CN117277288A - Control method and system for low-voltage ride through recovery of energy storage converter - Google Patents

Abstract

The invention provides a control method and a system for low-voltage ride through recovery of an energy storage converter, which are used for carrying out per unit treatment by acquiring an alternating voltage measured value of a grid-connected point of the energy storage converter; comparing the processed alternating voltage measured value with a voltage amplitude triggering low voltage ride through control; and according to different comparison results, different strategies are adopted to obtain the amplitude limiting value of the voltage outer loop control, the amplitude limiting value of the current inner loop control, the reactive current instruction value and the dynamic reactive coefficient of the outer loop, and the data are input into the energy storage inverter to carry out low voltage ride through control. By implementing the method, the problem of overcurrent caused by switching of the control strategy and nonlinear amplitude limiting of the energy storage converter during low voltage ride through recovery can be prevented, and low voltage ride through failure of the energy storage converter caused by the overcurrent problem can be effectively avoided.

Description

Control method and system for low-voltage ride through recovery of energy storage converter

Technical Field

The invention relates to the technical field of power electronics, in particular to a control method for low-voltage ride through recovery of an energy storage converter.

Background

The grid connection capability of new energy under faults is widely concerned. However, wind power and photovoltaic have the characteristic of random fluctuation, and factors such as new energy output weather, seasons and the like restrict new energy output, so that the power balance of a power grid system is seriously influenced, and even the problem of large-scale off-grid of new energy occurs. For this reason, more and more new energy power stations are equipped with energy storage converters for constantly fluctuating new energy output and improving the power quality of the system. According to the corresponding standard, when the system has voltage drop fault, the energy storage converter is required to be kept for a certain time without off-grid, namely the energy storage converter has low voltage ride through capability. However, in links such as a control strategy and nonlinear amplitude limiting of the energy storage converter during faults, the problem of overcurrent is easy to occur in the low-voltage ride-through recovery process, and the energy storage converter generally has overvoltage and overcurrent protection control links, so that the problem of off-grid occurs in the low-voltage ride-through recovery process of the energy storage converter, the low-voltage ride-through failure is caused, and the stable operation of a power grid is seriously threatened.

Most of the prior researches focus on the control research of the low-voltage ride-through recovery process when the grid voltage drop fault just happens or is in progress. And when the control is performed on dynamic reactive current, the problem of insufficient reactive compensation capability during voltage drop faults possibly occurs, and the low voltage ride-through capability of the energy storage converter is affected.

Disclosure of Invention

The invention aims to solve the technical problem of providing a control method and a system for low-voltage ride-through recovery of an energy storage converter, which can effectively prevent the problem of overcurrent of the energy storage converter during voltage drop fault recovery and avoid the off-grid accident caused by the failure of the low-voltage ride-through of the energy storage converter.

The technical scheme adopted by the invention is that the control method for recovering the low voltage ride through of the energy storage converter comprises the following steps:

step S1, acquiring an alternating voltage measured value of an energy storage converter grid-connected point, and carrying out per unit treatment;

step S2, judging whether the measured value of the alternating voltage subjected to per unit treatment is smaller than the voltage amplitude for triggering low voltage ride through control;

step S3, if yes, calculating a typical low voltage ride through recovery control method according to national standard requirements to obtain an active current given value I _dref Reactive current setpoint I _qref According to the dynamic voltage recovery characteristic, calculating the nonlinear limiting values of the outer voltage loop and the inner current loop, and calculating the dynamic reactive power coefficient of the outer loop;

s4, if not, determining the amplitude limiting value controlled by the outer voltage loop and the amplitude limiting value controlled by the inner current loop as corresponding rated amplitude limiting values;

and S5, inputting the amplitude limiting value of the voltage outer loop control, the amplitude limiting value of the current inner loop control, the reactive current instruction value and the outer loop dynamic reactive coefficient obtained in the step S3 or the step S4 into an energy storage inverter to perform low voltage ride through control.

Preferably, the step S1 further includes:

obtaining a voltage measurement value U through a voltage and current measurement device _abc And a current measurement i _abc The obtained alternating voltage measurement value U _abc Symmetrical component decomposition and per unit treatment are carried out to obtain voltage drop amplitude U _rms 。

Preferably, the step S2 further includes:

the voltage drop amplitude U _rms Voltage amplitude U for triggering low voltage ride through control _T Comparing and judging the voltage drop amplitude U _rms Whether or not it is smaller than the voltage amplitude U triggering the low voltage ride through control _T Wherein the U _T The value is 0.85.

Preferably, the step S3 further includes:

step S30, if the judgment result is the voltage drop amplitude U _rms Voltage amplitude U smaller than low voltage ride through control _T The following formula is adopted to calculate the active current given value I under the typical low voltage ride through recovery control method _dref And reactive current setpoint I _qref ：

Wherein K is _LVRT And K is equal to _LVRT _ _Z Respectively a low voltage ride through reactive current support coefficient and a low voltage ride through reactive current support coefficient, I _N Rated current of the energy storage converter; u (U) _rms The voltage drop value is the alternating voltage drop value of the grid-connected point of the system, namely the voltage per unit value of the grid-connected point of the energy storage converter;

step S31, calculating nonlinear limiting values of the outer ring of the voltage and the inner ring of the current according to the dynamic recovery characteristic of the voltage, and calculating dynamic reactive coefficients of the outer ring; in particular according to the per unit value U of the alternating voltage measured value of the acquisition system grid-connected point _rms The nonlinear limiting value I is calculated by adopting the following formula _dlimit And I _qlimit Calculating dynamic reactive coefficient K of outer ring _qw ：

Wherein I is _dreflimit 、I _qreflimit 、I _dlimit And I _qlimit Respectively representing nonlinear limiting values of a current inner loop and a voltage outer loop in a low voltage ride through process, I _{d_e} 、I _{q_e} 、I _{d_e} And I _{q_e} Rated limiting values K of a voltage outer loop and a current inner loop respectively representing a low voltage ride through process _qw Is the dynamic reactive coefficient of the outer ring.

Preferably, the step S4 further includes:

if the judgment result is that the voltage drop amplitude U _rms Voltage amplitude U greater than or equal to low voltage ride through control _T Determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the voltage outer loop control, determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the current outer loop control, andthe dynamic reactive coefficient of the outer loop is determined to be 1.

Accordingly, in another aspect of the present invention, there is also provided a control system for low voltage ride through recovery of an energy storage converter, including:

the measurement processing unit is used for acquiring an alternating voltage measured value of the grid-connected point of the energy storage converter and carrying out per unit processing;

the judging unit is used for judging whether the alternating voltage measured value subjected to per unit treatment is smaller than the voltage amplitude for triggering the low voltage ride through control;

a calculation unit for calculating typical low voltage ride through recovery control method according to national standard requirement to obtain active current given value I when the judgment result of the judgment unit is yes _dref Reactive current setpoint I _qref According to the dynamic voltage recovery characteristic, calculating the nonlinear limiting values of the outer voltage loop and the inner current loop, and calculating the dynamic reactive power coefficient of the outer loop;

the determining unit is used for determining the limiting value of the voltage outer loop control and the limiting value of the current inner loop control as corresponding rated limiting values when the judging result of the judging unit is negative;

and the ride-through control unit is used for inputting the amplitude limiting value of the voltage outer loop control, the amplitude limiting value of the current inner loop control, the reactive current instruction value and the outer loop dynamic reactive coefficient obtained by the calculation unit or the determination unit into the energy storage inverter to perform low voltage ride-through control.

Preferably, the measurement processing unit is specifically configured to:

obtaining a voltage measurement value U through a voltage and current measurement device _abc And a current measurement i _abc The obtained alternating voltage measurement value U _abc Symmetrical component decomposition and per unit treatment are carried out to obtain voltage drop amplitude U _rms 。

Preferably, the judging unit is specifically configured to:

the voltage drop amplitude U _rms Voltage amplitude U for triggering low voltage ride through control _T Comparing and judging the voltage drop amplitude U _rms Whether or not it is less than the triggerVoltage amplitude U of low voltage ride through control _T Wherein the U _T The value is 0.85.

Preferably, the computing unit further comprises:

a first calculation unit for determining the voltage drop amplitude U _rms Voltage amplitude U smaller than low voltage ride through control _T The following formula is adopted to calculate the active current given value I under the typical low voltage ride through recovery control method _dref And reactive current setpoint I _qref ：

Wherein K is _LVRT And K is equal to _LVRT _ _Z Respectively a low voltage ride through reactive current support coefficient and a low voltage ride through reactive current support coefficient, I _N Rated current of the energy storage converter; u (U) _rms The voltage drop value is the alternating voltage drop value of the grid-connected point of the system, namely the voltage per unit value of the grid-connected point of the energy storage converter;

the second calculation unit is used for calculating the nonlinear limiting values of the outer voltage loop and the inner current loop according to the dynamic voltage recovery characteristic and calculating the dynamic reactive coefficient of the outer loop; in particular according to the per unit value U of the alternating voltage measured value of the acquisition system grid-connected point _rms The nonlinear limiting value I is calculated by adopting the following formula _dlimit And I _qlimit Calculating dynamic reactive coefficient K of outer ring _qw ：

Wherein I is _dreflimit 、I _qreflimit 、I _dlimit And I _qlimit Respectively representing nonlinear limiting values of a current inner loop and a voltage outer loop in a low voltage ride through process, I _{d_e} 、I _{q_e} 、I _{d_e} And I _{q_e} Rated limiting values K of a voltage outer loop and a current inner loop respectively representing a low voltage ride through process _qw Is the dynamic reactive coefficient of the outer ring.

Preferably, the determining unit is specifically configured to:

the judgment result is the voltage drop amplitude U _rms Voltage amplitude U greater than or equal to low voltage ride through control _T And determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the voltage outer loop control, determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the current outer loop control, and determining the dynamic reactive coefficient of the outer loop as 1.

The embodiment of the invention has the following beneficial effects:

the invention provides a control method and a system for low-voltage ride through recovery of an energy storage converter. Performing per unit processing by acquiring an alternating voltage measured value of an energy storage converter grid-connected point; comparing the alternating voltage measured value subjected to per unit treatment with a voltage amplitude triggering low voltage ride through control; and according to different comparison results, different strategies are adopted to obtain the amplitude limiting value of the voltage outer loop control, the amplitude limiting value of the current inner loop control, the reactive current instruction value and the dynamic reactive coefficient of the outer loop, and the data are input into the energy storage inverter to carry out low voltage ride through control. By implementing the method, the problem of overcurrent caused by switching of the control strategy and nonlinear amplitude limiting of the energy storage converter during low voltage ride through recovery can be prevented, and low voltage ride through failure of the energy storage converter caused by the overcurrent problem can be effectively avoided.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic main flow chart of an embodiment of a control method for low voltage ride through recovery of an energy storage converter according to the present invention;

FIG. 2 is a schematic diagram of the energy storage device in the application environment of FIG. 1;

FIG. 3 is a schematic diagram of a simulation result of output power obtained by a conventional fault ride through control method in a charging mode;

FIG. 4 is a schematic diagram of simulation results of output power obtained by the method of the present invention in a charging mode;

FIG. 5 is a schematic diagram of a simulation result of output power obtained by a conventional fault ride-through control method in a discharge mode;

FIG. 6 is a schematic diagram of the simulation results of the output power obtained by the method of the present invention in discharge mode;

fig. 7 is a schematic structural diagram of an embodiment of a control system for low voltage ride through recovery of an energy storage converter according to the present invention;

fig. 8 is a schematic diagram of the configuration of the calculation unit in fig. 7.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Fig. 1 is a schematic diagram of a main flow of an embodiment of a control method for low voltage ride through recovery of an energy storage converter according to the present invention; in this embodiment, as shown in fig. 2, the method at least includes the following steps:

step S1, acquiring an alternating voltage measured value of an energy storage converter grid-connected point, and carrying out per unit treatment;

it will be appreciated that the method of the present invention is applicable to an energy storage device as in figure 2. In fig. 2, the energy storage device adopts a two-stage structure, and the direct current side adopts two stagesAn inverter circuit is used for the AC side of the DC-DC circuit. Because the scheme focuses on low voltage ride through control and optimization under fault conditions, the direct current side bidirectional DC-DC control link can be omitted in the embodiment. The AC side control link comprises: 1) Normal operating mode: voltage/power outer loop control and current inner loop control; 2) Voltage sag fault conditions: low voltage ride through control and current inner loop control. Obtaining a voltage measurement value U through a voltage and current measurement device _abc And a current measurement i _abc The obtained alternating voltage measurement value U _abc Symmetrical component decomposition is carried out to obtain a voltage drop amplitude U _rms . Under normal working conditions, the limiting value of the PI controller of the voltage/power outer ring and the current inner ring is set to be k times of the per unit value, namely the limiting value of the voltage outer ring is I _{dref_e} ＝kI _dref And I _{qref_e} ＝kI _qref The current inner loop limit value is I _{d_e} ＝kI _d And I _{q_e} ＝kI _q K is usually 1.2 or 1.5.

It will be appreciated that, where I _{dref_e} Limiting value representing d-axis current reference value of voltage outer loop, I _{qref_e} A clipping value representing a q-axis current reference value of the voltage outer loop; i _{d_e} Limiting value of d-axis current representing current inner loop, I _{q_e} Representing the clipping value of the q-axis current of the inner loop of current. Wherein I is _d Represents d-axis current, I _q Represents q-axis current; i _dref Reference value representing d-axis current, I _qref Representing a reference value of q-axis current. I _d 、I _q 、I _dref 、I _qref Obtained from the per unit value.

Thus, in a specific example, the step S1 further includes:

obtaining a voltage measurement value U through a voltage and current measurement device _abc And a current measurement i _abc The obtained alternating voltage measurement value U _abc Symmetrical component decomposition and per unit treatment are carried out to obtain voltage drop amplitude U _rms 。

Step S2, judging whether the measured value of the alternating voltage subjected to per unit treatment is smaller than the voltage amplitude for triggering low voltage ride through control;

in a specific example, the step S2 further includes:

the voltage drop amplitude U _rms Voltage amplitude U for triggering low voltage ride through control _T Comparing and judging the voltage drop amplitude U _rms Whether or not it is smaller than the voltage amplitude U triggering the low voltage ride through control _T Wherein the U _T The value is 0.85.

Step S3, if yes, calculating to obtain an active current given value I by adopting a typical low voltage ride through recovery control method according to national standard requirements _dref Reactive current setpoint I _qref According to the dynamic voltage recovery characteristic, calculating the nonlinear limiting values of the outer voltage loop and the inner current loop, and calculating the dynamic reactive power coefficient of the outer loop;

in a specific example, the step S3 further includes:

step S30, if the judgment result is the voltage drop amplitude U _rms Voltage amplitude U smaller than low voltage ride through control _T The following formula is adopted to calculate the active current given value I under the typical low voltage ride through recovery control method _dref And reactive current setpoint I _qref ：

Wherein K is _LVRT And K is equal to _LVRT _ _Z Respectively a low voltage ride through reactive current support coefficient and a low voltage ride through reactive current support coefficient, I _N Rated current of the energy storage converter; u (U) _rms The voltage drop value is the alternating voltage drop value of the grid-connected point of the system, namely the voltage per unit value of the grid-connected point of the energy storage converter;

step S31, calculating nonlinear limiting values of the outer ring of the voltage and the inner ring of the current according to the dynamic recovery characteristic of the voltage, and calculating dynamic reactive coefficients of the outer ring; in particular according to acquisition system grid-connected pointsPer unit value U of ac voltage measurement _rms The nonlinear limiting value I is calculated by adopting the following formula _dlimit And I _qlimit Calculating dynamic reactive coefficient K of outer ring _qw ：

Wherein I is _dreflimit 、I _qreflimit 、I _dlimit And I _qlimit Respectively representing nonlinear limiting values of a current inner loop and a voltage outer loop in a low voltage ride through process, I _{d_e} 、I _{q_e} 、I _{d_e} And I _{q_e} Rated limiting values K of a voltage outer loop and a current inner loop respectively representing a low voltage ride through process _qw Is the dynamic reactive coefficient of the outer ring.

It can be seen that if the ac voltage measurement value U _rms Voltage amplitude U smaller than trigger low voltage ride through control _T The nonlinear amplitude limiting value of the voltage outer loop control is the product of the alternating voltage measured value and the rated amplitude limiting value of the voltage outer loop control, the nonlinear amplitude limiting value of the current inner loop control is the product of the alternating voltage measured value and the rated amplitude limiting value of the current inner loop control, and the dynamic reactive coefficient of the outer loop is the square of the alternating voltage measured value.

S4, if not, determining the amplitude limiting value controlled by the outer voltage loop and the amplitude limiting value controlled by the inner current loop as corresponding rated amplitude limiting values;

in a specific example, the step S4 further includes:

if the judgment result is that the voltage drop amplitude U _rms Voltage amplitude U greater than or equal to low voltage ride through control _T And determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the voltage outer loop control, determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the current outer loop control, and determining the dynamic reactive coefficient of the outer loop as 1.

And S5, inputting the amplitude limiting value of the voltage outer loop control, the amplitude limiting value of the current inner loop control, the reactive current instruction value and the outer loop dynamic reactive coefficient obtained in the step S3 or the step S4 into an energy storage inverter to perform low voltage ride through control.

The PSCAD/EMTDC simulation software is operated to simulate and verify the low voltage ride through control strategy provided by the invention, and in a specific example, a voltage drop fault is set on the alternating current side of the photovoltaic system, the voltage drop amplitude is 0.6pu, and the fault lasts for 1s. Fig. 3 and fig. 4 are simulation results of conventional fault ride through control output power in a charging mode and fault ride through control according to the present invention, respectively. Fig. 5 and fig. 6 are simulation results of conventional fault ride through control output power in a discharge mode and fault ride through control according to the present invention, respectively. As can be seen from fig. 4 and 6, the simulation result of the method provided by the invention is smoother.

Referring to fig. 7, a schematic structural diagram of an embodiment of a control system for low voltage ride through recovery of an energy storage converter according to the present invention is shown. As shown in fig. 8, in this embodiment, the system 1 at least includes:

the measurement processing unit 10 is used for obtaining an alternating voltage measured value of the grid-connected point of the energy storage converter and carrying out per unit processing;

a judging unit 11, configured to judge whether the ac voltage measured value after the per unit processing is smaller than a voltage amplitude for triggering the low voltage ride through control;

a calculating unit 12 for calculating typical low voltage ride through recovery control method to obtain the active current given value I according to national standard requirement when the judging result of the judging unit is yes _dref Reactive current setpoint I _qref According to the dynamic voltage recovery characteristic, calculating the nonlinear limiting values of the outer voltage loop and the inner current loop, and calculating the dynamic reactive power coefficient of the outer loop;

a determining unit 13, configured to determine, when the determination result of the determining unit is no, the limiting value of the outer loop control of the voltage and the limiting value of the inner loop control of the current as corresponding rated limiting values;

and the ride-through control unit 14 is configured to input the limiting value of the outer loop control of the voltage, the limiting value of the inner loop control of the current, the reactive current command value and the dynamic reactive coefficient of the outer loop obtained by the calculation unit or the determination unit into the energy storage inverter, and perform low voltage ride-through control.

In a specific example, the measurement processing unit 10 is specifically configured to:

obtaining a voltage measurement value U through a voltage and current measurement device _abc And a current measurement i _abc The obtained alternating voltage measurement value U _abc Symmetrical component decomposition and per unit treatment are carried out to obtain voltage drop amplitude U _rms 。

In a specific example, the judging unit 11 is specifically configured to:

the voltage drop amplitude U _rms Voltage amplitude U for triggering low voltage ride through control _T Comparing and judging the voltage drop amplitude U _rms Whether or not it is smaller than the voltage amplitude U triggering the low voltage ride through control _T Wherein the U _T The value is 0.85.

In a specific example, the computing unit 12 further includes:

a first calculating unit 120 for, when the judgment result is the voltage drop amplitude U _rms Voltage amplitude U smaller than low voltage ride through control _T The following formula is adopted to calculate the active current given value I under the typical low voltage ride through recovery control method _dref And reactive current setpoint I _qref ：

Wherein K is _LVRT And K is equal to _LVRT _ _Z Respectively a low voltage ride through reactive current support coefficient and a low voltage ride through reactive current support coefficient, I _N Rated current of the energy storage converter; u (U) _rms The voltage drop value is the alternating voltage drop value of the grid-connected point of the system, namely the voltage per unit value of the grid-connected point of the energy storage converter;

a second calculation unit 121 for according toThe voltage dynamic recovery characteristic, the nonlinear limiting value of the voltage outer ring and the current inner ring is calculated, and the dynamic reactive coefficient of the outer ring is calculated; in particular according to the per unit value U of the alternating voltage measured value of the acquisition system grid-connected point _rms The nonlinear limiting value I is calculated by adopting the following formula _dlimit And I _qlimit Calculating dynamic reactive coefficient K of outer ring _qw ：

Wherein I is _dreflimit 、I _qreflimit 、I _dlimit And I _qlimit Respectively representing nonlinear limiting values of a current inner loop and a voltage outer loop in a low voltage ride through process, I _{d_e} 、I _{q_e} 、I _{d_e} And I _{q_e} Rated limiting values K of a voltage outer loop and a current inner loop respectively representing a low voltage ride through process _qw Is the dynamic reactive coefficient of the outer ring.

In a specific example, the determining unit 13 is specifically configured to:

the judgment result is the voltage drop amplitude U _rms Voltage amplitude U greater than or equal to low voltage ride through control _T And determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the voltage outer loop control, determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the current outer loop control, and determining the dynamic reactive coefficient of the outer loop as 1.

For more details, reference is made to the foregoing descriptions of fig. 1 to 7, and no further description is given here.

The embodiment of the invention has the following beneficial effects:

the invention provides a control method and a system for low-voltage ride through recovery of an energy storage converter. Performing per unit processing by acquiring an alternating voltage measured value of an energy storage converter grid-connected point; comparing the alternating voltage measured value subjected to per unit treatment with a voltage amplitude triggering low voltage ride through control; and according to different comparison results, different strategies are adopted to obtain the amplitude limiting value of the voltage outer loop control, the amplitude limiting value of the current inner loop control, the reactive current instruction value and the dynamic reactive coefficient of the outer loop, and the data are input into the energy storage inverter to carry out low voltage ride through control. By implementing the method, the problem of overcurrent caused by switching of the control strategy and nonlinear amplitude limiting of the energy storage converter during low voltage ride through recovery can be prevented, and low voltage ride through failure of the energy storage converter caused by the overcurrent problem can be effectively avoided.

It will be apparent to those skilled in the art that embodiments of the present invention may be provided as a method, apparatus, 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 modules specified in the flowchart flow or flows and/or block diagram block or blocks.

Finally, it should be noted that: the foregoing description is only illustrative of the preferred embodiments of the present invention, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements or changes may be made without departing from the spirit and principles of the present invention.

Claims (10)

1. The control method for the low-voltage ride through recovery of the energy storage converter is characterized by comprising the following steps of:

step S1, acquiring an alternating voltage measured value of an energy storage converter grid-connected point, and carrying out per unit treatment;

step S2, judging whether the measured value of the alternating voltage subjected to per unit treatment is smaller than the voltage amplitude for triggering low voltage ride through control;

step S3, if yes, calculating to obtain a corresponding active current given value I _dref Reactive current setpoint I _qref According to the dynamic voltage recovery characteristic, calculating the nonlinear limiting values of the outer voltage loop and the inner current loop, and calculating the dynamic reactive power coefficient of the outer loop;

s4, if not, determining the amplitude limiting value controlled by the outer voltage loop and the amplitude limiting value controlled by the inner current loop as corresponding rated amplitude limiting values;

and S5, inputting the amplitude limiting value of the voltage outer loop control, the amplitude limiting value of the current inner loop control, the reactive current instruction value and the outer loop dynamic reactive coefficient obtained in the step S3 or the step S4 into an energy storage inverter to perform low voltage ride through control.

2. The method according to claim 1, wherein the step S1 further comprises:

obtaining a voltage measurement value U through a voltage and current measurement device _abc And a current measurement i _abc The obtained alternating voltage measurement value U _abc Symmetrical component decomposition and per unit treatment are carried out to obtain voltage drop amplitude U _rms 。

3. The method of claim 2, said step S2 further comprising:

the voltage drop amplitude U _rms Voltage amplitude U for triggering low voltage ride through control _T Comparing and judging the voltage drop amplitude U _rms Whether or not it is smaller than the voltage amplitude U triggering the low voltage ride through control _T Wherein the U _T The value is 0.85.

4. The method of claim 3, wherein said step S3 further comprises:

step S30, if the judgment result is the voltage drop amplitude U _rms Voltage amplitude U smaller than low voltage ride through control _T The following formula is adopted to calculate the active current given value I under the typical low voltage ride through recovery control method _dref And reactive current setpoint I _qref ：

Wherein K is _LVRT And K is equal to _LVRT _ _Z Respectively a low voltage ride through reactive current support coefficient and a low voltage ride through reactive current support coefficient, I _N Rated current of the energy storage converter; u (U) _rms The voltage drop value is the alternating voltage drop value of the grid-connected point of the system, namely the voltage per unit value of the grid-connected point of the energy storage converter;

step S31, calculating nonlinear limiting values of the outer ring of the voltage and the inner ring of the current according to the dynamic recovery characteristic of the voltage, and calculating dynamic reactive coefficients of the outer ring; in particular according to the per unit value U of the alternating voltage measured value of the acquisition system grid-connected point _rms The nonlinear limiting value I is calculated by adopting the following formula _dlimit And I _qlimit Calculating dynamic reactive coefficient K of outer ring _qw ：

Wherein I is _dreflimit 、I _qreflimit 、I _dlimit And I _qlimit Respectively representing nonlinear limiting values of a current inner loop and a voltage outer loop in a low voltage ride through process, I _{d_e} 、I _{q_e} 、I _{d_e} And I _{q_e} Rated limiting values K of a voltage outer loop and a current inner loop respectively representing a low voltage ride through process _qw Is the dynamic reactive coefficient of the outer ring.

5. The method of claim 4, wherein said step S4 further comprises:

if the judgment result is that the voltage drop amplitude U _rms Voltage amplitude U greater than or equal to low voltage ride through control _T And determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the voltage outer loop control, determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the current outer loop control, and determining the dynamic reactive coefficient of the outer loop as 1.

6. A control system for energy storage converter low voltage ride through recovery, comprising:

the measurement processing unit is used for acquiring an alternating voltage measured value of the grid-connected point of the energy storage converter and carrying out per unit processing;

the judging unit is used for judging whether the alternating voltage measured value subjected to per unit treatment is smaller than the voltage amplitude for triggering the low voltage ride through control;

a calculation unit for calculating typical low voltage ride through recovery control method according to national standard requirement to obtain active current given value I when the judgment result of the judgment unit is yes _dref Reactive current setpoint I _qref According to the dynamic voltage recovery characteristic, calculating the nonlinear limiting values of the outer voltage loop and the inner current loop, and calculating the dynamic reactive power coefficient of the outer loop;

the determining unit is used for determining the limiting value of the voltage outer loop control and the limiting value of the current inner loop control as corresponding rated limiting values when the judging result of the judging unit is negative;

and the ride-through control unit is used for inputting the amplitude limiting value of the voltage outer loop control, the amplitude limiting value of the current inner loop control, the reactive current instruction value and the outer loop dynamic reactive coefficient obtained by the calculation unit or the determination unit into the energy storage inverter to perform low voltage ride-through control.

7. The system according to claim 6, wherein the measurement processing unit is specifically configured to:

obtaining a voltage measurement value U through a voltage and current measurement device _abc And a current measurement i _abc The obtained alternating voltage measurement value U _abc Symmetrical component decomposition and per unit treatment are carried out to obtain voltage drop amplitude U _rms 。

8. The system of claim 7, wherein the judging unit is specifically configured to:

the voltage drop amplitude U _rms Voltage amplitude U for triggering low voltage ride through control _T Comparing and judging the voltage drop amplitude U _rms Whether or not it is smaller than the voltage amplitude U triggering the low voltage ride through control _T Wherein the U _T The value is 0.85.

9. The system of claim 8, wherein the computing unit further comprises:

a first calculation unit for determining the voltage drop amplitude U _rms Voltage amplitude U smaller than low voltage ride through control _T The following formula is adopted to calculate the active current given value I under the typical low voltage ride through recovery control method _dref And reactive current setpoint I _qref ：

In the middle of，K _LVRT And K is equal to _LVRT _ _Z Respectively a low voltage ride through reactive current support coefficient and a low voltage ride through reactive current support coefficient, I _N Rated current of the energy storage converter; u (U) _rms The voltage drop value is the alternating voltage drop value of the grid-connected point of the system, namely the voltage per unit value of the grid-connected point of the energy storage converter; the method comprises the steps of carrying out a first treatment on the surface of the

The second calculation unit is used for calculating the nonlinear limiting values of the outer voltage loop and the inner current loop according to the dynamic voltage recovery characteristic and calculating the dynamic reactive coefficient of the outer loop; in particular according to the per unit value U of the alternating voltage measured value of the acquisition system grid-connected point _rms The nonlinear limiting value I is calculated by adopting the following formula _dlimit And I _qlimit Calculating dynamic reactive coefficient K of outer ring _qw ：

Wherein I is _dreflimit 、I _qreflimit 、I _dlimit And I _qlimit Respectively representing nonlinear limiting values of a current inner loop and a voltage outer loop in a low voltage ride through process, I _{d_e} 、I _{q_e} 、I _{d_e} And I _{q_e} Rated limiting values K of a voltage outer loop and a current inner loop respectively representing a low voltage ride through process _qw Is the dynamic reactive coefficient of the outer ring.

10. The system according to claim 9, wherein the determining unit is specifically configured to:

the judgment result is the voltage drop amplitude U _rms Voltage amplitude U greater than or equal to low voltage ride through control _T And determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the voltage outer loop control, determining the rated limiting value of the voltage outer loop control as the nonlinear limiting value of the current outer loop control, and determining the dynamic reactive coefficient of the outer loop as 1.