A hierarchical parallel real-time simulation method for fast hybrid DC circuit breakers

Abstract

A hierarchical parallel real-time simulation method for fast hybrid DC circuit breakers first constructs a small-step synthesis model of the submodules of the fast hybrid DCCB, and then builds a two-port equivalent model of the submodule based on the idea of ​​internal node contraction of the system, and then constructs a two-port equivalent model of the fast hybrid DCCB according to the connection relationship of the submodules. While ensuring accuracy, the small-step real-time simulation scale of the fast hybrid DCCB is greatly improved, and the simulation efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of direct current circuitbreakers (DCCBs), and in particular relates to a fast hybrid DCCB hierarchical parallel real-time simulation method. Background Art

[0002] With the rapid development of new sources and loads such as wind power, photovoltaics, energy storage, and electric vehicles, DC microgrids, DC distribution networks, and DC transmission networks are also developing rapidly. However, once a fault occurs in a DC grid, its current rises quickly, and it is difficult to interrupt the DC current. Traditional fast mechanical DC circuit breakers are difficult to quickly cut off the current, and although power electronic devices can be quickly disconnected, they also need to be used with appropriate circuit breakers. Therefore, fast hybrid DC circuit breakers (DCCBs) came into being. They combine the advantages of mechanical circuit breakers and power electronic devices, and can quickly suppress and clear fault currents when a fault occurs. They are important equipment to ensure the safe operation of DC grids.

[0003] In order to accurately analyze the electromagnetic transient (EMT) characteristics of fast hybrid DCCB, it is necessary to simulate and model the fast hybrid DCCB. However, due to the large number of power electronic submodules and power electronic devices in the fast hybrid DCCB, a large amount of computing resources are required during simulation, which brings great challenges to real-time simulation. In particular, when using a small step size to simulate complex EMT, how to ensure the accuracy and efficiency of the solution has become the biggest problem in the real-time simulation of fast hybrid DCCB.

[0004] In order to improve the efficiency of real-time simulation, researchers have tried to perform equivalent modeling on fast hybrid DCCB. Among them, the small-step synthesis method is a modeling method that improves the computational efficiency by parallelizing the simulation calculation process. However, even with the small-step synthesis model, for fast hybrid DCCBs with complex topology and a large number of modules, there are still limitations such as large matrix dimensions, low simulation efficiency, and insufficient hardware resources. In particular, when the number of power electronic modules is large, the real-time simulation efficiency will be significantly reduced.

[0005] Therefore, in order to overcome these challenges, it is necessary to further study more efficient and fast hybrid DCCB real-time simulation methods. This includes exploring new modeling methods, optimizing simulation algorithms, and improving hardware resource utilization, in order to improve real-time simulation efficiency while ensuring simulation accuracy, and provide more powerful support for the safe operation of DC power grids. Summary of the invention

[0006] In view of the above problems, the present invention proposes a hierarchical parallel real-time simulation technology for hybrid DCCB. The hierarchical parallel method first constructs a small-step synthesis model of the hybrid DCCB submodule, and further establishes a dual-port equivalent model of the submodule based on the idea of ​​internal node contraction of the system, and then constructs a dual-port equivalent model of the hybrid DCCB according to the connection relationship of the submodule. While ensuring accuracy, the scale of small-step real-time simulation of hybrid DCCB is greatly improved, and the simulation efficiency is improved.

[0007] The technical solution of the present invention is as follows:

[0008] A hierarchical parallel real-time simulation method for a fast hybrid DC circuit breaker is characterized in that the fast hybrid DCCD is composed of a main branch, a transfer branch and an energy release branch in parallel, wherein the main branch is composed of a fast mechanical circuit breaker and n submodules SM m The transfer branch is composed of s submodules SM t The energy release branch is composed of s and the submodule SM t The hierarchical parallel real-time simulation method comprises:

[0009] -For each submodule SM in the main branch m

[0010] 1) Algorithm-level sub-module modeling:

[0011] For each submodule SM m Discretize to get submodule SM m The discrete state space model is based on the branch voltage V b and branch current I b Output variable, used to represent the submodule SM m The voltage and current response under specific operating conditions is given by the historical current I h It is a state variable used to describe the submodule SM m The current state at a point in the past; the equivalent injection current I s is an input variable to simulate the external current source to the submodule SM m The influence of the branch voltage solution coefficient matrix A is generated v , branch current solution coefficient matrix A i And historical current update coefficient matrix C;

[0012] 3) Module-level submodule SM m Two-port equivalent model construction:

[0013] Based on the idea of ​​node contraction and the principle of interaction between sub-modules, each sub-module SM is constructed. m Two-port equivalent model, this submodule SMm The two-port equivalent model is based on the submodule SM only. m The input voltage V in and output current I out is the output variable;

[0014] 3) Construction of system-level DCCB dual-port equivalent model:

[0015] Each submodule SM m The dual-port equivalent model is cascaded, according to the sub-module SM m The connection relationship between them is used to construct a fast hybrid DCCB two-port equivalent model. The DCCB two-port equivalent model is based on the kth submodule SM m Input voltage V in_k and output current I out_k is the port information; and the state equation is used to update the historical current:

[0016] I h (t+Δt)=C h I h (t)+C s I s (t) (9)

[0017] In the formula, C h Update the current coefficient matrix for the submodule history, C s Equivalent injection current coefficient matrix for submodules;

[0018] - For each submodule SM in the transfer branch t The modeling method is the same as that of the main branch, replacing m with t and n with s in the equation.

[0019] Furthermore, the n submodules SM m and s submodules SM t Satisfies 1≤n≤100,1≤s≤1000.

[0020] Preferably, the submodule SM m Discrete state space model of :

[0021]

[0022] In the formula, A v Solve for the coefficient matrix for the branch voltage, A i is the branch current solution coefficient matrix, C is the historical current update coefficient matrix

[0023] Preferably, the submodule SM m Two-port equivalent model:

[0024]

[0025] In the formula, C 11 is the historical current coefficient matrix of the two-port equivalent model, C 12 Inject the current coefficient matrix into the two-port equivalent model, each submodule SM t The branch voltage V b Divided into input voltage V in , output voltage V out , internal branch voltage V INT , branch current I b Divided into input current I in , output current I out , internal branch current I INT :

[0026]

[0027] Preferably, the DCCB two-port equivalent model:

[0028]

[0029] Among them, the coefficient matrix A is:

[0030]

[0031] Compared with the prior art, the present invention has the following characteristics:

[0032] 1) Through hierarchical parallel processing, the matrix dimension and computational load in simulation calculations can be reduced. In particular, at the system level, the computational burden is further reduced by constructing a two-port equivalent model of the fast hybrid DCCB and ignoring the zero elements in the historical current vector and the equivalent injection current vector. This method of reducing the amount of computation makes real-time simulation possible, which is particularly suitable for simulation analysis of complex structures such as fast hybrid DCCB.

[0033] 2) The high parallelism of the small-step synthesis model is retained, and parallel computing resources can be fully utilized during the simulation process to further improve the simulation speed. Parallel processing not only speeds up the simulation, but also helps to process larger-scale power system models and improve the scalability of the simulation.

[0034] 3) By establishing a submodule model and a two-port equivalent model, the behavior and characteristics of the fast hybrid DCCB can be simulated more accurately. In particular, when considering the interaction principle between submodules and the idea of ​​node contraction, the simulation results can better reflect the dynamic response of the actual power system.

[0035] 4) The present invention is applicable to DC circuit breakers of different voltage levels. By adjusting the number of power electronic sub-modules, it can flexibly adapt to the requirements of different voltage levels and meet the simulation requirements of DC circuit breakers of different power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the hierarchical parallel real-time simulation technology of the present invention.

[0037] Figure 2 It is a topological structure diagram of the fast hybrid DC circuit breaker of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with examples and drawings, but the protection scope of the present invention shall not be limited thereto.

[0039] Please refer to Figure 1 , Figure 1 It is a schematic diagram of the hierarchical parallel real-time simulation technology of the present invention. As can be seen from the figure, the simulation architecture consists of the algorithm level, module level, and system level. The algorithm level is a small-step synthesis model of the main branch and transfer branch submodules of the fast hybrid DCCB, and the module level is a dual-port equivalent model of the submodule. Then, the dual-port equivalent model of the fast hybrid DCCB is constructed according to the connection relationship of the submodule.

[0040] The fast hybrid DCCB is mainly composed of a main branch, a transfer branch and an energy release branch in parallel; the main branch is a fast mechanical circuit breaker and a power electronic submodule SM m Series connection, transfer branch is connected with power electronic submodule SM t The fast hybrid DCCB hierarchical parallel real-time simulation technology includes the following steps:

[0041] Fast hybrid DCCB hierarchical parallel real-time simulation technology, the main branch and transfer branch each contain three levels:

[0042] 1) The first layer --- algorithm level: establish sub-module model

[0043] The branch voltage V b and branch current I b is the output variable, the historical current I h is the state variable, the equivalent injection current I s As input variables, generate coefficient matrix and obtain discrete state space model of power electronic submodule:

[0044]

[0045] 2) The second layer - module level: establish a two-port equivalent model of the submodule

[0046] Each submodule of the fast hybrid DCCB can be regarded as a two-port circuit. In the output equation in equation (1), the branch voltage of each submodule can be divided into input port voltage, output port voltage and internal branch voltage. The branch voltage can be rearranged into the following formula:

[0047]

[0048] Among them, V in is the input voltage of the submodule, V out is the output voltage of the submodule, V INT is the column vector of internal branch voltages;

[0049] Similar to equation (2), the branch current can also be rearranged into the following form:

[0050]

[0051] Among them, I in is the input current of the submodule, I out is the output current of the submodule, I INT is the column vector of internal branch currents;

[0052] Based on equation (1), the state equation of each submodule, that is, the update equation of the historical current, is rearranged as:

[0053]

[0054] Based on equations (2)-(4), when solving the submodules of the fast hybrid DCCB, the zero elements in the historical current vector and the equivalent injection current vector can be ignored to reduce the matrix dimension. At the same time, based on the node contraction idea and the interaction principle between submodules, only the output variable input voltage V is calculated. in and output current I out , you can build a two-port equivalent model of a single submodule:

[0055]

[0056] Formula (5) still retains the high parallelism of the small-step synthesis model, and constructs a dual-port equivalent model of the fast hybrid DCCB submodule through node contraction, which greatly reduces the matrix dimension and calculation amount in the simulation calculation, and is more suitable for real-time simulation of complex structures such as fast hybrid DCCB.

[0057] 3) System level - Layer 3: Establishing a dual-port equivalent model for fast hybrid DCCB

[0058] The dual-port equivalent modules of each submodule are cascaded to construct a dual-port equivalent model of the fast hybrid DCCB;

[0059] According to formula (3) and the port connection relationship of each submodule, the dual-port equivalent model of the fast hybrid DCCB can be obtained as follows:

[0060]

[0061] The coefficient matrix is:

[0062]

[0063] Among them, V in_k is the submodule input voltage, V in is the input voltage of the fast hybrid DCCB; I out_k is the submodule output current phase, I out is the output current of the hybrid DCCB; the subscript k represents the kth module, and the subscript n represents that the main branch of the fast hybrid DCCB contains n modules in total; I s And the I of each submodule in formula (5) s Same; I h is the historical current I of each submodule h_k The column vector composed of

[0064]

[0065] In addition to calculating the port information of the fast hybrid DCCB two-port equivalent model, it is also necessary to calculate its state equation to update the historical current:

[0066] I h (t+Δt)=C h I h (t)+C s I s (t) (9)

[0067] in

[0068]

[0069] 4) For the transfer branch, it includes s submodules, so in the above equations (6)-(10), m is replaced by t and n is replaced by s;

[0070] 5) The number n and s of power electronic submodules are related to the applied voltage of the DC circuit breaker. The higher the voltage, the larger n and s are. The selection range is 1≤n≤100, 1≤s≤1000.

[0071] Figure 2 is a topological structure diagram of the fast hybrid DC circuit breaker of the present invention, Figure 2It can be seen that the fast hybrid DCCB consists of a main branch, a transfer branch, and an energy release branch; the main branch mainly includes a fast mechanical circuit breaker and n power electronic submodules connected in series. The transfer branch mainly includes s power electronic submodules connected in series, and the energy release branch is a variable resistor - Metal Oxide Varistor (MOV). The transfer branch and the energy release branch are connected in parallel to form a stack, and each stack consists of a power electronic submodule SM t The working current flows through the main branch for power transmission. After a fault occurs, the power electronic submodule SM of the transfer branch is turned on. t , shut down the main branch SM m After the main branch current drops to zero, pull open the fast mechanical circuit breaker, and finally disconnect the SM of the transfer branch. t , the follow-flow energy is released through the variable resistor MOV.

[0072] The experiment shows that the present invention first constructs a small-step synthesis model of the fast hybrid DCCB submodule through a hierarchical parallel method, and further establishes a dual-port equivalent model of the submodule based on the idea of ​​internal node contraction of the system, and then constructs a dual-port equivalent model of the fast hybrid DCCB according to the connection relationship of the submodule. While ensuring the accuracy, the small-step real-time simulation scale of the fast hybrid DCCB is greatly improved, the simulation efficiency is improved, and less resources are occupied.

Claims

1. A hierarchical parallel real-time simulation method for a fast hybrid DC circuit breaker, characterized in that: The fast hybrid DCCD is composed of a main branch, a transfer branch and an energy release branch connected in parallel, wherein the main branch is a fast mechanical circuit breaker and n submodules SM m The transfer branch is composed of s submodules SM t The energy release branch is composed of s and the submodule SM t The hierarchical parallel real-time simulation method comprises: -For each submodule SM in the main branch m 1) Algorithm-level sub-module modeling: For each submodule SM m Discretize to get submodule SM m The discrete state space model is based on the branch voltage V b and branch current I b Output variable, used to represent the submodule SM m The voltage and current response under specific operating conditions is given by the historical current I h It is a state variable used to describe the submodule SM m The current state at a point in the past; the equivalent injection current I s is an input variable to simulate the external current source to the submodule SM m The influence of the branch voltage solution coefficient matrix A is generated v , branch current solution coefficient matrix A i And historical current update coefficient matrix C; 2) Module-level submodule SM m Two-port equivalent model construction: Based on the idea of ​​node contraction and the principle of interaction between sub-modules, each sub-module SM is constructed. m Two-port equivalent model, the submodule SM m The two-port equivalent model is based on the submodule SM m The input voltage V in and output current I out is the output variable; 3) Construction of system-level DCCB dual-port equivalent model: Each submodule SM m The two-port equivalent model is cascaded, according to the submodule SM m The connection relationship between them is used to construct a fast hybrid DCCB two-port equivalent model. The DCCB two-port equivalent model is based on the kth submodule SM m Input voltage V in_k and output current I out_k is the port information; and the state equation is used to update the historical current: I h (t+Δt)=C h ·I h (t)+C s ·I s (t) (9) In the formula, C h Update the current coefficient matrix for the submodule history, C s Equivalent injection current coefficient matrix for submodules; - For each submodule SM in the transfer branch t The modeling method is the same as that of the main branch, replacing m with t and n with s in the equation.

2. The hierarchical parallel real-time simulation method for a fast hybrid DC circuit breaker according to claim 1, characterized in that: The n submodules SM m and s submodules SM t Satisfies 1≤n≤100,1≤s≤1000.

3. The hierarchical parallel real-time simulation method for a fast hybrid DC circuit breaker according to claim 1, characterized in that: The submodule SM m Discrete state space model of : In the formula, A v Solve for the coefficient matrix for the branch voltage, A i is the coefficient matrix for branch current solution, and C is the coefficient matrix for updating historical current.

4. The hierarchical parallel real-time simulation method for a fast hybrid DC circuit breaker according to claim 1, characterized in that: The submodule SM m Two-port equivalent model: In the formula, C 11 is the historical current coefficient matrix of the two-port equivalent model, C 12 Inject the current coefficient matrix into the two-port equivalent model, each submodule SM t The branch voltage V b Divided into input voltage V in , output voltage V out , internal branch voltage V INT , branch current I b Divided into input current I in , output current I out , internal branch current I INT :

5. The hierarchical parallel real-time simulation method for a fast hybrid DC circuit breaker according to claim 1, characterized in that: The DCCB two-port equivalent model: Among them, the coefficient matrix A is:

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