CN116995730A - DC side voltage reference value setting method, device, storage medium and equipment - Google Patents

DC side voltage reference value setting method, device, storage medium and equipment Download PDF

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Publication number
CN116995730A
CN116995730A CN202310991532.5A CN202310991532A CN116995730A CN 116995730 A CN116995730 A CN 116995730A CN 202310991532 A CN202310991532 A CN 202310991532A CN 116995730 A CN116995730 A CN 116995730A
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China
Prior art keywords
voltage
grid
converter
reference value
ride
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Chinese (zh)
Inventor
陈兵
李群
姜齐荣
李博洋
王旭
王方明
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Tsinghua University
State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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Tsinghua University
State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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Priority to CN202310991532.5A priority Critical patent/CN116995730A/en
Publication of CN116995730A publication Critical patent/CN116995730A/en
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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
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
    • 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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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

Abstract

The invention discloses a method, a device, a storage medium and equipment for setting a direct-current side voltage reference value. According to different power grid voltage drop conditions, corresponding strategies are executed to reduce the direct-current voltage reference value, so that a higher modulation factor can be kept in the whole low-voltage ride-through process, meanwhile, the switching loss of the grid-structured converter is reduced, and the quality of an output waveform is improved. During high voltage ride through, the constant voltage control is adopted to possibly cause the grid-formed converter to lose balance points, so that the DC side reference value setting algorithm is divided into three conditions according to different power grid voltage lifting amplitudes, and an algorithm for maintaining the minimum active current required by stable DC side bus voltage is provided to ensure that the DC voltage is always controllable in the whole ride through process.

Description

DC side voltage reference value setting method, device, storage medium and equipment
Technical Field
The invention relates to a method, a device, a storage medium and equipment for setting a direct-current side voltage reference value, and belongs to the field of control and protection.
Background
In recent years, with the access of high-proportion power electronic equipment and high-proportion new energy into a power grid, a power system gradually develops towards low inertia and weak damping. The power electronic converter gradually becomes dominant and has the characteristic of multi-stage control synergy in control. Compared to traditional grids, high-proportion new energy power systems involve a wider time scale dynamics, which requires that they have to respond to disturbances over a wide frequency domain. Unlike traditional power grids, high-proportion new energy power systems are mainly supported by a grid-structured converter for providing voltage and frequency, and meanwhile, the grid-structured converter must have certain fault ride-through capability to ensure reliable operation of the power system. The current grid-structured converter needs to realize smooth running of a direct current side, which is a precondition for a new energy power system to complete fault ride-through.
The direct current side generally adopts a constant voltage control method when the current network-structured converter passes through faults. The two types of the two-stage new energy system are mainly divided into two types, wherein direct-current side constant voltage control is mainly added into a chopper circuit or a rectifier; for a single-stage new energy system, the control strategy of a grid-structured converter is mainly improved, and the control of a direct current side is added, so that the constant control of a direct current bus during fault crossing is realized.
However, when the grid-built converter performs high-low voltage ride through, the direct current side adopting the constant voltage control method tends to sacrifice the quality of the output waveform of the system, and similarly, for the high voltage ride through condition of the grid-built converter, maintaining the voltage of the direct current side constant may cause the grid-built converter to lose balance points, and further cause new energy to be off grid.
Disclosure of Invention
The invention provides a method, a device, a storage medium and equipment for setting a direct-current side voltage reference value, which solve the problems disclosed in the background technology.
In order to solve the technical problems, the invention adopts the following technical scheme:
a DC side voltage reference value setting method comprises the following steps:
responding to the fault ride-through signal of the grid-formed converter to carry out low-voltage ride-through, and calculating a DC side voltage reference value of the grid-formed converter during the low-voltage ride-through according to the voltage drop condition of the power grid during the low-voltage ride-through;
and responding to the fault ride-through signal of the grid-formed converter to carry out high-voltage ride-through, and according to the voltage lifting amplitude of the power grid during the high-voltage ride-through, calculating the voltage reference value of the direct-current side of the grid-formed converter by considering the minimum active current of the grid-formed converter required for maintaining the voltage stability of the direct-current side bus of the grid-formed converter.
The grid voltage drop condition comprises a single-phase drop of the grid voltage, a two-phase drop of the grid voltage and a three-phase symmetrical drop of the grid voltage;
according to the voltage drop condition of the power grid, calculating a DC side voltage reference value of the grid-constructed converter during low voltage ride through comprises the following steps:
if the power grid voltage single-phase drops, the reference value of the DC side voltage of the grid-structured converter during low-voltage ride through is the DC side voltage of the grid-structured converter during steady-state operation;
if the two phases of the power grid voltage drop, calculating a DC side voltage reference value of the grid-constructed converter during low voltage ride through according to the maximum difference value of any two phases of voltage;
if the grid voltage falls symmetrically in three phases and the voltage drop ratio obtained by calculation according to the three-phase voltage is not smaller than a threshold value, calculating a direct current side voltage reference value of the grid-formed converter during low-voltage ride through according to the voltage drop ratio and the direct current side voltage of the grid-formed converter during steady-state operation;
if the grid voltage falls symmetrically in three phases and the voltage drop ratio obtained by calculation according to the three-phase voltage is smaller than a threshold value, calculating a direct-current side voltage reference value of the grid-structured converter during low-voltage ride-through according to the threshold value and the direct-current side voltage during steady-state operation of the grid-structured converter.
According to the maximum difference value of any two-phase voltage, calculating a DC side voltage reference value of the grid-structured converter during low voltage ride through, wherein the formula is as follows:
in U dc_ref For constructing DC side voltage reference value of network type converter, V 1 、V 2 The two-phase voltage peak with the largest difference.
According to the voltage drop ratio and the DC side voltage of the grid-connected converter in steady-state operation, calculating the DC side voltage reference value of the grid-connected converter, wherein the formula is as follows:
U dc_ref ＝J*U dc0
in U dc_ref U is the voltage reference value of the DC side of the grid-structured converter dc0 For the dc side voltage of the grid-connected converter during steady-state operation,v as pressure drop ratio a 、V b 、V c Is three-phase voltage, V 0 The voltage of the PCC point is rated for the grid-type converter in operation.
According to the threshold value and the DC side voltage of the grid-connected converter in steady state operation, calculating the DC side voltage reference value of the grid-connected converter in low voltage ride through, wherein the formula is as follows:
U dc_ref ＝A*U dc0
in U dc_ref U is the voltage reference value of the DC side of the grid-structured converter dc0 The DC side voltage is the DC side voltage when the grid-connected converter operates stably, and A is a threshold value.
Responding to a fault ride-through signal of the grid-connected converter to carry out high-voltage ride-through, and according to the voltage lifting amplitude of a power grid during the high-voltage ride-through, considering the minimum active current of the grid-connected converter required for maintaining the voltage stability of a bus at the direct current side of the grid-connected converter, calculating a voltage reference value at the direct current side of the grid-connected converter during the high-voltage ride-through, wherein the method comprises the following steps:
if |V during the grid voltage rise g |＜U dc /m-ω g L g I max Or U dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max And i dc1 ＜i od1max The reference value of the DC side voltage of the grid-connected transformer during high-voltage ride through is the DC side voltage of the grid-connected transformer during steady-state operation; wherein V is g For the grid voltage, U dc The DC bus voltage of the grid-structured converter, m is the modulation factor, omega g For the angular frequency of the electric network, L g Is the equivalent inductance of the power grid, I max Current upper limit value i of net-structured converter dc1 ＝2i L U dc /(3V gd ) In order to maintain the minimum active current of the net type converter required by the stable voltage of the bus at the direct current side of the net type converter, i L Injecting current of a grid-structured converter into a new energy power generation system, V gd For the d-axis component, i of the network voltage od1max The maximum active current which can be output by the grid-structured converter;
if U is in the process of grid voltage lifting dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max And i dc1 ≥i od1max Or |V g |＞U dc /m+ω g L g I max The direct-current side voltage of the grid-structured converter is adjusted by adopting a fixed step length, and the grid-structured converter is direct-currentThe regulated DC side voltage of the grid-structured converter is not less than U dcmax Or i dc1 ≤i od1max Calculating a DC side voltage reference value of the grid-structured converter during high-voltage ride-through according to the regulated DC side voltage of the grid-structured converter; wherein U is dcmax The maximum voltage is the DC side of the network-structured converter.
If U is dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max And i dc1 ≥i od1max The initial DC side voltage of the grid-connected transformer is the DC side voltage of the grid-connected transformer in steady state operation, and the fixed step length is
If |V g |＞U dc /m+ω g L g I max Initial grid-formed converter DC side voltage U dc_base ＝m(V gd -ω g L g I max ) At this time, the fixed step length is
A dc-side voltage reference setting apparatus comprising:
the first response module responds to the fault ride-through signal of the grid-formed converter to carry out low-voltage ride-through, and calculates a DC side voltage reference value of the grid-formed converter during the low-voltage ride-through according to the voltage drop condition of the power grid during the low-voltage ride-through;
and the second response module responds to the fault ride-through signal of the grid-formed converter to carry out high-voltage ride-through, and calculates a voltage reference value of the direct current side of the grid-formed converter during the high-voltage ride-through by considering the minimum active current of the grid-formed converter required for maintaining the voltage stability of the direct current side bus of the grid-formed converter according to the voltage lifting amplitude of the power grid during the high-voltage ride-through.
A computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by a computing device, cause the computing device to perform a dc-side voltage reference setting method.
A computer device comprising one or more processors, and one or more memories in which one or more programs are stored and configured to be executed by the one or more processors, the one or more programs comprising instructions for performing a dc-side voltage reference value setting method.
The invention has the beneficial effects that: aiming at the low-voltage crossing condition, the invention calculates the DC side voltage reference value of the grid-structured converter during the low-voltage crossing according to the voltage drop condition of the power grid, further can execute a corresponding strategy to reduce the DC voltage reference value, can keep a higher modulation factor in the whole low-voltage crossing process, reduces the switching loss of the grid-structured converter and improves the quality of output waveforms; according to the situation of high voltage ride-through, according to different power grid voltage lifting amplitude, the minimum active current of the grid type converter required for maintaining the voltage stability of the bus at the direct current side is considered, and the reference value of the voltage at the direct current side of the grid type converter during high voltage ride-through is calculated, so that the voltage at the direct current side of the whole high voltage ride-through process can be always controllable, and further the stable operating point of the grid type converter during fault ride-through process is always ensured.
Drawings
FIG. 1 is a flow chart of a method for setting a DC side voltage reference value;
FIG. 2 is a grid-tie control system for a grid-tie converter;
FIG. 3 is a flowchart of calculating the DC side voltage reference value of the grid-formed converter during low voltage ride through;
FIG. 4 is a flowchart of the calculation of the DC side voltage reference of the grid-formed converter with the high voltage passing through;
fig. 5 is a flow chart of a fixed step adjustment grid-formed converter dc side voltage;
fig. 6 is a flowchart of the calculation of the dc side voltage reference value of the complete grid-formed converter.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and are not intended to limit the scope of the present invention.
As shown in fig. 1, a method for setting a reference value of a dc side voltage includes the following steps:
step 1, low-voltage ride through is performed in response to a fault ride-through signal of a grid-formed converter, and a direct-current side voltage reference value of the grid-formed converter during low-voltage ride-through is calculated according to the voltage drop condition of a power grid during low-voltage ride-through;
and 2, performing high-voltage ride through in response to the fault ride-through signal of the grid-formed converter, and calculating a voltage reference value of the direct-current side of the grid-formed converter during high-voltage ride-through according to the voltage lifting amplitude of the power grid during high-voltage ride-through by considering the minimum active current of the grid-formed converter required for maintaining the voltage stability of the direct-current side bus of the grid-formed converter.
According to the method, aiming at the low-voltage crossing condition, the DC side voltage reference value of the grid-structured converter in the low-voltage crossing is calculated according to the voltage drop condition of the power grid, so that a corresponding strategy can be executed to reduce the DC voltage reference value, a higher modulation factor can be kept in the whole low-voltage crossing process, the switching loss of the grid-structured converter is reduced, and the quality of an output waveform is improved; according to the situation of high voltage ride-through, according to different power grid voltage lifting amplitude, the minimum active current of the grid type converter required for maintaining the voltage stability of the bus at the direct current side is considered, and the reference value of the voltage at the direct current side of the grid type converter during high voltage ride-through is calculated, so that the voltage at the direct current side of the whole high voltage ride-through process can be always controllable, and further the stable operating point of the grid type converter during fault ride-through process is always ensured.
The method has certain universality, can be used for setting the DC side voltage reference value of the grid-structured converter, can also be used for controlling the DC side in fault ride through in the boost circuit control of the two-stage photovoltaic system, and can realize parameter transmission through communication among controllers. In addition, the method can be used for a two-stage direct-drive fan system, and the direct-current side reference value setting method is only needed to be loaded in a direct-current side control strategy of the rectifier, so that a reliable direct-current operation point can be provided for fault ride-through of the grid-side converter while the waveform output quality is optimized.
The method for setting the reference value of the direct current side is suitable for any grid-formed control strategy, and takes grid-formed control as shown in fig. 2 as an example to embody the importance of setting the reference value of the direct current side in the fault ride-through process of the grid-formed converter, namely, the frequency and the phase angle of alternating current output are generated by the dynamic characteristic of the direct current voltage of the system, and the part of the figure, which is framed with the DC-reference, adopts the setting method. The system performs current limiting through virtual impedance, and adjusts the dq axis current through a fault ride-through module so as to meet reactive power requirements during fault ride-through of the system; the power frequency loop control rate is as follows:
ω＝ω 0 +G DVC ·(V dc -V dcref )
θ＝∫ωdt
wherein ω is the output angular frequency of the grid-formed converter, ω 0 For synchronizing angular velocity of electric network, V dc To construct DC side voltage of the network type converter, V dcref The reference value is the DC side voltage of the grid-built converter; θ is the angular position of the rotating frame dq0 in the grid-built converter Park and inverse Park transforms; g DVC The method is realized by adopting PI control for a direct-current voltage controller, and is defined as follows:
wherein K is pdc P, K, which is the P parameter of the DC voltage controller idc Is the I parameter of the DC voltage controller.
When the fault ride-through signal of the grid-connected transformer carries out low-voltage ride-through, firstly, calculating a voltage reference value of the DC side of the grid-connected transformer during the low-voltage ride-through according to the voltage drop condition of the power grid during the low-voltage ride-through.
Referring to fig. 3, when a single-phase drop of the grid voltage is detected, the output performance cannot be improved by reducing the dc link voltage, because the modulation degree at this time remains unchanged, that is, if the single-phase drop of the grid voltage occurs, the reference value of the dc side voltage of the grid-configured converter during low-voltage ride through is the dc side voltage during steady-state operation of the grid-configured converter.
When the two-phase dip of the power grid voltage is detected, calculating a DC side voltage reference value of the grid-constructed converter during low-voltage ride-through according to the maximum difference value of any two-phase voltage; for example, when the voltage drop amplitude of the phase A and the phase C is the same and the voltage of the phase B is unchanged, the minimum direct current voltage cannot be smaller than 0.866 times of the maximum difference value of the voltages of the phase A and the phase B; let the a-phase and B-phase voltages be expressed as:
wherein V is 1 、V 2 Peak value of two-phase voltage with maximum difference, namely peak value of output phase voltage of A phase and B phase, omega g For grid angular frequency, then:
at this time, the liquid crystal display device,
in U dc_ref Is the DC side voltage reference value of the grid-structured converter during low voltage crossing.
When detecting that the grid voltage has three-phase symmetrical drop, in order to keep the modulation degree unchanged, the voltage drop ratio can be set as follows:
wherein J is the pressure drop ratio, V 0 For the voltage of PCC point when the network-structured converter operates at rated speed, V a 、V b 、V c For three-phase voltage, obtained by sampling, a first-order low-pass filter is connected before measurement to prevent high-frequency component in sampled value from causing fluctuation of DC side reference value, its parameter can be designed by DC side maximum voltage ripple required by network-structured converter, and its cut-off frequency is givenThe reference value is 400rad/s.
When J is not smaller than the threshold value, calculating a DC side voltage reference value of the grid-structured converter during low-voltage ride-through according to the voltage drop ratio and the DC side voltage during steady-state operation of the grid-structured converter, wherein the DC side voltage reference value can be expressed as follows by a formula:
U dc_ref ＝J*U dc0
in U dc0 The DC side voltage is the DC side voltage when the grid-connected converter operates stably;
when J is smaller than the threshold value, calculating a DC side voltage reference value of the grid-structured converter during low-voltage ride-through according to the threshold value and the DC side voltage during steady-state operation of the grid-structured converter, wherein the DC side voltage reference value can be expressed as follows by a formula:
U dc_ref ＝A*U dc0
in the formula, A is a threshold value, and in order to prevent J=0 when the photovoltaic grid-structured converter crosses zero voltage, the minimum allowable value of J is set to be 0.2, namely, A is set to be 0.2.
According to the dynamic change characteristics of the grid-structured converter during low voltage ride through, the method can respectively give corresponding direct current side reference values according to the conditions of symmetrical and asymmetrical voltage drops during low voltage ride through, and in order to prevent the direct current side reference values from dropping to zero during zero voltage ride through of the photovoltaic grid-structured converter, the method sets the lowest direct current side voltage drop ratio, can keep a higher modulation factor while considering various grid voltage drop conditions, reduces high-frequency harmonic waves and improves the quality of output waveforms.
When the fault crossing signal of the grid-structured converter carries out high voltage crossing, the original reference value of the direct current side is maintained to cause the system to be overmodulated, and meanwhile, the grid-structured converter possibly has no operating point, so that the reference value of the direct current side during the high voltage crossing of the grid-structured converter is required to be controlled.
For the system shown in fig. 2, the following two limitations should be noted:
wherein I is max Electric for network-structured current transformerThe upper limit value of the current is generally set as the rated current I of the grid-type converter rated 1.5 times, i odq To output current, v, under the dq coordinate system of the grid-structured converter odq For outputting voltage under dq coordinate system of grid-structured converter, U dc The direct current bus voltage of the network-structured converter is represented by m, and the m is a modulation factor.
According to the condition of the voltage rise of the power grid during high voltage ride through, the method comprises the following steps of rms 、V rms 、V g The three size relations mainly include the following three cases, see fig. 4:
when |V g |＜U dc /m-ω g L g I max Obviously, the output voltage is within the range provided by the grid-connected converter at this moment, namely, the reference value of the DC side voltage of the grid-connected converter during high-voltage ride-through is the DC side voltage of the grid-connected converter during steady-state operation;
when U is dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max At least one stable operation point must exist in the network-structured converter at this time, and the following relation is satisfied:
wherein V is gd For the d-axis component, i of the network voltage od1 And i oq1 Active current and reactive current, omega, are respectively output for the grid-structured converter under the operating point g For the angular frequency of the electric network, L g Is the equivalent inductance of the power grid, I max The upper limit value of the current of the grid-connected transformer is generally set as the rated current I of the grid-connected transformer rated 1.5 times of (2);
solving the above method to obtain i od1 And i oq1 Obviously, as the grid voltage gradually increases, i oq1 Must also be gradually increased, so that the maximum active current i which can be output by the grid-formed converter od1max Will decrease when i oq1 When not less than 0, it is obvious that i is od1max ＝I max When i oq1 When < 0, the following relationship exists:
let i be the active current of the grid-connected converter (grid-connected converter) required to maintain the stability of the dc bus of the grid-connected converter dc1 ：
i dc1 ＝2i L U dc /(3V gd )
Wherein i is L Injecting current of the grid-built converter into the new energy power generation system; obviously, i od1max Must be greater than i dc1 I.e. when U dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max And i dc1 ＜i od1max The DC side voltage reference value of the grid-connected converter is the DC side voltage of the grid-connected converter in steady-state operation. When U is dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max And i dc1 ≥i od1max Referring to fig. 5, the dc side voltage of the grid-formed converter is adjusted by a fixed step length until the adjusted dc side voltage of the grid-formed converter is not less than U dcmax Or i dc1 ≤i od1max And calculating a DC side voltage reference value of the grid-structured converter during high voltage ride through according to the regulated DC side voltage of the grid-structured converter.
The specific procedure in fig. 5 is as follows:
1) Assume that the initial DC side voltage of the grid-formed converter is U dc_base Fixed step size DeltaU dc ；
2) If U is dc_base +ΔU dc ＜U dcmax Go to 3), otherwise U dc_ref ＝U dc_base The method comprises the steps of carrying out a first treatment on the surface of the Wherein U is dcmax The maximum voltage of the DC side of the grid-structured converter is obtained;
3)U′ dc_ref ＝U dc_base +ΔU dc ；
4) If U' dc_ref ＜U dcmax Go to 5), otherwise U dc_ref ＝U′ dc_ref -ΔU dc ；
5) If i od1max ＜i dc1 Go to 6), otherwise U dc_ref ＝U′ dc_ref ；
6)U dc_base ＝U′ dc_ref Go to 3).
In U dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max The initial DC side voltage of the grid-connected transformer is the DC side voltage of the grid-connected transformer in steady state operation, namely U dc_base ＝U dc0 Fixed step sizeWherein m is a modulation factor, which is 1 for SPWM modulation and +.>k is the adjustment step size which determines the proposed value of the accuracy of the algorithm of fig. 5 to be 0.1.
When |V g |＞U dc /m+ω g L g I max When the grid-structured converter is uncontrollable, the output voltage exceeds the operation range of the grid-structured converter, and the direct current side reference must be controlled, and the method is the same as that of fig. 5, and the only difference is that: initial grid-formed converter DC side voltage U dc_base ＝m(V gd -ω g L g I max ) Fixed step size
According to the dynamic change characteristics of the grid-formed converter during high voltage ride through, the method divides a DC side reference value setting algorithm into three cases according to the amplitude of grid side voltage lifting, and simultaneously considers the minimum active current for maintaining the DC side bus voltage, so that the DC link voltage is always controllable. In addition, the method can obviously improve the condition that the network side voltage rises suddenly to generate transient impact on the network-structured converter, thereby avoiding the serious problem that the network-structured converter generates direct-current side overvoltage or overcurrent due to out-of-control during high-voltage ride-through
The above method is designed and implemented according to the following steps before operation, see fig. 6:
s1) obtaining starting parameters;
the maximum voltage of the DC side of the grid-type converter (U is obtained by measuring or consulting manual dcmax ) The voltage of PCC point, the angular frequency of the power grid, the power grid inductance, the rated current of the grid-structured converter, the DC voltage of the grid-structured converter in steady-state operation, the switching frequency of the grid-structured converter and the like when the grid-structured converter operates nominally; the d-axis component of the network side voltage during the rated operation of the system is obtained by measuring or calculating and other modes; obtaining minimum active current i of network-structured converter required by maintaining direct current bus through calculation dc1 。
S2) testing a three-phase voltage sensor;
the system runs in an open loop, and whether the direct current side controller can accept an accurate and stable three-phase voltage effective value signal at the PCC or not is checked by adjusting down the single-phase/two-phase/three-phase network side voltage.
S3) a low voltage ride through DC side reference value output test;
and starting the grid-structured converter in a steady-state operation voltage range, detecting whether direct-current control of the grid-structured converter can send a direct-current reference value instruction according to a corresponding mode by properly regulating down single-phase/two-phase/three-phase power grid voltage, clearing fault voltage after a certain time, and detecting whether a reference value of an output direct-current side is recovered.
S4) a high voltage ride through DC side reference value output test;
properly regulating the voltage amplitude of the network side to respectively meet U dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max Sum case |V g |＞U dc /m+ω g L g I max Detecting whether the direct-current side voltages respectively meet the requirementAnd->Is a function of the adjustment relationship of (a).
Based on the same technical scheme, the invention also discloses a virtual device of the method, namely software, and a direct-current side voltage reference value setting device comprises:
the first response module responds to the fault ride-through signal of the grid-formed converter to carry out low-voltage ride-through, and calculates a DC side voltage reference value of the grid-formed converter during the low-voltage ride-through according to the voltage drop condition of the power grid during the low-voltage ride-through;
and the second response module responds to the fault ride-through signal of the grid-formed converter to carry out high-voltage ride-through, and calculates a voltage reference value of the direct current side of the grid-formed converter by considering the minimum active current of the grid-formed converter required for maintaining the voltage stability of the direct current side bus of the grid-formed converter according to the voltage lifting amplitude of the power grid during the high-voltage ride-through.
The data processing flow and method of each module are consistent, and the description thereof is not repeated here.
Based on the same technical solution, the present invention also discloses a computer-readable storage medium storing one or more programs, the one or more programs including instructions, which when executed by a computing device, cause the computing device to perform a dc-side voltage reference value setting method.
Based on the same technical scheme, the invention also discloses a computer device, which comprises one or more processors and one or more memories, wherein one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs comprise instructions for executing the direct-current side voltage reference value setting method.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The foregoing is illustrative of the present invention and is not to be construed as limiting thereof, but rather as providing for the use of additional embodiments and advantages of all such modifications, equivalents, improvements and similar to the present invention are intended to be included within the scope of the present invention as defined by the appended claims.

Claims (10)

1. The method for setting the reference value of the direct-current side voltage is characterized by comprising the following steps of:
responding to the fault ride-through signal of the grid-formed converter to carry out low-voltage ride-through, and calculating a DC side voltage reference value of the grid-formed converter during the low-voltage ride-through according to the voltage drop condition of the power grid during the low-voltage ride-through;
and responding to the fault ride-through signal of the grid-formed converter to carry out high-voltage ride-through, maintaining the minimum active current of the grid-formed converter required by the voltage stabilization of the bus at the direct current side of the grid-formed converter according to the voltage lifting amplitude of the power grid during the high-voltage ride-through, and calculating the voltage reference value at the direct current side of the grid-formed converter during the high-voltage ride-through.
2. The method for setting a reference value of a direct current side voltage according to claim 1, wherein the grid voltage drop condition includes a single-phase drop of the grid voltage, a two-phase drop of the grid voltage, and a three-phase symmetrical drop of the grid voltage;
according to the voltage drop condition of the power grid, calculating a DC side voltage reference value of the grid-constructed converter during low voltage ride through comprises the following steps:
if the power grid voltage single-phase drops, the reference value of the DC side voltage of the grid-structured converter during low-voltage ride through is the DC side voltage of the grid-structured converter during steady-state operation;
if the two phases of the power grid voltage drop, calculating a DC side voltage reference value of the grid-constructed converter during low voltage ride through according to the maximum difference value of any two phases of voltage;
if the grid voltage falls symmetrically in three phases and the voltage drop ratio obtained by calculation according to the three-phase voltage is not smaller than a threshold value, calculating a direct current side voltage reference value of the grid-formed converter during low-voltage ride through according to the voltage drop ratio and the direct current side voltage of the grid-formed converter during steady-state operation;
if the grid voltage falls symmetrically in three phases and the voltage drop ratio obtained by calculation according to the three-phase voltage is smaller than a threshold value, calculating a direct-current side voltage reference value of the grid-structured converter during low-voltage ride-through according to the threshold value and the direct-current side voltage during steady-state operation of the grid-structured converter.
3. The method for setting a dc-side voltage reference value according to claim 2, wherein the dc-side voltage reference value of the grid-formed converter during low voltage ride through is calculated according to a maximum difference value of any two-phase voltages, and the formula is:
in U dc_ref For constructing DC side voltage reference value of network type converter, V 1 、V 2 The two-phase voltage peak with the largest difference.
4. The method for setting a dc side voltage reference value according to claim 2, wherein the dc side voltage reference value of the grid-formed converter during low voltage ride through is calculated according to a voltage drop ratio and a dc side voltage during steady operation of the grid-formed converter, and the formula is:
U dc_ref ＝J*U dc0
in U dc_ref U is the voltage reference value of the DC side of the grid-structured converter dc0 For the dc side voltage of the grid-connected converter during steady-state operation,v as pressure drop ratio a 、V b 、V c Is three-phase voltage, V 0 The voltage of the PCC point is rated for the grid-type converter in operation.
5. The method for setting a dc side voltage reference value according to claim 2, wherein the dc side voltage reference value of the grid-formed converter during low voltage ride through is calculated according to a threshold value and a dc side voltage during steady-state operation of the grid-formed converter, and the formula is:
U dc_ref ＝A*U dc0
in U dc_ref U is the voltage reference value of the DC side of the grid-structured converter dc0 The DC side voltage is the DC side voltage when the grid-connected converter operates stably, and A is a threshold value.
6. The method for setting a dc side voltage reference value according to claim 1, wherein the step of calculating the dc side voltage reference value of the grid-formed converter in the high voltage ride through by considering a minimum active current of the grid-formed converter required for maintaining the dc side bus voltage stability of the grid-formed converter according to a grid voltage rise amplitude in the high voltage ride through in response to the fault ride through signal of the grid-formed converter comprises:
if |V during the grid voltage rise g |＜U dc /m-ω g L g I max Or U dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max And i dc1 ＜i od1max The reference value of the DC side voltage of the grid-connected transformer during high-voltage ride through is the DC side voltage of the grid-connected transformer during steady-state operation; wherein V is g For the grid voltage, U dc The DC bus voltage of the grid-structured converter, m is the modulation factor, omega g For the angular frequency of the electric network, L g Is the equivalent inductance of the power grid, I max Current upper limit value i of net-structured converter dc1 ＝2i L U dc /(3V gd ) In order to maintain the minimum active current of the net type converter required by the stable voltage of the bus at the direct current side of the net type converter, i L Injecting current of a grid-structured converter into a new energy power generation system, V gd For the d-axis component, i of the network voltage od1max The maximum active current which can be output by the grid-structured converter;
if U is in the process of grid voltage lifting dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max And i dc1 ≥i od1max Or |V g |＞U dc /m+ω g L g I max Direct-current side electricity of grid-structured converter is adjusted by adopting fixed step lengthPressing until the regulated DC side voltage of the grid-formed converter is not less than U dcmax Or i dc1 ≤i od1max Calculating a DC side voltage reference value of the grid-structured converter during high-voltage ride-through according to the regulated DC side voltage of the grid-structured converter; wherein U is dcmax The maximum voltage is the DC side of the network-structured converter.
7. The method of setting a DC side voltage reference value according to claim 6, wherein if U dc /m-ω g L g I max ≤|V g |≤U dc /m+ω g L g I max And i dc1 ≥i od1max The initial DC side voltage of the grid-connected transformer is the DC side voltage of the grid-connected transformer in steady state operation, and the fixed step length is
If |V g |＞U dc /m+ω g L g I max Initial grid-formed converter DC side voltage U dc_base ＝m(V gd -ω g L g I max ) At this time, the fixed step length is
8. A direct current side voltage reference value setting device, comprising:
the first response module responds to the fault ride-through signal of the grid-formed converter to carry out low-voltage ride-through, and calculates a DC side voltage reference value of the grid-formed converter during the low-voltage ride-through according to the voltage drop condition of the power grid during the low-voltage ride-through;
and the second response module responds to the fault ride-through signal of the grid-formed converter to carry out high-voltage ride-through, and calculates a voltage reference value of the direct current side of the grid-formed converter during the high-voltage ride-through by considering the minimum active current of the grid-formed converter required for maintaining the voltage stability of the direct current side bus of the grid-formed converter according to the voltage lifting amplitude of the power grid during the high-voltage ride-through.
9. A computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by a computing device, cause the computing device to perform any of the methods of claims 1-7.
10. A computer device, comprising:
one or more processors, and one or more memories in which one or more programs are stored and configured to be executed by the one or more processors, the one or more programs comprising instructions for performing any of the methods of claims 1-7.
CN202310991532.5A 2023-08-08 2023-08-08 DC side voltage reference value setting method, device, storage medium and equipment Pending CN116995730A (en)

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