Power failure detection method, controller and energy storage device

Abstract

The application provides a power-off detection method, a controller and an energy storage device. The power-off detection method comprises the following steps: when a preset power-off triggering condition is met, a voltage curve of a bus capacitor in a first preset time length is obtained; an n-order derivative of the voltage curve is calculated to obtain an actual power-off coefficient; n is a preset positive integer; and the power state of the AC side is determined based on the actual power-off coefficient, and the power state is a mains power connection state or a mains power-off state. In the application, the voltage curve of the bus capacitor is obtained when the mains power is off, the actual power-off coefficient is calculated, and the power state of the AC side of the rectifier circuit is determined according to the actual power-off coefficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power supply, in particular to a power failure detection method, a controller and an energy storage device. BACKGROUND

[0002] In a common UPS (uninterruptible power supply) power switching scheme, the UPS power supply can compare the effective value of the grid input voltage with a preset value to identify whether the grid is powered off. However, when the grid is powered off, the voltage of the grid does not directly disappear, but gradually decreases. Therefore, the UPS power supply needs to wait for two to three cycles before detecting that the effective value of the grid input voltage is less than the preset value, triggering the UPS switching operation. This method has a delay of about 60 ms, which is too high. SUMMARY

[0003] To solve the problems in the prior art, the present application provides a power failure detection method, a controller and an energy storage device to improve the detection speed of grid power failure.

[0004] The present application provides a power failure detection method applied to an energy storage device, the energy storage device comprising a rectifier circuit, an AC side of the rectifier circuit being used to connect with a commercial power supply, a DC side of the rectifier circuit comprising a DC bus and a bus capacitor arranged on the DC bus, the power failure detection method comprising:

[0005] When a preset power failure triggering condition is met, obtaining a voltage curve of the bus capacitor within a first preset time length;

[0006] Calculating the n-th derivative of the voltage curve to obtain an actual power failure coefficient; n is a preset positive integer;

[0007] Determining the power receiving state of the AC side based on the actual power failure coefficient, the power receiving state being a commercial power supply access state or a commercial power supply power failure state.

[0008] In an embodiment, the obtaining of the voltage curve of the bus capacitor within the first preset time length comprises:

[0009] Within the first preset time length, collecting the voltage across the bus capacitor to obtain a plurality of sampling voltage values;

[0010] Based on a preset n-th function model, performing curve fitting on the plurality of sampling voltage values to obtain the voltage curve of the bus capacitor.

[0011] In an embodiment, the determining of the power receiving state of the AC side based on the actual power failure coefficient comprises:

[0012] Calculating the coefficient difference between the actual power failure coefficient and a preset power failure coefficient;

[0013] If the coefficient difference value is within a preset difference value range, it is determined that the AC side is in a power-off state.

[0014] If the coefficient difference value is outside the preset difference value range, it is determined that the AC side is in a power-on state.

[0015] In an embodiment, the preset power-off trigger condition is:

[0016] It is detected that the voltage value across the bus capacitor is less than a first preset voltage value.

[0017] In an embodiment, when the preset power-off trigger condition is met, the power-off detection method further includes:

[0018] If it is detected that the voltage value across the bus capacitor reaches the first preset voltage value within the first preset time length, it is determined that the AC side is in a power-on state.

[0019] In an embodiment, the power-off detection method further includes:

[0020] An input voltage value of the AC side is obtained;

[0021] When the input voltage value is less than a second preset voltage value, timing is started;

[0022] If the timing duration reaches a second preset time length, it is determined that the AC side is in a power-off state.

[0023] If the timing duration does not reach the second preset time length, and it is detected that the input voltage value reaches the second preset voltage value, the timing is terminated, and it is determined that the AC side is in a power-on state.

[0024] In an embodiment, the preset power-off trigger condition is:

[0025] It is detected that the input voltage value is less than the second preset voltage value.

[0026] The application also proposes a controller, including a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the above-mentioned power-off detection method when executing the program.

[0027] The application also proposes an energy storage device, including a rectifier circuit, an energy storage assembly, and the above-mentioned controller.

[0028] The AC side of the rectifier circuit is used to be connected with a power supply, and the DC side of the rectifier circuit includes a DC bus and a bus capacitor arranged on the DC bus.

[0029] The controller is configured to determine the power receiving state of the AC side according to the voltage across the bus capacitor and / or the voltage of the AC side, and control the energy storage component to discharge when the power receiving state is determined to be the mains power outage state.

[0030] In an embodiment, the energy storage device further comprises:

[0031] a voltage detection circuit electrically connected to the bus capacitor of the rectifier circuit, the AC side of the rectifier circuit, and the controller respectively, the voltage detection circuit being configured to collect the voltage across the bus capacitor to obtain a plurality of sampling voltage values, and detect the input voltage of the AC side;

[0032] The controller is further configured to determine the power receiving state of the AC side according to the plurality of sampling voltage values and / or the input voltage of the AC side.

[0033] The present application determines the power receiving state of the AC side of the rectifier circuit according to the actual outage coefficient calculated by obtaining the voltage curve of the bus capacitor when the mains power is out. The voltage curve of the bus capacitor can be obtained in a short time because the discharge speed of the bus capacitor is fast when the mains power is out. The voltage curve and the outage curve are compared by calculating the n-th derivative of the voltage curve, so that the comparison of multiple points on the voltage curve is not needed, and the mains power outage is determined without waiting for the grid voltage to drop below the preset value, thereby improving the detection speed of the mains power outage. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Fig. 1 is a waveform schematic diagram of the mains power outage curve;

[0035] Figure 2 Fig. 2 is a flowchart of an embodiment of the power outage detection method of the present application;

[0036] Figure 3 Fig. 3 is a detailed flowchart of step S1 in the power outage detection method of the present application;

[0037] Figure 4 Fig. 4 is a detailed flowchart of step S3 in the power outage detection method of the present application;

[0038] Figure 5 Fig. 5 is a flowchart of another embodiment of the power outage detection method of the present application;

[0039] Figure 6 Fig. 6 is a flowchart of another embodiment of the power outage detection method of the present application;

[0040] Figure 7 Fig. 7 is a structural schematic diagram of an embodiment of the energy storage device of the present application;

[0041] Figure 8Fig. 1 is a configuration diagram of an embodiment of a rectifier circuit of the present application.

[0042] Explanation of main element symbols

[0043] Energy storage device 10 Rectifier circuit 110

[0044] DC bus 111 Bus capacitor C1

[0045] Energy storage assembly 120 Controller 130

[0046] Voltage detection circuit 140 Voltage conversion circuit AC / DC

[0047] The following detailed description will further describe the present application with reference to the above-described drawings. DETAILED DESCRIPTION

[0048] The following description will reference the accompanying drawings so as to more fully understand the present application. The drawings show exemplary embodiments of the present application. However, the present application can be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. These exemplary embodiments are provided so that this application will be thorough and complete, and will fully convey the scope of the application to those skilled in the art. Like reference numerals refer to like or similar components throughout the specification.

[0049] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms "including", "includes", "having", "has", "a", "an", "one" or "said one" are used in this specification and / or claims, they are intended to be inclusive (meaning that there can be additional items) and / or they are intended to be quantitatively-singular (meaning that there is no additional items). However, it will be understood by those within the art that the application can be practiced without the specific details set forth in the description.

[0050] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure and will not be interpreted in an overly literal sense unless expressly so defined herein.

[0051] The following description will describe the example embodiments with reference to the drawings. It should be noted that the components depicted in the drawings are not necessarily shown to scale; rather, the same or similar components will be given the same or similar reference numerals or similar technical terms.

[0052] The grid-connected power equipment (such as energy storage equipment) supplies power for the power equipment. When the grid power fails, the voltage of the grid does not directly disappear, but gradually decreases according to the curve shown in Figure 1 . Figure 1 The curve is shown in the figure, the horizontal coordinate is time, and the vertical coordinate is voltage. The curve is calculated according to the voltage drop of different bus capacitors in the power equipment. Therefore, when detecting the grid power failure in the related art, detecting according to the real-time input voltage of the grid will easily lead to detection lag. Therefore, when the grid power fails, other power supply cannot be switched in time, which affects the use of the power equipment.

[0053] Referring to Figure 2 , Figure 2 An energy storage equipment 10 provided by an embodiment of the present application includes a rectifier circuit 110, an energy storage component 120, and a controller 130. The controller 130 is configured to execute the power failure detection method provided by an embodiment of the present application.

[0054] As shown in Figure 3 , the AC side of the rectifier circuit 110 is configured to be connected to the commercial power supply, and the DC side of the rectifier circuit 110 includes a DC bus 111 and a bus capacitor C1 arranged on the DC bus 111. The rectifier circuit 110 further includes a voltage conversion circuit AC / DC configured to convert the AC power input from the AC side and output DC power to the DC bus 111. The bus capacitor C1 arranged on the DC bus 111 is configured to store energy when receiving the DC power.

[0055] The controller 130 is configured to determine the power receiving state of the AC side according to the voltage across the bus capacitor C1 and / or the voltage of the AC side, and control the energy storage component 120 to discharge to supply power to the load when determining that the power receiving state is a commercial power failure state.

[0056] The detailed structure of the controller 130 can refer to the above-mentioned embodiments, which will not be described here. It can be understood that, since the above-mentioned controller 130 is used in the energy storage equipment 10 of the present application, the embodiments of the energy storage equipment 10 of the present application include all the technical solutions of all the embodiments of the above-mentioned controller 130, and the technical effects achieved are also completely the same, which will not be described here.

[0057] In an embodiment, the energy storage equipment 10 further includes a voltage detection circuit 140.

[0058] The voltage detection circuit 140 is electrically connected to the bus capacitor C1 of the rectifier circuit 110, the AC side of the rectifier circuit 110, and the controller 130, respectively. The voltage detection circuit 140 is configured to collect the voltage across the bus capacitor C1 to obtain a plurality of sampling voltage values, and detect the input voltage of the AC side. The voltage detection circuit 140 can be composed of resistors.

[0059] The controller 130 is further configured to determine the power receiving state of the AC side according to the plurality of sampling voltage values and / or the input voltage of the AC side.

[0060] With reference to Figure 4 The application provides a power-off detection method applied to an energy storage device 10. The energy storage device 10 comprises a rectifier circuit 110, an AC side of the rectifier circuit 110 being configured to be connected to a power supply, and a DC side of the rectifier circuit 110 comprising a DC bus 111 and a bus capacitor C1 arranged on the DC bus 111. The power-off detection method comprises the following steps.

[0061] S1: When a preset power-off triggering condition is met, obtaining a voltage curve of the bus capacitor C1 within a first preset time length.

[0062] The preset power-off triggering condition can be that a voltage value across the bus capacitor C1 is detected to be less than a first preset voltage value, and / or an input voltage value of the AC side is detected to be less than a second preset voltage value. In the case where the power supply is not powered off, the voltage across the bus capacitor C1 is a relatively stable value, and the input voltage of the AC side fluctuates regularly in a sinusoidal manner. When the voltage across the bus capacitor C1 is less than the first preset voltage value, and / or the input voltage value of the AC side is less than the second preset voltage value, it can be a short-time voltage fluctuation or a continuous power-off. Therefore, by detecting the voltage curve of the bus capacitor C1 within the first preset time length, the power receiving state of the AC side of the rectifier circuit 110 can be accurately determined. The first preset time length can be determined according to the discharge time length of the bus capacitor C1. When the bus capacitor C1 is powered off, the discharge speed is relatively fast, and the first preset time length can be set to be relatively short, for example, 8 ms, 10 ms, 12 ms, etc. In this way, the voltage curve of the bus capacitor C1 can be obtained within a short time, and then the power receiving state of the AC side can be determined according to the voltage curve, thereby improving the identification speed of the power receiving state. The first preset voltage value can be set according to the actual working voltage across the bus capacitor C1, for example, when the actual working voltage across the bus capacitor is 60 V, the first preset voltage value can be set to 55 V, 50 V, etc.

[0063] S2: Calculating the n-th derivative of the voltage curve to obtain an actual power-off coefficient; n is a preset positive integer.

[0064] The value of n can be set according to the order of the voltage curve. For example, if the voltage curve is a quadratic function y=ax 2 +bx+c, then n is 2, and the actual power-off coefficient a can be obtained by twice differentiating the voltage curve. In addition, n can also be set to other positive integers, which is not limited herein.

[0065] In practical applications, the bus capacitor C1 is of a fixed capacitance value after selection, and thus the power-off curve of the bus capacitor C1 is consistent or approximately consistent. Therefore, the power receiving state of the AC side can be determined by detecting whether the voltage curve and the power-off curve of the bus capacitor C1 are consistent. If the voltage curve and the power-off curve are similar or consistent, the highest order coefficient should be consistent. Therefore, the embodiment can compare the voltage curve and the power-off curve by calculating the n-th derivative of the voltage curve, without comparing multiple points on the voltage curve. In this way, the comparison speed can be improved, and the identification speed of the power receiving state is further improved.

[0066] S3: determining the power receiving state of the AC side based on the actual power-off coefficient, the power receiving state being a mains power-on state or a mains power-off state.

[0067] The actual power-off coefficient can be compared with the preset power-off coefficient to determine the power receiving state of the AC side. If the actual power-off coefficient is close to or equal to the preset power-off coefficient, it indicates that the AC side is in a mains power-off state. If the energy storage device is connected to a load at this time, and the power required by the load is entirely supplied by the mains, the energy storage assembly 120 needs to be switched to supply power to the load to ensure stable power supply. If the actual power-off coefficient is not close to or equal to the preset power-off coefficient, it indicates that the AC side is in a mains power-on state.

[0068] The application obtains the voltage curve of the bus capacitor C1 when the mains is powered off to calculate the actual power-off coefficient, and determines the power receiving state of the AC side of the rectifier circuit 110 according to the actual power-off coefficient. When the bus capacitor C1 is powered off, the discharge speed is fast, and the voltage curve of the bus capacitor C1 can be obtained in a short time. The voltage curve and the power-off curve are compared by calculating the n-th derivative of the voltage curve, without comparing multiple points on the voltage curve, and without waiting for the grid voltage to drop below the preset value to determine the grid power-off, thereby improving the detection speed of the grid power-off.

[0069] Reference Figure 5 In an embodiment, the voltage curve of the bus capacitor C1 within the first preset time period is obtained, including:

[0070] S11: collecting the voltage across the bus capacitor C1 within the first preset time period to obtain a plurality of sampling voltage values.

[0071] When the bus capacitor C1 is powered off, the discharge speed is fast, and the first preset time period can be set to be short. The sampling voltage values can be obtained by the voltage detection circuit 140. By setting a suitable sampling frequency, the voltage detection circuit 140 can collect a plurality of sampling voltage values within the first preset time period, and then the voltage curve of the bus capacitor C1 can be determined based on the plurality of sampling voltage values.

[0072] S12: Based on a preset nth-order function model, multiple sampled voltage values ​​are fitted to obtain the voltage curve of the bus capacitor C1.

[0073] The sampling frequency can be set according to actual needs. For example, a higher sampling frequency can be set to collect more sampled voltage values ​​within a first preset time period to obtain a more accurate voltage curve.

[0074] Reference Figure 6 and Figure 2 In one embodiment, determining the power receiving state on the AC side based on the target power-down constant includes:

[0075] S31: Calculate the difference between the actual power loss coefficient and the preset power loss coefficient.

[0076] When the AC side of the rectifier circuit 110 is powered off, the voltage curve and the power-off curve may not be completely consistent, and there may also be a difference between the actual power-off coefficient and the preset power-off coefficient of the power-off curve. Therefore, by calculating the difference between the actual power-off coefficient and the preset power-off coefficient, and comparing the coefficient difference, the power receiving state of the AC side can be determined more accurately.

[0077] S32: If the coefficient difference is within the preset difference range, then the AC side is determined to be in a mains power failure state.

[0078] The preset difference range can be set according to specific application scenarios, such as 0.5, 0.7, etc. If the coefficient difference is within the preset difference range, it means that the actual power loss coefficient is close to the power loss coefficient, and the voltage curve is approximately the power loss curve. In this case, it is determined that the AC side is in a mains power loss state.

[0079] S33: If the coefficient difference is outside the preset difference range, then the AC side is determined to be in the mains power access state.

[0080] If the coefficient difference is outside the preset difference range, it means that the actual power outage coefficient is significantly different from the power outage coefficient, and the voltage curve is not similar to the power outage curve. In this case, it is determined that the AC side is in the state of mains power connection.

[0081] Reference Figure 7 In one embodiment, when a preset power-down trigger condition is met, the power-down detection method further includes:

[0082] S4: If the voltage across the bus capacitor C1 reaches the first preset voltage value within the first preset time period, it is determined that the AC side is in the mains power connection state.

[0083] If the voltage value across the bus capacitor C1 is detected to return to the first preset voltage value within the first preset time length, it is indicated that the commercial power is only a short-time fluctuation, and it is determined that the AC side is in a commercial power access state. In this way, by detecting the voltage value across the bus capacitor C1 within the first preset time length, it is avoided that the commercial power fluctuation is misjudged as a power-off, and the accuracy of the power-off detection method is improved.

[0084] With reference to Figure 8 In an embodiment, the power-off detection method further includes:

[0085] S5: When a preset power-off triggering condition is met, an input voltage value of the AC side is obtained.

[0086] The input voltage value of the AC side can be determined by the voltage detection circuit 140. When the commercial power is not powered off, the input voltage of the AC side changes regularly in a sinusoidal waveform. When the commercial power is powered off, the input voltage of the AC side changes irregularly in a sinusoidal waveform or continuously decreases. In this embodiment, the input voltage value of the AC side is obtained, so as to determine the power state of the AC side according to the input voltage value of the AC side.

[0087] S6: When the input voltage value is less than a second preset voltage value, timing is started.

[0088] The second preset voltage value can be set according to the amplitude of the input voltage, for example, a value between 0 and 220V. When the input voltage value decreases to be less than the second preset voltage value, it can be a short-time voltage fluctuation, or a continuous power-off state. Therefore, the power-off time length needs to be timed, so as to more accurately determine the power state of the AC side.

[0089] S7: If the timing time length reaches a second preset time length, it is determined that the AC side is in a commercial power-off state.

[0090] The timing time length can be determined by a timer. The second preset time length can be set according to the actual application scenario. For example, when the AC side commercial power is normally connected, there is a normal fluctuation of the input voltage, and from the second preset voltage value to the second preset voltage value, the longest time does not exceed half a period, and the second preset time length can be set to half a period of the input voltage, or slightly greater than half a period.

[0091] S8: If the timing time length does not reach the second preset time length, and the input voltage value is detected to reach the second preset voltage value, the timing is terminated, and it is determined that the AC side is in a commercial power access state.

[0092] The input voltage returns to the second preset voltage value when the timing time length does not reach the second preset time length, which indicates that the input voltage is only a short-time fluctuation, and the commercial power is still normally connected. The timing is terminated, and it is determined that the AC side is in a commercial power access state.

[0093] The controller 130 provided in the application comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the program, the power-off detection method described above is realized.

[0094] In the foregoing, the specific embodiments of the application are described with reference to the drawings. However, those skilled in the art can understand that various changes and replacements can be made to the specific embodiments of the application without departing from the spirit and scope of the application. These changes and replacements are all within the scope defined by the application.

Claims

1. A power failure detection method applied to an energy storage device, the energy storage device including a rectifier circuit, the AC side of the rectifier circuit being connected to mains power, the DC side of the rectifier circuit including a DC bus and a bus capacitor disposed on the DC bus, characterized in that, The power failure detection method includes: When the preset power failure trigger condition is met, the voltage curve of the bus capacitor within a first preset time period is obtained; Calculate the nth derivative of the voltage curve to obtain the actual power loss coefficient; n is a preset positive integer; The power receiving state of the AC side is determined based on the actual power loss coefficient, and the power receiving state is either mains power connected or mains power outage.

2. The power failure detection method as described in claim 1, characterized in that, The acquisition of the voltage curve of the bus capacitor within a first preset time period includes: Within the first preset time period, the voltage across the bus capacitor is collected to obtain multiple sampled voltage values; Based on a preset nth-order function model, curve fitting is performed on multiple sampled voltage values ​​to obtain the voltage curve of the bus capacitor.

3. The power failure detection method as described in claim 1, characterized in that, Determining the power receiving state of the AC side based on the actual power loss constant includes: Calculate the difference between the actual power loss coefficient and the preset power loss coefficient; If the coefficient difference is within the preset difference range, then it is determined that the AC side is in a mains power failure state; If the coefficient difference is outside the preset difference range, then the AC side is determined to be in a mains power access state.

4. The power failure detection method as described in claim 1, characterized in that, The preset power failure trigger condition is: The voltage across the bus capacitor was detected to be less than a first preset voltage value.

5. The power failure detection method as described in claim 4, characterized in that, When the preset power-down trigger condition is met, the power-down detection method further includes: If the voltage across the bus capacitor reaches the first preset voltage value within the first preset time period, it is determined that the AC side is in a mains power connection state.

6. The power failure detection method as described in claim 1, characterized in that, The power failure detection method further includes: Obtain the input voltage value on the AC side; Timing begins when the input voltage value is less than the second preset voltage value; If the timing duration reaches the second preset duration, it is determined that the AC side is in a mains power failure state; If the timing duration does not reach the second preset duration, and the input voltage value is detected to reach the second preset voltage value, then the timing is terminated, and it is determined that the AC side is in the mains power access state.

7. The power failure detection method as described in claim 6, characterized in that, The preset power failure trigger condition is: The input voltage value was detected to be less than the second preset voltage value.

8. A controller, characterized in that, The device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, it implements the power-down detection method as described in any one of claims 1-7.

9. An energy storage device, characterized in that, The energy storage device includes a rectifier circuit, an energy storage component, and a controller as described in claim 8; The AC side of the rectifier circuit is used to connect to the mains power, and the DC side of the rectifier circuit includes a DC bus and a bus capacitor disposed on the DC bus. The controller is used to determine the power receiving state of the AC side based on the voltage across the bus capacitor and / or the voltage on the AC side, and when the power receiving state is determined to be a mains power failure state, it controls the energy storage component to discharge.

10. The energy storage device as described in claim 9, characterized in that, The energy storage device also includes: A voltage detection circuit is electrically connected to the bus capacitor of the rectifier circuit, the AC side of the rectifier circuit, and the controller, respectively; the voltage detection circuit is used to collect the voltage across the bus capacitor to obtain multiple sampled voltage values; and to detect the input voltage on the AC side; The controller is also configured to determine the power-on state of the AC side based on a plurality of the sampled voltage values ​​and / or the input voltage of the AC side.

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