Isolated DC microgrid coordinated control method, device, equipment and medium

Abstract

The present invention relates to an island DC microgrid coordinated control method, device, equipment and medium, including determining the unbalanced power of the island DC microgrid according to the DC bus voltage and the DC bus equivalent capacitance; if the unbalanced power meets the preset requirements, determining the first target power and the second target power according to the unbalanced power, and when the first target power meets the second preset requirements, switching the working mode of the energy storage unit to the first preset mode, and when the second target power meets the third preset requirements, switching the working mode of the photovoltaic system unit to the second preset mode; obtaining the voltage offset of the DC bus in the current state; determining the third target power and the fourth target power according to the voltage offset; adjusting the first target power to the third target power, and adjusting the second target power to the fourth target power. The problem of a large amount of unbalanced power generated in the island DC microgrid causing DC bus voltage fluctuations is solved.

Description

Background Art

[0002] As energy and environmental issues become increasingly severe around the world, DC microgrids can effectively utilize natural resources while reducing the adverse effects of small distributed power sources directly connected to large power grids, and have attracted widespread attention from scholars from various countries. Since DC microgrids are rich in distributed renewable energy, their power generation is highly random and volatile due to environmental factors. Therefore, when the microgrid is operated in an unplanned island, a large amount of unbalanced power will be generated inside the microgrid, which will cause fluctuations in the DC bus voltage, seriously affecting the safe and reliable operation of the DC microgrid. Summary of the invention

[0003] In order to overcome the problem of large amount of unbalanced power generated in the existing isolated DC microgrid and causing DC bus voltage fluctuation, the present invention provides a coordinated control method, device and electronic equipment for electric buses participating in an isolated DC microgrid.

[0004] In a first aspect, in order to solve the above technical problems, the present invention provides an island DC microgrid coordinated control method, comprising the following steps:

[0005] Obtain a DC bus voltage and a DC bus equivalent capacitance of the DC bus, and determine the unbalanced power of the island DC microgrid according to the DC bus voltage and the DC bus equivalent capacitance;

[0006] If the unbalanced power meets the preset requirement, the working mode of the energy storage unit is switched to the preset mode, and the energy storage unit is controlled to output the first target power, and the photovoltaic system unit is controlled to output the second target power;

[0007] The energy storage unit is set to a first preset mode, and a voltage offset of the DC bus in a current state is obtained, where the voltage offset represents an offset between a voltage value of the DC bus in a current state and a voltage value in a normal operating state;

[0008] Determining a third target power and a fourth target power according to the voltage offset;

[0009] The first target power is adjusted to a third target power, and the second target power is adjusted to a fourth target power.

[0010] The beneficial effect of the coordinated control method of the isolated DC microgrid provided by the present invention is as follows: the unbalanced power of the isolated DC microgrid is obtained through the DC bus voltage and the DC bus equivalent capacitance, and then the energy storage unit is switched to the first preset mode according to whether the unbalanced power meets the preset requirements. At the same time, the energy storage unit outputs the first target power and the photovoltaic system unit outputs the second target power. At this time, the voltage offset of the DC bus can be obtained, and finally the third target power and the fourth target power are obtained according to the voltage offset. The first target power is corrected by the third target power, and the second target power is corrected by the fourth target power, so that the voltage offset returns to normal, thereby solving the problem of DC bus voltage fluctuation caused by the unbalanced power in the isolated DC microgrid.

[0011] On the basis of the above technical solution, the coordinated control method of the isolated island DC microgrid of the present invention can also be improved as follows.

[0012] Furthermore, the unbalanced power of the island DC microgrid is determined according to the DC bus voltage and the DC bus equivalent capacitance, including:

[0013] According to the DC bus voltage and the DC bus equivalent capacitance, the unbalanced power of the island DC microgrid is determined by the first formula, where the first formula is:

[0014]

[0015] Where Δp represents the unbalanced power of the isolated DC microgrid, C f Indicates the DC bus equivalent capacitance, U dc Indicates the DC bus voltage, represents the derivative of the DC bus voltage.

[0016] The beneficial effect of adopting the above further scheme is: because when the island DC microgrid generates unbalanced power, it will cause fluctuations in the DC bus voltage. Therefore, using the derivative of the DC bus voltage to calculate the unbalanced power of the island DC microgrid is beneficial to determine the operating status of the island DC microgrid at the moment when the DC bus voltage fluctuates.

[0017] Furthermore, the above method also includes:

[0018] Obtaining the maximum charging and discharging power of the energy storage unit, the third output power of the energy storage unit in normal operation, the first droop coefficient of the energy storage unit in the first preset mode, the fourth output power of the photovoltaic system unit in the tracking mode at maximum power, and the second droop coefficient of the photovoltaic system unit in the second preset mode;

[0019] If the unbalanced power meets the preset requirements, the working mode of the energy storage unit is switched to the preset mode, and the energy storage unit is controlled to output the first target power, and the photovoltaic system unit is controlled to output the second target power, including:

[0020] According to the unbalanced power, the DC bus equivalent capacitance, the maximum charging and discharging power of the energy storage unit, the third output power and the first droop coefficient, the first target power is determined by the second formula, wherein the second formula is:

[0021]

[0022] Among them, P es_refs represents the first target power, P Besn Indicates the third output power, m Bes represents the first droop coefficient, P Bes_max Indicates the maximum charging and discharging power of the energy storage unit, ΔU dc Indicates voltage offset, C1 indicates preset value;

[0023] According to the unbalanced power, the working mode of the energy storage unit is switched to a first preset mode, and the energy storage unit is controlled to output a first target power according to a second formula;

[0024] According to the unbalanced power, the fourth output power and the second droop coefficient, the second target power is determined by a third formula, wherein the third formula is:

[0025]

[0026] Among them, P Pv_ref represents the second target power, P MPPT represents the fourth output power, m Pv represents the second droop coefficient, ΔU dc Indicates voltage offset;

[0027] The photovoltaic system unit is controlled to output a second target power according to a third formula.

[0028] The beneficial effect of adopting the above further solution is: the energy storage unit is switched to the first preset mode according to whether the unbalanced power meets the preset requirements. At the same time, the energy storage unit outputs the first target power and the photovoltaic system unit outputs the second target power.

[0029] Furthermore, the above method also includes:

[0030] Obtain proportional parameters, integral parameters and DC bus voltage rated value;

[0031] Get the voltage offset of the DC bus in the current state, including:

[0032] According to the proportional parameter, the integral parameter and the rated value of the DC bus voltage, the voltage offset is determined by the fourth formula, where the fourth formula is:

[0033]

[0034] Among them, ΔU dc Indicates voltage offset, K p represents the scale parameter, T i represents the integral parameter, U dcn Indicates the rated value of DC bus voltage;

[0035] Determining a third target power and a fourth target power according to the voltage offset includes:

[0036] Substitute the voltage offset into the second formula to determine the third target power, and substitute the voltage offset into the third formula to determine the fourth target power.

[0037] The beneficial effect of adopting the above further scheme is: according to the value of the voltage offset, the second formula is substituted to obtain the third target power, thereby adjusting the first target power of the energy storage unit; according to the value of the voltage offset, the third formula is substituted to obtain the fourth target power, thereby adjusting the second target power of the photovoltaic system unit; by adjusting the first target power and the second target power, the influence of the DC bus voltage fluctuation caused by the unbalanced power in the isolated DC microgrid is eliminated.

[0038] Furthermore, the above method also includes:

[0039] After the first target power is adjusted to the third target power, the working state of the energy storage unit is determined. If the working state of the energy storage unit is a preset state, the third target power is reduced to the preset power.

[0040] The beneficial effect of adopting the above further solution is that when the energy storage unit is in a preset state, the third target power is reduced to the preset power, so that the DC bus voltage is more stable.

[0041] Furthermore, the above method also includes:

[0042] Obtaining the DC bus voltage duration, the second-order derivative preset threshold, the preset time threshold, the energy storage state of charge limit value of the energy storage unit at the third preset power, the change in the maximum discharge power and the maximum charging power of the energy storage unit, the real-time state of charge value of the energy storage unit at the third preset power, and the state of charge threshold of the energy storage unit at the third preset power;

[0043] After the first target power is adjusted to the third target power, the working state of the energy storage unit is judged, and if the working state of the energy storage unit is a preset state, the third target power is reduced to the preset power, including:

[0044] According to the DC bus voltage, the DC bus voltage duration, the second-order derivative preset threshold and the preset time threshold, the working state of the energy storage unit is determined by the fifth formula, where the fifth formula is:

[0045]

[0046] Among them, U dc Indicates the DC bus voltage, d 2 U dc / dt 2 Indicates the second-order derivative of the DC bus voltage, C2 indicates the preset threshold of the second-order derivative, t indicates the duration of the second-order derivative of the DC bus voltage greater than 0, t delay Indicates the preset time threshold;

[0047] In d 2 U dc / dt 2 >C2 and t>t delay When the working state of the energy storage unit is determined to be a preset state;

[0048] According to the energy storage state of charge limit value, the change in the maximum discharge power and the maximum charging power of the energy storage unit, the real-time state of charge value and the state of charge threshold, the third droop coefficient is determined by the sixth formula, wherein the sixth formula is:

[0049]

[0050] Among them, m soc represents the third droop coefficient, ΔP Bes_max Indicates the change in the maximum discharge power and maximum charging power of the energy storage unit, x SOC_max Indicates the energy storage state of charge limit, x SOCn represents the state of charge threshold, x SOC Indicates the real-time state of charge value;

[0051] According to the third droop coefficient, the third preset power, the real-time state of charge value and the state of charge threshold, the third target power is reduced to the preset power through the seventh formula, where the seventh formula is:

[0052] P Bes_refs2 =P es_refs1 -m soc (x SOC -x SOCn );

[0053] Among them, P es_refs2 Indicates preset power, P Bes_refs1 Indicates the third target power.

[0054] The beneficial effect of adopting the above further scheme is: the working state of the energy storage unit is judged by the sixth formula. Once the working state of the energy storage unit is judged to be the preset state, the droop line derivative of the first droop coefficient is determined by the sixth formula, and then the third target power is reduced to the preset power by the seventh formula, thereby making the DC bus voltage more stable.

[0055] In a second aspect, the present invention provides an island DC microgrid coordinated control device, comprising:

[0056] The first acquisition module is used to obtain the DC bus voltage and the DC bus equivalent capacitance, and determine the unbalanced power of the island DC microgrid according to the DC bus voltage and the DC bus equivalent capacitance;

[0057] A second acquisition module is used to switch the working mode of the energy storage unit to a preset mode if the unbalanced power meets the preset requirement, and control the energy storage unit to output the first target power, and control the photovoltaic system unit to output the second target power;

[0058] A third acquisition module is used to take the energy storage unit in the first preset mode as the current state, and acquire the voltage offset of the DC bus in the current state, where the voltage offset represents the offset between the voltage value of the DC bus in the current state and the voltage value in the normal operating state;

[0059] A fourth acquisition module, used to determine a third target power and a fourth target power according to the voltage offset;

[0060] The adjustment module is used to adjust the first target power to the third target power, and adjust the second target power to the fourth target power.

[0061] The beneficial effect of the automatic image annotation device provided by the present invention is as follows: the unbalanced power of the isolated DC microgrid is obtained through the DC bus voltage and the DC bus equivalent capacitance, and then the energy storage unit is switched to the first preset mode according to whether the unbalanced power meets the preset requirements. At the same time, the energy storage unit outputs the first target power and the photovoltaic system unit outputs the second target power. At this time, the voltage offset of the DC bus can be obtained, and finally the third target power and the fourth target power are obtained according to the voltage offset. The first target power is corrected by the third target power, and the second target power is corrected by the fourth target power, so that the voltage offset returns to normal, thereby solving the problem of DC bus voltage fluctuation caused by the unbalanced power in the isolated DC microgrid.

[0062] In a third aspect, the present invention further provides an electronic device, including a memory, a processor, and a program stored in the memory and running on the processor, and when the processor executes the program, the steps of the coordinated control method of the island DC microgrid are implemented.

[0063] In a fourth aspect, the present invention further provides a computer-readable storage medium, in which instructions are stored. When the instructions are executed on a terminal device, the terminal device executes the steps of the coordinated control method of an island DC microgrid. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0065] Figure 1 A schematic flow chart of a coordinated control method for an island DC microgrid according to an embodiment of the present invention;

[0066] Figure 2 This is a schematic diagram of the structure of an isolated DC microgrid coordinated control device according to an embodiment of the present invention;

[0067] Figure 3 A simulation model of an island DC microgrid constructed for an embodiment of the present invention;

[0068] Figure 4 is the waveform diagram of the unbalanced power of the island DC microgrid obtained by the first formula;

[0069] Figure 5 is the waveform diagram of the DC bus voltage after eliminating the voltage offset;

[0070] Figure 6 This is a waveform diagram of the DC bus voltage after the energy storage unit enters a preset state. DETAILED DESCRIPTION

[0071] The following examples are provided to further explain and supplement the present invention and do not constitute any limitation to the present invention.

[0072] like Figure 1 As shown, the coordinated control method of the isolated DC microgrid in the embodiment of the present invention includes the following steps:

[0073] S1. Obtain a DC bus voltage and a DC bus equivalent capacitance of the DC bus, and determine the unbalanced power of the island DC microgrid according to the DC bus voltage and the DC bus equivalent capacitance.

[0074] Optionally, the unbalanced power of the island DC microgrid is determined according to the DC bus voltage and the DC bus equivalent capacitance, including:

[0075] According to the DC bus voltage and the DC bus equivalent capacitance, the unbalanced power of the isolated DC microgrid is determined by the first formula, where the first formula is:

[0076]

[0077] Where Δp represents the unbalanced power of the isolated DC microgrid, C f Indicates the DC bus equivalent capacitance, U dc Indicates the DC bus voltage, represents the derivative of the DC bus voltage.

[0078] S2: If the unbalanced power meets the preset requirement, the working mode of the energy storage unit is switched to the preset mode, and the energy storage unit is controlled to output the first target power, and the photovoltaic system unit is controlled to output the second target power.

[0079] Optionally, the preset requirement refers to a power range that the unbalanced power satisfies;

[0080] The first preset mode refers to the working mode corresponding to the energy storage unit when the unbalanced power meets the preset requirements.

[0081] Optionally, also include:

[0082] Obtaining the maximum charging and discharging power of the energy storage unit, the third output power of the energy storage unit in normal operation, the first droop coefficient of the energy storage unit in the first preset mode, the fourth output power of the photovoltaic system unit in the tracking mode at maximum power, and the second droop coefficient of the photovoltaic system unit in the second preset mode;

[0083] If the unbalanced power meets the preset requirements, the working mode of the energy storage unit is switched to the preset mode, and the energy storage unit is controlled to output the first target power, and the photovoltaic system unit is controlled to output the second target power, including:

[0084] According to the unbalanced power, the DC bus equivalent capacitance, the maximum charging and discharging power of the energy storage unit, the third output power and the first droop coefficient, the first target power is determined by the second formula, wherein the second formula is:

[0085]

[0086] Among them, P es_refs represents the first target power, P Besn Indicates the third output power, m Bes represents the first droop coefficient, P Bes_max Indicates the maximum charging and discharging power of the energy storage unit, ΔU dc Indicates voltage offset, C1 indicates preset value;

[0087] According to the unbalanced power, the working mode of the energy storage unit is switched to a first preset mode, and the energy storage unit is controlled to output a first target power according to a second formula;

[0088] According to the unbalanced power, the fourth output power and the second droop coefficient, the second target power is determined by a third formula, wherein the third formula is:

[0089]

[0090] Among them, P Pv_ref represents the second target power, P MPPT represents the fourth output power, m Pv represents the second droop coefficient, ΔU dc Indicates voltage offset;

[0091] The photovoltaic system unit is controlled to output a second target power according to a third formula.

[0092] S3, setting the energy storage unit to a first preset mode, obtaining a voltage offset of the DC bus in a current state, where the voltage offset represents an offset between a voltage value of the DC bus in a current state and a voltage value in a normal operating state.

[0093] Optionally, the normal operating state refers to an operating state of the isolated DC microgrid when no DC bus voltage fluctuation occurs.

[0094] Optionally, also include:

[0095] Obtain proportional parameters, integral parameters and DC bus voltage rated value;

[0096] Get the voltage offset of the DC bus in the current state, including:

[0097] According to the proportional parameter, the integral parameter and the rated value of the DC bus voltage, the voltage offset is determined by the fourth formula, where the fourth formula is:

[0098]

[0099] Among them, ΔU dc Indicates voltage offset, K p represents the scale parameter, T i represents the integral parameter, U dcn Indicates the rated value of DC bus voltage;

[0100] S4, determining a third target power and a fourth target power according to the voltage offset.

[0101] Optionally, the voltage offset is substituted into the second formula to determine the third target power, and the voltage offset is substituted into the third formula to determine the fourth target power.

[0102] S5, adjusting the first target power to a third target power, and adjusting the second target power to a fourth target power.

[0103] The method further includes S6, which is as follows:

[0104] After the first target power is adjusted to the third target power, the working state of the energy storage unit is determined. If the working state of the energy storage unit is a preset state, the third target power is reduced to the preset power.

[0105] Optionally, also include:

[0106] Obtaining the DC bus voltage duration, the second-order derivative preset threshold, the preset time threshold, the energy storage state of charge limit value of the energy storage unit at the third preset power, the change in the maximum discharge power and the maximum charging power of the energy storage unit, the real-time state of charge value of the energy storage unit at the third preset power, and the state of charge threshold of the energy storage unit at the third preset power;

[0107] After the first target power is adjusted to the third target power, the working state of the energy storage unit is judged, and if the working state of the energy storage unit is a preset state, the third target power is reduced to the preset power, including:

[0108] According to the DC bus voltage, the DC bus voltage duration, the second-order derivative preset threshold and the preset time threshold, the working state of the energy storage unit is determined by the fifth formula, where the fifth formula is:

[0109]

[0110] Among them, U dc Indicates the DC bus voltage, d 2 U dc / dt 2 Indicates the second-order derivative of the DC bus voltage, C2 indicates the preset threshold of the second-order derivative, t indicates the duration of the second-order derivative of the DC bus voltage greater than 0, t delay Indicates the preset time threshold;

[0111] In d 2 U dc / dt 2 >C2 and t>t delay When the working state of the energy storage unit is determined to be a preset state;

[0112] According to the energy storage state of charge limit value, the change in the maximum discharge power and the maximum charging power of the energy storage unit, the real-time state of charge value and the state of charge threshold, the third droop coefficient is determined by the sixth formula, wherein the sixth formula is:

[0113]

[0114] Among them, m soc represents the third droop coefficient, ΔP Bes_maxIndicates the change in the maximum discharge power and maximum charging power of the energy storage unit, x SOC_max Indicates the energy storage state of charge limit, x SOCn represents the state of charge threshold, x SOC Indicates the real-time state of charge value;

[0115] According to the third droop coefficient, the third preset power, the real-time state of charge value and the state of charge threshold, the third target power is reduced to the preset power through the seventh formula, where the seventh formula is:

[0116] P Bes_refs2 =P es_refs1 -m soc (x SOC -x SOCn );

[0117] Among them, P es_refs2 Indicates preset power, P Bes_refs1 Indicates the third target power.

[0118] like Figure 2 As shown, the island DC microgrid coordinated control device of the embodiment of the present invention includes:

[0119] A first acquisition module 202 is used to acquire a DC bus voltage and a DC bus equivalent capacitance, and determine the unbalanced power of the island DC microgrid according to the DC bus voltage and the DC bus equivalent capacitance;

[0120] The second acquisition module 203 is used to switch the working mode of the energy storage unit to a preset mode if the unbalanced power meets the preset requirement, and control the energy storage unit to output the first target power, and control the photovoltaic system unit to output the second target power;

[0121] A third acquisition module 204 is used to take the energy storage unit in the first preset mode as the current state, and acquire the voltage offset of the DC bus in the current state, where the voltage offset represents the offset between the voltage value of the DC bus in the current state and the voltage value in the normal operating state;

[0122] The fourth acquisition module 205 is used to determine the third target power and the fourth target power according to the voltage offset.

[0123] The adjustment module 205 is configured to adjust the first target power to the third target power, and adjust the second target power to the fourth target power.

[0124] Optionally, the first acquisition module 202 includes:

[0125] The first calculation module is used to determine the unbalanced power of the island DC microgrid according to the DC bus voltage and the DC bus equivalent capacitance through a first formula, wherein the first formula is:

[0126]

[0127] Where Δp represents the unbalanced power of the isolated DC microgrid, C f Indicates the DC bus equivalent capacitance, U dc Indicates the DC bus voltage, represents the derivative of the DC bus voltage.

[0128] Optionally, the second acquisition module 203 includes:

[0129] A fifth acquisition module, used to acquire the maximum charging and discharging power of the energy storage unit, the third output power of the energy storage unit under normal operating conditions, the first droop coefficient of the energy storage unit under the first preset mode, the fourth output power of the photovoltaic system unit in the tracking mode at maximum power, and the second droop coefficient of the photovoltaic system unit under the second preset mode;

[0130] The second calculation module is used to determine the first target power through a second formula according to the unbalanced power, the DC bus equivalent capacitance, the maximum charging and discharging power of the energy storage unit, the third output power and the first droop coefficient, wherein the second formula is:

[0131]

[0132] Among them, P es_refs represents the first target power, P Besn Indicates the third output power, m Bes represents the first droop coefficient, P Bes_max Indicates the maximum charging and discharging power of the energy storage unit, ΔU dc Indicates voltage offset, C1 indicates preset value;

[0133] In addition, according to the unbalanced power, the working mode of the energy storage unit is switched to the first preset mode, and the energy storage unit is controlled to output the first target power according to the second formula;

[0134] The third calculation module is used to determine the second target power according to the unbalanced power, the fourth output power and the second droop coefficient by using a third formula, wherein the third formula is:

[0135]

[0136] Among them, P Pv_ref represents the second target power, P MPPT represents the fourth output power, m Pv represents the second droop coefficient, ΔU dc Indicates voltage offset;

[0137] In addition, the photovoltaic system unit is controlled to output a second target power according to a third formula.

[0138] Optionally, the third acquisition module 204 includes:

[0139] A sixth acquisition module, used for acquiring a proportional parameter, an integral parameter and a rated value of a DC bus voltage;

[0140] The fourth calculation module is used to determine the voltage offset according to the proportional parameter, the integral parameter and the rated value of the DC bus voltage by using a fourth formula, wherein the fourth formula is:

[0141]

[0142] Among them, ΔU dc Indicates voltage offset, K p represents the scale parameter, T i represents the integral parameter, U dcn Indicates the rated value of the DC bus voltage.

[0143] Optionally, the device also includes a preset power determination module, which is used to judge the working state of the energy storage unit after the first target power is adjusted to the third target power, and if the working state of the energy storage unit is a preset state, reduce the third target power to the preset power.

[0144] Optionally, the preset power determination module includes:

[0145] A seventh acquisition module is used to obtain the DC bus voltage duration, the second-order derivative preset threshold, the preset time threshold, the energy storage state of charge limit value of the energy storage unit at the third preset power, the change in the maximum discharge power and the maximum charging power of the energy storage unit, the real-time state of charge value of the energy storage unit at the third preset power, and the state of charge threshold of the energy storage unit at the third preset power;

[0146] The fifth calculation module is used to determine the working state of the energy storage unit according to the DC bus voltage, the DC bus voltage duration, the second-order derivative preset threshold and the preset time threshold through a fifth formula, wherein the fifth formula is:

[0147]

[0148] Among them, U dc Indicates the DC bus voltage, d 2 U dc / dt 2 Indicates the second-order derivative of the DC bus voltage, C2 indicates the preset threshold of the second-order derivative, t indicates the duration of the second-order derivative of the DC bus voltage greater than 0, t delay Indicates the preset time threshold;

[0149] In addition, in d 2 U dc / dt 2 >C2 and t>t delay When the working state of the energy storage unit is determined to be a preset state;

[0150] The sixth calculation module is used to determine the droop line derivative of the first droop coefficient through a sixth formula according to the energy storage state of charge limit value, the change in the maximum discharge power and the maximum charging power of the energy storage unit, the real-time state of charge value and the state of charge threshold, wherein the sixth formula is:

[0151]

[0152] Among them, m soc represents the sag line derivative, ΔP Bes_max Indicates the change in the maximum discharge power and maximum charging power of the energy storage unit, x SOC_max Indicates the energy storage state of charge limit, x SOCn represents the state of charge threshold, x SOC Indicates the real-time state of charge value;

[0153] The seventh calculation module is used to reduce the third target power to the preset power through a seventh formula according to the droop line derivative, the third preset power, the droop line derivative, the real-time state of charge value and the state of charge threshold, wherein the seventh formula is:

[0154] P Bes_refs2 =P es_refs1 -m soc (x SOC -x SOCn );

[0155] Among them, P es_refs2 Indicates preset power, P Bes_refs1 Indicates the third target power.

[0156] A specific application of this embodiment:

[0157] like Figure 3 As shown, a simulation model of an isolated DC microgrid is built based on the PSCAD simulation platform. Now, according to the coordinated control method of the isolated DC microgrid in this embodiment, the parameters are: P Bes_max =500KW, P Load =300KW, C f =400μF, U dcn =20KV, x SOCn =89%, x SOC_max =0.2MW, m Bes =5,m Pv =5, C2=0, K p =1,Ti =2,P Pv =5MW, C f =400μF, the above parameters are used as the experimental parameters of this embodiment to carry out the following experiment (for the convenience of explanation, this embodiment takes the DC microgrid entering the island operation mode at 3S as an example):

[0158] S1, according to the DC bus voltage and the DC bus equivalent capacitance, the unbalanced power of the island DC microgrid is determined by the first formula.

[0159] like Figure 4 ,for Figure 4 In the lower row of figures, the horizontal axis represents time, the vertical axis represents the value of the DC bus voltage at each time point, the solid line represents the DC bus voltage obtained by this embodiment, and the dotted line represents the DC bus voltage obtained by the prior art. Figure 4 In the upper row of figures, the horizontal axis represents time, the vertical axis represents the value of the unbalanced power at each time point, the solid line represents the unbalanced power calculated by this embodiment, and the dotted line represents the unbalanced power obtained by the prior art.

[0160] Through the above experiment, it can be seen that according to the fluctuation moment of the DC bus voltage, the unbalanced power can be correctly calculated by the first formula, which is conducive to observing the relationship between the DC bus voltage and the unbalanced power.

[0161] S2, when the unbalanced power meets the preset requirements, determine the first target power and the second target power, and when the first target power meets the second preset requirement, switch the energy storage unit to the first preset mode, and when the second target power meets the third preset requirement, switch the photovoltaic system unit to the second preset mode.

[0162] S3, taking the energy storage unit in the first preset mode and the photovoltaic system unit in the second preset mode as the current state, and obtaining the voltage offset of the DC bus in the current state.

[0163] Through the second and third formulas, we can get ΔU dc =0.4KV, which means that even if the current mode of the energy storage unit and the current mode of the photovoltaic system unit are switched, there is still a voltage offset, and the voltage offset at this time needs to be eliminated.

[0164] S4, according to the proportional parameter, the integral parameter and the rated value of the DC bus voltage, the voltage offset is determined by the fourth formula. After the voltage offset is determined, the voltage offset is substituted into the second formula to determine the third target power. The voltage offset is substituted into the third formula to determine the fourth target power.

[0165] like Figure 5As shown, the horizontal axis represents time, the vertical axis represents the DC bus voltage, the solid line represents the DC bus voltage after the voltage offset is eliminated through this embodiment, and the dotted line represents the DC bus voltage obtained without eliminating the voltage offset. By comparing the solid line with the dotted line, it can be seen that after the first target power and the second target power are readjusted by the voltage offset, the DC bus voltage is more stable.

[0166] S5, after the first target power is adjusted to the third target power, the working state of the energy storage unit is determined, and if the working state of the energy storage unit is a preset state, the third target power is reduced to the preset power.

[0167] When the working state of the energy storage unit is the preset state, m is obtained by the sixth formula: soc =5, and then through the seventh formula, the third target power is reduced to the preset power, such as Figure 6 As shown, for Figure 6 In the following row of figures, the horizontal axis represents time, the vertical axis represents the result of calculating the second-order derivative of the DC bus voltage, the solid line represents the result of calculating the second-order derivative of the DC bus voltage when the energy storage unit is in the preset state, and the dotted line represents the result of calculating the second-order derivative of the DC bus voltage when the energy storage unit is in the original working state (the original working state refers to the working state when the energy storage unit has not entered the preset state). Figure 6 In the upper row of figures, the horizontal axis represents time, the vertical axis represents preset power, the solid line represents the output power when the energy storage unit is in the preset state, and the dotted line represents the output power when the energy storage unit is in the original working state.

[0168] pass Figure 6 It can be seen that when the energy storage unit is in the preset state, the second-order derivative of the DC bus voltage is continuously greater than 0 for a long time. Therefore, the energy storage unit will not be directly shut down and stop output, which is conducive to further controlling the stability of the DC bus voltage through the low-power output of the energy storage unit.

[0169] An electronic device according to an embodiment of the present invention includes a memory, a processor, and a program stored in the memory and running on the processor. When the processor executes the program, some or all steps of the above-mentioned island DC microgrid coordinated control method are implemented.

[0170] Among them, the electronic device can be a computer, a mobile phone, etc. Correspondingly, its program is a computer software or a mobile phone APP, etc., and the above-mentioned parameters and steps in an electronic device of the present invention can refer to the parameters and steps in the embodiment of the coordinated control method of the isolated DC microgrid in the above text, and will not be repeated here.

[0171] Those skilled in the art know that the present invention can be implemented as a device, method or computer program product. Therefore, the present disclosure can be specifically implemented in the following forms, namely: it can be complete hardware, it can be complete software (including firmware, resident software, microcode, etc.), or it can be a combination of hardware and software, generally referred to as "circuit", "module" or "device" herein. In addition, in some embodiments, the present invention can also be implemented in the form of a computer program product in one or more computer-readable media, and the computer-readable medium contains computer-readable program code. Computer-readable storage media can be, for example, but not limited to - electrical, magnetic, optical, electromagnetic, infrared, or semiconductor devices, devices or components, or any combination of the above.

[0172] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0173] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A coordinated control method for an island DC microgrid, characterized in that: The following steps are involved: Obtaining a DC bus voltage and a DC bus equivalent capacitance of the DC bus, and determining an unbalanced power of the island DC microgrid according to the DC bus voltage and the DC bus equivalent capacitance; If the unbalanced power meets the preset requirement, the working mode of the energy storage unit is switched to the preset mode, and the energy storage unit is controlled to output the first target power, and the photovoltaic system unit is controlled to output the second target power; Taking the energy storage unit in the first preset mode as the current state, obtaining the voltage offset of the DC bus in the current state, wherein the voltage offset represents the offset between the voltage value of the DC bus in the current state and the voltage value in the normal operating state; Determining a third target power and a fourth target power according to the voltage offset; adjusting the first target power to the third target power, and adjusting the second target power to the fourth target power; The step of determining the unbalanced power of the island DC microgrid according to the DC bus voltage and the DC bus equivalent capacitance includes: According to the DC bus voltage and the DC bus equivalent capacitance, the unbalanced power of the island DC microgrid is determined by a first formula, wherein the first formula is: Where Δp represents the unbalanced power of the isolated DC microgrid, C f Indicates the DC bus equivalent capacitance, U dc Indicates the DC bus voltage, represents the derivative of the DC bus voltage; The method further includes: obtaining the maximum charging and discharging power of the energy storage unit, the third output power of the energy storage unit in the normal operating state, the first droop coefficient of the energy storage unit in the first preset mode, the fourth output power of the photovoltaic system unit in the tracking mode at the maximum power, and the second droop coefficient of the photovoltaic system unit; If the unbalanced power meets the preset requirement, the working mode of the energy storage unit is switched to the preset mode, and the energy storage unit is controlled to output the first target power, and the photovoltaic system unit is controlled to output the second target power, including: The first target power is determined by a second formula according to the unbalanced power, the DC bus equivalent capacitance, the maximum charging and discharging power of the energy storage unit, the third output power and the first droop coefficient, wherein the second formula is: Among them, P es_refs represents the first target power, P Besn Indicates the third output power, m Bes represents the first droop coefficient, P Bes_max Indicates the maximum charging and discharging power of the energy storage unit, ΔU dc Indicates voltage offset, C1 indicates preset value; According to the unbalanced power, the working mode of the energy storage unit is switched to a first preset mode, and the energy storage unit is controlled to output a first target power according to a second formula; According to the unbalanced power, the fourth output power and the second droop coefficient, the second target power is determined by a third formula, wherein the third formula is: Among them, P Pv_ref represents the second target power, P MPPT represents the fourth output power, m Pv represents the second droop coefficient, ΔU dc Indicates voltage offset; The method further includes: Obtain proportional parameters, integral parameters and DC bus voltage rated value; Then the step of obtaining the voltage offset of the DC bus in the current state includes: The voltage offset is determined according to the proportional parameter, the integral parameter and the rated value of the DC bus voltage by using a fourth formula, wherein the fourth formula is: Among them, ΔU dc Indicates voltage offset, K p represents the scale parameter, T i represents the integral parameter, U dcn Indicates the rated value of DC bus voltage; The determining the third target power and the fourth target power according to the voltage offset includes: Substitute the voltage offset into the second formula to determine the third target power, and substitute the voltage offset into the third formula to determine the fourth target power.

2. The method according to claim 1, characterized in that: Also includes: After the first target power is adjusted to the third target power, the working state of the energy storage unit is judged, and if the working state of the energy storage unit is a preset state, the third target power is reduced to the preset power.

3. The method according to claim 2, characterized in that: Also includes: Obtaining the DC bus voltage duration, the second-order derivative preset threshold, the preset time threshold, the energy storage state of charge limit value of the energy storage unit at the third preset power, the change in the maximum discharge power and the maximum charging power of the energy storage unit, the real-time state of charge value of the energy storage unit at the third preset power, and the state of charge threshold of the energy storage unit at the third preset power; After the first target power is adjusted to the third target power, judging the working state of the energy storage unit, and if the working state of the energy storage unit is a preset state, reducing the third target power to the preset power, comprises: The working state of the energy storage unit is determined according to the DC bus voltage, the DC bus voltage duration, the second-order derivative preset threshold and the preset time threshold through a fifth formula, wherein the fifth formula is: Among them, U dc Indicates the DC bus voltage, d 2 U dc / dt 2 Indicates the second-order derivative of the DC bus voltage, C2 indicates the preset threshold of the second-order derivative, t indicates the duration of the second-order derivative of the DC bus voltage greater than 0, t delay Indicates the preset time threshold; In d 2 U dc / dt 2 >C2 and t>t delay , determining that the working state of the energy storage unit is a preset state; According to the energy storage state of charge limit value, the change in the maximum discharge power and the maximum charging power of the energy storage unit, the real-time state of charge value and the state of charge threshold, the third droop coefficient is determined by a sixth formula, wherein the sixth formula is: Among them, m soc represents the third droop coefficient, ΔP Bes_max Indicates the change in the maximum discharge power and maximum charging power of the energy storage unit, x SOC_max Indicates the energy storage state of charge limit, x SOCn represents the state of charge threshold, x SOC Indicates the real-time state of charge value; According to the third droop coefficient, the third preset power, the real-time state of charge value and the state of charge threshold, the third target power is reduced to the preset power through a seventh formula, wherein the seventh formula is: P Bes_refs2 =P es_refs1 -m soc (x SOC -x SOCn ); Among them, P es_refs2 Indicates preset power, P Bes_refs1 Indicates the third target power.

4. An island DC microgrid coordinated control device, characterized in that: include: A first acquisition module is used to acquire a DC bus voltage and a DC bus equivalent capacitance, and determine the unbalanced power of the island DC microgrid according to the DC bus voltage and the DC bus equivalent capacitance; A second acquisition module is used to switch the working mode of the energy storage unit to a preset mode if the unbalanced power meets the preset requirement, and control the energy storage unit to output the first target power, and control the photovoltaic system unit to output the second target power; A third acquisition module is used to take the energy storage unit in the first preset mode as the current state, and acquire the voltage offset of the DC bus in the current state, wherein the voltage offset represents the offset between the voltage value of the DC bus in the current state and the voltage value in the normal operating state; a fourth acquisition module, configured to determine a third target power and a fourth target power according to the voltage offset; an adjusting module, configured to adjust the first target power to the third target power, and adjust the second target power to the fourth target power; The first acquisition module includes: The first calculation module is used to determine the unbalanced power of the island DC microgrid according to the DC bus voltage and the DC bus equivalent capacitance through a first formula, wherein the first formula is: Where Δp represents the unbalanced power of the isolated DC microgrid, C f Indicates the DC bus equivalent capacitance, U dc Indicates the DC bus voltage, represents the derivative of the DC bus voltage; The second acquisition module includes: A fifth acquisition module, used to acquire the maximum charging and discharging power of the energy storage unit, the third output power of the energy storage unit under normal operating conditions, the first droop coefficient of the energy storage unit under the first preset mode, the fourth output power of the photovoltaic system unit in the tracking mode at maximum power, and the second droop coefficient of the photovoltaic system unit under the second preset mode; The second calculation module is used to determine the first target power through a second formula according to the unbalanced power, the DC bus equivalent capacitance, the maximum charging and discharging power of the energy storage unit, the third output power and the first droop coefficient, wherein the second formula is: Among them, P es_refs represents the first target power, P Besn Indicates the third output power, m Bes represents the first droop coefficient, P Bes_max Indicates the maximum charging and discharging power of the energy storage unit, ΔU dc Indicates voltage offset, C1 indicates preset value; According to the unbalanced power, the working mode of the energy storage unit is switched to a first preset mode, and the energy storage unit is controlled to output a first target power according to a second formula; The third calculation module is used to determine the second target power according to the unbalanced power, the fourth output power and the second droop coefficient by using a third formula, wherein the third formula is: Among them, P Pv_ref represents the second target power, P MPPT represents the fourth output power, m Pv represents the second droop coefficient, ΔU dc Indicates voltage offset; The third acquisition module includes: A sixth acquisition module, used for acquiring a proportional parameter, an integral parameter and a rated value of a DC bus voltage; The fourth calculation module is used to determine the voltage offset according to the proportional parameter, the integral parameter and the rated value of the DC bus voltage by using a fourth formula, wherein the fourth formula is: Among them, ΔU dc Indicates voltage offset, K p represents the scale parameter, T i represents the integral parameter, U dcn Indicates the rated value of DC bus voltage; The fourth acquisition module includes: Substitute the voltage offset into the second formula to determine the third target power, and substitute the voltage offset into the third formula to determine the fourth target power.

5. An electronic device comprising a memory, a processor, and a program stored in the memory and running on the processor, characterized in that: When the processor executes the program, the steps of the coordinated control method of the island DC microgrid as described in any one of claims 1 to 3 are implemented.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores instructions, and when the instructions are executed on a terminal device, the terminal device executes the steps of the coordinated control method for an island DC microgrid as described in any one of claims 1 to 3.

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