SOP-based double-end AC / DC flexible interconnection power distribution system operation method and system

Abstract

The invention discloses an SOP-based double-end AC / DC flexible interconnection power distribution system operation method and system, and the method comprises the steps: obtaining the data of a power distribution system, and carrying out the large-signal stability analysis of the power distribution system. And according to the large signal average value model and the TS fuzzy model, constructing a control equation of the double-end AC / DC flexible interconnection power distribution system based on the SOP, and drawing an attraction domain of each working point. And planning a system running track according to the attraction domain of the target working point to ensure stable running of the system. According to the SOP-based double-end AC / DC flexible interconnection power distribution system operation method and system provided by the invention, the effectiveness of planning or guiding the operation of the source-load double-end AC / DC power distribution system based on the attraction domain is explained by the state trajectory of the SOP-based double-end AC / DC flexible interconnection power distribution system; the replacement cost of hardware equipment of a main circuit of the system is too high, and the problem of instability of large signals can be smoothly avoided on the premise that all parameters of an original system are not changed.

Description

Technical Field

[0001] The present invention relates to the technical field of safe and stable operation of flexible AC / DC power distribution networks, and specifically to an operation method and system of a two-terminal AC / DC flexible interconnected power distribution system based on SOP. Background Art

[0002] With the rapid development of power systems, the scale of power systems is constantly upgrading. The damage and economic losses caused by power outages are also increasing. Therefore, the stability of power systems is becoming more and more important. Due to the inherent nonlinear characteristics of power electronic converters in power systems, it is a difficult problem to ensure their safe and stable operation. Traditionally, the stability of power electronic converters is studied by small signal analysis tools. Small signal linearization is performed near the operating point to convert the nonlinear system into a small signal linear model. In many cases, using classical linear control theory and adopting safety margins, it is easy to design a voltage regulator to achieve stable operation and good overall system performance. However, the results obtained by this type of analysis method are only valid locally. However, the small signal analysis method is not suitable for large signal stability analysis. The advantage of the attraction domain is that this method can quantitatively and intuitively describe the size of the large disturbance that the system can withstand. The small signal theory analyzes the stability of the AC / DC interconnected distribution system based on flexible soft switching. The derived small signal stability range only demarcates the area where the operating point is stable, but cannot guarantee that the system can maintain stable operation when switching between these operating points. Therefore, according to the stable working range divided by small signal stability analysis, guiding the system operation may cause unstable accidents under large signal disturbance conditions, resulting in economic losses. In this regard, the present invention proposes a stable operation guide suitable for the SOP-based two-terminal AC / DC flexible interconnection distribution system that has been put into operation based on the attraction domain theory without changing the system hardware and software, thereby avoiding the risk of instability in the system during operation. Summary of the invention

[0003] In view of the above-mentioned problems, the present invention is proposed.

[0004] Therefore, the technical problem solved by the present invention is to effectively overcome the limitations of small signal stability analysis in the prior art. By introducing large signal stability analysis, the area of ​​stable operation of the system is redefined, thereby ensuring that the system can maintain stable operation even under large signal disturbances. By applying the attraction domain theory, the present invention can provide accurate dynamic stability guidance for system operation, avoid unstable accidents that may occur under large signal conditions, and thus ensure efficient and economical operation of the system.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: a method for operating a two-terminal AC / DC flexible interconnected distribution system based on SOP, comprising: acquiring distribution system data and performing large signal stability analysis on the distribution system.

[0006] According to the large signal average model and TS fuzzy model, the control equation of the two-terminal AC / DC flexible interconnected distribution system based on SOP is constructed, and the attraction domain of each working point is drawn.

[0007] The system operation trajectory is planned according to the attraction domain of the target working point to ensure stable operation of the system.

[0008] As a preferred scheme of the operation method of the two-terminal AC / DC flexible interconnected distribution system based on SOP described in the present invention, wherein: the TS fuzzy model includes, in the large signal stability analysis, estimating ROA based on the TS fuzzy model method, guiding the operation of the two-terminal AC / DC flexible interconnected distribution system based on SOP, establishing an operation guide for the two-terminal AC / DC flexible interconnected distribution system based on SOP, and maximally ensuring the stable operation of the system.

[0009] The TS fuzzy model has the problem of dimensional collapse for complex nonlinear systems, and the two-terminal AC / DC flexible interconnected distribution system based on SOP can only transmit active power on the DC side. Therefore, when the AC power grid is a strong power grid, the coupling relationship between the dq components of the system is ignored, and only the d-axis component of the system is considered.

[0010] As a preferred solution of the operation method of the two-terminal AC / DC flexible interconnection distribution system based on SOP described in the present invention, wherein: the large signal average value model includes a large signal average value model of the two-terminal AC / DC flexible interconnection distribution system based on SOP obtained by a simplified processing method using a switching cycle average method, and the state variables of the system include x=[i dr ,v gdr ,i dcc ,v dci ,i di ,m1,m2,m3,m4,v gdi ].

[0011] The large signal average model is expressed as:

[0012]

[0013] The subscript d represents the component of the d-axis in the dq coordinate system obtained after the dq transformation. dr represents the d-axis current of the main converter in the synchronous rotating coordinate system, v gdr The d-axis grid voltage of the main converter in the synchronous rotating coordinate system, v dcr represents the DC side voltage of the main converter in the synchronous rotating coordinate system, sdr represents the d-axis duty cycle of the main converter in the synchronous rotating coordinate system. di represents the d-axis current of the inverter in the synchronous rotating coordinate system, v gdi represents the d-axis grid voltage of the slave converter in the synchronous rotating coordinate system, v dci represents the DC voltage of the slave converter in the synchronous rotating coordinate system, s di represents the d-axis duty cycle of the slave converter in the synchronous rotating coordinate system. dcc Indicates the DC line current. i drref Represents the current command generated by the voltage outer loop PI controller, V dcrref Indicates the reference value of the DC voltage output by the main converter. diref represents the current command generated by the voltage outer loop PI controller, P iref Indicates the active power command value of the slave converter, P i Indicates the active power value of the slave converter. gdi Indicates the load d-axis voltage. m i (i=12,3,4) represents the intermediate parameter of PI controller, which is obtained by integrating the corresponding parameter deviation. r Represents the main converter inductance, R sr Represents equivalent resistance, C dcr Represents capacitance. R sc Indicates the equivalent resistance of the DC line, L c Indicates the inductance of the DC line. L i Represents the inductance from the converter side, R si Indicates the equivalent resistance of the inverter, C dci represents capacitance. ω=2πf represents the angular frequency of the AC power grid.

[0014] As a preferred solution of the operation method of the double-terminal AC / DC flexible interconnected distribution system based on SOP described in the present invention, the control equation includes: the main converter adopts a voltage and current dual-loop control structure to ensure the stability of the DC bus voltage and the stable operation of the system, and the slave converter adopts a power outer loop + current inner loop control structure to quantitatively control the power flow. The control equation is expressed as:

[0015]

[0016] Among them, k ipdr represents the proportional coefficient of the main converter current inner loop PI controller, k iidr Indicates the integral coefficient of the main converter current inner loop PI controller. k vpdr represents the proportional coefficient of the main converter voltage outer loop PI controller, k vidr Represents the integral coefficient of the main converter voltage outer loop PI controller. k ipdirepresents the proportional coefficient of the inner loop PI controller of the converter current, k iidi k represents the integral coefficient of the inner loop PI controller of the slave converter current. vpdi represents the proportional coefficient of the PI controller of the power outer loop of the converter, k vidri Represents the integral coefficient of the PI controller of the power outer loop of the slave converter. V tri Indicates the carrier voltage amplitude.

[0017] As a preferred solution of the operation method of the two-terminal AC / DC flexible interconnection distribution system based on SOP described in the present invention, the TS fuzzy model includes: for the establishment of the TS fuzzy model, the large signal stability of the system is analyzed by moving the working point to the origin. The new state variable is expressed as:

[0018]

[0019] Among them, V dcr represents the steady-state value of the corresponding variable, I dr represents the steady-state value of the corresponding variable, I qr represents the steady-state value of the corresponding variable.

[0020] As a preferred solution of the operation method of the two-terminal AC / DC flexible interconnection distribution system based on SOP described in the present invention, wherein: the drawing of the attraction domain of each working point includes performing coordinate transformation according to the new state variable, placing the steady-state working point of the system at the origin of the coordinate system, and the obtained result is written in matrix form, which is expressed as:

[0021]

[0022] in,

[0023]

[0024]

[0025] There are 4 nonlinear terms, so 24 fuzzy rules are constructed. According to the constant coefficient matrix A of the local linear submodel of the TS fuzzy model i , directly applied to the LMI formula, the LMI formula is expressed as:

[0026]

[0027] Find the constant positive definite matrix M and Lyapunov function under the extreme value, and draw the attraction domain of the system at the equilibrium point.

[0028] Substitute the data of a certain working point and obtain the corresponding M matrix by the LMI formula. Draw the attraction domain at the corresponding working point based on the obtained matrix M.

[0029] As a preferred solution of the operation method of the two-terminal AC / DC flexible interconnection distribution system based on SOP described in the present invention, the planned system operation trajectory includes: when the system has a high-power load connected from the converter side, the system has two operating points at this time. When it is clear that the load is xMW, the steady-state operating point of the system is used as the initial point OP1 of the large signal disturbance process. When the load is yMW, the corresponding steady-state operating point of the system is used as the final target operating point OP2, and these two operating points are both small-signal stable.

[0030] Estimate the attraction domain of the final target working point OP2 and determine whether the initial point OP1 is within the attraction domain of the target working point OP2: If the attraction domain of OP2 contains the initial point OP1, the system must be able to start from OP1, go through a short transient process, and finally stably work at OP2.

[0031] Estimate and draw the attraction domain Ω of the operating point OP2 OP2 , judge Ω OP2 Whether OP1 is included or not, there are two types of positional relationships:

[0032] When Ω OP2 When OP1 is included, the system can run directly from OP1 to OP2, and the system will not become unstable.

[0033] When Ω OP2 If OP1 is not included, it is necessary to OP2 Find an intermediate transitional transient operating point OP3 inside. Take the middle point between OP1 and OP2, define it as OP3, and re-determine whether OP3 is in Ω OP2 interior.

[0034] If OP3 is in Ω OP2 The interior of OP3 is estimated by OP3 , and determine OP1 and Ω OP3 position relationship.

[0035] If OP1 is in Ω OP3 Inside, the operating point trajectory of the two-terminal AC / DC flexible interconnected distribution system based on SOP is OP1→OP3→OP2.

[0036] If OP1 is in Ω OP3 If the outside of OP1 is selected, the middle point OP4 between OP1 and OP3 is selected, and so on, until the attraction domain Ω of OPn is obtained. OPn At this point, the operating point trajectory of the two-terminal AC / DC flexible interconnected distribution system based on SOP is OP1→OPn→…→OP3→OP2.

[0037] A two-terminal AC / DC flexible interconnection distribution system operation system based on SOP, characterized in that: it includes:

[0038] The stability analysis module obtains distribution system data and performs large signal stability analysis on the distribution system.

[0039] Draw the attraction domain module, construct the control equation of the two-terminal AC / DC flexible interconnected distribution system based on SOP according to the large signal average model and TS fuzzy model, and draw the attraction domain of each working point.

[0040] The trajectory planning module plans the system operation trajectory according to the attraction domain of the target working point to ensure the stable operation of the system.

[0041] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0042] A computer-readable storage medium stores a computer program, which implements the steps of the method described above when executed by a processor.

[0043] Beneficial effects of the present invention: The time domain simulation and system state trajectory of the present invention both illustrate the effectiveness of planning or guiding the operation of a source-load two-terminal AC / DC distribution system based on an attraction domain. For a two-terminal AC / DC flexible interconnected distribution system based on SOP that has been put into operation, the replacement cost of the hardware equipment of the system's main circuit is too high. Without changing the parameters of the original system, the occurrence of large signal instability problems can be successfully avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0045] Figure 1 An overall flow chart of a method for operating a two-terminal AC / DC flexible interconnected power distribution system based on SOP provided in the first embodiment of the present invention;

[0046] Figure 2 A simplified average value model diagram of a two-terminal AC / DC flexible interconnection distribution system based on SOP, which is a two-terminal AC / DC flexible interconnection distribution system operation method based on SOP provided by the first embodiment of the present invention;

[0047] Figure 3A flow chart of a system stable operation guide based on an attraction domain for a method for operating a two-terminal AC / DC flexible interconnected power distribution system based on SOP provided in the first embodiment of the present invention;

[0048] Figure 4 A planning method for operating a two-terminal AC / DC flexible interconnected power distribution system based on SOP is provided for the first embodiment of the present invention; a schematic diagram of an operating trajectory of a two-terminal AC / DC flexible interconnected power distribution system based on SOP;

[0049] Figure 5 The second embodiment of the present invention provides a method for operating a two-terminal AC / DC flexible interconnected power distribution system based on SOP to estimate the attraction domain of the target operating point OP2 and its positional relationship with OP1;

[0050] Figure 6 A method for operating a two-terminal AC / DC flexible interconnected power distribution system based on SOP and a diagram of its attraction domain for finding a transition operating point OP3 is provided in accordance with the second embodiment of the present invention;

[0051] Figure 7 A system state trajectory diagram under the transformation of working point OP1→OP3→OP2 of a two-terminal AC / DC flexible interconnected distribution system operation method based on SOP provided in the second embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0053] Example 1

[0054] Reference Figure 1 to Figure 4 , is an embodiment of the present invention, and provides a method for operating a two-terminal AC / DC flexible interconnection distribution system based on SOP, comprising:

[0055] S1: Obtain distribution system data and perform large signal stability analysis on the distribution system.

[0056] It should be noted that the two-terminal AC / DC flexible interconnection distribution system based on SOP includes a main converter, a slave converter and a DC bus. For the stability analysis of the AC / DC interconnection distribution system based on flexible soft switches, small signal stability analysis is generally used, but the small signal stability range obtained by the small signal stability analysis only delineates the area where the working point is stable, and cannot guarantee that the system can maintain stable operation when switching between these working points. According to the stable working range divided by the small signal stability analysis, the system operation is guided, and unstable accidents may occur under large signal disturbance conditions, causing economic losses. Therefore, it is necessary to adopt a large signal stability analysis method to redefine the area where the system can operate stably and ensure the system can operate stably to the greatest extent. Especially for the two-terminal AC / DC flexible interconnection distribution system based on SOP that has been put into operation, the system hardware equipment is fixed and the replacement cost is huge. There is a risk of failure in optimizing the controller parameters to meet the switching stability between working points. For a two-terminal AC / DC flexible interconnected power distribution system based on SOP, when a huge jump occurs in the system power, the present invention proposes a stable operation guide suitable for the system according to the attraction domain theory without changing the system hardware and software, thereby avoiding the risk of instability in the system during operation.

[0057] Furthermore, before performing large signal analysis, the system needs to satisfy global small signal stability within the working range. The research on small signal stability analysis of AC / DC hybrid distribution networks is relatively mature. The present invention performs large signal stability analysis under the premise of global small signal stability within the working range of the system.

[0058] S2: According to the large signal average model and TS fuzzy model, the control equation of the two-terminal AC / DC flexible interconnected distribution system based on SOP is constructed, and the attraction domain of each working point is drawn.

[0059] It should be noted that in large signal stability analysis, "domain" is usually used to describe the system's ability to withstand large disturbances, which is called the region of attraction (ROA). The calculation of the true region of attraction is very difficult and complicated, so the true subset of the region of attraction, that is, the estimated region of attraction (EROA), is usually calculated to replace the true region of attraction. There are many methods for estimating ROA, such as the Lyapunov method based on LaSalle's theorem, the Takagi-Sugeno (TS) fuzzy model method, the mixed potential function method, the genetic algorithm, etc. For different nonlinear systems, various methods have their own advantages. The present invention estimates ROA based on the TS fuzzy model method, guides the operation of a two-terminal AC / DC flexible interconnected distribution system based on SOP, and establishes an operation guide for a two-terminal AC / DC flexible interconnected distribution system based on SOP, so as to maximize the stable operation of the system.

[0060] The TS fuzzy model includes estimating ROA based on the TS fuzzy model method in large signal stability analysis, guiding the operation of the two-terminal AC / DC flexible interconnected distribution system based on SOP, and establishing an operation guide for the two-terminal AC / DC flexible interconnected distribution system based on SOP to ensure the stable operation of the system to the greatest extent.

[0061] Considering the possible dimension collapse problem of TS fuzzy model for complex nonlinear systems, in addition, the two-terminal AC / DC flexible interconnection distribution system based on SOP can only transmit active power on the DC side. Therefore, when the AC power grid is a strong power grid, such as SCR>4, the coupling relationship between the dq components of the system can be ignored, so that only the d-axis component of the system can be considered. The large signal average model of the two-terminal AC / DC flexible interconnection distribution system based on SOP can be obtained by using the switching cycle averaging method. Figure 2 shown.

[0062] The large signal average model includes a large signal average model of a two-terminal AC / DC flexible interconnected power distribution system based on SOP obtained by simplifying the switching cycle average method. The state variables of the system include x = [i dr ,v gdr ,i dcc ,v dci ,i di ,m1,m2,m3,m4,v gdi ].

[0063] The large signal average model is expressed as:

[0064]

[0065] The subscript d represents the component of the d-axis in the dq coordinate system obtained after the dq transformation. dr represents the d-axis current of the main converter in the synchronous rotating coordinate system, v gdr The d-axis grid voltage of the main converter in the synchronous rotating coordinate system, v dcr represents the DC side voltage of the main converter in the synchronous rotating coordinate system, s dr represents the d-axis duty cycle of the main converter in the synchronous rotating coordinate system. di represents the d-axis current of the inverter in the synchronous rotating coordinate system, v gdi represents the d-axis grid voltage of the slave converter in the synchronous rotating coordinate system, v dci represents the DC voltage of the slave converter in the synchronous rotating coordinate system, s di represents the d-axis duty cycle of the slave converter in the synchronous rotating coordinate system. dcc Indicates the DC line current. i drref Represents the current command generated by the voltage outer loop PI controller, V dcrrefIndicates the reference value of the DC voltage output by the main converter. diref represents the current command generated by the voltage outer loop PI controller, P iref Indicates the active power command value of the slave converter, P i Indicates the active power value of the slave converter. gdi Indicates the load d-axis voltage. m i (i=12,3,4) represents the intermediate parameter of PI controller, which is obtained by integrating the corresponding parameter deviation. r Represents the main converter inductance, R sr Represents equivalent resistance, C dcr Represents capacitance. R sc Indicates the equivalent resistance of the DC line, L c Indicates the inductance of the DC line. L i Represents the inductance from the converter side, R si Indicates the equivalent resistance of the inverter, C dci represents capacitance. ω=2πf represents the angular frequency of the AC power grid.

[0066] The main converter adopts a voltage-current dual-loop control structure to ensure the stability of the DC bus voltage and the stable operation of the system. The slave converter adopts a power outer loop + current inner loop control structure to quantitatively control the power flow. The control equation is expressed as:

[0067]

[0068] Among them, k ipdr represents the proportional coefficient of the main converter current inner loop PI controller, k iidr Indicates the integral coefficient of the main converter current inner loop PI controller. k vpdr represents the proportional coefficient of the main converter voltage outer loop PI controller, k vidr Represents the integral coefficient of the main converter voltage outer loop PI controller. k ipdi represents the proportional coefficient of the inner loop PI controller of the converter current, k iidi k represents the integral coefficient of the inner loop PI controller of the slave converter current. vpdi represents the proportional coefficient of the PI controller of the power outer loop of the converter, k vidri Represents the integral coefficient of the PI controller of the power outer loop of the slave converter. V tri Indicates the carrier voltage amplitude.

[0069] In order to establish the TS fuzzy model, the large signal stability of the system is analyzed by moving the operating point to the origin. The new state variable is expressed as:

[0070]

[0071] Among them, V dcrrepresents the steady-state value of the corresponding variable, I dr represents the steady-state value of the corresponding variable, I qr represents the steady-state value of the corresponding variable.

[0072] According to the new state variables, coordinate transformation is performed and the steady-state operating point of the system is placed at the origin of the coordinate system. The result is written in matrix form and expressed as:

[0073]

[0074] in,

[0075]

[0076]

[0077] There are 4 nonlinear terms, so 24 fuzzy rules are constructed. According to the constant coefficient matrix A of the local linear submodel of the TS fuzzy model i , directly applied to the LMI formula, the LMI formula is expressed as:

[0078]

[0079] Find the constant positive definite matrix M and Lyapunov function under the extreme value, and draw the attraction domain of the system at the equilibrium point.

[0080] Substitute the data of a certain working point and obtain the corresponding M matrix by the LMI formula. Draw the attraction domain at the corresponding working point based on the obtained matrix M.

[0081] S3: Plan the system operation trajectory according to the attraction domain of the target working point to ensure stable operation of the system.

[0082] It should be noted that in the two-terminal AC / DC flexible interconnection distribution system based on SOP, the main converter adopts DC voltage outer loop control to support the DC side voltage. The slave converter adopts power outer loop + current inner loop control to ensure power controllability. It can be seen that in the control structure of the two-terminal AC / DC flexible interconnection distribution system based on SOP, the slave converter controls the size of the system's transmitted active power, and the size of the system's control power instruction value is completely determined by the load demand. In actual operation, high-power loads are often connected and removed. How to ensure that the system can maintain stable operation under the conditions of high-power load connection and removal without cutting the load? Guiding the system operation based on the attraction domain theory can just avoid this instability. The specific operations are as follows:

[0083] When a high-power load is connected to the system from the converter side, the system has two operating points. When the load is xMW, the steady-state operating point of the system is used as the initial point OP1 of the large signal disturbance process. When the load is yMW, the corresponding steady-state operating point of the system is used as the final target operating point OP2, and both operating points are small-signal stable.

[0084] Estimate the attraction domain of the final target working point OP2 and determine whether the initial point OP1 is within the attraction domain of the target working point OP2: If the attraction domain of OP2 contains the initial point OP1, the system must be able to start from OP1, go through a short transient process, and finally stably work at OP2.

[0085] Furthermore, the following will introduce in detail the operation guide based on the attraction domain, such as Figure 3 shown.

[0086] Estimate and draw the attraction domain Ω of the operating point OP2 OP2 , judge Ω OP2 Whether OP1 is included or not, there are two types of positional relationships:

[0087] When Ω OP2 When OP1 is included, the system can run directly from OP1 to OP2, and the system will not become unstable.

[0088] When Ω OP2 If OP1 is not included, it is necessary to OP2 Find an intermediate transitional transient operating point OP3 inside. Take the middle point between OP1 and OP2, define it as OP3, and re-determine whether OP3 is in Ω OP2 interior.

[0089] If OP3 is in Ω OP2 The interior of OP3 is estimated by OP3 , and determine OP1 and Ω OP3 position relationship.

[0090] If OP1 is in Ω OP3 , then the operating point trajectory of the two-terminal AC / DC flexible interconnected distribution system based on SOP is OP1→OP3→OP2, as shown in Figure 4 shown.

[0091] If OP1 is in Ω OP3 If the outside of OP1 is selected, the middle point OP4 between OP1 and OP3 is selected, and so on, until the attraction domain Ω of OPn is obtained. OPn At this point, the operating point trajectory of the two-terminal AC / DC flexible interconnected distribution system based on SOP is OP1→OPn→…→OP3→OP2.

[0092] The above embodiments also include a two-terminal AC / DC flexible interconnection distribution system operation system based on SOP, specifically:

[0093] The stability analysis module obtains distribution system data and performs large signal stability analysis on the distribution system.

[0094] Draw the attraction domain module, construct the control equation of the two-terminal AC / DC flexible interconnected distribution system based on SOP according to the large signal average model and TS fuzzy model, and draw the attraction domain of each working point.

[0095] The trajectory planning module plans the system operation trajectory according to the attraction domain of the target working point to ensure the stable operation of the system.

[0096] The computer device may be a server. The computer device includes a processor, a memory, an input / output interface (I / O for short) and a communication interface. The processor, the memory and the input / output interface are connected via a system bus, and the communication interface is connected to the system bus via the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store data cluster data of a power monitoring system. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal via a network connection. When the computer program is executed by the processor, a method is implemented.

[0097] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but are not limited to this.

[0098] Example 2

[0099] Reference Figure 5 to Figure 7 , which is an embodiment of the present invention, provides a two-terminal AC / DC flexible interconnected distribution system operation method and system based on SOP. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through simulation experiments.

[0100] System operating conditions: Assume that, based on the SOP-based two-terminal AC / DC flexible interconnection distribution system, the load initially requires the system to deliver xMW of power, and the power system operates stably under this operating condition, which is recorded as the operating point OP1. When the load needs to increase the power of the load by (yx)MW, the yMW operating point is the final operating point, recorded as OP2. At this time, the load requires the SOP-based two-terminal AC / DC flexible interconnection distribution system to deliver yMW of active power.

[0101] First, it is necessary to determine whether the two-terminal AC / DC flexible interconnected distribution system based on SOP can operate stably when the transmission power is directly increased from xMW to yMW. First, it is necessary to draw the attraction domain Ω of the OP2 working point OP2 , the attraction domains estimated by different large signal analysis methods have different dimensions, but they can all be projected to i dr -v dcr On a plane, such as Figure 5 As shown. Among them, i dr is the active current component of the main converter, and its amplitude can indirectly reflect the active power transmitted by the system; while v dcr It is the output voltage of the DC side of the main converter, which can reflect whether the operation of the DC side of the system is stable. It can be seen that the position of OP1 is in the attraction domain Ω OP2 Therefore, if the system switches directly from OP1 to OP2, the large signal is likely to be unstable, and an intermediate transition point OP3 needs to be found. Figure 3 Find the middle transition point in this way.

[0102] Directly take the middle point between OP1 and OP2 as OP3 And estimate the attraction domain Ω of the working point OP3 ,like Figure 6 As shown, it can be seen that the working point OP3 is in the attraction domain Ω OP2 The system can safely transfer from the working point OP3 to the working point OP2. On the other hand, the position of OP1 in the state space is in the attraction domain Ω. OP3 The internal structure of the system ensures that the system can stably operate from the working point OP1 to OP3. Therefore, it can be determined that the operation of the system to complete the transfer of the working point from OP1 to OP3 is: OP1→OP3→OP2. In specific implementation, the load to be put into operation is put into operation twice, and the first operation Second re-commissioning

[0103] It can be seen that at t = 0.1s, the load power increases At t = 0.4s, it increases After two short transitions, the system finally stabilized and operated at yMW, meeting the user's power requirements. Figure 6 In the state space shown in Figure 7 It can be seen that in the whole process, the state trajectory of the system is in a positional relationship with the working point and its attraction domain determined by theoretical analysis. That is, the state trajectory of the system moves from OP1 to OP2, and the trajectory shows a convergence trend. After a transition process, it reaches OP2. This is the first increase in load power. Then, the load power increases again. The system operating point moves from OP2 to OP3, and the state trajectory also shows a convergence trend, and finally stabilizes at OP3.

[0104] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for operating a two-terminal AC / DC flexible interconnection distribution system based on SOP, characterized in that: include: Obtain distribution system data and conduct large signal stability analysis on the distribution system; According to the large signal average model and TS fuzzy model, the control equation of the two-terminal AC / DC flexible interconnected distribution system based on SOP is constructed, and the attraction domain of each working point is drawn; The system operation trajectory is planned according to the attraction domain of the target working point to ensure stable operation of the system.

2. The method for operating a two-terminal AC / DC flexible interconnection power distribution system based on SOP according to claim 1, characterized in that: The TS fuzzy model includes estimating ROA based on the TS fuzzy model method in large signal stability analysis, guiding the operation of the two-terminal AC / DC flexible interconnected distribution system based on SOP, establishing an operation guide for the two-terminal AC / DC flexible interconnected distribution system based on SOP, and ensuring the stable operation of the system to the maximum extent; The TS fuzzy model has the problem of dimensional collapse for complex nonlinear systems, and the two-terminal AC / DC flexible interconnected distribution system based on SOP can only transmit active power on the DC side. Therefore, when the AC power grid is a strong power grid, the coupling relationship between the dq components of the system is ignored, and only the d-axis component of the system is considered.

3. The method for operating a two-terminal AC / DC flexible interconnection distribution system based on SOP according to claim 2, characterized in that: The large signal average model includes a large signal average model of a two-terminal AC / DC flexible interconnected power distribution system based on SOP obtained by simplified processing using a switching cycle average method. The state variables of the system include x=[i dr ,v gdr ,i dcc ,v dci ,i di ,m1,m2,m3,m4,v gdi ]; The large signal average model is expressed as: Wherein, the subscript d represents the component of the d-axis in the dq coordinate system obtained after the dq transformation; i dr represents the d-axis current of the main converter in the synchronous rotating coordinate system, v gdr The d-axis grid voltage of the main converter in the synchronous rotating coordinate system, v dcr represents the DC side voltage of the main converter in the synchronous rotating coordinate system, s dr represents the d-axis duty cycle of the main converter in the synchronous rotating coordinate system; i di represents the d-axis current of the inverter in the synchronous rotating coordinate system, v gdi represents the d-axis grid voltage of the slave converter in the synchronous rotating coordinate system, v dci represents the DC voltage of the slave converter in the synchronous rotating coordinate system, s di represents the d-axis duty cycle of the slave converter in the synchronous rotating coordinate system; i dcc Represents the DC line current; i drref Represents the current command generated by the voltage outer loop PI controller, V dcrref Indicates the reference value of the DC voltage output by the main converter; i diref represents the current command generated by the voltage outer loop PI controller, P iref Indicates the active power command value of the slave converter, P i Indicates the active power value of the slave converter; v gdi Indicates the load d-axis voltage; m i (i=12,3,4) represents the intermediate parameter of PI controller, which is obtained by integrating the corresponding parameter deviation; L r Represents the main converter inductance, R sr Represents equivalent resistance, C dcr Represents capacitance; R sc Indicates the equivalent resistance of the DC line, L c Indicates the inductance of the DC line; L i Represents the inductance from the converter side, R si Indicates the equivalent resistance of the inverter, C dci represents capacitance; ω=2πf represents the angular frequency of the AC power grid.

4. The method for operating a two-terminal AC / DC flexible interconnection power distribution system based on SOP according to claim 3, characterized in that: The control equation includes that the main converter adopts a voltage and current dual-loop control structure to ensure the stability of the DC bus voltage and the stable operation of the system, and the slave converter adopts a power outer loop + current inner loop control structure to quantitatively control the power flow. The control equation is expressed as: Among them, k ipdr represents the proportional coefficient of the main converter current inner loop PI controller, k iidr represents the integral coefficient of the main converter current inner loop PI controller; k vpdr represents the proportional coefficient of the main converter voltage outer loop PI controller, k vidr k represents the integral coefficient of the main converter voltage outer loop PI controller; ipdi represents the proportional coefficient of the inner loop PI controller of the converter current, k iidi represents the integral coefficient of the inner loop PI controller of the slave converter current; k vpdi represents the proportional coefficient of the PI controller of the power outer loop of the converter, k vidri Represents the integral coefficient of the PI controller of the power outer loop of the slave converter; V tri Indicates the carrier voltage amplitude.

5. The method for operating a two-terminal AC / DC flexible interconnection distribution system based on SOP according to claim 4, characterized in that: The TS fuzzy model includes: for the establishment of the TS fuzzy model, the large signal stability of the system is analyzed by moving the working point to the origin; the new state variable is expressed as: Among them, V dcr represents the steady-state value of the corresponding variable, I dr represents the steady-state value of the corresponding variable, I qr represents the steady-state value of the corresponding variable.

6. The method for operating a two-terminal AC / DC flexible interconnection power distribution system based on SOP according to claim 5, characterized in that: The drawing of the attraction domain of each working point includes performing coordinate transformation according to the new state variables, placing the steady-state working point of the system at the origin of the coordinate system, and writing the obtained result in matrix form, which is expressed as: in, There are 4 nonlinear terms, so 24 fuzzy rules are constructed; according to the constant coefficient matrix A of the local linear submodel of the TS fuzzy model i , directly applied to the LMI formula, the LMI formula is expressed as: Find the constant positive definite matrix M and Lyapunov function under the extreme value, and draw the attraction domain of the system at the equilibrium point; Substitute the data of a certain working point and obtain the corresponding M matrix by the LMI formula. Draw the attraction domain at the corresponding working point based on the obtained matrix M.

7. The method for operating a two-terminal AC / DC flexible interconnection distribution system based on SOP according to claim 6, characterized in that: The planned system operation trajectory includes that when a high-power load is connected to the system from the converter side, the system has two operating points. When it is clear that the load is xMW, the steady-state operating point of the system is used as the initial point OP1 of the large-signal disturbance process; when the load is yMW, the corresponding steady-state operating point of the system is used as the final target operating point OP2, and both operating points are small-signal stable. Estimate the attraction domain of the final target working point OP2, and determine whether the initial point OP1 is within the attraction domain of the target working point OP2: If the attraction domain of OP2 contains the initial point OP1, the system must be able to start from OP1, go through a short transient process, and finally work stably at OP2; Estimate and draw the attraction domain Ω of the operating point OP2 OP2 , judge Ω OP2 Whether OP1 is included or not, there are two types of positional relationships: When Ω OP2 When OP1 is included, the system can run directly from OP1 to OP2, and the system will not be unstable; When Ω OP2 If OP1 is not included, it is necessary to OP2 Find an intermediate transitional transient operating point OP3 inside; take the middle point between OP1 and OP2, defined as OP3, and re-determine whether OP3 is in Ω OP2 the interior; If OP3 is in Ω OP2 , then estimate the attraction domain Ω of OP3 OP3 , and determine OP1 and Ω OP3 Positional relationship; If OP1 is in Ω OP3 Inside, the operating point trajectory of the two-terminal AC / DC flexible interconnected distribution system based on SOP is OP1→OP3→OP2; If OP1 is in Ω OP3 If the outside of OP1 is selected, the middle point OP4 between OP1 and OP3 is selected, and so on, until the attraction domain Ω of OPn is obtained. OPn Up to including OP1; at this time, the operating point trajectory of the two-terminal AC / DC flexible interconnected distribution system based on SOP is OP1→OPn→…→OP3→OP2.

8. A two-terminal AC / DC flexible interconnection distribution system operation system based on SOP using the method according to any one of claims 1 to 7, characterized in that: Stability analysis module, which obtains distribution system data and performs large signal stability analysis on the distribution system; Draw the attraction domain module, construct the control equation of the two-terminal AC / DC flexible interconnected distribution system based on SOP according to the large signal average model and TS fuzzy model, and draw the attraction domain of each working point; The trajectory planning module plans the system operation trajectory according to the attraction domain of the target working point to ensure the stable operation of the system.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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