Power conversion device

Abstract

A power conversion device according to an embodiment of the present invention comprises: a switching element; a temperature sensing element for measuring the temperature of the switching element; and a control unit for calculating an outdoor air temperature from the temperature measured by the temperature sensing element by using a temperature transfer function of the switching element, wherein the temperature transfer function represents an estimated temperature of the switching element according to output power.

Description

power conversion device

[0001] The present invention relates to a power conversion device, and more specifically, to a power conversion device that estimates the temperature of a switching element measured using a temperature sensing element, and an external temperature estimation method.

[0002] Solar power generation is becoming widely adopted as an eco-friendly energy source, replacing conventional chemical and nuclear power generation. Solar power generation can be either standalone, with a battery connected to a converter, or grid-connected. Standalone systems typically consist of photovoltaic panels, storage batteries, and power conversion equipment, while grid-connected systems connect to commercial power sources, enabling the exchange of power with the grid.

[0003] Power generated by solar power generation must generate as much power as possible, even during derating, when fed to the grid through an inverter. While a derating algorithm measures the temperature of specific areas within the product and designs the system to ensure that the set temperature is not exceeded, as the ambient temperature rises, the operating temperatures of other components may exceed the specified temperature range. If the ambient temperature exceeds the product's operating temperature specifications, the lack of ambient temperature information can make it difficult to protect the product at the point where operation is guaranteed. While ambient temperature data is necessary for product protection, attaching an external temperature sensor incurs additional costs to ensure the product's water and dust resistance.

[0004] The technical problem to be solved by the present invention is to provide a power conversion device that estimates the temperature of a switching element measured using a temperature sensing element and a method for estimating the external temperature.

[0005] In order to solve the above technical problem, a power conversion device according to one embodiment of the present invention includes: a switching element; a temperature sensing element that measures the temperature of the switching element; and a control unit that calculates an external temperature from the measured temperature of the temperature sensing element using a temperature transfer function of the switching element, wherein the temperature transfer function represents an estimated temperature of the switching element according to output power.

[0006] In addition, the control unit can calculate the outside temperature using the difference between the measured temperature of the temperature sensing element and the estimated temperature derived using the temperature transfer function.

[0007] In addition, the temperature transfer function can be derived using temperature saturation data of the switching element according to the output power of the power conversion unit.

[0008] In addition, the temperature transfer function can be derived by using the average of the first result and the second result obtained by applying the first filter and the second filter, which pass different bands, to the temperature saturation data, respectively.

[0009] In addition, the temperature transfer function can be derived by reflecting a correction factor according to the output power to the average of the first result and the second result.

[0010] Additionally, the switching element may be a switching element having the highest temperature among the switching elements of the power conversion device.

[0011] In addition, the control unit can control the switching element within an operating range according to the calculated external temperature.

[0012] In order to solve the above technical problem, an ambient temperature estimation method for estimating the ambient temperature of a power conversion device according to an embodiment of the present invention includes a step in which a temperature sensing element measures an element temperature of a switching element; a step in which a control unit calculates an estimated temperature of the switching element according to output power using a temperature transfer function; and a step in which the control unit calculates an ambient temperature from a measured temperature of the temperature sensing element using the estimated temperature of the switching element.

[0013] In addition, the step of calculating the outside temperature may be such that the control unit calculates the outside temperature using the difference between the measured temperature of the temperature sensing element and the estimated temperature derived using the temperature transfer function.

[0014] In addition, the temperature transfer function can be derived by calculating the average of the first result and the second result by applying a first filter and a second filter that pass different bands to the temperature saturation data of the switching element according to the output power of the power conversion unit, respectively, and reflecting a correction factor according to the output power to the calculated average of the first result and the second result.

[0015] Additionally, the switching element may be a switching element having the highest temperature among the switching elements of the power conversion device.

[0016] Additionally, the control unit may include a step of controlling the switching element within an operating range according to the calculated external temperature.

[0017] According to embodiments of the present invention, the ambient temperature can be estimated without an additional temperature sensor. Using the estimated ambient temperature, thermal management of components within the product can be facilitated. Furthermore, performing a derating operation based on the estimated ambient temperature can minimize power ripples due to temperature. Furthermore, the device can accurately implement a shutdown function to protect the device from heat, thereby increasing its lifespan. Furthermore, the device can satisfy water and dust resistance requirements and reduce the cost of additional equipment required to implement an external temperature measurement function.

[0018] Figure 1 is a block diagram of a power conversion device according to one embodiment of the present invention.

[0019] Figure 2 is a block diagram of a power conversion device according to an embodiment of the present invention.

[0020] FIGS. 3 to 5 are drawings for explaining a method for a power conversion device according to one embodiment of the present invention to estimate an external temperature.

[0021] Figure 6 is a flowchart of an outside temperature estimation method according to one embodiment of the present invention.

[0022] Figure 7 is a flowchart of an outside temperature estimation method according to an embodiment of the present invention.

[0023] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0024] However, the technical idea of ​​the present invention is not limited to some of the embodiments described, but can be implemented in various different forms, and within the scope of the technical idea of ​​the present invention, one or more of the components between the embodiments can be selectively combined or substituted for use.

[0025] In addition, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted as having a meaning that can be generally understood by a person of ordinary skill in the technical field to which the present invention belongs, unless explicitly and specifically defined and described, and terms that are commonly used, such as terms defined in a dictionary, may be interpreted in consideration of the contextual meaning of the relevant technology.

[0026] Additionally, the terms used in the embodiments of the present invention are intended to describe the embodiments and are not intended to limit the present invention.

[0027] In this specification, the singular may also include the plural unless specifically stated otherwise in the phrase, and when it is described as “A and / or at least one (or more) of B, C”, it may include one or more of all combinations that can be combined with A, B, C.

[0028] Additionally, in describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and are not intended to limit the nature, order, or sequence of the components.

[0029] And, when a component is described as being 'connected', 'coupled', or 'connected' to another component, it may include not only cases where the component is 'connected', 'coupled', or 'connected' directly to the other component, but also cases where the component is 'connected', 'coupled', or 'connected' by another component between the component and the other component.

[0030] Additionally, when described as being formed or arranged "above" or "below" each component, "above" or "below" includes not only cases where the two components are in direct contact with each other, but also cases where one or more other components are formed or arranged between the two components. Furthermore, when expressed as "above" or "below," the meaning may include not only the upward direction but also the downward direction based on one component.

[0031] Variations according to the present embodiment may include some components of each embodiment and some components of other embodiments. That is, a variation may include one embodiment among various embodiments, but may omit some components and include some components of the corresponding other embodiment. Or, the opposite may be true. The features, structures, effects, etc. to be described in the embodiments are included in at least one embodiment, and are not necessarily limited to just one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment may be combined or modified in other embodiments by a person having ordinary skill in the art to which the embodiments belong. Therefore, the contents related to such combinations and modifications should be interpreted as being included within the scope of the embodiments.

[0032] Figure 1 is a block diagram of a power conversion device according to one embodiment of the present invention.

[0033] FIG. 2 is a block diagram of a power conversion device according to an embodiment of the present invention, and FIGS. 3 to 5 are drawings for explaining a method for a power conversion device according to an embodiment of the present invention to estimate an external temperature.

[0034] A power conversion device (100) according to one embodiment of the present invention is composed of a switching element (110), a temperature sensing element (120), and a control unit (130), and may include an input unit (140), a power conversion unit (150), an output unit (160), a voltage measuring unit (not shown), a current measuring unit (not shown), and a storage unit (not shown).

[0035] A power conversion device (100) according to an embodiment of the present invention is a power conversion device that receives power from a PV module (200), converts it, and outputs it. It may be an inverter that receives power from the PV module (200). Alternatively, it may include a DC-DC converter, or another power conversion device that receives power, converts it, and outputs it.

[0036] According to an embodiment of the present invention, a power conversion device (100) can receive power through an input unit (140), and the input unit (140) can receive power from a PV module (210). The PV module (210) is a photovoltaic module, and may be a module that converts power generated by a photovoltaic panel and the photovoltaic panel into power suitable for a load or a battery. It can be expressed as a solar module, a solar power generation module, etc. The PV panel includes a plurality of cell strings. A solar cell that performs solar power generation can be expressed as a cell string unit in which a plurality of cells are connected in series.

[0037] A cell string may include at least one cell, and when including multiple cells, the multiple cells may be connected in series. The cell string may be a solar cell string including solar cells. The solar cell string may form a photovoltaic (PV) panel. A PV panel may also be referred to as a solar panel or solar power generation panel. Solar cells generate solar power (PV) by utilizing the photovoltaic effect. The photovoltaic effect is the emission of electrons when light above a certain frequency strikes a specific metal material. A pn ​​junction is formed using a p-type semiconductor and an n-type semiconductor, and the electrons generated by the photovoltaic effect are used to generate current, thereby generating power. Solar cells are formed using silicon or other materials and may be formed in a wafer form. Solar cells are located in fields that can receive a lot of sunlight, on the exterior walls of buildings, on rooftops, etc., and generate power using sunlight. In this case, the solar cells may be formed as BIPV (Building Integrated Photovoltaics) that are formed integrally with the building.

[0038] Since the amount of power generated from a single solar cell is insufficient to be utilized by a load or power system, power suitable for utilization can be generated by connecting multiple solar cells in series to form a solar cell string instead of a single solar cell. A solar cell string can be a basic unit for generating power. A photovoltaic panel can be formed by forming multiple cell strings, which are basic units, into a panel. Solar cells have different voltage-current characteristics depending on the amount of sunlight, temperature, etc., and the maximum power point (MPP) also changes. (Generated power = Voltage X Current)

[0039] The PV module (210) may include a Module-Level Power Electronics (MLPE). Alternatively, it may include an optimizer. The MLPE may control the solar cell to operate at the maximum power point (MPP), which is the operating point where the power of the solar cell is maximum under each condition. This is called maximum power point tracking (MPPT), and the efficiency of solar power generation can be improved by using maximum power point tracking. In solar power generation, depending on the characteristics of the relationship between current and voltage and the relationship between voltage and power, the maximum power may be the power when the voltage is about 80% of the maximum voltage, not the maximum voltage. Since this maximum power point continuously changes depending on the magnitude of the voltage and current generated by the photovoltaic panel, a point where the maximum power point can be generated must be continuously searched. In other words, in order to track the maximum power, not the maximum voltage, the magnitude of the voltage and current can be varied so as to achieve the maximum power. That is, the voltage can be reduced and the current increased in the direction of increasing power, or the voltage can be increased and the current can be reduced.

[0040] The power input to the input unit (140) can be converted and output by the power conversion unit (150). The power conversion unit (150) can supply power to an energy storage system (ESS) including a battery or a grid (grid, 220) through the output unit (160).

[0041] The power conversion unit (150) includes a switching unit, and the switching unit includes a switching element (110). The control unit (130) can control the switching element (110) by applying a PWM signal to it.

[0042] The temperature sensing element (120) measures the temperature of the switching element (110). The temperature sensing element (120) may include a thermistor, an NTC (Negative Temperature Coefficient of Resistance), or a PTC (Positive Temperature Coefficient of Resistance). An NTC is a resistor whose resistance value decreases when the temperature rises, and a PTC is a resistor whose resistance value increases when the temperature rises. The temperature sensing element (120) can measure the temperature of the switching element (110) using an NTC.

[0043] The control unit (130) may perform derating control to ensure stable operation when controlling the switching element (110). Derating refers to using the element under conditions lower than the rated value in order to operate the element and system safely and reliably. The control unit (130) may control the switching element (110) within an operating range according to temperature through derating curve control. Here, the control unit (130) may use the temperature of a component corresponding to a critical point among the components, and the critical point may be the switching element (110) of the power conversion unit (150). Here, the switching element (110) may be a power semiconductor switching element or a MOSFET. The switching element with the highest temperature among the switching elements may be used as the critical point. A power limit function may be set for the temperature of the critical point. If the temperature of the critical point is higher than the first critical temperature, power can be limited according to the power limiting function, and if the second critical temperature is reached, the product can be stopped. In this case, if only the temperature of the switching element (110), which is the critical point, is used, the influence of the ambient temperature on the temperature cannot be determined, and since the ambient temperature is not known, components other than the critical component may not be protected from heat.

[0044] Instead of using a power limit function, a high threshold and a low threshold are set for the temperature of the critical point, and the power is limited at a certain rate when the temperature of the critical point is higher than the high threshold, and the power is released at a certain rate when it is lower than the low threshold. However, since the power is limited discontinuously according to the temperature measurement cycle, the power ripple is relatively large, which may have some adverse effects on the system. In addition, since it is difficult to estimate the external temperature, it may not be possible to protect parts other than the relevant part from heat.

[0045] To solve this, the control unit (130) calculates the outside temperature from the measured temperature of the temperature sensing element (120) using the temperature transfer function of the switching element (110). The control unit (130) may include one or more processors and a storage unit. The storage unit may include a temperature transfer function and a power limiting function, and the processor may calculate the outside temperature from the measured temperature of the temperature sensing element (120) using the temperature transfer function and perform derating control using the power limiting function.

[0046] The control unit (130) can receive the measured temperature of the switching element (110) from the temperature sensing element (120) or calculate the measured temperature of the switching element (110) using the output value of the temperature sensing element (120). The control unit (130) can calculate the outside temperature from the measured temperature of the temperature sensing element (120) using a temperature transfer function. The control unit (130) can calculate the outside temperature using the difference between the measured temperature of the temperature sensing element (120) and the estimated temperature derived using the temperature transfer function. That is, the control unit (130) can calculate the outside temperature by subtracting the estimated temperature from the measured temperature. The control unit (130) can control the power conversion unit (150) using a derating curve method of control according to the calculated outside temperature.

[0047] The temperature transfer function is a function that represents the estimated temperature of the switching element (110) according to the output power. The estimated temperature of the switching element (110) may be a temperature that occurs only by the heat generation of the switching element (110) without being affected by the outside temperature. The measured temperature of the switching element (110) measured by the temperature sensing element (120) is the temperature obtained by adding the outside temperature and the temperature caused by the heat generation of the switching element (110), and the outside temperature can be estimated by subtracting the estimated temperature from the measured temperature.

[0048] The temperature transfer function can be derived by calculating the average of the first result and the second result by applying a first filter and a second filter that pass different bands to the temperature saturation data of the switching element (110) according to the output power of the power conversion unit (150) of the power conversion device, and reflecting a correction factor according to the output power to the average of the calculated first result and the second result.

[0049] The temperature transfer function is derived in the same manner as in Fig. 3, and the estimated temperature of the switching element (110) can be calculated through this.

[0050] Temperature saturation data is measured by comparing the temperature saturation data of the switching element (110) with the room temperature according to the power. As shown in Fig. 4, the temperature saturation data can be derived by measuring the saturated temperature according to the output power compared to the maximum output power through an experiment. The temperature saturation data includes a fitting curve, and the temperature saturation data can be derived by linearizing the slope to a natural constant e, or by using a mathematical formula of a first- or second-order function, or by creating a table data of the saturation temperature for each power.

[0051] The temperature transfer function can be derived by using the average of the first and second results obtained by applying a first filter and a second filter having different bands to the temperature saturation data, respectively. Here, the first and second filters may be low-pass filters (LPFs) that pass through different bands. The temperature saturation data changes according to the amount of change in power, and the temperature change may be fast at low power and slow at high power, so there may be differences in the temperature change for each section. In order to closely approximate this to the actual temperature, the data may be passed through two filters having different bands, the results may be added, and then the average may be derived by multiplying by 0.5. The average of the two results may be derived by reflecting a correction factor (K_power) according to the output power. The correction factor is a correction value that compensates for an error that occurs depending on the actual output power. By reflecting this, the final temperature transfer function can be derived, and currently, the estimated temperature of the switching element (110) can be calculated using the power output from the power conversion unit (150).

[0052] The control unit (130) can calculate the outside temperature using the following equation.

[0053] T_Amb = T_Cripnt - T_Est

[0054] The outside temperature T_Amb can be calculated by using the difference between the measured temperature T_CriPnt of the temperature sensing element for the switching element (110), which is a critical point in the power conversion device (100), and the result value T_Est of the temperature transfer function.

[0055] The output power of the power conversion unit (150) can be calculated by measuring the voltage and current of the output unit (160). The voltage and current of the output unit (160) may include a voltage measuring unit or a current measuring unit, and may include a voltage sensor or a current sensor.

[0056] The control unit (130) can control the switching element (110) within an operating range according to the calculated external temperature. The control unit (130) can control the switching element (110) in a temperature derating curve manner according to the calculated external temperature. The control unit (130) can set a power limiting function according to the external temperature. For example, as shown in FIG. 5, a first threshold temperature (AmbThr_L) and a second threshold temperature (AmbThr_H) can be set. When the external temperature is higher than the first threshold temperature, the power can be limited according to the power limiting function, and when the second threshold temperature is reached, the product can be stopped.

[0057] According to the measurement results according to the outside temperature estimation method, when the outside temperature estimation value was 26.6 degrees, the outside temperature measurement value was 28.9 degrees, with an error of -2.3 degrees. This confirmed that the outside temperature could be accurately estimated within the error range of 5 degrees or less.

[0058] As described above, by estimating the temperature of a switching element measured using a temperature sensing element, the ambient temperature can be estimated without an additional temperature sensor. Using the estimated ambient temperature facilitates thermal management of components within the product. Furthermore, performing derating based on the estimated ambient temperature can minimize power ripple due to temperature. Furthermore, the device can accurately implement a shutdown function to protect the device from heat, thereby extending its lifespan. Furthermore, it satisfies water and dust resistance requirements and reduces the cost of additional equipment required to implement an external temperature measurement function.

[0059] Fig. 6 is a flowchart of an outside temperature estimation method according to one embodiment of the present invention, and Fig. 7 is a flowchart of an outside temperature estimation method according to an embodiment of the present invention. Detailed descriptions of each step of Figs. 6 and 7 correspond to the detailed descriptions of the power conversion devices of Figs. 1 to 5, and thus, any redundant descriptions will be omitted below.

[0060] In order to estimate the outside temperature, in step S11, a temperature sensing element measures the element temperature of a switching element, in step S12, a control unit calculates an estimated temperature of the switching element according to the output power using a temperature transfer function, and in step S13, the control unit calculates the outside temperature from the measured temperature of the temperature sensing element using the estimated temperature of the switching element.

[0061] In calculating the outside temperature at step S13, the control unit can calculate the outside temperature using the difference between the measured temperature of the temperature sensing element and the estimated temperature derived using the temperature transfer function.

[0062] The temperature transfer function can be derived by calculating the average of the first result and the second result by applying a first filter and a second filter that pass different bands to the temperature saturation data of the switching element according to the output power of the power conversion unit, and reflecting a correction factor according to the output power to the calculated average of the first result and the second result.

[0063] The switching element measuring the element temperature at step S11 may be the switching element having the highest temperature among the switching elements of the power conversion device.

[0064] When the outside temperature is estimated at step S13, the control unit can control the switching element within an operating range according to the calculated outside temperature at step S21.

[0065] As described above, by estimating the temperature of a switching element measured using a temperature sensing element, the ambient temperature can be estimated without an additional temperature sensor. Using the estimated ambient temperature facilitates thermal management of components within the product. Furthermore, performing derating based on the estimated ambient temperature can minimize power ripple due to temperature. Furthermore, the device can accurately implement a shutdown function to protect the device from heat, thereby extending its lifespan. Furthermore, it satisfies water and dust resistance requirements and reduces the cost of additional equipment required to implement an external temperature measurement function.

[0066] Meanwhile, embodiments of the present invention can be implemented as computer-readable code on a computer-readable recording medium. Computer-readable recording media include all types of recording devices that store data that can be read by a computer system.

[0067] Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices. In addition, the computer-readable recording media can be distributed across network-connected computer systems, so that computer-readable code can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the present invention can be easily inferred by programmers in the technical field to which the present invention pertains.

[0068] Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from the essential characteristics of the above-described description. Therefore, the disclosed methods should be considered illustrative rather than restrictive. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

Claims

1. Switching element; A temperature sensing element for measuring the temperature of the above switching element; and It includes a control unit that calculates the outside temperature from the measured temperature of the temperature sensing element using the temperature transfer function of the switching element, The above temperature transfer function is, A power conversion device that indicates the estimated temperature of the switching element according to the output power.

2. In paragraph 1, The above control unit, A power conversion device that calculates the outside temperature by using the difference between the measured temperature of the temperature sensing element and the estimated temperature derived using the temperature transfer function.

3. In paragraph 1, The above temperature transfer function is, A power conversion device derived by using temperature saturation data of the switching element according to the output power of the power conversion device.

4. In paragraph 3, The above temperature transfer function is, A power conversion device derived by using the average of the first result and the second result by applying the first filter and the second filter which pass different bands to the above temperature saturation data, respectively.

5. In paragraph 4, The above temperature transfer function is, A power conversion device derived by reflecting a correction factor according to the output power to the average of the first result and the second result.

6. In paragraph 1, The above switching element, A power conversion device having the highest temperature among the switching elements of the above power conversion device.

7. In paragraph 1, The above control unit, A power conversion device that controls the switching element within an operating range according to the above-described calculated external temperature.

8. In the method for estimating the external temperature of a power conversion device, A step in which a temperature sensing element measures the element temperature of a switching element; A step in which the control unit calculates the estimated temperature of the switching element according to the output power using the temperature transfer function; and An outside temperature estimation method, comprising a step of the above control unit calculating the outside temperature from the measured temperature of the temperature sensing element using the estimated temperature of the switching element.

9. In paragraph 8, The steps for calculating the above outside temperature are: An outside temperature estimation method in which the above control unit calculates the outside temperature by using the difference between the measured temperature of the temperature sensing element and the estimated temperature derived using the temperature transfer function.

10. In paragraph 8, The above temperature transfer function is, A method for estimating the ambient temperature, wherein the average of the first result and the second result is calculated by applying a first filter and a second filter that pass different bands to the temperature saturation data of the switching element according to the output power of the power conversion device, and the average of the first result and the second result is reflected in the average of the first result and the second result according to the output power.

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