power quality operation level of the low-voltage transformer area is improved, and meanwhile, the cost of building and modifying the power quality of the low-voltage transformer area is reduced.
Drawings
The invention is further described below in conjunction with the appended drawings and the detailed description.
Fig. 1 is a schematic structural diagram of the photovoltaic poverty-alleviation rural power grid electric energy quality optimization device of the invention.
FIG. 2 is a flow chart of the design of a single-phase power quality management device.
Fig. 3 is a parameter calculation flow of the single-phase power quality control device.
Fig. 4 is a flow chart of a cooperative autonomous control strategy of the power quality coordination controller and the single-phase power quality management device.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described below by combining the specific drawings.
The invention aims to solve the problems by providing a photovoltaic poverty-relieving rural power grid electric energy quality optimization device and method based on cooperation autonomy, wherein the photovoltaic poverty-relieving rural power grid electric energy quality optimization device and method are provided by the invention.
Referring to fig. 1, the photovoltaic poverty-alleviation rural power grid electric energy quality optimization device based on cooperative autonomy is applied to a rural power grid with a poverty-alleviation photovoltaic device connected to a low-voltage platform area, and comprises an electric energy quality coordination controller, wherein the electric energy quality coordination controller is connected to the ABC three phases at the total incoming line position of the low-voltage platform area of the rural power grid, detects the electric energy quality of the ABC three phases and sends electric energy quality information, and the electric energy quality information sent by the electric energy quality coordination controller comprises reactive power information and three-phase imbalance information at the total incoming line position of the low-voltage platform. The electric energy quality coordination controller is a signal processing unit and can be composed of hardware and software, wherein the hardware is responsible for preprocessing collected signals, and the software is used for calculating and analyzing the electric energy quality of the preprocessed signals. The main function is to collect the data of the bus voltage and the total incoming line current of the low-voltage transformer area, calculate the unbalanced compensation current and the reactive compensation current and send instructions to the single-phase power quality management device. After the single-phase power quality control device receives the control signal, the single-phase power quality control device sends out the unbalanced current and the reactive current with the specified size, and the purpose of cooperative control of each single-phase power quality control device is achieved.
Compared with the prior art, the invention has the main improvement that a single-phase power quality control device is arranged and exemplarily illustrated by phase A in figure 1, the power quality control device of phase A (single-phase) comprises an inverter circuit and a control circuit which are formed by IGBT switching devices, the direct current side of the inverter circuit is connected with an energy storage device, the energy storage device is arranged for active current control and unbalanced current control, energy storage elements such as a super capacitor and a storage battery can be selected as required by the energy storage device, and a DC/DC converter can be additionally arranged on the direct current side as required by the energy storage elements, so that the full utilization of energy is realized.
The alternating current side of the inverter circuit is connected with one phase line and a zero line in the ABC three phases, and the functions of harmonic filtering, reactive compensation, active control, voltage regulation and three-phase unbalance management are realized through the rapid turn-off and turn-on of an IGBT switching device. The fast turn-off and turn-on of the IGBT switching device are controlled through an A-phase (single-phase) control circuit, specifically, the A-phase (single-phase) control circuit is connected with a phase line and a zero line in ABC three phases connected to the alternating current side of the inverter circuit, the electric energy quality coordination controller sends electric energy quality information, and the A-phase (single-phase) control circuit controls the on-off of the IGBT switching device. The structure of the single-phase power quality control device is similar to that of a single-phase APF or SVG, the on-off of the IGBT can be controlled through PWM modulation, and direct current is converted into current to be compensated (including harmonic current, reactive current, unbalanced current and active current).
In an ideal state, single-phase power quality control devices are arranged on the ABC three phases of the rural power grid, single-phase power quality control devices are also arranged on the B/C phases, and a control circuit of each B/C phase power quality control device is correspondingly connected with one phase and a zero line of the ABC three phases connected to the alternating current side of an inverter circuit of the B/C phase power quality control device, namely at least 3 single-phase power quality control devices are correspondingly connected with each phase line and zero line of the ABC three phases.
Certainly, according to the research result and the power quality control function requirement, in the actual operation, a proper position is selected between the head end and the tail end of each matched power line in the low-voltage station area to install the single-phase power quality control device, the installation position of the power quality control device can ensure the realization of the control function of the single-phase power quality control device, the single-phase power quality control device is preferable in engineering, and the installation position of the single-phase power quality control device is preferably arranged at the position which is far from the main incoming line 1/2 to 2/3 of a power supply circuit of the rural power grid low-voltage.
Referring to fig. 2 to 4, when the photovoltaic poverty-alleviation rural power grid power quality optimization device based on cooperative autonomy performs power quality optimization control, the following modes are adopted:
firstly, a grid structure, system parameters, load types, existing power quality problems and the like of a rural power grid provided with a photovoltaic poverty-alleviation device are investigated, and a control function module required to be possessed by a single-phase power quality control device is determined, wherein the single-phase power quality control device controls the on-off output of an IGBT (insulated gate bipolar transistor) through PWM (pulse-width modulation) modulation and outputs a required current waveform, and the single-phase power quality control device also comprises a controller and controls harmonic waves and active power by detecting the voltage and the current of an access point. However, the problems of three-phase unbalance and overlarge reactive current also exist in the low-voltage distribution network, and the single-phase power quality control device does not have the three-phase unbalance control, so that three-phase voltage and current are detected at the distribution outlet side of a low-voltage transformer area through a coordination controller, the unbalanced current and the reactive current which need to be compensated are calculated, and then a control instruction is sent to each single-phase power quality control device, so that the cooperative control of each single-phase power quality control device is realized, and each single-phase power quality control device can independently control active and harmonic currents;
then, calculating the compensation current or compensation capacity of the single-phase power quality management device according to the content of the power quality index of the power distribution network in the rural power grid low-voltage transformer area and the control function of the single-phase power quality management device; and finally, the power quality coordination controller detects the power quality of the ABC three phases and sends power quality information to the control circuit (if the single-phase power quality control device and the single-phase coordination control are arranged in multiple pairs, the power quality information is sent to the control circuit of each phase), the control circuit controls the on/off of the IGBT switching device of the phase where the single-phase power quality control device is located, and then the control circuit controls whether the single-phase power quality control device compensates the rural power grid or not so as to realize the optimized control of the power quality of the rural power grid.
The most important thing here is how to obtain the content of the power quality index of the distribution network in the rural power grid low-voltage transformer area and how to calculate the compensation current or the compensation capacity of the single-phase power quality control device. Firstly, the content of each power quality index of the distribution network in the rural power grid low-voltage transformer area comprises the following steps: harmonic content and reactive power content of the single-phase electric energy quality control device at a rural power grid access point, three-phase unbalanced content indicated by three-phase load current and maximum power generation power of the rural power grid access poverty-facilitating photovoltaic device.
The harmonic content and the reactive power content of the single-phase power quality control device at the rural power grid access point can be obtained by direct measurement or estimation, wherein when the harmonic content of the single-phase power quality control device at the rural power grid access point is obtained by estimation, the maximum load capacity of the access point, the total harmonic distortion rate and the harmonic compensation rate of the current of the electric equipment can be estimated, and the harmonic compensation current I required by the harmonic content of the single-phase power quality control device at the rural power grid access point is finally obtained by direct measurement or estimationH(ii) a When the reactive power content is obtained through estimation, the reactive power content can be estimated through the maximum load active power of each phase and the power factors before and after reactive power compensation, and similarly, the reactive compensation current I required by the electric energy quality control device for the reactive power content is finally obtained through direct measurement or estimationQ. The three-phase unbalanced content indicated by the three-phase load current is actually calculated directly through the three-phase load current of the low-voltage transformer area, and finally the compensation electricity required by the three-phase unbalance is obtainedStream I (ii) a Finally, acquiring the required active compensation current I based on the maximum power generation power of the rural power grid connected to the poverty-alleviation photovoltaic deviceP。
After the obtaining of the compensation current required by the content of each power quality index is completed, the compensation current of the single-phase power quality control device can be obtained by calculating after the calculation results are summarized, specifically, the compensation currentWhen the compensating current can be converted into the compensating capacity, the compensating capacity of the single-phase power quality control deviceWherein U isNNominal line voltage, I, being the access point of a single-phase power quality management devicePQThe compensation current of the single-phase power quality control device.
Through the setting, the power quality detection point of the single-phase power quality treatment device is arranged at the access point position of the treatment device, and the single-phase power quality treatment device is controlled to carry out autonomous control on harmonic waves, active power and power supply voltage according to the power quality detection result. Each power quality treatment device comprehensively treats each power quality problem of the low-voltage transformer area according to the cooperative autonomous control strategy, and if the power quality problem reaches a control target, the control is finished; and if the control target is not reached, returning to optimize the parameters and the control strategy of the power quality control device until the control target is reached.
For a better presentation of the invention, the following detailed description is given by way of a specific example:
in this example, the head end voltage U of the power supply of the rural power grid low-voltage transformer areaN380V, the capacity of the distribution transformer is 200kVA, the maximum load rate of the transformer is 60 percent, the minimum load rate in the daytime is 10 percent, the average power factor of the load is 0.85, and the low-voltage electric loads are uniformly distributed along the line. Each phase of the low-voltage transformer area is provided with 2 outgoing lines, the length of a power supply line is 1000 meters, and the section of a power distribution lead wireIs 50mm2The equivalent resistance of the distribution line is 0.64 omega/km, the ABC three phases all contain 10-household 3kW poverty-relieving photovoltaic devices, and the maximum power generation power of the distributed photovoltaic devices can reach 60% of the rated power; in the daytime of photovoltaic power generation peak, the voltage at the power supply end can reach 240V, the minimum voltage at the power supply end in the evening power utilization peak can reach 180V, the total harmonic distortion rate of the current can reach 20%, and the three-phase unbalanced current can reach 20% of the rated current. The harmonic current of the compensated access point is required to be completely compensated, the average power factor of the load is not less than 0.98, the voltage at the power supply tail end meets the national standard requirement (198V-235V), and the three-phase power utilization is basically balanced.
According to the basic data:
(1) the total apparent power of the three-phase load at the maximum load rate is as follows:
SLmax＝ST*ηTmax＝200kVA*60％＝120kVA
(2) total active power of three-phase load at maximum load rate:
PLmax＝ST*ηTmax*PF＝200kVA*60％*0.85＝102kW
(3) three-phase load total reactive power at maximum load rate:
(4) single-phase load current at maximum load rate:
(5) single-phase load current at minimum load factor:
(6) total harmonic current content at maximum load factor:
IHmax＝ILmax×THDI＝182.3A×20％＝36.5A
(7) total unbalanced current at maximum load rate:
Imax＝ILmax×20％＝182.3A×20％＝36.5A
(8) single-phase poverty-relief photovoltaic power generation power:
PGFmax＝3kW×10×60％＝18kW
(9) maximum power generation current of single-phase poverty-alleviation photovoltaic power generation:
(10) because the equivalent impedance of the distribution line is 0.64 omega, and the load is uniformly distributed along the line, in order to ensure that the voltage at the power supply end is between 198V and 235V, the current flowing through each matched line should meet the following conditions:i.e., -46.9A. ltoreq.IL-rangeLess than or equal to 68.8A, namely, the maximum forward current of each matched electric line does not exceed 68.8A in the power utilization state; in the power generation state, the maximum reverse current of each matched electric line does not exceed 46.9A.
(11) Under the current operation condition, the maximum forward current I of each matched electric lineLS-Pmax＝ILmax180.3A; maximum reverse current I of each matched electric lineLS-Nmax＝IGFmax-ILmin82.0-30.4A-51.6A, all exceeded the reasonable operating range calculated in (10).
(12) Because the power factor requirement after compensation reaches 0.98, the reactive power required to be compensated is:
wherein,-a compensated power factor angle;-power factor angle before compensation
(13) Because low voltage distribution lines are qualified by 2 lines, install 6 single-phase power quality control devices altogether, because the voltage qualification rate of this district power supply end is lower, in order to effectively improve the voltage qualification rate of power supply end, with power quality control device mounted position in distribution lines '2/3 department, power quality control device each functional module's capacity calculation as follows:
the harmonic control module compensates the current:(note: the harmonic control module only compensates for harmonic currents at the back end of the access point);
the reactive power control module compensates current:
the unbalance control module compensates the current:
the active control module compensates current:
therefore, the load current of the single-phase power quality control device can be calculated as follows:
capacity of the single-phase power quality control device:
(14) the power quality coordination controller and the single-phase power quality treatment device have a coordination autonomous control strategy shown in the attached figure 4. Because the loads are uniformly distributed along the line, and the access point of the single-phase power quality control device is positioned at 2/3 of the distribution line, in order to ensure that the voltage at the power supply end is between 198V and 235V, when the bus voltage of the access point is lower than 205V, the control circuit controls the IGBT switching device to be switched on and off so that the energy storage device starts to discharge; when the bus voltage of the access point is higher than 230V, the control circuit controls the IGBT switching device to be switched on and off so that the energy storage device starts to charge. In order to ensure that the three-phase power utilization is basically balanced, when the coordination controller detects that the three-phase load current is unbalanced, a three-phase unbalanced compensation current index is sent to the power quality control device, and meanwhile, the calculated unbalanced current is distributed to each single-phase power quality control device; in order to ensure that the power supply power factor of the total incoming line of the rural power grid low-voltage transformer area is not less than 0.98, when the coordination controller detects that the power factor of the total incoming line of the rural power grid low-voltage transformer area is less than 0.98, a reactive compensation current index is sent to the power quality device, and meanwhile, the calculated reactive compensation current is distributed to each single-phase power quality control device.
On each phase of distribution line of a rural low-voltage power distribution network containing distributed poverty-alleviation photovoltaic equipment, a single-phase power quality treatment device with harmonic filtering, reactive compensation, unbalanced three phases and active control function modules is respectively installed at a proper position, and through the cooperative autonomous control of the single-phase power quality treatment device and a power quality coordination controller, the control of the unbalanced harmonic, reactive, active, voltage and three phases of the low-voltage power distribution network is realized.
The foregoing is illustrative of the preferred embodiments of the present invention only and is not to be construed as limiting the claims. The present invention is not limited to the above embodiments, and the specific structure thereof is allowed to vary. In general, all changes which come within the scope of the invention as defined by the independent claims are intended to be embraced therein.
Claims (10)
1. Photovoltaic poverty-alleviation rural power grid electric energy quality optimization device based on cooperative autonomy is applied to the rural power grid that the low-voltage platform district is connected with poverty-alleviation photovoltaic device, and its characterized in that includes:
the electric energy quality coordination controller is connected with the ABC three phases at the main incoming line position of the rural power grid low-voltage transformer area, detects the electric energy quality of the ABC three phases and sends the electric energy quality information;
the single-phase electric energy quality treatment device comprises an inverter circuit and a control circuit, wherein the inverter circuit and the control circuit are formed by IGBT switching devices, an energy storage device is connected to the direct current side of the inverter circuit, a phase line and a zero line in ABC three phases are connected to the alternating current side of the inverter circuit, one phase and the zero line in the ABC three phases are connected to the control circuit and the alternating current side of the inverter circuit, electric energy quality information of an access point is detected, and meanwhile, the electric energy quality information sent by the electric energy quality coordination controller is received to control the IGBT switching devices to output current.
2. The photovoltaic poverty-alleviation rural power grid electric energy quality optimization device based on cooperative autonomy as claimed in claim 1, characterized in that: the number of the single-phase power quality control devices is at least 3, and the single-phase power quality control devices are respectively and correspondingly connected with each phase and a zero line in the ABC three phases.
3. The photovoltaic poverty-alleviation rural power grid electric energy quality optimization device based on cooperative autonomy as claimed in claim 1, characterized in that: the single-phase power quality treatment device is arranged at a position which is away from a main incoming line 1/2 to 2/3 from a power supply line of a rural power grid low-voltage transformer area.
4. The photovoltaic poverty-alleviation rural power grid electric energy quality optimization device based on cooperative autonomy as claimed in claim 1, characterized in that: and the electric energy quality coordination controller detects and sends electric energy quality information including reactive power information and three-phase imbalance information.
5. The photovoltaic poverty-alleviation rural power grid electric energy quality optimization method based on cooperative autonomy adopts the photovoltaic poverty-alleviation rural power grid electric energy quality optimization device based on cooperative autonomy in any one of claims 1 to 4, and is characterized by comprising the following steps:
1) determining a control function module which is required to be possessed by the single-phase power quality management device;
2) calculating the compensation current or the compensation capacity of the single-phase power quality treatment device according to the content of the power quality index of the power distribution network in the rural power grid low-voltage transformer area and the control function of the single-phase power quality treatment device;
3) the electric energy quality coordination controller detects the electric energy quality of ABC three phases and sends electric energy quality information to the control circuit, the control circuit controls the on-off of the IGBT switching device, and then the single-phase electric energy quality control device is controlled to control whether to compensate the rural power grid or not, and the optimal control of the electric energy quality of the rural power grid is realized.
6. The photovoltaic poverty-alleviation rural power grid electric energy quality optimization method based on cooperative autonomy as claimed in claim 5, characterized in that: the control function module that single-phase power quality governs device needs to possess is confirmed through one or more than one combination of following content:
1) a grid structure of the photovoltaic poverty-alleviation rural net;
2) system parameters of the light poverty-relief rural power grid;
3) the load type of the light poverty-relief rural power grid;
4) the existing electric energy quality problem of the light poverty-relief rural power grid.
7. The photovoltaic poverty-alleviation rural power grid electric energy quality optimization method based on cooperative autonomy as claimed in claim 5, characterized in that: the content of each electric energy quality index of rural power grids low-voltage transformer district distribution network includes: harmonic content and reactive power content of the single-phase electric energy quality control device at a rural power grid access point, three-phase unbalanced content indicated by three-phase load current and maximum power generation power of the rural power grid access poverty-facilitating photovoltaic device.
8. The photovoltaic poverty-alleviation rural power grid electric energy quality optimization control method based on cooperative autonomy as claimed in claim 7, characterized in that: the harmonic content and the reactive power content of the single-phase power quality management device at the rural power grid access point are obtained through direct measurement or estimation;
or the harmonic content of the single-phase power quality control device at the rural power grid access point is estimated through the maximum load capacity of the access point, the total current harmonic distortion rate and the harmonic compensation rate of the electric equipment;
or estimating the reactive power content through the maximum load active power of each phase and the power factors before and after reactive compensation.
9. The photovoltaic poverty-alleviation rural power grid electric energy quality optimization method based on cooperative autonomy as claimed in claim 1, characterized in that: compensation current of single-phase electric energy quality control deviceWherein, IHHarmonic compensation current, I, required for the harmonic content of a single-phase power quality management device at a rural power grid access pointQReactive compensation current required by the electric energy quality control device aiming at the reactive power content and compensation current I required by three-phase unbalance ，IPThe maximum power generation power of the poverty-alleviation photovoltaic device is accessed to the rural power grid, and the required active compensation current is obtained;
compensation capacity of single-phase power quality control deviceWherein U isNNominal line voltage, I, being the access point of a single-phase power quality management devicePQThe compensation current of the single-phase power quality control device.
10. The photovoltaic poverty-alleviation rural power grid electric energy quality optimization method based on cooperative autonomy as claimed in claim 1, characterized in that: the voltage of the power supply tail end of the rural power grid is controlled to be 198V to 235V, and when the bus voltage of the access point of the single-phase power quality control device is lower than 205V, the control circuit controls the IGBT switching device to be switched on and off, so that the energy storage device starts to discharge; when the bus voltage of the access point of the single-phase power quality control device is higher than 230V, the control circuit controls the IGBT switching device to be switched on and off, so that the energy storage device starts to charge;
or when the power quality coordination controller detects that the three-phase current is unbalanced, the three-phase unbalanced compensation current index is sent to the control circuit, and then the calculated unbalanced current is distributed to the single-phase power quality control device.
Or when the power quality coordination controller detects that the power supply power factor of the main incoming line of the rural power grid low-voltage transformer area is less than 0.98, the power quality coordination controller sends a reactive compensation current index to the control circuit, and then the calculated reactive compensation current is distributed to the single-phase power quality control device.
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