Distribution network distributed energy active and reactive coordination droop control method

Abstract

The embodiment of the invention discloses a distribution network distributed energy active and reactive coordination droop control method, which comprises the following steps of: acquiring three-phase voltage of a distribution network, filtering, and judging whether the three-phase voltage of the distribution network is out of limit or not based on a preset reactive stable region; if yes, amplitude limiting / speed limiting is carried out on reactive output through reactive droop control and single-phase reactive limitation, so that a reactive instruction is generated, and reactive power adjustment is executed; when the power distribution network three-phase voltage reaches the lower limit of the reactive power adjustment threshold value, the three-phase voltage of the power distribution network still exceeds the limit, and the single-phase reactive power set according to the reactive instruction is compared with the actual reactive power output to control active enabling and generate an active instruction so as to execute active power adjustment and control the three-phase voltage of the power distribution network; on the basis of active and reactive coordination control of the power distribution network, the voltage control effect is achieved, and the operation stability of the power distribution network is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network control, and in particular to a method for coordinated droop control of active and reactive power of distributed energy in a distribution network. Background Art

[0002] With the continuous development of distributed power generation technology, large-scale distributed power sources are connected to the distribution network. The connection of large-scale distributed power sources to the grid has alleviated the problems of energy shortage and environmental pollution to a certain extent. However, due to the randomness of the output of large-scale distributed power sources, it will cause voltage fluctuations in the distribution network after large-scale grid connection, thereby affecting the power quality of distribution network users. In addition, the drastic fluctuations in the distribution network voltage caused by the uncertainty of large-scale distributed power generation processing will increase the pressure on the stable operation of the main power grid. The above problems put forward higher requirements for the voltage control of the distribution network.

[0003] At present, most distribution network voltage dispatching and control methods have adopted the "layered and hierarchical" control system of the main network. The existing methods are all based on steady-state models, and the control cycle is at the minute level. However, the time scale of voltage fluctuations caused by changes in the output of large-scale distributed power sources in the distribution network is usually a few seconds. It can be seen that the current methods cannot effectively deal with the voltage fluctuation phenomenon of the distribution network caused by the power fluctuation of large-scale distributed power sources. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for coordinated droop control of active and reactive power of distributed energy in a distribution network, so as to realize voltage control of the distribution network and improve the stability of the operation of the distribution network.

[0005] To achieve the above objectives, the present application provides a method for coordinated droop control of active and reactive power of distributed energy in a distribution network, the method comprising:

[0006] Collect the three-phase voltage of the distribution network, filter it, and determine whether the three-phase voltage of the distribution network exceeds the limit based on the preset reactive power stability zone;

[0007] If so, the reactive output is limited / speed-limited through reactive droop control and single-phase reactive limitation, thereby generating reactive commands to perform reactive power regulation;

[0008] When the lower limit of the reactive power regulation threshold is reached and the three-phase voltage of the distribution network is still out of limit, the active power is enabled and an active power instruction is generated based on the comparison between the single-phase reactive power set by the reactive power instruction and the actual reactive power output to execute active power regulation and control the three-phase voltage of the distribution network.

[0009] Optionally, the method further includes:

[0010] Simplify and equate the formal topology of the distribution network to obtain the equivalent topological structure;

[0011] According to the equivalent topological structure, modeling and simulation are performed to obtain a characteristic slope curve between different reactive powers of the photovoltaic grid-connected point and the grid-connected point voltage through simulation, thereby obtaining a reactive characteristic slope;

[0012] The photovoltaic reactive power is set to 0, and the characteristic curve oa between the photovoltaic active power and the grid connection point voltage is obtained through simulation and real data fitting;

[0013] Selecting point a in the characteristic curve oa as the reference point of the maximum photovoltaic active power and the corresponding maximum voltage;

[0014] According to the reactive characteristic slope and the inverter maximum reactive adjustable limit Q max , draw a line segment in the lower half of the voltage-power plane, whose intercept on the voltage abscissa is point c, which serves as the lower limit of the reactive power regulation threshold.

[0015] Optionally, the method further includes:

[0016] Determine a target point d for voltage control according to the control target, and the intersection of the vertical line of the target point d and the voltage horizontal coordinate is the voltage value of the control target point;

[0017] Draw a line segment from the point c to the target point d to obtain the active power boundary curve cd after reactive power control is put into operation;

[0018] The line segment cd intersects the characteristic curve oa at point e, and a vertical line from point e intersects the voltage abscissa at point g, which serves as the upper limit of the reactive power regulation threshold.

[0019] Optionally, the method further includes:

[0020] Setting the voltage dead zone of the line segment cd as an active power stability zone;

[0021] Based on the reactive characteristic slope line cb, correction is performed to obtain a corrected slope line cb';

[0022] The voltage dead zone of the modified slope line cb' is set as the preset reactive power stability zone.

[0023] Optionally, the performing correction based on the reactive characteristic slope line cb to obtain a corrected slope line cb' comprises:

[0024] Determine the droop limit slope according to the reactive characteristic slope line cb;

[0025] Determine a reactive power control starting point, where the reactive power control starting point is any point between point c and point g;

[0026] Select the minimum reactive adjustable limit Q lim , based on Qlim The droop limit slope is connected to the reactive power control starting point by an oblique line to determine the correction slope line cb'.

[0027] Optionally, the single-phase reactive power limitation is expressed as follows:

[0028] ifmax(Q x )-min(Q x )>δQ

[0029] thenmin(Q x )=max(Q x )-δQ;

[0030] else

[0031] end

[0032] Among them, Q x is the single-phase reactive power, and δQ is the reactive power limit parameter.

[0033] Optionally, the single-phase active power limitation is expressed as follows:

[0034] ifmax(P x )-min(P x )>δP

[0035] thenmin(P x )=max(P x )-δP;

[0036] else

[0037] end

[0038] Among them, P x is the single-phase active power, and δP is the active power limit parameter.

[0039] On the other hand, the present application also provides a distribution network distributed energy source active and reactive coordinated droop control device, comprising:

[0040] A judgment module is used to collect the three-phase voltage of the distribution network, and after filtering, judge whether the three-phase voltage of the distribution network exceeds the limit based on a preset reactive power stability zone;

[0041] A reactive power control module is used to limit the reactive output by reactive droop control and single-phase reactive power limitation, thereby generating reactive power instructions to perform reactive power regulation;

[0042] The active power control module is used to control the active power enable and generate an active power instruction to execute active power regulation and control the three-phase voltage of the distribution network when the lower limit of the reactive power regulation threshold is reached and the three-phase voltage of the distribution network is still over the limit, based on the comparison between the single-phase reactive power set by the reactive instruction and the actual reactive power output.

[0043] On the other hand, the present application provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the first aspect and any possible implementation method thereof.

[0044] On the other hand, the present application provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes each step of the method described in the first aspect.

[0045] The present application provides a method for coordinated droop control of active and reactive power of distributed energy in a distribution network. The method collects the three-phase voltage of the distribution network, filters it, and judges whether the three-phase voltage of the distribution network exceeds the limit based on a preset reactive stability zone. If so, the reactive output is limited / speed-limited through reactive droop control and single-phase reactive limitation, thereby generating a reactive instruction to perform reactive power regulation. When the lower limit of the reactive power regulation threshold is reached, the three-phase voltage of the distribution network still exceeds the limit. The active power is controlled by comparing the single-phase reactive power set by the reactive instruction with the actual reactive power output, and an active power instruction is generated to perform active power regulation and control the three-phase voltage of the distribution network. The method solves the problem of large voltage fluctuation of distributed energy in the distribution network, and proposes a new method for controlling active power and reactive power at the same time to achieve voltage control, thereby improving the stability of the distribution network operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] in:

[0048] Figure 1 A flow chart of a method for coordinated droop control of active and reactive power of distributed energy in a distribution network provided in an embodiment of the present application;

[0049] Figure 2 A characteristic curve diagram of photovoltaic active power, reactive power and voltage provided in an embodiment of the present application;

[0050] Figure 3 Another characteristic curve diagram of photovoltaic active power, reactive power and voltage provided in an embodiment of the present application;

[0051] Figure 4 A flow chart of another method for coordinated droop control of active and reactive power of distributed energy in a distribution network provided in an embodiment of the present application;

[0052] Figure 5 A schematic diagram of a control flow of a power distribution network voltage control system provided in an embodiment of the present application;

[0053] Figure 6 A schematic diagram of the structure of a distribution network distributed energy source active and reactive coordinated droop control device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0055] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0056] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0057] The power conversion system (PCS) mentioned in the embodiments of the present application is a special term and can be regarded as an inverter.

[0058] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0059] See also Figure 1 , is a flow chart of a method for coordinated droop control of active and reactive power of a distribution network distributed energy provided in an embodiment of the present application. Figure 1 As shown, the method includes:

[0060] 101. Collect the three-phase voltage of the distribution network, filter it, and determine whether the three-phase voltage of the distribution network exceeds the limit based on a preset reactive power stability zone;

[0061] 102. If yes, the reactive output is limited / speed-limited by reactive droop control and single-phase reactive limitation, thereby generating reactive commands to perform reactive power regulation;

[0062] 103. When the lower limit of the reactive power regulation threshold is reached and the three-phase voltage of the distribution network is still out of limit, the active power is enabled and an active power instruction is generated by comparing the single-phase reactive power set by the reactive power instruction with the actual reactive power output to execute active power regulation and control the three-phase voltage of the distribution network.

[0063] The method in the embodiment of the present application can be executed by a distribution network distributed energy active and reactive coordinated droop control device, which can specifically be a terminal device.

[0064] The principle of the method in the embodiment of the present application is mainly to collect the three-phase voltage of the distribution network. When the voltage exceeds the limit, the droop control method is used to coordinate the active and reactive power of the distribution network at the same time; reactive power control can be put into priority to reduce the voltage. When the maximum reactive power threshold (the lower limit of the reactive power regulation threshold) is reached, the voltage has not been adjusted to the limited range, and the active power is intervened; by determining the active power slope of the droop control, the active power is ensured to be in the stable area; according to the coordinated control of the active and reactive power of the distribution network, the distribution network is controlled on the spot. This control method can solve the problem of large voltage fluctuations of distributed energy sources in the distribution network, and proposes a new method for controlling active and reactive power at the same time to achieve voltage control, providing new ideas for subsequent researchers and improving the stability of the distribution network operation.

[0065] If the three-phase voltage of the distribution network does not exceed the limit, you can return to continue filtering processing.

[0066] Among them, a reasonable "dead zone" or stable zone is set. When the voltage at the photovoltaic grid-connected point exceeds the upper limit, reactive power control is prioritized to reduce the voltage. The voltage qualification rate is improved at the expense of a part of the network loss. If the grid-connected point voltage still cannot be restored to a reasonable value after reactive power control is put into use, active power control is put into use to reduce photovoltaic output. The above method can alleviate the contradiction between voltage exceeding the limit and active power during the photovoltaic centralized transmission period, improve the voltage qualification rate, minimize the power loss of photovoltaic power generation, and reduce the occurrence of abandoned light.

[0067] Specifically, the implementation method may be to send reactive power instructions to the PCS through droop control and single-phase reactive power limitation to control the reactive power output of the distribution network, and the process may include:

[0068] Reactive power control: Collect the three-phase voltage of the distribution network, filter it, and determine whether the voltage exceeds the set "dead zone". If not, return to continue filtering. When it exceeds the "dead zone", the reactive power output is limited / speed-limited through reactive power droop control and single-phase reactive power limitation, thereby generating reactive power instructions;

[0069] Active power control: Through active power droop control, single-phase active power limitation, reactive power command feedback and reactive power output feedback, it is determined whether active power intervention is needed, and the active power output is limited / speed-limited, thereby generating active power commands and finally controlling the distribution network voltage. The specific process may include:

[0070] The three-phase voltage of the distribution network is collected and filtered to determine whether the voltage crosses the set "dead zone". If not, it returns to continue filtering. When it crosses the dead zone, it is judged through the active power droop controller, single-phase active power limitation, reactive power command feedback and reactive power output feedback. It is mainly based on the comparison between the single-phase reactive power set by the reactive command and the actual reactive power output to control the active power enable, thereby limiting the active power / speed, generating active power commands, and finally realizing the voltage control of the distribution network.

[0071] In order to more clearly illustrate the coordinated droop control method of active and reactive power of distributed energy in the distribution network of this application, the simulation modeling and parameter settings involved in this application are first introduced below.

[0072] In an optional implementation, the above method further includes:

[0073] Simplify and equate the formal topology of the distribution network to obtain the equivalent topological structure;

[0074] According to the above equivalent topological structure, modeling and simulation are carried out, and the characteristic slope curve between different reactive powers of photovoltaic grid-connected points and grid-connected point voltage is obtained through simulation to obtain the reactive characteristic slope;

[0075] The photovoltaic reactive power is set to 0, and the characteristic curve oa between the photovoltaic active power and the grid connection point voltage is obtained through simulation and real data fitting;

[0076] Select point a in the above characteristic curve oa as the reference point of the maximum photovoltaic active power and the corresponding maximum voltage;

[0077] According to the above reactive characteristic slope and the inverter maximum reactive adjustable limit Q max, draw a line segment in the lower half of the voltage-power plane, whose intercept on the voltage horizontal axis is point c, which serves as the lower limit of the threshold of the above-mentioned reactive power regulation.

[0078] Simulation modeling: In the embodiment of the present application, the formal topology of the distribution network is simplified and equivalent, and the equivalent topological structure is obtained. Modeling and simulation are performed based on the equivalent topological structure. The characteristic slope curve between different reactive powers of the photovoltaic grid-connected point and the grid-connected point voltage is obtained by simulation, referred to as the reactive characteristic slope η. The photovoltaic reactive power is set to 0, and the characteristic curve oa of the photovoltaic active power and the grid-connected point voltage is obtained by simulation and real data fitting.

[0079] Selection of the lower limit of reactive power regulation threshold: Select point a as the reference point of the maximum PV active power and the corresponding maximum voltage. According to the reactive characteristic slope and the inverter maximum reactive adjustable limit Q max , draw a line segment in the lower half of the voltage-power plane, whose intercept on the voltage horizontal axis is point c, which can be selected as the lower threshold of reactive power regulation.

[0080] Optionally, the above method further includes:

[0081] Determine the target point d of voltage control according to the control target, and the intersection of the vertical line of the target point d and the voltage horizontal coordinate is the voltage value of the control target point;

[0082] Draw a line segment from the above point c to the above target point d to obtain the active boundary curve cd after reactive power control is put into operation;

[0083] The line segment cd intersects the characteristic curve oa at point e, and a vertical line from point e intersects the voltage abscissa at point g, which serves as the upper limit of the threshold of the reactive power regulation.

[0084] Specifically, the selection of the upper threshold of reactive power regulation: point d can be selected as the target point of voltage control according to the control target (see Figure 2 Set to 1.1U n , U n is the rated voltage), and the intersection of the vertical line of this point and the voltage horizontal coordinate is the voltage value of the control target point. Draw a line segment from point c to point d to obtain the active boundary curve cd after reactive power control is put into use. The line segment cd intersects with the characteristic curve oa at point e, and the vertical line drawn from point e intersects with the voltage horizontal coordinate at point g, which can be used as the upper limit of the reactive power regulation threshold.

[0085] In an optional implementation, the above method further includes:

[0086] Set the voltage dead zone of the line segment cd as the active power stability zone;

[0087] Based on the reactive characteristic slope line cb, correction is performed to obtain a corrected slope line cb';

[0088] The voltage dead zone of the modified slope line cb' is set as the preset reactive power stability zone.

[0089] Further optionally, the above correction based on the reactive characteristic slope line cb to obtain the corrected slope line cb' includes:

[0090] Determine the droop limit slope based on the above reactive characteristic slope line cb;

[0091] Determine a reactive power control starting point, the reactive power control starting point being any point between the above point c and the above point g;

[0092] Select the minimum reactive adjustable limit Q lim , based on Q lim The above-mentioned droop limit slope is connected to the above-mentioned reactive power control starting point by an oblique line to determine the above-mentioned correction slope line cb'.

[0093] The above steps are described in detail as follows:

[0094] Reactive power droop slope: The reactive power characteristic slope line cb is used as the droop limit slope -η. Since the slope is obtained through theoretical calculation, necessary corrections can be made according to field tests. The reactive power control starting point can be selected arbitrarily between c and g, but considering the constraints of line loss, it should be as close to point g as possible. After determining the control starting point, select Q lim , Q lim max h, can be based on Q lim The droop limit slope is connected to the reactive power control starting point by a slant line to determine the correction slope line cb', that is, to determine the final droop slope.

[0095] Active power slope: The voltage-active power slope of the controller can be selected according to the cd line. Ideally, the positions of all operating points in the active power working area will be located in the left area of ​​the cd line.

[0096] Stable zone or dead zone setting: To ensure the stability of the control system, it is necessary to set the voltage dead zone of the cd line and cb' line as the active and reactive stable zone, for example Figure 2 The active stable area and reactive stable area shown in FIG. Optionally, the size of the dead zone can be set as required, for example, according to 5% to 10% U n Select.

[0097] See also Figure 2 , Figure 2 A characteristic curve diagram of photovoltaic active power, reactive power and voltage provided in an embodiment of the present application. ​

[0098] like Figure 2 As shown, the horizontal axis is voltage and the vertical axis is power. Figure 2 The upper half of the horizontal axis represents the photovoltaic active power P, which is called the voltage-active half zone; the lower half represents the photovoltaic inductive reactive power Q, which is called the voltage-reactive half zone. Curve oa is the ideal characteristic curve of photovoltaic active power and voltage, and cb is the ideal characteristic curve of photovoltaic inductive reactive power and voltage, with a characteristic slope of -η. As an example, Figure 2 The maximum value of photovoltaic active power corresponds to a voltage of 1.15U n , where U n It is the rated voltage (10kV for medium voltage grid connection and 380V for low voltage grid connection).

[0099] Q max The maximum adjustable reactive power limit of the inverter is equal to 1.15U n The intersection point is b. Draw a straight line with a slope of -η at point b, which intersects with the horizontal axis at point c. This point is the theoretical lower limit voltage threshold of reactive power regulation (the voltage is higher than this point, and reactive power control is put into operation). Draw a vertical line from point c, which intersects with oa at point f. This point is the starting point of the slope change after reactive power control is put into operation. Let point d be the target point of voltage control when the photovoltaic power generation is at its maximum active power, which is 1.1U in this example. n Draw a straight line from point c to point d and intersect with oa at point e. Draw a vertical line from point e and intersect with the horizontal coordinate at point g, which is the theoretical upper voltage threshold of reactive power regulation.

[0100] The voltage value of reactive power input can be arbitrarily selected between point c and point g. Theoretically, the voltage can be controlled within 1.1U n If reactive power control is put into operation at point c, the active power curve will rise along fd at point f; if reactive power control is put into operation at point g, the active power curve will rise along ed at point e. However, in the embodiment of the present application, considering that photovoltaic reactive power absorption will cause additional line loss, the voltage value of reactive power input is as close to point g as possible.

[0101] See also Figure 3 , Figure 3 Another characteristic curve diagram of photovoltaic active power, reactive power and voltage provided in an embodiment of the present application, Figure 3 based on Figure 2 The figure further illustrates the setting of the stability zone.

[0102] Specifically, use Figure 2The explanation of the lines and points in the figure assumes that the reactive power is controlled at the upper limit of the threshold, point g. When the voltage exceeds the position of point g, the reactive power of the inverter will droop along gb'. Since the grid voltage will drop after absorbing reactive power, the operating point of the inverter will gradually stabilize in the reactive stability zone (the area surrounded by g'-g-b'-b") and reach a new balance. At this time, the active power-voltage characteristic curve will become oed. Ideally, all the voltage-active points drawn for this photovoltaic will fall on the left side of the oed curve. In this way, while reducing the grid voltage, the photovoltaic active power output is maximized.

[0103] In practical applications, considering the constraints of network loss (power loss), Q is generally lim <Q max It can be set according to the actual project needs. At the same time, it is also necessary to set the active power control when the inverter reactive power reaches a certain level, which is set to 80%Q in this example. lim .

[0104] In actual applications, the inverter active power-voltage operating points cannot all be on the left side of the curve oed. Due to the random start and stop of loads in the distribution network, the voltage will fluctuate, and some operating points may run to the right side of the curve oed. For illustration, Figure 3 Point A in the figure is a schematic diagram of its position in the voltage-active half zone and voltage-reactive half zone. It can be seen that point A has crossed the ed line in the voltage-active half zone, and its position in the voltage-reactive half zone has exceeded 80% Q lim At this time, active power intervenes, and point A in the voltage-active power half zone will drop along the arrow direction to x%P n Position, limit its active power, and enter the active stability zone. As the active power decreases, the voltage at the photovoltaic grid-connected point will also decrease. At this time, once point A crosses the d'-h' line, it will rise in the direction of the arrow, gradually releasing the active power limit on the inverter. At this time, the position of point A in the active half zone and the reactive half zone will change and reach a new balance. If Q<80%Q lim , and lasts for a certain period of time, active power control exits.

[0105] Based on the above description, the specific control method steps in this application are further explained.

[0106] See also Figure 4 Another flow chart of a method for coordinated droop control of active and reactive power of distributed energy in a distribution network is shown in FIG. Figure 4As shown, the method for coordinated droop control of active and reactive power of distributed energy in the distribution network in the embodiment of the present application includes active power control and reactive power control of the distribution network. The voltage is restricted by setting the "dead zone" of the droop control, and the restriction of single-phase reactive power is added to achieve the control of the distribution network voltage. The specific implementation steps are as follows:

[0107] Step 1: Setting the dead zone range

[0108] By setting the threshold of reactive power control and setting the "dead zone" for the control method, the control effect can be achieved. The slope -η of the droop control curve g-b' is obtained by theoretical calculation and needs to be corrected according to field tests. Set the dead zone as follows Figure 3 The area enclosed by g'-g-b'-b" is shown.

[0109] Step 2: Reactive power control of distribution network

[0110] The three-phase voltage of the distribution network is collected and filtered to determine whether the voltage exceeds the set "dead zone". If not, it returns to continue filtering. When it exceeds the "dead zone", the reactive output is limited / speed-limited through droop control and single-phase reactive power limitation, thereby generating reactive power instructions;

[0111] The above single-phase reactive power limitation can be expressed as follows:

[0112] ifmax(Q x )-min(Q x )>δQ

[0113] thenmin(Q x )=max(Q x )-δQ;

[0114] else

[0115] end

[0116] Among them, Q x is the single-phase reactive power, δQ is a settable parameter, i.e., a limiting parameter.

[0117] Step 3: Active power control of distribution network

[0118] Collect the three-phase voltage of the distribution network, filter it, and determine whether the voltage exceeds the set dead zone. The control range is Figure 3 The left side of the oed curve in the middle, if it has not crossed, returns to continue filtering. When crossing the dead zone, the active power droop controller, single-phase active power limitation, and reactive power command feedback are compared with reactive power output feedback to perform amplitude limiting / speed limiting, generate active power command, and finally realize distribution network voltage control.

[0119] The above single-phase active power limitation can be expressed as follows:

[0120] ifmax(P x )-min(P x )>δP

[0121] thenmin(P x )=max(P x )-δP;

[0122] else

[0123] end

[0124] Among them, P x is the single-phase active power, δP is a settable parameter, i.e., the power limit.

[0125] Step 4: Coordinated control of active and reactive power in distribution network

[0126] By controlling the single-phase active and reactive power of the distribution network at the same time, the single-phase reactive power is set by the reactive power instruction and compared with the actual reactive power output, the active power is controlled, and the corresponding active power instruction is given to set the three-phase active power value P a_set , P b_set , P c_set , the distribution network voltage is controlled by PCS, the specific formula is as follows:

[0127] if Q x ≥θ*Q x_set

[0128] then enable

[0129] Among them, Q x Indicates the actual single-phase reactive power, Q x_set It indicates that the reactive power instruction sets the single-phase reactive power. θ is a settable parameter value, which sets the single-phase limit power.

[0130] Figure 5 A control flow diagram of a distribution network voltage control system provided in an embodiment of the present application is shown in FIG. Figure 5 As shown in the figure, the specific process mainly includes: collecting the three-phase voltage of the distribution network, filtering it through a low-pass filter, and judging whether the voltage exceeds the limit. If it does not exceed the limit, it maintains the normal operation state. If it exceeds the limit, the voltage dead zone specified in the reactive power droop controller is used as the stable zone of active and reactive power. The dead zone size can be 5% to 10% of U nConsidering the constraint of line loss, firstly, point g is used as the starting point of reactive power control. If the voltage can be adjusted within the specified range, the normal operation state is maintained. If the voltage is still at the over-limit value, the reactive power control increases continuously toward point c. When the lower threshold point c of reactive power regulation is reached, the voltage cannot be adjusted to the normal value and is still at the over-limit value, then the active power control intervenes. Under ideal conditions, in the active droop controller, the positions of all operating conditions in the active working area will be located in the left area of ​​the cd line. Through the voltage over-limit range, the corresponding active power command is given to set the three-phase active power value P a_set , P b_set , P c_set , the distribution network voltage can be controlled through PCS.

[0131] in, Figure 5 The specific control expressions or parameters involved can be referred to the description in the aforementioned embodiment and will not be repeated here.

[0132] The embodiment of the present application proposes a method for coordinated droop control of active and reactive power of distributed energy in a distribution network. The method mainly collects the three-phase voltage of the distribution network. When the voltage exceeds the limit, a droop control method is used to coordinate the active and reactive power of the distribution network at the same time. Reactive power control is prioritized to reduce the voltage. When the maximum reactive power threshold is reached and the voltage has not been adjusted to the limited range, active power control intervenes. The active power slope of the droop control is determined to ensure that the active power is in a stable area. Based on the coordinated control of the active and reactive power of the distribution network, the distribution network is controlled on-site. The control method in the embodiment of the present application can solve the problem of large voltage fluctuations of distributed energy in the distribution network, and proposes a new method for controlling active and reactive power at the same time to achieve voltage control, which provides new ideas for subsequent researchers and improves the stability of the distribution network operation.

[0133] Based on the description of the aforementioned method embodiment, the embodiment of the present application also provides a distribution network distributed energy active and reactive coordinated droop control device.

[0134] Figure 6 A schematic diagram of a structure of a distributed energy source active and reactive coordinated droop control device provided in an embodiment of the present application, such as Figure 6 As shown, the device 600 includes:

[0135] The judgment module 610 is used to collect the three-phase voltage of the distribution network, and after filtering, judge whether the three-phase voltage of the distribution network exceeds the limit based on the preset reactive power stability zone;

[0136] The reactive power control module 620 is used to limit the reactive output by reactive droop control and single-phase reactive power limitation, thereby generating reactive power instructions to perform reactive power regulation;

[0137] The active power control module 630 is used to control the active power enable and generate active power instructions to execute active power regulation and control the three-phase voltage of the distribution network when the lower limit of the reactive power regulation threshold is reached and the three-phase voltage of the distribution network is still over the limit, based on the comparison between the single-phase reactive power set by the reactive instruction and the actual reactive power output.

[0138] It can be understood that the relevant contents of each module in the above device have been described in detail in the aforementioned method embodiment, and the specific contents in the method embodiment can be referred to; that is, a distribution network distributed energy active and reactive coordinated droop control device provided in the present application can be executed as follows Figure 1 or Figure 4 Any steps in the illustrated embodiment will not be described in detail here.

[0139] In one embodiment of the present application, an electronic device is also provided. The electronic device may include a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the execution Figure 1 or Figure 4 Any step in the method embodiment shown. The electronic device may also include an input / output device, etc. In a specific implementation, the electronic device may be a terminal device, etc.

[0140] In one embodiment, a computer-readable storage medium is further provided. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the processor executes any step in the above method embodiment.

[0141] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0142] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0143] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for coordinated droop control of active and reactive power of distributed energy in a distribution network, characterized in that: The method comprises: Collect the three-phase voltage of the distribution network, filter it, and determine whether the three-phase voltage of the distribution network exceeds the limit based on the preset reactive power stability zone; If so, the reactive output is limited / speed-limited through reactive droop control and single-phase reactive limitation, thereby generating reactive commands to perform reactive power regulation; When the lower limit of the reactive power regulation threshold is reached and the three-phase voltage of the distribution network is still out of limit, the active power is enabled and an active power instruction is generated based on the comparison between the single-phase reactive power set by the reactive power instruction and the actual reactive power output to execute active power regulation and control the three-phase voltage of the distribution network.

2. The method for coordinated droop control of active and reactive power of distributed energy in distribution network according to claim 1 is characterized in that: The method further comprises: Simplify and equate the formal topology of the distribution network to obtain the equivalent topological structure; According to the equivalent topological structure, modeling and simulation are performed to obtain a characteristic slope curve between different reactive powers of the photovoltaic grid-connected point and the grid-connected point voltage through simulation, thereby obtaining a reactive characteristic slope; The photovoltaic reactive power is set to 0, and the characteristic curve oa between the photovoltaic active power and the grid connection point voltage is obtained through simulation and real data fitting; Selecting point a in the characteristic curve oa as the reference point of the maximum photovoltaic active power and the corresponding maximum voltage; According to the reactive characteristic slope and the inverter maximum reactive adjustable limit Q max , a line segment is drawn in the lower half of the voltage-power plane, and its intercept on the voltage abscissa is point c, which serves as the lower limit of the reactive power regulation threshold.

3. The method for coordinated droop control of active and reactive power of distributed energy in distribution network according to claim 2 is characterized in that: The method further comprises: Determine a target point d for voltage control according to the control target, and the intersection of the vertical line of the target point d and the voltage horizontal coordinate is the voltage value of the control target point; Draw a line segment from the point c to the target point d to obtain the active power boundary curve cd after reactive power control is put into operation; The line segment cd intersects the characteristic curve oa at point e, and a vertical line from point e intersects the voltage abscissa at point g, which serves as the upper limit of the reactive power regulation threshold.

4. The method for coordinated droop control of active and reactive power of distributed energy in distribution network according to claim 1 is characterized in that: The method further comprises: Setting the voltage dead zone of the line segment cd as an active power stability zone; Based on the reactive characteristic slope line cb, correction is performed to obtain a corrected slope line cb'; The voltage dead zone of the modified slope line cb' is set as the preset reactive power stability zone.

5. The method for coordinated droop control of active and reactive power of distributed energy in distribution network according to claim 4 is characterized in that: The method of performing correction based on the reactive characteristic slope line cb to obtain a corrected slope line cb' comprises: Determine the droop limit slope according to the reactive characteristic slope line cb; Determine a reactive power control starting point, where the reactive power control starting point is any point between point c and point g; Select the minimum reactive adjustable limit Q lim , based on Q lim The droop limit slope is connected to the reactive power control starting point by an oblique line to determine the correction slope line cb'.

6. The method for coordinated droop control of active and reactive power of distributed energy in distribution network according to claim 1, characterized in that: The single-phase reactive power limitation is expressed as follows: ifmax(Q x )-min(Q x )>δQ thenmin(Q x )=max(Q x )-δQ; else end Among them, Q x is the single-phase reactive power, and δQ is the reactive power limit parameter.

7. The method for coordinated droop control of active and reactive power of distributed energy in distribution network according to claim 6 is characterized in that: The single-phase active power limitation is expressed as follows: ifmax(P x )-min(P x )>δP thenmin(P x )=max(P x )-δP; else end Among them, P x is the single-phase active power, and δP is the active power limit parameter.

8. A coordinated droop control device for active and reactive power of distributed energy in a distribution network, characterized in that: include: A judgment module is used to collect the three-phase voltage of the distribution network, and after filtering, judge whether the three-phase voltage of the distribution network exceeds the limit based on a preset reactive power stability zone; A reactive power control module is used to limit the reactive output by reactive droop control and single-phase reactive power limitation, thereby generating reactive power instructions to perform reactive power regulation; The active power control module is used to control the active power enable and generate an active power instruction to execute active power regulation and control the three-phase voltage of the distribution network when the lower limit of the reactive power regulation threshold is reached and the three-phase voltage of the distribution network is still over the limit, based on the comparison between the single-phase reactive power set by the reactive instruction and the actual reactive power output.

9. An electronic device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

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