A simulation method, device and model of a modular converter with a two-stage conversion structure

Abstract

The present invention discloses a simulation method, device and model of a modular converter with a two-stage conversion structure. The method comprises: obtaining an initial model of a modular converter; the initial model comprises an input-stage half-bridge power module and an output-stage dual-active bridge module; establishing a converter equivalent simulation model according to the initial model; the converter equivalent simulation model comprises an input-stage equivalent model and an output-stage equivalent model. Determine the first and second adjustable resistors and the capacitor equivalent resistor of the input-stage equivalent model according to the parameters of the input-stage half-bridge power module. Determine the equivalent reactance and equivalent resistor of the output-stage equivalent model according to the parameters of the output-stage dual-active bridge module; determine the different first and second controlled voltage sources in the input-stage equivalent model according to different switch states of the initial model, the input-stage capacitor current and the input-stage capacitor voltage; determine the different controlled current sources of the output-stage equivalent model according to different switch states of the initial model, the output-stage current and the output-stage capacitor voltage.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technology of modular converters with a two-stage conversion structure, and particularly to a simulation method, device and model for modular converters with a two-stage conversion structure. Background Art

[0002] With the development of flexible DC technology and DC distribution networks, the application fields of modular multilevel converters have been continuously expanding, and their sub-module topologies have been continuously updated. Existing fast models can only meet the simulation needs of half-bridge module cascaded converters. In converters such as AC / DC converters, DC / DC converters, and three-port power electronic transformers in flexible DC systems or medium-voltage DC distribution systems, modular cascaded structures are also adopted, and the module structures are complex. For example, in the direction of power electronic transformers, two-stage or three-stage conversion structures are usually adopted. The input stage can adopt a half-bridge module cascaded structure, and the output stage can adopt a parallel topology of dual active bridge sub-modules to achieve the conversion from high-voltage AC / DC to low-voltage DC. However, in this topology, a single sub-module contains 10 fully controlled switching devices, as well as a coupled transformer and a capacitor. Even if the number of sub-modules in a single bridge arm is in the order of a dozen or dozens in series, if discrete power electronic devices are used to establish a system simulation model, there will still be problems such as too large a simulation scale and difficulty in realizing the simulation. Summary of the Invention

[0003] The present invention provides a simulation method, device and model for modular converters with a two-stage conversion structure to improve the simulation speed and accuracy of modular converters with medium and high voltage levels.

[0004] In a first aspect, an embodiment of the present invention provides a simulation method for a modular converter with a two-stage conversion structure. The simulation method includes:

[0005] Obtain an initial model of the modular converter; wherein, the initial model includes an input-stage half-bridge power module and an output-stage dual active bridge module;

[0006] Establish an equivalent simulation model of the converter according to the initial model; wherein, the equivalent simulation model of the converter includes an input-stage equivalent model and an output-stage equivalent model;

[0007] Determine a first adjustable resistor, a second adjustable resistor and a capacitive equivalent resistor of the input-stage equivalent model according to the parameters in the input-stage half-bridge power module;

[0008] Determine the equivalent reactance and equivalent resistance of the output-stage equivalent model according to the parameters of the output-stage dual active bridge module;

[0009] Determine different first controlled voltage sources and different second controlled voltage sources in the input-stage equivalent model according to different switching states of the initial model, the input-stage capacitor current, and the input-stage capacitor voltage of the input-stage half-bridge power module, and determine different controlled current sources in the output-stage equivalent model according to different switching states of the initial model, the output-stage current, and the output-stage capacitor voltage of the output-stage dual-active-bridge module.

[0010] Optionally, determining different first controlled voltage sources and different second controlled voltage sources in the input-stage equivalent model according to different switching states of the initial model, the input-stage capacitor current, and the input-stage capacitor voltage of the input-stage half-bridge power module, and determining different controlled current sources in the output-stage equivalent model according to different switching states of the initial model, the output-stage current, and the output-stage capacitor voltage of the output-stage dual-active-bridge module includes:

[0011] Establish different KVL differential equations for the initial model according to different switching states of the initial model;

[0012] Perform discretization processing on the different KVL differential equations to obtain different discretized equations;

[0013] Determine different first controlled voltage sources and different second controlled voltage sources in the input-stage equivalent model and determine different controlled current sources in the output-stage equivalent model according to different discretized equations.

[0014] Optionally, establish an equivalent simulation model of the converter according to the initial model, where the equivalent simulation model of the converter includes an input-stage equivalent model and an output-stage equivalent model, including:

[0015] Establish a forward current equivalent path, a capacitor equivalent branch, and a negative current equivalent path of the input-stage equivalent model according to the initial model;

[0016] Establish a commutation output current equivalent path of the output-stage equivalent model according to the initial model;

[0017] Determine a converter simulation model according to the forward current equivalent path, the capacitor equivalent branch, the negative current equivalent path, and the commutation output current equivalent path, where the forward current equivalent path and the negative current equivalent path are connected in parallel, and the forward current equivalent path and the capacitor equivalent branch are connected in series.

[0018] In a second aspect, an embodiment of the present invention further provides a modular converter simulation device with a two-stage conversion structure, and the device includes:

[0019] An acquisition module for acquiring an initial model of a modular converter; wherein the initial model includes an input-stage half-bridge power module and an output-stage dual-active-bridge module;

[0020] An equivalent simulation model establishment module for establishing an equivalent simulation model of the converter according to the initial model; wherein the equivalent simulation model of the converter includes an input-stage equivalent model and an output-stage equivalent model;

[0021] A first determination module for determining a first adjustable resistor, a second adjustable resistor, and a capacitive equivalent resistor of the input-stage equivalent model according to the parameters in the input-stage half-bridge power module;

[0022] A second determination module for determining the equivalent reactance and equivalent resistance of the output-stage equivalent model according to the parameters of the output-stage dual-active-bridge module;

[0023] A third determination module for determining different first controlled voltage sources and different second controlled voltage sources in the input-stage equivalent model according to different switching states of the initial model, the input-stage capacitive current, and the input-stage capacitive voltage of the input-stage half-bridge power module, and determining different controlled current sources in the output-stage equivalent model according to different switching states of the initial model, the output-stage current, and the output-stage capacitive voltage of the output-stage dual-active-bridge module.

[0024] Optionally, the third determination module includes:

[0025] A differential equation establishment unit for establishing different KVL differential equations for the initial model according to different switching states of the initial model;

[0026] A discretization processing unit for performing discretization processing on the different KVL differential equations to obtain different discretized equations;

[0027] A second determination unit for determining different first controlled voltage sources and different second controlled voltage sources in the input-stage equivalent model and determining different controlled current sources in the output-stage equivalent model according to the different discretized equations.

[0028] Optionally, the equivalent simulation model establishment module includes:

[0029] A first path establishment unit for establishing a forward current equivalent path, a capacitive equivalent branch, and a reverse current equivalent path of the input-stage equivalent model according to the initial model;

[0030] A second path establishment unit for establishing a commutation output current equivalent path of the output-stage equivalent model according to the initial model;

[0031] An equivalent simulation model building unit is configured to determine a converter simulation model according to the forward current equivalent path, the capacitor equivalent branch, the reverse current equivalent path, and the commutation output current equivalent path. The forward current equivalent path and the reverse current equivalent path are connected in parallel, and the forward current equivalent path and the capacitor equivalent branch are connected in series.

[0032] In a third aspect, an embodiment of the present invention provides a modular converter simulation model with a two-stage conversion structure. The model is obtained by the modular converter simulation method described in the first aspect above. The modular converter simulation model includes: an input-stage equivalent model and an output-stage equivalent model;

[0033] The input-stage equivalent model includes a first adjustable resistor, a second adjustable resistor, a capacitor equivalent resistor, a first diode, a second diode, a first controlled voltage source, and a second controlled voltage source;

[0034] The output-stage equivalent model includes an equivalent reactance, an equivalent resistor, and a controlled current source;

[0035] The cathode of the first diode and the anode of the second diode are both electrically connected to the positive electrode of the bridge arm of the input-stage equivalent model; the cathode of the second diode is connected to the first end of the first adjustable resistor;

[0036] The anode of the first diode is electrically connected to the first end of the second controlled voltage source, and the second end of the second controlled voltage source is electrically connected to the first end of the second adjustable resistor;

[0037] The second end of the first adjustable resistor and the second end of the second adjustable resistor are both electrically connected to the first end of the first controlled voltage source. The second end of the first controlled voltage source is electrically connected to the first end of the equivalent resistor, and the second end of the equivalent resistor is electrically connected to the negative electrode of the bridge arm of the input-stage equivalent model;

[0038] The controlled current source, the equivalent reactance, and the equivalent resistor are connected in series and are connected in parallel with the converter output capacitor.

[0039] Optionally, the resistance value R t1 of the first adjustable resistor satisfies: R t1 = 0.5NR TON , where N is the number of stages of the two-stage conversion structure; R TON is the on-resistance of the transistor in the initial model;

[0040] The resistance value R t2 of the second adjustable resistor satisfies: R t2 = 0.5NR TON , where N is the number of stages of the two-stage conversion structure; R TONis the on-resistance of the transistor in the initial model;

[0041] The resistance value R of the equivalent resistance of the capacitor c1 satisfies: R c1 = T / (2*C1), where C1 is the capacitance value of the input-stage capacitor of the initial model; T is the sampling period.

[0042] Optionally, the reactance L of the equivalent reactance eq satisfies: L eq = NL1; where N is the number of stages of the two-stage conversion structure; L1 is the inductor value of the transformer in the initial model;

[0043] The resistance value R of the equivalent resistance eq satisfies: R eq = NR TON , where N is the number of stages of the two-stage conversion structure; R TON is the on-resistance of the transistor in the initial model.

[0044] Optionally, the voltage value of the first controlled voltage source is adjusted according to different switching states of the input-stage half-bridge power module in the initial model;

[0045] The voltage value of the second controlled voltage source is adjustable according to different switching states of the input-stage half-bridge model in the initial model;

[0046] The current value of the controlled current source is adjustable according to different switching states of the input-stage half-bridge model in the initial model.

[0047] In the embodiment of the present invention, by obtaining the initial model of the modular converter; wherein, the initial model includes an input-stage half-bridge power module and an output-stage dual-active-bridge module; establishing an equivalent simulation model of the converter according to the initial model; wherein, the equivalent simulation model of the converter includes an input-stage equivalent model and an output-stage equivalent model. Determining the first adjustable resistor, the second adjustable resistor and the equivalent resistance of the capacitor of the input-stage equivalent model according to the parameters in the input-stage half-bridge power module of the initial model; determining the equivalent reactance and the equivalent resistance of the output-stage equivalent model according to the parameters of the output-stage dual-active-bridge module; and determining different first controlled voltage sources and different second controlled voltage sources in the input-stage equivalent model according to different switching states of the initial model, the input-stage capacitor current and the input-stage capacitor voltage of the input-stage half-bridge power module, and determining different controlled current sources of the output-stage equivalent model according to different switching states of the initial model, the output-stage current and the output-stage capacitor voltage of the output-stage dual-active-bridge module. In this way, the simulation model realizes the improvement of the simulation speed of modular converters with medium and high voltage levels. Description of the Drawings

[0048] Figure 1It is a flowchart of a simulation method for a modular converter with a two-stage conversion structure provided by an embodiment of the present invention;

[0049] Figure 2 It is a schematic structural diagram of an initial model of a modular multilevel converter provided by an embodiment of the present invention;

[0050] Figure 3 It is a schematic structural diagram of an equivalent simulation model of a converter provided by an embodiment of the present invention;

[0051] Figure 4 It is a schematic structural diagram of a simulation device for a modular converter with a two-stage conversion structure provided by an embodiment of the present invention. Detailed implementation manners

[0052] The present invention will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. In addition, it should be noted that for the sake of description, only parts related to the present invention rather than all structures are shown in the drawings.

[0053] Figure 1 It is a flowchart of a simulation method for a modular converter with a two-stage conversion structure provided by an embodiment of the present invention. This embodiment is applicable to the establishment of a converter simulation model. This method can be executed by a simulation device for a modular converter with a two-stage conversion structure, and specifically includes the following steps:

[0054] S110. Obtain an initial model of the modular converter.

[0055] Among them, Figure 2 It is a schematic structural diagram of an initial model of a modular multilevel converter provided by an embodiment of the present invention. As Figure 2 shown, this initial model includes an input-stage half-bridge power module 10 and an output-stage dual active bridge module 20. The input-stage half-bridge power module 10 includes N input-stage half-bridge power sub-powers, an input-stage capacitor C1, and an input-stage resistor R sm1 , and the input-stage half-bridge power sub-power includes a first power device IGBT1 and a second power device IGBT2; the positive and negative terminals of N input-stage half-bridge power sub-powers are connected in series in sequence and can be connected to a high-voltage AC power grid. The working states of the input-stage half-bridge power sub-modules in the input-stage half-bridge power module 10 are divided into three working states; among them, the first working state is that TGBT1 is conducting and TGBT2 is off; the second working state is that TGBT1 is off and TGBT2 is conducting; the third working state is that both TGBT1 and TGBT2 are off; the output-stage dual active bridge module 20 includes N output-stage dual active bridge sub-modules, an output-stage capacitor C2, and an output-stage resistor R sm2; The output - stage dual - active - bridge sub - module includes a primary - side full - bridge module, a transformer, and a secondary - side full - bridge module. The primary - side full - bridge module includes four power devices IGBTs. The secondary - side full - bridge module includes four power devices IGBTs. The DC output terminals of the secondary - side full - bridge module are respectively connected in parallel with the output - stage capacitor C2 and the output - stage resistor R sm2 ; N output - stage dual - active - bridge sub - modules are connected in parallel with each other and can be connected to a low - voltage DC power grid or load. In actual operation, a current i is passed into the input - stage half - bridge power module 10 arml , and when the input - stage half - bridge power sub - module is in any working state, two cross - connected power devices IGBTs out of the four power devices IGBTs in the primary - side full - bridge module are turned on. Exemplarily, both IGBT3 and IGBT6 are turned on, or both IGBT4 and IGBT5 are turned on. Through the induction of the coil current of the transformer, two cross - connected power devices IGBTs out of the four power devices IGBTs in the secondary - side full - bridge module are turned on. Exemplarily, both IGBT7 and IGBT10 are turned on, or both IGBT8 and IGBT9 are turned on, so as to realize the output of low - voltage direct current i L1 In actual operation of the converter, the input - stage capacitor voltage U c1i , the current i of the input - stage capacitor c11i , the output - stage capacitor voltage U c2i and the output - stage current i Li are collected in real - time.

[0056] S120. Establish an equivalent simulation model of the converter according to the initial model; among them, the equivalent simulation model of the converter includes an input - stage equivalent model and an output - stage equivalent model.

[0057] Among them, the initial model of the modular multilevel converter with two - stage transformation contains 10N fully - controlled switching devices, 2N capacitors and N isolation transformers. The initial model structure is relatively complex. Building a system simulation model based on discrete power - electronic devices has too many switching devices and state variables, making large - scale simulation difficult to achieve. Therefore, in this solution, an equivalent simulation model of the converter is established according to the initial model Figure 3 is the structural schematic diagram of the equivalent simulation model of the converter provided by the embodiment of the present invention; as Figure 3 shown, the equivalent simulation model of the converter includes an input - stage equivalent model and an output - stage equivalent model. The input - stage equivalent model includes a first adjustable resistor R t1 , a forward - current equivalent path determined by the second diode D2; includes a second adjustable resistor R t2 , a second controlled voltage source V dc2 and a negative - current equivalent path determined by the first diode D1; includes a first controlled voltage source V dc1 and a capacitance equivalent resistor R c1Determined capacitive equivalent branch; the forward current equivalent path and the reverse current equivalent path are connected in parallel, and the forward current equivalent path is connected in series with the capacitive equivalent branch; the output stage equivalent model includes a controlled current source i dco , equivalent reactance L eq and equivalent resistance R eq Determined converter output current equivalent path.

[0058] S130. Determine the first adjustable resistor, the second adjustable resistor and the capacitive equivalent resistance of the input stage equivalent model according to the parameters in the input stage half-bridge power module of the initial model.

[0059] Among them, the parameters in the input stage half-bridge power module of the initial model include the on-resistance R TON of each IGBT device in the input stage half-bridge power module, the number of cascaded input stage half-bridge power sub-modules N in the input stage half-bridge power module, and the capacitance value C1 of the input stage capacitor of the input stage half-bridge power sub-module in the input stage half-bridge power module; according to each parameter, the first adjustable resistor R t1 of the input stage equivalent model can be determined to be 0.5NR TON , the second adjustable resistor R t2 is 0.5NR TON , and the capacitive equivalent resistance R C1 is R C1 =T / (2*C1), where T is the sampling period.

[0060] S140. Determine the equivalent reactance and equivalent resistance of the output stage equivalent model according to the parameters of the output stage dual active bridge module of the initial model.

[0061] Among them, the parameters of the output stage dual active bridge module of the initial model include the number of cascaded output stage half-bridge power sub-modules N in the output stage half-bridge power module, the transformer inductance value L1 in the output stage dual active bridge sub-module, and the on-resistance R TON of each IGBT device in the output stage dual active bridge sub-module; then, according to each parameter, the impedance value L eq of the equivalent reactance of the output stage equivalent model satisfies: L eq =NL 1 ; the resistance value of the equivalent resistance R eq satisfies: R eq =NR TON .

[0062] S150. Determine different first controlled voltage sources and different second controlled voltage sources in the input stage equivalent model according to different switching states of the initial model, the input stage capacitor current and the input stage capacitor voltage of the input stage half-bridge power module, and determine different controlled current sources in the output stage equivalent model according to different switching states of the initial model, the output stage current and the output stage capacitor voltage of the output stage dual active bridge module.

[0063] Specifically, different KVL differential equations are established for the initial model according to different switch states of the initial model; different discretized equations are obtained by discretizing different KVL differential equations; different first controlled voltage sources, different second controlled voltage sources and different controlled power source currents are determined according to different discretized equations. Exemplarily:

[0064] (1) When each input-stage half-bridge sub-module IGBT1 is turned on and IGBT2 is turned off, that is, the input-stage half-bridge module is in the first working state, the output-stage dual-active-bridge sub-module IGBT3, IGBT6, IGBT7, IGBT10 are conducting, and IGBT4, IGBT5, IGBT8, IGBT9 are turned off, according to the current path, the current i injected by the i-th half-bridge module of the input stage into its input-stage capacitor c11i is equal to the arm current iarm1, that is, i c11i =i arm1

[0065] According to the KCL and KVL formulas in the circuit, the differential equation of the i-th sub-module is obtained:

[0066]

[0067] The above formula is discretized as follows, where T is the sampling period

[0068]

[0069] In the formula,

[0070]

[0071] The voltage U of the i-th capacitor in the input stage cli is accumulated to the voltage V of the first controlled voltage source in the input stage dc1 to obtain the first controlled voltage source V dc1 , as follows:

[0072]

[0073] Thus, according to G and H, that is, according to different switch states, the input-stage capacitor current i c11i (k - 1) collected at the (k - 1)th order and the input-stage capacitor voltage U cli (k - 1) collected at the (k - 1)th order, the first controlled voltage source V dc1 is determined; in the formula, R sm1 is the input-stage resistance value, C 1 is the input-stage capacitance value, and m is the turns ratio of the primary and secondary coils of the transformer.

[0074] The second controlled voltage source V of the input stagedc2 i(k) = 0;

[0075] The controlled current source is:

[0076] That is, according to different switch states, the output-stage current i L-1 (k - 1) collected at the (k - 1)th order and the output-stage capacitor voltage U c2i (k - 1) collected at the (k - 1)th order to determine the controlled current source i dco .

[0077] (2) When the IGBT1 of each input-stage half-bridge sub-module is turned on, IGBT2 is turned off, the output-stage dual-active-bridge modules IGBT4, IGBT5, IGBT7, and IGBT10 are conducting, and IGBT3, IGBT6, IGBT8, and IGBT9 are turned off, the current value i c11i injected by the i-th half-bridge module of the input stage into its input-stage capacitor C1 is the same as in the first step. The input-stage first controlled voltage source V dc1 and the second controlled voltage source V dc2 have the same numerical calculation formulas as in the first step, and the controlled current source i dco is also the same as in the first step.

[0078] (3) When the IGBT1 of each input-stage half-bridge sub-module is turned on, IGBT2 is turned off, the output-stage dual-active-bridge modules IGBT3, IGBT6, IGBT8, and IGBT9 are conducting, and IGBT4, IGBT5, IGBT7, and IGBT10 are turned off, the current value i c11i injected by the i-th half-bridge module of the input stage into its input-stage capacitor C is the same as in the first step.

[0079] According to the KCL and KVL formulas in the circuit, the differential equation of the i-th sub-module is obtained:

[0080]

[0081] Discretize the above formula as follows,

[0082]

[0083] where,

[0084]

[0085] The voltage U cli of the i-th capacitor of the input stage is accumulated to the voltage V dc1 of the first controlled voltage source of the input stage to obtain the first controlled voltage source V dc1 , as follows:

[0086]

[0087] Thus, based on G and H, that is, according to different switching states, the input-stage capacitor current i c11i (k - 1) collected at the (k - 1)th order and the input-stage capacitor voltage U cli (k - 1) collected at the (k - 1)th order, the first controlled voltage source V dc1 is determined; where R sm1 is the input-stage resistance value, C 1 is the input-stage capacitance value, and m is the turns ratio of the primary and secondary coils of the transformer.

[0088] The second controlled voltage source V dc2 (k) = 0;

[0089] The controlled current source is:

[0090] That is, according to different switching states, the output-stage current i L-1 (k - 1) collected at the (k - 1)th order and the output-stage capacitor voltage U c2i (k - 1) collected at the (k - 1)th order, the controlled power source is determined.

[0091] (4) When each input-stage half-bridge sub-module IGBT1 is turned on and IGBT2 is turned off, and the output-stage dual-active-bridge modules IGBT4, IGBT5, IGBT8, and IGBT9 are conducting while IGBT3, IGBT6, IGBT7, and IGBT10 are turned off, the current value i c11i injected by the i-th half-bridge module in the input stage into its input-stage capacitor is the same as in the first step. The numerical calculation formulas of the first controlled voltage source V dc1 and the second controlled voltage source V dc2 in the input stage are the same as in the third step, and the controlled current source i dco is the same as in the third step.

[0092] (5) When each input-stage half-bridge sub-module IGBT1 is turned off and IGBT2 is turned on, that is, the input-stage half-bridge module is in the second working state, and the output-stage dual-active-bridge modules IGBT3, IGBT6, IGBT7, and IGBT10 are conducting while IGBT4, IGBT5, IGBT8, and IGBT9 are turned off, according to the current path, the current i c11i injected by the i-th half-bridge module in the input stage into its input-stage capacitor is 0, that is, i c11i = 0.

[0093] The differential equation of the i-th sub-module is obtained according to the KCL and KVL formulas in the circuit

[0094]

[0095] The above formula is discretized as follows:

[0096]

[0097] Wherein,

[0098]

[0099] the voltage U of the i-th capacitor at the input stage cli is not accumulated to the voltage V of the first controlled voltage source at the input stage dc1 , and the voltage V of the first controlled voltage source at the input stage dc1 remains unchanged. It should be noted here that the voltage U of the i-th capacitor at the input stage cli can be used as the value of U cli (k - 1) in the next cycle when the IGBT1 of each input-stage half-bridge sub-module is turned on and the IGBT2 is turned off (i.e., U cli (k - 1) in Formula 2), so as to calculate the value of U cli when the IGBT1 is in the conducting state in the next cycle.

[0100] The second controlled voltage source V at the input stage dc2 (k) = 0;

[0101] The controlled current source is:

[0102] That is, the controlled power source is determined according to different switching states, the output-stage current i L-1 (k - 1) collected at the (k - 1)-th order and the output-stage capacitor voltage U c2i (k - 1) collected at the (k - 1)-th order.

[0103] (6) When the IGBT1 of each input-stage half-bridge sub-module is turned off, the IGBT2 is turned on, the IGBT4, IGBT5, IGBT7, and IGBT10 of the output-stage dual-active-bridge module are conducting, and the IGBT3, IGBT6, IGBT8, and IGBT9 are turned off, the current value i c11i injected by the i-th half-bridge module at the input stage into its input-stage capacitor is the same as that in the fifth step, and the voltage U of the i-th capacitor at the input stage cli is not accumulated to the voltage V of the first controlled voltage source at the input stage dc1 , and the voltage V of the first controlled voltage source at the input stage dc1 remains unchanged. The second controlled voltage source V at the input stage dc2 and the controlled current source are the same as those in the fifth step.

[0104] (7) When the IGBT1 of each input - stage half - bridge sub - module is off and the IGBT2 is on, and the IGBT3, IGBT6, IGBT8, IGBT9 of the output - stage dual - active - bridge module are conducting and the IGBT4, IGBT5, IGBT7, IGBT10 are off, the current value \(i\) injected by the \(i\) - th half - bridge module of the input stage into its input - stage capacitor c11i Is the same as the fifth step.

[0105] The differential equation of the \(i\) - th sub - module is obtained according to the KCL and KVL formulas in the circuit

[0106]

[0107] Discretize the above formula as follows

[0108]

[0109] In the formula,

[0110]

[0111] The voltage \(U\) of the \(i\) - th capacitor in the input stage cli Is not accumulated to the voltage \(V\) of the first controlled voltage source in the input stage dc1 , and the voltage \(V\) of the first controlled voltage source in the input stage dc1 Remains unchanged.

[0112] The second controlled voltage source \(V\) in the input stage dc2 (k)=0.

[0113] The controlled current source is:

[0114] That is, according to different switching states, the output - stage current \(i\) L-1 (k - 1) collected at the \((k - 1)\) - th order and the output - stage capacitor voltage \(U\) c2i (k - 1) collected at the \((k - 1)\) - th order to determine the controlled power source.

[0115] (8) When the IGBT1 of each input - stage half - bridge sub - module is off and the IGBT2 is on, and the IGBT4, IGBT5, IGBT8, IGBT9 of the output - stage dual - active - bridge module are conducting and the IGBT3, IGBT6, IGBT7, IGBT10 are off, the current value \(i_{c11i}\) injected by the \(i\) - th half - bridge module of the input stage into its input - stage capacitor is the same as the fifth step. The voltage \(U_{cli}\) of the \(i\) - th capacitor in the input stage is not accumulated to the voltage \(V_{dc1}\) of the first controlled voltage source in the input stage, and the voltage \(V_{dc1}\) of the first controlled voltage source in the input stage remains unchanged. The second controlled voltage source \(V_{dc2}\) and the controlled current source in the input stage are both the same as the fifth step.

[0116] (9) When all IGBTs 1 to 2 of the input - stage half - bridge module are turned off and all IGBTs 3 to 10 of the output - stage dual - active - bridge module are turned off, that is, when the input - stage half - bridge module is in the second working state, namely the input - stage half - bridge module is in the locked state:

[0117] When the input - stage arm current i arm1 < 0

[0118] i c11i (k)=0

[0119] When the input - stage arm current i arm1 > 0

[0120] i c11i (k)=i arm1

[0121] The output - stage dual - active - bridge module injects the output - stage capacitor current i c12i in an exponentially decaying form, as follows

[0122]

[0123] i c12i (k)=0 (i c12i (k - 1)<0)

[0124] Calculate the input - stage capacitor voltage U cli (k) as follows:

[0125]

[0126] According to the trapezoidal formula of integration, where the equivalent resistance of the capacitor R c1 =T / (2*C1), C 1 is the value of the input - stage capacitor, and T is the sampling period. Accumulate all N input - stage capacitor voltages U cli to the input - stage second controlled voltage source voltage V dc2 to obtain the second controlled voltage source voltage V dc2 as:

[0127] V dc2 (k)=V dc2 (k)+u c1i (k)

[0128] The input - stage first controlled voltage source voltage V dc1 = 0;

[0129] The value of the controlled current source current is: Nmi c12i

[0130] In this solution, a single-module equivalent model is used to replace the cascaded structure of multiple modules in the equivalent model. Compared with the simulation model built with discrete power electronic devices, it can reduce the number of switching devices and state variables, simulate the port voltage and current characteristics of the post-bridge arm of the cascaded module with controlled voltage sources and current sources, and improve the simulation speed. In addition, the input stage of this simulation model uses two diodes and each controlled voltage source to simulate the characteristics of the half-bridge port. The interpolation calculation characteristics of the diodes in the existing simulation software can be used to further improve the simulation accuracy of the model and simplify the model calculation amount.

[0131] An embodiment of the present invention also provides a simulation device for a modular converter with a two-stage conversion structure. The simulation device for a modular converter with a two-stage conversion structure provided by the embodiment of the present invention can execute the simulation method for a modular converter with a two-stage conversion structure provided by any embodiment of the present invention, and has corresponding functional modules and beneficial effects for executing the method. Figure 4 It is a schematic structural diagram of a simulation device for a modular converter with a two-stage conversion structure provided by an embodiment of the present invention, as Figure 4 shown. The simulation device includes:

[0132] An acquisition module 10, configured to acquire an initial model of the modular converter; wherein, the initial model includes an input-stage half-bridge power module and an output-stage dual-active-bridge module;

[0133] An equivalent simulation model establishment module 20, configured to establish an equivalent simulation model of the converter according to the initial model; wherein, the equivalent simulation model of the converter includes an input-stage equivalent model and an output-stage equivalent model;

[0134] A first determination module 30, configured to determine a first adjustable resistor, a second adjustable resistor, and a capacitance equivalent resistor of the input-stage equivalent model according to each parameter in the input-stage half-bridge power module;

[0135] A first determination module 30, configured to determine a first adjustable resistor, a second adjustable resistor, and a capacitance equivalent resistor of the input-stage equivalent model according to each parameter in the input-stage half-bridge power module.

[0136] A second determination module 40, configured to determine an equivalent reactance and an equivalent resistor of the output-stage equivalent model according to each parameter of the output-stage dual-active-bridge module;

[0137] A third determination module 50, configured to determine different first controlled voltage sources and different second controlled voltage sources in the input-stage equivalent model according to different switching states of the initial model, the input-stage capacitance current, and the input-stage capacitance voltage of the input-stage half-bridge power module, and determine different controlled current sources of the output-stage equivalent model according to different switching states of the initial model, the output-stage current, and the output-stage capacitance voltage of the output-stage dual-active-bridge module.

[0138] Optionally, the second determination module includes:

[0139] A differential equation establishment unit for establishing different KVL differential equations for the initial model according to different switching states of the input-stage half-bridge power module;

[0140] A discretization processing unit for discretizing different KVL differential equations to obtain different discretized equations;

[0141] A first determination unit for determining different first controlled voltage sources and different second controlled voltage sources in the input-stage equivalent model according to different discretized equations, and determining different controlled voltage sources of the output-stage equivalent model.

[0142] Optionally, the equivalent simulation model establishment module includes:

[0143] A first path establishment unit for establishing a forward current equivalent path, a capacitance equivalent branch, and a negative current equivalent path of the input-stage equivalent model according to the initial model;

[0144] A second path establishment unit for establishing a commutation output current equivalent path of the output-stage equivalent model according to the initial model;

[0145] An equivalent simulation model establishment unit for determining a converter simulation model according to the forward current equivalent path, the capacitance equivalent branch, the negative current equivalent path, and the commutation output current equivalent path, wherein the forward current equivalent path and the negative current equivalent path are connected in parallel, and the forward current equivalent path and the capacitance equivalent branch are connected in series.

[0146] An embodiment of the present invention also provides a modular converter simulation model with a two-stage conversion structure. Referring to Figure 3 , this simulation model includes: an input-stage equivalent model and an output-stage equivalent model; the input-stage equivalent model includes a first adjustable resistor R t1 , a second adjustable resistor R t2 , a capacitance equivalent resistor R c1 , a first diode D1, a second diode D2, a first controlled voltage source Vdc1, and a second controlled voltage source Vdc2; the output-stage equivalent model includes an equivalent reactance L eq , an equivalent resistor R eq , and a controlled current source i dco ; the cathode of the first diode D1 and the anode of the second diode D2 are both electrically connected to the bridge arm positive electrode AC1+ of the input-stage equivalent model; the cathode of the second diode D2 is connected to the first end of the first adjustable resistor Rt1; the anode of the first diode D1 is electrically connected to the first end of the second controlled voltage source Vdc2, and the second end of the second controlled voltage source Vdc2 is electrically connected to the first end of the second adjustable resistor R t2 ; the first adjustable resistor R t1The second end of and the second adjustable resistor R t2 The second ends of are both electrically connected to the first end of the first controlled voltage source Vdc1. The second end of the first controlled voltage source Vdc1 is electrically connected to the first end of the capacitive equivalent resistor Rc1. The second end of the equivalent resistor R eq is electrically connected to the negative electrode Acn- of the bridge arm of the input stage equivalent model; the controlled current source i dco , the equivalent reactance Leq and the equivalent resistor Req are connected in series and are in parallel with the converter output capacitor Ceq.

[0147] Among them, the fast simulation model of the modular multilevel converter with a two-stage conversion structure proposed in this embodiment uses a single-module equivalent model to replace the cascaded structure of multiple modules. Compared with the simulation model built with discrete power electronic devices, it can reduce the number of switching devices and state variables, and use controlled voltage sources and current sources to simulate the port voltage and current characteristics of the bridge arm after module cascading, thereby improving the simulation speed. In addition, the input stage of this simulation model uses diodes and controlled voltage sources to simulate the half-bridge port characteristics, and the interpolation calculation characteristics of the diodes in the existing simulation software can be used to further improve the simulation accuracy of the model and simplify the model calculation amount.

[0148] Optionally, referring to Figure 3 , the resistance value R t1 of the first adjustable resistor satisfies: R t1 = 0.5NR TON , where N is the number of stages of the two-stage conversion structure; R TON is the on-resistance of the transistor in the initial model;

[0149] The resistance value R t2 of the second adjustable resistor satisfies: R t2 = 0.5NR TON , where N is the number of stages of the two-stage conversion structure; R TON is the on-resistance of the transistor in the initial model;

[0150] The resistance value R c1 of the capacitive equivalent resistor satisfies: R c1 = T / (2*C1), where C1 is the capacitance value of the input stage capacitor in the initial model; T is the sampling period.

[0151] Optionally, referring to Figure 3 , the reactance L eq of the equivalent reactance satisfies: L eq = NL1; where N is the number of stages of the two-stage conversion structure; L1 is the transformer inductance value in the initial model;

[0152] The resistance value R eq of the equivalent resistor satisfies: R eq = NR TON, where N is the number of stages of the two-stage conversion structure; R TON is the on-resistance of the transistor in the initial model.

[0153] Optionally, the voltage value of the first controlled voltage source Vdc1 is adjusted according to different switching states of the input-stage half-bridge power module in the initial model; the voltage value of the second controlled voltage source Vdc2 is adjustable according to different switching states of the input-stage half-bridge model in the initial model; the current value of the controlled current source i dco is adjustable according to different switching states of the input-stage half-bridge model in the initial model. Specifically, different first controlled voltage sources Vdc1 and different second controlled voltage sources Vdc2 in the input-stage equivalent model are determined according to different switching states of the input-stage half-bridge power module, input-stage current, and input-stage capacitor voltage, and different controlled voltage sources i dco of the output-stage equivalent model are obtained according to the method described in the above embodiments, which will not be elaborated here.

[0154] Note that the above is only the preferred embodiment of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A modular converter simulation method with a two-stage conversion structure, characterized in that: include: Acquire an initial model of a modular converter; wherein the initial model includes an input-stage half-bridge power module and an output-stage dual active bridge module; Establishing a converter equivalent simulation model according to the initial model; wherein the converter equivalent simulation model includes an input stage equivalent model and an output stage equivalent model; Determine the first adjustable resistor, the second adjustable resistor and the capacitor equivalent resistor of the input stage equivalent model according to the parameters in the input stage half-bridge power module; Determine the equivalent reactance and equivalent resistance of the output stage equivalent model according to the parameters of the output stage dual active bridge module; Determine different first controlled voltage sources and different second controlled voltage sources in the input stage equivalent model according to different switch states of the initial model, the input stage capacitor current and the input stage capacitor voltage of the input stage half-bridge power module, and determine different controlled current sources of the output stage equivalent model according to different switch states of the initial model, the output stage current and the output stage capacitor voltage of the output stage dual active bridge module; Among them, the converter equivalent simulation model is established according to the initial model, including: Establishing a positive current equivalent path, a capacitance equivalent branch and a negative current equivalent path of the input stage equivalent model according to the initial model; Establishing a commutation output current equivalent path of the output stage equivalent model according to the initial model; The converter simulation model is determined according to the forward current equivalent path, the capacitor equivalent branch, the negative current equivalent path and the commutation output current equivalent path, wherein the forward current equivalent path is connected in parallel with the negative current equivalent path, and the forward current equivalent path is connected in series with the capacitor equivalent branch.

2. The modular converter simulation method of the two-stage conversion structure according to claim 1 is characterized in that: Determining different first controlled voltage sources and different second controlled voltage sources in the input stage equivalent model according to different switch states of the initial model, the input stage capacitor current and the input stage capacitor voltage of the input stage half-bridge power module, and determining different controlled current sources of the output stage equivalent model according to different switch states of the initial model, the output stage current and the output stage capacitor voltage of the output stage dual active bridge module, including: Establishing different KVL differential equations for the initial model according to different switch states of the initial model; Discretizing the different KVL differential equations to obtain different discretized equations; Different first controlled voltage sources and different second controlled voltage sources in the input stage equivalent model are determined according to different discretized equations, and different controlled current sources in the output stage equivalent model are determined.

3. A modular converter simulation device with a two-stage conversion structure, characterized in that: include: An acquisition module is used to acquire an initial model of a modular converter; wherein the initial model includes an input-stage half-bridge power module and an output-stage dual active bridge module; An equivalent simulation model building module is used to build a converter equivalent simulation model based on the initial model; wherein the converter equivalent simulation model includes an input stage equivalent model and an output stage equivalent model; A first determination module, used to determine a first adjustable resistor, a second adjustable resistor and a capacitor equivalent resistor of an input stage equivalent model according to various parameters in the input stage half-bridge power module; A second determination module is used to determine the equivalent reactance and equivalent resistance of the output stage equivalent model according to the parameters of the output stage dual active bridge module; a third determination module, configured to determine different first controlled voltage sources and different second controlled voltage sources in the input-stage equivalent model according to different switch states of the initial model, the input-stage capacitor current and the input-stage capacitor voltage of the input-stage half-bridge power module, and to determine different controlled current sources of the output-stage equivalent model according to different switch states of the initial model, the output-stage current and the output-stage capacitor voltage of the output-stage dual active bridge module; Wherein, the third determination module includes: A first path establishing unit, used for establishing a positive current equivalent path, a capacitance equivalent branch and a negative current equivalent path of the input stage equivalent model according to an initial model; A second path establishing unit, used for establishing a commutation output current equivalent path of the output stage equivalent model according to an initial model; An equivalent simulation model establishing unit is used to determine a converter simulation model based on the forward current equivalent path, the capacitor equivalent branch, the negative current equivalent path and the commutation output current equivalent path, wherein the forward current equivalent path is connected in parallel with the negative current equivalent path, and the forward current equivalent path is connected in series with the capacitor equivalent branch.

4. The modular converter simulation device with a two-stage conversion structure according to claim 3 is characterized in that: The third determining module comprises: A differential equation establishing unit, used for establishing different KVL differential equations for the initial model according to different switch states of the initial model; A discretization processing unit, used for discretizing the different KVL differential equations to obtain different discretized equations; The second determining unit is used to determine different first controlled voltage sources and different second controlled voltage sources in the input stage equivalent model and determine different controlled current sources in the output stage equivalent model according to different discretized equations.

5. A modular converter simulation model with a two-stage conversion structure, characterized in that: Obtained by the modular converter simulation method according to any one of claims 1 to 2 above, the modular converter simulation model comprises: an input stage equivalent model and an output stage equivalent model; The input stage equivalent model includes a first adjustable resistor, a second adjustable resistor, a capacitor equivalent resistor, a first diode, a second diode, a first controlled voltage source and a second controlled voltage source; The output stage equivalent model includes an equivalent reactance, an equivalent resistance and a controlled current source; The cathode of the first diode and the anode of the second diode are both electrically connected to the positive electrode of the bridge arm of the input stage equivalent model; the cathode of the second diode is connected to the first end of the first adjustable resistor; An anode of the first diode is electrically connected to a first end of the second controlled voltage source, and a second end of the second controlled voltage source is electrically connected to a first end of the second adjustable resistor; The second end of the first adjustable resistor and the second end of the second adjustable resistor are both electrically connected to the first end of the first controlled voltage source, the second end of the first controlled voltage source is electrically connected to the first end of the equivalent resistor, and the second end of the equivalent resistor is electrically connected to the negative electrode of the bridge arm of the input stage equivalent model; The controlled current source, the equivalent reactance and the equivalent resistor are connected in series and in parallel with the converter output capacitor.

6. The modular converter simulation model of the two-stage conversion structure according to claim 5 is characterized in that: The resistance value of the first adjustable resistor R t1 Satisfaction: R t1 =0.5NR TON , where N is the number of two-stage transformation structures; R TON is the on-resistance of the transistor in the initial model; The resistance value of the second adjustable resistor R t2 Satisfaction: R t2 =0.5NR TON， Where N is the number of two-stage transformation structures; R TON is the on-resistance of the transistor in the initial model; The resistance value of the capacitor equivalent resistor R c1 Satisfaction: R c1 = T / (2*C1), where C1 is the capacitance of the input stage capacitor of the initial model; T is the sampling period.

7. The modular converter simulation model of the two-stage conversion structure according to claim 5 is characterized in that: The equivalent reactance is the reactance L eq Satisfaction: L eq =NL1; where N is the number of stages of the two-stage transformation structure; L1 is the transformer inductance value in the initial model; The resistance value of the equivalent resistor R eq Satisfaction: R eq =NR TON， Where N is the number of two-stage transformation structures; R TON is the on-resistance of the transistor in the initial model.

8. The modular converter simulation model of the two-stage conversion structure according to claim 5, characterized in that: The voltage value of the first controlled voltage source is adjusted according to different switching states of the input-stage half-bridge power module in the initial model; The voltage value of the second controlled voltage source is adjustable according to different switching states of the input stage half-bridge model in the initial model; The current value of the controlled current source can be adjusted according to different switching states of the input stage half-bridge model in the initial model.

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