An equivalent simulation method for energy storage device sub-module

Abstract

The embodiment of the present application relates to a kind of energy storage device sub-module equivalent simulation method, this method includes the following steps: according to the switching resistance characteristic of switching device, the equivalent model of switching device is established;Energy storage capacitor is discretized, and the equivalent model of energy storage capacitor is established;According to the pre-stored energy storage battery group test data, the equivalent model of energy storage battery group is established;Equivalent voltage and equivalent resistance value of sub-module under different states are calculated;According to the working state of sub-module under different working conditions, each controlled voltage source and controlled resistance are respectively assigned corresponding value.The technical scheme provided by the embodiment of the present application, method implementation is simple, less component is used in model, it is advantageous to improve the simulation efficiency of simulation model.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of power system simulation technology, and in particular to an equivalent simulation method for energy storage device sub-modules. Background Technology

[0002] In 2003, German scholars first proposed the modular multilevel converter (MMC) topology. The bridge arms of this type of topology adopt the form of cascading basic operating units, avoiding the direct series connection of a large number of switching devices and eliminating the problem of consistent triggering. Therefore, it has received widespread attention from academia and industry in recent years and has been rapidly applied to engineering practice.

[0003] The bridge arm of an MMC topology consists of multiple sub-modules connected in series. The structure of the sub-modules can be divided into different types according to the needs of the application. Currently, the most commonly used types are half-bridge sub-modules, full-bridge sub-modules, and clamped dual sub-modules. Among them, half-bridge sub-modules are widely used because of their high reliability, fewer switching devices required, and lower cost.

[0004] Energy storage submodules can be constructed by combining battery packs with half-bridge submodules. A large number of energy storage submodules can be cascaded to form DC distributed energy storage devices. Currently, research on DC distributed energy storage devices is still in its early stages, and system modeling is fundamental to this research. Energy storage devices contain numerous power electronic devices, and the frequent switching of these devices places a significant burden on system simulation calculations. If each submodule is built using traditional methods with a real model, not only is the construction process difficult, but subsequent simulation calculations will also be extremely time-consuming. Summary of the Invention

[0005] Based on the above-mentioned situation of the prior art, the purpose of this embodiment of the invention is to provide an equivalent simulation method for energy storage device sub-modules. This method is simple to implement, uses fewer components in the model, and is more conducive to improving the simulation efficiency of the simulation model.

[0006] To achieve the above objectives, according to one aspect of the present invention, an equivalent simulation method for an energy storage device submodule is provided. The energy storage device submodule includes a first fully controlled switching device and a second fully controlled switching device connected in series, and an energy storage capacitor connected in parallel therewith. One end of the energy storage capacitor is connected to the positive terminal of an energy storage battery pack via a main switch and a pre-charge switch connected in parallel, and the other end is connected to the negative terminal of the energy storage battery pack. The method includes the following steps:

[0007] Based on the switching resistance characteristics of the switching device, an equivalent model of the switching device is established.

[0008] The energy storage capacitor is discretized, and an equivalent model of the energy storage capacitor is established.

[0009] Based on the pre-stored test data of the energy storage battery pack, an equivalent model of the energy storage battery pack is established;

[0010] Calculate the equivalent voltage and equivalent resistance values ​​of the submodule under different states;

[0011] Based on the working status of the submodule under different operating conditions, assign corresponding values ​​to each controlled voltage source and controlled resistor.

[0012] Furthermore, the switching device includes a first fully controlled switching device and a second fully controlled switching device, as well as a main switch and a precharge switch.

[0013] Furthermore, establishing the equivalent model of the switching device includes:

[0014] When current flows through a switching device, its resistance is equivalent to the turn-on resistance R. on ;

[0015] When no current flows through the switching device, its resistance is equivalent to the turn-off resistance R. off .

[0016] Furthermore, the equivalent model of the energy storage capacitor includes:

[0017] Calculate the equivalent voltage V of the energy storage capacitor. c (t):

[0018]

[0019] Where ΔT is the calculation period, C is the capacitance of the energy storage capacitor, and I... c (t) represents the current flowing through the energy storage capacitor at time t;

[0020] The energy storage capacitor branch is equivalent to a resistor R. E With voltage source U E Serial connection:

[0021]

[0022] Furthermore, the establishment of the equivalent model for the energy storage battery pack includes:

[0023] Calculate the equivalent voltage U of the energy storage battery pack Q :

[0024]

[0025] Where G(SOC) represents the functional relationship between the voltage of the energy storage battery pack and the SOC of the battery, Q is the capacity of the energy storage module battery pack, and I... Q This refers to the current flowing through the energy storage battery pack.

[0026] Furthermore, the equivalent voltage U of the submodule under different states is calculated according to the following formula. smEQ and equivalent resistance value R smEQ :

[0027]

[0028]

[0029] Among them, R K1 The equivalent resistance of the main switch, R K2 R is the equivalent resistance of the precharge switch. Q R is the equivalent resistance of the energy storage battery pack. T1 R is the equivalent resistance of the first fully controlled switching device. T2 R is the equivalent resistance of the second fully controlled switching device. S R is the resistance value of the pre-charge resistor connected in series with the pre-charge switch. X R is the resistance of the voltage-equalizing resistor connected in parallel with the energy storage capacitor. L This is the equivalent resistance of the drive circuit.

[0030] Furthermore, the corresponding assignment of values ​​to each controlled voltage source and controlled resistor includes:

[0031] The energy storage device submodule is equivalent to a first controlled voltage source, a first controlled resistor, and a first branch and a second branch connected in parallel, connected in series.

[0032] The first branch includes a third controlled resistor;

[0033] The second branch includes a second controlled voltage source and a second controlled resistor connected in series.

[0034] Furthermore, the process of assigning corresponding values ​​to each controlled voltage source and controlled resistor also includes:

[0035] When the submodule is in a locked state,

[0036] When the bridge arm current i arm When ≥0,

[0037]

[0038] When the bridge arm current i arm When <0,

[0039]

[0040] Among them, u eq1 Let r be the voltage value of the first controlled voltage source. eq1 Let u be the resistance value of the first controlled resistor. eq2 r is the voltage value of the second controlled voltage source.eq2 Let r be the resistance value of the second controlled resistor. eq3 The resistance value of the third controlled resistor.

[0041] Furthermore, the process of assigning corresponding values ​​to each controlled voltage source and controlled resistor also includes:

[0042] When the submodule is in the committed state,

[0043]

[0044] Furthermore, the process of assigning corresponding values ​​to each controlled voltage source and controlled resistor also includes:

[0045] When a submodule is in a cut-off state,

[0046]

[0047] In summary, this invention provides an equivalent simulation method for a submodule of an energy storage device. The method includes the following steps: establishing an equivalent model of the switching device based on its switching resistance characteristics; discretizing the energy storage capacitor to establish an equivalent model of the energy storage capacitor; establishing an equivalent model of the energy storage battery pack based on pre-stored experimental data; calculating the equivalent voltage and equivalent resistance values ​​of the submodule under different states; and assigning corresponding values ​​to each controlled voltage source and controlled resistance according to the operating state of the submodule under different operating conditions. The technical solution provided by this invention is simple to implement, uses fewer components in the model, and is beneficial for improving the simulation efficiency of the simulation model. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the circuit structure of the energy storage device and its sub-modules according to an embodiment of the present invention;

[0049] Figure 2 This is a flowchart of the equivalent simulation method for the energy storage device sub-module in an embodiment of the present invention;

[0050] Figure 3 This is a simplified equivalent model diagram of the energy storage submodule battery pack;

[0051] Figure 4 This is a schematic diagram of the equivalent process of an energy storage device submodule;

[0052] Figure 5 This is an equivalent circuit diagram of an energy storage device submodule. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0054] The technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. According to one embodiment of the present invention, an equivalent simulation method for an energy storage device submodule is provided. Figure 1 The diagram shows a circuit structure schematic of the energy storage device and its sub-modules, as shown below. Figure 1 As shown, the energy storage device submodule includes a first fully controlled switching device IGBT1 and a second fully controlled switching device IGBT2 connected in series, and an energy storage capacitor C connected in parallel with them. One end of the energy storage capacitor C is connected to the positive terminal of the energy storage battery pack B through a main switch K1 and a pre-charge switch K2 connected in parallel. The other end of the pre-charge switch K2 is connected to the negative terminal of the energy storage battery pack B. The pre-charge switch K2 is also connected in series with a pre-charge resistor R. S A voltage-equalizing resistor R is also connected in parallel across the energy storage capacitor C. X and energy harvesting element R L The two ends are respectively connected to one end of the main switch K1 and the precharge switch K2 via the first fuse FU1, and connected to the negative terminal of the energy storage battery pack B via the second fuse FU2. The two ends of the second fully controlled switching device IGBT2 are also connected in parallel with a thyristor Tr and a bypass switch K3. Multiple of these sub-modules are connected in series to form a DC-side distributed independent controllable energy storage device. This energy storage device is connected to the positive DC terminal and the negative DC terminal via isolating switches Q11, Q21, Q22 and Q12, Q23, Q24, respectively. The flowchart of this method is as follows: Figure 2 As shown, it includes the following steps:

[0055] S201. Based on the switching resistance characteristics of the switching devices, establish an equivalent model of the switching devices. The switching devices involved in this step include the first fully controlled switching device IGBT1 and the second fully controlled switching device IGBT2 (including their anti-parallel diodes), as well as the main switch K1 and the pre-charge switch K2. Establishing the equivalent model of the switching devices includes:

[0056] When current flows through a switching device, its resistance is equivalent to the turn-on resistance R. on ;

[0057] When no current flows through the switching device, its resistance is equivalent to the turn-off resistance R. off .

[0058] Specifically, considering the first fully controlled switching device IGBT1 and the second fully controlled switching device IGBT2, along with their anti-parallel diodes, as a whole, their resistance when current flows is equivalent to the turn-on resistance R. on When no current flows through it, its resistance is equivalent to the turn-off resistance R. off ;Right now:

[0059]

[0060]

[0061] Among them, i T1 i is the current flowing through the first fully controlled switching device, IGBT1; T2 This refers to the current flowing through the second fully controlled switching device, IGBT2.

[0062] For the main switch K1 and the precharge switch K2, when the switch state is ON, they can be equivalent to the on-resistance R. on When the switch is in the open state, it can be equivalent to the turn-off resistor R. off ;Right now:

[0063]

[0064]

[0065] Among them, T K1 The state of the main switch K1 is 1 for the on state and 0 for the off state; T K2 This indicates the state of the precharge switch K2: 1 for on and 0 for off.

[0066] S202. Discretize the energy storage capacitor and establish its equivalent model, including the following steps:

[0067] S2021. Calculate the equivalent voltage V of the energy storage capacitor. c (t), the capacitor voltage V can be calculated using the trapezoidal integral method. c (t) is:

[0068]

[0069] Simplifying the above equation, we get:

[0070]

[0071] Where ΔT is the calculation period, C is the capacitance of the energy storage capacitor, and I... c (t) represents the current flowing through the energy storage capacitor at time t.

[0072] S2022, Equivalently represent the energy storage capacitor branch as a resistor R. EWith voltage source U E Serial connection:

[0073]

[0074] S203. Establish an equivalent model of the energy storage battery pack based on the pre-stored test data. In this embodiment of the invention, the voltage of the energy storage battery pack changes continuously with the battery SOC, and the functional relationship is a known quantity, represented by G(x), where x is the battery SOC; the battery SOC can be calculated from the current flowing into the energy storage battery; the simplified equivalent model of the energy storage submodule battery pack is as follows: Figure 3 As shown, where R Q Since it is obtained through experimental testing, it is considered a known quantity, while the equivalent voltage U Q It can be represented as:

[0075]

[0076] Where G(SOC) represents the functional relationship between the voltage of the energy storage battery pack and the SOC of the battery, Q is the capacity of the energy storage module battery pack, and I... Q This refers to the current flowing through the energy storage battery pack.

[0077] The current I flowing through capacitor C and energy storage module battery pack B Q and I E Based on Figure 4 The equivalent process of the medium energy storage submodule was calculated to obtain:

[0078]

[0079] Among them, P loss The energy harvesting element loss of the energy storage device submodule.

[0080] S204. Calculate the equivalent voltage and equivalent resistance values ​​of the submodule under different states. The equivalent process of the energy storage device submodule is as follows: Figure 4 As shown, when performing Thevenin equivalent calculations on the submodules, it is necessary to consider the calculation methods for the equivalent voltage source and equivalent resistance under nine operating conditions: the submodule is in a locked state, an engaged state, and a disconnected state, while the energy storage battery pack is in a disconnected state, a soft-start state, and an engaged state, respectively. To reduce computational complexity, a general calculation method is sought, and then different values ​​are assigned to the corresponding variables for different operating conditions. Figure 4 The equivalent process shown allows for the calculation of the equivalent voltage U of the submodule under different states. smEQ and equivalent resistance value R smEQ :

[0081]

[0082]

[0083] Among them, R K1 The equivalent resistance of the main switch, R K2 R is the equivalent resistance of the precharge switch. Q R is the equivalent resistance of the energy storage battery pack. T1 R is the equivalent resistance of the first fully controlled switching device. T2 R is the equivalent resistance of the second fully controlled switching device. S R is the resistance value of the pre-charge resistor connected in series with the pre-charge switch. X R is the resistance of the voltage-equalizing resistor connected in parallel with the energy storage capacitor. L This is the equivalent resistance of the energy extraction element.

[0084] Based on the equivalence principle and the operating principle of the energy storage submodule, the quantities that change with different operating conditions under all nine operating conditions mainly include R. T1 R T2 R K1 R K2 The working state of the submodule determines R T1 R T2 The value R is determined by the state of the energy storage submodule's battery pack. K1 R K2 ;

[0085] When the working state of a submodule changes, R T1 R T2 The values ​​change as follows:

[0086] a. The submodule operates in a locked state.

[0087] At this time R T1 R T2 The possible values ​​are:

[0088]

[0089]

[0090] b. The submodule is in the active state.

[0091] At this time R T1 R T2 The possible values ​​are:

[0092] R T1 =R on

[0093] R T2 =R off

[0094] c. The submodule is in the cut-off state.

[0095] At this time R T1 R T2 The possible values ​​are:

[0096] R T1 =R off

[0097] R T2 =R on

[0098] When the operating state of the battery pack changes, R K1 R K2 The values ​​change as follows:

[0099] a. Battery pack is in the off state.

[0100] At this time R K1 R K2 The possible values ​​are:

[0101] R K1 =R off

[0102] R K2 =R off

[0103] b. The battery pack is operating in soft-start mode.

[0104] At this time R K1 R K2 The possible values ​​are:

[0105] R K1 =R off

[0106] R K2 =R on

[0107] c. The battery pack is in the engaged state.

[0108] At this time R K1 R K2 The possible values ​​are:

[0109] R K1 =R on

[0110] R K2 =R off

[0111] Substitute the values ​​of each of the above states into the equivalent voltage U smEQ and equivalent resistance value R smEQ The equivalent voltage source and equivalent resistance values ​​under various operating conditions can be calculated from the calculation formula.

[0112] S205. Based on the operating state of the submodule under different working conditions, assign corresponding values ​​to each controlled voltage source and controlled resistor. First, the energy storage device submodule is equivalent to a first controlled voltage source, a first controlled resistor, and a first branch and a second branch connected in parallel, connected in series. The schematic diagram of this equivalent circuit is shown below. Figure 5 As shown, the first branch includes a third controlled resistor; the second branch includes a second controlled voltage source and a second controlled resistor connected in series. When assigning values ​​to the controlled voltage source and the controlled resistor, the assignment schemes for the submodule in the locked, engaged, and disconnected states need to be considered. The energy storage battery pack in the disconnected, soft-start, and engaged states is mainly reflected through different device parameters. Based on the calculation of the equivalent voltage source and equivalent resistance in step S204, values ​​are assigned considering different operating conditions:

[0113] (1) When the submodule is in a locked state

[0114] When the bridge arm current i arm When ≥0,

[0115]

[0116] When the bridge arm current i arm When <0,

[0117]

[0118] Among them, u eq1 Let r be the voltage value of the first controlled voltage source. eq1 Let u be the resistance value of the first controlled resistor. eq2 r is the voltage value of the second controlled voltage source. eq2 Let r be the resistance value of the second controlled resistor. eq3 The resistance value of the third controlled resistor.

[0119] (2) When the submodule is in the activated state

[0120]

[0121] (3) When the submodule is in the cut-off state

[0122]

[0123] Thus, the different device parameters are mainly reflected when the energy storage battery pack is in the disconnected state, soft-start state, and connected state, thereby realizing the equivalent simulation of the energy storage device sub-module.

[0124] In summary, the embodiments of the present invention relate to an equivalent simulation method for a submodule of an energy storage device. This method includes the following steps: establishing an equivalent model of the switching device based on its switching resistance characteristics; discretizing the energy storage capacitor to establish an equivalent model of the energy storage capacitor; establishing an equivalent model of the energy storage battery pack based on pre-stored experimental data of the energy storage battery pack; calculating the equivalent voltage and equivalent resistance values ​​of the submodule under different states; and assigning corresponding values ​​to each controlled voltage source and controlled resistance according to the operating state of the submodule under different operating conditions. The technical solution provided by the embodiments of the present invention is simple to implement, uses fewer components in the model, and is beneficial to improving the simulation efficiency of the simulation model.

[0125] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for equivalent simulation of a submodule of an energy storage device, characterized in that, The energy storage device submodule includes a first fully controlled switching device and a second fully controlled switching device connected in series, and an energy storage capacitor connected in parallel with them. One end of the energy storage capacitor is connected to the positive terminal of the energy storage battery pack through a main switch and a pre-charge switch connected in parallel, and the other end is connected to the negative terminal of the energy storage battery pack. The method includes the following steps: Based on the switching resistance characteristics of the switching device, an equivalent model of the switching device is established. The energy storage capacitor is discretized, and an equivalent model of the energy storage capacitor is established. Based on the pre-stored test data of the energy storage battery pack, an equivalent model of the energy storage battery pack is established; Calculate the equivalent voltage and equivalent resistance values ​​of the submodule under different states; Based on the working status of the submodule under different operating conditions, assign corresponding values ​​to each controlled voltage source and controlled resistor.

2. The method according to claim 1, characterized in that, The switching devices include a first fully controlled switching device and a second fully controlled switching device, as well as a main switch and a precharge switch.

3. The method according to claim 2, characterized in that, The establishment of the equivalent model of the switching device includes: When current flows through a switching device, its resistance is equivalent to the turn-on resistance R. on ; When no current flows through the switching device, its resistance is equivalent to the turn-off resistance R. off .

4. The method according to claim 3, characterized in that, The equivalent model of the energy storage capacitor includes: Calculate the equivalent voltage V of the energy storage capacitor. c (t): Where ΔT is the calculation period, C is the capacitance of the energy storage capacitor, and I... c (t) represents the current flowing through the energy storage capacitor at time t; The energy storage capacitor branch is equivalent to a resistor R. E With voltage source U E Serial connection:

5. The method according to claim 4, characterized in that, The equivalent model for establishing the energy storage battery pack includes: Calculate the equivalent voltage U of the energy storage battery pack Q : Where G(SOC) represents the functional relationship between the voltage of the energy storage battery pack and the SOC of the battery, Q is the capacity of the energy storage module battery pack, and I... Q This refers to the current flowing through the energy storage battery pack.

6. The method according to claim 5, characterized in that, The equivalent voltage U of the submodule under different states is calculated using the following formula. smEQ and equivalent resistance value R smEQ : Among them, R K1 The equivalent resistance of the main switch, R K2 R is the equivalent resistance of the precharge switch. Q R is the equivalent resistance of the energy storage battery pack. T1 R is the equivalent resistance of the first fully controlled switching device. T2 R is the equivalent resistance of the second fully controlled switching device. S R is the resistance value of the pre-charge resistor connected in series with the pre-charge switch. X R is the resistance of the voltage-equalizing resistor connected in parallel with the energy storage capacitor. L This is the equivalent resistance of the drive circuit.

7. The method according to claim 6, characterized in that, The process of assigning corresponding values ​​to each controlled voltage source and controlled resistor includes: The energy storage device submodule is equivalent to a first controlled voltage source, a first controlled resistor, and a first branch and a second branch connected in parallel, connected in series. The first branch includes a third controlled resistor; The second branch includes a second controlled voltage source and a second controlled resistor connected in series.

8. The method according to claim 7, characterized in that, The process of assigning corresponding values ​​to each controlled voltage source and controlled resistor also includes: When the submodule is in a locked state, When the bridge arm current i arm When ≥0, When the bridge arm current i arm When <0, Among them, u eq1 Let r be the voltage value of the first controlled voltage source. eq1 Let u be the resistance value of the first controlled resistor. eq2 r is the voltage value of the second controlled voltage source. eq2 Let r be the resistance value of the second controlled resistor. eq3 The resistance value of the third controlled resistor.

9. The method according to claim 8, characterized in that, The process of assigning corresponding values ​​to each controlled voltage source and controlled resistor also includes: When the submodule is in the committed state, 10. The method according to claim 9, characterized in that, The process of assigning corresponding values ​​to each controlled voltage source and controlled resistor also includes: When a submodule is in a cut-off state,

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