Multi-resource distributed cooperative control method for elastic power distribution network

Abstract

The invention discloses a multi-resource distributed cooperative control method for an elastic power distribution network, and relates to the technical field of power distribution network fault recovery, and the multi-resource distributed cooperative control method based on heterogeneous dynamic partition operation comprises the steps: carrying out the heterogeneous definition of an island partition of a post-disaster power distribution network according to the spatial distribution of GFLS, GFMS and SOP, and carrying out the fault recovery of the power distribution network; therefore, a distributed cooperative controller of multi-type resources is designed, fault recovery cooperative control of the post-disaster distributed elastic power distribution network under the heterogeneous dynamic island partition is realized, and the problem that the cooperative recovery potential of the multi-type resources is not fully excavated in the traditional active island recovery technology is solved. The method has important significance for improving the fault recovery capability and the operation flexibility of the power distribution network, the utilization efficiency of resources is improved, and important technical support is provided for constructing a novel power system with high toughness and high reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network fault recovery, and particularly to a multi-resource distributed collaborative control method for an elastic distribution network. Background Art

[0002] In recent years, extreme events such as natural disasters and potential geopolitical conflicts have seriously threatened the safe and stable operation of the distribution network, posing higher requirements for the post-disaster fault recovery ability of the distribution network. With the gradual construction of the new power system, the development of a highly reliable and elastic distribution network is imperative. As one of the important technical means for distribution network recovery under fault scenarios, the active island restoration technology enables the distribution network to be quickly divided into multiple island areas after a fault occurs by real-time monitoring and analyzing the operating state of the distribution network, and each island partition can operate independently through internal recovery resources. The application of the active island restoration technology can quickly restore the power-off load and improve the emergency response ability and operating flexibility of the distribution network.

[0003] Existing research on the active island restoration technology mostly focuses on static restoration areas, that is, multiple independent island partitions operate within predefined electrical boundaries and cooperate with internal DGs to restore the power-off load. However, in this static restoration structure, the partitions only exchange power through fixed lines at static points of common coupling, which limits the interaction between partitions, and the distribution system operates in a suboptimal state and is difficult to flexibly respond to changes in load and DG output power. Therefore, it is necessary to apply a dynamic and flexible electrical boundary during the fault recovery process to form a scalable and expandable dynamic recovery area (DRA).

[0004] Meanwhile, with the proposal of the "dual carbon" goal, the access of a high proportion of distributed generation (DG) and a high proportion of new power electronic devices provides important recovery resources for the distribution network to cope with extreme events, but also makes the recovery resources more distributed and diversified. Most existing studies focus on grid-forming sources (GFMS), and only regard GFLS as an unregulated load. However, according to the advocacy of IEEE1547, the participation of GFLS in the frequency / voltage regulation of the distribution network can provide certain benefits and enhance the operating flexibility of the distribution network. Therefore, it is necessary to consider the distributed collaborative control of various types of recovery resources in heterogeneous partitions formed during the fault recovery process to tap the recovery potential of important resources. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a multi-resource distributed collaborative control method for elastic distribution networks, which solves the problems that traditional active island restoration technologies do not consider the dynamic changes of heterogeneous partition electrical boundaries and the collaborative control of various types of restoration resources within them, and provides technical support for the collaborative fault restoration of various types of distributed resources after the disaster of the distribution network.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] A multi-resource distributed collaborative control method for elastic distribution networks proposed according to the present invention includes:

[0008] Step 1: Clarify the post-disaster distributed restoration resources in different dynamic restoration areas (DRA) divided in the post-disaster distribution network;

[0009] Differentially classify heterogeneous DRAs according to the distributed restoration resources in the post-disaster distribution network within different DRAs. The heterogeneous DRAs after differential classification include network construction support type DRA, network following supplement type DRA, network construction and following hybrid type DRA, and power outage area;

[0010] Step 2: Determine the primary control methods of different types of restoration resources under heterogeneous DRAs; among them, different types of restoration resources include network construction type resources (GFMS), network following type resources (GFLS), and intelligent soft switches (SOP);

[0011] Step 3: Decompose the collaborative control objectives of different types of restoration resources within heterogeneous DRAs into voltage / frequency non-differential restoration and power sharing, and design the collaborative secondary control variables of different types of restoration resources within the DRA according to the collaborative control objectives;

[0012] Step 4: Perform cross-interval interaction on heterogeneous DRAs, and the cross-interval interaction of heterogeneous DRAs includes the merger and separation of DRAs;

[0013] Adjust the state variables of intelligent switches (SSW) during the cross-interval interaction of heterogeneous DRAs: The state variables adjusted by the intelligent switch SSW are used as the secondary control objectives, and the SSW adjustment secondary control variables of different types of restoration resources are designed according to the state variables adjusted by the SSW;

[0014] Step 5: Based on the designed collaborative secondary control variables of different types of restoration resources within the DRA and the SSW adjustment secondary control variables of different types of restoration resources, after the distribution network resumes power supply, the restoration resources within the distribution network act together to adjust the synchronous operation of the distribution network and the large power grid. After the grid connection switch closes when meeting the preset conditions, the restoration resources within the distribution network will switch to the grid connection mode, and the distribution network resumes operation.

[0015] As a further optimization scheme of the multi-resource distributed collaborative control method for elastic distribution networks described in the present invention, in step 2,

[0016] The GFMS independently supports the grid voltage and frequency, and droop control is adopted for primary control to form a network;

[0017] The GFLS operates in coordination with the GFMS. The GFLS adopts inverse droop control to make the GFLS exhibit power droop characteristics;

[0018] One end of the SOP adopts U dc The Q control maintains the stability of the DC capacitor voltage, and the other end of the SOP acts as the GFMS to participate in load restoration;

[0019] In step 4, the implementation method of the merger and separation of the DRA is as follows: adjust the state of the intelligent switch SSW. When the voltage amplitude difference and phase angle difference at both ends of the SSW are close to 0, the SSW closes. When the active power and reactive power flowing through the SSW are close to 0, the SSW disconnects;

[0020] The state variables adjusted by the SSW include the voltage amplitude difference and voltage phase angle difference at both ends of the SSW, as well as the active power and reactive power flowing through the SSW;

[0021] After the DRA is merged or separated, only the recovery resources inside the DRA are coordinated and controlled.

[0022] As a further optimization scheme of the elastic distribution network multi-resource distributed collaborative control method described in the present invention,

[0023] The network-forming support type DRA only includes the GFMS. The network-forming support type DRA can black-start and restore the load, and support the grid voltage and frequency;

[0024] The network-following supplementary type DRA only includes the GFLS. The network-following supplementary type DRA is interconnected with the DRA with the GFMS through the SOP, so as to transmit power to drive the GFLS to start, and cooperate to restore the powered-off load;

[0025] The network-forming and following hybrid type DRA includes the GFMS and the GFLS. Among them, while the GFMS black-starts and restores the load, it drives the GFLS in the region to start, and the two cooperate to restore the powered-off load;

[0026] There is no distributed power source DG or only the GFLS exists in the powered-off area. The powered-off area does not have the ability to black-start and restore the load, and the powered-off area is regarded as an inadjustable load;

[0027] In the heterogeneous DRA partitions after differential classification, the network-following supplementary type DRA is connected to the network-forming support type DRA or the network-forming and following hybrid type DRA through the SOP, and realizes dynamic soft expansion through continuous adjustment of the transmitted power; The DRAs that are not interconnected through the SOP are connected through the SSW, and the 0-1 action of the SSW is used to realize dynamic hard expansion.

[0028] As a further optimization scheme of the elastic distribution network multi - resource distributed collaborative control method described in the present invention,

[0029] It is assumed that the communication links between DGs are connected and undirected, and can be connected and disconnected following the merger or separation of the heterogeneous DRA partitions after differential classification;

[0030] GFMS adopts primary droop control for networking, and additional distributed secondary control variables are added to GFMS to achieve the regulation of voltage, frequency, active power, and reactive power; specifically as follows:

[0031]

[0032] Among them, Δu i and Δv i respectively represent the total secondary control variables of the active - frequency droop and reactive - voltage droop distributed controllers of the i - th GFMS, ω i is the operating frequency of the i - th DG, is the reference value of the operating frequency of the i - th DG, m i is the active - frequency droop coefficient of the i - th DG, P i is the active power output by the i - th DG, V i is the operating voltage of the i - th DG, V i ref is the reference value of the operating voltage of the i - th DG, n i is the reactive - voltage droop coefficient of the i - th DG, Q i is the reactive power output by the i - th DG.

[0033] As a further optimization scheme of the elastic distribution network multi - resource distributed collaborative control method described in the present invention,

[0034] GFLS adopts primary inverse - droop control to participate in collaborative operation, and additional distributed secondary control variables are added to GFLS to achieve the regulation of voltage, frequency, active power, and reactive power; specifically as follows:

[0035]

[0036] Among them, Δp i and Δq i respectively represent the total secondary control variables of the active - frequency inverse - droop and reactive - voltage inverse - droop distributed controllers of the i - th GFLS, w i is the active - frequency inverse - droop coefficient of the i - th DG, Q i is the reactive power output by the i - th DG, h i is the reactive - voltage inverse - droop coefficient of the i - th DG.

[0037] As a further optimization scheme of the multi - resource distributed collaborative control method for the elastic distribution network described in the present invention, the other end of the SOP acts as the GFMS to participate in load restoration, specifically as follows:

[0038] The ports where the SOP acts as the GFMS are networked using primary droop control, and distributed secondary control variables are designed to participate in coordinated operation;

[0039]

[0040] Among them, Δu sop and Δv sop respectively represent the total secondary control variables of the active - frequency droop and reactive - voltage droop distributed controllers at the ports where the SOP acts as the GFMS, ω sop is the operating frequency at the ports where the SOP acts as the GFMS, is the reference value of the operating frequency at the ports where the SOP acts as the GFMS, m sop is the active - frequency droop coefficient at the ports where the SOP acts as the GFMS, P sop is the output active power at the ports where the SOP acts as the GFMS, V sop is the operating voltage at the ports where the SOP acts as the GFMS, is the reference value of the operating voltage at the ports where the SOP acts as the GFMS, n sop is the reactive - voltage droop coefficient at the ports where the SOP acts as the GFMS, Q sop is the output reactive power at the ports where the SOP acts as the GFMS.

[0041] As a further optimization scheme of the multi - resource distributed collaborative control method for the elastic distribution network described in the present invention, the goal of coordinated control of multiple types of restoration resources in the heterogeneous DRA is decomposed into voltage / frequency restoration without error and power sharing, specifically as follows:

[0042] For the coordinated control of multiple types of resources in the heterogeneous DRA, the GFMS secondary controller variables Δu S and Δv S are:

[0043]

[0044] Among them, and Δω i 、ΔV i respectively represent the deviations of the operating frequency and voltage from the reference values; aij represents whether there is a communication link between the i - th DG and the j - th DG. If there is, the value is 1, otherwise it is 0; ΔP′ ij =P i ′ - P j ′ and ΔQ′ ij =Q i′-Q j ′, ΔP′ ij 、Q' ij respectively represent the active and reactive power deviations of the output of the i-th DG and the j-th DG; c f 、c p 、c v 、c q respectively represent Δω i 、ΔP′ ij 、ΔV i 、ΔQ′ ij corresponding gains; α i indicates whether voltage regulation is enabled, P i ′ is the unit active power output by the i-th DG, P j ’ is the unit active power output by the j-th DG, Q i ’ is the unit reactive power output by the i-th DG, Q j ’ is the unit reactive power output by the j-th DG;

[0045] For the coordinated control of multiple types of resources in a heterogeneous DRA, the GFLS secondary controller variables Δp S and Δq S are:

[0046]

[0047] Among them, c fg 、c pg 、c vg 、c qg respectively represent Δω i 、ΔP ij 、ΔV i 、ΔQ ij corresponding gains; E rate represents the rated capacity value of the inverter; ΔP ij =P i -P j and ΔQ ij =Q i -Q j ,ΔP ij 、ΔQ ij respectively represent the active and reactive power deviations of the output of the i-th DG and the j-th DG, P j is the active power output by the j-th DG, Q j is the reactive power output by the j-th DG;

[0048] For the coordinated control of multiple types of resources in a heterogeneous DRA, the SOP acts as the secondary control variables Δu sopS and Δv sopS are designed as:

[0049]

[0050] Among them, and Δω sop and Δv sopS respectively represent the deviations of the operating frequency and voltage from the reference values; asop,j represents whether there is a communication link between the port where the SOP acts as the GFMS and the j-th DG in the network-connected complementary DRA. If it exists, the value is 1; otherwise, it is 0; ΔQ′ sop,j = Q′ sop -Q j ’, ΔQ′ sop,j represents the deviation of the unit reactive power output by the SOP acting as the GFMS port and the j-th DG in the network-connected complementary DRA; σ represents whether voltage regulation is enabled, Q s ’ op is the unit reactive power output by the SOP acting as the GFMS port, and Q j ’ is the unit reactive power output by the j-th DG.

[0051] As a further optimization scheme of the multi-resource distributed cooperative control method for the elastic distribution network described in the present invention, when the voltage amplitude and phase angle difference at both ends of the SSW are close to 0, the SSW is closed; when the active power and reactive power flowing through the SSW are close to 0, the SSW is disconnected; the state variables adjusted by the SSW are used as the secondary control objectives, and different types of restoration resources are designed for the secondary control variables of the SSW according to the state variables adjusted by the SSW; specifically as follows:

[0052] For adjusting the state of the SSW, the secondary control variables Δu T and Δv T of the GFMS are designed as follows:

[0053]

[0054] Among them, Δθ SSW,k and ΔV SSW,k respectively represent the voltage phase and amplitude deviations at both ends of the k-th SSW; ΔP′ SSW,k and ΔQ′ SSW,k respectively represent the unit active and reactive powers flowing through the k-th SSW; β i and γ i respectively represent whether the i-th DG participates in adjusting the state of the SSW to meet the closing or opening conditions. When the SSW changes from open to closed, β i = 1, γ i = 0; when the SSW changes from closed to open, β i = 0, γ i = 1; when the SSW does not act, β i= 0, γ i = 0; c t , c sp , c o , c sq respectively represent Δθ SSW,k , ΔP’ SSW,k , ΔV SSW,k , ΔQ’ SSW,k corresponding gains;

[0055] Adjust the state of the SSW, and the secondary control variables Δp T and Δq T are designed as follows:

[0056]

[0057] where, c tg , c spg , c og , c sqg respectively represent Δθ SSW,k , ΔP SSW,k , ΔV SSW,k , ΔQ SSW,k corresponding gains; ΔP SSW,k and ΔQ SSW,k respectively represent the active and reactive powers flowing through the k-th SSW;

[0058] Only when the SOP acts as the port of the GFMS to connect the two ends of the SSW to adjust the amplitude or the reactive power flow, enable the secondary control variable Δv of the SOP acting as the port of the GFMS to adjust the state of the SSW sopT , and the design is as follows:

[0059] Δv sopT = c o ηΔV SSW,k + c sq μΔQ' SSW,k (9)

[0060] where, η and μ respectively represent whether the SOP acting as the port of the GFMS needs to participate in adjusting the closing and opening of the SSW. If so, the value is 1, otherwise it is 0; ΔQ' SSW,k is the unit reactive power flowing through the k-th SSW.

[0061] As a further optimization scheme of the elastic distribution network multi-resource distributed collaborative control method described in the present invention, the grid-connected switch closes when it meets the preset conditions. The preset conditions refer to that the distribution network operates synchronously with the upstream large power grid. The synchronous operation of the distribution network and the upstream large power grid means that the voltage amplitude difference and voltage phase angle difference at both ends of the grid-connected switch are close to 0; specifically as follows:

[0062] For the state regulation of the grid-connected switch, the secondary control variables Δu R and Δv R are designed as follows:

[0063]

[0064] where, Δθ C and ΔV C respectively represent the voltage phase and amplitude deviation at both ends of the grid-connected switch; λ i indicates whether the i-th DG needs to participate in regulating the state of the grid-connected switch to meet the closing condition. When the grid connection command is issued, λ i = 1, otherwise λ i = 0; c θ , c z respectively represent the gains corresponding to Δθ C and ΔV C ;

[0065] For the state regulation of the grid-connected switch, the secondary control variables Δp R and Δq R are designed as follows:

[0066]

[0067] where, c θg , c zg respectively represent the gains of the corresponding secondary controller variables;

[0068] Only when regulating the amplitude at both ends of the grid-connected switch connected to the port acting as GFMS or regulating the reactive power flow, enable the SOP to act as the secondary control variable Δv sopR for regulating the state of the grid-connected switch at the GFMS port, and the design is as follows:

[0069] Δv sopR = c z δΔV C (12)

[0070] where, δ indicates whether the port of the SOP acting as GFMS needs to participate in regulating the closing of the grid-connected switch. If so, the value is 1, otherwise it is 0, and σ in equation (6) = 1 - η - μ - δ.

[0071] As a further optimization scheme of the multi-resource distributed collaborative control method for the elastic distribution network described in the present invention,

[0072]

[0073] where, k pi and k ii respectively represent the proportional coefficient and integral coefficient of the PI link.

[0074] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0075] The elastic distribution network multi-resource distributed collaborative control method based on heterogeneous dynamic partition operation can not only flexibly adjust the electrical boundary of the island partition and quickly respond to the reconstruction instruction, but also fully exploit the collaborative restoration potential of various types of resources in the network, and continuously and stably supply power to the de-energized load by using the restoration resources as much as possible. This method is of great significance for improving the fault restoration ability and operation flexibility of the distribution network, improving the utilization efficiency of resources, and providing important technical support for building a new type of power system with high toughness and high reliability. Description of the Drawings

[0076] Figure 1 is the method flow chart of the present invention;

[0077] Figure 2 is the schematic diagram of heterogeneous DRA attribute division of the present invention;

[0078] Figure 3 is the collaborative control block diagram of different types of restoration resources in multiple heterogeneous DRAs of the present invention;

[0079] Figure 4 are the experimental results obtained by using the present invention; among them, (a) SSW is closed, (b) SSW is disconnected, and (c) the grid connection switch is closed. Detailed Embodiments

[0080] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0081] As Figure 1 shown is the method flow chart of the present invention. A kind of elastic distribution network multi-resource distributed collaborative control method based on heterogeneous dynamic partition operation of the present invention includes the following steps:

[0082] 1) Clarify the post-disaster distributed restoration resources in different dynamic restoration areas DRA divided in the post-disaster distribution network; classify the heterogeneous DRA differently according to the post-disaster distributed restoration resources in the post-disaster distribution network in different DRAs. The heterogeneous DRA after differential classification includes network construction support type DRA, network following supplement type DRA, network construction and following hybrid type DRA and power outage area.

[0083] Figure 2 is the schematic diagram of heterogeneous DRA attribute division of the present invention. As Figure 2 shown by the network construction support type DRA in (the yellow box in the figure), only GFMS is included in the network construction support type DRA, which can quickly black start to restore the load and support the grid voltage and frequency; as Figure 2As shown by the grid-following supplementary DRA in [Figure] (the purple box in the figure), the grid-following supplementary DRA only includes GFLS and needs to be interconnected with the DRA with GFMS through SOP to transmit power to drive the start of GFLS and cooperate to restore the power-loss load; such as Figure 2 As shown by the structure-following hybrid DRA in [Figure] (the green box in the figure), the structure-following hybrid DRA includes GFMS and GFLS. Among them, while GFMS quickly black-starts to restore the load, it drives the start of GFLS in the area, and the two cooperate to restore the power-loss load; such as Figure 2 As shown by the power-loss area in [Figure] (the blue box in the figure), there is no distributed power source DG or only GFLS exists in the power-loss area. The power-loss area does not have the ability to black-start and restore the load, and the power-loss area is regarded as an uncontrollable load.

[0084] In the heterogeneous DRA partitions after differential classification, the grid-following supplementary DRA is connected to the grid-forming supporting DRA or the structure-following hybrid DRA through SOP, and realizes dynamic soft scaling through continuous adjustment of the transmitted power; the DRAs not interconnected through SOP are connected through SSW, and the 0-1 action of SSW is used to realize dynamic hard scaling.

[0085] 2) Determine the primary control methods of different types of restoration resources under heterogeneous DRA. Different types of restoration resources include the grid-forming resource GFMS, the grid-following resource GFLS, and the intelligent soft switch SOP; among them, GFMS independently supports the grid voltage and frequency, and the primary control uses droop control to form a network; GFLS operates in cooperation with GFMS, and GFLS uses inverse droop control to make GFLS exhibit power droop characteristics; one end of SOP uses UdcQ control to maintain the stability of the DC capacitor voltage, and the other end of SOP acts as GFMS to participate in load restoration.

[0086] Figure 3 is the cooperative control block diagram of different types of restoration resources in the multi-heterogeneous DRA of the present invention. In Figure 3 the green block diagrams in [Figure] respectively depict the primary control methods of GFMS, GFLS, and the port of SOP acting as GFMS.

[0087] It is assumed that the communication links between each DG are connected and undirected, and can be connected and disconnected following the merger or separation of the heterogeneous DRA partitions after differential classification.

[0088] GFMS uses primary droop control to form a network, and additional distributed secondary control variables are added to GFMS to achieve the regulation of voltage frequency and active and reactive power; specifically as follows:

[0089]

[0090] Among them, Δu i and Δv irespectively represent the total secondary control variables of the active-frequency droop and reactive-voltage droop distributed controllers of the i-th GFMS, ω i is the operating frequency of the i-th DG, is the reference value of the operating frequency of the i-th DG, m i is the active-frequency droop coefficient of the i-th DG, P i is the active power output by the i-th DG, V i is the operating voltage of the i-th DG, V i ref is the reference value of the operating voltage of the i-th DG, n i is the reactive-voltage droop coefficient of the i-th DG, Q i is the reactive power output by the i-th DG.

[0091] GFLS cannot achieve autonomous grid-forming and stable operation. It is difficult to respond in a timely manner to the changes in the output power of GFMS and different cooperative control objectives using traditional PQ control. To maximize its regulation ability, inverted droop control is adopted to make it exhibit power droop characteristics and achieve cooperative operation with GFMS. The control strategy is designed as follows:

[0092]

[0093] where, Δp i and Δq i respectively represent the total secondary control variables of the active-frequency inverted droop and reactive-voltage inverted droop distributed controllers of the i-th GFLS, w i is the active-frequency inverted droop coefficient of the i-th DG, Q i is the reactive power output by the i-th DG, h i is the reactive-voltage inverted droop coefficient of the i-th DG.

[0094] The SOP of the present invention adopts a back-to-back converter structure. The DC sides of the two converters are connected by a DC capacitor to form a two-port SOP. One port adopts U dc Q control to maintain the stability of the DC capacitor voltage, and the other port acts as GFMS. U dc Q control is a control method of SOP. U dc refers to the DC capacitor voltage of SOP, and Q refers to the reactive power output by the port of SOP adopting U dc Q control. The control strategy is designed as:

[0095]

[0096] where, i dref is the d-axis current reference value of the current inner loop control, i qref is the q-axis current reference value of the current inner loop control; k pi and kii are the proportional and integral coefficients of the PI controller; U dcref and U dc are the reference value and the actual value of the DC capacitor voltage respectively; Q ref and Q are the reference value and the actual value of the output reactive power respectively. Here, to simplify the communication structure and avoid reactive power circulation, the reactive power output from this port is controlled to be 0, that is, Q ref is set to 0.

[0097] The ports where the SOP acts as the GFMS adopt primary droop control for networking, and distributed secondary control variables are designed to participate in coordinated operation, specifically as follows:

[0098]

[0099] Among them, Δu sop and Δv sop represent the total secondary control variables of the active - frequency droop and reactive - voltage droop distributed controllers of the port where the SOP acts as the GFMS respectively, ω sop is the operating frequency of the port where the SOP acts as the GFMS, is the reference value of the operating frequency of the port where the SOP acts as the GFMS, m sop is the active - frequency droop coefficient of the port where the SOP acts as the GFMS, P sop is the output active power of the port where the SOP acts as the GFMS, V sop is the operating voltage of the port where the SOP acts as the GFMS, is the reference value of the operating voltage of the port where the SOP acts as the GFMS, n sop is the reactive - voltage droop coefficient of the port where the SOP acts as the GFMS, Q sop is the output reactive power of the port where the SOP acts as the GFMS.

[0100] 3) The objectives of the coordinated control of different types of restoration resources in the heterogeneous DRA are decomposed into voltage / frequency restoration without error and power sharing. Among them, after the DRA is merged or separated, only the restoration resources inside the DRA are coordinated and controlled, and the coordinated secondary control variables of different types of restoration resources in the DRA are designed according to the coordinated control objectives.

[0101] As Figure 3 shown, the stable operation control objectives in the heterogeneous DRA area include frequency restoration without error, power sharing, and voltage restoration without error, and subsequent designs of the secondary controller variables of different types of restoration resources are carried out based on this coordinated control objective. Figure 3 also gives the secondary controller variables corresponding to the stable operation in the area for the GFMS, GFLS, and SOP.

[0102] For the coordinated control of multiple types of resources in a heterogeneous DRA, the GFMS secondary controller variables Δu S and Δv S are as follows:

[0103]

[0104] Among them, and Δω i 、ΔV i respectively represent the deviations of the operating frequency and voltage from the reference values; a ij indicates whether there is a communication link between the i-th DG and the j-th DG. If there is, the value is 1; otherwise, it is 0; ΔP′ ij =P i ’-P j ′ and ΔQ′ ij =Q i ′-Q j ′, ΔP′ ij 、Q′ ij respectively represent the deviations of the unit active and reactive power outputs of the i-th DG and the j-th DG; c f 、c p 、c v 、c q respectively represent the gains corresponding to Δω i 、ΔP′ ij 、ΔV i 、ΔQ′ ij ; α i indicates whether voltage regulation is enabled, P′ i is the unit active power output of the i-th DG, P j ′ is the unit active power output of the j-th DG, Q i ′ is the unit reactive power output of the i-th DG, Q j ′ is the unit reactive power output of the j-th DG.

[0105] For the coordinated control of multiple types of resources in a heterogeneous DRA, the GFLS secondary controller variables Δp S and Δq S are as follows:

[0106]

[0107] Among them, c fg 、c pg 、c vg 、c qg respectively represent the gains corresponding to Δω i 、ΔP ij 、ΔV i 、ΔQ ij ; Erate Represents the rated capacity value of the inverter; ΔP ij = P i - P j and ΔQ ij = Q i - Q j , ΔP ij , ΔQ ij respectively represent the active and reactive power deviations of the i-th DG and the j-th DG outputs. P j is the active power output by the j-th DG, and Q j is the reactive power output by the j-th DG.

[0108] According to the SOP determined in step 2), it acts as a port of the GFMS and uses primary droop control to form a network. Similarly, corresponding distributed secondary control variables are designed to participate in coordinated operation. Since the SOP itself does not generate power and the transmitted active power at both ends needs to be equal, the equal sharing of active power only considers the DGs within the two interconnected partitions, while the output reactive power can be controlled arbitrarily. Considering the reactive power equal sharing between the DGs within this port and the grid-connected supplementary DRA. For the coordinated control of multiple types of resources within the heterogeneous DRA, the secondary control variables Δu sopS and Δv sopS are designed as:

[0109]

[0110] where and Δω sop , Δv sopS respectively represent the deviations of the operating frequency and voltage from the reference values; a sop,j represents whether there is a communication link between the port where the SOP acts as the GFMS and the j-th DG within the grid-connected supplementary DRA. If there is, the value is 1, otherwise it is 0; ΔQ′ sop,j = Q′ sop - Q j ′, ΔQ' sop,j represents the unit reactive power deviation of the output of the port where the SOP acts as the GFMS and the j-th DG within the grid-connected supplementary DRA; σ represents whether voltage regulation is enabled, and Q s ′ op is the unit reactive power output of the port where the SOP acts as the GFMS, and Q j ′ is the unit reactive power output by the j-th DG.

[0111] 4) The heterogeneous DRA cross-region interaction includes the merging and separation of DRAs, and adjusts the state of the intelligent switch SSW. When the voltage amplitude difference and phase angle difference at both ends of the SSW approach 0, the SSW closes; when the active power and reactive power flowing through the SSW approach 0, the SSW disconnects; thus realizing the merging and separation between different heterogeneous DRAs. The state variables adjusted by the SSW are used as the secondary control objectives, and the secondary control variables for the SSW adjustment of different types of restoration resources are designed according to the state variables adjusted by the SSW. Among them, the state variables include the voltage amplitude difference at both ends of the SSW, the voltage phase angle difference at both ends, the active power and reactive power flowing through the SSW.

[0112] As Figure 3 shown, the smooth interaction control objectives between heterogeneous DRA regions include the SSW closing adjustment and the SSW disconnecting adjustment, and subsequent designs of secondary controller variables for different types of restoration resources are carried out based on this collaborative control objective. Figure 3 also gives the secondary controller variables of GFMS, GFLS, and SOP corresponding to the SSW state adjustment in the smooth interaction between regions.

[0113] For adjusting the state of the SSW, the secondary control variables Δu T and Δv T of GFMS are designed as follows:

[0114]

[0115] Among them, Δθ SSW,k and ΔV SSW,k respectively represent the voltage phase and amplitude deviation at both ends of the k-th SSW; ΔP′ SSW,k and ΔQ′ SSW,k respectively represent the unit active and reactive power flowing through the k-th SSW; β i and γ i respectively represent whether the i-th DG participates in adjusting the SSW state to meet the closing or disconnecting conditions. When the SSW changes from disconnecting to closing, β i = 1, γ i = 0; when the SSW changes from closing to disconnecting, β i = 0, γ i = 1; when the SSW does not act, β i = 0, γ i = 0; c t 、c sp 、c o 、c sq respectively represent the gains corresponding to Δθ SSW,k 、ΔP′ SSW,k 、ΔV SSW,k 、ΔQ′ SSW,k 。

[0116] Adjust the state of the SSW, and the secondary control variables Δp of the GFLS T and Δq T are designed as follows:

[0117]

[0118] where c tg 、c spg 、c og 、c sqg represent the gains corresponding to Δθ SSW,k 、ΔP SSW,k 、ΔV SSW,k 、ΔQ SSW,k respectively; ΔP SSW,k and ΔQ SSW,k represent the active and reactive powers flowing through the k-th SSW respectively.

[0119] The SOP uses U dc There is no secondary control variable at the port where Q maintains the DC voltage stability. Since the active power output at both ends of the SOP is equal and the reactive power output at both ends is arbitrarily controllable, the corresponding secondary control variable Δv is enabled only when the amplitude or reactive power flowing through both ends of the SSW needs to be adjusted at this port. The design is as follows: sopT is designed as follows:

[0120] Δv sopT =c o ηΔV SSW,k +c sq μΔQ' SSW,k (10)

[0121] where η and μ represent whether the port where the SOP acts as the GFMS needs to participate in adjusting the closing and opening of the SSW. If it is needed, the value is 1, otherwise it is 0; ΔQ' SSW,k is the unit reactive power flowing through the k-th SSW.

[0122] 5) After the power supply of the distribution network is restored, the restoration resources in the distribution network act together to adjust the synchronous operation of the distribution network and the large power grid. After the grid connection switch closes under the preset conditions, the restoration resources in the distribution network will switch to the grid connection mode, and the distribution network resumes operation. The preset condition for the grid connection switch to close is that the voltage amplitude difference and voltage phase angle difference at both ends of the grid connection switch are close to 0.

[0123] As Figure 3 shown, the smooth interaction control objectives between heterogeneous DRA regions include the adjustment of the grid connection switch closing, and subsequent designs of the secondary controller variables for different types of restoration resources are carried out based on this cooperative control objective. In Figure 3Also given are the secondary controller variables of GFMS, GFLS, and SOP corresponding to the regulation of the grid-connected switch status during the stable interaction between regions.

[0124] For the regulation of the grid-connected switch status, the secondary control variables Δu R and Δv R of GFMS are designed as follows:

[0125]

[0126] where, Δθ C and ΔV C respectively represent the voltage phase and amplitude deviation at both ends of the grid-connected switch; λ i indicates whether the i-th DG needs to participate in regulating the grid-connected switch status to meet the closing condition. When the grid connection command is issued, λ i = 1, otherwise λ i = 0; c θ , c z respectively represent the gains corresponding to Δθ C and ΔV C .

[0127] For the regulation of the grid-connected switch status, the secondary control variables Δp R and Δq R of GFLS are designed as follows:

[0128]

[0129] where, c θg , c zg respectively represent the gains of the corresponding secondary controller variables.

[0130] Similar to the control of SOP in the DRA cross-region interaction regulation of the SSW status, only when the amplitude at both ends of the grid-connected switch connected to the port acting as GFMS or the reactive power flowing through it needs to be regulated, the corresponding secondary control variable Δv sopR is enabled and designed as follows:

[0131] Δv sopR = c z δΔV C (13)

[0132] where, δ indicates whether the port of SOP acting as GFMS needs to participate in regulating the closing of the grid-connected switch. If it is needed, the value is 1, otherwise it is 0, and σ in formula (7) = 1 - η - μ - δ.

[0133] The sum of the secondary control variables designed for the regional interaction in different stages and the secondary control variables of the collaborative control of the resources within the region constitutes the total secondary control variables corresponding to different types of resources, that is:

[0134]

[0135] Among them, k pi and k ii respectively represent the proportional coefficient and integral coefficient of the PI link.

[0136] Figure 4 are the experimental results obtained by using the present invention; among them, as Figure 4 shown by (a) SSW closing in, in the time period of 0 - 4.5 s, each DRA successfully established its own voltage frequency, and the internal DG also successfully achieved power sharing. At the moment of 4.5 s, the SSW closing instruction was issued. In the time period of 4.5 - 7 s, each DG cooperatively adjusted the voltage amplitude and phase angle difference at both ends of the SSW. After the SSW met the seamless closing condition and operated at the moment of 7 s, the DRAs merged, and all the internal DGs achieved power sharing and successfully responded to the SSW closing instruction; as Figure 4 shown by (b) SSW opening in, in the time period of 0 - 4.5 s, each DRA also successfully established its own voltage frequency, and the internal DG also successfully achieved power sharing. At the moment of 4.5 s, the SSW opening instruction was issued. In the time period of 4.5 - 7 s, each DG cooperatively adjusted the active and reactive powers flowing through the SSW. After the SSW met the seamless opening condition and operated at the moment of 7 s, the DRAs separated, and the DGs inside each separated DRA achieved power sharing and successfully responded to the SSW opening instruction; as Figure 4 shown by (c) grid - connection switch closing in, after the distribution network resumed power supply in the time period of 0 - 4.5, the grid - connection switch closing instruction was issued at the moment of 4.5 s. In the time period of 4.5 - 10 s, all the DGs in the distribution network cooperatively adjusted the voltage amplitude and phase angle difference at both ends of the grid - connection switch, and the fluctuation of the DG output power is reflected in the figure.

[0137] As mentioned above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A multi - resource distributed collaborative control method for an elastic distribution network, characterized in that, Including: Step 1: Identify the post-disaster distributed restoration resources within different dynamic restoration areas (DRA) divided in the post-disaster distribution network; Differentially classify the heterogeneous DRAs according to the distributed restoration resources in the post-disaster distribution network within different DRAs. The heterogeneous DRAs after differential classification include network-constructing support type DRA, network-following supplement type DRA, network-constructing and following hybrid type DRA, and power outage areas; Step 2: Determine the primary control methods of different types of restoration resources under heterogeneous DRAs; among them, different types of restoration resources include grid-forming resources (GFMS), grid-following resources (GFLS), and intelligent soft switches (SOP); Step 3: Decompose the collaborative control objectives of different types of restoration resources within the heterogeneous DRA into voltage / frequency droop-free restoration and power sharing, and design the collaborative secondary control variables of different types of restoration resources within the DRA according to the collaborative control objectives; Step 4: Conduct cross-interval interaction for the heterogeneous DRA. The cross-interval interaction of the heterogeneous DRA includes the merging and splitting of the DRA; Adjust the state variables of the intelligent switch (SSW) during the cross-interval interaction of the heterogeneous DRA: The state variables adjusted by the intelligent switch SSW are used as the secondary control objectives, and design the SSW-adjusted secondary control variables of different types of restoration resources according to the state variables adjusted by the SSW; Step 5: Based on the designed collaborative secondary control variables of different types of restoration resources within the DRA and the SSW-adjusted secondary control variables of different types of restoration resources, after the distribution network resumes power supply, the restoration resources within the distribution network act together to adjust the synchronous operation of the distribution network and the large power grid. After the grid connection switch closes when meeting the preset conditions, the restoration resources within the distribution network will switch to the grid connection mode, and the distribution network resumes operation.

2. The elastic distribution network multi-resource distributed collaborative control method according to claim 1, wherein In Step 2, The GFMS autonomously supports the grid voltage and frequency, and the primary control uses droop control for networking; The GFLS operates in coordination with the GFMS. The GFLS uses inverse droop control to make the GFLS exhibit power droop characteristics; One end of the SOP adopts U dc The Q control maintains the stability of the DC capacitor voltage, and the other end of the SOP acts as the GFMS to participate in the load restoration; In Step 4, the implementation method of the merging and splitting of the DRA is: adjust the state of the intelligent switch SSW. When the voltage amplitude difference and phase angle difference at both ends of the SSW are close to 0, the SSW closes. When the active power and reactive power flowing through the SSW are close to 0, the SSW disconnects; The state variables adjusted by the SSW include the voltage amplitude difference and voltage phase angle difference at both ends of the SSW, as well as the active power and reactive power flowing through the SSW; After the DRA is merged or split, only the restoration resources within the DRA are collaboratively controlled.

3. A multi-resource distributed collaborative control method for an elastic distribution network according to claim 1, characterized in that The network-constructing support type DRA only includes GFMS. The network-constructing support type DRA can perform black start to restore loads and support the grid voltage and frequency; The network-following supplement type DRA only includes GFLS. The network-following supplement type DRA is interconnected with the DRA with GFMS through the SOP, thereby transmitting power to drive the start of the GFLS and collaboratively restoring the power outage loads; The network-constructing and following hybrid type DRA includes GFMS and GFLS. Among them, while the GFMS performs black start to restore loads, it drives the start of the GFLS within the region, and the two collaborate to restore the power outage loads; There is no distributed generation (DG) or only GFLS exists in the power outage area. The power outage area does not have the ability to black-start and restore loads, and the power outage area is regarded as an uncontrollable load. In the heterogeneous DRA partitions after differential classification, the grid-following supplementary DRA is connected to the grid-forming supporting DRA or the grid-forming and grid-following hybrid DRA through the SOP, and realizes dynamic soft scaling through continuous adjustment of the transmission power; the DRAs not interconnected through the SOP are connected through the SSW, and the 0-1 action of the SSW is used to realize dynamic hard scaling.

4. A multi-resource distributed cooperative control method for an elastic distribution network according to claim 3, characterized in that It is assumed that the communication links between DGs are connected and undirected, and can be connected and disconnected following the merger or separation of the heterogeneous DRA partitions after differential classification. The GFMS adopts primary droop control for networking, and additional distributed secondary control variables are added to the GFMS to realize the regulation of voltage frequency and active and reactive power; specifically as follows: Among them, Δu i and Δv i respectively represent the total secondary control variables of the active-frequency droop and reactive-voltage droop distributed controllers of the i-th GFMS. ω i is the operating frequency of the i-th DG, is the reference value of the operating frequency of the i-th DG, m i is the active-frequency droop coefficient of the i-th DG, P i is the active power output by the i-th DG, V i is the operating voltage of the i-th DG, V i ref is the reference value of the operating voltage of the i-th DG, n i is the reactive-voltage droop coefficient of the i-th DG, Q i is the reactive power output by the i-th DG.

5. A multi-resource distributed cooperative control method for an elastic distribution network according to claim 4, characterized in that The GFLS adopts primary inverted droop control to participate in cooperative operation, and additional distributed secondary control variables are added to the GFLS to realize the regulation of voltage frequency and active and reactive power; specifically as follows: Among them, Δp i and Δq i respectively represent the total secondary control variables of the active - frequency inverse droop and reactive - voltage inverse droop distributed controllers of the i - th GFLS. w i is the active - frequency inverse droop coefficient of the i - th DG, Q i is the reactive power output by the i - th DG, and h i is the reactive - voltage inverse droop coefficient of the i - th DG.

6. The elastic distribution network multi-resource distributed collaborative control method according to claim 5, characterized in that The other end of the SOP acts as the GFMS to participate in load restoration, specifically as follows: The port where the SOP acts as the GFMS adopts primary droop control for networking, and designs distributed secondary control variables to participate in cooperative operation. where, Δu sop and Δv sop respectively represent the total secondary control variables of the active-frequency droop and reactive-voltage droop distributed controllers when the SOP acts as the GFMS port. ω sop is the operating frequency when the SOP acts as the GFMS port, is the reference value of the operating frequency when the SOP acts as the GFMS port, m sop is the active-frequency droop coefficient when the SOP acts as the GFMS port, P sop is the output active power when the SOP acts as the GFMS port, V sop is the operating voltage when the SOP acts as the GFMS port, is the reference value of the operating voltage when the SOP acts as the GFMS port, n sop is the reactive-voltage droop coefficient when the SOP acts as the GFMS port, Q sop is the output reactive power when the SOP acts as the GFMS port.

7. A multi - resource distributed collaborative control method for an elastic distribution network according to claim 6, characterized in that, The goal of cooperative control of multiple types of restoration resources in the heterogeneous DRA is decomposed into voltage / frequency zero-error restoration and power sharing, specifically as follows: For the collaborative control of multiple types of resources in heterogeneous DRA, the GFMS secondary controller variables Δu S and Δv S are as follows: Among them, and Δω i and ΔV i respectively represent the deviations of the operating frequency and voltage from the reference values; a ij represents whether there is a communication link between the i-th DG and the j-th DG. If it exists, the value is 1; otherwise, it is 0; ΔP′ ij = P′ i - P′ j and ΔQ′ ij = Q′ i - Q′ j , ΔP′ ij , Q′ ij respectively represent the active and reactive power deviations per unit output by the i-th DG and the j-th DG; c f , c p , c v , c q respectively represent the gains corresponding to Δω i , ΔP′ ij , ΔV i , ΔQ′ ij ; α i represents whether voltage regulation is enabled. P′ i is the active power per unit output by the i-th DG, P′ j is the active power per unit output by the j-th DG, Q′ i is the reactive power per unit output by the i-th DG, Q′ j is the reactive power per unit output by the j-th DG; For the collaborative control of multiple types of resources in heterogeneous DRA, the GFLS secondary controller variables Δp S and Δq S are as follows: Among them, c fg 、c pg 、c vg 、c qg respectively represent the gains corresponding to Δω i 、ΔP ij 、ΔV i 、ΔQ ij ; E rate represents the rated capacity value of the inverter; ΔP ij = P i - P j and ΔQi j = Q i - Q j , ΔP ij 、ΔQ ij respectively represent the active and reactive power deviations of the i-th DG and the j-th DG outputs, P j is the active power output by the j-th DG, and Q j is the reactive power output by the j-th DG; For the collaborative control of multiple types of resources in a heterogeneous DRA, the SOP serves as the secondary control variables Δu sopS and Δv sopS which are designed as: Among them, and Δω sop , Δv sopS respectively represent the deviations of the operating frequency and voltage from the reference values; a sop，j indicates whether there is a communication link between the port where the SOP acts as the GFMS and the j-th DG in the network-connected supplementary DRA. If there is, the value is 1; otherwise, it is 0; ΔQ′ sop，j = Q′ sop - Q′ j , ΔQ′ sop，j represents the deviation of the unit reactive power output by the j-th DG in the network-connected supplementary DRA with the SOP acting as the GFMS port; σ indicates whether voltage regulation is enabled, Q′ sop is the unit reactive power output by the SOP acting as the GFMS port, and Q′ j is the unit reactive power output by the j-th DG.

8. A multi-resource distributed collaborative control method for an elastic distribution network according to claim 7, characterized in that When the voltage amplitude and phase angle difference at both ends of the SSW are close to 0, the SSW closes; when the active power and reactive power flowing through the SSW are close to 0, the SSW disconnects. The state variables adjusted by the SSW are used as the secondary control target, and the SSW adjustment secondary control variables of different types of restoration resources are designed according to the state variables adjusted by the SSW; specifically as follows: Adjust the state of SSW, and the secondary control variables Δu T and Δv T of GFMS are designed as follows: where, Δθ SSW，k and ΔV SSW，k represent the voltage phase and amplitude deviation at both ends of the k-th SSW respectively; AP′ SSW,k and ΔQ′ SSW,k represent the unit active and reactive power flowing through the k-th SSW respectively; β i and γ i represent whether the i-th DG participates in regulating the SSW state to meet the closing or opening conditions respectively. When the SSW changes from open to closed, β i = 1, γ i = 0. When the SSW changes from closed to open, β i = 0, γ i = 1. When the SSW does not operate, β i = 0, γ i = 0; c t 、c sp 、c o 、c sq represent the gains corresponding to Δθ SSW，k 、AP′ SSW,k 、ΔV SSW，k 、ΔQ′ SSW，k respectively; Adjust the state of SSW, and the secondary control variables Δp T and Δq T of GFLS are designed as follows: Among them, c tg , c spg , c og , c sqg respectively represent the gains corresponding to Δθ SSW，k , ΔP SSW，k , ΔV SSW，k , ΔQ SSW,k ; ΔP SSW，k and ΔQ SSW，k respectively represent the active and reactive powers flowing through the k-th SSW. Enable the SOP to act as a secondary control variable Δv for regulating the SSW state at the GFMS port only when the SOP acts as a port connection of the GFMS to regulate the amplitude at both ends of the SSW or the reactive power flow sopT , the design is as follows: Δv sopT = c o ηΔV SSW，k + c sq μΔQ′ SSW，k (9) Among them, η and μ respectively indicate whether the SOP acting as the port of the GFMS needs to participate in regulating the closing and opening of the SSW. If it is required, the value is 1; otherwise, it is 0; ΔQ′ SSW，k is the unit reactive power flowing through the k-th SSW.

9. The elastic distribution network multi-resource distributed collaborative control method according to claim 8, characterized in that The grid connection switch closes when it meets the preset conditions. The preset conditions refer to the synchronous operation of the distribution network and the upstream large power grid. The synchronous operation of the distribution network and the upstream large power grid means that the voltage amplitude difference and voltage phase angle difference at both ends of the grid connection switch are close to 0; specifically as follows: For the state regulation of the grid-connected switch, the secondary control variables Δu R and Δv R are designed as follows: where, Δθ C and ΔV C represent the voltage phase and amplitude deviation across the grid - connection switch respectively; λ i indicates whether the i - th DG needs to participate in adjusting the grid - connection switch state to meet the closing condition. When the grid - connection command is issued, λ i = 1, otherwise λ i = 0; c θ and c z represent the gains corresponding to Δθ C and ΔV C respectively; For the state regulation of the grid-connected switch, the secondary control variables Δp R and Δq R are designed as follows: Among them, C θg and c zg respectively represent the corresponding secondary controller variable gains; Enable SOP to act as the secondary control variable Δv for regulating the grid-connected switch status at the GFMS port only when the amplitude at both ends of the grid-connected switch connected to the port of the GFMS or the reactive power flowing through it is regulated sopR , and the design is as follows: Δv sopR = c z δΔV C (12) Among them, δ represents whether the port where the SOP acts as the GFMS needs to participate in regulating the closing of the grid connection switch. If it is needed, the value is 1, otherwise it is 0, and σ = 1 - η - μ - δ in formula (6).

10. A multi-resource distributed cooperative control method for an elastic distribution network according to claim 9, characterized in that where k pi and k ii represent the proportional coefficient and integral coefficient of the PI link, respectively.

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