阅读说明：本技术 一种lcc-vsc混合直流电网机电暂态仿真方法、装置及存储介质 (Electromechanical transient simulation method and device for LCC-VSC hybrid direct-current power grid and storage medium ) 是由 张金龙 鲍颜红 徐泰山 徐伟 查显煜 罗峰 杨君军 郭剑 吴峰 任先成 阮晶晶 于 2021-07-16 设计创作，主要内容包括：本发明公开了一种LCC-VSC混合直流电网机电暂态仿真方法、装置及存储介质,所述方法包括：根据混合直流电网动态元件特性和网络拓扑构建混合直流电网动态模型；根据预设的仿真步长构建与混合直流电网动态模型相对应的差分方程组；根据差分方程组混合直流电网状态变量的偏导项,构建雅可比矩阵；采用牛顿拉夫逊法对当前仿真时刻差分方程组进行迭代求解,迭代过程中不断更新差分方程组及雅可比矩阵中的变量元素,直至收敛；根据当前仿真时刻差分方程组求解结果,获取下一仿真时刻混合直流电网的状态变量。本发明能够从整体上提升LCC-VSC混合直流电网机电暂态仿真的计算精度和计算效率,满足工程应用要求。(The invention discloses an LCC-VSC hybrid direct current power grid electromechanical transient simulation method, a device and a storage medium, wherein the method comprises the following steps: constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology; constructing a difference equation set corresponding to the hybrid direct-current power grid dynamic model according to a preset simulation step length; constructing a Jacobian matrix according to the partial derivative terms of the state variables of the mixed direct current network of the differential equation set; performing iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence; and obtaining the state variable of the hybrid direct-current power grid at the next simulation time according to the solving result of the differential equation set at the current simulation time. The method can improve the calculation precision and the calculation efficiency of the electromechanical transient simulation of the LCC-VSC hybrid direct current power grid on the whole, and meet the engineering application requirements.)

1. An LCC-VSC hybrid direct current grid electromechanical transient simulation method is characterized by comprising the following steps:

constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;

constructing a difference equation set corresponding to the hybrid direct-current power grid dynamic model according to a preset simulation step length;

constructing a Jacobian matrix according to the partial derivative terms of the state variables of the mixed direct current network of the differential equation set;

performing iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;

and obtaining the state variable of the hybrid direct-current power grid at the next simulation time according to the solving result of the differential equation set at the current simulation time.

2. The LCC-VSC hybrid direct current grid electromechanical transient simulation method of claim 1, wherein a circuit equivalent transformation is performed on the hybrid direct current grid before the hybrid direct current grid dynamic model is constructed.

3. The LCC-VSC hybrid direct current grid electromechanical transient simulation method according to claim 1 or 2, characterized in that the hybrid direct current grid dynamic models comprise a direct current line dynamic model, an LCC converter direct current side dynamic model and a VSC converter direct current side dynamic model.

4. The LCC-VSC hybrid direct current grid electromechanical transient simulation method of claim 3, wherein the direct current line dynamic model is described with equation (1):

wherein R is_i,j、L_i,j、I_i,jThe equivalent resistance and the equivalent inductance of the direct current line and the current flowing through the direct current line are respectively; t represents time; v_i、V_jThe direct current voltages of nodes i and j at two ends of a direct current line are respectively direct current voltages; the positive direction of the direct current line current flows from i to j, wherein i is less than j;

the direct current side dynamic model of the LCC converter is described by equations (2) to (4):

wherein, U_iThe voltage is the direct current side voltage of the LCC converter; l is_iIs a smoothing reactor; x_iIs the LCC converter equivalent impedance; i is_iInjecting the current of the direct current line into the LCC converter; c_i、I_c,iNode i is equivalent to earth capacitance and current flowing through the node i; s_iThe direct current lines connected with the node i are collected;g_i、h_iare respectively S_iCurrent, head end node, tail end node, g, of medium DC line_i＜h_i；Is an orientation factor, if i ═ g_iThenOtherwise

The VSC converter direct current side dynamic model is described by equations (5) to (7):

V_jI_j＝P_j (5)

wherein: c_j、I_c,jRespectively node j equivalent earth capacitance and current flowing through the node j equivalent earth capacitance; i is_jInjecting the current of the direct current line into the VSC converter; s_jIs a direct current line set connected with the node j;g_j、h_jare respectively S_jCurrent, head end node, tail end node, g, of medium DC line_j＜h_j；Is a direction factor, if j is g_jThen, thenOtherwiseP_jAnd injecting the power of the direct current line for the VSC converter.

5. The LCC-VSC hybrid direct current grid electromechanical transient simulation method of claim 4, wherein the set of differential equations comprises:

direct current line differential equation:

LCC converter direct current side difference equation set:

VSC converter direct current side difference equation set:

in the formula, Δ t is a preset time interval, and n +1 respectively represent n time and n +1 time; the superscripts n and n +1 are added to each parameter to respectively represent the values of the parameter corresponding to the time n and the time n + 1.

6. The LCC-VSC hybrid direct current grid electromechanical transient simulation method of claim 5, wherein the Jacobian matrix is constructed by row ordering and column ordering using the following method:

sequencing the corresponding differential equation sets in a row sequence, namely sequentially sequencing a direct-current line differential equation (8), an LCC converter direct-current side differential equation (9), an LCC converter direct-current side differential equation (10), a VSC converter direct-current side differential equation (13), an LCC converter direct-current side differential equation (11), a VSC converter direct-current side differential equation (14) and a VSC converter direct-current side differential equation (12);

the column sequence corresponds to the mixed direct current network state variable sequence and sequentially comprises current flowing through a direct current circuit, direct current voltage of a side end node connected with the direct current circuit and the LCC converter, direct current circuit node ground capacitance branch current, current injected into the direct current circuit by the LCC converter, current injected into the direct current circuit by the VSC converter and direct current voltage of a side end node connected with the direct current circuit and the VSC converter.

7. The LCC-VSC hybrid direct current grid electromechanical transient simulation method according to claim 4, characterized in that the LCC converter direct current side voltage U_iObtaining by calculation using equation (15):

in the formula, E_iMeasuring the voltage, alpha, for the LCC converter AC_iThe control trigger angle of the LCC converter.

8. An LCC-VSC hybrid direct current grid electromechanical transient simulation device is characterized by comprising:

a dynamic model construction unit: the system is used for constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;

a difference equation set construction unit: the system comprises a simulation step length generation unit, a difference equation set and a difference equation set, wherein the simulation step length generation unit is used for generating a difference equation set corresponding to a dynamic model of the hybrid direct-current power grid according to a preset simulation step length;

a jacobian matrix construction unit: the method comprises the steps of constructing a Jacobian matrix according to a partial derivative term of a state variable of a mixed direct current network of a difference equation set;

an iteration solving unit: the method is used for carrying out iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;

an acquisition unit: and the method is used for obtaining the state variable of the hybrid direct-current power grid at the next simulation moment according to the solving result of the differential equation set at the current simulation moment.

9. An LCC-VSC hybrid direct current power grid electromechanical transient simulation device is characterized by comprising a processor and a storage medium;

the storage medium is used for storing instructions; the processor is configured to operate in accordance with the instructions to perform the steps of the method according to any one of claims 1 to 7.

10. Computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 7.

Technical Field

The invention relates to an LCC-VSC hybrid direct current power grid electromechanical transient simulation method, device and storage medium, and belongs to the technical field of power system automation.

Background

The high-voltage direct-current transmission system (LCC-HVDC) of the power grid commutation converter has the advantages of large transmission capacity, low operation loss, mature and reliable technology and the like, but has the defects of failed commutation of an inverter station, incapability of supplying power to a weak alternating-current system, large reactive power consumption in the operation process and the like; the voltage source type converter high-voltage direct-current transmission system (VSC-HVDC, wherein MMC-HVDC is widely applied) has the advantages of flexible control, small compensation and filtering capacity, no commutation failure, easy formation of a multi-terminal network and the like; but has the defects of lower transmission capacity, higher running loss, high manufacturing cost and the like. The LCC-VSC hybrid direct-current power grid is constructed, stable transmission of long-distance large-capacity electric energy is achieved through the LCC-HVDC, collection of distributed renewable energy sources is achieved through the VSC-HVDC, and the LCC-HVDC hybrid direct-current power grid and the VSC-HVDC are mutually connected and fused and have complementary advantages, so that the LCC-VSC hybrid direct-current power grid becomes an expression form with great development prospects in the future.

Limited by computing power and data parameters, compared with electromagnetic transient simulation, electromechanical transient simulation is a main means for analyzing the safety and stability of the large power grid at present. Because the dynamic response speed of the capacitor and the inductor on the direct current side is high, the alternating current and direct current hybrid power grid has obvious response speed difference, in order to take account of calculation efficiency and accuracy, the alternating current power grid adopts a large step length (h is 0.01 s), the direct current power grid adopts a small step length (h/10-h/4), and alternating current and direct current power grid alternating iterative solution is the mainstream method for the electromechanical transient simulation calculation of the alternating current and direct current hybrid power grid at present.

Aiming at the simulation calculation in the direct current power grid, because the interface of a converter and the direct current network contains a nonlinear equation, the solving steps of the existing method are as follows:

1) suppose a DC voltage U_dCalculating the current I of the converter injected into the DC network without changing_d；

2) Solving a direct current network difference equation set according to the Id, and updating the U_d；

3) The steps 1) and 2) are circulated until the U is reached_dThe iteration error is less than the threshold value.

The existing method is to carry out linearization processing on the original equation and adopt a simple iteration method to alternately solve the dynamic equations at two sides of the interface, but the convergence error caused by alternate iteration under the complex multi-terminal direct-current power network can cause too slow convergence or even incapability of convergence.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, provides an LCC-VSC hybrid direct current power grid electromechanical transient simulation method, device and storage medium, and solves the technical problem that convergence is too slow or even can not be converged due to handover errors caused by alternate iteration under a complex multi-terminal direct current power grid when a nonlinear equation of the direct current power grid is solved in electromechanical transient simulation.

In order to achieve the purpose, the invention is realized by adopting the following technical scheme:

in a first aspect, the invention provides an LCC-VSC hybrid dc grid electromechanical transient simulation method, which includes:

constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;

constructing a difference equation set corresponding to the hybrid direct-current power grid dynamic model according to a preset simulation step length;

constructing a Jacobian matrix according to the partial derivative terms of the state variables of the mixed direct current network of the differential equation set;

performing iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;

and obtaining the state variable of the hybrid direct-current power grid at the next simulation time according to the solving result of the differential equation set at the current simulation time.

Further, before the dynamic model of the hybrid direct-current power grid is constructed, circuit equivalent transformation is carried out on the hybrid direct-current power grid.

Further, the hybrid direct-current power grid dynamic model comprises a direct-current line dynamic model, an LCC converter direct-current side dynamic model and a VSC converter direct-current side dynamic model.

Further, the dc link dynamic model is described by equation (1):

wherein R is_i,j、L_i,j、I_i,jThe equivalent resistance and the equivalent inductance of the direct current line and the current flowing through the direct current line are respectively; t represents time; v_i、V_jThe direct current voltages of nodes i and j at two ends of a direct current line are respectively direct current voltages; the positive direction of the direct current line current flows from i to j, wherein i is less than j;

the direct current side dynamic model of the LCC converter is described by equations (2) to (4):

wherein, U_iThe voltage is the direct current side voltage of the LCC converter; l is_iIs a smoothing reactor; x_iIs the LCC converter equivalent impedance; i is_iInjecting the current of the direct current line into the LCC converter; c_i、I_c,iNode i is equivalent to earth capacitance and current flowing through the node i; s_iThe direct current lines connected with the node i are collected;g_i、h_iare respectively S_iCurrent, head end node, tail end node, g, of medium DC line_i＜h_i；Is an orientation factor, if i ═ g_iThenOtherwise

The VSC converter direct current side dynamic model is described by equations (5) to (7):

V_jI_j＝P_j (5)

wherein: c_j、I_c,jRespectively node j equivalent earth capacitance and current flowing through the node j equivalent earth capacitance; i is_jInjecting the current of the direct current line into the VSC converter; s_jIs a direct current line set connected with the node j;g_j、h_jare respectively S_jCurrent, head end node, tail end node, g, of medium DC line_j＜h_j；Is a direction factor, if j is g_jThen, thenOtherwiseP_jAnd injecting the power of the direct current line for the VSC converter.

Further, the system of difference equations includes:

direct current line differential equation:

LCC converter direct current side difference equation set:

VSC converter direct current side difference equation set:

in the formula, Δ t is a preset time interval, and n +1 respectively represent n time and n +1 time; the superscripts n and n +1 are added to each parameter to respectively represent the values of the parameter corresponding to the time n and the time n + 1.

Further, when the jacobian matrix is constructed, the following method is adopted for row sorting and column sorting:

sequencing the corresponding differential equation sets in a row sequence, namely sequentially sequencing a direct-current line differential equation (8), an LCC converter direct-current side differential equation (9), an LCC converter direct-current side differential equation (10), a VSC converter direct-current side differential equation (13), an LCC converter direct-current side differential equation (11), a VSC converter direct-current side differential equation (14) and a VSC converter direct-current side differential equation (12);

the column sequence corresponds to the mixed direct current network state variable sequence and sequentially comprises current flowing through a direct current circuit, direct current voltage of a side end node connected with the direct current circuit and the LCC converter, direct current circuit node ground capacitance branch current, current injected into the direct current circuit by the LCC converter, current injected into the direct current circuit by the VSC converter and direct current voltage of a side end node connected with the direct current circuit and the VSC converter.

Further, the DC side voltage U of the LCC converter_iObtaining by calculation using equation (15):

in the formula, E_iMeasuring the voltage, alpha, for the LCC converter AC_iThe control trigger angle of the LCC converter.

In a second aspect, an LCC-VSC hybrid dc grid electromechanical transient simulation apparatus includes:

a dynamic model construction unit: the system is used for constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;

a difference equation set construction unit: the system comprises a simulation step length generation unit, a difference equation set and a difference equation set, wherein the simulation step length generation unit is used for generating a difference equation set corresponding to a dynamic model of the hybrid direct-current power grid according to a preset simulation step length;

a jacobian matrix construction unit: the method comprises the steps of constructing a Jacobian matrix according to a partial derivative term of a state variable of a mixed direct current network of a difference equation set;

an iteration solving unit: the method is used for carrying out iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;

an acquisition unit: and the method is used for obtaining the state variable of the hybrid direct-current power grid at the next simulation moment according to the solving result of the differential equation set at the current simulation moment.

In a third aspect, the invention further provides an LCC-VSC hybrid direct current grid electromechanical transient simulation device, which includes a processor and a storage medium;

the storage medium is used for storing instructions;

the processor is configured to operate according to the instructions to perform the steps of the LCC-VSC hybrid direct current grid electromechanical transient simulation method of any one of the first aspect.

In a fourth aspect, the present invention further provides a computer-readable storage medium, on which a computer program is stored, wherein the program is executed by a processor to implement the steps of the LCC-VSC hybrid direct current grid electromechanical transient simulation method according to any one of the first aspect.

Compared with the prior art, the invention has the following beneficial effects:

according to the LCC-VSC hybrid direct current power grid electromechanical transient simulation method, the difference equation set at the current simulation moment is iteratively solved by adopting a Newton-Raphson method, variable elements in the difference equation set and a Jacobian matrix are continuously updated in the iteration process, and the convergence stability is improved; the Jacobian matrix is constructed and obtained according to the partial derivatives of the state variables of the hybrid direct current power grid of the differential equation set, only a small number of matrix elements are used as variables, so that only a small number of variable elements in the Jacobian matrix need to be updated in each iterative solution process, the calculated amount is greatly reduced, the calculation accuracy and the calculation efficiency of the electromechanical transient simulation of the LCC-VSC hybrid direct current power grid can be integrally improved, and the engineering application requirements are met.

Drawings

Fig. 1 is a flowchart of an LCC-VSC hybrid dc power grid electromechanical transient simulation method according to an embodiment of the present invention;

fig. 2 is an equivalent circuit diagram of an LCC-VSC hybrid dc power grid according to an embodiment of the present invention;

fig. 3 is a circuit diagram of an LCC-VSC three-terminal hybrid dc grid according to an embodiment of the present invention;

fig. 4 is a ranking diagram of a jacobian matrix constructed from the circuit diagram provided in fig. 3.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

The first embodiment is as follows:

referring to fig. 1, an embodiment of the present invention provides an LCC-VSC hybrid dc power grid electromechanical transient simulation method, which is used for obtaining state variables of a next simulation time hybrid dc power grid in a simulation manner, and specifically includes the following steps:

step A: constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;

in the embodiment of the present invention, before constructing the dynamic model of the hybrid dc power grid, equivalent transformation may be performed on the circuit of the hybrid dc power grid, and the circuit structure is divided into three parts, i.e., a dc side of the LCC converter, a dc line and a dc side of the VSC converter, as shown in fig. 2, which is an equivalent circuit diagram of the hybrid dc power grid provided in the embodiment of the present invention. Corresponding dynamic models can be respectively constructed for the direct current side of the LCC converter, the direct current line and the direct current side of the VSC converter.

As shown in fig. 2, the dc link dynamics model can be described using equation (1):

wherein R is_i,j、L_i,j、I_i,jThe equivalent resistance and the equivalent inductance of the direct current line and the current flowing through the direct current line are respectively; t represents time; v_i、V_jThe direct current voltages of nodes i and j at two ends of the direct current line are respectively direct current voltages, and the positive direction of the direct current line current flows from i to j.

The direct current side dynamic model of the LCC converter can be described by equations (2) to (4):

wherein, U_iThe voltage is the direct current side voltage of the LCC converter; l is_iIs a smoothing reactor; x_iIs the LCC converter equivalent impedance; i is_iInjecting the current of the direct current line into the LCC converter; c_i、I_c,iNode i is equivalent to earth capacitance and current flowing through the node i; s_iThe direct current lines connected with the node i are collected;g_i、h_iare respectively S_iCurrent, head end node, tail end node, g, of medium DC line_i＜h_i；Is an orientation factor, if i ═ g_iThenOtherwise

The direct current side dynamic model of the VSC can be described by equations (5) to (7):

V_jI_j＝P_j (5)

wherein: c_j、I_c,jRespectively node j equivalent earth capacitance and current flowing through the node j equivalent earth capacitance; i is_jInjecting the current of the direct current line into the VSC converter; s_jIs a direct current line set connected with the node j;g_j、h_jare respectively S_jCurrent, head end node, tail end node, g, of medium DC line_j＜h_j；Is a direction factor, if j is g_jThen, thenOtherwiseP_jAnd injecting the power of the direct current line for the VSC converter.

And B: constructing a difference equation set corresponding to the hybrid direct-current power grid dynamic model according to a preset simulation step length;

corresponding direct current circuit dynamic model, LCC transverter direct current side dynamic model and VSC transverter direct current side dynamic model, corresponding difference equation set includes: the direct current circuit differential equation, the LCC converter direct current side differential equation set and the VSC converter direct current side differential equation set. The embodiment of the invention adopts an implicit trapezoidal integral method to convert a direct current power grid dynamic differential equation into a differential equation set, and specifically comprises the following steps:

direct current line differential equation:

LCC converter direct current side difference equation set:

VSC converter direct current side difference equation set:

in the formula, Δ t is a preset time interval (i.e. simulation step length), and n +1 respectively represent n time and n +1 time; the superscripts n and n +1 are added to each parameter to respectively represent the values of the parameter corresponding to the time n and the time n + 1.

And C: constructing a Jacobian matrix according to the partial derivative terms of the state variables of the mixed direct current network of the differential equation set;

in vector calculus, the jacobian matrix is a matrix in which the first-order partial derivatives are arranged in a certain way, the determinant of which is called jacobian, and the significance of the jacobian matrix is that it embodies an optimal linear approximation of a given point to a micro equation, and therefore, the jacobian matrix is similar to the derivative of a multi-element function.

As an embodiment of the present invention, when constructing the jacobian matrix, the following method may be adopted for row sorting and column sorting:

sequencing the corresponding differential equation sets in a row sequence, namely sequentially sequencing a direct-current line differential equation (8), an LCC converter direct-current side differential equation (9), an LCC converter direct-current side differential equation (10), a VSC converter direct-current side differential equation (13), an LCC converter direct-current side differential equation (11), a VSC converter direct-current side differential equation (14) and a VSC converter direct-current side differential equation (12);

the column sequence corresponds to the mixed direct current network state variable sequence and sequentially comprises current flowing through a direct current circuit, direct current voltage of a side end node connected with the direct current circuit and the LCC converter, direct current circuit node ground capacitance branch current, current injected into the direct current circuit by the LCC converter, current injected into the direct current circuit by the VSC converter and direct current voltage of a side end node connected with the direct current circuit and the VSC converter.

As shown in fig. 3, taking an LCC-VSC three-terminal hybrid dc grid as an example, the three-terminal hybrid dc grid includes a dc network, an LCC converter and two VSC converters; the direct current network comprises three direct current lines, three nodes are corresponding to the three direct current lines, and the nodes can be respectively marked as nodes 1, 2 and 3, wherein the node 1 is connected with the LCC converter, and the nodes 2 and 3 are respectively and correspondingly connected with the two VSC converters. For the hybrid dc power grid shown in fig. 3, the jacobian matrix may be sorted in rows and columns by the following method:

the row ordering is:

group 1: lines (1) - (3) correspond to equation (8);

group 2: line (4) corresponds to equation (9);

group 3: lines (5) - (7) correspond to equation (10) and equation (13);

group 4: lines (8) - (10) correspond to equation (11) and equation (14);

group 5: lines (11) to (12) correspond to equation (12);

the column ordering is:

group 1: the columns (1) to (3) correspond to DC line currentsA partial derivative term;

group 2: column (4) corresponds to LCC converter DC point voltageA partial derivative term;

group 3: the line (5) to (7) corresponds to the branch current of the converter to the ground capacitorA partial derivative term;

group 4: injecting DC network current into the LCC converter corresponding to the column (8)A partial derivative term;

group 5: injecting direct current network current into VSC converter corresponding to columns (9) - (10)A partial derivative term;

group 6: the rows (11) to (12) correspond to the DC point voltage of the VSC converterAnd (4) a partial derivative item.

It should be noted that: the row sorting and the column sorting described above are only one preferred sorting method of the jacobian matrix in the present embodiment, and the jacobian matrix may be another sorting method in the present invention.

As shown in FIG. 4, three constructed for FIG. 3A jacobian matrix of the end hybrid direct-current power grid, wherein a main diagonal element of the jacobian matrix is shown in a box a in fig. 4, and the value of the main diagonal element is relatively large; except for the matrix elements circled by the box b in fig. 4Except for the variables, the other matrix elements are all constants.

Step D: performing iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;

the newton-raphson method is a method of solving equations approximately in the real and complex domains, using the first terms of the taylor series of functions to find the root of the equation, with the greatest advantage of square convergence near a single root of the equation.

It should be noted that the value of the principal diagonal elements of the jacobian matrix generated according to the sorting method of step C is relatively large; only the first calculation needs full matrix LU factorization; subsequent calculations need only update the jacobian matrix part elements (matrix elements as circled by the lower right corner box b in fig. 4)) And its corresponding LU factor.

In this embodiment, the "next simulation time" may be understood as n +1 time, where n time is denoted as the current simulation time, and the time interval between n +1 time and n time is Δ t.

Step E: and obtaining the state variable of the hybrid direct-current power grid at the next simulation time according to the solving result of the differential equation set at the current simulation time.

According to the LCC-VSC hybrid direct current power grid electromechanical transient simulation method, the difference equation set at the current simulation moment is iteratively solved by adopting a Newton-Raphson method, variable elements in the difference equation set and a Jacobian matrix are continuously updated in the iteration process, and the convergence stability is improved; the Jacobian matrix is constructed and obtained according to the partial derivatives of the state variables of the hybrid direct current power grid of the differential equation set, only a small number of matrix elements are used as variables, so that only a small number of variable elements in the Jacobian matrix need to be updated in each iterative solution process, the calculated amount is greatly reduced, the calculation accuracy and the calculation efficiency of the electromechanical transient simulation of the LCC-VSC hybrid direct current power grid can be integrally improved, and the engineering application requirements are met.

Example two:

the embodiment of the invention provides an LCC-VSC hybrid direct current power grid electromechanical transient simulation device, which comprises:

a dynamic model construction unit: the system is used for constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;

a difference equation set construction unit: the system comprises a simulation step length generation unit, a difference equation set and a difference equation set, wherein the simulation step length generation unit is used for generating a difference equation set corresponding to a dynamic model of the hybrid direct-current power grid according to a preset simulation step length;

a jacobian matrix construction unit: the method comprises the steps of constructing a Jacobian matrix according to a partial derivative term of a state variable of a mixed direct current network of a difference equation set;

an iteration solving unit: the method is used for carrying out iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;

an acquisition unit: and the method is used for obtaining the state variable of the hybrid direct-current power grid at the next simulation moment according to the solving result of the differential equation set at the current simulation moment.

The device provided by the embodiment of the present invention can be used to implement the simulation method described in the first embodiment, and the specific implementation method for implementing the corresponding function by each unit in the device may refer to the description of the corresponding part of the first embodiment.

Example three:

the embodiment of the invention also provides an LCC-VSC hybrid direct current power grid electromechanical transient simulation device, which comprises a processor and a storage medium;

a storage medium to store instructions;

the processor is used for operating according to the instructions to execute the steps of the LCC-VSC hybrid direct current grid electromechanical transient simulation method according to the first embodiment.

Example four:

the embodiment of the invention provides a computer-readable storage medium, on which a computer program is stored, wherein the program is executed by a processor to implement the steps of the LCC-VSC hybrid direct current grid electromechanical transient simulation method according to the first embodiment.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.