Method and device for determining working voltage of optical storage DC micro-grid, and storage medium

Abstract

The embodiment of the invention discloses a working voltage determination method and device of an optical storage DC micro-grid and a storage medium. The method comprises the following steps: reading the actual voltage of a common DC bus in the optical storage DC micro-grid; obtaining a first filtering voltage and a second filtering voltage of the actual voltage based on a low-pass filtering mode, wherein a first filtering parameter corresponding to the first filtering voltage is greater than a second filtering parameter corresponding to the second filtering voltage; determining a first filtering weight coefficient and a second filtering weight coefficient according to the first filtering voltage and the second filtering voltage; weighting the first filtering voltage and the second filtering voltage according to the first filtering weight coefficient and the second filtering weight coefficient to obtain working voltage; and according to the working voltage, enabling the optical storage DC micro-grid to operate in a corresponding working mode, wherein each working mode has the corresponding working voltage. By adopting the method, the technical problem that the working mode of the optical storage DC micro-grid is switched by mistake due to invalid fluctuation of the common DC bus voltage in the prior art can be solved.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of photovoltaic-storage DC microgrids, and in particular to a method, device, and storage medium for determining the operating voltage of a photovoltaic-storage DC microgrid. Background Art

[0002] With the increasing demand for new energy, the use of photovoltaic and storage DC microgrids in the field of solar power generation is becoming increasingly popular. Photovoltaic and storage DC microgrids can convert light energy into DC power for use by load devices. Based on the advantages of small footprint and few geographical constraints, the power generation of photovoltaic and storage DC microgrids can be improved. In addition, photovoltaic and storage DC microgrids have the characteristics of immediate use, so they are widely used in power supply scenarios such as residential buildings and shopping malls.

[0003] The photovoltaic DC microgrid usually adopts a voltage hierarchical control strategy, that is, the voltage in the public DC bus of the photovoltaic DC microgrid determines its own working mode. However, the voltage of the public DC bus will be affected by other factors (factors unrelated to the determination of the working mode) and aggravate the fluctuation. At this time, the aggravated fluctuation can be considered as invalid fluctuation. Invalid fluctuation may cause the working mode of the photovoltaic DC microgrid to switch incorrectly, thereby affecting the operating stability of the photovoltaic DC microgrid. Summary of the invention

[0004] The embodiments of the present application provide a method, device and storage medium for determining the working voltage of a photovoltaic-storage DC microgrid to solve the technical problem of incorrect switching of the working mode of a photovoltaic-storage DC microgrid caused by invalid fluctuations in the common DC bus voltage in the related art.

[0005] In a first aspect, an embodiment of the present application provides a method for determining an operating voltage of a photovoltaic-storage DC microgrid, the method comprising:

[0006] Read the actual voltage of the common DC bus in the photovoltaic and energy storage DC microgrid;

[0007] Based on the low-pass filtering method, a first filtered voltage and a second filtered voltage of the actual voltage are obtained respectively, the first filtered voltage corresponds to a first filtering parameter, the second filtered voltage corresponds to a second filtering parameter, and the first filtering parameter is greater than the second filtering parameter;

[0008] Determine a first filtering weight coefficient and a second filtering weight coefficient used this time according to the first filtering voltage and the second filtering voltage;

[0009] The first filtered voltage and the second filtered voltage are weighted according to the first filtering weight coefficient and the second filtering weight coefficient to obtain an operating voltage for determining an operating mode of a photovoltaic-storage DC microgrid;

[0010] The photovoltaic-storage DC microgrid operates in a corresponding working mode according to the working voltage, and each working mode has a corresponding working voltage.

[0011] In a second aspect, an embodiment of the present application further provides a device for determining the operating voltage of a photovoltaic-storage DC microgrid, the device comprising:

[0012] A voltage reading unit is used to read the actual voltage of the common DC bus in the photovoltaic and energy storage DC microgrid;

[0013] A low-pass filtering unit, used for obtaining a first filtered voltage and a second filtered voltage of the actual voltage respectively based on a low-pass filtering method, wherein the first filtered voltage corresponds to a first filtering parameter, the second filtered voltage corresponds to a second filtering parameter, and the first filtering parameter is greater than the second filtering parameter;

[0014] A weight determination unit, configured to determine a first filtering weight coefficient and a second filtering weight coefficient used this time according to the first filtering voltage and the second filtering voltage;

[0015] A voltage determination unit, configured to weight the first filtered voltage and the second filtered voltage according to the first filtering weight coefficient and the second filtering weight coefficient to obtain an operating voltage for determining an operating mode of a photovoltaic-storage DC microgrid;

[0016] The mode determination unit is used to make the photovoltaic and energy storage DC microgrid operate in a corresponding working mode according to the working voltage, and each working mode has a corresponding working voltage.

[0017] In a third aspect, an embodiment of the present application further provides a device for determining the operating voltage of a photovoltaic-storage DC microgrid, the device comprising: one or more processors;

[0018] When the one or more processors execute one or more programs stored in the memory, the one or more processors implement the operating voltage determination method as described in the first aspect.

[0019] In a fourth aspect, an embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for determining the operating voltage as described in the first aspect.

[0020] In one embodiment of the present application, by reading the actual voltage of the common DC bus in the photovoltaic storage DC microgrid, the first filter parameter and the second filter parameter are used to perform low-pass filtering on the actual voltage respectively to obtain the first filter voltage and the second filter voltage respectively, and then the first filter weight coefficient and the second filter weight coefficient used this time are determined according to the first filter voltage and the second filter voltage, and the first filter voltage and the second filter voltage are weighted according to the first filter weight coefficient and the second filter weight coefficient to obtain the working voltage of the determined working mode, so that the photovoltaic storage DC microgrid can operate the corresponding working mode according to the working voltage. The technical problem of the wrong switching of the working mode of the photovoltaic storage DC microgrid caused by the invalid fluctuation of the common DC bus voltage in the related technology is solved. By filtering the actual voltage using two filter parameters, the filter voltage focusing on the filtering effect and the dynamic performance can be obtained respectively, and then two appropriate filter weight coefficients are determined by combining the two filter voltages, and the working voltage considering both the filtering effect and the dynamic performance is obtained based on the filter weight coefficient, thereby suppressing the wrong switching of the working mode caused by the invalid fluctuation, and can quickly track the change of the voltage related to the switching working mode, and suppress the lag problem generated during low-pass filtering. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A flow chart of a method for determining the operating voltage of a photovoltaic-storage DC microgrid provided in one embodiment of the present application;

[0022] Figure 2 A flowchart of another method for determining the operating voltage of a photovoltaic-storage DC microgrid provided in one embodiment of the present application;

[0023] Figure 3 An example flow chart of a method for determining the operating voltage of a photovoltaic-storage DC microgrid provided in one embodiment of the present application;

[0024] Figure 4 A first signal simulation diagram provided for one embodiment of the present application;

[0025] Figure 5 A second signal simulation diagram provided for one embodiment of the present application;

[0026] Figure 6 A schematic diagram of the structure of a device for determining the working voltage of a photovoltaic-storage DC microgrid provided in one embodiment of the present application;

[0027] Figure 7 A schematic diagram of the structure of a device for determining the working voltage of a photovoltaic-storage DC microgrid provided in one embodiment of the present application;

[0028] Figure 8 A schematic diagram of the structure of a photovoltaic-storage DC microgrid provided for one embodiment of the present application. DETAILED DESCRIPTION

[0029] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are used to explain the present application, rather than to limit the present application. It should also be noted that, for ease of description, only the parts related to the present application, rather than all structures, are shown in the accompanying drawings.

[0030] A typical photovoltaic DC microgrid (hereinafter referred to as microgrid) includes a photovoltaic power generation device, an energy storage device, a grid-connected interface device and a constant power load. At this time, the photovoltaic power generation device, the energy storage device, the grid-connected interface device and the constant power load can all be considered as networking devices of the microgrid. Among them, the photovoltaic power generation device is used to generate electricity based on solar energy, that is, to generate electrical energy. The energy storage device is used to store the electrical energy generated by the photovoltaic power generation device. The grid-connected interface device is used to convert the electrical energy stored in the energy storage device into direct current suitable for constant power loads. The constant power load is a load device that absorbs energy (with constant power), that is, a load device that receives direct current. The constant power load is connected to the common DC bus of the microgrid. At this time, the common DC bus transmits direct current for the constant power load. The voltage of the common DC bus can be considered as the voltage for supplying power to the constant power load.

[0031] Microgrids usually adopt a voltage hierarchical control strategy, that is, the microgrid (which can also be understood as each networking device) determines the current working mode according to the voltage of the common DC bus. For example, the current working modes include the grid-connected interface device control mode and the energy storage device control mode. The voltage range corresponding to the grid-connected interface device control mode is 390V-410V, and the voltage range corresponding to the energy storage device control mode is 380V-390V and 410V-420V. When the current voltage of the common DC bus is within the voltage range of 390V-410V, the microgrid uses the grid-connected interface device control mode. When the current voltage of the common DC bus is within the voltage range of 380V-390V or the voltage range of 410V-420V, the microgrid uses the energy storage device control mode.

[0032] At present, due to the dynamic negative damping characteristics of the constant power load, the voltage of the common DC bus will fluctuate. Among them, the dynamic negative damping characteristics will cause the input impedance of the load device to decrease, which will reduce the system stability of the microgrid, and then cause the fluctuation of the common DC bus voltage to intensify. At this time, the fluctuation of the common DC bus voltage may cause the working mode of the microgrid (which can also be understood as each networking device) to switch frequently. At this time, even if there is no need to switch the working mode, the working mode will be switched incorrectly due to voltage fluctuations. Therefore, the voltage fluctuation caused by the dynamic negative damping characteristics can also be considered as invalid fluctuations that are unrelated to the switching working mode. At this time, each networking device may mistakenly change the working mode due to invalid fluctuations. For example, the microgrid is currently in the grid-connected interface device control mode, but because the dynamic negative damping characteristics cause voltage fluctuations, the microgrid switches to the energy storage device control mode based on the fluctuating voltage, and switches back to the grid-connected interface device control mode as the fluctuation ends, which affects the system stability of the microgrid. It can be understood that in addition to the invalid fluctuations caused by the dynamic negative damping characteristics, other factors may also cause invalid fluctuations.

[0033] Therefore, how to prevent the microgrid from incorrectly changing its working mode due to invalid fluctuations has become a technical problem that needs to be solved urgently.

[0034] In the related art, in order to ensure smooth switching of the working mode and avoid erroneous switching, the voltage signal of the common DC bus can be processed by a low-pass filtering method or a hysteresis comparison method, and then the switching of the working mode is controlled based on the processed voltage signal to avoid erroneous switching of the working mode caused by voltage fluctuations, thereby improving the system stability of the microgrid.

[0035] The low-pass filtering method refers to filtering the voltage signal in the common DC bus through a low-pass filter to suppress the voltage fluctuation in the voltage signal, thereby avoiding frequent switching of the working mode. Among them, the low-pass filter is an electronic filtering device that allows signals below the cut-off frequency to pass, but signals above the cut-off frequency cannot pass. After setting appropriate filtering parameters for the low-pass filter, the waveform with higher frequency in the voltage signal can be suppressed, thereby suppressing voltage fluctuations. In this way, although voltage fluctuations can be suppressed, it is only applicable to the steady-state situation of the microgrid. In the dynamic situation of the microgrid, for example, when the voltage of the common DC bus changes from the voltage of one working mode to the voltage of another working mode, since the low-pass filtering method uses fixed filtering parameters, the low-pass filtering method causes a serious lag effect on the voltage signal, thereby affecting the dynamic performance of the microgrid. Generally speaking, the change in the voltage value of the common DC bus in the steady state is significantly smaller than the change in the voltage value of the common DC bus in the dynamic situation.

[0036] The hysteresis comparison method refers to presetting a hysteresis interval, which can also be recorded as an insensitive interval, indicating the range of voltage fluctuation allowed when the working mode is not switched. When the voltage fluctuation range of the common DC bus is within the hysteresis interval, the microgrid does not switch the working mode. When the voltage fluctuation range of the common DC bus exceeds the hysteresis interval, the microgrid switches to the corresponding functional mode according to the current voltage of the common DC bus. The hysteresis comparison method can reduce the sensitivity of the microgrid to smaller voltage fluctuations based on the hysteresis interval, and can respond quickly to larger voltage fluctuations. However, when the power of the load device increases, causing the voltage fluctuation to increase, the voltage fluctuation range may exceed the hysteresis interval, which will make the hysteresis comparison method invalid. In addition, under the hysteresis comparison method, it is difficult to select a suitable voltage range width (also recorded as hysteresis width) for the hysteresis interval.

[0037] Based on this, a method for determining the working voltage of a photovoltaic DC microgrid is provided in an embodiment of the present application. The method for determining the working voltage is based on the use of a low-pass filtering method, and the voltage signal in the common DC bus is filtered using filtering parameters suitable for steady-state conditions and dynamic conditions respectively. Thereafter, an appropriate weight coefficient is determined by combining the filter signals obtained by combining the two filtering parameters, and the two filtered signals are weighted in combination with the weight coefficient to obtain a final filtered value. The filtered value can reflect the working voltage related to the working mode in the voltage signal of the common DC bus, thereby enabling the photovoltaic DC microgrid to set an accurate working mode according to the working voltage, avoiding the technical problem of erroneous change of the working mode due to invalid voltage fluctuations, and overcoming the problem of severe signal lag in the dynamic state of the low-pass filtering method, thereby improving the stability of the photovoltaic DC microgrid.

[0038] The method for determining the working voltage of a photovoltaic DC microgrid with storage can be performed by a working voltage determination device of the photovoltaic DC microgrid with storage. The working voltage determination device can be composed of one physical entity or multiple physical entities. Currently, the working voltage determination device is a device with data signal processing and analysis functions. In one embodiment, when any networking device in the photovoltaic DC microgrid has data signal processing and analysis functions, it can be used as the currently used working voltage determination device, that is, the working voltage determination device is integrated in the networking device of the photovoltaic DC microgrid with storage. In actual applications, the working voltage determination device can also use other devices independent of each networking device. At this time, the working voltage determination device can be connected to the photovoltaic DC microgrid to determine the working voltage that controls the working mode of the photovoltaic DC microgrid.

[0039] Figure 1 A flowchart of a method for determining the working voltage of a photovoltaic-storage DC microgrid provided in one embodiment of the present application. Figure 1 The working voltage determination method includes steps 110 to 150:

[0040] Step 110: Read the actual voltage of the common DC bus in the photovoltaic and energy storage DC microgrid.

[0041] Exemplarily, the working voltage determination device reads the voltage signal of the common DC bus at a preset frequency. The voltage signal represents a sampled value of the voltage of the common DC bus. Currently, the voltage signal read from the common DC bus is an unfiltered voltage signal, which can represent the actual current voltage value of the common DC bus. In an embodiment, the voltage signal in the common DC bus currently read is recorded as the actual voltage. The actual voltage may include fluctuations in the voltage on the common DC bus.

[0042] The method for reading the actual voltage is not currently limited. For example, a sampling program is pre-stored in the working voltage determination device, and the actual voltage can be read from the common DC bus through the sampling program. Optionally, the working voltage determination device can be directly connected to the common DC bus, or indirectly connected to the common DC bus through other devices or circuits. In this case, the sampling program can drive other devices or circuits to read the actual voltage from the common DC bus.

[0043] Step 120 , obtaining a first filtered voltage and a second filtered voltage of the actual voltage respectively based on a low-pass filtering method, wherein the first filtered voltage corresponds to a first filtering parameter, the second filtered voltage corresponds to a second filtering parameter, and the first filtering parameter is greater than the second filtering parameter.

[0044] The low-pass filtering method is implemented by a low-pass filter. In one embodiment, the low-pass filter is implemented by a program. In this case, the working voltage determination device pre-stores an implementation program of the low-pass filter, and the function of the low-pass filter can be realized by running the implementation program.

[0045] In one embodiment, when filtering the actual voltage based on the low-pass filtering method, two low-pass filters are used, and the two low-pass filters have different filtering parameters. The filtering parameter refers to the parameter used in the operation of the low-pass filter. During the operation of the low-pass filter, the filtering effect can be enhanced as the filtering parameter increases. The larger the filtering parameter, the smoother the waveform obtained after filtering. Currently, the filtering parameters used by the two low-pass filters are respectively recorded as the first filtering parameter and the second filtering parameter.

[0046] Exemplarily, the values ​​of the first filter parameter and the second filter parameter are different, so that the two low-pass filters focus on filtering effect and dynamic performance respectively. When focusing on filtering effect, the waveform after filtering is as smooth as possible and the voltage fluctuation is small, so as to achieve effective suppression of voltage fluctuation. When focusing on dynamic performance (i.e., rapid tracking of dynamic changes in voltage), the waveform after filtering still has a certain voltage fluctuation. At this time, it can be guaranteed that the photovoltaic storage DC microgrid can provide timely feedback on voltage changes under dynamic conditions, that is, quickly switch the working mode. In one embodiment, the first filter parameter is greater than the second filter parameter, that is, the low-pass filter using the first filter parameter focuses on filtering effect, and the low-pass filter using the second filter parameter focuses on dynamic performance. The values ​​of the first filter parameter and the second filter parameter can be set according to actual conditions to ensure that a waveform that guarantees the filtering effect and a waveform that retains a certain voltage fluctuation are obtained respectively. At present, the first filter parameter is expressed as j L , and j L =0.98 as an example, the second filtering parameter is expressed as j H , and j H =0.7 as an example. Among them, j L =0.98, the voltage fluctuation can be effectively suppressed, but the voltage fluctuation related to the change of working mode cannot be tracked immediately, so more emphasis is placed on the filtering effect. H When =0.7, the voltage fluctuation is retained to a certain extent, and the erroneous switching of the working mode cannot be avoided. However, the voltage fluctuation that changes the working mode can be identified, so more emphasis is placed on dynamic performance.

[0047] In one embodiment, each time the actual voltage is read, the actual voltage is input into two low-pass filters for low-pass filtering to obtain two filtered signals. At present, the filtered signal output after the actual voltage is low-pass filtered based on the first filtering parameter is recorded as the first filtered voltage, and the filtered signal output after the actual voltage is low-pass filtered based on the second filtering parameter is recorded as the second filtered voltage. The voltage fluctuation in the first filtered voltage is smaller than the voltage fluctuation in the second filtered voltage. At this time, the fluctuation of the first filtered voltage is smaller and has a better filtering effect. The second filtered voltage retains the fluctuation of the actual voltage and has a better effect of fast tracking of the dynamic change of the voltage.

[0048] Now, let the first filtered voltage be v dcL , the second filtered voltage is recorded as v dcH .v dcL and v dcH The calculation formula is as follows:

[0049] v dcL =j L ·v dcL +(1-j L )·vdc (1)

[0050] v dcH =j H ·v dcH +(1-j H )·v dc (2)

[0051] Among them, v dc Indicates the actual voltage currently read. Use the low-pass filter with the first filter parameter corresponding to formula (1), and get v through formula (1) dcL The low-pass filter with the second filter parameter corresponds to formula (2), and v is obtained by formula (2) dcH .

[0052] Step 130: Determine a first filtering weight coefficient and a second filtering weight coefficient used this time according to the first filtering voltage and the second filtering voltage.

[0053] Exemplarily, the filter weight coefficient reflects the weight of the first filter voltage and the second filter voltage in weighted aggregation. For example, if the current focus is on the filtering effect, then a higher filter weight coefficient can be set for the first filter voltage, and a lower filter weight coefficient can be set for the second filter voltage, so as to increase the proportion of the first filter voltage in the final result during weighted aggregation. If the current focus is on dynamic performance, that is, focusing on the rapid tracking of dynamic changes in voltage, then a higher filter weight coefficient can be set for the second filter voltage, and a lower weight filter coefficient can be set for the first filter voltage, so as to increase the proportion of the second filter voltage in the final result during weighted aggregation.

[0054] It can be understood that the first filtered voltage and the second filtered voltage are filtered signals obtained based on the same actual voltage. At this time, if the fluctuation degree of the actual voltage is large, the fluctuation degree of the second filtered voltage will be significantly greater than the fluctuation degree of the first filtered voltage. If the fluctuation degree of the actual voltage is not very large, the fluctuation degree of the second filtered voltage is not much different from the fluctuation degree of the first filtered voltage. Therefore, based on the difference between the first filtered voltage and the second filtered voltage, it can be determined whether the fluctuation degree of the actual voltage (which can reflect the change in voltage value) is large. When the working mode is switched, the value of the actual voltage of the common DC bus needs to change significantly. At this time, the fluctuation of the actual voltage caused is larger and significantly greater than the invalid fluctuation (the change in the value of the actual voltage of the common DC bus under invalid fluctuation is not obvious). Based on this, if the fluctuation degree of the actual voltage is large (that is, the voltage value changes significantly), it means that it should be considered whether the fluctuation of the actual voltage is the fluctuation when the working mode is switched, that is, the dynamic performance needs to be enhanced. If the fluctuation degree of the actual voltage is small (that is, the voltage value does not change significantly), it means that the voltage fluctuation of the actual voltage is likely to be invalid fluctuation, that is, the filtering effect needs to be enhanced. Therefore, reasonable filtering weight coefficients may be set for the first filtered voltage and the second filtered voltage based on the degree of difference between the first filtered voltage and the second filtered voltage.

[0055] In one embodiment, after reading the actual voltage this time, the filter weight coefficient that should be used for the first filter voltage is recorded as the first filter weight coefficient, and the filter weight coefficient that should be used for the second filter voltage is recorded as the second filter weight coefficient. Currently, the value ranges of the first filter weight coefficient and the second filter weight coefficient are both greater than or equal to 0 and less than or equal to 1, and the sum of the two filter weight coefficients is 1, so after determining one of the filter weight coefficients, the other filter weight coefficient can be obtained. In the embodiment, since the second filter voltage focuses on dynamic performance, which is related to the switching of the working mode, the process of determining the filter weight coefficient used by the second filter voltage is currently described as an example.

[0056] At present, if the difference between the first filter voltage and the second filter voltage is small, it means that the voltage fluctuation in the common DC bus is small, and the probability of the fluctuation generated when the working mode is switched is very small. At this time, the second filter weight coefficient can be set to a very small value, such as 0, then the first filter weight coefficient can be set to 1. If the difference between the first filter voltage and the second filter voltage is large, it means that the voltage fluctuation in the common DC bus is a large probability of the fluctuation generated when the working mode is switched. At this time, the second filter weight coefficient can be set in combination with the first filter voltage and the second filter voltage, and the greater the difference between the first filter voltage and the second filter voltage, the greater the second filter weight coefficient, so as to ensure that the final filter value better reflects the change in voltage. After that, the first filter weight coefficient can be determined based on the second filter weight coefficient. Optionally, the coefficient values ​​corresponding to different degrees of difference can be pre-set, and then, according to the pre-set corresponding relationship, the coefficient value corresponding to the degree of difference between the first filter voltage and the second filter voltage can be determined, and the coefficient value is used as the second filter weight coefficient. Alternatively, a calculation formula for the degree of difference and the coefficient value is pre-set, and the calculation formula can be set in combination with the voltage fluctuation of the common DC bus when each working mode is switched. After substituting the degree of difference between the first filter voltage and the second filter voltage into the calculation formula, the second filter weight coefficient can be determined.

[0057] In practical applications, the first filter weight coefficient and the second filter weight coefficient may also be determined in other ways, which are not limited by the embodiment comparison. For example, the coefficient values ​​of the first filter weight coefficient and the second filter weight coefficient under different degrees of difference between the first filter voltage and the second filter voltage are pre-set, and then the first filter weight coefficient and the second filter weight coefficient used this time can be determined according to the corresponding relationship.

[0058] Step 140: weight the first filtered voltage and the second filtered voltage according to the first filtering weight coefficient and the second filtering weight coefficient to obtain an operating voltage for determining an operating mode of the photovoltaic-storage DC microgrid.

[0059] After weighting the first filter voltage and the second filter voltage according to the first filter weight coefficient and the second filter weight coefficient, the obtained filter value can be considered as a voltage signal obtained on the basis of comprehensive filtering effect and dynamic performance, and the voltage signal more accurately reflects the voltage value that determines the working mode on the public DC bus at the current moment during the operation of the photovoltaic storage DC microgrid. In the embodiment, the voltage signal obtained after weighting is recorded as the working voltage. The working voltage can be considered as a voltage signal obtained after suppressing the invalid fluctuation of the actual voltage of the public DC bus and effectively retaining the voltage fluctuation caused by the switching of the working mode, that is, the working voltage is used when the photovoltaic storage DC microgrid adopts the voltage stratification control strategy.

[0060] When weighting, a first filter weight coefficient is used for the first filter voltage, and a second filter weight coefficient is used for the second filter voltage. Afterwards, the two filter voltages using the filter weight coefficients are added together to achieve weighted aggregation and obtain the working voltage.

[0061] Step 150: operate the photovoltaic-storage DC microgrid in a corresponding operating mode according to the operating voltage, and each operating mode has a corresponding operating voltage.

[0062] At present, each working mode has a corresponding working voltage, which can also be understood as each working mode has a corresponding working voltage range. After obtaining the working voltage of the common DC bus, each networking device of the photovoltaic storage DC microgrid can determine which working mode's working voltage range the working voltage belongs to, and then determine the working mode that needs to be run at present. If it is determined that the working mode needs to be switched according to the working voltage, the networking device can switch the working mode.

[0063] It can be understood that each time the actual voltage is read, the corresponding operating voltage can be obtained, and the corresponding operating mode can be determined based on the operating voltage.

[0064] In the above, by reading the actual voltage of the common DC bus in the photovoltaic storage DC microgrid, the actual voltage is low-pass filtered using the first filter parameter and the second filter parameter respectively to obtain the first filter voltage and the second filter voltage respectively, and then the first filter weight coefficient and the second filter weight coefficient used this time are determined according to the first filter voltage and the second filter voltage, and the first filter voltage and the second filter voltage are weighted according to the first filter weight coefficient and the second filter weight coefficient to obtain the working voltage of the determined working mode, and then the photovoltaic storage DC microgrid can be operated according to the working voltage. The technical means of the corresponding working mode solves the technical problem of the wrong switching of the working mode of the photovoltaic storage DC microgrid caused by the invalid fluctuation of the common DC bus voltage in the related technology. By filtering the actual voltage using two filter parameters, the filter voltage focusing on the filtering effect and the dynamic performance can be obtained respectively, and then two appropriate filter weight coefficients are determined by combining the two filter voltages, and the working voltage considering both the filtering effect and the dynamic performance is obtained based on the filter weight coefficient, thereby suppressing the wrong switching of the working mode caused by the invalid fluctuation, and can quickly track the change of the voltage related to the switching working mode, and suppress the lag problem generated during low-pass filtering.

[0065] Figure 2 A flowchart of another method for determining the operating voltage of a photovoltaic-storage DC microgrid provided in an embodiment of the present application. Figure 2 The method shown is in Figure 1 The method shown in FIG. 1 is used to exemplarily describe how to obtain the filtering weight coefficient and how to perform weighting. Figure 2, the working voltage determination method includes steps 210 to 2100.

[0066] Step 210: Read the actual voltage of the common DC bus in the photovoltaic and energy-storage DC microgrid.

[0067] Step 220: Obtain a first filtered voltage and a second filtered voltage of the actual voltage based on a low-pass filtering method, wherein the first filtered voltage corresponds to a first filtering parameter, the second filtered voltage corresponds to a second filtering parameter, and the first filtering parameter is greater than the second filtering parameter.

[0068] Currently, the first filter parameter is denoted as j L , the second filter parameter is represented as j H , the first filtered voltage is represented as v dcL , the second filtered voltage is recorded as v dcH Among them, j L =0.98,j H =0.7.

[0069] Step 230: Calculate a first voltage difference between the first filtered voltage and the second filtered voltage.

[0070] After that, calculate v dcL and v dcH The difference is currently recorded as the first voltage difference. The first voltage difference is represented by v abs .v abs =v dcL -v dcH .v dcL and v dcH It is the filtered voltage obtained by low-pass filtering the same actual voltage using two filtering parameters. Therefore, based on v dcL and v dcH The obtained v abs It can reflect the actual voltage fluctuation.

[0071] When the actual voltage fluctuation is small (i.e., the voltage value changes little), it can be considered that the actual voltage is in the steady-state range. In the steady-state range, the working modes of the networking devices in the photovoltaic DC microgrid do not switch. At this time, when the actual voltage is low-pass filtered using different filtering parameters, the difference between the obtained filtered voltages is small, i.e., v abs The absolute value of is relatively small. When the actual voltage fluctuates greatly (i.e., the voltage value changes greatly), it can be considered that the actual voltage is in a dynamic range. In the dynamic range, the working modes of various networking devices in the photovoltaic storage DC microgrid generally switch. At this time, when using different filtering parameters to perform low-pass filtering on the actual voltage, the fluctuation degree of the filtering voltage focusing on dynamic performance is significantly different from that of the filtering voltage focusing on filtering effect, i.e., v abs The absolute value of is relatively large.

[0072] Step 240: Determine a second filtering weight coefficient used this time according to the first voltage difference, where the second filtering weight coefficient corresponds to a second filtering voltage.

[0073] When the working mode is switched, the fluctuation of the actual voltage in the common DC bus is more obvious, that is, the fluctuation degree of the actual voltage is greater than the degree of invalid fluctuation when the working mode is switched. Therefore, after obtaining the first voltage difference, if the absolute value of the first voltage difference is small, it means that the fluctuation of the actual voltage is not obvious. The fluctuation at this time is more likely to be caused by the dynamic negative damping characteristics of the constant power load (that is, invalid fluctuation). Then, it can be considered that the current actual voltage is in the voltage stabilization range and the working mode switching does not occur. At this time, when calculating the working voltage, the first filter voltage should be considered as the focus, that is, the second filter weight coefficient should be very small to avoid the influence of the second filter voltage on the static working voltage. If the absolute value of the first voltage difference is large, it means that the actual voltage fluctuates significantly. At this time, the fluctuation is more likely to be caused by the need to switch the working mode. Therefore, it can be considered that the current actual voltage is in a dynamic range, and it is very likely that the working mode needs to be switched. At this time, when calculating the working voltage, the second filtered voltage should be considered as the priority, that is, the second filtering weight coefficient should be large, so as to reflect the voltage fluctuation when switching the working mode in the working voltage as much as possible. In addition, the larger the absolute value of the first voltage difference, the greater the fluctuation of the actual voltage, and the higher the possibility of switching the working mode. The larger the second filtering weight coefficient should be, so as to ensure that the working voltage is as close to the second filtered voltage as possible, that is, there is obvious voltage fluctuation in the working voltage.

[0074] In one embodiment, when determining the second filtering weight coefficient, a preset voltage fluctuation threshold may be introduced to determine whether the actual voltage is in a static range or a dynamic range, thereby determining a suitable second filtering weight coefficient. At this time, step 240 includes steps 241 to 243:

[0075] Step 241, determine whether the absolute value of the first voltage difference is greater than a preset voltage fluctuation threshold. If it is greater than the voltage fluctuation threshold, execute step 242. If it is less than or equal to the voltage fluctuation threshold, execute step 243.

[0076] The voltage fluctuation threshold is a preset value. The voltage fluctuation threshold can also be considered as the maximum difference between the first filter voltage and the second filter voltage in the steady-state interval, that is, the maximum value that the absolute value of the first voltage difference can reach in the steady-state interval. The voltage fluctuation threshold can be set according to actual conditions. At present, the voltage fluctuation threshold is recorded as a, and a is a positive number.

[0077] After the voltage fluctuation threshold is preset, it can be used directly in this step.

[0078] Exemplarily, after the first voltage difference is calculated, the absolute value of the first voltage difference is compared with the voltage fluctuation threshold. It should be noted that there is a case where the first voltage difference is negative. At this time, although the first voltage difference is negative, the larger the negative value, the more obvious the difference between the first filter voltage and the second filter voltage, that is, the greater the possibility that the actual voltage is in the dynamic interval. Therefore, in order to avoid the influence of negative values ​​on the identification of dynamic intervals and steady-state intervals, it is necessary to compare the absolute value of the first voltage difference with the voltage fluctuation threshold. In one embodiment, when comparing, it is specifically to determine whether the first voltage difference is less than or equal to the voltage fluctuation threshold. If it is less than or equal to the voltage fluctuation threshold, it means that the difference between the first filter voltage and the second filter voltage is small, that is, the actual voltage fluctuation is small. At this time, it can be considered that the first voltage difference is in the steady-state range, and the steady-state range corresponds to the steady-state range. In the steady-state range, the amplitude of the actual voltage fluctuation is within the voltage fluctuation range allowed when the working mode is not switched. At this time, it is necessary to strengthen the suppression effect of voltage fluctuations, that is, it is necessary to pay more attention to the filtering effect. Therefore, step 243 is executed. If the first voltage difference is greater than the voltage fluctuation threshold, it means that the first filtered voltage and the second filtered voltage have a large difference, that is, the actual voltage fluctuates greatly. At this time, it can be considered that the first voltage difference is in a dynamic range, and the dynamic range corresponds to a dynamic interval, indicating that the actual voltage is changing rapidly and may need to switch the working mode. At this time, it is necessary to strengthen the rapid tracking of voltage fluctuations, that is, it is necessary to pay more attention to dynamic effects. Therefore, step 242 is executed.

[0079] It should be noted that in actual applications, in addition to setting the voltage fluctuation threshold, the voltage fluctuation range can also be set. The voltage fluctuation range can be a range from negative to positive numbers. For example, the voltage fluctuation threshold and the negative of the voltage fluctuation threshold are respectively used as two boundary values ​​of the voltage fluctuation range. If the first voltage difference is within the voltage fluctuation range, it means that the first voltage difference is in the static range. If the first voltage difference exceeds the voltage fluctuation range, it means that the first voltage difference is in the dynamic range.

[0080] Step 242: Determine a second filtering weight coefficient used this time according to the first voltage difference and the voltage fluctuation threshold.

[0081] When the first voltage difference is greater than the voltage fluctuation threshold, if the difference between the voltage fluctuation threshold is greater, it means that the actual voltage fluctuation is greater, and the corresponding second filtering weight coefficient should be greater. Therefore, the second filtering weight coefficient can be determined according to the difference between the first voltage difference and the voltage fluctuation threshold. Optionally, the second filtering weight coefficient corresponding to each first voltage difference can be pre-set, or the conversion relationship between each first voltage difference and the filtering weight coefficient can be set, and the second filtering weight coefficient can be determined according to the conversion relationship. Regardless of which method is adopted, it is necessary to satisfy the relationship that the greater the difference, the greater the second filtering weight coefficient. In one embodiment, the second filtering weight coefficient used this time is determined according to the conversion relationship between the first voltage difference and the filtering weight coefficient. At this time, step 242 may specifically include: if it is greater than the voltage fluctuation threshold, the absolute value of the first voltage difference and the second voltage difference of the voltage fluctuation threshold are calculated; the square of the product of the second voltage difference and the preset coefficient is used as the second filtering weight coefficient used this time.

[0082] When determining the second filtering weight coefficient, the difference between the absolute value of the first voltage difference and the voltage fluctuation threshold is first calculated, and the difference is currently recorded as the second voltage difference. It can be understood that when the first voltage difference is greater than the voltage fluctuation threshold, when the voltage fluctuation threshold is fixed, the larger the second voltage difference is, the larger the actual voltage fluctuation is.

[0083] After calculating the second voltage difference, multiply the second voltage difference by the preset coefficient. Among them, the preset coefficient can be selected according to the range of the first voltage difference in actual application. The goal of setting the preset coefficient is to make the second filter weight coefficient finally calculated be within the preset weight coefficient value range (the current weight coefficient value range is [0,1]). Generally speaking, when the range of the first voltage difference is between 10V-20V, after the preset coefficient is selected as 0.1, it can be ensured that the calculated second filter weight coefficient is between 0-1. After squaring the product of the second voltage difference and the preset coefficient, the second filter weight coefficient can be obtained. In one embodiment, the calculation formula of the second filter weight coefficient is:

[0084] kx=[(|v abs |-a)·b] 2 (3)

[0086] Wherein, kx represents the second filtering weight coefficient, and b represents the preset coefficient.

[0087] Step 243: Determine the second filtering weight coefficient to be 0.

[0088] When the first voltage difference is less than or equal to the voltage fluctuation threshold, it means that the actual voltage fluctuation is small. At this time, the fluctuation amplitude of the actual voltage is within the voltage fluctuation range allowed when the working mode is not switched. At this time, the second filtering weight coefficient is set to 0, so that the final working voltage only considers the filtering effect, without considering the voltage fluctuation that occurs when the working mode is switched.

[0089] In one embodiment, the second filter weight coefficient should be between [0, 1]. At this time, in order to ensure that the second filter weight coefficient is between [0, 1], after obtaining the second filter weight coefficient, the second filter weight coefficient is also limited. At this time, after step 240, it can also include: limiting the second filter weight coefficient so that the second filter weight coefficient is within the preset weight coefficient value range.

[0090] The weight coefficient value range refers to the range of the coefficient value of the second filter weight coefficient. Currently, the weight coefficient value range is [0,1]. In practical applications, other weight coefficient value ranges can also be set. The purpose of the limit processing is to make the second filter weight coefficient fall within the weight coefficient value range to avoid the situation in which the second filter weight coefficient exceeds the weight coefficient value range, making the final calculated working voltage inaccurate.

[0091] The process of the amplitude limiting process may be that if the second filter weight coefficient is within the weight coefficient value range, the second filter weight coefficient is not processed. If the second filter weight coefficient is less than the weight coefficient value range, the second filter weight coefficient is modified to the minimum value (such as 0) in the weight coefficient value range. If the second filter weight coefficient is greater than the weight coefficient value range, the second filter weight coefficient is modified to the maximum value (such as 1) in the weight coefficient value range.

[0092] In practical applications, the amplitude limiting process may also be implemented in other ways, which are not currently limited. In practical applications, the amplitude limiting may also be performed only on the second filtering weight coefficient calculated when the value is greater than the voltage fluctuation threshold.

[0093] Step 250, compare the second filter weight coefficient with the third filter weight coefficient, the third filter weight coefficient is equal to the filter weight coefficient used by the second filter voltage determined last time. If the third filter weight coefficient is greater than the second filter weight coefficient, execute step 260. If the third filter weight coefficient is greater than, less than or equal to the second filter weight coefficient 270.

[0094] In one embodiment, each time the real-time voltage is collected, the corresponding filter weight coefficient (such as the second filter weight coefficient and the first filter weight coefficient) is calculated to obtain the corresponding working voltage. At this time, the obtained filter weight coefficient will change with the change of the collected real-time voltage. In one embodiment, in order to avoid instability in the photovoltaic DC microgrid due to the change of the filter weight coefficient, an intermediate variable of the weight coefficient is introduced, which is currently recorded as the third filter weight coefficient. The third filter weight coefficient can be considered as an intermediate variable used in the process of changing the filter weight coefficient.

[0095] Exemplarily, after reading the real-time voltage and calculating the second filter weight coefficient, the third filter weight coefficient used may be the filter weight coefficient used for the second filter voltage when calculating the working voltage last time, so as to avoid the instability of the photovoltaic storage DC microgrid caused by the change of the filter weight coefficient used when calculating the working voltage twice. It should be noted that for the first time reading the real-time voltage, the third filter weight coefficient used may be a preset value, for example, the preset value is 0, then when the real-time voltage is first collected, the third filter weight coefficient introduced is 0.

[0096] After obtaining the second filter weight coefficient, obtain the third filter weight coefficient, and then compare the second filter weight coefficient and the third filter weight coefficient. In one embodiment, when comparing, it is specifically to determine whether the third filter weight coefficient is greater than the second filter weight coefficient. Based on the above content, it can be seen that the larger the first voltage difference, the larger the corresponding second filter weight coefficient. Then, if the third filter weight coefficient is greater than the second filter weight coefficient, it means that the fluctuation of the real-time voltage read last time is greater than the fluctuation of the real-time voltage read this time, that is, the working mode should not be switched under this reading, and the real-time voltage may be converted from the dynamic interval to the steady-state interval. Therefore, the filter weight coefficient used for the second filter voltage does not need to change too fast. At this time, the filter weight coefficient can be allowed to change slowly to pursue the stability of the photovoltaic storage DC microgrid. At this time, step 260 is executed. If the third filter weight coefficient is less than the second filter weight coefficient, it means that the fluctuation of the real-time voltage read last time is less than the fluctuation of the real-time voltage read this time, that is, the working mode may be switched under this reading, and the real-time voltage may be converted from the steady-state interval to the dynamic interval. Therefore, it is necessary to quickly adjust the filter weight coefficient, that is, quickly confirm the working voltage. At this time, step 270 is executed.

[0097] Step 260: If the third filter weight coefficient is greater than the second filter weight coefficient, the third filter weight coefficient is gradually reduced according to a preset coefficient adjustment value until the third filter weight coefficient is equal to the second filter weight coefficient. Execute step 280.

[0098] Exemplarily, when the third filter weight coefficient is greater than the second filter weight coefficient, the filter weight coefficient used last time (currently the third filter weight coefficient) is adjusted successively, so that the filter weight coefficient used last time (currently the third filter weight coefficient) gradually changes to the filter weight coefficient to be used this time (currently the second filter weight coefficient) through successive adjustments, so as to avoid the second filter weight coefficient changing too fast. It should be noted that, in general, when the filter weight coefficient changes, the working voltage also changes. At this time, the change of the filter weight coefficient may cause a large mutation in the working voltage, and a large mutation in the working voltage may cause the photovoltaic storage DC microgrid to be unstable. Therefore, when the third filter weight coefficient gradually changes to the second filter weight coefficient, the second filter weight coefficient is used to determine the working voltage, so that the filter weight coefficient can change slowly. At this time, the working voltage will not change too fast (that is, the working voltage calculation slows down), so as to pursue the stability of the photovoltaic storage DC microgrid.

[0099] In one embodiment, when the third filter weight coefficient is adjusted successively, the third filter weight coefficient is specifically reduced successively using a preset coefficient adjustment value. Among them, the coefficient adjustment value can also be understood as the amplitude when the filter weight coefficient is adjusted each time. The coefficient adjustment value can be set in combination with actual needs. The larger the coefficient adjustment value, the faster the filter weight coefficient is adjusted, and the smaller the coefficient adjustment value, the smoother the filter weight coefficient is adjusted. Each time the third filter weight coefficient is adjusted according to the coefficient adjustment value, the adjusted third filter weight coefficient is compared with the second filter weight coefficient again. If the adjusted third filter weight coefficient is still greater than the second filter weight coefficient, the coefficient adjustment value is continued to be used for adjustment until the third filter weight coefficient is equal to the second filter weight coefficient. It should be noted that if the third filter weight coefficient after a certain adjustment is less than the second filter weight coefficient, the third filter weight coefficient is adjusted to be equal to the second filter weight coefficient.

[0100] When the third filter weight coefficient after successive reduction is equal to the second filter weight coefficient, the adjusted third filter weight coefficient can be used as the second filter weight coefficient used this time. At this time, the second filter weight coefficient is still used in the subsequent weighted calculation, but the successive reduction process is added.

[0101] Step 270 : If the third filter weight coefficient is less than or equal to the second filter weight coefficient, the third filter weight coefficient is directly adjusted to the second filter weight coefficient. Execute step 280 .

[0102] Exemplarily, when the third filter weight coefficient is equal to the second filter weight coefficient, the third filter weight coefficient may not be adjusted, and the third filter weight coefficient may be used as the second filter weight coefficient used this time. In this case, the second filter weight coefficient is still used in subsequent weighted calculations.

[0103] Exemplarily, when the third filter weight coefficient is less than the second filter weight coefficient, it is necessary to quickly adjust the filter weight coefficient used last time (currently the third filter weight coefficient) to the filter weight coefficient to be used this time (currently the second filter weight coefficient) to ensure that the current operating voltage is quickly determined, that is, timely tracking of real-time voltage changes, and then accurately adjusting the switching working mode. After the third filter weight coefficient is directly adjusted to the second filter weight coefficient, the adjusted third filter weight coefficient can be used as the second filter weight coefficient used this time. At this time, the subsequent weighted calculation still uses the second filter weight coefficient, but the direct reduction process is added.

[0104] Step 280: Use the difference between the preset weight coefficient and the second filtering weight coefficient as the first filtering weight coefficient of the first filtering voltage.

[0105] The weight coefficient and value can be understood as the sum of the first filter weight coefficient and the second filter weight coefficient. The weight coefficient and value can be set according to the actual situation. Currently, the weight coefficient and value are described as 1, that is, the sum of the first filter weight coefficient and the second filter weight coefficient is equal to 1.

[0106] After the second filtering weight coefficient is obtained, the preset weight coefficient sum value and the second filtering weight coefficient may be subtracted, and the obtained difference may be used as the first filtering weight coefficient of the first filtering voltage.

[0107] Step 290: weight the first filtered voltage and the second filtered voltage according to the first filtering weight coefficient and the second filtering weight coefficient to obtain an operating voltage for determining an operating mode of the photovoltaic-storage DC microgrid.

[0108] Step 290 may specifically include: multiplying the first filtered voltage by the first filtering weight coefficient to obtain a first multiplication result, and multiplying the second filtered voltage by the second filtering weight coefficient to obtain a second multiplication result; and using the sum of the first multiplication result and the second multiplication result as the working voltage for determining the working mode of the photovoltaic storage DC microgrid. At this time, the calculation formula for the working voltage is:

[0109] v dcz = kxz·v dcH +(1-kxz)·v dcL (4)

[0110] Among them, v dcz Indicates the operating voltage, v dcH Represents the second filter voltage, v dcL represents the first filter voltage, kxz represents the second filter weight coefficient obtained after adjusting the third filter weight coefficient. (1-kxz) represents the first filter weight coefficient. kxz·v dcHis the second multiplication result obtained by multiplying the second filter voltage and the second filter weight coefficient, (1-kxz)·v dcL The first multiplication result is obtained by multiplying the first filter voltage and the first filter weight coefficient. At this time, the calculated working voltage takes into account both the filtering effect and the dynamic performance, and the proportion of the filtering effect and the dynamic performance is also determined in combination with the actual voltage, thereby ensuring the accuracy of the working voltage.

[0111] Step 2100: operate the photovoltaic-storage DC microgrid in a corresponding operating mode according to the operating voltage, and each operating mode has a corresponding operating voltage.

[0112] As mentioned above, by reading the actual voltage of the common DC bus in the photovoltaic storage DC microgrid, the first filter parameter and the second filter parameter are used to perform low-pass filtering on the actual voltage respectively to obtain the first filter voltage and the second filter voltage respectively, and then the first voltage difference indicating the degree of actual voltage fluctuation can be obtained. Then, the first filter weight coefficient and the second filter weight coefficient are set in combination with the first voltage difference, which can enhance the filtering effect or enhance the dynamic performance in a targeted manner, and when the real-time voltage changes, the corresponding first filter weight coefficient and the second filter weight coefficient can be automatically determined without manual adjustment, which also reduces the labor cost. In addition, by introducing the voltage fluctuation threshold, it can be clear whether the real-time voltage is in the dynamic range or the steady-state range, and then a more reasonable second filter weight coefficient can be set. For example, when it is in the steady-state range, the second filter weight coefficient can be directly assigned to increase the fluctuation suppression capability. When it is in the dynamic range, the voltage change can be quickly tracked to ensure the accuracy of the working voltage and avoid the wrong switching of the working mode. In addition, the third filter weight coefficient is introduced as an intermediate variable, so that when the dynamic interval changes to the steady-state interval, the third filter weight coefficient can be adjusted successively to avoid affecting the stability of the photovoltaic storage DC microgrid. When the steady-state interval changes to the dynamic interval, the third filter weight coefficient can be directly adjusted to ensure rapid tracking and response to voltage changes.

[0113] The following is an example of a method for determining the working voltage of a photovoltaic DC microgrid provided in an embodiment of the present application. In this example, the first filtering parameter j L =0.98, the second filter parameter j H =0.7, voltage fluctuation threshold a=10, preset coefficient b=0.1, coefficient adjustment value is 0.0002. Figure 3 This is an example flow chart of a method for determining the working voltage of a photovoltaic-storage DC microgrid provided by an embodiment of the present application. Figure 3 The example process includes reading the actual voltage v of the common DC bus dc , then, according to j L v dcBy performing low-pass filtering (refer to formula (1)), the first filtered voltage v can be obtained. dcL , according to j H v dc The second filtered voltage v can be obtained by low-pass filtering (refer to formula (2)). dcH After that, calculate the first voltage difference v abs , v abs =v dcL -v dcH . Determine the absolute value of the first voltage difference |v abs |Is it greater than a? If |v abs |>a, calculate the second filtering weight coefficient kx, kx=[(|v abs |-10)·0.1] 2 If |v abs |≤a, take kx=0.

[0114] After calculating kx, limit it to 0≤kx≤1. Then, determine whether kx is greater than kxz. kxz is the third weight filter coefficient, and kxz is used as the intermediate variable of kx. If kx>kxz, then kxz=kxz-0.0002, and then determine whether kx is greater than kxz until kx=kxz. If kx≤kxz, then kx=kxz. Then, use kxz as the second filter weight coefficient used this time, and calculate the value according to the effect of kxz on v dcL and v dcH The weighted aggregation is performed through formula (4) to obtain the working voltage v dcz After that, the working mode of the photovoltaic storage DC microgrid can be determined based on the above.

[0115] Figure 4 A first signal simulation diagram provided by an embodiment of the present application, Figure 5 A second signal simulation diagram provided by an embodiment of the present application, Figure 4 and Figure 5 is used Figure 3 Voltage signal simulation diagram when the working voltage determination method is shown. Figure 4 and Figure 5 The waveform “before filtering” can be considered as the waveform of the actual voltage, the waveform “τ=0.7” can be considered as the waveform of the second filtered voltage, the waveform “τ=0.98” can be considered as the waveform of the first filtered voltage, and the waveform of “weighted aggregate filtering” can be considered as the waveform of the working voltage.

[0116] Figure 4 The actual voltage shown is in a steady-state range, at which time the voltage fluctuation is small (ie, the voltage value changes little). Figure 5 The actual voltage shown is in the dynamic range, at this time, the voltage fluctuation is large (that is, the voltage value changes greatly). Figure 4 and Figure 5 It can be seen that the larger the filter parameter, the stronger the filtering effect. When the filter parameter is 0.7, in the steady-state interval, the fluctuation of the second filter voltage is still relatively obvious, and it may not be possible to suppress the erroneous change of the working mode. In the dynamic interval, the waveform of the second filter voltage is closer to the waveform of the actual voltage, and there is a small lag. At this time, the waveform of the second filter voltage can more accurately reflect the voltage fluctuation when switching the working mode. Therefore, the filter parameter 0.7 is more suitable for the dynamic interval, that is, it focuses on dynamic performance. When the filter parameter is 0.98, in the steady-state interval, the fluctuation of the first filter voltage is smoother and smaller. At this time, the first filter voltage cannot change the working mode. In the dynamic interval, the problem of the lag of the first filter voltage is more serious, which will affect the dynamic performance of the photovoltaic storage DC microgrid. Therefore, the filter parameter 0.98 is more suitable for the steady-state interval, that is, it focuses on the steady-state effect. On this basis, the working voltage obtained by the working voltage determination method in the embodiment of the present application is combined with the two filtering parameters. In the steady-state range, the voltage fluctuation is very small and the working mode cannot be changed, which can avoid incorrect switching of the working mode. In the dynamic range, the voltage fluctuation when switching the working mode can be reflected, and there is basically no lag. Therefore, both the filtering effect and the dynamic performance are guaranteed.

[0117] Figure 6 A schematic diagram of a device for determining the working voltage of a photovoltaic DC microgrid provided in one embodiment of the present application. Figure 6 The working voltage determination device includes: a voltage reading unit 301, a low-pass filtering unit 302, a weight determination unit 303, a voltage determination unit 304 and a mode determination unit 305.

[0118] Among them, the voltage reading unit 301 is used to read the actual voltage of the common DC bus in the photovoltaic storage DC microgrid; the low-pass filtering unit 302 is used to obtain the first filtered voltage and the second filtered voltage of the actual voltage respectively based on the low-pass filtering method, the first filtered voltage corresponds to the first filtering parameter, the second filtered voltage corresponds to the second filtering parameter, and the first filtering parameter is greater than the second filtering parameter; the weight determination unit 303 is used to determine the first filtering weight coefficient and the second filtering weight coefficient used this time according to the first filtered voltage and the second filtered voltage; the voltage determination unit 304 is used to weight the first filtered voltage and the second filtered voltage according to the first filtering weight coefficient and the second filtering weight coefficient to obtain the working voltage for determining the working mode of the photovoltaic storage DC microgrid; the mode determination unit 305 is used to make the photovoltaic storage DC microgrid operate in the corresponding working mode according to the working voltage, and each working mode has a corresponding working voltage.

[0119] In one embodiment of the present application, the weight determination unit 303 includes: a first difference determination subunit, used to calculate the first voltage difference between the first filter voltage and the second filter voltage; a second coefficient determination subunit, used to determine the second filter weight coefficient used this time according to the first voltage difference, and the second filter weight coefficient corresponds to the second filter voltage; the first coefficient determination subunit, used to use the difference between the preset weight coefficient and the second filter weight coefficient as the first filter weight coefficient of the first filter voltage.

[0120] In one embodiment of the present application, the second coefficient determination subunit includes: a threshold comparison subunit, which is used to determine whether the absolute value of the first voltage difference is greater than a preset voltage fluctuation threshold; a second weight coefficient determination subunit, which is used to determine the second filter weight coefficient used this time based on the first voltage difference and the voltage fluctuation threshold if it is greater than the voltage fluctuation threshold; and an assignment subunit, which is used to determine that the second filter weight coefficient is 0 if it is less than or equal to the voltage fluctuation threshold.

[0121] In one embodiment of the present application, the second filtering weight coefficient determining unit is specifically used for: if it is greater than the voltage fluctuation threshold, calculating the absolute value of the first voltage difference and the second voltage difference of the voltage fluctuation threshold; and taking the square of the product of the second voltage difference and the preset coefficient as the second filtering weight coefficient used this time.

[0122] In one embodiment of the present application, the working voltage determination device also includes: a coefficient comparison unit, which is used to determine the second filter weight coefficient used this time according to the first voltage difference, and then compare the second filter weight coefficient with the third filter weight coefficient, the third filter weight coefficient is equal to the filter weight coefficient used for the second filter voltage determined last time; a successive adjustment unit, which is used to successively reduce the third filter weight coefficient according to a preset coefficient adjustment value if the third filter weight coefficient is greater than the second filter weight coefficient, until the third filter weight coefficient is equal to the second filter weight coefficient; and a direct adjustment unit, which is used to directly adjust the third filter weight coefficient to the second filter weight coefficient if the third filter weight coefficient is less than or equal to the second filter weight coefficient.

[0123] In one embodiment of the present application, the working voltage determination device also includes: a weight limiting unit, which is used to determine the second filter weight coefficient used this time according to the first voltage difference, and then limit the second filter weight coefficient to make the second filter weight coefficient fall within a preset weight coefficient value range.

[0124] In one embodiment of the present application, the voltage determination unit 304 is specifically used to: multiply the first filtered voltage by the first filtering weight coefficient to obtain a first multiplication result, and multiply the second filtered voltage by the second filtering weight coefficient to obtain a second multiplication result; and use the sum of the first multiplication result and the second multiplication result as the operating voltage for determining the operating mode of the photovoltaic storage DC microgrid.

[0125] The operating voltage determination device provided in the embodiments of the present application is included in the operating voltage determination equipment and can be used to execute the operating voltage determination method provided in any of the above embodiments, and has corresponding functions and beneficial effects.

[0126] It is worth noting that in the embodiment of the above-mentioned working voltage determination device, the various units and modules included are only divided according to functional logic, but are not limited to the above-mentioned division, as long as the corresponding functions can be achieved; in addition, the specific names of the functional units are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention.

[0127] Figure 7 This is a schematic diagram of a device for determining the working voltage of a photovoltaic DC microgrid provided in one embodiment of the present application. Figure 7 As shown, the working voltage determination device includes a processor 40. The number of the processor 40 can be one or more. Figure 7 A processor 40 is taken as an example.

[0128] The processor 40 is connected to the common DC bus 41 of the photovoltaic storage DC microgrid. It includes direct connection or indirect connection. When indirectly connected, there are other devices or circuits between the processor 40 and the common DC bus 41. At this time, the processor 40 can drive other devices or circuits to obtain the actual voltage of the common DC bus 41.

[0129] Optionally, the program used when the processor 40 runs the working voltage determination method can be stored in the memory. The memory and the processor 40 can be connected via a bus or other means. The memory, as a computer-readable storage medium, can be used to store software programs, computer executable programs and modules, such as program instructions / modules corresponding to the working voltage determination method in the embodiment of the present application (for example, the voltage reading unit 301, the low-pass filtering unit 302, the weight determination unit 303, the voltage determination unit 304 and the mode determination unit 305 in the working voltage determination device). The processor 40 executes various functional applications and data processing of the working voltage determination device by running the software programs, instructions and modules stored in the memory, that is, realizing the above-mentioned working voltage determination method. It can be understood that when the processor 40 has a storage function, the program used when the processor 40 runs the working voltage determination method can also be stored in the processor 40.

[0130] In one embodiment, one or more processors 40 are processors used by networking equipment of a photovoltaic-storage DC microgrid. Figure 8 A schematic diagram of the structure of a photovoltaic DC microgrid provided by an embodiment of the present application. Figure 8 , the photovoltaic storage DC microgrid includes: a photovoltaic power generation device 51, an energy storage device 52, a grid-connected interface device 53 and a constant power load 54. The photovoltaic power generation device 51, the energy storage device 52, the grid-connected interface device 53 and the constant power load 54 can all be considered as networking devices of the microgrid. Each networking device can be considered as a physical entity, or each networking device can be set as one or more physical entities based on actual conditions. Currently, if any networking device is equipped with a processor, then the processor can be used as a working voltage determination device, that is, the working voltage determination method is implemented through a corresponding program. If multiple networking devices are equipped with processors, then any one or at least two of the processors installed in the networking devices can be used as a working voltage determination device, that is, the working voltage determination method is implemented through a corresponding program.

[0131] In addition, the operating voltage determination device may also include other components, which are not currently limited.

[0132] The operating voltage determination device provided in the embodiment of the present application is included in the operating voltage determination device, and can be used to execute the operating voltage determination method provided in any of the above embodiments, and has corresponding functions and beneficial effects.

[0133] One embodiment of the present application also provides a storage medium containing computer executable instructions, which, when executed by a working voltage determination device (i.e., a processor), are used to perform relevant operations in the working voltage determination method provided in any embodiment of the present application, and have corresponding functions and beneficial effects.

[0134] Those skilled in the art should understand that the embodiments of the present application may be provided as methods, systems, or computer program products.

[0135] Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the functions in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0136] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0137] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0138] Note that the above are only preferred embodiments of the present application and the technical principles used. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present application. Therefore, although the present application is described in more detail through the above embodiments, the present application is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A method for determining the working voltage of a photovoltaic-storage DC microgrid, characterized in that: include: Read the actual voltage of the common DC bus in the photovoltaic and energy storage DC microgrid; Based on the low-pass filtering method, a first filtered voltage and a second filtered voltage of the actual voltage are obtained respectively, the first filtered voltage corresponds to a first filtering parameter, the second filtered voltage corresponds to a second filtering parameter, and the first filtering parameter is greater than the second filtering parameter; Determine a first filtering weight coefficient and a second filtering weight coefficient used this time according to the first filtering voltage and the second filtering voltage; The first filtered voltage and the second filtered voltage are weighted according to the first filtering weight coefficient and the second filtering weight coefficient to obtain an operating voltage for determining an operating mode of a photovoltaic-storage DC microgrid; The photovoltaic-storage DC microgrid operates in a corresponding working mode according to the working voltage, and each working mode has a corresponding working voltage.

2. The method for determining the operating voltage according to claim 1, characterized in that: The determining the first filtering weight coefficient and the second filtering weight coefficient used this time according to the first filtering voltage and the second filtering voltage includes: Calculating a first voltage difference between the first filtered voltage and the second filtered voltage; Determine a second filtering weight coefficient used this time according to the first voltage difference, wherein the second filtering weight coefficient corresponds to a second filtering voltage; The difference between the preset weight coefficient and the second filtering weight coefficient is used as the first filtering weight coefficient of the first filtering voltage.

3. The method for determining the operating voltage according to claim 2, characterized in that: The determining the second filtering weight coefficient used this time according to the first voltage difference includes: Determining whether the absolute value of the first voltage difference is greater than a preset voltage fluctuation threshold; If it is greater than the voltage fluctuation threshold, determining a second filtering weight coefficient used this time according to the first voltage difference and the voltage fluctuation threshold; If it is less than or equal to the voltage fluctuation threshold, the second filtering weight coefficient is determined to be 0.

4. The method for determining the working voltage according to claim 3, characterized in that: If the voltage difference is greater than the voltage fluctuation threshold, determining a second filtering weight coefficient used this time according to the first voltage difference and the voltage fluctuation threshold, including: If it is greater than the voltage fluctuation threshold, calculating the absolute value of the first voltage difference and a second voltage difference of the voltage fluctuation threshold; The square of the product of the second voltage difference and the preset coefficient is used as the second filtering weight coefficient used this time.

5. The method for determining the working voltage according to claim 2, characterized in that: After determining the second filtering weight coefficient used this time according to the first voltage difference, the method includes: comparing the second filtering weight coefficient with a third filtering weight coefficient, the third filtering weight coefficient being equal to the filtering weight coefficient used by the second filtering voltage determined last time; If the third filter weight coefficient is greater than the second filter weight coefficient, the third filter weight coefficient is gradually reduced according to a preset coefficient adjustment value until the third filter weight coefficient is equal to the second filter weight coefficient; If the third filter weight coefficient is less than or equal to the second filter weight coefficient, the third filter weight coefficient is directly adjusted to the second filter weight coefficient.

6. The method for determining the working voltage according to claim 2 or 3, characterized in that: After determining the second filtering weight coefficient used this time according to the first voltage difference, the method includes: The second filtering weight coefficient is limited so that the second filtering weight coefficient is within a preset weight coefficient value range.

7. The method for determining the working voltage according to claim 1, characterized in that: The first filtering voltage and the second filtering voltage are weighted according to the first filtering weight coefficient and the second filtering weight coefficient to obtain the working voltage for determining the working mode of the photovoltaic storage DC microgrid, including: Multiplying the first filtered voltage by the first filtering weight coefficient to obtain a first multiplication result, and multiplying the second filtered voltage by the second filtering weight coefficient to obtain a second multiplication result; The sum of the first multiplication result and the second multiplication result is used as the operating voltage for determining the operating mode of the photovoltaic-storage DC microgrid.

8. A device for determining the working voltage of a photovoltaic-storage DC microgrid, characterized in that: include: A voltage reading unit is used to read the actual voltage of the common DC bus in the photovoltaic and energy storage DC microgrid; A low-pass filtering unit, used for obtaining a first filtered voltage and a second filtered voltage of the actual voltage respectively based on a low-pass filtering method, wherein the first filtered voltage corresponds to a first filtering parameter, the second filtered voltage corresponds to a second filtering parameter, and the first filtering parameter is greater than the second filtering parameter; A weight determination unit, configured to determine a first filtering weight coefficient and a second filtering weight coefficient used this time according to the first filtering voltage and the second filtering voltage; A voltage determination unit, configured to weight the first filtered voltage and the second filtered voltage according to the first filtering weight coefficient and the second filtering weight coefficient to obtain an operating voltage for determining an operating mode of a photovoltaic-storage DC microgrid; The mode determination unit is used to make the photovoltaic and energy storage DC microgrid operate in a corresponding working mode according to the working voltage, and each working mode has a corresponding working voltage.

9. A device for determining the working voltage of a photovoltaic-storage DC microgrid, characterized in that: include: one or more processors; When the one or more processors execute one or more programs stored in the memory, the one or more processors implement the operating voltage determination method as described in any one of claims 1-7.

10. The operating voltage determination device according to claim 9, characterized in that: The one or more processors are processors used by the networking equipment of the photovoltaic and energy storage DC microgrid.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method for determining the operating voltage as described in any one of claims 1 to 7 is implemented.

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