CN112531774A - Low-voltage ride-through operation control method of inverter type distributed power supply - Google Patents

Low-voltage ride-through operation control method of inverter type distributed power supply Download PDF

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CN112531774A
CN112531774A CN202011380319.3A CN202011380319A CN112531774A CN 112531774 A CN112531774 A CN 112531774A CN 202011380319 A CN202011380319 A CN 202011380319A CN 112531774 A CN112531774 A CN 112531774A
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voltage
grid
power supply
power
current
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楚天丰
闫振宏
王同
张武洋
宋保全
付钰惠
黄未
王英明
李伟
朱天翼
东方
周佳旭
李鹏里
田丰源
刘梦夏
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Liaoning Dongke Electric Power Co Ltd
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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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • 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
    • H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/40—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

A low voltage ride through operation control method of an inverter type distributed power supply is used for separating and transforming collected data and then judging; and giving different measures based on different judgment results, and directly cutting off the distributed power supply under the condition that the low-voltage ride through characteristic curve is not met. For the condition of meeting the low voltage ride through characteristic curve, further judging the voltage drop degree, directly using the conventional control strategy of the voltage outer ring current inner ring when the voltage drop is not more than 10%, for the condition of exceeding 10%, adopting a low voltage ride through operation control method, disconnecting the voltage outer ring, carrying out classification processing based on the voltage drop degree, giving different voltage drop degrees to adjust the reference value of reactive power, and finally setting the active current reference value according to the reactive current reference value and the bearing capacity of the device. The invention can flexibly transmit reactive power to the power grid under the condition of unbalanced power grid, and realizes the stable operation of low voltage ride through of the power grid.

Description

Low-voltage ride-through operation control method of inverter type distributed power supply
Technical Field
The invention belongs to the field of new energy grid-connected control, and particularly relates to low-voltage ride-through operation control.
Background
With the continuous improvement of the permeability of the photovoltaic grid-connected power generation system, the influence of the permeability on the transient stability of the power grid is larger and larger, when the power grid fails and voltage drops, the transient stability of the power grid can be seriously influenced by the off-grid of the photovoltaic system, and even a large-area power failure accident is caused by a chain reaction. Therefore, the photovoltaic power generation system needs to have a Low Voltage Ride Through (LVRT) capability as a conventional generator, and support the grid Voltage after a fault occurs.
When an asymmetric fault occurs in a power grid, a negative sequence component in the voltage of the power grid can enable a second harmonic component to exist in active power and reactive power output by an inverter, the stability of a grid-connected system can be seriously influenced, in order to eliminate the influence of a negative sequence component of the voltage of the power grid side on the grid-connected system, the negative sequence component of output current of the grid-connected inverter is taken as a control target in the traditional positive and negative sequence double-loop control method, a reference value of negative sequence current under a dq axis is set to be zero, a reference value of positive sequence current under the dq axis is set according to a power expression under an unbalanced power grid, an outer loop adopts voltage control, the output of the outer loop corresponds to the input of an inner loop of the positive sequence current, and meanwhile, in order to realize independent regulation of the. The positive and negative sequence double-loop control method taking the negative sequence current suppression as the control target can enable the current voltage at the point of the common coupling to have no negative sequence component, and further improve the stability of the grid-connected system. However, according to the latest grid connection regulation, when a grid fails, the inverter type distributed power supply is required to provide certain reactive power to the grid to support the grid voltage, so as to realize low voltage ride through, but the traditional positive and negative sequence double-loop control method does not consider this point, but adopts unit power factor control, and cannot deliver reactive power to the grid.
In order to solve the problem that the control method cannot transmit reactive power to a power grid, most control methods can directly control active power and reactive power output by an inverter according to the voltage drop condition of a public coupling point, and the method can effectively inhibit second harmonic in the output power of the inverter, but neglects the imbalance condition of grid-connected current. Other control methods adopt a proportional resonance control method to achieve the purpose of outputting reactive power, but the proportional resonator is difficult to achieve an ideal state, so the method is not strong in practicability.
Disclosure of Invention
The invention provides a low voltage ride through operation control method of an inverter type distributed power supply, which can well solve the technical problem of poor unbalanced current suppression effect in the prior art by controlling reactive power by adjusting reactive current. According to the invention, different reactive current reference values are set according to the voltage drop condition of the public coupling point, so that the required reactive power is transmitted to the power grid, and the more serious the fault degree of the power grid is, the more the required reactive power is transmitted to the power grid. Meanwhile, in order to reduce the loss of active power as much as possible, certain reactive power is ensured to be output, and the maximum active current is output as much as possible. According to the control method, the reactive power can be flexibly transmitted to the power grid under the condition of unbalanced power grid, and the low-voltage ride through stable operation of the power grid is realized.
In order to achieve the purpose, the invention adopts the following technical scheme:
a low voltage ride through operation control method of an inverter type distributed power supply comprises the following steps:
step 1: voltage drop detection is carried out on the voltage of the grid-connected point of the inverter type distributed power supply;
step 2: judging the voltage drop condition based on the voltage drop value detected in the step 1, and immediately cutting off the distributed power supply from the power distribution network when the voltage of the power distribution network accessed by the inverter type distributed power supply is in an area below a low-voltage ride-through characteristic curve of the inverter type distributed power supply;
and step 3: judging the voltage drop condition based on the voltage drop value detected in the step 1, and when the voltage of a power distribution network accessed by the inverter type distributed power supply is in an area above a low-voltage ride-through characteristic curve of the inverter type distributed power supply, keeping the inverter type distributed power supply to be in grid-connected operation all the time;
step 3.1: when the power grid has asymmetric faults, in a synchronous rotation dq coordinate system, positive and negative sequence components of the power grid voltage are respectively subjected to directional control, and output negative sequence current components of the inverter type distributed power supply are suppressed;
step 3.2: when the inverter type distributed power supply is always kept in grid-connected operation, the inverter type distributed power supply is controlled by adopting a low-voltage ride through control method, and in the control process, the inverter type distributed power supply outputs active power by adjusting reactive current according to the grid-connected requirement on the premise of ensuring the safe operation of the inverter type distributed power supply, so that the active power of a power grid is kept in a balanced state.
In the step 1, the voltage drop detection method specifically includes:
step 1.1: firstly, positive and negative sequence component separation is carried out on the collected voltage of the power grid: separating the positive sequence and the negative sequence of the current output by the inverter and the grid-connected point voltage by adopting a T/4 time delay algorithm, and under an alpha-beta coordinate system, the power grid voltage U on an alpha axis and a beta axis at the moment Tα(t)、Uβ(t) can be expressed as:
Figure BDA0002809169610000021
wherein the content of the first and second substances,
Figure BDA0002809169610000022
representing the positive sequence component of the grid voltage on the alpha axis at time t,
Figure BDA0002809169610000023
representing the negative sequence component of the grid voltage on the alpha axis at time t,
Figure BDA0002809169610000024
representing the positive sequence component of the grid voltage on the beta axis at time t,
Figure BDA0002809169610000025
representing the negative sequence component of the grid voltage on the alpha axis at time t;
Figure BDA0002809169610000026
wherein, U1Representing the magnitude, theta, of the positive sequence component of the mains voltage+Initial phase, U, representing positive sequence component of grid voltage2Indicating electricityAmplitude of negative sequence component of grid voltage, theta-Representing the initial phase of the negative sequence component of the power grid voltage;
by substituting formula (2) into formula (1)
Figure BDA0002809169610000031
To the network voltage Uα(t)、Uβ(T) the delay T/4 can be obtained according to the above process:
Figure BDA0002809169610000032
from the above formulas (3) and (4), it is possible to obtain
Figure BDA0002809169610000033
Is represented by the formula (1);
Figure BDA0002809169610000034
step 1.2: respectively converting the alpha-axis component and the beta-axis component of the positive and negative sequence voltage of the power grid obtained in the step 1.1 into a positive and negative sequence dq coordinate system, and sequentially calculating the positive sequence component of the d axis of the power grid voltage
Figure BDA0002809169610000035
And negative sequence component
Figure BDA0002809169610000036
Positive sequence component of q-axis
Figure BDA0002809169610000037
Negative sequence component of q-axis
Figure BDA0002809169610000038
Figure BDA0002809169610000039
Figure BDA00028091696100000310
Step 1.3: and (3) carrying out low-pass filtering processing on the data obtained in the step (1.2) to obtain a required direct current component, carrying out Fourier calculation on the processed three-phase sequence direct current component to obtain an effective value and a phase angle of each sequence component, and carrying out inverse pseudo-gram transformation on the finally obtained phase angle to obtain the voltage amplitude and phase jump condition of each phase.
In the step 3.1), the specific method is as follows:
step 3.1.1: and (3) based on the d-axis and q-axis components of the positive and negative sequence voltages of the power grid obtained in the step 1.2, showing the positive and negative sequence voltage complex vectors of the power grid in a dq coordinate system:
Figure BDA0002809169610000041
according to the complex vector model relation of the inverter distributed power supply in the alpha beta coordinate system:
Figure BDA0002809169610000042
correspondingly obtaining a mathematical model of the positive sequence and the negative sequence of the distributed power supply under a synchronous rotation dq coordinate system:
Figure BDA0002809169610000043
the three-phase instantaneous active power and reactive power output by the inverter type distributed power supply are determined by the three-phase voltage of a grid-connected point and the input power grid current of the distributed power supply, based on the concepts of the active power and the reactive power, the active power p can be expressed as the dot product of the voltage and the current of the power grid, the reactive power q is expressed as the cross product of the voltage and the current of the power grid, and the three-phase instantaneous active power and the reactive power are expressed in the following forms:
Figure BDA0002809169610000044
simplification thereof can lead to the following formula:
Figure BDA0002809169610000045
in the formula p0Is the average value of active power, q0Is the average value of the reactive power, p1Is the amplitude of the cosine second harmonic of the active power, q1Is the amplitude, p, of the cosine second harmonic of the reactive power2Is the amplitude, q, of the sinusoidal second harmonic of the active power2The amplitude of the reactive power sine second harmonic wave; from the above, it is found that when the power grid has an asymmetric fault, both the active power and the reactive power output by the distributed power supply contain second harmonics, and p can be obtained according to the above formula0、q0、p1、q1、p2、q2The corresponding expression:
Figure BDA0002809169610000046
based on directional vector control principle of power grid voltage
Figure BDA0002809169610000047
Equation (12) is simplified to one step:
Figure BDA0002809169610000051
step 3.1.2: the reference values of the negative-sequence current components in the dq coordinate system are each assigned to 0, i.e.:
Figure BDA0002809169610000052
step 3.1.3: the reference value in dq coordinate system of the positive sequence current component is solved according to the step 3.1.1 power expression and step 3.1.2 negative sequence current component reference value in dq coordinate system, that is:
Figure BDA0002809169610000053
the distributed power inverter is controlled by adopting a structural form of a voltage outer ring and a current inner ring, the voltage outer ring adopts a PI (proportional integral) regulator, and the output of the PI regulator corresponds to the input of a positive sequence current inner ring:
Figure BDA0002809169610000054
when low voltage ride through is not considered, the distributed power inverter adopts unit power control, namely q is ordered0And (5) calculating a reference value without considering the active and reactive components of the positive sequence current and the negative sequence current in the low voltage ride through, wherein the reference value is as follows:
Figure BDA0002809169610000055
in the step 3.2), the specific method comprises the following steps:
step 3.2.1: based on the requirement of low voltage ride through of the inverter type distributed power supply, when the per unit value of the grid-connected positive sequence voltage of the power distribution network fault is greater than 0.9, the distributed power supply is enabled to only output constant active power, and a normal control mode is kept, namely the distributed power supply is enabled to output constant active power
Figure BDA0002809169610000056
Step 3.2.2: when the per unit value of the grid-connected positive sequence voltage of the power distribution network is [0.2, 0.9], at least 2% of reactive current is provided when the positive sequence voltage drops by 1%; firstly, disconnecting the voltage outer ring, then adaptively adjusting an instruction of reactive current based on the voltage of the power grid at the moment, and finally directly giving an instruction of active current according to the bearing capacity borne by the distributed power supply inverter;
when the per unit value of the grid-connected positive sequence voltage of the power distribution network fault is [0, 0.2], the distributed power supply does not output active power and outputs the maximum allowable short-circuit current flowing through the transformer, namely the reactive current of 2 times of rated current; firstly, a voltage outer ring is disconnected, then a reactive current instruction is adaptively adjusted based on the voltage of the power grid at the moment, and finally an active current instruction is directly given according to the bearing capacity borne by the distributed power supply inverter;
step 3.2.3: when a short-circuit fault occurs in a power grid, reference values of corresponding positive and negative sequence current components are increased, but the reference values are not infinitely increased under the limitation of short-circuit current, and a boundary solution equation can be obtained:
Figure BDA0002809169610000061
calculating the boundary voltage to enable the output active current of the distributed power supply to just reach the convenient constraint condition;
Figure BDA0002809169610000062
when the per unit value of the positive sequence voltage is [0.54, 0.9), the distributed power supply meets the margin output active power under the condition that the reactive power can be output preferentially;
when the per unit value of the positive sequence voltage is [0.2, 0.54), the distributed power supply cannot meet the margin output active power, so the finally calculated positive sequence negative sequence current active and reactive reference value is as follows:
Figure BDA0002809169610000063
the beneficial effects created by the invention are as follows: according to the low voltage ride through operation control method of the inversion type distributed power supply, dq conversion is not directly performed on the collected physical quantity, positive and negative sequence components are obtained after positive and negative sequence separation is performed, and then dq conversion is performed independently. The positive and negative sequence separation adopts a T/4 time delay algorithm, the separation of the positive sequence component and the negative sequence component of the voltage and the current is realized only by a mathematical extrapolation mode, the order of a control system is not increased, and the stability of the control system is not basically influenced. The scheme can effectively solve the problems in the detection of the voltage drop characteristic quantity by the dq conversion method. The method has the greatest characteristic that the influence of the negative sequence component under the asymmetric fault on the dq method can be effectively avoided. The invention adopts a control method that the positive sequence component and the negative sequence component of the grid voltage are respectively oriented in a positive sequence synchronous rotation dq coordinate system and a negative sequence synchronous rotation dq coordinate system, and mainly directly inhibits the negative sequence component when the grid has an asymmetric fault, so that the current only contains the positive sequence component, and the problems that the current quality is asymmetric and the electric energy quality is influenced are effectively avoided.
Drawings
Fig. 1 is a graph of the low voltage ride through characteristic of the inverter-type distributed power supply in the context of the present invention;
fig. 2 is a block diagram of an inverter-type distributed power inverter current inner loop control system in the context of the present invention;
FIG. 3 is a flow chart of a low voltage ride through control method in accordance with the teachings of the present invention;
fig. 4 is a block diagram of an inverter-type distributed power supply accessing a power distribution network in an embodiment of the present invention;
fig. 5 is a block diagram of a control structure of the entire inverter-type distributed power grid-connected inverter in the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments.
The overall flow is shown in fig. 3.
A low voltage ride through operation control method of an inverter type distributed power supply comprises the following steps:
step 1: and performing voltage drop detection on the voltage of the grid-connected point of the inverter type distributed power supply.
The voltage drop detection method specifically comprises the following steps:
step 1.1: firstly, positive and negative sequence component separation is carried out on the collected voltage of the power grid: separating the positive sequence and the negative sequence of the current output by the inverter and the grid-connected point voltage by adopting a T/4 time delay algorithm, and under an alpha-beta coordinate system, the power grid voltage U on an alpha axis and a beta axis at the moment Tα(t)、Uβ(t) can be expressed as:
Figure BDA0002809169610000071
wherein the content of the first and second substances,
Figure BDA0002809169610000072
representing the positive sequence component of the grid voltage on the alpha axis at time t,
Figure BDA0002809169610000073
representing the negative sequence component of the grid voltage on the alpha axis at time t,
Figure BDA0002809169610000074
representing the positive sequence component of the grid voltage on the beta axis at time t,
Figure BDA0002809169610000075
representing the negative sequence component of the grid voltage on the alpha axis at time t;
Figure BDA0002809169610000076
wherein, U1Representing the magnitude, theta, of the positive sequence component of the mains voltage+Initial phase, U, representing positive sequence component of grid voltage2Representing the magnitude, theta, of the negative sequence component of the grid voltage-Representing the initial phase of the negative sequence component of the power grid voltage;
by substituting formula (2) into formula (1)
Figure BDA0002809169610000081
To the network voltage Uα(t)、Uβ(T) the delay T/4 can be obtained according to the above process:
Figure BDA0002809169610000082
from the above formulas (3) and (4), it is possible to obtain
Figure BDA0002809169610000083
Is represented by the formula (1);
Figure BDA0002809169610000084
step 1.2: respectively converting the alpha-axis component and the beta-axis component of the positive and negative sequence voltage of the power grid obtained in the step 1.1 into a positive and negative sequence dq coordinate system, and sequentially calculating the positive sequence component of the d axis of the power grid voltage
Figure BDA0002809169610000085
And negative sequence component
Figure BDA0002809169610000086
Positive sequence component of q-axis
Figure BDA0002809169610000087
Negative sequence component of q-axis
Figure BDA0002809169610000088
Figure BDA0002809169610000089
Figure BDA00028091696100000810
Step 1.3: and (3) carrying out low-pass filtering processing on the data obtained in the step (1.2) to obtain a required direct current component, carrying out Fourier calculation on the processed three-phase sequence direct current component to obtain an effective value and a phase angle of each sequence component, and carrying out inverse pseudo-gram transformation on the finally obtained phase angle to obtain the voltage amplitude and phase jump condition of each phase.
Step 2: judging the voltage drop condition based on the voltage drop value detected in the step 1, and immediately cutting off the distributed power supply from the power distribution network when the voltage of the power distribution network accessed by the inverter type distributed power supply is in an area below a low-voltage ride-through characteristic curve of the inverter type distributed power supply;
and step 3: judging the voltage drop condition based on the voltage drop value detected in the step 1, and when the voltage of a power distribution network accessed by the inverter type distributed power supply is in an area above a low-voltage ride-through characteristic curve of the inverter type distributed power supply, keeping the inverter type distributed power supply to be in grid-connected operation all the time;
step 3.1: when the power grid has asymmetric faults, in a synchronous rotation dq coordinate system, positive and negative sequence components of the power grid voltage are respectively subjected to directional control, and output negative sequence current components of the inverter type distributed power supply are restrained.
The specific method comprises the following steps:
step 3.1.1: and (3) based on the d-axis and q-axis components of the positive and negative sequence voltages of the power grid obtained in the step 1.2, showing the positive and negative sequence voltage complex vectors of the power grid in a dq coordinate system:
Figure BDA0002809169610000091
according to the complex vector model relation of the inverter distributed power supply in the alpha beta coordinate system:
Figure BDA0002809169610000092
correspondingly obtaining a mathematical model of the positive sequence and the negative sequence of the distributed power supply under a synchronous rotation dq coordinate system:
Figure BDA0002809169610000093
the three-phase instantaneous active power and reactive power output by the inverter type distributed power supply are determined by the three-phase voltage of a grid-connected point and the input power grid current of the distributed power supply, based on the concepts of the active power and the reactive power, the active power p can be expressed as the dot product of the voltage and the current of the power grid, the reactive power q is expressed as the cross product of the voltage and the current of the power grid, and the three-phase instantaneous active power and the reactive power are expressed in the following forms:
Figure BDA0002809169610000094
simplification thereof can lead to the following formula:
Figure BDA0002809169610000095
in the formula p0Is the average value of active power, q0Is the average value of the reactive power, p1Is the amplitude of the cosine second harmonic of the active power, q1Is the amplitude, p, of the cosine second harmonic of the reactive power2Is the amplitude, q, of the sinusoidal second harmonic of the active power2The amplitude of the reactive power sine second harmonic wave; from the above, it is found that when the power grid has an asymmetric fault, both the active power and the reactive power output by the distributed power supply contain second harmonics, and p can be obtained according to the above formula0、q0、p1、q1、p2、q2The corresponding expression:
Figure BDA0002809169610000101
based on directional vector control principle of power grid voltage
Figure BDA0002809169610000102
Equation (12) is simplified to one step:
Figure BDA0002809169610000103
step 3.1.2: the reference values of the negative-sequence current components in the dq coordinate system are each assigned to 0, i.e.:
Figure BDA0002809169610000104
step 3.1.3: the reference value in dq coordinate system of the positive sequence current component is solved according to the step 3.1.1 power expression and step 3.1.2 negative sequence current component reference value in dq coordinate system, that is:
Figure BDA0002809169610000105
the distributed power inverter is controlled by adopting a structural form of a voltage outer ring and a current inner ring, the voltage outer ring adopts a PI (proportional integral) regulator, and the output of the PI regulator corresponds to the input of a positive sequence current inner ring:
Figure BDA0002809169610000106
when low voltage ride through is not considered, the distributed power inverter adopts unit power control, namely q is ordered0And (5) calculating a reference value without considering the active and reactive components of the positive sequence current and the negative sequence current in the low voltage ride through, wherein the reference value is as follows:
Figure BDA0002809169610000107
step 3.2: when the inverter type distributed power supply is always kept in grid-connected operation, the inverter type distributed power supply is controlled by adopting a low-voltage ride through control method, and in the control process, the inverter type distributed power supply outputs active power by adjusting reactive current according to the grid-connected requirement on the premise of ensuring the safe operation of the inverter type distributed power supply, so that the active power of a power grid is kept in a balanced state.
The specific method comprises the following steps:
step 3.2.1: based on the requirement of the inverter-type distributed power supply for low voltage ride through, as shown in fig. 1, when the per unit value of the grid-connected positive sequence voltage of the power distribution network fault is greater than 0.9, the distributed power supply is enabled to output only constant active power, and the normal control mode in step 3.1.3 is maintained, that is, the distributed power supply is enabled to output only constant active power, that is, the normal control mode is enabled
Figure BDA0002809169610000111
Step 3.2.2: when the per unit value of the grid-connected positive sequence voltage of the power distribution network is [0.2, 0.9], at least 2% of reactive current is provided when the positive sequence voltage drops by 1%; firstly, disconnecting the voltage outer ring, then adaptively adjusting an instruction of reactive current based on the voltage of the power grid at the moment, and finally directly giving an instruction of active current according to the bearing capacity borne by the distributed power supply inverter;
when the per unit value of the grid-connected positive sequence voltage of the power distribution network fault is [0, 0.2], the distributed power supply does not output active power and outputs the maximum allowable short-circuit current flowing through the transformer, namely the reactive current of 2 times of rated current; firstly, a voltage outer ring is disconnected, then a reactive current instruction is adaptively adjusted based on the voltage of the power grid at the moment, and finally an active current instruction is directly given according to the bearing capacity borne by the distributed power supply inverter;
step 3.2.3: when a short-circuit fault occurs in a power grid, reference values of corresponding positive and negative sequence current components are increased, but the reference values are not infinitely increased under the limitation of short-circuit current, and a boundary solution equation can be obtained:
Figure BDA0002809169610000112
calculating the boundary voltage to enable the output active current of the distributed power supply to just reach the convenient constraint condition;
Figure BDA0002809169610000113
when the per unit value of the positive sequence voltage is [0.54, 0.9), the distributed power supply meets the margin output active power under the condition that the reactive power can be output preferentially;
when the per unit value of the positive sequence voltage is [0.2, 0.54), the distributed power supply cannot meet the margin output active power, so the finally calculated positive sequence negative sequence current active and reactive reference value is as follows:
Figure BDA0002809169610000121
as shown in fig. 4, the structure diagram of the distribution network into which the inverter-type distributed power source is connected is shown, after the whole distribution network is determined, all data of the distribution network system are determined, a group of operation conditions can be obtained by normally controlling the distributed power source inverter in the upper structure diagram, and the implementation condition of the control method can be obtained by controlling one or more conditions of the asymmetric faults given in 50% of the line 2 by using the low voltage ride through control method.
Example 1:
a control structure block diagram of the whole inverter type distributed power grid-connected inverter is shown in fig. 5: the system comprises an inversion module overall structure, a filtering link, a data sampling link, a positive and negative sequence component separation link, a voltage outer ring control link, a low voltage ride through adaptive regulation link, a current inner ring control link and the like.
The method comprises the following steps: sampling grid-connected voltage and grid-connected current on the grid-connected side of the distributed power supply inverter to obtain three-phase voltage and three-phase current; and separating the positive sequence component and the negative sequence component of the collected power grid data, and separating the three-phase voltage and the three-phase current by a T/4 time delay algorithm to respectively obtain the active and reactive components of the actually measured positive sequence voltage, negative sequence voltage, positive sequence current and negative sequence current.
Step two: and judging data of the voltage quantity of the power grid, directly cutting off the distributed power supply when the power grid is below the low-voltage ride-through characteristic curve, and controlling by adopting a low-voltage ride-through control method when the power grid voltage is above the low-voltage ride-through characteristic curve and meets the requirement of grid connection.
Step three: under the condition of meeting the grid-connected requirement, the change of the grid voltage data has certain difference according to different fault conditions, and the degree of grid voltage drop is judged again. Under the condition that the voltage of the power grid drops below 20%, a normal operation mode is adopted, the voltage outer ring controls normal operation, and the current inner ring adopts a conventional operation method; for the condition that the voltage of the power grid drops by more than 20%, the voltage outer loop control is firstly disconnected, and only the current inner loop control method is adopted. According to the dropping degree of the power grid voltage, on the premise of meeting the grid-connected technical requirements of the distributed power supply, current reference values suitable for the current dropping situation are respectively given.

Claims (4)

1. A low voltage ride through operation control method of an inverter type distributed power supply is characterized in that: the method comprises the following steps:
step 1: voltage drop detection is carried out on the voltage of the grid-connected point of the inverter type distributed power supply;
step 2: judging the voltage drop condition based on the voltage drop value detected in the step 1, and immediately cutting off the distributed power supply from the power distribution network when the voltage of the power distribution network accessed by the inverter type distributed power supply is in an area below a low-voltage ride-through characteristic curve of the inverter type distributed power supply;
and step 3: judging the voltage drop condition based on the voltage drop value detected in the step 1, and when the voltage of a power distribution network accessed by the inverter type distributed power supply is in an area above a low-voltage ride-through characteristic curve of the inverter type distributed power supply, keeping the inverter type distributed power supply to be in grid-connected operation all the time;
step 3.1: when the power grid has asymmetric faults, in a synchronous rotation dq coordinate system, positive and negative sequence components of the power grid voltage are respectively subjected to directional control, and output negative sequence current components of the inverter type distributed power supply are suppressed;
step 3.2: when the inverter type distributed power supply is always kept in grid-connected operation, the inverter type distributed power supply is controlled by adopting a low-voltage ride through control method, and in the control process, the inverter type distributed power supply outputs active power by adjusting reactive current according to the grid-connected requirement on the premise of ensuring the safe operation of the inverter type distributed power supply, so that the active power of a power grid is kept in a balanced state.
2. The method for controlling the low voltage ride through operation of the inverter-type distributed power supply according to claim 1, wherein: in the step 1, the voltage drop detection method specifically includes:
step 1.1: firstly, positive and negative sequence component separation is carried out on the collected voltage of the power grid: separating the positive sequence and the negative sequence of the current output by the inverter and the grid-connected point voltage by adopting a T/4 time delay algorithm, and under an alpha-beta coordinate system, the power grid voltage U on an alpha axis and a beta axis at the moment Tα(t)、Uβ(t) can be expressed as:
Figure FDA0002809169600000011
wherein the content of the first and second substances,
Figure FDA0002809169600000012
representing the positive sequence component of the grid voltage on the alpha axis at time t,
Figure FDA0002809169600000013
representing the negative sequence component of the grid voltage on the alpha axis at time t,
Figure FDA0002809169600000014
representing the positive sequence component of the grid voltage on the beta axis at time t,
Figure FDA0002809169600000015
representing the negative sequence component of the grid voltage on the alpha axis at time t;
Figure FDA0002809169600000016
wherein, U1Representing the magnitude, theta, of the positive sequence component of the mains voltage+Initial phase, U, representing positive sequence component of grid voltage2Representing the magnitude, theta, of the negative sequence component of the grid voltage-Representing the initial phase of the negative sequence component of the power grid voltage;
by substituting formula (2) into formula (1)
Figure FDA0002809169600000021
To the network voltage Uα(t)、Uβ(T) the delay T/4 can be obtained according to the above process:
Figure FDA0002809169600000022
from the above formulas (3) and (4), it is possible to obtain
Figure FDA0002809169600000023
Is represented by the formula (1);
Figure FDA0002809169600000024
step 1.2: respectively converting the alpha-axis component and the beta-axis component of the positive and negative sequence voltage of the power grid obtained in the step 1.1 into a positive and negative sequence dq coordinate system, and sequentially calculating the positive sequence component of the d axis of the power grid voltage
Figure FDA0002809169600000025
And negative sequence component
Figure FDA0002809169600000026
Positive sequence component of q-axis
Figure FDA0002809169600000027
Negative sequence component of q-axis
Figure FDA0002809169600000028
Figure FDA0002809169600000029
Step 1.3: and (3) carrying out low-pass filtering processing on the data obtained in the step (1.2) to obtain a required direct current component, carrying out Fourier calculation on the processed three-phase sequence direct current component to obtain an effective value and a phase angle of each sequence component, and carrying out inverse pseudo-gram transformation on the finally obtained phase angle to obtain the voltage amplitude and phase jump condition of each phase.
3. The method for controlling the low voltage ride through operation of the inverter-type distributed power supply according to claim 2, wherein in the step 3.1), the specific method is as follows:
step 3.1.1: and (3) based on the d-axis and q-axis components of the positive and negative sequence voltages of the power grid obtained in the step 1.2, showing the positive and negative sequence voltage complex vectors of the power grid in a dq coordinate system:
Figure FDA0002809169600000031
according to the complex vector model relation of the inverter distributed power supply in the alpha beta coordinate system:
Figure FDA0002809169600000032
correspondingly obtaining a mathematical model of the positive sequence and the negative sequence of the distributed power supply under a synchronous rotation dq coordinate system:
Figure FDA0002809169600000033
the three-phase instantaneous active power and reactive power output by the inverter type distributed power supply are determined by the three-phase voltage of a grid-connected point and the input power grid current of the distributed power supply, based on the concepts of the active power and the reactive power, the active power p can be expressed as the dot product of the voltage and the current of the power grid, the reactive power q is expressed as the cross product of the voltage and the current of the power grid, and the three-phase instantaneous active power and the reactive power are expressed in the following forms:
Figure FDA0002809169600000034
this was simplified to give the following formula:
Figure FDA0002809169600000035
in the formula p0Is the average value of active power, q0Is the average value of the reactive power, p1Is the amplitude of the cosine second harmonic of the active power, q1Is the amplitude, p, of the cosine second harmonic of the reactive power2Is the amplitude, q, of the sinusoidal second harmonic of the active power2The amplitude of the reactive power sine second harmonic wave; finding out that the power grid has asymmetric faults, the active power and the reactive power output by the distributed power supply both contain second harmonic waves, and obtaining p according to the formula0、q0、p1、q1、p2、q2The corresponding expression:
Figure FDA0002809169600000036
based on directional vector control principle of power grid voltage
Figure FDA0002809169600000037
Equation (12) is simplified to one step:
Figure FDA0002809169600000041
step 3.1.2: the reference values of the negative-sequence current components in the dq coordinate system are each assigned to 0, i.e.:
Figure FDA0002809169600000042
step 3.1.3: the reference value in dq coordinate system of the positive sequence current component is solved according to the step 3.1.1 power expression and step 3.1.2 negative sequence current component reference value in dq coordinate system, that is:
Figure FDA0002809169600000043
the distributed power inverter is controlled by adopting a structural form of a voltage outer ring and a current inner ring, the voltage outer ring adopts a PI (proportional integral) regulator, and the output of the PI regulator corresponds to the input of a positive sequence current inner ring:
Figure FDA0002809169600000044
when low voltage ride through is not considered, the distributed power inverter adopts unit power control, namely q is ordered0And (5) calculating a reference value without considering the active and reactive components of the positive sequence current and the negative sequence current in the low voltage ride through, wherein the reference value is as follows:
Figure FDA0002809169600000045
。
4. the method for controlling the low voltage ride through operation of the inverter-type distributed power supply according to claim 1, wherein in the step 3.2), the specific method comprises the following steps:
step 3.2.1: based on inversion typeThe distributed power supply low voltage ride through requirement is that when the per unit value of the grid-connected positive sequence voltage of the power distribution network fault is greater than 0.9, the distributed power supply is enabled to only output constant active power, and a normal control mode is kept, namely the distributed power supply is enabled to output constant active power
Figure FDA0002809169600000046
Step 3.2.2: when the per unit value of the grid-connected positive sequence voltage of the power distribution network is [0.2, 0.9], at least 2% of reactive current is provided when the positive sequence voltage drops by 1%; firstly, disconnecting the voltage outer ring, then adaptively adjusting an instruction of reactive current based on the voltage of the power grid at the moment, and finally directly giving an instruction of active current according to the bearing capacity borne by the distributed power supply inverter;
when the per unit value of the grid-connected positive sequence voltage of the power distribution network fault is [0, 0.2], the distributed power supply does not output active power and outputs the maximum allowable short-circuit current flowing through the transformer, namely the reactive current of 2 times of rated current; firstly, a voltage outer ring is disconnected, then a reactive current instruction is adaptively adjusted based on the voltage of the power grid at the moment, and finally an active current instruction is directly given according to the bearing capacity borne by the distributed power supply inverter;
step 3.2.3: when a short-circuit fault occurs in a power grid, reference values of corresponding positive and negative sequence current components are increased, but the reference values are not infinitely increased under the limitation of short-circuit current, and a boundary solution equation can be obtained:
Figure FDA0002809169600000051
calculating the boundary voltage to enable the output active current of the distributed power supply to just reach the convenient constraint condition;
Figure FDA0002809169600000052
when the per unit value of the positive sequence voltage is [0.54, 0.9), the distributed power supply meets the margin output active power under the condition that the reactive power can be output preferentially;
when the per unit value of the positive sequence voltage is [0.2, 0.54), the distributed power supply cannot meet the margin output active power, so the finally calculated positive sequence negative sequence current active and reactive reference value is as follows:
Figure FDA0002809169600000053
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113315121A (en) * 2021-05-26 2021-08-27 南方电网科学研究院有限责任公司 Current reference value setting method, device and medium for power grid fault ride-through
CN113794208A (en) * 2021-08-31 2021-12-14 南京智睿能源互联网研究院有限公司 Control method for reducing high-voltage cascade SVG low-voltage ride-through off-line
CN116436043A (en) * 2023-06-13 2023-07-14 国网江西省电力有限公司电力科学研究院 Asymmetric fault ride-through control method for multiple converters

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109494755A (en) * 2019-01-09 2019-03-19 东北大学 A kind of virtual synchronous generator no-voltage passes through control system and control method
CN110198040A (en) * 2019-05-20 2019-09-03 清华大学 Flywheel energy storage system low voltage traversing control method and device based on VSG
CN110518624A (en) * 2018-05-21 2019-11-29 南京理工大学 A kind of low voltage traversing control method based on photovoltaic combining inverter

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110518624A (en) * 2018-05-21 2019-11-29 南京理工大学 A kind of low voltage traversing control method based on photovoltaic combining inverter
CN109494755A (en) * 2019-01-09 2019-03-19 东北大学 A kind of virtual synchronous generator no-voltage passes through control system and control method
CN110198040A (en) * 2019-05-20 2019-09-03 清华大学 Flywheel energy storage system low voltage traversing control method and device based on VSG

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
赵化宾: "考虑低电压穿越的含逆变型分布式电源配电网的故障特性分析", 《中国优秀硕士学位论文全文数据库 工程科技Ⅱ辑》 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113315121A (en) * 2021-05-26 2021-08-27 南方电网科学研究院有限责任公司 Current reference value setting method, device and medium for power grid fault ride-through
CN113315121B (en) * 2021-05-26 2022-06-14 南方电网科学研究院有限责任公司 Current reference value setting method, device and medium for power grid fault ride-through
CN113794208A (en) * 2021-08-31 2021-12-14 南京智睿能源互联网研究院有限公司 Control method for reducing high-voltage cascade SVG low-voltage ride-through off-line
CN113794208B (en) * 2021-08-31 2023-10-24 南京智睿能源互联网研究院有限公司 Control method for reducing high-voltage cascading SVG low-voltage ride through off-grid
CN116436043A (en) * 2023-06-13 2023-07-14 国网江西省电力有限公司电力科学研究院 Asymmetric fault ride-through control method for multiple converters
CN116436043B (en) * 2023-06-13 2023-10-20 国网江西省电力有限公司电力科学研究院 Asymmetric fault ride-through control method for multiple converters

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