WO2018147544A1

WO2018147544A1 - Power conversion device and battery charging system comprising same

Info

Publication number: WO2018147544A1
Application number: PCT/KR2017/014922
Authority: WO
Inventors: 한상택; 박정건; 양정모; 민병선; 박정필; 송준우
Original assignee: 삼성에스디아이주식회사
Priority date: 2017-02-08
Filing date: 2017-12-18
Publication date: 2018-08-16
Also published as: KR102380513B1; KR20180092192A

Abstract

A power conversion device and a battery charging system, according to various embodiments, are disclosed. Disclosed are a power conversion device and a battery charging system comprising the same, the power conversion device comprising: a PFC converter for converting an alternating current input voltage into a direct current voltage and outputting the same, and correcting a power factor; a DC link for receiving a direct current voltage from the PFC converter; a DC-DC converter for converting the direct current voltage received from the DC link into an alternating current voltage and converting the alternating current voltage back into the direct current voltage; and a control unit for adjusting the output voltage and the output current of the DC-DC converter by controlling at least one of the switching frequency and the duty ratio of the PFC converter, wherein the PFC converter and the DC-DC converter comprise a 3-level converter.

Description

Power conversion device and charging system of battery including same

The present invention relates to a power conversion device and a charging system of a battery including the same.

Most of the components constituting the interior of various electronic devices used today require a DC voltage, but since the required values are different from each other, it is very important to properly convert the level of the voltage supplied to these components. Accordingly, converters for outputting a desired voltage by boosting or stepping down a predetermined voltage are widely used. In particular, in the DC-DC converter converting the input DC power to a different level of DC power, a method of controlling the flow of electric power by using a switching operation of a power semiconductor device is widely used, thereby providing high efficiency and high power density. It is possible to implement a conversion device.

Power converters generally include PFC converters and DC-DC converters. The DC-DC converter adjusts the switching frequency and duty ratio as the load changes. When the DC-DC converter is out of the predetermined switching frequency due to the change in the load amount, switching loss occurs when the switching element included in the DC-DC converter is turned on / off. This switching loss causes a problem of lowering the efficiency of the DC-DC converter.

The problem to be solved by the present invention is that the DC-DC converter is always optimal regardless of load by feedback control the PFC converter and drive the DC-DC converter in an open loop with a fixed duty ratio and a fixed switching frequency The present invention provides a power conversion device and a charging system including the same that can be obtained by operating in a high efficiency and high performance.

According to an aspect of the present invention, a power converter includes a PFC converter that converts an AC input voltage into a DC voltage, outputs a power factor, and compensates a power factor, a DC link supplied with a DC voltage from the PFC converter, and a DC voltage supplied from the DC link. Is a DC-DC converter for converting an AC voltage to a DC voltage, and a controller for controlling the output voltage and the output current of the DC-DC converter by controlling at least one of a switching frequency and a duty ratio of the PFC converter. In addition, the PFC converter and the DC-DC converter is characterized in that it comprises a three-level converter.

According to an example of the power converter, the control unit detects the magnitude of the output voltage and the output current of the DC-DC converter, characterized in that the feedback control of the switching frequency and duty ratio of the PFC converter.

According to another example of the power converter, the three-level converter included in the DC-DC converter is characterized in that it comprises a resonant LLC converter.

According to another example of the power converter, the DC-DC converter is operated at a first frequency which is a fixed switching frequency, wherein the first frequency has a value corresponding to the resonant frequency of the resonant LLC converter.

According to another example of the power converter, the DC-DC converter is characterized in that it is controlled through a PWM signal having a fixed duty ratio to any value of 25% to 50%.

According to another example of the power converter, the voltage of the DC link is characterized in that it changes in response to the variation of the output voltage of the DC-DC converter.

According to another example of a power converter, the DC link is characterized in that it comprises a film capacitor.

Battery charging system according to an aspect of the present invention, a battery pack including at least one battery cell, and a PFC converter for converting an AC voltage applied from the system to a DC voltage and a power factor compensation, DC voltage from the PFC converter The battery by controlling at least one of a switching frequency and a duty ratio of the DC link receiving a DC link, a DC-DC converter supplied from the DC link to an AC voltage, and converting the DC voltage back to a DC voltage, and the PFC converter. And a power conversion device including a control unit for adjusting an output voltage and an output current applied to the pack, wherein the PFC converter and the DC-DC converter include a three level converter.

According to an example of a battery charging system, the controller compares a magnitude of an output current applied to the battery pack with a preset reference current to feedback control at least one of a switching frequency and a duty ratio of the PFC converter.

According to another example of a battery charging system, the controller compares a voltage applied to the battery pack with a preset reference voltage to feedback control at least one of a switching frequency and a duty ratio of the PFC converter.

According to another example of a battery charging system, the three level converter included in the DC-DC converter is a resonant LLC converter.

According to another example of the battery charging system, the DC-DC converter is characterized in that the voltage gain is kept constant even if the voltage and current applied to the battery pack is changed.

According to another example of a charging system of a battery, the DC-DC converter operates at a first frequency that is a fixed switching frequency, wherein the first frequency has a value corresponding to the resonant frequency of the resonant LLC converter. .

According to another example of a charging system of a battery, the DC-DC converter is controlled through a PWM signal having a fixed duty ratio at any one of 25% to 50%.

According to another example of the battery charging system, the voltage of the DC link is characterized in that it changes in response to a change in the voltage applied to the battery.

According to various embodiments of the present disclosure, the energy stored in the batteries may be efficiently adjusted by adjusting the magnitude of the discharge end voltage at which the batteries included in the battery pack or the energy storage system terminate the discharge according to the output amount of the battery pack or the energy storage system. Can be used as

1 is a diagram schematically illustrating an internal configuration of a power conversion apparatus according to an embodiment of the present invention.

2 is a diagram schematically illustrating a resonant LLC transformer which is part of a DC-DC converter according to an embodiment of the present invention.

3 shows a graph of the voltage gain of a DC-DC converter.

4 is a diagram illustrating a DC-DC converter and a PFC converter including a three-level converter by way of example.

5 exemplarily shows a control timing diagram of a PFC converter.

6 exemplarily shows a control timing diagram of a DC-DC converter.

7 is a view briefly illustrating an internal configuration of a charging system of a battery according to an embodiment of the present invention.

Advantages and features of the present invention, and methods of achieving them will be apparent with reference to the embodiments described in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments set forth below, but may be embodied in many different forms and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. do. The embodiments set forth below are provided to make the disclosure of the present invention complete, and to fully inform the scope of the invention to those skilled in the art. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings, and in the following description with reference to the accompanying drawings, the same or corresponding components are given the same reference numerals and redundant description thereof will be omitted. Let's do it.

Referring to FIG. 1, the power converter 100 includes a PFC converter 110, a DC-DC converter 120, a DC link 140, and a controller 130.

The power converter 100 converts the supplied AC voltage into a DC voltage and outputs the DC voltage. The power converter 100 may adjust the magnitude of the DC voltage. For example, the power converter 100 may be a charger that charges the battery pack 20. In this case, the power converter 100 may charge the battery by converting it into a voltage required to charge the battery pack 20. The power converter 100 may include at least one converter.

The PFC converter 110 may compensate for the power factor of the voltage while converting an AC input voltage into a DC voltage. That is, the PFC converter 110 may increase the power factor by reducing the phase difference between the rectifying configuration and the input current and the input voltage for converting an AC voltage into a DC voltage. Specifically, the PFC converter 110 is composed of a PFC circuit part for improving the power factor and a DC-DC converter for DC voltage conversion, which is performed by separating the PFC function and the DC-DC conversion function, and thus have a high power factor close to one. Also, the regulation and dynamic characteristics of the output voltage also have excellent advantages.

The DC-DC converter 120 may convert an output voltage output from the PFC converter 110 into an AC voltage and convert the converted AC voltage into a DC voltage again. The DC-DC converter 120 supplies the converted DC voltage to a load connected to the power converter 100. The DC-DC converter 120 may be configured as an isolated DC-DC converter 120 including a transformer. The DC-DC converter 120 is implemented in any one of a full bridge, a phase shift full bridge, and a half bridge.

The DC link 140 temporarily stores the DC power output from the PFC converter 110 and transfers the stored power to the DC-DC converter 120. The DC link 140 may have one voltage between the PFC converter 110 and the DC-DC converter 120 having different voltage levels. DC link 140 includes a link capacitor. The link capacitor may filter the ripple component of the DC power output from the PFC. For example, when the PFC converter 110 is connected to the grid 10 to receive AC power of 60 Hz, the DC link 140 filters the 60 Hz component of the grid 10 using the link capacitor to form a ripple component. Can be removed.

The controller 130 acquires at least one of an output voltage and an output current of the power converter 100 to process data, such as a processor capable of adjusting the switching frequency and duty ratio of the PFC converter 110. It can include any kind of device that can. Here, the 'processor' may refer to a data processing apparatus embedded in hardware having, for example, a circuit physically structured to perform a function represented by code or instructions included in a program. As an example of a data processing device embedded in hardware, a microprocessor, a central processing unit (CPU), a processor core, a multiprocessor, and an application-specific integrated device (ASIC) It may include a processing device such as a circuit, a field programmable gate array (FPGA), etc., but the scope of the present invention is not limited thereto.

The controller 130 may control power factor control of the PFC converter 110 and output of the power converter 100. The controller 130 may control the output voltage and the output current of the PFC converter 110 after comparing the preset reference current and the reference voltage with at least one of the output current and the output voltage of the power converter 100. In detail, the controller 130 controls the switching frequency and the duty ratio of the PFC converter 110 without controlling the switching frequency and the duty ratio of the DC-DC converter 120. The controller 130 detects an output of the power converter 100 and adjusts a frequency and duty ratio of a pulse width modulation (PWM) signal applied to the PFC converter 110 so that the detected value matches a preset target value. do.

For example, when the power converter 100 is a charger that charges the battery pack 20, the controller 130 may charge the battery pack 20 with a constant current and a constant voltage. In the case of the constant current charging, the controller 130 may control the switching frequency and the duty ratio of the PFC converter 110 so that the output current output to the battery pack 20 matches the preset reference current. Similarly, in the case of constant voltage charging, the controller 130 may control at least one of the switching frequency and the duty ratio of the PCF converter so that the output voltage output to the battery pack 20 matches the preset reference voltage.

Meanwhile, the controller 130 does not control the voltage of the DC link 140 to maintain a predetermined voltage value. That is, the voltage of the DC link 140 is variable depending on the voltage output from the PFC converter 110 and the high frequency component is allowed to flow. In addition, the switching frequency and duty ratio of the DC-DC converter 120 are controlled to not adjust the output voltage and the current of the power converter 100. In this case, the DC-DC converter 120 has a function of transferring power of the PFC converter 110 to the battery side in an insulated state through open loop control without feedback control according to the output voltage and the output current.

2 is a diagram schematically illustrating a resonant LLC transformer which is part of a DC-DC converter according to an embodiment of the present invention. 3 shows a graph of the voltage gain of a DC-DC converter.

Referring to FIG. 2, the DC-DC converter 120 includes a resonant LLC transformer 121. The resonant LLC transformer 121 is defined as including a resonant capacitor Cr, a resonant inductor Lr, a magnetized inductor Lm, a transformer Tr, and a second rectifier 123.

The structure of the resonant LLC transformer 121 is similar to the LC series resonant converter, with the only difference being the magnetization inductance value. The series resonant converter has a much larger magnetizing inductance than the LC series resonant inductance, but the magnetizing inductance of the resonant LLC transformer 121 is three to eight times larger than the LC series resonant inductance and is usually implemented by introducing a void in the transformer. The resonant LLC transformer 121 has many advantages over the series resonant converter.

In other words, even if the switching frequency is adjusted very small, proper output regulation can be realized for sensitive load fluctuations. In addition, zero voltage switching (ZVS) is possible in the operating region of the DC-DC converter 120. And all the necessary parasitics, including junction capacitances of all semiconductor devices and magnetizing inductances and leakage inductances of transformers, can be utilized to achieve soft switching. The resonant LLC transformer 121 has parameter values that change slowly over time.

Referring to FIG. 3, there is shown a voltage gain graph of DC-DC converter 120 when varying the switching frequency of DC-DC converter 120 including resonant LLC transformer 121.

In the DC-DC converter 120, the voltage gain varies according to the increase or decrease of the load. As shown in FIG. 3, the gain has a value of 1 when the switching frequency Fs of the DC-DC converter 120 and the resonance frequency Fr of the resonant LLC transformer 121 are the same.

The first region Region 1 and the third region Region 3 are zero voltage switching regions, and the second region Region 2 is a zero current switching region. In the DC-DC converter 120, the voltage gain is changed as the load is changed, and the switching region is shown through the first to third regions (Region 1 to Region 3). In particular, when a large current flows in the resonant inductor Lr due to a large fluctuation range of the switching frequency Fs during operation in the first region Region 1, the switches included in the DC-DC converter 120 are turned off to cause switching loss. This increases. Therefore, it is necessary to fix the switching frequency Fs of the DC-DC converter 120 to a value corresponding to the resonance frequency Fr, thereby operating the DC-DC converter 120 to minimize switching losses.

According to an embodiment, the DC-DC converter 120 operates at the same switching frequency Fs as the resonance frequency Fr. The controller 130 may feedback-control the PFC converter 110 based on the output current and output voltage of the power converter 100 (or the output current and output voltage of the DC-DC converter 120) to convert the power converter ( The output current and output voltage of 100 can be adjusted. The DC-DC converter 120 operates with the switching frequency Fs fixed at the resonance frequency Fr. In this case, losses of switches of the DC-DC converter 120 may be minimized.

According to an embodiment, the power converter 100 may be connected between the system 10 and the battery pack 20 to charge the battery pack 20. In this case, when charging the battery pack 20 with a constant current, if the voltage of the battery pack 20 varies from Vb1 to Vb2, the voltage of the DC link 140 ranges from Vb1 * N1 / N2 to Vb2 * N1 / N2 Will fluctuate in. At this time, N1 is the winding ratio of the primary side of the transformer to which the current is applied, and N2 is the winding ratio of the secondary side of the transformer to which the current is output. For example, when the voltage of the battery pack 20 is changed from 40V to 60V and N1: N2 is 2: 1, the voltage of the DC link 140 is 80V to 120V corresponding to the voltage change of the battery pack 20. Change.

In this case, the DC link 140 may vary to a higher voltage than when the voltage is maintained at a predetermined value. When the DC link 140 rises to a high voltage, it may cause damage to the switching elements included in the PFC converter 110 and the DC-DC converter 120. For example, when a voltage of the DC link is maintained at 100 V, a switching element of the PFC converter 110 and the DC-DC converter 120 (eg, the voltage resistance voltage of the switching element is 110 V) is selected. When the voltage of the battery pack 20 changes from 50V to 80V, the voltage across the DC link 140 changes from 100V to 160V. In this case, 160 V, the maximum value of the DC link 140 voltage, is applied to each of the switch elements included in the PFC converter 110 and the DC-DC converter 120, and the switching element is higher than the breakdown voltage rated voltage. Can be applied and burned. That is, in the case of not controlling to maintain the voltage of the DC link 140 at a constant value, the switching elements should be composed of switching elements having a high breakdown voltage rating of 160V or more.

The power converter 100 according to an embodiment configures the DC-DC converter 120 and the PFC converter 110 as a three-level converter, so that the switching is included in the PFC converter 110 and the DC-DC converter 120. Voltages applied to the DC links 140 may be divided and applied to the devices, and a detailed description thereof will be described with reference to FIG. 4.

4 is a diagram illustrating a DC-DC converter and a PFC converter including a three-level converter by way of example. 5 exemplarily shows a control timing diagram of the PFC converter, and FIG. 6 exemplarily shows a control timing diagram of the DC-DC converter.

Referring to FIG. 4, the PFC converter 110 and the DC-DC converter 120 include a three level converter. As shown in FIG. 4, the PFC converter 110 configured as a three-level converter includes two switches, and the DC-DC converter includes four switches. Each switch applies a preset PWM signal to increase the DC voltage. Have a value of 0, and a negative value. In this case, the three-level converter is about half the lower harmonic generation and the voltage stress of the switching element compared to the conventional two-level converter, and can significantly reduce the loss in the switching element and the filter circuit. On the other hand, there are two types of three-level methods, NPC (Neutral Point Clamped) and TNPC (T-type Neutral Point Clamped).

In addition, the three-level converter can reduce the circulating current even in the power converter 100 having a wide output voltage range. For example, when the power converter 100 charges the battery pack 20, the three-level converter can reduce the conduction loss when charging the CC mode mainly operating at a low battery voltage.

The power converter 100 includes a DC-DC converter 120, a PFC converter 110, and a controller 130. The DC-DC converter 120 includes third to sixth switches SW3 to SW6, third to sixth diodes D3 to D6, and a resonant LLC transformer 121 for switching. The PFC converter 110 includes a first switch SW1, a second switch SW2, a first diode D1, a second diode D2, and a first rectifier 111.

The switches SW1 to SW6 included in the PFC converter 110 and the DC-DC converter 120 turn on the switch because the voltage and current change with a constant delay and slope according to the characteristics of the device in the switching operation. Alternatively, when turned off, a section in which voltage and current are simultaneously applied to the switch occurs. During this period, switching power losses corresponding to the product of voltage and current occur.

For example, devices such as Insulated Gate Bipolar Transistors (IGBTs) switch during turn-off because tail current flows for a period of time even after sufficient voltage is applied across the switch at turn-off. Loss occurs. This switching loss increases in proportion to the frequency at which the device is opened and closed, thereby limiting the maximum switching frequency of the device.

The three-level converter can perform zero voltage switching to switch in a zero voltage state to enable high frequency switching while reducing switching loss of a power semiconductor device. In addition, the three-level converter may cause a voltage of half of the voltage applied to the switching element in the two-level converter to be applied to the switching element.

The DC-DC converter 120 is disposed between each of the third switch SW3, the fourth switch SW4, the fifth switch SW5, the sixth switch SW6, and the third to sixth switches SW3 to SW6. A flying capacitor Css connected between the fourth switch SW4 and the fifth switch SW5 for balancing the anti-parallel diodes D3 to D6 and the voltage level output by the switch, respectively. The flying capacitors Css are connected in series and include diodes Dc1 and Dc2 connected in parallel.

Referring to FIG. 5, the DC-DC converter 120 includes third to sixth switches by PWM signals having a switching frequency Fs, which is a first frequency (1 / Ts), and a first duty ratio (D). (SW3 to SW6) are switched. As shown in the PWM signals, the third to sixth switches SW3 to SW6 may be switched to three modes, that is, (1) the third switch SW3 and the fifth switch SW5 are turned on and the fourth switch ( SW4) and the mode in which the sixth switch SW6 is turned off (2) The mode in which all of the third to sixth switches SW3 to SW6 are turned off (3) The third switch SW3 and the fifth switch SW5 The turn off, the fourth switch SW4 and the sixth switch SW6 are operated in a turned on mode. At this time, the first frequency 1 / Ts has the same value as the resonance frequency Fr.

As such, the third to sixth switches SW3 to SW6 operate in three modes by the PWM signals, and at a constant rate by the transformer on the secondary side by the current applied to the resonant LLC transformer 121. Increased or decreased current is induced. The induced current is rectified by the second rectifying unit 123 described with reference to FIG. 2, and the ripple is removed through the smoothing filter C1 and output.

According to an embodiment, the DC-DC converter 120 may have a fixed switching frequency (Fs) and a duty ratio (D) when the power converter 100 which has started to operate is stabilized. As described above, the output of the DC-DC converter 120 is controlled according to the output of the PFC converter 110. The DC-DC converter 120 has a constant voltage gain because the switching frequency Fs having the first period Ts is fixed at the resonance frequency Fr, and after the power conversion device 100 which has started operation is stabilized, It can be operated by fixing one duty ratio (D) to any value between 25% and 50%. In this case, the DC-DC converter 120 does not change the switching frequency Fs and the first duty ratio D according to the load variation. That is, the DC-DC converter 120 may operate while maintaining the switching frequency Fs and the first duty ratio D, which are the first frequency 1 / Ts, to minimize the switching loss.

Referring to FIG. 6, the PFC converter 110 controls the turn on / off operations of the first switch SW1 and the second switch SW2 according to the PWM signal of the controller 130. The PWM signal has a second period Ts and a second duty ratio D. The controller 130 sets the first switch SW1 and the second switch SW2 in the first state (1) to turn on the first switch SW1 and to turn off the second switch SW2 (2). (3) Turn-off mode of first switch SW1 and second switch SW2 (3) Turn-off mode of first switch SW1 and turn-on mode of second switch SW2 In the second state, (1) the turn-on mode of the first switch SW1, the turn-off mode of the second switch SW2, and (2) the turn-on mode of the first switch SW1 and the second switch SW2 (3) It operates in three modes: turn off of the first switch SW1 and turn-on mode of the second switch SW2.

The first state is when the second duty ratio D is 0% or more and 50% or less, and the second state is when the second duty ratio D is more than 50% and less than 100%. The switching frequency and duty ratio of the PFC converter 110 vary according to the variation of the load amount.

The DC link 140 is divided into a first link capacitor Ck1 and a second link capacitor Ck2. The node to which the first link capacitor Ck1 and the second link capacitor Ck2 are connected is a neutral node (voltage is 0V). In this case, the voltage applied to the DC link 140 is divided and applied to each of the first link capacitor Ck1 and the second link capacitor Ck2. In this case, a voltage applied to any one of the first link capacitor Ck1 and the second link capacitor Ck2 is applied to each of the switches SW3 to SW6 included in the DC-DC converter 120.

Also, in the case of the PFC converter 110, the first switch SW1 is connected in parallel with the first link capacitor Ck1, and the second switch SW2 is connected in parallel with the second link capacitor Ck2. The voltage of the divided DC link 140 is applied to the second switch SW2 and the second switch SW2. For example, half of the voltage applied to the DC link 140 may be applied to the first switch SW1 and the second switch SW2.

According to one embodiment, the voltage of the DC link 140 is variable in response to a change in the output voltage of the power converter 100. The voltage of the DC link 140 may vary and a higher voltage may be applied than when the voltage of the DC link 140 is controlled to have a constant value. The power converter 100 includes a DC-DC converter 120 and a PFC converter 110 including a three-level converter, and a part of the voltage of the DC link 140 may be applied to each switching device. For example, when the maximum voltage applied to the DC link 140 is 160V, a voltage of 80V may be applied to each of the switching elements included in the DC-DC converter 120 and the PFC converter 110. In this case, the switching elements included in the DC-DC converter 120 and the PFC converter 110 may be selected as switching elements having a breakdown voltage rating of greater than 80V.

As a result, since the controller 130 does not control the voltage of the DC link 140 to a constant value, the voltage of the DC link 140 increases, so that the voltage of the DC link has a maximum value exceeding the breakdown voltage rating of the switching element. The power converter 100 may configure the DC-DC converter and the PFC converter as a three-level converter to distribute the voltage of the DC link to be applied to each of the switching elements, and to operate the switching elements without damage.

Referring to FIG. 7, the charging system 200 of a battery includes a power converter 100 and a battery pack 20. The charging system 200 of the battery is electrically connected to the system 10 to receive AC power from the system 10.

The power converter 100 includes a PFC converter 110, a DC-DC converter 120, and a DC link 140. The PFC converter 110 and the DC-DC converter 120 include a three level converter, and the DC link 140 includes a first link capacitor Ck1 and a second link capacitor Ck2.

The system 10 includes a power plant, a substation, a power transmission line, and the like. The system 10 may supply an alternating voltage to the charging system 200 of the battery. The system 10 may provide an alternating voltage with constant voltage value and frequency to the charging system 200 of the battery. For example, the system 10 may be a commercial power source capable of providing an alternating voltage having a voltage value of 220 V and a frequency of 60 Hz.

The battery pack 20 may include a battery including at least one battery cell (not shown), a battery manager (not shown), and a charge / discharge switch (not shown).

The battery is a portion that stores power and includes at least one battery cell. The battery may include one battery cell, or the battery may include a plurality of battery cells, and the battery cells may be connected in series, connected in parallel, or a combination of series and parallel. The number and connection scheme of the battery cells included in the battery may be determined according to the required output voltage and power storage capacity.

The battery cell may include a secondary battery except for a lead acid battery that may be charged. For example, the battery cell may include a nickel-cadmium battery, a nickel metal hydride battery (NiMH), a lithium ion battery, and a lithium polymer battery. have.

The charge switch and the discharge switch may be disposed on the high current path of the battery to interrupt the flow of the charge current and the discharge current of the battery. The charge switch and the discharge switch may be turned on / off in accordance with a control signal of the battery manager. Charge and discharge switches may include relays or FET switches.

The battery manager acquires information about the battery, such as current, voltage, and temperature of the battery, and analyzes the state of the battery and determines all kinds of devices capable of processing data such as a processor that can determine the need for battery protection. It may include. Here, the 'processor' may refer to a data processing apparatus embedded in hardware having, for example, a circuit physically structured to perform a function represented by code or instructions included in a program. As an example of a data processing device embedded in hardware, a microprocessor, a central processing unit (CPU), a processor core, a multiprocessor, and an application-specific integrated device (ASIC) It may include a processing device such as a circuit, a field programmable gate array (FPGA), etc., but the scope of the present invention is not limited thereto.

The battery manager detects a current, a voltage, and a temperature of a battery, and obtains a remaining power amount, a lifetime, a state of charge (SOC), etc. based on the detected information. For example, the battery manager may measure the cell voltage and the temperature of the battery cell using the sensors.

According to an embodiment, the controller 130 may receive information about the state of the battery from the battery manager. When the controller 130 receives the fact that the battery has reached the buffer voltage from the battery manager, the controller 130 may stop the operation of the PFC converter 110 and the DC-DC converter 120 to stop charging of the battery pack 20. have. Meanwhile, although the controller 130 and the battery manager are shown in separate configurations, the controller 130 may be configured to perform a function of the battery manager.

The PFC converter 110 may convert an AC voltage provided from the system 10 into a DC voltage. The controller 130 may correct the power factor by controlling the PFC converter 110, and control the switching frequency and the duty ratio of the PWM signal of the PFC converter 110 to output a DC voltage and a DC current output by the PFC converter 110. Can be controlled.

The voltage of the DC link 140 may vary in response to a change in the charging voltage of the battery pack 20. In general, the voltage of the DC link 140 is controlled to be a constant value, but in the charging system 200 of the battery according to an embodiment, the DC-DC converter 120 has a constant voltage gain (for example, voltage gain). To maintain this 1), the voltage of the DC link 140 is varied to correspond to the voltage of the battery pack 20.

The DC-DC converter 120 changes the DC voltage supplied from the DC link 140 into a high frequency AC voltage and applies it to the primary side of the transformer Tr, and the second rectifying unit 123 on the secondary side of the transformer Tr. To DC voltage. The DC-DC converter 120 includes a three level resonant LLC converter, which is a resonant LLC converter (see FIG. 4) that includes a three level converter. The switching frequency Fs of the DC-DC converter 120 is fixed to a value corresponding to the resonant frequency Fr of the resonant LLC converter.

According to an embodiment, the controller 130 performs feedback control on the switching frequency and duty ratio of the PFC converter 110. When charging the battery pack 20 with a predetermined reference current as a constant current, the controller 130 switches the PFC converter 110 until the output current of the power converter 100 matches the preset reference current. Correct the frequency and duty ratio. That is, the controller 130 detects the output current of the power converter 100 and feedback-controls the switching frequency and duty ratio of the PFC converter 110 such that the detected output current matches the preset reference current. In this case, the controller 130 may correspond to the switching frequency and duty ratio of the PFC converter 110 by modifying the load according to the load amount variation (for example, the charging voltage variation of the battery), and the switching frequency of the DC-DC converter 120. (Fs) and duty ratio (D) can be fixed to a predetermined value.

In addition, in the case of charging the battery pack 20 with a predetermined reference voltage at a constant voltage, the controller 130 may control the PFC converter 110 until the output voltage of the power converter 100 matches the predetermined reference voltage. Correct the switching frequency and duty ratio. Even in this case, the controller 130 may correspond to the switching frequency and duty ratio of the PFC converter 110 by modifying the load according to the load variation, and the DC-DC converter 120 sets the switching frequency Fs to the resonance frequency Fr. ) And the duty ratio (D) of the DC-DC converter 120 may be operated at a fixed value of any one of 25% to 50%.

According to an embodiment, the DC-DC converter 120 may be operated with a switching frequency Fs having a first period Ts fixed and a duty ratio of any one of 25% to 50% duty ratio. have. The DC-DC converter 120 may perform a phase shifter for a predetermined time so that the power converter 100, which starts the charging operation, is soft-started. The phaser shifted DC-DC converter 120 determines a duty ratio that can operate in an optimal state, and is fixed and operated at the determined duty ratio regardless of a load change. In addition, the switching frequency (Fs) is a value corresponding to the resonant frequency (Fr) of the DC-DC converter 120.

According to one embodiment, the DC link 140 may include a film capacitor. Since the DC link 140 is not controlled to maintain a fixed voltage, the link capacitors Ck1 and Ck2 included in the DC link 140 do not require high capacitance. Therefore, the link capacitors Ck1 and Ck2 may adopt and use a film capacitor in place of an electrolyte capacitor having a disadvantage of a sharp drop in life due to a temperature increase, thereby achieving a long life of the DC link 140. .

As a result, the DC-DC converter 120 can be driven in an open loop by using a PWM signal of a fixed frequency (Fs) and a fixed duty ratio (D) without a separate controller, thereby achieving a low price, and is related to the amount of load. High efficiency and high performance can be obtained by always operating in the optimal state.

In addition, the DC-DC converter 120 and the PFC converter 110 are configured as three-level converters even when the maximum value of the voltage applied to the DC link 140 increases by varying the voltage of the DC link 140. By lowering the voltage applied to the switching element, it is possible to operate the charging system 200 of the battery without damaging the switching element without increasing the breakdown voltage rating of the switching elements.

The spirit of the present invention should not be limited to the embodiments described above, and all the scope equivalent to or equivalent to the scope of the claims as well as the following claims are within the scope of the spirit of the present invention. I will say.

Claims

A PFC converter converting an AC input voltage into a DC voltage and outputting the same, and compensating for the power factor;

A DC link supplied with the DC voltage from the PFC converter;

A DC-DC converter converting a DC voltage supplied from the DC link into an AC voltage and converting the DC voltage into a DC voltage again; And

And a controller configured to control at least one of a switching frequency and a duty ratio of the PFC converter to adjust an output voltage and an output current of the DC-DC converter.

And the PFC converter and the DC-DC converter include a three level converter.
The method of claim 1,

And the control unit detects magnitudes of the output voltage and the output current of the DC-DC converter to feedback control the switching frequency and the duty ratio of the PFC converter.
The method of claim 2,

And the three level converter included in the DC-DC converter comprises a resonant LLC converter.
The method of claim 3,

The DC-DC converter operates at a first frequency that is a fixed switching frequency,

And the first frequency has a value corresponding to the resonant frequency of the resonant LLC converter.
The method of claim 4, wherein

And the DC-DC converter is controlled through a pulse width modulation (PWM) signal having a duty ratio fixed at any one of 25% to 50%.
The method of claim 1,

And the voltage of the DC link varies in response to a change in an output voltage of the DC-DC converter.
The method of claim 1,

And the DC link comprises a film capacitor.
A battery pack including at least one battery cell; And

A PFC converter converting an AC voltage applied from a system into a DC voltage and compensating for a power factor; And a power conversion device including a DC-DC converter for converting and a control unit controlling at least one of a switching frequency and a duty ratio of the PFC converter to adjust an output voltage and an output current applied to the battery pack.

The PFC converter and the DC-DC converter includes a three-level converter.
The method of claim 8,

And the controller is configured to feedback control at least one of a switching frequency and a duty ratio of the PFC converter by comparing a magnitude of an output current applied to the battery pack with a preset reference current.
The method of claim 8,

And the controller is configured to feedback control at least one of a switching frequency and a duty ratio of the PFC converter by comparing a voltage applied to the battery pack with a preset reference voltage.
The method of claim 8,

And the three-level converter included in the DC-DC converter is a resonant LLC converter.
The method of claim 11,

The DC-DC converter is a battery charging system, characterized in that the voltage gain is kept constant even if the voltage and current applied to the battery pack is changed.
The method of claim 12,

The DC-DC converter operates at a first frequency that is a fixed switching frequency,

And the first frequency has a value corresponding to the resonant frequency of the resonant LLC converter.
The method of claim 13,

And the DC-DC converter is controlled through a pulse width modulation (PWM) signal having a fixed duty ratio of any of 25% to 50%.
The method of claim 8,

The voltage of the DC link is variable in response to a change in the voltage applied to the battery.