Power Conversion Equipment

Abstract

To provide a power converter that can alone output different voltages of a plurality of systems through simple control and avoid cutoff of current in an inverter.SOLUTION: A power converter according to an embodiment comprises: a chopper that converts power from a power supply into DC power and outputs the DC power; an inverter that converts the DC power output from the chopper into AC power; a plurality of resonance capacitors that are connected in dual series with a DC input part of the inverter; a plurality of high frequency transformers that have primary winding connected with the midpoint between the inverter and the plurality of resonance capacitors and convert the AC power of the inverter; a plurality of rectifiers that convert AC power supplied from secondary winding of the plurality of high frequency transformers into DC power; one or more voltage detectors that detect output voltage from any one of the plurality of rectifiers; and a control unit that controls the chopper based on output from the voltage detectors so that an output voltage of the DC power becomes a predetermined voltage value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD An embodiment of the present invention relates to a power conversion device. [Background technology]

[0002] When supplying power from a high-voltage system to a low-voltage load, not only is it necessary to convert the voltage value, but it also requires isolation using a transformer (isolation transformer). In a power conversion device that uses an isolation transformer, DC power is converted to AC power and input to the primary side of the isolation transformer, and the output from the secondary side is rectified to convert it back to DC power. The higher the frequency of the AC power input to the isolation transformer, the more compact the isolation transformer can be, which enables the miniaturization of the system. One configuration of a high-frequency isolation type power conversion device includes a chopper that converts the power supplied from a power supply circuit into the desired DC power, an inverter that converts the DC power of the chopper into high-frequency AC power, a high-frequency transformer (isolation transformer) excited by the high-frequency AC current supplied from the inverter, and a rectifier that converts the high-frequency AC power into DC power.In addition, by applying a resonant circuit that utilizes the resonant action due to the electrostatic capacitance and inductance on the circuit, the switching loss of the inverter can be significantly reduced, making high-frequency switching of the inverter possible. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-83658 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in some power conversion systems, there are multiple loads with different rated voltages, and therefore multiple systems of different voltage outputs are required. In response to this, there is a problem that the system becomes larger and more expensive when multiple power conversion devices are installed. Furthermore, when controlling the output voltages of a plurality of systems with a single power conversion device, there is a risk that the control system will become complicated and that the current in the resonant circuit will be cut off, resulting in increased loss in the inverter and the generation of surge voltages. The present invention has been made in consideration of the above, and aims to provide a high-frequency isolation type power conversion device that can output different voltages from multiple systems with a single unit through simple control and that can avoid current interruption in the inverter. [Means for solving the problem]

[0005] The power conversion device according to the embodiment includes: a chopper that converts power from a power source into DC power and outputs the DC power; The chopper has a switching element constituting an upper arm and a switching element constituting a lower arm connected to a DC output side of the chopper, and a plurality of resonant capacitors connected in series, Converts the DC power output by the chopper into AC power resonance Inverter and, The primary winding The midpoint between the switching elements constituting the upper arm and the switching elements constituting the lower arm and Two in series The midpoint of the resonant capacitor and a plurality of high frequency transformers connected to said inverter for converting AC power, a plurality of rectifiers for converting AC power supplied from secondary windings of said plurality of high frequency transformers into DC power, one or a plurality of voltage detectors for detecting an output voltage of any one of said plurality of rectifiers, and a control device for controlling a chopper based on an output of said voltage detector so that an output voltage of said DC power becomes a predetermined voltage value. The period during which the switching elements constituting the inverter are on is made longer than the conduction period of the resonant current flowing through the primary windings of the multiple high frequency transformers. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a power conversion device according to a first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram of a current path during an on-period of an upper arm of the resonant inverter of the power conversion device according to the first embodiment. [Diagram 3] FIG. 3 is an explanatory diagram of a current path during an on-period of a lower arm of the resonant inverter of the power conversion device according to the first embodiment. [Figure 4] FIG. 4 is an explanatory diagram of current waveforms during the on-period of the upper arm and the lower arm of the resonant inverter of the power conversion device according to the first embodiment. [Diagram 5]FIG. 5 is an explanatory diagram of conventional chopper control. [Figure 6] FIG. 6 is an explanatory diagram of voltages at various parts of the power conversion device according to the first embodiment. [Figure 7] FIG. 7 is a diagram illustrating control of the chopper of the power conversion device according to the first embodiment for suppressing the occurrence of a ripple voltage. [Figure 8] FIG. 8 is a diagram illustrating a schematic configuration of a power conversion device according to the second embodiment. [Figure 9] FIG. 9 is an explanatory diagram of chopper control in the power conversion device according to the second embodiment. [Figure 10] FIG. 10 is a diagram illustrating a schematic configuration of a power conversion device according to the third embodiment. [Figure 11] FIG. 11 is an explanatory diagram of chopper control in the power conversion device according to the third embodiment. [Figure 12] FIG. 12 is an explanatory diagram of chopper control in the power conversion device according to the fourth embodiment. [Figure 13] FIG. 13 is an explanation of the control of the chopper of the power conversion device according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, an embodiment will be described with reference to the drawings. [1] First embodiment FIG. 1 is a diagram illustrating a schematic configuration of a power conversion device according to a first embodiment. 2. Description of the Related Art In order to ensure insulation between the primary side and the secondary side, a transformer is known that insulates the primary side from the secondary side by using a transformer that has a pair of electromagnetically coupled windings (coils). The power conversion system 100 of the embodiment includes a power conversion device 1 having a transformer, and a power supply device 2.

[0008] However, the lower the excitation frequency, the larger the transformer becomes. For example, a transformer with an excitation frequency set to correspond to the 50 Hz / 60 Hz frequency of a commercial power supply becomes large. Therefore, the power conversion device 1 of the present embodiment uses a high-frequency transformer to insulate the primary side from the secondary side and achieve a compact size.

[0009] Here, the configuration of the power conversion device 1 will be described in detail. The power conversion device 1 includes a resonant inverter 11, a first diode rectifier 12, a second diode rectifier 13, a first high-frequency transformer 21, a second high-frequency transformer 22, a chopper 31, an input terminal TI of an input system of the power conversion device 1, an output terminal TO1 of a first output system of the power conversion device 1, an output terminal TO2 of a second output system of the power conversion device 1, a voltage detector 51 that detects the voltage of the output terminal TO1, and a control device 41 that receives a voltage detection signal DS51 from the voltage detector 51 and controls the resonant inverter 11 and the chopper 31.

[0010] The input terminal TI is connected to a power supply circuit 2 having a power supply 2A, a transformer 2B and a rectifier 2C. Here, when the rectifier 2C is configured as a diode bridge, the voltage at the input terminal TI fluctuates, so the power input from the power supply circuit 2 is converted into DC power of a predetermined voltage by the chopper 31 and output to the resonant inverter 11, thereby suppressing the voltage fluctuation.

[0011] The resonant inverter 11 uses DC power supplied from the chopper 31 to supply AC power to the first high-frequency transformer 21 and the second high-frequency transformer 22. The resonant inverter 11 is configured as, for example, a resonant type single-phase half-bridge inverter.

[0012] The resonant inverter 11 includes a filter capacitor C1, a first switching transistor S1, a second switching transistor S2, a first resonant capacitor RC1, a second resonant capacitor RC2, a third resonant capacitor RC3, and a fourth resonant capacitor RC4.

[0013] A primary winding of the first high frequency transformer 21 is connected to a midpoint between the first switching transistor S1 and the second switching transistor S2. Similarly, a primary winding of the first high frequency transformer 21 is connected to a midpoint between the first resonant capacitor RC1 and the second resonant capacitor RC2 connected in series.

[0014] The resonant inverter 11 supplies AC power to the first high frequency transformer 21 by alternately turning on and off the first switching transistor S1 and the second switching transistor S2 under the control of the control device 41.

[0015] A primary winding of the second high-frequency transformer 22 is connected to a midpoint between the first switching transistor S1 and the second switching transistor S2. Similarly, a primary winding of the second high-frequency transformer 22 is connected to a midpoint between the third resonant capacitor RC3 and the fourth resonant capacitor RC4, which are connected in series.

[0016] The resonant inverter 11 supplies AC power to the second high-frequency transformer 22 by alternately turning on and off the switching transistor S1 and the second switching transistor S2 under the control of the control device 41.

[0017] In the following description, the first switching transistor S1 side of the resonant inverter 11 is referred to as an upper arm of the resonant inverter 11, and the second switching transistor S2 side of the resonant inverter 11 is referred to as a lower arm of the resonant inverter 11.

[0018] The first high-frequency transformer 21 is configured as an isolation transformer having a primary winding (primary winding) that generates magnetic flux, and a secondary winding (secondary winding) that is insulated from the primary winding and excited by the magnetic flux generated in the primary winding. When an AC current is supplied from the resonant inverter 11 to the primary winding of this first high frequency transformer 21, a magnetic flux is generated in the primary winding. The magnetic flux generated in the primary winding generates an induced current in the secondary winding. As a result, the first high frequency transformer 21 supplies power to the secondary side according to the AC current input from the primary side.

[0019] The diode rectifier 12 is a circuit that rectifies the power generated in the secondary winding of the first high-frequency transformer 21, and in Fig. 1, it includes a diode bridge (rectifier bridge) in which a plurality of diodes are combined, and a filter capacitor 21. Here, the filter capacitor C21 smoothes the DC voltage rectified by the diode rectifier 12.

[0020] Furthermore, reactor 23 smoothes the DC current rectified by diode rectifier 12 . A filter capacitor C22 stabilizes the voltage at the output terminal TO1.

[0021] The second high-frequency transformer 22 is an insulating transformer having a primary winding (primary winding) that generates magnetic flux, and a secondary winding (secondary winding) that is insulated from the primary winding and excited by the magnetic flux generated in the primary winding. When an AC current is supplied from the resonant inverter 11 to the primary winding of the second high-frequency transformer 22, a magnetic flux is generated in the primary winding. The magnetic flux generated in the primary winding generates an induced current in the secondary winding. As a result, the second high-frequency transformer 22 supplies power to the secondary side according to the AC current input from the primary side.

[0022] The diode rectifier 13 is a circuit that rectifies the power generated in the secondary winding of the second high-frequency transformer 22, and includes, for example, a diode bridge (rectifier bridge) in which a plurality of diodes are combined, and a filter capacitor C31. Here, the filter capacitor C31 smoothes the DC voltage rectified by the diode rectifier 13.

[0023] Furthermore, reactor 24 smoothes the DC current rectified by diode rectifier 13 . Filter capacitor C32 stabilizes the voltage at output terminal TO2. The DC power output from the output terminal TO1 and the output terminal TO2 is used to directly supply power to a DC load, or the voltage is converted by a converter such as an inverter (not shown) before supplying power to the load.

[0024] In this case, the voltage detector 51 detects the output voltage value of the output terminal TO1 and inputs it to the control device 41 as a voltage detection signal DS51.

[0025] As a result, the control device 41 controls the resonant inverter 11 and the chopper 31 based on the voltage detection signal DS51. In this case, the control device 41 is configured as, for example, a logic circuit that generates a pulse signal. Alternatively, the control device 41 may be configured to include a microprocessor that is a calculation element (computer) that executes calculation processing, and a memory that stores a program and data used in the program, and generate a pulse signal by the microprocessor executing the program.

[0026] The control device 41 controls the conduction ratio of the chopper 31 so that the output voltage of the output terminal TO1 becomes a predetermined voltage value. In this embodiment, the control device 41 controls the conduction ratio of the upper arm and the lower arm of the resonant inverter 11, i.e., the on-period of each arm, to be constant.

[0027] In this case, the output voltage at output terminal TO2 will not be constant but will fluctuate slightly, but in a system in which a converter such as an inverter is connected to output terminal TO2, this will not be a problem as long as the voltage fluctuation of the output voltage is within a controllable range.

[0028] The above explanation was for the case where the power conversion device has two output systems, but a similar configuration can also be achieved for three or more systems by providing a pair of resonant capacitors connected in series in parallel with the filter capacitor C1, similar to the first resonant capacitor RC1 and the second resonant capacitor RC2, and a high-frequency transformer.

[0029] Next, the operation of the first embodiment will be described. FIG. 2 is an explanatory diagram of a current path during an on-period of an upper arm of the resonant inverter of the power conversion device according to the first embodiment.

[0030] As shown in FIG. 2, a first resonant capacitor RC1, a second resonant capacitor RC2, a filter capacitor C1, a first switching transistor S1 (upper arm) of the resonant inverter 11, a first high-frequency transformer 21, and a first diode rectifier 12 form a resonant circuit.

[0031] At this time, the circuit constants that contribute to the resonant frequency of the resonant current flowing through the first high-frequency transformer 21 are dominated by the capacitance of the first resonant capacitor RC1 and the second resonant capacitor RC2, the leakage inductance of the first high-frequency transformer 21, and the conductor inductance of the current path.

[0032] Similarly, the third resonant capacitor RC3 and the fourth resonant capacitor RC4, the filter capacitor C1, the first switching transistor S1 (upper arm) of the resonant inverter 11, the second high frequency transformer 22, and the second diode rectifier 13 form a resonant circuit.

[0033] At this time, the circuit constants that contribute to the resonant frequency of the resonant current flowing through the second high-frequency transformer 22 are dominated by the capacitance of the third resonant capacitor RC3 and the fourth resonant capacitor RC4, the leakage inductance of the second high-frequency transformer 22, and the conductor inductance of the current path.

[0034] FIG. 3 is an explanatory diagram of a current path during an on-period of a lower arm of the resonant inverter of the power conversion device according to the first embodiment.

[0035] The first resonant capacitor RC1, the second resonant capacitor RC2, the filter capacitor C1, the second switching transistor S2 (lower arm) of the resonant inverter 11, the first high frequency transformer 21, and the first diode rectifier 12 form a resonant circuit.

[0036] At this time, the circuit constants that contribute to the resonant frequency of the resonant current flowing through the first high-frequency transformer 21 are dominated by the capacitance of the first resonant capacitor RC1 and the second resonant capacitor RC2, the leakage inductance of the first high-frequency transformer 21, and the conductor inductance of the current path.

[0037] Similarly, the third resonant capacitor RC3 and the fourth resonant capacitor RC4, the filter capacitor C1, the second switching transistor S2 (lower arm) of the resonant inverter 11, the second high frequency transformer 22, and the second diode rectifier 13 form a resonant circuit.

[0038] At this time, the circuit constants that contribute to the resonant frequency of the resonant current flowing through the second high-frequency transformer 22 are dominated by the capacitance of the third resonant capacitor RC3 and the fourth resonant capacitor RC4, the leakage inductance of the second high-frequency transformer 22, and the conductor inductance of the current path.

[0039] 2 and 3, the current path includes diode rectifiers 12 and 13. Therefore, when the polarity of the resonant current is reversed, it becomes opposite to the diode polarity, and therefore, when the resonant current reaches 0, the resonant current stops flowing.

[0040] In addition, the current paths of the resonant current flowing through the first high-frequency transformer 21 and the resonant current flowing through the second high-frequency transformer 22 overlap only in the resonant inverter 11 and the filter capacitor C1 of the resonant inverter, but the resonant capacitor and the high-frequency transformer that contribute to the resonant frequency are separated. For this reason, the mutual interference of the resonant operations can be ignored, and the conduction periods of the resonant currents can be regarded as constant.

[0041] FIG. 4 is an explanatory diagram of current waveforms during the on-period of the upper arm and the lower arm of the resonant inverter of the power conversion device according to the first embodiment. In the following description, it is assumed that the resonant current flowing through the primary winding of first high-frequency transformer 21 has a longer conduction period than the resonant current flowing through the primary winding of second high-frequency transformer 22.

[0042] The output current of resonant inverter 11 is the sum of the resonant current flowing through the primary winding of first high-frequency transformer 21 and the resonant current flowing through the primary winding of second high-frequency transformer 22 .

[0043] Therefore, the conduction period of the output current of the resonant inverter 11 is determined by the resonant current flowing through the primary winding of the transformer 21, which has a long conduction period.

[0044] Therefore, if the on-period of the first switching transistor S1 (upper arm) and the on-period of the second switching transistor S2 (lower arm) of the resonant inverter 11 are made longer than the conduction periods of all resonant currents flowing through the transformer, current interruption in the resonant inverter 11 will not occur.

[0045] Moreover, the on-period of the first switching transistor S1 (upper arm) and the on-period of the second switching transistor S2 (lower arm) of the resonant inverter 11 are fixed to values ​​close to the conduction period of the resonant current. This reduces the RMS value of the resonant current, making it possible to reduce circuit loss. Incidentally, if the on-period of resonant inverter 11 is fixed, it cannot be used for control, so as described above, the conduction rate is controlled by chopper 31 so that the output voltage at output terminal TO1 becomes a predetermined voltage value.

[0046] Here, a conventional chopper control will be described. FIG. 5 is an explanatory diagram of conventional chopper control. In FIG. 5, for ease of understanding, the same reference numerals as in the first embodiment are used. In conventional chopper control, the difference between the voltage command value and the value of the voltage detection signal DS51 output by the voltage detector 51 is input to a PI control unit 61 that performs proportional-integral control, and the calculation result is input to a triangular wave comparator 62 to obtain the gate signal GS of the chopper 31.

[0047] However, if the gain of the PI control section cannot be increased due to performance constraints of the control device 41, the average voltage of the output terminal TO1 can be kept constant, but the periodically fluctuating ripple voltage cannot be suppressed, and there is a risk that the voltage fluctuation will exceed the specified value.

[0048] FIG. 6 is an explanatory diagram of voltages at various parts of the power conversion device according to the first embodiment. For example, when a single-phase inverter is connected to output terminal TO2 and outputs a single-phase AC voltage of 50 Hz or 60 Hz, as shown in FIG. 6, the AC power pulsates at 100 Hz or 120 Hz, which is twice the frequency of the output AC voltage.

[0049] Due to the influence of this power pulsation, a ripple voltage of 100 Hz or 120 Hz may occur in the output voltage VTO2 at the output terminal TO2. The power pulsation also generates a ripple voltage in the voltage VC1 of the filter capacitor C1 of the resonant inverter 11, which is the power supply source, and as a result, a ripple voltage also occurs in the output voltage VTO1 at the output terminal TO1. Therefore, in the first embodiment, the occurrence of ripple voltage is suppressed.

[0050] FIG. 7 is a diagram illustrating control of the chopper of the power conversion device according to the first embodiment for suppressing the occurrence of a ripple voltage. The ripple voltage extracting section 63 extracts a ripple voltage in a specific ripple voltage frequency band contained in the voltage detection signal DS51 corresponding to the voltage at the output terminal TO1 detected by the voltage detector 51.

[0051] In this case, the ripple voltage can be extracted using a bandpass filter or FFT. Then, the ripple voltage suppression control unit 64 receives the extracted ripple voltage value as an input, calculates an output value of the ripple voltage frequency band so as to reduce the ripple voltage, outputs the calculated value to the adder 65, and adds it to the output value of the PI control 61.

[0052] As a result, the effective voltage command value input to the triangular wave comparing section 62 suppresses the influence of the ripple voltage. Therefore, in the first embodiment, the gate signal GS of the chopper 31 output from the triangular wave comparison unit 62 suppresses the occurrence of a ripple voltage due to power pulsation. As described above, according to the first embodiment, power conversion can be performed while suppressing ripple voltages in the voltage VTO2 at the output terminal TO2, the voltage VC1 of the filter capacitor C1, and the output voltage VTO1 at the output terminal TO1.

[0053] [2] Second embodiment Next, a second embodiment will be described. FIG. 8 is a diagram illustrating a schematic configuration of a power conversion device according to the second embodiment. In FIG. 8, the same parts as those in the first embodiment in FIG. 1 are denoted by the same reference numerals. The second embodiment differs from the first embodiment in that a voltage detector 52 is provided that detects the voltage VTO2 at the output terminal TO2 and outputs a voltage detection signal DS52.

[0054] FIG. 9 is an explanatory diagram of chopper control in the power conversion device according to the second embodiment. In the first embodiment, as explained with reference to Fig. 6, there is a risk that a ripple voltage may also occur at the output terminal TO2. For this reason, in the present second embodiment, the voltage detection signal DS52 output by the voltage detector 52 is used as an input value of the ripple voltage extraction unit 63.

[0055] The ripple voltage extracting section 63 extracts a ripple voltage in a specific ripple voltage frequency band contained in the voltage detection signal DS52 that corresponds to the output voltage VTO2 at the output terminal TO2 detected by the voltage detector 52.

[0056] Then, the ripple voltage suppression control unit 64 receives the extracted ripple voltage value as an input, calculates an output value of the ripple voltage frequency band so as to reduce the ripple voltage, outputs the calculated value to the adder 65, and adds it to the output value of the PI control 61.

[0057] As a result, the effective voltage command value input to the triangular wave comparing section 62 suppresses the influence of the ripple voltage appearing at the second output terminal TO2.

[0058] Therefore, according to the second embodiment, in addition to the effects of the first embodiment, the gate signal GS of the chopper 31 output from the triangular wave comparison unit 62 can more reliably suppress the effects of the ripple voltage appearing in the output voltage VTO2 at the second output terminal TO2.

[0059] [3] Third embodiment Next, a third embodiment will be described. FIG. 10 is a diagram illustrating a schematic configuration of a power conversion device according to the third embodiment. In FIG. 10, the same parts as those in the first embodiment in FIG. 1 are denoted by the same reference numerals. The third embodiment differs from the first embodiment in that a voltage detector 53 is added, which detects the voltage of the filter capacitor C1 of the resonant inverter 11 and outputs a voltage detection signal DS53.

[0060] FIG. 11 is an explanatory diagram of chopper control in the power conversion device according to the third embodiment. In the first embodiment, as described with reference to FIG. 6, there is a risk that a ripple voltage will also occur in the filter capacitor C1 of the resonant inverter 11.

[0061] For this reason, in the third embodiment, the voltage detection signal DS53 output by the voltage detector 53 is used as an input value of the ripple voltage extraction unit 63. The ripple voltage extracting unit 63 extracts a ripple voltage in a specific ripple voltage frequency band contained in the voltage detection signal DS53 corresponding to the output voltage VC1 of the filter capacitor C1 of the resonant inverter 11 detected by the voltage detector 53.

[0062] Then, the ripple voltage suppression control unit 64 receives the extracted ripple voltage value as an input, calculates an output value of the ripple voltage frequency band so as to reduce the ripple voltage, outputs the calculated value to the adder 65, and adds it to the output value of the PI control 61.

[0063] As a result, the effective voltage command value input to the triangular wave comparator 62 suppresses the influence of the ripple voltage appearing in the output voltage VC1 of the filter capacitor C1 of the resonant inverter 11.

[0064] Therefore, according to the third embodiment, in addition to the effects of the first embodiment, the gate signal GS of the chopper 31 output from the triangular wave comparison unit 62 can more reliably suppress the effects of the ripple voltage appearing in the output voltage VC1 of the filter capacitor C1 of the resonant inverter 11.

[0065] [4] Fourth embodiment FIG. 12 is an explanatory diagram of chopper control in the power conversion device according to the fourth embodiment. FIG. 12 is a diagram illustrating a schematic configuration of a power conversion device according to the fourth embodiment. In FIG. 12, the same parts as those in the first embodiment in FIG. 1 are denoted by the same reference numerals.

[0066] The fourth embodiment differs from the first embodiment in that a current detector 54 that detects the current in the second reactor 24 and outputs a current detection signal DS54 is added.

[0067] FIG. 13 is an explanation of the control of the chopper of the power conversion device according to the fourth embodiment. Incidentally, like the ripple voltage, a ripple current also occurs in the current of the reactor 24, but the ripple current is greater than the ripple voltage in terms of its ratio to the DC value. Even if the ripple voltage is reduced, a ripple current still occurs due to power pulsation.

[0068] Therefore, in the fourth embodiment, the ripple voltage extraction unit 63 extracts a ripple voltage in a specific ripple voltage frequency band contained in the voltage detection signal DS51 corresponding to the voltage of the output terminal TO1 detected by the voltage detector 51, and sets the extracted ripple voltage as a first input value of the ripple voltage suppression control 64.

[0069] Furthermore, based on the current detection signal DS54 output by the current detector 54, a ripple current is extracted by a ripple current extractor 65 and used as a second input value for a ripple voltage suppression control 64. As a result, the ripple voltage suppression control unit 64 receives the extracted ripple voltage value as a first input and the extracted ripple current value as a second input, calculates an output value of the ripple voltage frequency band so as to reduce the ripple voltage, outputs the output to the adder 65, and adds it to the output value of the PI control 61.

[0070] As a result, the effective voltage command value input to the triangular wave comparison unit 62 takes into account the ripple current and thus suppresses with high precision the effects of the ripple voltage appearing in the voltage VTO2 at the output terminal TO2, the voltage VC1 of the filter capacitor C1, and the output voltage VTO1 at the output terminal TO1. Therefore, according to the fourth embodiment, in addition to the effects of the first embodiment, the gate signal GS of the chopper 31 output from the triangular wave comparison unit 62 takes into account the effects of the ripple current, and the occurrence of ripple voltage can be more reliably suppressed.

[0071] Although the embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0072] For example, a method may be executed by a power conversion device including a chopper that converts power from a power source into DC power and outputs it, an inverter that converts the DC power output by the chopper into AC power, a plurality of resonant capacitors connected in series to a DC input section of the inverter, a plurality of high-frequency transformers whose primary windings are connected to a midpoint between the inverter and the plurality of resonant capacitors and that convert the AC power of the inverter, and a plurality of rectifiers that convert the AC power supplied from secondary windings of the plurality of high-frequency transformers into DC power, the method may include a step of detecting an output voltage of any of the plurality of rectifiers, and a step of controlling the chopper based on a result of the voltage detection so that the output voltage of the DC power becomes a predetermined voltage value.

[0073] Also, a program for controlling a power conversion device using a computer may be provided, the power conversion device including a chopper that converts power from a power source into DC power and outputs it, an inverter that converts the DC power output by the chopper into AC power, a plurality of resonant capacitors connected in series to a DC input section of the inverter, a plurality of high-frequency transformers whose primary windings are connected to a midpoint between the inverter and the plurality of resonant capacitors and that convert the AC power of the inverter, and a plurality of rectifiers that convert the AC power supplied from the secondary windings of the plurality of high-frequency transformers into DC power, and the program may be provided to cause the computer to function as a means for detecting the output voltage of any of the plurality of rectifiers and a means for controlling the chopper so that the output voltage of the DC power becomes a predetermined voltage value based on the result of the voltage detection. [Explanation of symbols]

[0074] 100...Power conversion system 1...Power conversion device 2…Power circuit 11...Resonant inverter 12...First diode rectifier 13...Second diode rectifier 21...First high frequency transformer 22...Second high frequency transformer 23…First reactor 24…Second reactor 31...Chopper 41...Control device 51~53: Voltage detector 54...Current detector 61...PI control unit 62...Triangle wave comparison section 63…Ripple voltage extraction section 64...Ripple voltage suppression control section 65...Ripple current extraction section C1, C21, C22, C31, C32...Filter capacitors RC1~RC4: 1st resonant capacitor~4th resonant capacitor S1: First switching transistor (upper arm) S2: Second switching transistor (lower arm) TI: Input terminal TO1, TO2...Output terminals.

Claims

1. A chopper that converts power from a power source into DC power and outputs it; a resonant inverter including a switching element constituting an upper arm and a switching element constituting a lower arm connected to a DC output side of the chopper, and a plurality of resonant capacitors connected in series, and configured to convert the DC power output by the chopper into AC power; a plurality of high frequency transformers whose primary windings are connected to a midpoint between the switching elements constituting the upper arm and the switching elements constituting the lower arm and to a midpoint between the two series-connected resonant capacitors, for converting AC power of the inverter; a plurality of rectifiers for converting AC power supplied from secondary windings of the plurality of high frequency transformers into DC power; one or more voltage detectors for detecting an output voltage of any one of the plurality of rectifiers; a control device that controls the chopper based on an output of the voltage detector so that an output voltage of the DC power becomes a predetermined voltage value, a period during which a switching element constituting the inverter is turned on is set to be longer than a conduction period of a resonant current flowing through a primary winding of each of the plurality of high frequency transformers; Power conversion equipment.

2. the control device extracts a ripple voltage in a specific frequency band based on a detection value of the voltage detector, and controls the chopper so as to reduce the ripple voltage included in an output voltage of the DC power. The power conversion device according to claim 1 .

3. a plurality of voltage detectors each detecting an output voltage of a plurality of rectifiers among the plurality of rectifiers; the control device extracts a ripple voltage of a specific frequency band based on detection values ​​of the plurality of voltage detectors, and controls the chopper so as to reduce the ripple voltage included in the output voltage of the DC power. The power conversion device according to claim 1 .

4. a current detector for detecting a ripple current included in the output current of the DC power, the control device extracts a ripple current in a specific frequency band based on the ripple current detected by the current detector, and controls the chopper so as to reduce a ripple voltage included in an output voltage of the DC power. The power conversion device according to any one of claims 1 to 3.

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