CN101719679B - Method for synchronizing distributed power supply and power grid - Google Patents
Method for synchronizing distributed power supply and power grid Download PDFInfo
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Abstract
The invention discloses a method for synchronizing a distributed power supply and a power grid and particularly relates to a method for solving voltage fluctuation in the connection of the distributed power supply to the power grid. In the method, a detection module contrasts the voltages of the distributed power supply and the power grid, the power grid is connected to if the voltage difference is within an error range, and the value of the voltage value needed to be regulated is calculated, the output of a grid-connected inverter is regulated and the distributed power supply can be connected to the power grid if the voltage difference is beyond the error range. The method realizes the seamless combination of a distributed power supply system and the power grid and the quick and accurate detection of the frequencies, amplitudes and phases of the voltages of the distributed power supply system and the power grid, and when a grid connection condition is met, accurately sends a grid connection signal to realize seamless and quick grid connection. The alternating current of the grid-connected inverter is used as a grid connection feedback signal and the output current of the grid-connected inverter is made as close to zero as possible to prevent overcurrent faults from appearing before grid connection, so equipment is protected.
Description
Technical field
The present invention relates to a kind of electric power system control method, be specifically related to solve when a kind of distributed power source is connected to the grid the method for voltage fluctuation.
Background technology
Along with the development of the regenerative resources such as photovoltaic/wind power generation, distributed power source obtains increasingly extensive application; The effect of distributed power generation power supply is that solar energy, wind energy, chemical energy etc. are converted into electric energy, and the electric energy form that obtains after the different energy is changed is different; The electric energy that obtains after by power conversion such as, systems such as photovoltaic generation, fuel cell is the direct current form, and the electric energy that the systems such as wind power generation, little gas turbine obtain is form of communication.Combining inverter is the important component part of distributed power generation grid-connected system, its effect is that direct current is converted into alternating current, and the alternating current that conversion is obtained can satisfy with line voltage with frequently, the same width of cloth, the requirement of being incorporated into the power networks of homophase, in addition, combining inverter also should have very high validity and reliability, to guarantee grid-connected system, the safety of local load and electrical network, when being incorporated into the power networks, combining inverter is converted to the direct current form that is applicable to grid-connected inverters with the output of these distributed power sources usually, by adjusting dc voltage, make voltage reach the scope that inverter can work, but the scope in the at present adjustment of combining inverter can not adapt to electrical network, usually electrical network is caused over current fault and vibration.
Summary of the invention
Excessive for solving in the prior art distributed power grid time-harmonic wave that is connected to the grid, cause the problem of over current fault, the invention provides and a kind ofly seamlessly be incorporated into the power networks, can suppress Yin Maoci and the frequent saltus step that causes and the method for vibration.Concrete steps are as follows: the method for synchronous of a kind of distributed power source and electrical network, the distributed power source, combining inverter, output filter, isolating transformer and the static switch that comprise connection, distributed power source 1 is interchange by combining inverter 2 inversions, behind output filter 3, by isolating transformer 4 by static switch 5 feed-in electrical networks, it is characterized in that, be connected with detection module between combining inverter and the electrical network, described detection module is carried out following steps:
The output voltage values of distributed power source and the output current value of combining inverter are obtained in A, (1);
(2) obtain the magnitude of voltage of electrical network;
B, distributed power source output voltage values and line voltage value are calculated, obtain the voltage comparison value between distributed power source and the line voltage,
(1) the voltage comparison value is then connected static switch and is connected to the grid in default error range;
(2) the voltage comparison value then disconnects the adjusted in concert step that static switch changes C over to outside default error range;
C, the electric current comparison value of voltage comparison value and distributed power source is regulated the voltage synchronization value that obtains combining inverter after the conversion, wherein, the electric current comparison value obtains after being compared by the output current value of combining inverter and preset value;
D, to utilize the voltage synchronization value of C to regulate the output of combining inverter consistent with electrical network, then connects static switch and be connected to the grid.
Another optimal way of the present invention: the magnitude of voltage of distributed power source obtains by the Park conversion by the Clarke conversion first again among the described A.
Another optimal way of the present invention: the magnitude of voltage of electrical network obtains by the Park conversion by the Clarke conversion first again among the described A.
Another optimal way of the present invention: the combining inverter output current value passes through the Park conversion again through the Clarke conversion first among the described C, obtain the distributed power source output current value under the rotational coordinates, after output current value and electric current preset value calculated, obtain the electric current comparison value.
Another optimal way of the present invention: described voltage synchronization value adopts following step to obtain:
(1) electric current comparison value and voltage comparison value are regulated through pi regulator respectively after, calculate again feedback signal,
(2) output voltage values of feedback signal and distributed power source calculate after as the voltage given value,
(3) the voltage given value is passed through first the Park inverse transformation, passes through the Clarke inverse transformation again,
(4) pass through again the driving signal that pulse width modulator obtains the combining inverter power tube.
Another optimal way of the present invention: wherein: described phase angle theta adopts three-phase phase-locked loop to obtain.
The method for synchronous of distributed power source provided by the invention and electrical network, realized the seamless combination of distributed power supply system and electrical network, to the quick and precisely detection of frequency, amplitude and the phase place of both sides' voltage, when the condition of being incorporated into the power networks satisfies, send accurately the signal that is incorporated into the power networks, realize seamlessly being incorporated into the power networks fast.The present invention is corresponding with two-dimensional coordinate with three-dimensional coordinate, obtains phase angle theta, according under the rotational coordinates relatively dq axle value obtain a difference, this difference and preset value relatively if satisfy the condition that is incorporated into the power networks then trigger the thyristor of static switch, are realized seamless being incorporated into the power networks.The alternating current that utilizes combining inverter is as being incorporated into the power networks feedback signal, and to make the combining inverter output current be 0 as far as possible, avoided over current fault occurring before being incorporated into the power networks, thereby protected equipment.The electrical network phase angle theta adopts three-phase phase-locked loop to realize, the preferably ability of real-time tracking electrical network three-phase voltage frequency and phase place is arranged, dynamically and static characteristic good.
Description of drawings
Fig. 1 distributed power source schematic diagram that is connected to the grid
The rotational coordinates schematic diagram that Fig. 2 two-dimensional coordinate and three-dimensional coordinate stack form
Fig. 3 schematic flow sheet of the present invention
Fig. 4 the present invention asks the phase angle theta circuit diagram
Embodiment
The present invention mainly comprises the detection of line voltage, the detection of combining inverter 2 output voltages, the detection of combining inverter 2 output currents, the dq conversion of line voltage and combining inverter output voltage, the dq conversion of combining inverter output current, and by phase-locked loop (Phase Locked Loop, PLL) the electrical network phase angle theta that obtains, when not being incorporated into the power networks, the deviation of the dq conversion by detection of grid voltage and combining inverter output voltage determines whether to satisfy the condition that is incorporated into the power networks, the dq reference value that electric current loop is set simultaneously is 0, avoiding occurring over current fault, realizes accurately being incorporated into the power networks safely and fast of distributed power source.
This method is obtained first the output voltage values of distributed power source 1 and electrical network, as shown in Figure 1, the connection diagram of distributed power source 1 and electrical network, mainly comprise distributed power source 1, combining inverter 2, output filter 3, isolating transformer 4, static switch 5 and detection module 6, distributed power source 1 output current passes through isolating transformer 4 by static switch 5 feed-in AC network through output filter 3 after being interchange by combining inverter 2 inversions.
As shown in Figure 3, detection module 6 mainly comprises voltage, current acquisition and Clarke7, Park8 conversion, line voltage and comparison, analog switch 11, hysteresis loop comparator 10 and the signal that is incorporated into the power networks of combining inverter voltage, anti-Clarke, Park conversion and the PWM pulse-width modulation 9 under rotating coordinate system of distributed power source and electrical network.And network process in, output three-phase voltage and electrical network three-phase voltage with combining inverter 2 passes through first respectively the Clarke7 conversion first, pass through again the Park8 conversion, the coordinate transforming relation of Clarke and Park as shown in Figure 2, obtain distributed power source magnitude of voltage Ud_m, Uq_m and line voltage value Ud_g, Uq_g under the rotational coordinates after the conversion, wherein Clarke and Park transformation for mula are as follows:
The Clarke transformation for mula:
The Park transformation for mula:
V
d＝V
α*cos(θ)+V
β*sin(θ)
V
q＝-V
α*sin(θ)+V
β*cos(θ)
Distributed power source 1 magnitude of voltage Ud_m, the Uq_m and line voltage value Ud_g, the Uq_g that draw are compared, obtain voltage comparison value Δ Ud and Δ Uq, this voltage comparison value compares through threshold value default in hysteresis loop comparator 10 and the analog switch 11 respectively, if within default scope then output " 1 ", otherwise output " 0 ", with the output logic value of Δ Ud and Δ Uq carry out again with, with the logical value of door output as judging whether to satisfy the condition that is incorporated into the power networks.
In this method logical signal " 1 " is made as and satisfies the condition that is incorporated into the power networks, hysteresis loop comparator 10 sends corresponding closure signal to static switch 5, close simultaneously analog switch 11, analog switch is the passage of distributed power source 1 and line voltage error signal, after static switch 5 closures, to not need this two error signals, and namely not need to adjust synchronously, after distributed power source directly is connected to the grid.
Logical signal " 0 " is made as the dissatisfied condition that is incorporated into the power networks, hysteresis loop comparator 10 sends corresponding cut-off signal to static switch 5, and simultaneously conducting analog switch 11 needs to regulate output voltage and the phase place thereof of combining inverter 1 this moment, with consistent with electrical network, thereby reach the condition of being incorporated into the power networks.Detection module 6 is with output current process Clarke and the Park conversion of combining inverter 1, obtain distributed power source output current value Id_m and Iq_m under the rotational coordinates, the front current reference value Idref=0 if distributed power source is incorporated into the power networks, Iqref=0, to regulate the combining inverter output current as 0, over current fault occurs and damage equipment before can avoiding being incorporated into the power networks, then current value I d_m and Iq_m and current reference value Idref, Iqref are compared, obtain electric current comparison value Δ Id and Δ Iq.
Obtain feedback signal Ud_feedback behind the voltage comparison value Δ Ud process pi regulator A12 with behind the electric current comparison value Δ Id process pi regulator C14, obtain feedback signal Uq_feedback behind the voltage comparison value Δ Uq process pi regulator B13 with behind the electric current comparison value Δ Iq process pi regulator D15, with feedback signal Ud_feedback and Uq_feedback and distributed power source output voltage values Ud_m, the relatively rear voltage given value as combining inverter of Uq_m, the voltage given value is passed through first the Park conversion, pass through again the Clarke conversion, then obtained the voltage synchronization value of combining inverter by PWM pulse-width modulation 9, the voltage synchronization value that obtain this moment is the concrete voltage data that combining inverter need to be adjusted.
When carrying out Park conversion and inverse transformation, line voltage and combining inverter output voltage and current signal all to use phase angle theta, there are various methods can obtain phase angle theta in the prior art, but all there are some defectives, such as crossing the zero balancing phase-locked loop, it calculates phase place by detecting zero crossing.Because zero crossing only occurs once in every half period, point-to-point transmission can not obtain phase information, and zero crossing disturbs very responsively to harmonic wave, asymmetric etc., so the testing result that obtains, its static and dynamic performance is poor, and error is large; Another kind is under static rotating coordinate system U α _ g and U β _ g to be carried out the arc tangent conversion also can obtain phase angle theta, and this detection method detects than zero crossing and improves to some extent, but need to design preferably filter in the time of power network fluctuation; As shown in Figure 4, the angle theta of α axle and d axle is that three-phase phase-locked loop obtains among the present invention, it is tried to achieve according to rotating coordinate system, phase-locked realization realizes by setting d shaft voltage reference value Udref=0, with actual Ud output valve Ud_error relatively by the angular frequency that pi regulator E obtains electrical network, can obtain the electrical network phase angle theta through integrator again.
Claims (5)
1. the method for synchronous of a distributed power source and electrical network, the distributed power source (1), combining inverter (2), output filter (3), isolating transformer (4) and the static switch (5) that comprise connection, distributed power source (1) is interchange by combining inverter (2) inversion, behind output filter (3), by isolating transformer (4) by static switch (5) feed-in electrical network, it is characterized in that, be connected with detection module (6) between combining inverter and the electrical network, described detection module is carried out following steps:
The output voltage values of distributed power source and the output current value of combining inverter are obtained in A, (1);
(2) obtain the magnitude of voltage of electrical network;
B, distributed power source output voltage values and line voltage value are carried out subtraction, obtain the voltage comparison value between distributed power source and the line voltage,
(1) the voltage comparison value is then connected static switch and is connected to the grid in default error range;
(2) the voltage comparison value then disconnects the adjusted in concert step that static switch changes C over to outside default error range;
C, the electric current comparison value of voltage comparison value and distributed power source is regulated the voltage synchronization value that obtains combining inverter after the conversion, wherein, the electric current comparison value is undertaken obtaining behind the subtraction by output current value and the preset value of combining inverter;
D, to utilize the voltage synchronization value of C to regulate the output of combining inverter consistent with electrical network, then connects static switch and be connected to the grid.
2. method for synchronous as claimed in claim 1 is characterized in that, the magnitude of voltage of distributed power source obtains by the Park conversion by the Clarke conversion first again among the described A.
3. method for synchronous as claimed in claim 1 is characterized in that, the magnitude of voltage of electrical network obtains by the Park conversion by the Clarke conversion first again among the described A.
4. method for synchronous as claimed in claim 1, it is characterized in that, the combining inverter output current value passes through the Park conversion again through the Clarke conversion first among the described C, obtain the distributed power source output current value under the rotational coordinates, after output current value and electric current preset value calculated, obtain the electric current comparison value.
5. method for synchronous as claimed in claim 4 is characterized in that, described voltage synchronization value adopts following step to obtain:
(1) electric current comparison value and voltage comparison value are regulated through pi regulator respectively after, calculate again feedback signal,
(2) output voltage values of feedback signal and distributed power source carries out after the subtraction as the voltage given value,
(3) the voltage given value is passed through first the Park inverse transformation, passes through the Clarke inverse transformation again,
(4) pass through again the driving signal that pulse width modulator obtains the combining inverter power tube.
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| CN102480243B (en) * | 2010-11-29 | 2015-05-27 | 比亚迪股份有限公司 | Direct current component control method and system used for three-phase or single-phase inverter |
| EP2632012B1 (en) * | 2012-02-22 | 2016-02-17 | Siemens Aktiengesellschaft | Method for synchronising a feed-in voltage with a mains voltage |
| US9379551B2 (en) * | 2012-08-10 | 2016-06-28 | General Electric Company | Methods and systems for controlling a power converter |
| CN103267897B (en) * | 2013-05-15 | 2015-04-08 | 电子科技大学 | Three-phase-locked loop based on reversed Park conversion |
| CN103336550B (en) * | 2013-05-22 | 2015-01-07 | 广西电网公司 | Photovoltaic power generation maximum power point tracing method and maximum power point tracing controller |
| CN103414211A (en) * | 2013-08-09 | 2013-11-27 | 泰豪科技股份有限公司 | Method for detecting synchronization of distributed power supply and power grid |
| CN103840485B (en) * | 2014-02-28 | 2015-02-25 | 山东大学 | Global synchronization pulse width modulation system and method of distributed grid-connected inverter system |
| CN104104114B (en) * | 2014-07-31 | 2017-06-16 | 阳光电源股份有限公司 | A kind of control method and system for solving grid-connected dash current |
| US10181728B2 (en) * | 2016-03-22 | 2019-01-15 | General Electric Company | Smart grid synchronization scheme |
| CN111130144B (en) * | 2019-12-13 | 2021-11-19 | 华南理工大学广州学院 | Small hydropower station quick grid connection method considering deviation and trend change |
| CN111130143B (en) * | 2019-12-13 | 2021-09-21 | 华南理工大学广州学院 | Small hydropower station rapid synchronization method for directly comparing voltage sampling values |
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