A power conversion device and control method thereof, and a power supply system

Abstract

The present invention discloses a power conversion device and a control method thereof, and a power supply system. The first side of the power conversion device is connected to a battery, and the second side of the power conversion device can be selectively connected to a power grid or a load; the method comprises: sampling and acquiring electrical parameters of the second side of the power conversion device; determining the actual current value of the battery at least according to the electrical parameters of the second side, wherein the actual current value includes an actual charging current value or an actual discharging current value; and adjusting the operation of the power conversion device based on the actual current value. The technical solution of the present invention improves the accuracy of determining the battery current.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a power conversion device and a control method thereof, and a power supply system. Background Art

[0002] With the rapid development of new energy technology, batteries are being used more and more widely. There is a bidirectional power conversion device that can convert the electric energy discharged by the battery into another form of electric energy to provide to the load, and can also use an external power supply to charge the battery.

[0003] In order to ensure that the current when the battery is charging or discharging meets the charging and discharging requirements, the power conversion device needs to obtain the current on the battery side during the charging and discharging process during operation, so as to adjust the battery charging and discharging current in time when the battery charging and discharging current does not meet the requirements.

[0004] At present, most current sensors or signal sampling circuits are used to obtain the current during the battery charging and discharging process. However, the charging and discharging current of the battery on the low-voltage side is not only relatively large, but also has a wide current variation range, requiring a larger acquisition range, resulting in high costs for current sensors or signal sampling circuits, and difficulty in accurately obtaining the battery charging and discharging current. Summary of the invention

[0005] The present invention provides a power conversion device and a control method thereof, and a power supply system to solve the problems of high cost and low accuracy of battery current sampling.

[0006] According to one aspect of the present invention, a control method for a power conversion device is provided, wherein a first side of the power conversion device is connected to a battery, and a second side of the power conversion device is selectively connected to a power grid or a load; the method comprises:

[0007] Sampling and acquiring electrical parameters of the second side of the power conversion device;

[0008] determining an actual current value of the battery at least according to the electrical parameter of the second side, wherein the actual current value includes an actual charging current value or an actual discharging current value;

[0009] The operation of the power conversion device is adjusted based on the actual current value.

[0010] Optionally, the sampling and acquiring the electrical parameters of the second side of the power conversion device includes:

[0011] Sampling and acquiring a first voltage value and a first current value of a second side of the power conversion device;

[0012] The determining the actual current value of the battery at least according to the electrical parameter of the second side includes:

[0013] Sampling and acquiring an actual voltage value of the battery on the first side of the power conversion device;

[0014] determining a first power value of the second side according to the first voltage value and the first current value;

[0015] The actual current value of the battery is determined according to the actual voltage value of the battery, the conversion efficiency of the power conversion device and the first power value.

[0016] Optionally, determining the actual current value of the battery according to the actual voltage value of the battery, the conversion efficiency of the power conversion device and the first power value includes:

[0017] Determining a power range within which the first power value lies;

[0018] The actual current value of the battery is determined according to the conversion efficiency of the power conversion device corresponding to the power range, the actual voltage value of the battery and the first power value.

[0019] Optionally, determining the actual current value of the battery according to the actual voltage value of the battery, the conversion efficiency of the power conversion device and the first power value includes:

[0020] Determine a second power value of the first side of the power conversion device according to the conversion efficiency and the first power value;

[0021] An actual current value of the battery is determined according to the second power value and an actual voltage value of the battery.

[0022] Optionally, the sampling and acquiring the electrical parameters of the second side of the power conversion device includes:

[0023] Sampling and acquiring a second current value of a second side of the power conversion device;

[0024] The determining the actual current value of the battery at least according to the electrical parameter of the second side includes:

[0025] The actual current value of the battery is determined according to a mapping relationship between the second current value of the second side and the battery current.

[0026] Optionally, the mapping relationship between the second current value of the second side and the battery current is determined according to the following method:

[0027] Under test conditions, respectively sampling a first-side current value and a second-side current value of the power conversion device;

[0028] A mapping relationship curve is fitted according to the first-side current value and the second-side current value.

[0029] Optionally, the sampling and acquiring the electrical parameters of the second side of the power conversion device includes:

[0030] Sampling and acquiring a first voltage value and a first current value of a second side of the power conversion device;

[0031] The determining the actual current value of the battery at least according to the electrical parameter of the second side includes:

[0032] Sampling and acquiring an actual voltage value of the battery on the first side of the power conversion device;

[0033] Determine a first actual current value of the battery according to the actual voltage value of the battery, the conversion efficiency of the power conversion device, the first current value and the first voltage value;

[0034] Determining a second actual current value of the battery according to a mapping relationship between the first current value of the second side and the battery current;

[0035] An actual current value of the battery is determined according to the first actual current value and the second actual current value.

[0036] Optionally, determining the actual current value of the battery according to the first actual current value and the second actual current value includes:

[0037] An average value of the first actual current value and the second actual current value is used as the actual current value of the battery.

[0038] According to another aspect of the present invention, a power conversion device is provided, wherein a first side of the power conversion device is connected to a battery, and a second side of the power conversion device is selectively connected to a power grid or a load; the power conversion device comprises:

[0039] A collection unit, the collection unit is configured to obtain electrical parameters of the second side of the power conversion device;

[0040] A control unit, the control unit being configured to determine an actual current value of the battery at least according to the electrical parameters of the second side, and to adjust the operation of the power conversion device based on the actual current value, wherein the actual current value includes an actual charging current value or an actual discharging current value.

[0041] According to another aspect of the present invention, there is provided a power supply system, the power supply system comprising a battery and the power conversion device according to any embodiment of the present invention;

[0042] The first side of the power conversion device is connected to the battery;

[0043] The second side of the power conversion device is connected to the power grid, and is used to charge the battery with the AC input power of the power grid;

[0044] Alternatively, the second side of the power conversion device is connected to a load, and is used to convert the DC input power of the battery into AC power to supply power to the load.

[0045] The technical solution of the embodiment of the present invention can determine the actual current value of the battery on the first side of the power conversion device by collecting the electrical parameters of the second side of the power conversion device, at least based on the electrical parameters of the second side of the power conversion device. This eliminates the need to use a current collection device to collect the current value of the battery, facilitates the determination of the actual current value of the battery, reduces hardware costs, and can improve the accuracy of determining the actual current value of the battery. At the same time, the operation of the power conversion device is adjusted based on the determined actual current value, which is beneficial to ensuring that the working state of the power conversion device is consistent with the expected state.

[0046] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0048] Figure 1 is a flow chart of a control method for a power conversion device provided by an embodiment of the present invention;

[0049] Figure 2 is a flow chart of another control method of a power conversion device provided by an embodiment of the present invention;

[0050] Figure 3 is a flow chart of another control method of a power conversion device provided by an embodiment of the present invention;

[0051] Figure 4 is a schematic diagram of a current mapping relationship curve provided by an embodiment of the present invention;

[0052] Figure 5 is a flow chart of another control method of a power conversion device provided by an embodiment of the present invention;

[0053] Figure 6 is a schematic structural diagram of a power conversion device provided by an embodiment of the present invention;

[0054] Figure 7 is a structural schematic diagram of a power supply system provided by an embodiment of the present invention;

[0055] Figure 8 It is a structural schematic diagram of a power supply system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0056] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0057] It should be noted that, in this article, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not clearly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements limited by the sentence "include one ..." do not exclude the existence of other identical elements in the process, method, article or device including the element. It should be further understood that, as used in this article, the singular form "one", "one" and "the" are intended to also include plural forms, unless there is an opposite indication in the context. Furthermore, the terms "or", "and / or", "include at least one of the following" etc. used in this article can be interpreted as inclusive, or mean any one or any combination. Only when the combination of elements, functions, steps or operations is inherently mutually exclusive in some way, the exception of this definition will occur.

[0058] It should be understood that, although the terms first, second, third, etc. may be used herein to describe various parameters or modules, these parameters or modules should not be limited to these terms. These terms are only used to distinguish parameters or modules of the same type from each other. For example, without departing from the scope of this article, the first parameter may also be referred to as the second parameter, and similarly, the second parameter may also be referred to as the first parameter. Depending on the context, the words "if" and "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determination" or "in response to detection". Similarly, depending on the context, the phrase "if it is determined" or "if it is detected (statement of the condition or event)" may be interpreted as "when determining" or "in response to determination" or "when detecting (statement of the condition or event)" or "in response to detection (statement of the condition or event)". In addition, the components, features, and elements with the same name in different embodiments of the present application may have the same meaning, or may have different meanings, and their specific meanings need to be determined by their explanation in the specific embodiment or further combined with the context in the specific embodiment.

[0059] It should be understood that, although the various steps in the flowchart in the embodiment of the present application are displayed in sequence according to the indication of the arrows, these steps are not necessarily performed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and it can be performed in other orders. Moreover, at least a portion of the steps in the figure may include a plurality of sub-steps or a plurality of stages, and these sub-steps or stages are not necessarily performed at the same time, but can be performed at different times, and their execution order is not necessarily performed in sequence, but can be performed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0060] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the scope of rights of the present application.

[0061] The power conversion device can convert the input electrical energy into another form of electrical energy output to meet specific power demand. The power conversion device can be a direct current to alternating current, a direct current to direct current, or an alternating current to direct current. The power conversion device can also be a bidirectional power conversion device, that is, the first side of the power conversion device is the input side, and the second side is the output side; or the second side of the power conversion device is the input side, and the first side is the output side. The first side of the power conversion device is connected to the battery, and the second side of the power conversion device can be selectively connected to the power grid or the load. When the second side of the power conversion device is connected to the power grid, the high-voltage AC power of the power grid can be converted into low-voltage DC power and output to the battery to charge the battery. When the second side of the power conversion device is connected to the load, the low-voltage DC power of the battery can be converted into high-voltage AC power to power the load. Therefore, generally speaking, the first side of the power conversion device connected to the battery is the low-voltage side, and the second side of the power conversion device is the high-voltage side. When a power conversion device is used to charge or discharge a low-voltage battery, the current on the first side of the power conversion device is relatively large. When the current of the battery (the current on the first side of the power conversion device) is collected through a current sensor or an acquisition circuit, a larger acquisition range is required, resulting in a high cost of the current sensor or signal sampling circuit, and it is difficult to accurately obtain the battery charge and discharge current. For example, taking a 3KW power conversion device as an example, when it is connected to a 12V battery and inverted to output 220V AC, the current on the low-voltage side will be as high as 250A, and as the power consumption changes, the current on the low-voltage side may vary from tens of amperes to hundreds of amperes. This obviously places very high demands on the hardware current sampling device, and it often takes a high cost to configure a high-end current sensor to achieve accurate current sampling.

[0062] In view of the above technical problem, this embodiment provides a control method for a power conversion device. Figure 1 The present invention provides a flow chart of a control method for a power conversion device, which can be executed by a control unit, which includes at least one of a digital signal processor (DSP), a complex programmable logic device (CPLD), a field programmable gate array (FPGA), a central processing unit (CPU), or a microcontroller unit (MCU). Figure 1 As shown, the method includes:

[0063] Step S110: sampling and acquiring electrical parameters of the second side of the power conversion device.

[0064] The electrical parameter is a parameter related to the electric power input or output by the power conversion device at the second side, and may be at least one of a voltage value, a current value and a power value.

[0065] Specifically, since the voltage on the second side of the power conversion device is higher, when the output power of the power conversion device is constant, the current on the second side will be significantly smaller than the current on the first side, so a current sensor with a lower specification can be used to collect the current value on the second side of the power conversion device. For example, the current value on the second side of the power conversion device can be collected by a current sensor, an ammeter, a current transformer or a current acquisition circuit, and the voltage value on the second side of the power conversion device can be collected by a voltage sensor, a voltage transformer, a voltmeter or a voltage acquisition circuit. By collecting the voltage value and current value on the second side of the power conversion device, the power value on the second side of the power conversion device can be determined. In some other embodiments, the voltage value, current value and power value on the second side of the power conversion device can also be collected by a power device.

[0066] Step S120: determining an actual current value of the battery at least according to the electrical parameters of the second side, wherein the actual current value includes an actual charging current value or an actual discharging current value.

[0067] Specifically, the electrical parameters of the second side of the power conversion device are associated with the electrical parameters of the first side. For example, within a certain range, the larger the current on the second side, the larger the current on the first side. According to the electrical parameters of the second side and the associated relationship between the electrical parameters of the second side and the electrical parameters of the first side, the electrical parameters of the first side can be determined, that is, the electrical parameters of the battery are determined, so as to determine the actual current value of the battery. When the second side of the power conversion device is connected to a load, the battery is discharged, and the actual current value of the battery is the actual discharge current value. When the second side of the power conversion device is connected to the power grid, the AC power of the power grid is used to charge the battery, and the actual current value of the battery is the actual charging current value. In this way, there is no need to use a high-cost current sensor to collect the actual current value of the battery, and there is no need to consider the range of current collection, and the accuracy of current collection will not be reduced due to the range problem, which is conducive to improving the accuracy of battery current acquisition and conveniently determining the actual current of the battery.

[0068] Step S130: adjusting the operation of the power conversion device based on the actual current value.

[0069] Specifically, when the battery is charged or discharged, it is generally charged or discharged according to the target current value, and the target current value can be a preset fixed value or a value input by the user. The control unit will adjust the operation of the power conversion device according to the target current value and the actual current value, so that the charging current value or the discharging current value of the battery follows the target current value output, so that the current value of the battery is equal to or close to the target current value. Exemplarily, when the absolute value of the difference between the actual current value and the target current value is large, for example, when it is greater than a preset threshold, it indicates that the actual current value is greatly different from the target current value, and the control unit will adjust the operation of the power conversion device, for example, adjust the pulse width or frequency of the PWM drive signal output to the power switch tube in the power conversion device, adjust the output of the power conversion device, and thus adjust the current value of the battery, so that the battery operates according to the target current value, that is, operates according to the expected state, which is conducive to ensuring that the working state of the battery and the power conversion device is consistent with the expected state, thereby meeting different charging and discharging requirements.

[0070] The technical solution of this embodiment, by collecting the electrical parameters of the second side of the power conversion device, can determine the actual current value of the battery on the first side of the power conversion device at least based on the electrical parameters of the second side of the power conversion device, thereby eliminating the need to use a current collection device to collect the current value of the battery, facilitating the determination of the actual current value of the battery, reducing hardware costs, and improving the accuracy of determining the actual current value of the battery. At the same time, the operation of the power conversion device is adjusted based on the determined actual current value, which is beneficial to ensuring that the working state of the power conversion device is consistent with the expected state.

[0071] On the basis of the above technical solution, in step S120, there may be multiple ways to determine the actual current value of the battery at least based on the electrical parameters of the second side. The control method of the power conversion device is further explained below in combination with the specific method for determining the actual current value of the battery, but it is not intended to limit the present application.

[0072] In one embodiment, Figure 2 is a flowchart of another method for controlling a power conversion device provided by an embodiment of the present invention. Optionally, refer to Figure 2 , the control method of the power conversion device includes:

[0073] Step S210: sampling and acquiring a first voltage value and a first current value of a second side of the power conversion device.

[0074] Specifically, by acquiring the first voltage value and the first current value of the second side of the power conversion device, it is convenient to determine the current value of the first side of the corresponding power conversion device according to the first voltage value and the first current value, that is, to determine the actual current value of the battery.

[0075] When the power conversion device operates in the inverter output mode, the battery discharges to the load through the power conversion device, and the output power of the power conversion device at this time can be determined by sampling the voltage value and current value of the second side of the power conversion device. Alternatively, when the power conversion device operates in the rectifier charging mode, the input power of the power conversion device at this time can be determined by sampling the voltage value and current value of the second side of the power conversion device.

[0076] Step S220: sampling and acquiring the actual voltage value of the battery on the first side of the power conversion device.

[0077] Specifically, for example, the actual voltage value of the battery on the first side can be obtained by a voltmeter, a voltage sensor or a power device, so as to determine the actual current value of the battery on the first side based on the actual voltage value of the battery on the first side and the electrical parameters of the second side of the power conversion device.

[0078] Step S230: determine a first power value of the second side according to the first voltage value and the first current value.

[0079] Specifically, for example, the product of the first voltage value and the first current value is calculated, and the product is used as the first power value. For example, if the first voltage value is V1 and the first current value is I1, then the first power value P1=V1*I1. According to the law of conservation of energy, without considering the efficiency of the power conversion device, the input power and output power of the power conversion device should be the same; on the basis of considering the efficiency of the power conversion device, the input power and output power of the power conversion device also have a corresponding relationship. In this way, according to the correlation between the first power value of the second side and the power value of the first side, the power value of the first side can be determined, and then the actual current value of the battery can be determined according to the power value of the first side and the actual voltage value of the battery on the first side.

[0080] Step S240: determining the actual current value of the battery according to the actual voltage value of the battery, the conversion efficiency of the power conversion device and the first power value.

[0081] Specifically, the conversion efficiency of the power conversion device is the ratio of the output power of the power conversion device to the input power. Due to the power consumption and conversion loss of the power conversion device itself, the conversion efficiency is usually less than 1. The conversion efficiency can be determined according to the test results of the engineering prototype, and the conversion efficiency is stored in the memory of the control unit. The second power value of the battery can be determined according to the conversion efficiency of the power conversion device and the first power value, and the actual current value of the battery can be determined according to the second power value of the battery and the actual voltage value of the battery. In this way, the actual current value of the battery can be accurately calculated without the need to use hardware sensors to sample the battery current. In addition, the actual current value of the battery can be calculated in real time or periodically, which is convenient for obtaining the working state (charging and discharging state) of the battery, thereby adjusting the operation of the power conversion device.

[0082] Step S250: adjusting the operation of the power conversion device based on the actual current value.

[0083] Specifically, a PI current regulator or a PID current regulator can be used to control and adjust the operation of the power conversion device. The actual current value of the battery determined in step S240 is used as a feedback quantity, and the reference current value is used as a reference quantity for calculation. The obtained output signal acts on the power conversion device, and the power conversion device adjusts its operating state so that the actual current value of the battery approaches the reference current value.

[0084] On the basis of the above technical solution, optionally, step S240, determining the actual current value of the battery according to the actual voltage value of the battery, the conversion efficiency of the power conversion device and the first power value, includes:

[0085] Step a1: determine the power range in which the first power value is located.

[0086] Specifically, the first power value of the first side of the power conversion device is the input power value of the power grid or the power consumption value of the load. The power of the power grid or the load will fluctuate within a certain range, so there is a minimum power value and a maximum power value for operation. The power value between the minimum power value and the maximum power value can be divided into multiple different power ranges (or power segments), and the first power value can be compared with the boundary value of each power range to determine the power range in which the first power value is located. Under different power ranges, the efficiency of the power conversion device may be different, so a power-efficiency curve can be formed based on the test data of the engineering prototype, and then the full power is divided into different power ranges (or power segments) according to the efficiency value. In each power range, the power conversion device has the same or similar conversion efficiency, and the data is stored in the memory of the control unit.

[0087] Step a2: determining the actual current value of the battery according to the conversion efficiency of the power conversion device corresponding to the power range, the actual voltage value of the battery and the first power value.

[0088] Specifically, since different power ranges on the second side of the power conversion device correspond to different conversion efficiencies of the power conversion device, that is, each power range corresponds to a conversion efficiency, the conversion efficiency corresponding to the first power value can be determined according to the conversion efficiency mapping table corresponding to the pre-stored power range. The second power value of the battery can be determined according to the conversion efficiency of the power conversion device and the first power value, and the second power value of the battery is equal to the product of the conversion efficiency of the power conversion device and the first power value. The actual current value of the battery can be determined according to the second power value of the battery and the actual voltage value of the battery, and the actual current value of the battery is equal to the quotient of the second power value of the battery and the actual voltage value of the battery. In this way, since different charging (discharging) current ranges of the battery correspond to different power ranges of the power conversion device, and different power ranges correspond to different power ranges of the power grid input (or power conversion device output), it is possible to achieve accurate estimation of the battery charging current (or discharge current) by dynamically adjusting the conversion efficiency within different charging current ranges to meet different charging (or discharging) requirements.

[0089] Optionally, step S240, determining the actual current value of the battery according to the actual voltage value of the battery, the conversion efficiency of the power conversion device and the first power value, includes:

[0090] Step b1: determining a second power value of the first side of the power conversion device according to the conversion efficiency and the first power value.

[0091] Specifically, the conversion efficiency of the power conversion device is the ratio of the first power value to the second power value, so the second power value can be calculated based on the conversion efficiency and the first power value. For example, if the first power value is P1 and the conversion efficiency of the power conversion device is k, then the second power value is P2=k*P1.

[0092] Step b2: determining the actual current value of the battery according to the second power value and the actual voltage value of the battery.

[0093] Specifically, the second power value is the charging power or discharging power of the battery. The ratio of the second power value to the actual voltage value of the battery is calculated to be the actual current value of the battery. For example, if the actual voltage value of the battery is V2, then the actual current value of the battery is

[0094] In another embodiment, Figure 3 is a flowchart of another method for controlling a power conversion device provided by an embodiment of the present invention. Optionally, refer to Figure 3 , the control method of the power conversion device includes:

[0095] Step S310: sampling and acquiring a second current value of a second side of the power conversion device.

[0096] Specifically, for example, a current sensor can be used to obtain the second current value of the second side of the power conversion device. The voltage on the second side of the power conversion device is larger and the current is smaller. In this way, a power device with a smaller range can be used to obtain the second current. The hardware cost is low, and there will be no problem of large acquisition errors due to the larger range. This is beneficial to improving the accuracy of determining the actual current value of the battery.

[0097] It should be noted that, under the same operating state and at the same time, the second current value of the second side of the power conversion device is the same as the first current value, but different names are used to express different methods of determining the actual current values ​​of the batteries.

[0098] Step S320: Determine the actual current value of the battery according to the mapping relationship between the second current value of the second side and the battery current.

[0099] Specifically, as the current on the first side of the power conversion device changes, the current on the second side of the power conversion device will also change accordingly; as the current on the second side of the power conversion device changes, the current on the first side of the power device will also change accordingly, and the second current value on the second side of the power conversion device is associated with the battery current, that is, there is a mapping relationship. The actual current value of the battery can be determined based on the mapping relationship and the second current value on the second side. For example, the actual current value of the battery can be found by substituting the second current value into the mapping relationship.

[0100] Exemplarily, the mapping relationship can be stored in the memory of the control unit in the form of a formula, a table or a curve graph, or stored in a separate memory, and the control unit can find or calculate the actual current value of the battery by substituting the second current value into the mapping relationship. The mapping relationship can be determined according to the test results of the engineering prototype during the product design stage, and the mapping relationship is stored in the memory of the control unit.

[0101] Step S330: Adjust the operation of the power conversion device based on the actual current value.

[0102] Optionally, the mapping relationship between the second current value of the second side and the battery current is determined according to the following method:

[0103] Step f1, sampling the current value of the first side and the current value of the second side of the power conversion device respectively under test conditions.

[0104] Specifically, the test conditions include, for example, that the actual voltage of the battery is constant (i.e., the actual voltage of the battery is substantially unchanged), and the charging power or discharging power of the battery can also be controlled within a preset power range, which is not limited in this embodiment. For example, when the actual voltage of the battery is constant, the charging power (or discharging power) of the battery can be changed, and the current value of the first side and the current value of the second side of the power conversion device can be sampled multiple times to obtain multiple sets of current data.

[0105] Step f2: fitting a mapping relationship curve according to the current value of the first side and the current value of the second side.

[0106] Specifically, for example, a coordinate system is established, all the first-side current values ​​and the corresponding second-side current values ​​are placed in the coordinate system, and a mapping relationship curve of the first-side current value and the second-side current value is fitted according to multiple groups of first-side current values ​​and second-side current values. Wherein, when fitting the mapping relationship curve, all current data can be fitted together to obtain a mapping relationship curve, or it can be segmented fitting to obtain multiple mapping relationship curves. In some embodiments, when there is one mapping relationship curve, the second current value of the second side of the power conversion device is substituted into the mapping relationship curve to determine the actual current value of the battery. In this way, the speed of determining the actual current value of the battery can be improved. In some embodiments, when there are two mapping relationship curves, the current range of the second current value of the second side of the power conversion device is determined, thereby determining the mapping relationship curve corresponding to the second current value of the second side of the power conversion device, and the second current value is substituted into the corresponding mapping relationship curve to obtain the actual current value of the battery. In this way, the accuracy of determining the actual current value of the battery can be improved.

[0107] In addition, after fitting the mapping relationship curve, a mapping relationship expression (formula) can also be obtained according to the mapping relationship curve. When determining the actual current value of the battery, the second current value can be substituted into the mapping relationship expression to calculate the actual current value of the battery.

[0108] For example, Figure 4 is a schematic diagram of a current mapping relationship curve provided by an embodiment of the present invention, such as Figure 4 As shown, the horizontal axis is the current value of the first side (the current value of the battery), the vertical axis is the current value of the second side, curve ① is a curve chart of the actual current value of the first side and the current value of the second side, and curve ② is a fitted curve chart. The actual current value of the battery can be determined based on the fitted curve chart and the second current value. Alternatively, the mapping relationship between the current value of the first side and the current value of the second side can be determined based on the fitted curve, Figure 4 The corresponding mapping relationship is y = -1.7e -7 *x 4 +4.7e -5 *x 3 -0.0037*x 2 +0.12x-0.14, where x is the current value of the first side (the current value of the battery), and y is the current value of the second side. When determining the actual current value of the battery, it is only necessary to substitute the sampled second current value into the mapping relationship to calculate the actual current value of the battery.

[0109] In yet another embodiment, Figure 5is a flowchart of another method for controlling a power conversion device provided by an embodiment of the present invention. Optionally, refer to Figure 5 , the control method of the power conversion device includes:

[0110] Step S410: sampling and acquiring a first voltage value and a first current value of a second side of the power conversion device.

[0111] Step S420: sampling and acquiring the actual voltage value of the battery on the first side of the power conversion device.

[0112] Step S430: determining a first actual current value of the battery according to the actual voltage value of the battery, the conversion efficiency of the power conversion device, the first current value and the first voltage value.

[0113] Step S440: Determine a second actual current value of the battery according to a mapping relationship between the first current value of the second side and the battery current.

[0114] Step S450: determining the actual current value of the battery according to the first actual current value and the second actual current value.

[0115] Specifically, the first actual current value is the actual current value of the battery determined according to the actual voltage value of the battery, the conversion efficiency of the power conversion device, the first current value and the first voltage value, and the second actual current value is the actual current value of the battery determined according to the mapping relationship between the first current value of the second side and the battery current. Determining the actual current value of the battery according to the first actual current value and the second actual current value determined in two ways is conducive to improving the accuracy of determining the actual current value of the battery. Exemplarily, determining the actual current value of the battery according to the first actual current value and the second actual current value can be to calculate the weighted average of the first actual current value and the second actual current value, that is, the first actual current value and the second actual current value can be multiplied by different weight values. It can also be to calculate the arithmetic mean of the first actual current value and the second actual current value, which can improve the accuracy of the actual current value calculation of the battery and improve the calculation efficiency. It can also be to calculate the difference between the first actual current value and the second actual current value. If the difference is small, take the average of the first actual current value and the second actual current value. If the difference is large, recalculate the first actual current value and the second actual current value, which is conducive to improving the accuracy of the actual current value calculation of the battery.

[0116] Step S460: Adjust the operation of the power conversion device based on the actual current value.

[0117] On the basis of the above technical solution, optionally, determining the actual current value of the battery according to the first actual current value and the second actual current value includes:

[0118] The average of the first actual current value and the second actual current value is taken as the actual current value of the battery.

[0119] Specifically, the average of the first actual current value and the second actual current value is the arithmetic mean of the first actual current value and the second actual current value. By calculating the average of the first actual current value and the second actual current value as the actual current value of the battery, the error between the method of determining the battery current according to the conversion efficiency and the method of determining the battery current according to the mapping relationship can be reduced, thereby improving the accuracy of determining the actual current value of the battery. In addition, there is no need to spend more calculation time, which is conducive to improving the efficiency of determining the actual current value of the battery.

[0120] This embodiment also provides a power conversion device. Figure 6 Schematic diagram of a power conversion device provided by an embodiment of the present invention. Figure 6 As shown, the device includes: a collection unit 510 and a control unit 520; the collection unit 510 is configured to obtain electrical parameters of the second side of the power conversion device; the control unit 520 is configured to determine the actual current value of the battery at least according to the electrical parameters of the second side, and adjust the operation of the power conversion device based on the actual current value, wherein the actual current value includes an actual charging current value or an actual discharging current value.

[0121] The power conversion device provided in the embodiment of the present invention can execute the control method of the power conversion device provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method.

[0122] This embodiment also provides a power supply system. Figure 7 is a schematic diagram of a power supply system provided by an embodiment of the present invention, with reference to Figure 7 The power supply system includes a battery 10 and a power conversion device 20 provided in any of the above-mentioned embodiments; a first side of the power conversion device 20 is connected to the battery 10; a second side of the power conversion device 20 is connected to a power grid (not shown) for charging the battery 10 with the AC input power of the power grid; or, a second side of the power conversion device 20 is connected to a load 30 for converting the DC input power of the battery 10 into AC power to power the load 30. Figure 7 Only the case where the second side of the power conversion device 20 is connected to the load 30 is shown, but this is not limiting.

[0123] Specifically, when the second side of the power conversion device 20 is connected to the power grid, the power grid transmits AC input power to the power conversion device 20, and the power conversion device 20 converts the high-voltage AC input power of the power grid into low-voltage AC power to charge the battery 10. When the second side of the power conversion device 20 is connected to the load 30, the power conversion device 20 converts the low-voltage DC input power of the battery 10 into a higher-voltage AC power to supply power to the load 30. When the battery 10 is working (charging or discharging), the target current value is set, and the power conversion device 20 adjusts the working state of the power conversion device 20 according to the target current value and the actual current value, so that the current of the battery 10 follows the target current value, that is, the battery 10 works in the desired state. By determining the actual current value of the battery according to the control method of the power conversion device of any of the above-mentioned embodiments, the actual current value of the battery can be accurately determined, and the working state of the power conversion device 20 can be adjusted based on the actual current value, so that the working state of the power conversion device 20 can be accurately adjusted, which is conducive to better operation of the power supply system.

[0124] As a further implementation scheme of this embodiment, on the basis of the above technical scheme, Figure 8 is a schematic diagram of a power supply system provided by an embodiment of the present invention. Optionally, as Figure 8 As shown, the power conversion device 20 includes a first conversion unit 21 and a second conversion unit 22. The first conversion unit 21 is connected to the battery 10, and is used to convert the low-voltage DC power of the battery 10 into a high-voltage DC bus voltage, or convert the high-voltage DC bus voltage into a low-voltage DC power and input it into the battery 10. The second conversion unit 22 is connected between the first conversion unit 21 and the power grid or the load 30, and is used to convert the AC power of the power grid into a high-voltage DC bus voltage, or invert the high-voltage DC bus voltage output by the first conversion unit 21 into AC power to supply power to the load 30.

[0125] Specifically, the acquisition unit 510 of the power conversion device 20 is electrically connected to the second side of the power conversion device 20 (i.e., the power grid or the load end), and the acquisition unit 510 is electrically connected to the control unit 520 to collect electrical parameters of the second side of the power conversion device 20 and send them to the control unit 520; the acquisition unit 510 is also electrically connected to the DC bus of the power conversion device 20, for example, to the bus between the first conversion unit 21 and the second conversion unit 22. The acquisition unit 510 can collect electrical parameters of the DC bus (for example, at least one of the voltage value, the current value, and the power value) and send them to the control unit 520, so that the control unit 520 determines the actual current value on the battery 10 side at least according to the electrical parameters of the second side of the power conversion device 20, and adjusts the operation of the power conversion device 20 based on the actual current value.

[0126] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0127] In the present application, the same or similar terminology concepts, technical solutions and / or application scenario descriptions are generally described in detail only the first time they appear. When they appear again later, they are generally not repeated for the sake of brevity. When understanding the technical solutions and other contents of the present application, for the same or similar terminology concepts, technical solutions and / or application scenario descriptions that are not described in detail later, reference can be made to the previous related detailed descriptions.

[0128] In the present application, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0129] The various technical features of the technical solution of the present application can be arbitrarily combined. In order to make the description concise, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the present application.

[0130] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as above, and includes a number of instructions for a terminal device (which can be an electrical device or a network device, etc.) to execute the method of each embodiment of the present application.

[0131] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A control method for a power conversion device, characterized in that: The first side of the power conversion device is connected to a battery, and the second side of the power conversion device is selectively connected to a power grid or a load; the method comprises: Sampling and acquiring electrical parameters of the second side of the power conversion device; determining an actual current value of the battery at least according to the electrical parameter of the second side, wherein the actual current value includes an actual charging current value or an actual discharging current value; adjusting the operation of the power conversion device based on the actual current value; The sampling and obtaining of the electrical parameters of the second side of the power conversion device includes: Sampling and acquiring a first voltage value and a first current value of a second side of the power conversion device; The determining the actual current value of the battery at least according to the electrical parameter of the second side includes: Sampling and acquiring an actual voltage value of the battery on the first side of the power conversion device; determining a first power value of the second side according to the first voltage value and the first current value; The actual current value of the battery is determined according to the actual voltage value of the battery, the conversion efficiency of the power conversion device and the first power value.

2. The method according to claim 1, characterized in that Determining the actual current value of the battery according to the actual voltage value of the battery, the conversion efficiency of the power conversion device and the first power value includes: Determining a power range within which the first power value lies; The actual current value of the battery is determined according to the conversion efficiency of the power conversion device corresponding to the power range, the actual voltage value of the battery and the first power value.

3. The method according to claim 1, characterized in that Determining the actual current value of the battery according to the actual voltage value of the battery, the conversion efficiency of the power conversion device and the first power value includes: Determine a second power value of the first side of the power conversion device according to the conversion efficiency and the first power value; An actual current value of the battery is determined according to the second power value and an actual voltage value of the battery.

4. A control method for a power conversion device, characterized in that: The first side of the power conversion device is connected to a battery, and the second side of the power conversion device is selectively connected to a power grid or a load; the method comprises: Sampling and acquiring electrical parameters of the second side of the power conversion device; determining an actual current value of the battery at least according to the electrical parameter of the second side, wherein the actual current value includes an actual charging current value or an actual discharging current value; adjusting the operation of the power conversion device based on the actual current value; The sampling and obtaining of the electrical parameters of the second side of the power conversion device includes: Sampling and acquiring a second current value of a second side of the power conversion device; The determining the actual current value of the battery at least according to the electrical parameter of the second side includes: The actual current value of the battery is determined according to a mapping relationship between the second current value of the second side and the battery current.

5. The method according to claim 4, characterized in that The mapping relationship between the second current value of the second side and the battery current is determined according to the following method: Under test conditions, respectively sampling a first-side current value and a second-side current value of the power conversion device; A mapping relationship curve is fitted according to the first-side current value and the second-side current value.

6. A control method for a power conversion device, characterized in that: The first side of the power conversion device is connected to a battery, and the second side of the power conversion device is selectively connected to a power grid or a load; the method comprises: Sampling and acquiring electrical parameters of the second side of the power conversion device; determining an actual current value of the battery at least according to the electrical parameter of the second side, wherein the actual current value includes an actual charging current value or an actual discharging current value; adjusting the operation of the power conversion device based on the actual current value; The sampling and obtaining of the electrical parameters of the second side of the power conversion device includes: Sampling and acquiring a first voltage value and a first current value of a second side of the power conversion device; The determining the actual current value of the battery at least according to the electrical parameter of the second side includes: Sampling and acquiring an actual voltage value of the battery on the first side of the power conversion device; Determine a first actual current value of the battery according to the actual voltage value of the battery, the conversion efficiency of the power conversion device, the first current value and the first voltage value; Determining a second actual current value of the battery according to a mapping relationship between the first current value of the second side and the battery current; An actual current value of the battery is determined according to the first actual current value and the second actual current value.

7. The method according to claim 6, characterized in that Determining the actual current value of the battery according to the first actual current value and the second actual current value includes: An average value of the first actual current value and the second actual current value is used as the actual current value of the battery.

8. A power conversion device, characterized in that: A control method for a power conversion device for implementing any one of claims 1 to 7, wherein a first side of the power conversion device is connected to a battery, and a second side of the power conversion device is selectively connected to a power grid or a load; the power conversion device comprises: A collection unit, the collection unit is configured to obtain electrical parameters of the second side of the power conversion device; wherein the voltage of the second side of the power conversion device is greater than the voltage of the first side of the power conversion device; A control unit, the control unit being configured to determine an actual current value of the battery at least according to the electrical parameters of the second side, and to adjust the operation of the power conversion device based on the actual current value, wherein the actual current value includes an actual charging current value or an actual discharging current value.

9. A power supply system, characterized in that: comprising a battery and a power conversion device as claimed in claim 8; The first side of the power conversion device is connected to the battery; The second side of the power conversion device is connected to the power grid, and is used to charge the battery with the AC input power of the power grid; Alternatively, the second side of the power conversion device is connected to a load, and is used to convert the DC input power of the battery into AC power to supply power to the load.

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