KR102181321B1 - Power conversion apparatus - Google Patents

Abstract

The present application relates to a power conversion device capable of balancing a primary-side voltage imbalance of a direct current (DC)-DC converter. According to an embodiment of the present invention, the power conversion device comprises: a plurality of rectifiers which are serially connected to alternating current (AC) input power and rectify each distribution voltage distributed from the input power into DC link voltage; a DC-DC converter which is serially connected to the plurality of rectifiers, transforms the DC link voltage into DC-DC, and includes a first output terminal connected to a load and a second output terminal connected to an energy storage system (ESS); and a control unit which controls the plurality of rectifiers and the DC-DC converter to independently maintain output voltage of the first output terminal and to balance output current of the DC link voltage and the second output terminal. Each of the second output terminals included in the DC-DC converter can be connected in parallel with each other.

Description

Power conversion apparatus

The present application relates to a power conversion device, and more particularly, to a power conversion device capable of performing output control and balancing control for a rectifier and a DC-DC converter connected in series to a power source.

DC converters that convert input DC voltage to output DC voltage with different levels are widely used in the industry. In general, DC converters convert DC voltage to AC voltage and then boost or step down with a transformer and then back to DC voltage. By rectifying, the voltage is transformed.

In the past, independent control of the output was implemented by mainly configuring the primary side of DC converters in parallel and controlling the secondary side individually. However, in the case of such a DC converter, since the entire input voltage cannot be increased, it is applied to low voltage applications.

In a converter circuit of a series type capable of responding to a high-voltage input voltage, a circuit structure for individually controlling the output voltages of DC converters has not been presented so far. In order to individually control the outputs of the DC converters connected in series to the high voltage input voltage, the outputs cannot be connected in parallel, resulting in a problem in that the primary and secondary voltages of each DC converter are different. Therefore, in order to obtain a plurality of individually controlled DC converter outputs, the outputs must be connected in parallel and an individual DC converter must be added again. This structure has a disadvantage that the number of modules in the system is increased, so that it is complicated and economical is poor.

The present application is to provide a power conversion device capable of balancing the primary side voltage imbalance of the DC-DC converter by connecting one of the multiple outputs of the DC-DC converter serially connected to the power source in parallel and controlling the remaining outputs individually. do.

The present application is intended to provide a power conversion device capable of reducing the number of physical current and voltage measuring devices required for control and reducing the amount of computation required for control.

A power conversion device according to an embodiment of the present invention includes a plurality of rectifiers connected in series to an AC input power source and rectifying each of the divided voltages distributed from the input power to a DC link voltage; A first output terminal connected to each of the plurality of rectifiers in series, converting the DC link voltage to DC-DC, and connected to a load, and a second output connected to an ESS (Energy Storage System) A DC-DC converter including a terminal; And controlling the plurality of rectifiers and DC-DC converters to independently maintain the output voltages of the first output terminals, and perform balancing for the DC link voltage and the output currents of the second output terminals. And a control unit, wherein each of the second output terminals included in the DC-DC converters may be connected in parallel with each other.

Here, the DC-DC converter includes: a primary side module for converting the DC link voltage into a first AC voltage; A transformer module configured to transform the first AC voltage into a second AC voltage according to a set winding ratio and output the second AC voltage to a plurality of transformer terminals; A secondary module connected to any one of the transformer terminals and configured to rectify the second AC voltage and provide an output voltage to the first output terminal; And it is connected to the other one of the transformer terminals, supplying the balancing power provided from the transformer module to the other DC-DC converter connected in parallel, or regenerating the balancing power delivered from the other DC-DC converter to the secondary module. It may include a balancing module to allow.

Here, the control unit includes: a rectifier control module for controlling the switching operation of the rectifier so that the magnitude of the ESS current, which is the sum of the output currents of the second output terminal, has a reference ESS current value; And a switching operation of the secondary module and the balancing module so that the magnitudes of the individual DC link voltages applied to each of the DC-DC converters match, and an output voltage corresponding to each load is output to the first output terminal. It may include a DC-DC converter control module to control.

Here, the rectifier control module may receive the magnitude of the ESS current from an ESS current meter positioned between the power storage device and the second output terminal.

Here, the DC-DC converter control module receives the DC link voltage from each DC link voltage meter positioned between the rectifier and the DC-DC converter, and from an output voltage meter positioned at the first output terminal, the Output voltage can be input.

In addition, the solution to the above-described problem does not enumerate all the features of the present invention. Various features of the present invention and advantages and effects thereof may be understood in more detail with reference to the following specific embodiments.

According to the power conversion apparatus according to an embodiment of the present invention, it is possible to individually control the outputs of DC-DC converters to provide a plurality of outputs capable of independent control without the addition of an additional converter. Accordingly, it is possible to provide simultaneous access to various loads and energy sources, such as a DC load requiring individual control, an energy storage system (ESS), an electric vehicle charging infrastructure, and a renewable energy source.

According to the power conversion device according to an embodiment of the present invention, since one of a plurality of outputs of a series-connected DC-DC converter is connected in parallel, the outputs of each rectifier and DC-DC converters are independently maintained and power balance. Can be implemented.

According to the power conversion device according to an embodiment of the present invention, since the rectifier controls the ESS current supplied to the power storage device, and the DC-DC converter controls the output voltage and the DC link voltage, the physical current required for control It is possible to reduce the number of measuring devices and voltage measuring devices and the amount of computation in the control unit. That is, it can be economically and efficiently implemented in terms of installation cost, and it is possible to implement optimized control by reducing the complexity of control.

1 and 2 are circuit diagrams showing a power conversion device according to an embodiment of the present invention.
3 is a block diagram showing a control unit of a power conversion device according to an embodiment of the present invention.
4 is a block diagram showing the operation of the rectifier control module according to an embodiment of the present invention.
5 is a block diagram showing the operation of the DC-DC converter control module according to an embodiment of the present invention.
6 is a block diagram showing a power conversion device according to another embodiment of the present invention.
7 and 8 are block diagrams showing the operation of a control unit according to another embodiment of the present invention.
9 is a schematic diagram showing a modified example of the power conversion device according to an embodiment of the present invention.

Hereinafter, preferred embodiments will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, in describing a preferred embodiment of the present invention in detail, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, the same reference numerals are used throughout the drawings for portions having similar functions and functions.

In addition, throughout the specification, when a part is said to be'connected' to another part, it is not only'directly connected', but also'indirectly connected' with another element in the middle. Include. In addition, "including" a certain component means that other components may be further included rather than excluding other components unless specifically stated to the contrary. In addition, terms such as "~ unit" and "module" described in the specification mean units that process at least one function or operation, which may be implemented as hardware or software, or as a combination of hardware and software.

1 and 2 are circuit diagrams showing a power conversion device according to an embodiment of the present invention.

1 and 2, the power conversion device 100 according to an embodiment of the present invention may include a rectifier 110, a DC-DC converter 120, and a control unit 130. Here, for convenience, a single-phase circuit structure is used, but according to embodiments, a power conversion device operating in a three-phase circuit may be implemented.

Hereinafter, a power conversion device 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

The rectifier 110 may be connected in series to an AC input power source, and an input voltage Vac supplied by the input power may be distributed to each of the rectifiers 110. That is, each of the divided voltages Vac1, Vac2, and Vac3 to which the input power is distributed may be applied to the rectifier 110. Thereafter, the rectifier 110 may generate a DC link voltage by rectifying the applied divided voltage to DC. In FIG. 1, three rectifiers 110 are shown, but the number of rectifiers 110 may be variously changed according to embodiments.

Here, as shown in Figure 9 (a), the rectifier 110 may include a plurality of switches (S11, S12, S13, S14), the switching operation of the switches (S11, S12, S13, S14) Accordingly, the divided voltages Vac1, Vac2, and Vac3 can be converted into DC link voltages V_dc_pri1, V_dc_pri2, and V_dc_pri3. The operation of each of the switches may be controlled by the controller 130, and then the DC link voltages V_dc_pri1, V_dc_pri2, and V_dc_pri3 may be applied to the DC-DC converter 120.

The DC-DC converter 120 may be connected in series to the plurality of rectifiers 110, respectively, and may convert the received DC link voltages V_dc_pri1, V_dc_pri2, and V_dc_pri3 to DC-DC. Here, the DC-DC converter 120 may include a plurality of output terminals, the first output terminal (a-a') is connected to a load, and the second output terminal (b-b') is different It may be connected in parallel with the second output terminals b-b' of the DC-DC converters 120. Specifically, the DC-DC converter 120 may include a primary module 121, a transformer module 122, a secondary module 123, and a balancing module 124, as shown in FIG. 1.

The primary-side module 121 may convert the DC link voltage V_dc_prik into a first AC voltage. In order to convert the received DC link voltage (V_dc_prik) into an output voltage (Vo1) corresponding to the load, the primary side module 111 first converts the DC link voltage DC link voltage (V_dc_prik) to the first AC voltage of AC. I can. Here, the primary side module 111 may include a plurality of switches (S21, S22, S23, S24), as shown in Figure 9 (a), the switches (S21, S22, S23, S24) The DC link voltage (DC link voltage V_dc_prik) may be converted to the first AC voltage by the switching operation. The operation of each of the switches may be controlled by the control unit 130, and the converted first AC voltage is then converted. It can be applied to the transformer module 122. The primary side module 121 can have a structure of a full-bridge converter as shown in Fig. 2, and in addition, various types of converters such as half-bridge converters and NPC type converters. It can be implemented as a structure.

The transformation module 122 may receive a first AC voltage from the primary side module 121 and may transform the first AC voltage into a second AC voltage according to a set winding ratio. The transforming module 122 may include a plurality of transforming terminals, and may supply the transformed second AC voltage through each of the transforming terminals. In FIG. 2, including two transformer terminals, each of which is connected to the secondary side module 123 and the balancing module 124 is illustrated, but it is also possible to include two or more transformer terminals according to embodiments. In this case, there may be two or more secondary-side modules 123 connected to the transformer module 122, and each secondary-side module 123 may output an independent output voltage.

The secondary module 123 may be connected to any one of the transforming terminals, and rectifies the second AC voltage received from the transforming module 122, and converts the output voltage Vo1 to the first output terminals (a-a'). Can provide. As shown in Fig. 9(a), the secondary side module 123 may include a plurality of switches S31, S32, S33, S34, and the switching operation of the switches S31, S32, S33, S34 Accordingly, the second AC voltage can be converted into a DC output voltage Vo1. Here, the operation of each of the switches may be controlled by the control unit 130, and the secondary module 123 may independently output output power corresponding to the connected load. That is, the secondary side module 123 is not affected by other loads connected to the power conversion device 100 and may provide output power constantly. The secondary module 123 may be implemented in various types of converter structures such as a full-bridge converter, a half-bridge converter, and an NPC type converter.

The balancing module 124 may be connected to the other one of the transformer terminals, and may perform a balancing operation for the rectifier 110 or the DC-DC converter 120 according to a control operation by the controller 130. Here, the second output terminal (b-b') of the balancing module 124 is the second output terminal (b-b') of each of the balancing modules 124 included in the plurality of DC-DC converters 120 They may be connected in parallel, through which balancing power may be transmitted between the balancing modules 124.

Specifically, the balancing module 124 supplies the balancing power provided from the transformer module 122 to the other DC-DC converters 120 included in the power conversion device 100, or the other DC-DC converter 120 Balancing power received from them may be regenerated to the secondary module 123 connected through the transformer module 122.

In addition, in some cases, it is also possible to charge or discharge the balancing power with the power storage device 1 connected to the second output terminal b-b'. Here, the power storage device 1 may store power including a plurality of batteries, and may perform a function of a buffer, such as charging or discharging power by the control unit 130. As shown in Fig. 1, the power storage device 130 may be connected to a second output terminal (b-b') connected in parallel, and may be configured except for the power storage device 1 according to embodiments. Do.

Meanwhile, the supply operation of the balancing module 124 supplying the balancing power to other DC-DC converters 120 or the regenerative operation of regenerating the received balancing power to the secondary module 123 are performed by the controller 130 It can be implemented by transmitting control signals.

The balancing module 124 may include a plurality of switches S41, S42, S43, S44, as shown in Fig. 9(a), and the switching operation of each of the switches S41, S42, S43, S44 Depending on the method, the balancing power supply operation and the regenerative operation may be performed respectively.

The second output terminals b-b' connected in parallel of the balancing modules 124 may be connected to the power storage device 1, and may charge or discharge the power storage device 1 according to the balancing.

The controller 130 may control the operation of the rectifier 110 and the DC-DC converter 120. That is, the controller 130 independently maintains the output voltages of the first output terminals, and at the same time performs balancing for the DC link voltage (V_dc_prik) and the output current of the second output terminals (b-b'). Can be controlled to do. Specifically, as illustrated in FIG. 3, the control unit 130 may include a rectifier control module 131 and a DC-DC converter control module 132.

The rectifier control module 131 may control the switching operation of the rectifier 110 so that the magnitude of the ESS current has a reference ESS current value. That is, as shown in FIG. 4, the rectifier control module 131 may control the magnitude of the ESS current, which is the total current for charging or discharging the power storage device 1, through the operation of the rectifier 110. Here, when the size of the ESS current is determined, the size of the total charge/discharge power to be supplied to the power storage device 1 through the rectifier 110 is determined, so the size of the input side current Ii of the rectifier 110 through this Can be controlled. Here, the ESS current meter may be located between the power storage device 1 and the second output terminal (b-b'), as shown in FIG. 1, and the rectifier control module 131 is from the ESS current meter. The size of ESS current can be input.

Conventionally, as shown in FIG. 7, the switching operation of the rectifier 110 was controlled so that the sum of the DC link voltages of each of the plurality of rectifiers 110 coincides with the reference value, and the phase-to-phase voltage balancing according to the three-phase power unbalance is performed. For this purpose, the video division voltage control (Vom) was additionally performed.

On the contrary, the rectifier control module 131 according to an embodiment of the present invention can control the operation of the rectifier 110 using only the size of the ESS current (I _ESS ), and control the voltage of the rectifier for phase-to-phase voltage balancing. Since the etc. can be omitted, it is possible to simplify the control of the rectifier 110. In addition, since the rectifier control module 131 measures and utilizes only one ESS current using an ESS current meter located between the power storage device 1 and the second output terminal (b-b'), an additional current meter It is not necessary, and when a plurality of current measuring devices are included, it is possible to omit necessary additional communication and the like.

The DC-DC converter control module 132 has the same magnitude of the individual DC link voltage V_dc_prik applied to each DC-DC converter 120, and the first output terminal (a-a') is applied to each load. The switching operation of the secondary side module 123 and the balancing module 124 may be controlled so that corresponding output voltages V_dc_port 1, V_dc_port2, and V_dc_port3 are independently output. That is, as shown in Fig. 5, the DC-DC converter control module 132 has the size of each DC link voltage (V_dc_prik) to have an average value (V_dc_pri_ref) of the size of each DC link voltage (V_dc_prik). Control, and the level of the output voltage V_dc_Portj so that each first output terminal a-a' has an output voltage V_dc_Port_ref set to each first output terminal a-a'. . Here, the DC-DC converter control module 132 may receive a DC link voltage (V_dc_pri1, V_dc_pri2, V_dc_pri3) from each DC link voltage measuring device positioned between the rectifier 110 and the DC-DC converter 120. . In addition, the output voltages V_dc_port 1, V_dc_port2, and V_dc_port3 may be input from an output voltage meter located at the first output terminal a-a'.

Conventionally, it is the same to control the DC-DC converter 120 so that the output voltages V_dc_port 1, V_dc_port2, and V_dc_port3 corresponding to each load are independently output to the first output terminal a-a'. However, as shown in Fig. 8, while matching the magnitude of the individual DC link voltage (V_dc_prik) applied to each DC-DC converter 120, output from each of the second output terminals (b-b') The operation of the DC-DC converter 120 was controlled so that the magnitude of the output current being constant is maintained. That is, in order to balance the deviation of the DC link voltage and the output current of the second output terminal (b-b'), two control functions were performed using one degree of freedom of the DC-DC converter 120, so the control performance There was this falling problem. In addition, in order to balance the output current, a precise current measuring device is required for each second output terminal (b-b'), and an additional communication function is required to share the size of the measured output current. That is, since communication for current measurement and sharing thereof is required, the difficulty of building a control system and the complexity of control are also increased, and thus, there is a difficulty in actual implementation.

On the contrary, since the DC-DC converter control module 132 according to an embodiment of the present invention controls the magnitude of the individual DC link voltage V_dc_prik applied to each DC-DC converter 120 to match, It corresponds to performing only one control function with one degree of freedom. That is, it is possible to increase the control performance of the DC-DC converter 120 compared to the conventional one. In addition, the DC-DC converter control module 132 according to an embodiment of the present invention can perform balancing by individually controlling the primary DC link voltage (V_dc_prik) using the DC-DC converter 120 , Additional control for balancing the total DC link voltages (Vdc_Rav, Vdc_Sav, Vdc_Tav) in the three-phase circuit is unnecessary. That is, since the rectifier 110 does not need to control the video voltage, it is possible to reduce the amount of computation of the controller 130.

9 is a schematic diagram showing a modified example of a power conversion device according to an embodiment of the present invention. As shown in Fig. 9(a), in the case of using the 3-wind transformer module 122, one primary module 121 is connected to the primary side, and the secondary module 123 and the secondary module 123 are respectively balanced on the secondary side. The module 124 may form a connected unit structure. That is, when a plurality of unit structures of FIG. 9(a) are combined, a power conversion device of the type shown in FIG. 2 can be implemented.

Depending on the embodiment, it is possible to form a unit structure as shown in Fig. 9(b). That is, in the case of using the four winding transformer module 122, two primary-side modules 121 are connected to the primary side, and the secondary-side module 123 and the balancing module 124 can be connected to the secondary side, respectively. In this case, a unit structure may be implemented by connecting the corresponding rectifiers 110 to each of the primary-side modules 121. Thereafter, a power conversion device may be implemented by combining a plurality of unit structures of FIG. 9(b). Further, even when the transformer module 122 is extended to the N winding, the power conversion device can be implemented in the same manner.

The present invention is not limited by the above-described embodiments and the accompanying drawings. It will be apparent to those of ordinary skill in the art to which the present invention pertains, that components according to the present invention can be substituted, modified, and changed within the scope of the technical spirit of the present invention.

100: power converter 110: rectifier
120: DC-DC converter 130: control unit
131: rectifier control module 132: DC-DC converter control module

Claims (17)

delete delete A plurality of rectifiers connected in series to an AC input power source and rectifying each of the divided voltages distributed from the input power to a DC link voltage;
A first output terminal connected to each of the plurality of rectifiers in series, converting the DC link voltage to DC-DC, and connected to a load, and a second output connected to an ESS (Energy Storage System) A DC-DC converter including a terminal; And
Controlling the plurality of rectifiers and DC-DC converters to independently maintain the output voltages of the first output terminals, and to perform balancing for the DC link voltage and the output currents of the second output terminals. Including a control unit,
Each of the second output terminals included in the DC-DC converters are connected in parallel with each other,
The DC-DC converter is
A primary-side module converting the DC link voltage into a first AC voltage;
A transformer module configured to transform the first AC voltage into a second AC voltage according to a set winding ratio and output the second AC voltage to a plurality of transformer terminals;
A secondary module connected to any one of the transformer terminals and configured to rectify the second AC voltage and provide an output voltage to the first output terminal; And
It is connected to the other one of the transformer terminals and supplies the balancing power provided from the transformer module to the other DC-DC converter connected in parallel, or regenerates the balancing power delivered from the other DC-DC converter to the secondary module. It includes a balancing module,
The control unit
A rectifier control module for controlling a switching operation of the rectifier so that the magnitude of the ESS current, which is the sum of the output currents of the second output terminal, has a reference ESS current value; And
Controls the switching operation of the secondary module and the balancing module so that the magnitudes of the individual DC link voltages applied to each of the DC-DC converters match and output voltages corresponding to each load are output to the first output terminal. A power conversion device comprising a DC-DC converter control module.
The method of claim 3, wherein the rectifier control module
The power conversion device, characterized in that receiving the magnitude of the ESS current from the ESS current meter located between the power storage device and the second output terminal.
The method of claim 3, wherein the DC-DC converter control module
Power characterized in that receiving the DC link voltage from each DC link voltage measuring device located between the rectifier and the DC-DC converter, and receiving the output voltage from an output voltage measuring device located at the first output terminal Inverter.
The method of claim 3,
The DC-DC converter includes a plurality of the secondary side modules,
Wherein the secondary modules are individually connected to the transformer terminals.
The method of claim 3, wherein the balancing module
A power conversion device comprising a plurality of switches, and performing a supply operation or a regenerative operation of the balancing power according to a switching operation method of each of the switches.
The method of claim 3, wherein the balancing module
And charging or discharging the balancing power to the power storage device connected to the second output terminal under the control of the controller.
The method of claim 8, wherein the power storage device
Power conversion device comprising a plurality of batteries (battery).
The method of claim 3, wherein the DC-DC converter control module
Regardless of the magnitude of the output current output from the second output terminal, the DC link voltage (V_dc_prik) is controlled to have an average value (V_dc_pri_ref) of the magnitude of each DC link voltage (V_dc_prik). Power converter.
The method of claim 3, wherein the input power is
Power conversion device, characterized in that the three-phase circuit.
delete delete delete In the power conversion device connected to an AC input power source to provide a plurality of output voltages,
The power conversion device includes a plurality of unit structures connected in series to the input power source,
The unit structure is
A rectifier for rectifying the divided voltage distributed from the input power to a DC link voltage; And
It is connected in series to the rectifier, converts the DC link voltage to DC-DC, and includes a first output terminal connected to a load, and a second output terminal connected to an ESS (Energy Storage System). Including a DC-DC converter,
The DC-DC converter is
A primary-side module converting the DC link voltage into a first AC voltage;
A three-winding transforming module converting the first AC voltage into a second AC voltage according to a set winding ratio and outputting the second AC voltage to a first transforming terminal and a second transforming terminal;
A secondary module connected to the first transforming terminal and rectifying the second AC voltage to provide an output voltage to the first output terminal; And
The secondary module is connected to the second transformer terminal and supplies the balancing power provided from the transformer module to the outside of the unit structure through the second output terminal or the balancing power delivered through the second output terminal. It includes a balancing module to regenerate into,
Each of the second output terminals included in the plurality of unit structures are connected in parallel with each other,
By controlling the rectifier and DC-DC converter of the unit structure, the output voltages of the first output terminals are independently maintained, and the DC link voltage and the output current of the second output terminals are balanced. Further comprising a control unit,
The control unit
A rectifier control module for controlling a switching operation of the rectifier so that the magnitude of the ESS current, which is the sum of the output currents of the second output terminal, has a reference ESS current value; And
Controls the switching operation of the secondary module and the balancing module so that the magnitudes of the individual DC link voltages applied to each of the DC-DC converters match and output voltages corresponding to each load are output to the first output terminal. A power conversion device comprising a DC-DC converter control module.
The method of claim 15, wherein the rectifier control module
The power conversion device, characterized in that receiving the magnitude of the ESS current from the ESS current meter located between the power storage device and the second output terminal.
The method of claim 15, wherein the DC-DC converter control module
The DC link voltage is inputted from each DC link voltage measuring device positioned between the rectifier of the unit structure and the DC-DC converter, and the output voltage is received from an output voltage measuring device positioned at the first output terminal. Power converter.

Images