Power conversion device

Abstract

A power conversion device according to one embodiment of the present invention comprises: a plurality of power conversion units connected in parallel, each including a switching unit; and a control unit for controlling the plurality of power conversion units through pulse width modulation (PWM), wherein the control unit individually controls the pulse width of output signals of the switching unit of each of the plurality of power conversion units.

Description

power conversion device

[0001] The present invention relates to a power conversion device, and more specifically, to a power conversion device capable of balancing output between a plurality of power conversion units and reducing ripple.

[0002] Rapid chargers for electric vehicles support high-speed charging at hundreds of kilowatts. They consist of power modules with capacities of tens of kilowatts, connected in parallel, and output a large amount of power. When connected to an electric vehicle, the power modules receive AC power from the grid and output DC power to charge the electric vehicle's battery.

[0003] Rapid chargers utilize multiple power modules to output large capacities. However, the resonant inductors or capacitors in the resonant circuits within the power modules may vary in tolerance, resulting in differences in output power between power modules.

[0004] The technical problem to be solved by the present invention is to provide a power conversion device capable of balancing output between multiple power conversion units and reducing ripple.

[0005] In order to solve the above technical problem, a power conversion device according to one embodiment of the present invention includes a plurality of power conversion units connected in parallel, each including a switching unit; and a control unit that controls the plurality of power conversion units by PWM (pulse width modulation), wherein the control unit individually controls the pulse width of an output signal of a switching unit of each of the plurality of power conversion units.

[0006] In addition, the control unit may be configured to have the switching frequency of the output signal of each switching unit of the plurality of power conversion units be the same, and the phase difference between the output signals of each switching unit of the plurality of power conversion units may have a preset phase difference.

[0007] In addition, the phase difference between the output signals of each switching unit of the plurality of power conversion units may vary depending on the number of power conversion units included in the plurality of power conversion units.

[0008] In addition, the phase difference between the output signals of each switching unit of the plurality of power conversion units can be set as the difference between the centers of the pulse widths of the output signals of each switching unit of the plurality of power conversion units.

[0009] In addition, the plurality of power conversion units may include a first power conversion unit and a second power conversion unit, and the phase difference between the output signal of the switching unit of the first power conversion unit and the output signal of the switching unit of the second power conversion unit may be 90 degrees.

[0010] In addition, the switching unit of each of the plurality of power conversion units includes at least one upper switch and at least one lower switch that are connected in series and complementarily conduct each other, and the pulse width of the output signal of the switching unit of each of the plurality of power conversion units can vary depending on the duty value of the upper switch.

[0011] In addition, it may include a plurality of first monitoring units that measure at least one of the output voltage, output current, and output power of each of the plurality of power conversion units.

[0012] In addition, it may include a plurality of second monitoring units that measure at least one of the input voltage, input current, and input power of each of the plurality of power conversion units.

[0013] In addition, it may include a plurality of first monitoring units that measure at least one of the output voltage, output current, and output power of each of the plurality of power conversion units; and a plurality of second monitoring units that measure at least one of the input voltage, input current, and input power of each of the plurality of power conversion units.

[0014] In addition, each of the plurality of power conversion units may include a switching unit that receives a direct current voltage as input, converts it into an alternating voltage, and outputs it; a resonance unit that converts the output of the switching unit using resonance; a transformer that converts the output of the resonance unit; and a rectifier that rectifies the output of the transformer unit into a direct current voltage.

[0015] Additionally, each of the plurality of power conversion units may include a resonant LLC converter.

[0016] In addition, the control unit can control the pulse width of the output signal of the switching unit of each of the plurality of power conversion units so that the output power output from each of the plurality of power conversion units is the same.

[0017] According to embodiments of the present invention, the output between multiple power conversion units connected in parallel can be balanced. Furthermore, ripple can be reduced by controlling the switching frequency of the multiple power conversion units to be the same.

[0018] FIG. 1 illustrates a power conversion device according to one embodiment of the present invention.

[0019] FIGS. 2 to 8 are drawings for explaining the operation of a power conversion device according to an embodiment of the present invention.

[0020] Figures 9 to 13 are circuit implementation examples of a power conversion device according to an embodiment of the present invention.

[0021] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] Fig. 1 illustrates a power conversion device according to an embodiment of the present invention. Figs. 2 to 8 are drawings for explaining the operation of a power conversion device according to an embodiment of the present invention, and Figs. 9 to 13 are circuit implementation examples of a power conversion device according to an embodiment of the present invention.

[0030] A power conversion device (100) according to one embodiment of the present invention is composed of a plurality of power conversion units (110) and a control unit (120), and may include a monitoring unit.

[0031] A power conversion device (100) according to an embodiment of the present invention may be a power conversion device of an electric vehicle charging device. Here, the power conversion device (100) may be a power module of the electric vehicle charging device. The power module may receive AC power from a grid (50 / 60 Hz), convert it into DC power for charging an electric vehicle battery, and output it. Alternatively, the power module may receive DC power from an energy storage system (ESS), convert it into DC power for charging a battery, and output it. Power may be received from an external power source such as a solar power generation module. The power module may include an AC-DC rectifier and a DC-DC converter, and the power conversion device (100) according to an embodiment of the present invention may be an isolated DC-DC converter, which may be a resonant LLC converter. In addition, the power conversion device may include a CLLC resonant converter, a DAB (Dual Active Bridge) converter, or a buck converter, a boost converter, or a buck-boost converter among non-isolated DC-DC converters.

[0032] A plurality of power conversion units (110) may be connected in parallel and each may include a switching unit (141). The plurality of power conversion units (110) may be connected in parallel to receive input power (210), convert it, and output it. The input power (210) may be the output of an AC-DC rectifier. The AC-DC rectifier may output the AC power input from the outside as DC power. The input input power (210) may be converted into a square wave form through the switching unit (141).

[0033] Each power conversion unit (110) may include a switching unit (141), a resonant unit (142), a transformer unit (143), and a rectifier unit (144). Each power conversion unit (110) may include a resonant LLC converter, and as shown in FIG. 2, the switching unit (141), the resonant unit (142), the transformer unit (143), and the rectifier unit (144) may be connected in that order. The input power (210) may be transmitted through the switching unit (141), the resonant unit (142), the transformer unit (143), and the rectifier unit (144) and output to a battery (220) connected to the output side to charge the battery (220).

[0034] The switching unit (141) can convert the input DC voltage, which is the input power, into an AC voltage in the form of a square wave and output it to the resonant unit (142). The resonant unit (142) can convert the voltage and current, which are the outputs of the switching unit (141), into AC voltage and AC current by using resonance before being applied to the transformer unit (143). The frequency of the resonant circuit of the resonant unit (142) is adjusted to match the switching frequency of the switching unit (141), so that the switch of the switching unit (141) can be turned on and off at zero voltage or zero current, thereby reducing switching loss and improving efficiency. The transformer unit (143) can convert the voltage or current input from the resonant unit (142) and output it to the rectifier unit (144). The rectifier unit (144) can rectify the AC voltage or current input from the transformer unit (143) and output DC power.

[0035] Switching loss can be reduced by utilizing the resonance of the resonant unit (142), but when using multiple power conversion units (110) connected in parallel, output differences may occur due to tolerances of the elements constituting the resonant circuit of the resonant unit (142) of each power conversion unit. This may result in an imbalance in output between the multiple power conversion units (110), which may reduce efficiency and place a burden on a specific power conversion unit (110), which may cause failure.

[0036] The control unit (120) can control a plurality of power conversion units (110) by PWM (pulse width modulation). The control unit (120) can individually control the pulse width of the output signal of each switching unit (141) of the plurality of power conversion units (110). The control unit (120) can individually control the pulse width of the square wave output from the switching unit (141) for each power conversion unit (110).

[0037] The switching unit (141) may include one or more upper switches and one or more lower switches that are connected in series and complementarily conduct. The pulse width of the output signal of each switching unit (141) of the plurality of power conversion units (110) may vary depending on the duty value of the upper switch. The control unit (120) may control the pulse width of the square wave output from the switching unit (141) by controlling the duty of the switching unit (141).

[0038] When controlled with the same pulse width, the output of each power conversion unit (110) may be different, which may cause an imbalance in the output. The control unit (120) may control the output between power conversion units to be the same by reducing the pulse width of a power conversion unit with a large output, increasing the pulse width of a power conversion unit with a small output, or reducing the pulse width of a power conversion unit with a large output and increasing the pulse width of a power conversion unit with a small output. Through this, the imbalance in the output between multiple power conversion units (110) may be resolved.

[0039] The control unit (120) can control the switching frequency of the output signal of each switching unit (141) of the plurality of power conversion units (110) to be the same, and the phase difference between the output signals of each switching unit (141) of the plurality of power conversion units (110) to have a preset phase difference.

[0040] The switching frequency of a square wave can be measured as the frequency between rising edges or falling edges, and the phase difference between square waves can be measured as the phase between the centers of the pulse widths of each square wave.

[0041] When there is a switching operation of the switching unit (141), a ripple may occur in which the output voltage fluctuates, and when multiple power conversion units (110) are used, the ripple may increase. In order to reduce the ripple, the control unit (120) may control the switching frequency of each switching unit (141) of the multiple power conversion units (110) to be the same, and may control the phase difference to have a preset phase difference.

[0042] The phase difference between the output signals of each switching unit of the plurality of power conversion units (110) may vary depending on the number of power conversion units included in the plurality of power conversion units (110). The plurality of power conversion units (110) may be controlled to include times when they are turned on without overlapping, in order to reduce ripple. For example, they may operate in an interleaving manner. In this case, the phase difference may be set to a number obtained by dividing 180 degrees by the number of power conversion units included in the plurality of power conversion units (110). For example, when the number of power conversion units included in the plurality of power conversion units (110) is two, the phase difference between the switching units (141) of the two power conversion units (110) can be set to 180 / 2=90 degrees, and when the number of power conversion units included in the plurality of power conversion units (110) is three, the phase difference between the switching units (141) of the three power conversion units (110) can be set to 180 / 3=60 degrees.

[0043] Here, the phase difference between the output signals of each switching unit (141) of the plurality of power conversion units (110) can be set as the difference between the centers of the pulse widths of the output signals of each switching unit (141) of the plurality of power conversion units (110).

[0044] In the case where a plurality of power conversion units (110) include two power conversion units, a first power conversion unit (111) and a second power conversion unit (112), the phase difference between the output signal of the switching unit (141) of the first power conversion unit (111) and the output signal of the switching unit (141) of the second power conversion unit (112) may be 90 degrees. The square wave output from each switching unit (141) may be as shown in FIG. 3, and the control unit (120) may individually control each switching unit (141) so as to have a pulse width of the square wave output from each switching unit (141). The pulse width (431) of the first power conversion unit (111) with a low output may be controlled to be large, and the pulse width (432) of the second power conversion unit (112) with a high output may be controlled to be small. At this time, the switching frequency (411) of the first power conversion unit (111) and the switching frequency (412) of the second power conversion unit (112) are controlled to be the same, and the phase difference (421) between the centers of the pulse widths of the two power conversion units (110) can be controlled to 90 degrees. Through this, the imbalance of the output between the power conversion units can be resolved and the ripple can be reduced.

[0045] In order to determine the imbalance of output between multiple power conversion units (110), a monitoring unit may be included. The monitoring unit may measure at least one of voltage, current, and power. The monitoring unit may include at least one of a voltage sensor and a current sensor. The control unit (120) may use the values ​​measured by the monitoring unit to control the measured values ​​so that they become target values. At this time, the control unit (120) may use the measured values ​​to control the pulse width of the output signal of the switching unit (141) of each power conversion unit (110).

[0046] The monitoring unit may include a first monitoring unit (130) connected to an output terminal of the power conversion unit, a second monitoring unit (150) connected to an input terminal of the power conversion unit, or a first monitoring unit (130) connected to an output terminal of the power conversion unit and a second monitoring unit (150) connected to an input terminal of the power conversion unit.

[0047] The first monitoring unit (130) can measure at least one of the output voltage, output current, and output power of each of the plurality of power conversion units (110). As shown in Fig. 4, the first monitoring units (131, 132) are respectively connected to the output terminals of each power conversion unit (110) to measure the output voltage, output current, and output power and transmit them to the control unit (120). The control unit (120) can determine voltage imbalance using the output power of each power conversion unit (110) received, and can individually control the pulse width of the output signal of the switching unit (141) of each power conversion unit (110) using the output power of each power conversion unit (110) received.

[0048] The second monitoring unit (150) can measure at least one of the input voltage, input current, and input power of each of the plurality of power conversion units (110). As shown in Fig. 5, the second monitoring units (151, 152) are respectively connected to the input terminals of each power conversion unit (110) to measure the input voltage, input current, and input power and transmit them to the control unit (120). The control unit (120) can determine voltage imbalance using the input power of each power conversion unit (110) received, and can individually control the pulse width of the output signal of the switching unit (141) of each power conversion unit (110) using the input power of each power conversion unit (110) received.

[0049] In addition, both the first monitoring unit (130) and the second monitoring unit (150) may be included. As shown in Fig. 6, the first monitoring unit (131, 132) is connected to the output terminal of each power conversion unit (110) to measure the output voltage, output current, and output power and transmit them to the control unit (120), and the second monitoring unit (151, 152) is connected to the input terminal of each power conversion unit (110) to measure the input voltage, input current, and input power and transmit them to the control unit (120). By using the first monitoring unit (130) and the second monitoring unit (150), it is possible to distribute the measurement function or confirm whether the measured information is correct. The control unit (120) can determine voltage imbalance using the input power of each power conversion unit (110) received, and can individually control the pulse width of the output signal of the switching unit (141) of each power conversion unit (110) using the input power of each power conversion unit (110) received.

[0050] The control unit (120) can control the pulse width of the output signal of the switching unit (141) of each of the plurality of power conversion units (110) so that the output power output from each of the plurality of power conversion units (110) is the same.

[0051] The outputs of multiple power conversion units (110) whose inputs are connected in parallel can be connected in parallel or in series. As shown in Fig. 7, the inputs of the first power conversion unit (111) and the second power conversion unit (112) are connected in parallel, and the outputs can also be connected in parallel. The first power conversion unit (111) and the second power conversion unit (112) can each receive input power (210), convert it into the rated voltage of the load battery (220), and output it.

[0052] In addition, as shown in Fig. 8, the inputs of the first power conversion unit (111) and the second power conversion unit (112) may be connected in parallel, and the outputs may be connected in series. The first power conversion unit (111) and the second power conversion unit (112) each receive input power (210) and output it, and the respective outputs may be connected in series and combined to output the output in accordance with the rated voltage of the battery (220), which is a load. When the voltage output from each power conversion unit (110) is lower than the rated voltage of the battery (220), the two outputs may be combined in series to match the rated voltage of the battery (220).

[0053] When the outputs of the first power conversion unit (111) and the second power conversion unit (112) are connected in parallel and the outputs of the first power conversion unit (111) and the second power conversion unit (112) are unequal, the control unit (120) can control the outputs between the power conversion units to be equal by reducing the pulse width of the power conversion unit with a large output, increasing the pulse width of the power conversion unit with a small output, or reducing the pulse width of the power conversion unit with a large output and increasing the pulse width of the power conversion unit with a small output. Through this, the imbalance in the outputs of the first power conversion unit (111) and the second power conversion unit (112) can be resolved.

[0054] When the outputs of the first power conversion unit (111) and the second power conversion unit (112) are connected in series and the outputs of the first power conversion unit (111) and the second power conversion unit (112) are unequal, the control unit (120) can control the outputs between the power conversion units to be equal by increasing the pulse width of the power conversion unit with a smaller output. Through this, when modulating the pulse width to resolve the imbalance in the outputs of the first power conversion unit (111) and the second power conversion unit (112), it is possible to prevent the final output voltage from becoming lower than the rated voltage of the battery (220) by reducing the pulse width.

[0055] Within the range of forming the rated voltage of the battery (220), the pulse width of a power conversion unit with a large output can be reduced, the pulse width of a power conversion unit with a small output can be increased, or the pulse width of a power conversion unit with a large output can be reduced and the pulse width of a power conversion unit with a small output can be increased to control the output between the power conversion units to be the same. Through this, the imbalance in the output of the first power conversion unit (111) and the second power conversion unit (112) can be resolved.

[0056] Each power conversion unit (110) can be configured as shown in Fig. 9. It can include a switching unit (141) including a plurality of switches, a resonant unit (142) forming a resonant circuit, a voltage transformer (143) converting voltage, and a rectifier (144) rectifying the output of the voltage transformer (143).

[0057] The switching unit (141) can be implemented as a full bridge circuit using four switching elements Q1 to Q4, as shown in Fig. 10. The switching elements Q1 to Q4 are semiconductor switching elements, and elements of the Si, SiC, and GaN series can be used. The control unit (120) can control the pulse width of the output signal by PWM controlling the duty of Q1 and Q3.

[0058] The resonant unit (142) can configure an LLC resonant circuit in various ways, as shown in Fig. 11. The resonant circuit can be configured by connecting inductors and capacitors in series, and can include at least two inductors (LL) and at least one capacitor (C). As shown in 510 and 520, the connection order or connection state of the elements can be changed, and as shown in 530, the number of elements can increase. In addition, as shown in 540, at least one of the inductors used in the resonant circuit can be connected in parallel with the transformer (143). At this time, as shown in 550, the inductor connected in parallel with the transformer (143) can be replaced with the magnetizing inductance of the transformer (143).

[0059] The secondary circuit and rectifier of the transformer (143) can be configured in various ways, as shown in Fig. 12. The rectifier (144) can be implemented with a current doubler (610), a full-wave rectifier (620), and a center-tapped full-wave rectifier (630). The diodes of the rectifier (144) of 510 to 530 can be replaced with semiconductor switch elements, as in the rectifier (144) of 540 to 560, and the use of the semiconductor switch enables bidirectional power transmission. The semiconductor switch can be a Si, SiC, or GaN series element.

[0060] When two resonant LLC converters are used, a circuit configuration as shown in Fig. 13 is possible. The inputs are connected in parallel, but the outputs can be connected in parallel, as in 710, or in series, as in 720.

[0061] 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. A plurality of power conversion units connected in parallel, each of which includes a switching unit; and It includes a control unit that controls the plurality of power conversion units using PWM (pulse width modulation), The above control unit, A power conversion device that individually controls the pulse width of the output signal of each switching unit of the plurality of power conversion units.

2. In paragraph 1, The above control unit, A power conversion device in which the switching frequency of the output signal of each switching unit of the plurality of power conversion units is the same, and the phase difference between the output signals of each switching unit of the plurality of power conversion units has a preset phase difference.

3. In paragraph 2, The phase difference between the output signals of each switching unit of the above plurality of power conversion units is A power conversion device that varies depending on the number of power conversion units included in the above plurality of power conversion units.

4. In paragraph 3, The phase difference between the output signals of each switching unit of the above plurality of power conversion units is A power conversion device set by the difference between the centers of the pulse widths of the output signals of each switching unit of the plurality of power conversion units.

5. In paragraph 2, The above plurality of power conversion units include a first power conversion unit and a second power conversion unit, A power conversion device in which the phase difference between the output signal of the switching unit of the first power conversion unit and the output signal of the switching unit of the second power conversion unit is 90 degrees.

6. In paragraph 1, The switching unit of each of the above multiple power conversion units is: Comprising one or more upper switches and one or more lower switches that are connected in series and conduct complementarily, A power conversion device in which the pulse width of the output signal of each switching unit of the plurality of power conversion units changes depending on the duty value of the upper switch.

7. In paragraph 1, A power conversion device including a plurality of first monitoring units that measure at least one of the output voltage, output current, and output power of each of the plurality of power conversion units.

8. In paragraph 1, A power conversion device including a plurality of second monitoring units that measure at least one of the input voltage, input current, and input power of each of the plurality of power conversion units.

9. In paragraph 1, A plurality of first monitoring units for measuring at least one of the output voltage, output current, and output power of each of the plurality of power conversion units; and A power conversion device including a plurality of second monitoring units that measure at least one of the input voltage, input current, and input power of each of the plurality of power conversion units.

10. In paragraph 1, Each of the above multiple power conversion units, A switching unit that receives direct current voltage, converts it into alternating current voltage, and outputs it; A resonant section that converts the output of the switching section using resonance; A transformer for converting the output of the above resonant section; and A power conversion device including a rectifier that rectifies the output of the above transformer into a direct current voltage.

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