Power conversion device

Abstract

In a controller (9) of an electric power converter (10), a switching frequency of a switching element (5) is determined based on a magnetic parameter of a magnetic component (3) and at least one of an electrical parameter of the electric power converter (10), and the switching frequency of the switching element (5) is changed in stages for each of M intervals based on any one of a predetermined time width and a predetermined electrical quantity amplitude, wherein M is an integer greater than 2, and a control frequency is a value obtained by dividing the switching frequency by an integer P greater than 2.

Description

Technical Field

[0001] The present application relates to a power conversion device. Background Art

[0002] In order to achieve the miniaturization and lightness of the power conversion device, the main method used is to increase the driving frequency of the switching element (hereinafter referred to as the switching frequency). When the switching frequency is always fixed at a high state, the switching loss increases, so research has been conducted to make the switching frequency variable according to the operating conditions (for example, refer to Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-186436 Summary of the invention

[0006] The power conversion device described in Patent Document 1 discontinuously switches the switching carrier frequency according to the phase of the input AC voltage of the rectifier circuit, and controls using various physical quantities sampled at the peak and / or trough of the carrier. When this technology is applied as it is to the case where the maximum value of the switching frequency required is high speed, the case where complex control processing is required, the case where a single microcomputer (hereinafter referred to as microcomputer) controls multiple power conversion devices, etc., the processing load of the microcomputer, i.e., the controller, increases.

[0007] The present application discloses a technology for solving the above-mentioned problems, and its object is to reduce the processing load of a controller.

[0008] The power conversion device disclosed in the present application comprises:

[0009] Power converters, including magnetic components and switching elements, perform power conversion; and

[0010] A controller controls the on / off state of the switching element according to the duty cycle of the switching element and the switching frequency of driving the switching element under a control period determined by the control frequency,

[0011] In the controller, the switching frequency is determined according to at least one of the magnetic parameters of the magnetic component and the electrical parameters of the power converter, and the switching frequency is changed in stages for each of M intervals according to any one of a predetermined time width and a predetermined electric quantity amplitude, where M is an integer greater than 2, and

[0012] The control frequency is a value obtained by dividing the switching frequency by an integer P that is greater than or equal to 2.

[0013] According to the power conversion device disclosed in the present application, the processing load of the controller can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram showing an example of a circuit configuration of a power conversion device according to Embodiment 1.

[0015] Figure 2 This is a block diagram showing a configuration example of hardware of the control device according to the first embodiment.

[0016] Figure 3 This is an operation waveform diagram of the power conversion device according to the first embodiment.

[0017] Figure 4 This is an operation waveform diagram of the power conversion device according to the second embodiment.

[0018] Figure 5 This is a diagram showing an example of a circuit configuration of a power conversion device according to the third embodiment.

[0019] Figure 6 This is an operation waveform diagram of the power conversion device according to the third embodiment.

[0020] Figure 7 This is an operation waveform diagram of the power conversion device according to the fourth embodiment.

[0021] (Explanation of symbols)

[0022] 1: AC power supply; 2: Input-side diode rectifier bridge circuit; 3: Power factor improving inductor; 4: Diode element; 5: Switching element; 6: Smoothing capacitor; 71: First voltage detector; 72: Second voltage detector; 73: First current detector; 74: Second current detector; 8: DC load; 9: Controller; 10: AC / DC converter; 11: Insulated DC / DC converter; 112: Insulating transformer; 114: Smoothing inductor; 115: Smoothing capacitor; 1111, 1112, 1113, 1114: Switching element; 1161: Load voltage detector; 1162: Load current detector. DETAILED DESCRIPTION

[0023] [Summary of this application]

[0024] The power conversion device disclosed in the present application comprises:

[0025] Power converters, including magnetic components and switching elements, perform power conversion; and

[0026] A controller controls the on / off state of the switching element according to the duty cycle of the switching element and the switching frequency of driving the switching element under a control period determined by the control frequency,

[0027] In the controller, the switching frequency is determined according to at least one of the magnetic parameters of the magnetic component and the electrical parameters of the power converter, and the switching frequency is changed in stages for each of M intervals according to any one of a predetermined time width and a predetermined electric quantity amplitude, where M is an integer greater than 2, and

[0028] The control frequency is a value obtained by dividing the switching frequency by an integer P that is greater than or equal to 2.

[0029] According to the power conversion device disclosed in the present application, the control frequency can be reduced to 1 / P relative to the switching frequency. As a result, the processing load of the controller (microcomputer) can be reduced in the case where the maximum switching frequency required is high speed, complex control processing is required, and multiple power conversion devices are controlled by one controller (microcomputer).

[0030] Here, the switching frequency is determined based on at least one of the magnetic parameters of the magnetic part and the electrical parameters of the power converter, but as the magnetic parameters of the magnetic part, the inductance, number of turns, effective cross-sectional area of ​​the magnetic core, and magnetic flux density of the magnetic core can be used, and as the electrical parameters of the power converter, the voltage, current, and power conditions can be used. In the first embodiment described below, as the magnetic parameter of the magnetic part, the magnetic flux density of the magnetic core of the reactor is used, and in the second embodiment, as the electrical parameter of the power converter, the current ripple of the input current of the power converter is used, and in the third embodiment, as the magnetic parameter of the magnetic part, the magnetic flux density of the magnetic core of the reactor or transformer is used, and in the fourth embodiment, as the electrical parameter of the power converter, the current ripple of the output current of the power converter is used.

[0031] In addition, as the predetermined time width and the predetermined power range, any one of an arbitrary time width, phase range, voltage range, current range or power range is used. In Embodiments 1 and 2, the half cycle of the input AC voltage phase is used as the predetermined time width, and in Embodiments 3 and 4, the operating range of the output voltage of the power converter is used as the predetermined power range.

[0032] Hereinafter, with reference to the accompanying drawings, a preferred embodiment of the power conversion device related to the present application is described. In addition, the same reference numerals are added to the same contents and corresponding parts, and their detailed description is omitted. Similarly, in the subsequent embodiments, repeated descriptions are omitted for the structures with the same reference numerals.

[0033] Implementation method 1.

[0034] The power conversion device according to Embodiment 1 will be described with reference to the drawings. Figure 1 1 is a diagram showing an example of a circuit configuration diagram of a power conversion device according to Embodiment 1, and includes an AC / DC converter 10 that converts AC power into DC power.

[0035] [Description of Circuit Configuration of Embodiment 1]

[0036] Figure 1 The power conversion device shown inputs AC power from an AC power source 1 to an AC / DC converter 10 as a power converter, and outputs DC power from the AC / DC converter 10 to a DC load 8. The AC / DC converter 10 includes an input-side diode rectifier bridge circuit 2, a power factor improvement reactor 3, a diode element 4, a switch element 5, and a smoothing capacitor 6. In addition, the AC / DC converter 10 as a power converter includes a controller 9 that controls the on / off of the switch element 5 by inputting detection signals from a first voltage detector 71, a second voltage detector 72, a first current detector 73, and a second current detector 74. In addition, in this example, a boost chopper circuit is shown as the AC / DC converter 10, but it can also be applied to a step-down circuit or a step-up / step-down circuit as long as it is a circuit including a reactor as a magnetic component.

[0037] The AC power source 1 is a commercial AC system or a home generator. The DC load 8 is not only a pure resistance load, but can also be composed of a high-voltage battery for vehicle driving or a lead battery or an electric double layer capacitor (EDLC) as a power source for automotive electronic products. In addition, the AC power source 1 or the DC load 8 is not limited to the above examples.

[0038] The power factor improving reactor 3 is a current reducing reactor having one end connected to the positive side output bus of the input side diode rectifier bridge circuit 2 and the other end connected to the connection point of the diode element 4 and the switch element 5. In addition, the power factor improving reactor 3 can be connected to the negative side output bus of the input side diode rectifier bridge circuit 2 and the source terminal of the switch element 5, or can be distributedly connected to both ends of the input and output bus of the input side diode rectifier bridge circuit 2.

[0039] The diode element 4 is not limited to the types such as fast recovery diode (FRD) and soft recovery diode (SBD), and materials such as SiC (Silicon Carbide), GaN (Gallium Nitride) or Ga2O3 (Gallium Oxide) may be used. Furthermore, a switching element may be used instead to perform synchronous rectification.

[0040] The switching element 5 is not limited to IGBT (Insulated Gate Bipolar Transistor) and MOSFET (Metal Oxide Semiconductor Field Effect Transistor), but SiC-MOSFET, GaN-FET, GaN-HEMT (High Electron Mobility Transistor) or Ga2O3-MOSFET may also be used.

[0041] In addition, Figure 1 The AC / DC converter 10 shown has a step-up chopper circuit configuration as described above, but may also have a semi-bridgeless or totem-pole configuration in which the input-side diode rectifier bridge circuit 2 is omitted.

[0042] The controller 9 of the power conversion device of the present application performs control calculation for each control cycle determined by the control frequency described below based on part or all of the detection values ​​of the first voltage detector 71, the second voltage detector 72, the first current detector 73, and the second current detector 74. In addition, the controller 9 controls the switching element 5 of the AC / DC converter 10. That is, the controller 9 sends a drive signal X to the gate of the switching element 5 based on part or all of the detection values ​​of the first voltage detector 71, the second voltage detector 72, the first current detector 73, and the second current detector 74, and controls the on and off of the switching element 5, so that the desired operation can be performed.

[0043] In addition, the controller 9 performs appropriate feedback calculation according to the operation mode of the power conversion device as described later, outputs the duty ratio duty_fb, and calculates the duty ratio duty of the switching element 5 .

[0044] Figure 21 is a block diagram showing an example of the hardware of the microcomputer in the controller 9. The hardware of the microcomputer is composed of a processor 100 and a storage device 101. Although not shown in the figure, the storage device 101 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. In addition, an auxiliary storage device such as a hard disk may be provided instead of the flash memory. The processor 100 outputs a drive signal X by executing a program input from the storage device 101. In this case, the program is input from the auxiliary storage device to the processor 100 via the volatile storage device. In addition, the processor 100 can output data such as a calculation result to the volatile storage device of the storage device 101, and can also save the data to the auxiliary storage device via the volatile storage device.

[0045] [Description of the operation based on constant magnetic flux density control]

[0046] First, the switching frequency of the switching element 5 and the control frequency of the controller 9 are controlled by taking the magnetic flux density B of the magnetic core of the power factor improving reactor 3 as an object. In the first embodiment, the variation of the output voltage Vout of the AC / DC converter 10 is set to zero, that is, a constant value.

[0047] Figure 3 It is an operation waveform diagram of the switching frequency and the control frequency in the AC / DC converter 10 and the controller 9 in the present embodiment, and shows the operation in one cycle of the AC power source 1 .

[0048] exist Figure 3 In A, the instantaneous value of the input voltage Vin from the AC power supply 1 (the output value of the first voltage detector 71) is full-wave rectified via the input-side diode rectifier bridge circuit 2 to become the input voltage |Vin|. In addition, the output voltage Vout (the output value of the second voltage detector 72) of the AC / DC converter 10 is as follows: Figure 3 A shows a constant DC voltage Vout. Figure 3 In A, Vin_rms represents the effective value of the input voltage Vin.

[0049] exist Figure 3 In B, the duty cycle duty of the switching element 5 changes in a manner that becomes 1 at the phase where the input voltage Vin becomes zero and becomes minimum at the phase where the input voltage Vin becomes a peak. This action can be expressed using the following formula (1). The duty cycle duty_vt obtained by the formula (1) and the duty cycle duty_fb obtained by the feedback operation described later are used to determine the duty cycle duty of the switching element 5. Specifically, the duty cycle duty_fb is used as a feedback term and the duty cycle duty_vt is used as a feedforward term, so that only the feedback term or the sum of the feedback term and the feedforward term becomes the duty cycle duty of the switching element 5.

[0050] [Mathematical formula 1]

[0051]

[0052] On the other hand, the magnetic flux density B of the magnetic core of the power factor improving inductor 3 is expressed by the following formula (2). In formula (2), N is the number of turns of the power factor improving inductor 3, Ae is the effective cross-sectional area of ​​the magnetic core of the power factor improving inductor 3, and fsw is the switching frequency of the switching element 5.

[0053] [Mathematical formula 2]

[0054]

[0055] When the output voltage Vout is constant and the switching frequency fsw of the switching element 5 is fixed to a predetermined value, for example, the switching frequency fsw_max, and when the magnetic flux density B of the magnetic core of the power factor improving inductor 3 decreases as the input voltage Vin decreases, even if the magnetic flux density B of the magnetic core of the power factor improving inductor 3 becomes zero, since the switching element 5 operates at the fixed switching frequency fsw_max, under light load conditions, the proportion of switching loss to the overall loss becomes larger, resulting in a decrease in power conversion efficiency.

[0056] In contrast, in this embodiment, if Figure 3 C and Figure 3 As shown in D, the magnetic flux density B of the magnetic core of the power factor improving reactor 3 is obtained by feedback calculation according to equation (2) to be a set value ( Figure 3 D B theoretical value) in the case of switching frequency ( Figure 3 That is, in addition to the feedback control of the duty cycle duty, the switching frequency fsw at which the magnetic flux density B of the magnetic core of the power factor improving reactor 3 determined by the formula (2) becomes a set value less than the maximum value Bmax is derived by feedback calculation.

[0057] Here, the switching frequency fsw of the switching element 5 changes instantaneously and dynamically in a half cycle of the phase of the input voltage Vin.

[0058] Therefore, in the present embodiment, in order to realize a stable change in the switching frequency fsw of the switching element 5, the switching frequency (fsw) is set to a value at which the magnetic flux density B of the magnetic core of the power factor improving reactor 3 derived above becomes equal to or less than the maximum value Bmax. Figure 3 The fsw theoretical value of C is controlled so as to change in a step-wise manner for each of M (M is an integer greater than or equal to 2) intervals according to the half cycle of the phase of the input voltage Vin.

[0059] Specifically, if Figure 3 As shown in E, the half cycle of the phase of the input voltage Vin is divided into M intervals, and the switching frequency fsw in each interval is calculated in such a way that the magnetic flux density B of the magnetic core of the power factor improving inductor 3 becomes a set value below the maximum value Bmax at the starting point of each interval in time.

[0060] At this time, when the input voltage Vin is zero, after the switching frequency of the switching element 5 is made zero, according to the relationship of formula (2), the magnetic flux density of the magnetic core of the power factor improving reactor 3 theoretically diverges to infinity. Therefore, near the zero crossing of the input voltage Vin, the switching frequency fsw of the switching element 5 is made to be a non-zero frequency smaller than the switching frequency fsw at the time point when the input voltage Vin becomes maximum. For example, by Figure 3 The minimum value fsw_min of the switching frequency of the switching element 5 set as shown in E is set as the lower limit value, and the switching frequency is controlled in a manner to be the minimum value fsw_min near the zero crossing, which can suppress the divergence of the magnetic flux density B. In addition, the increase and decrease relationship between the switching frequency fsw and the magnetic flux density B of the magnetic core of the power factor improving inductor 3 is not limited to this.

[0061] In addition, in the above, the switching frequency ( Figure 3 C fsw theoretical value), but a feedforward operation may be used in addition to the feedback operation. That is, a feedforward operation using the following formula (3) may be added to derive the switching frequency fsw of the switching element 5 at which the magnetic flux density of the power factor improving reactor 3 becomes the set value, and control the switching frequency fsw.

[0062] Specifically, the input voltage Vin obtained from the first voltage detector 71, the output voltage Vout obtained from the second voltage detector 72, the number of turns N of the power factor improving reactor 3, the effective cross-sectional area Ae of the magnetic core, and the command value Bref of the magnetic flux density of the magnetic core set in advance are substituted into the formula (3), and the obtained feedforward operation term is added to the feedback control operation term of the feedback control, and the switching frequency fsw is derived as a set value at which the magnetic flux density B of the magnetic core of the power factor improving reactor 3 becomes less than the maximum value Bmax. Then, the switching frequency fsw is controlled so as to change stepwise for each of the arbitrary integer M intervals according to the half cycle of the phase of the input voltage Vin. In addition, for the output voltage Vout, not only the detection value obtained from the second voltage detector 72 but also the control command value can be used when setting the control command value.

[0063] Alternatively, the switching frequency fsw ( Figure 3 fsw theoretical value of C).

[0064] [Mathematical formula 3]

[0065]

[0066] In addition, in this embodiment, if Figure 3 As shown in FIG. 1 , the control frequency fcont in the controller 9 is aligned in phase with the switching frequency fsw and is set to a value obtained by dividing the switching frequency fsw by an integer P (P is an integer greater than or equal to 2). As a result, the control frequency fcont can be set to 1 / P relative to the switching frequency fsw. Therefore, in the case where the maximum value of the switching frequency fsw required is high speed, in the case where complex control processing is required, in the case where a plurality of power conversion devices are controlled by one controller (microcomputer), etc., the processing load of the controller (microcomputer) can be reduced.

[0067] In addition, Figure 3 In the example shown in F, the case where the integer P is made constant is shown, but it is not limited to this. For example, the integer P may be changed for each interval divided into M or for each AC cycle. In this case, the integer P may be 2 or more in at least a part of the interval, and when it is set to 1 in the intervals other than the interval, the effect of reducing the load processing of the controller (microcomputer) can still be obtained. In addition, in the following embodiments 2 to 5, the integer P is not limited to being constant, and may be 2 or more in at least a part of the interval.

[0068] like Figure 3 As shown in FIG. 1 , by setting the control frequency fcont in the controller 9 to a value obtained by dividing the switching frequency fsw by an integer P, the switching frequency fsw and the control frequency fcont can be always synchronized. Thus, for example, when a predetermined input current command (target sinusoidal current) Iin* of a sinusoidal shape synchronized with the detection value of the AC input voltage Vin obtained from the first voltage detector 71 and the current difference between the detection value of the AC input current Iin are used as a feedback amount for feedback calculation, control is performed using a value that is always detected at the same timing relative to the current fluctuation of the AC input current Iin, so even when the switching frequency fsw changes sequentially according to the operating conditions, it is possible to prevent the controllability from being reduced.

[0069] exist Figure 3In the example shown, the output voltage Vout is a constant value, so the duty ratio duty can be calculated using the detected value of the input voltage Vin. Conversely, when the input voltage Vin is a known constant value, the duty ratio duty can be calculated using the detected value of the output voltage Vout. When both the input voltage Vin and the output voltage Vout change dynamically, the duty ratio duty can be calculated using the detected values ​​of both the input voltage Vin and the output voltage Vout.

[0070] [About the action mode]

[0071] The operation mode of the AC / DC converter 10 is divided into a constant power control mode (hereinafter referred to as CP control mode) and a constant current control mode (hereinafter referred to as CC control mode) according to a control method.

[0072] Specifically, in the CP control mode, the controller 9 calculates the current difference between the predetermined sinusoidal input current command (target sinusoidal current) Iin* and the detected value of the AC input current Iin, which is synchronized with the detected value of the AC input voltage Vin obtained from the first voltage detector 71. The calculated current difference is used as a feedback amount through proportional control or proportional integral control operation, and the duty ratio duty_fb related to the power factor control is output.

[0073] On the other hand, in the CC control mode, the controller 9 calculates the voltage difference between the predetermined output voltage command (target DC voltage) Vout* and the detected value of the DC output voltage Vout. The calculated voltage difference is used as feedback through proportional control or proportional integral control operation to output the duty ratio duty_fb related to voltage control.

[0074] [Explanation on how to set the control gain (control constant)]

[0075] Regarding the proportional control or proportional-integral control in the above-mentioned CP control mode and CC control mode, its control gain (control constant) is set based on either the control frequency fcont calculated by the above-mentioned method or the detection value of the input current Iin obtained from the first current detector 73.

[0076] Specifically, the control gain (control constant) is set so that the responsiveness of the power converter becomes higher as the control frequency fcont increases, and the control gain (control constant) is set so that the responsiveness of the power converter becomes lower as the control frequency fcont decreases.

[0077] In addition, as the detection value of the input current Iin obtained from the first current detector 73 becomes larger, the inductance L of the power factor improvement inductor 3 becomes smaller, so the control gain (control constant) is set in a manner that reduces the responsiveness of the power conversion device. As the detection value of the input current Iin obtained from the first current detector 73 becomes smaller, the inductance L of the power factor improvement inductor 3 becomes larger, so the control gain (control constant) is set in a manner that increases the responsiveness of the power conversion device.

[0078] This makes it possible to realize optimal feedback calculation for the operating conditions of the power conversion device.

[0079] [Effects of Embodiment 1]

[0080] As described above, according to this embodiment,

[0081] A power converter is an AC / DC converter that converts AC voltage into DC voltage.

[0082] The AC / DC converter includes a reactor as the magnetic part,

[0083] In the controller, the switching frequency is determined based on a frequency derived in such a way that the magnetic flux density of the magnetic core of the reactor, which is a magnetic parameter of the magnetic component, becomes a set value, and the switching frequency is changed in stages for each of M intervals according to a half cycle of the input AC voltage phase as the time width, where M is an integer greater than 2, so that although the iron loss of the reactor is fixed, the switching loss of the switching element, which accounts for most of the loss of the power conversion device, can be reduced. In addition, stable change of the switching frequency can be achieved.

[0084] In addition, the controller uses the command value Bref of the magnetic flux density of the magnetic core of the inductor, the number of turns N of the inductor, the effective cross-sectional area Ae of the magnetic core of the inductor, the input voltage detection value Vin of the power converter, and the output voltage detection value Vout of the power converter to determine the switching frequency in a manner that satisfies the formula (3). Therefore, although the iron loss of the inductor is fixed, the switching loss of the switching element, which accounts for most of the loss of the power conversion device, can be reduced.

[0085] In addition, the controller calculates the duty ratio of the switching element by performing feedback control so that the input current of the power converter follows a sinusoidal current synchronized with the input voltage of the power converter, thereby being able to supply power from the AC power supply to the DC load while performing power factor control.

[0086] Furthermore, the controller performs feedback control so that the output voltage of the power converter follows the target output voltage and calculates the duty ratio of the switching element. Therefore, power can be supplied from the AC power supply to the DC load while performing voltage control.

[0087] Furthermore, since the controller sets the control constant of the feedback control based on either the control frequency or the input current of the power converter, it is possible to perform optimal feedback calculation according to the operating conditions of the power converter.

[0088] Implementation method 2.

[0089] In the first embodiment, the control method of the switching frequency and the control frequency is described with respect to the magnetic flux density B of the magnetic core of the reactor 3. In the second embodiment, the control method of the switching frequency and the control frequency is described with respect to the current fluctuation (pulsation) of the reactor 3.

[0090] In addition, the circuit structure of the power conversion device is similar to that of the first embodiment. Figure 1 as well as Figure 2 The circuit structure is the same, so its description is omitted.

[0091] [Description of the operation based on the current fluctuation constant control]

[0092] Figure 4 It is an operation waveform diagram for explaining the switching frequency and the control frequency in the AC / DC converter 10 and the controller 9 in the present embodiment, and shows the operation in one cycle of the AC power source 1 .

[0093] exist Figure 4 In A, the instantaneous value of the input voltage Vin from the AC power supply 1 (the output value of the first voltage detector 71) is full-wave rectified via the input-side diode rectifier bridge circuit 2 to become the input voltage |Vin|. In addition, the output voltage Vout (the output value of the second voltage detector 72) of the AC / DC converter 10 is as follows: Figure 4 A shows a constant DC voltage Vout. Figure 4 In A, Vin_rms represents the effective value of the input voltage Vin.

[0094] exist Figure 4 In B, the duty cycle duty of the switching element 5 changes so as to become 1 at the phase where the input voltage Vin becomes zero and to become minimum at the phase where the input voltage Vin becomes a peak value. This operation can be expressed using the above formula (1). The duty cycle duty_vt obtained by the formula (1) and the duty cycle duty_fb obtained by the feedback operation are used to determine the duty cycle duty of the switching element 5. In addition, the control of the duty cycle duty of the switching element 5 is the same as that of the first embodiment.

[0095] Here, the instantaneous input current Iin obtained from the first current detector 73 is superimposed with a current fluctuation ΔIrip due to the excitation and demagnetization (resetting) of the power factor improving inductor 3. The current fluctuation ΔIrip can be expressed by the following formula (4). In addition, L in the formula (4) is the inductance of the power factor improving inductor 3.

[0096] [Number sequence 4]

[0097]

[0098] According to formula (4), when the switching frequency fsw of the switching element 5 is fixed at a preset value, such as the switching frequency fsw_max, the current fluctuation changes according to the phase of the input voltage Vin. In the case where the output voltage Vout is constant and the input current fluctuation ΔIrip decreases as the input voltage Vin increases, even if the input current fluctuation becomes the minimum value ΔIrip_min, since the switching element 5 operates at the fixed switching frequency fsw_max, the ratio of the switching loss to the overall loss increases under light load conditions, resulting in a decrease in the power conversion efficiency.

[0099] In contrast, in the present embodiment, the current fluctuation ΔIrip of the instantaneous input current Iin obtained from the first current detector 73 is derived by feedback calculation according to equation (4) to be a set value ( ΔIrip_max) or less than the maximum value ΔIrip_max of the current fluctuation when the switching element 5 is operated with the maximum value (fsw_max) of the switching frequency being fixed. Figure 4 The switching frequency of D (ΔIrip theoretical value) Figure 4 fsw theoretical value of C).

[0100] That is, in addition to the feedback control of the duty cycle duty, the current ripple ΔIrip of the input current Iin determined by equation (4) is derived by feedback calculation to become the set value ( Figure 4 The switching frequency fsw (theoretical value of ΔIrip of D) Figure 4 fsw theoretical value of C).

[0101] exist Figure 4 In the fsw theoretical value of C, the switching frequency fsw of the switching element 5 changes instantaneously and dynamically in the half cycle of the phase of the input voltage Vin.

[0102] Therefore, in this embodiment, in order to achieve stable variation of the switching frequency of the switching element 5, the switching frequency, which is a set value based on the current fluctuation ΔIrip of the input current Iin derived above, is controlled in a manner that varies in stages for each of M intervals (M is an integer greater than 2) according to the half cycle of the phase of the input voltage Vin.

[0103] Specifically, if Figure 3 As shown in E, the half cycle of the phase of the input voltage Vin is divided into M intervals, and the switching frequency fsw in each interval is calculated so that the current fluctuation ΔIrip of the input current Iin becomes a set value at the starting point of each interval in time.

[0104] [Description of Feedforward Control in Embodiment 2]

[0105] Furthermore, the switching frequency fsw of the switching element 5 may be controlled by deriving the current ripple ΔIrip of the input current Iin to be a set value by adding a feedforward operation in addition to the feedback operation based on the equation (4) described below using the equation (5) to control the switching frequency fsw.

[0106] Specifically, the input voltage Vin obtained from the first voltage detector 71, the output voltage Vout obtained from the second voltage detector 72, the inductance L of the power factor improving reactor 3, and the preset input current fluctuation command value ΔIrip_ref are substituted into the formula (5), and the obtained feedforward operation term is added to the feedback control operation term of the above-mentioned feedback control, and the switching frequency fsw at which the current fluctuation ΔIrip of the input current Iin becomes the set value is derived. And the switching frequency fsw is controlled in a manner that changes in stages for each of the M intervals according to the half cycle of the phase of the input voltage Vin. In addition, for the output voltage Vout, not only the detection value obtained from the second voltage detector 72 but also the control command value can be used when setting the control command value.

[0107] Alternatively, the switching frequency ( Figure 4 fsw theoretical value of C).

[0108] [Formula 5]

[0109]

[0110] In addition, the operation mode and the setting method of the control gain (control constant) of the AC / DC converter 10 are the same as those in the first embodiment, and thus the description thereof will be omitted.

[0111] Furthermore, in the present embodiment, an example in which the current fluctuation of the input current of the power converter is used as the electrical parameter of the power converter is described, but the current fluctuation of the output current of the power converter may also be used.

[0112] [Effects of Embodiment 2]

[0113] As described above, according to this embodiment,

[0114] The power converter is an AC / DC converter that converts AC voltage into DC voltage.

[0115] The AC / DC converter includes a reactor as the magnetic part,

[0116] In the controller, the switching frequency is determined based on a frequency derived in such a way that the current fluctuation of the input current of the power converter, which is an electrical parameter of the power converter, becomes a set value, and the switching frequency is changed in stages for each of M intervals according to a half cycle of the input AC voltage phase as the time width, where M is an integer greater than or equal to 2, so that the switching loss of the switching element, which accounts for most of the loss of the power conversion device, can be reduced. In addition, stable change of the switching frequency can be achieved.

[0117] In addition, the switching frequency is determined in a manner that satisfies the formula (5) using the command value ΔIrip_ref of the current fluctuation of the input current, the inductance L of the reactor, the input voltage detection value Vin of the power converter, and the output voltage detection value Vout of the power converter. This can reduce the switching loss of the switching element, which accounts for most of the loss of the power conversion device.

[0118] In addition, the controller calculates the duty ratio of the switching element by performing feedback control so that the input current of the power converter follows a sinusoidal current synchronized with the input voltage of the power converter, thereby being able to supply power from the AC power supply to the DC load while performing power factor control.

[0119] Furthermore, the controller performs feedback control so that the output voltage of the power converter follows the target output voltage and calculates the duty ratio of the switching element. Therefore, power can be supplied from the AC power supply to the DC load while performing voltage control.

[0120] Furthermore, since the controller sets the control constant of the feedback control based on either the control frequency or the input current of the power converter, it is possible to perform optimal feedback calculation according to the operating conditions of the power converter.

[0121] Implementation method 3.

[0122] [Description of Circuit Configuration of Embodiment 3]

[0123] Figure 5 This is an example of a circuit configuration diagram of a power conversion device according to the third embodiment, in which an isolated DC / DC converter 11 is provided between the output terminal of the AC / DC converter 10 and the DC load 8 described in the first embodiment.

[0124] The structure of the AC / DC converter 10 is the same as that of the first embodiment ( Figure 1 ) has the same structure as that of the input side diode rectifier bridge circuit 2, the power factor improving inductor 3, the diode element 4, and the switching element 5, which are described in detail in the first embodiment.

[0125] The isolated DC / DC converter 11 includes a primary-side inverter circuit composed of switching elements 1111, 1112, 1113, and 1114, an isolation transformer 112, a secondary-side rectifier circuit composed of diode elements 1131, 1132, 1133, and 1134, a smoothing inductor 114, a smoothing capacitor 115, a load voltage detector 1161 for detecting a load voltage Vload, and a load current detector 1162 for detecting a load current Iload.

[0126] The switching elements 1111 to 1114 constituting the primary side inverter of the isolated DC / DC converter 11 are not limited to IGBTs and MOSFETs, but SiC-MOSFETs, GaN-FETs, GaN-HEMTs or Ga2O3-MOSFETs may also be used. Figure 5 The rectifier bridge circuit is composed of diodes, and a switching element such as MOSFET can be used instead of the diode to set it as a synchronous rectifier circuit.

[0127] like Figure 5 As shown, when an isolated DC / DC converter 11 is connected to the front stage of the DC load 8, a second voltage detector 72, a load voltage detector 1161, a second current detector 74 and a load current detector 1162 are used, and based on part or all of their detection values, the controller 90 performs control operations for each control cycle determined by the control frequency.

[0128] The controller 90 controls the switching elements 1111 to 1114. That is, the controller 90 sends drive signals Y1 to Y4 to the gates of the switching elements 1111 to 1114 based on part or all of the detection values ​​obtained from the second voltage detector 72, the load voltage detector 1161, the second current detector 74, and the load current detector 1162, and controls the on and off of the switching elements 1111 to 1114, so that the desired operation can be performed.

[0129] In addition, the controller 90 performs appropriate feedback calculation according to the operation mode of the power conversion device as described later, outputs the duty ratio duty_fb, and calculates the duty ratio duty of the switching elements 1111 to 1114 .

[0130] In addition, in the present embodiment, the isolated DC / DC converter 11 is controlled as a power converter, so the voltage Vout detected by the second voltage detector 72 becomes the input voltage Vout of the power converter, the current Iout detected by the second current detector 74 becomes the input current Iout of the power converter, the voltage Vload detected by the load voltage detector 1161 becomes the output voltage Vload of the power converter, and the current Iload detected by the load current detector 1162 becomes the output current Iload of the power converter.

[0131] [Description of the operation based on constant magnetic flux density control]

[0132] In the third embodiment, a case is described in which the switching frequency of the switching elements 1111 to 1114 and the control frequency in the controller 90 are controlled with the magnetic flux density B of the magnetic core of the insulating transformer 112 constituting the isolated DC / DC converter 11 as an object. In addition, in the third embodiment, the fluctuation amount of the output voltage Vout of the AC / DC converter 10 (the input voltage Vout of the DC / DC converter 11) and the load voltage Vload of the DC / DC converter 11 (the output voltage Vload of the DC / DC converter 11) is treated as zero, that is, a constant value.

[0133] Figure 6 This is an operation waveform diagram for explaining the switching frequency and the control frequency in the isolated DC / DC converter 11 and the controller 90 according to the present embodiment, and shows the operation waveform with respect to the load voltage (output voltage) Vload.

[0134] exist Figure 6 In A, the detection value Vout of the second voltage detector 72, that is, the input voltage Vout of the isolated DC / DC converter 11, and the detection value Vload of the load voltage detector 1161, that is, the output voltage Vload of the isolated DC / DC converter 11, become constant DC voltages.

[0135] At this time, if Figure 6The duty cycle duty of the drive signals Y1 to Y4 for determining the switching elements 1111 to 1114 shown in B becomes the minimum value when the load voltage (output voltage) Vload becomes the minimum, and becomes the maximum value when the load voltage (output voltage) Vload becomes the maximum. This action can be expressed by the following formula (6). The duty cycle duty_vt obtained by formula (6) and the duty cycle duty_fb obtained by feedback operation are used to determine the duty cycle duty of the switching elements 1111 to 1114. Specifically, the duty cycle duty_fb is used as a feedback term, and the duty cycle duty_vt is used as a feedforward term, so that only the feedback term or the sum of the feedback term and the feedforward term becomes the duty cycle duty of the switching element 5.

[0136] [Mathematical formula 6]

[0137]

[0138] The magnetic flux density B of the magnetic core of the isolation transformer 112 is expressed by the following equation (7): In equation (7), N is the number of turns of the isolation transformer 112, Ae is the effective cross-sectional area of ​​the magnetic core of the isolation transformer 112, and fsw is the switching frequency of the switching elements 1111 to 1114.

[0139] [Formula 7]

[0140]

[0141] In a case where the input voltage Vout of the isolated DC / DC converter 11 is constant and the switching frequency fsw is fixed at a preset maximum value fsw_max, and the magnetic flux density of the magnetic core of the isolation transformer 112 decreases as the output voltage Vload of the isolation DC / DC converter 11 decreases, even if the magnetic flux density B of the magnetic core of the isolation transformer 112 becomes a minimum value, since the switching elements 1111 to 1114 operate at a fixed switching frequency fsw_max, under light load conditions, the proportion of switching loss to the overall loss increases, resulting in a decrease in power conversion efficiency.

[0142] Therefore, in this embodiment, if Figure 6 C and Figure 6 D, so that the magnetic flux density B of the magnetic core of the isolation transformer 112 becomes a set value below the maximum value Bmax (in this example, the maximum value Bmax of the magnetic flux density; Figure 6 The switching frequencies ( ) of the switching elements 1111, 1112, 1113, and 1114 are derived by feedback calculation according to equation (7). Figure 6That is, in addition to the feedback control of the duty cycle duty, the switching frequency fsw is derived by feedback calculation at a setting value at which the magnetic flux density B of the magnetic core of the isolation transformer 112 determined by equation (7) becomes less than or equal to the maximum value Bmax.

[0143] Furthermore, in this embodiment, in order to realize stable variation of the switching frequency of the switching elements 1111 to 1114, the switching frequency ( Figure 6 The switching frequency fsw of the output voltage (load voltage) Vload is calculated to be a set value that makes the magnetic flux density B of the magnetic core of the insulation transformer 112 less than the maximum value Bmax at any load voltage Vload in each interval.

[0144] In addition, the switching frequency ( Figure 6 C fsw theoretical value), but a feedforward operation may be used in addition to the feedback operation. That is, a feedforward operation using the following formula (8) may be added to derive the switching frequency fsw of the switching elements 1111 to 1114 at which the magnetic flux density of the isolation transformer 112 becomes a set value, and control the switching frequency fsw.

[0145] Specifically, the input voltage Vout obtained from the second voltage detector 72, the output voltage (load voltage) Vload obtained from the load voltage detector 1161, the number of turns N of the insulation transformer 112, the effective cross-sectional area Ae of the magnetic core, and the command value Bref of the magnetic flux density of the magnetic core set in advance are substituted into the formula (8), and the obtained feedforward operation term is added to the feedback control operation term of the above-mentioned feedback control, and the switching frequency fsw is derived to be a set value at which the magnetic flux density B of the magnetic core of the insulation transformer 112 becomes less than the maximum value Bmax. Then, the switching frequency fsw is controlled so as to change stepwise for each of M (M is an integer greater than or equal to 2) intervals according to the operating range R1 of the output voltage (load voltage) Vload. In addition, for the output voltage (load voltage) Vload, not only the detection value obtained from the load voltage detector 1161 but also the control command value may be used when setting the control command value.

[0146] Alternatively, the switching frequency may be derived using only the feedforward operation instead of the feedback operation. Figure 6 fsw theoretical value of C).

[0147] [Mathematical formula 8]

[0148]

[0149] In addition, in this embodiment, regarding the control frequency fcont in the controller 90, as shown in FIG. Figure 6 As shown in FIG. 1 , the phase is aligned with the switching frequency fsw, and is set to a value obtained by dividing the switching frequency fsw by an integer P (P is an integer greater than 2). As a result, the control frequency fcont can be made 1 / P relative to the switching frequency fsw. Therefore, in the case where the maximum value of the required switching frequency is high speed, in the case where complex control processing is required, in the case where a plurality of power conversion devices are controlled by one controller (microcomputer), the processing load of the controller (microcomputer) can be reduced.

[0150] Furthermore, by setting the control frequency fcont in the controller 90 to Figure 6 The value obtained by dividing the switching frequency by an integer P greater than 2 as shown in F can always synchronize the switching frequency with the control frequency. As a result, for example, when the current difference between the load current command Iload* and the detected value of the load current Iload is used as the feedback amount for feedback calculation, the control is performed using the value detected at the same timing relative to the current fluctuation of the load current Iload, so even when the switching frequency changes sequentially according to the operating conditions, it is possible to prevent the controllability from being reduced.

[0151] exist Figure 6 In the example, the output voltage (load voltage) Vload is a constant value, so the duty ratio duty can be calculated using the detection value of the input voltage Vout of the isolated DC / DC converter 11 (the output voltage Vout of the AC / DC converter 10). On the contrary, when the input voltage Vout of the isolated DC / DC converter 11 (the output voltage Vout of the AC / DC converter 10) is a known constant value, the duty ratio duty can be calculated using the detection value of the output voltage (load voltage) Vload. When both the input voltage Vout and the output voltage (load voltage) Vload of the isolated DC / DC converter 11 change dynamically, the duty ratio duty can be calculated using the detection values ​​of both.

[0152] [About the action mode]

[0153] The operation mode of the isolated DC / DC converter 11 is divided into a constant power control mode (hereinafter referred to as CP control mode) and a constant current control mode (hereinafter referred to as CC control mode) according to a control method.

[0154] Specifically, in the CP control mode, the controller 90 calculates the voltage difference between the predetermined output voltage command Vout* of the AC / DC converter 10, that is, the input voltage command Vout* of the isolated DC / DC converter 11, and the detected value of the output voltage Vout of the AC / DC converter 10, that is, the detected value of the input voltage Vout of the isolated DC / DC converter 11. The calculated voltage difference is used as a feedback amount through proportional control or proportional-integral control operation, and the duty ratio duty_fb related to the voltage control is output.

[0155] In the CC control mode, the controller 90 calculates the current difference between the predetermined load current command (output current command) Iload* and the detected value of the load current (output current) Iload. The calculated current difference is used as feedback through proportional control or proportional integral control operation, and the duty cycle duty_fb related to the current control is output.

[0156] [Explanation on how to set the control gain (control constant)]

[0157] Regarding the proportional control or proportional-integral control in the above-mentioned CP control mode and CC control mode, its control gain (control constant) is set based on either the control frequency fcont calculated by the above-mentioned method or the detection value of the load current (output current) Iload obtained from the load current detector 1162.

[0158] Specifically, the control gain (control constant) is set so that the responsiveness of the power conversion device increases as the control frequency fcont increases, and the control gain (control constant) is set so that the responsiveness of the power conversion device decreases as the control frequency fcont decreases. In addition, as the detection value of the load current (output current) Iload obtained from the load current detector 1162 increases, the inductance L of the insulation transformer 112 decreases, so the control gain (control constant) is set so that the responsiveness of the power conversion device decreases, and as the detection value of the load current (output current) Iload obtained from the load current detector 1162 decreases, the inductance L of the insulation transformer 112 increases, so the control gain (control constant) is set so that the responsiveness of the power conversion device increases.

[0159] This makes it possible to realize optimal feedback calculation for the operating conditions of the power conversion device.

[0160] In addition, in the above, the DC / DC converter includes a transformer as a magnetic component, and the switching frequency is determined based on the frequency derived in a manner such that the magnetic flux density of the magnetic core of the transformer, which is a magnetic parameter of the magnetic component, becomes a set value, but the DC / DC converter may also include an inductor as a magnetic component, and the switching frequency may be determined based on the frequency derived in a manner such that the magnetic flux density of the inductor, which is a magnetic parameter of the magnetic component, becomes a set value.

[0161] [Effects of Embodiment 3]

[0162] As described above, according to this embodiment,

[0163] The power converter is a DC / DC converter that converts a DC voltage into a DC voltage.

[0164] The DC / DC converter includes at least one of a reactor and a transformer as the magnetic component.

[0165] In the controller, the switching frequency is determined based on a frequency derived in such a way that the magnetic flux density of the magnetic core of the inductor or transformer, which is the magnetic parameter of the magnetic part, becomes a set value, and the switching frequency changes in stages for each of M intervals according to the operating range of the output voltage of the power converter, which is the electrical quantity amplitude, wherein M is an integer greater than 2. Therefore, although the iron loss of the inductor or transformer is fixed, the switching loss of the switching element, which accounts for most of the loss of the power conversion device, can be reduced.

[0166] In addition, the controller uses the command value Bref of the magnetic flux density of the magnetic core of the inductor or the transformer, the number of turns N of the inductor or the transformer, the effective cross-sectional area Ae of the magnetic core of the inductor or the transformer, the input voltage detection value Vout of the power converter, and the output voltage detection value Vload of the power converter to determine the switching frequency in a manner that satisfies the formula (8). Therefore, although the iron loss of the inductor or the transformer is fixed, the switching loss of the switching element, which accounts for most of the loss of the power conversion device, can be reduced.

[0167] Furthermore, since the controller performs feedback control to calculate the duty ratio of the switching element so that the input voltage of the power converter follows the target input voltage, it is possible to perform voltage control while converting DC power into DC power.

[0168] Furthermore, since the controller performs feedback control to calculate the duty ratio of the switching element so that the output current of the power converter follows the target output current, it is possible to perform conversion from DC power to DC power while performing current control.

[0169] Furthermore, since the controller sets the control constant of the feedback control based on either the control frequency or the output current of the power converter, it is possible to perform optimal feedback calculation according to the operating conditions of the power converter.

[0170] Implementation method 4.

[0171] In the third embodiment, a method of controlling the switching frequency and the control frequency is described with reference to the magnetic flux density B of the magnetic core of the insulating transformer constituting the insulating DC / DC converter 11. In the fourth embodiment, a method of controlling the switching frequency and the control frequency is described with reference to the fluctuation (pulsation) of the output current of the insulating DC / DC converter 11.

[0172] In addition, the circuit structure of the power conversion device is similar to that of the third embodiment. Figure 5 The circuit structure is the same, so its description is omitted.

[0173] Figure 7 This is an operation waveform diagram for explaining the switching frequency and the control frequency in the power conversion device according to the present embodiment, and shows the operation waveform with respect to the load voltage (output voltage) Vload.

[0174] exist Figure 7 In A, the detection value Vout of the second voltage detector 72, that is, the input voltage Vout of the isolated DC / DC converter 11, and the detection value Vload of the load voltage detector 1161, that is, the output voltage Vload of the isolated DC / DC converter 11, become constant DC voltages.

[0175] At this time, if Figure 7 The duty ratio duty of the drive signals Y1 to Y4 for determining the switch elements 1111 to 1114 shown in B becomes the minimum value when the load voltage (output voltage) Vload becomes the minimum value, and becomes the maximum value when the load voltage (output voltage) Vload becomes the maximum value. This action can be expressed by the above formula (6). The duty ratio duty_vt obtained by the formula (6) and the duty ratio duty_fb obtained by the feedback operation are used to determine the duty ratio duty of the switch elements 1111 to 1114. In addition, the control of the duty ratio duty of the operation switch elements 1111 to 1114 is the same as that in the third embodiment.

[0176] In addition, the load current (output current) Iload obtained from the load current detector 1162 is superimposed with a current fluctuation ΔIrip due to the excitation and reset (demagnetization) of the isolation transformer 112. The current fluctuation ΔIrip can be expressed by the following equation (9). Here, in equation (9), L is the inductance of the isolation transformer 112.

[0177] [Mathematical formula 9]

[0178]

[0179] According to formula (9), when the switching frequency fsw of the switching elements 1111 to 1114 is fixed at a preset value, the current fluctuation changes according to the load voltage (output voltage) Vload. For example, when the output voltage Vout from the AC / DC converter 10, that is, the input voltage Vout of the isolated DC / DC converter 11 is constant, as the load voltage (output voltage) Vload decreases, the load current (output current) fluctuation ΔIrip decreases, even if the load current (output current) fluctuation becomes the minimum value ΔIrip_min, since the switching elements 1111 to 1114 operate at a fixed switching frequency, the ratio of the switching loss to the overall loss increases under light load conditions, resulting in a decrease in the power conversion efficiency.

[0180] In contrast, in the present embodiment, the current fluctuation ΔIrip of the instantaneous load current Iload obtained from the load current detector 1162 is derived by feedback calculation according to equation (9) so as to be a set value ( ΔIrip_max) or less than the maximum value ΔIrip_max of the current fluctuation when the switching elements 1111 to 1114 are operated with the maximum value (fsw_max) of the switching frequency being fixed. Figure 7 The switching frequency of D (ΔIrip theoretical value) Figure 7 fsw theoretical value of C).

[0181] That is, in addition to the feedback control of the duty cycle duty, the current fluctuation ΔIrip of the load current Iload determined by equation (9) is derived by feedback calculation to become the set value ( Figure 7 The switching frequency fsw (theoretical value of ΔIrip of D) Figure 7 fsw theoretical value of C).

[0182] Furthermore, in the present embodiment, in order to achieve stable variation of the switching frequency of the switching elements 1111 to 1114, the switching frequency, which is a set value according to the current fluctuation ΔIrip of the load current (output current) Iload derived above, is controlled in a manner that varies in stages for each of M intervals (M is an integer greater than 2) according to the operating range R1 of the load voltage (output voltage) Vload.

[0183] Specifically, if Figure 7As shown in E, the operating range R1 of the load voltage (output voltage) Vload is divided into M intervals, and the switching frequency fsw in each interval is calculated in such a way that the current fluctuation ΔIrip of the load current (output current) Iload becomes a set value under any load voltage (output voltage) Vload in each interval.

[0184] In addition, it is also possible to use not only the feedback operation based on equation (9) but also the following equation (10) plus a feedforward operation to derive the switching frequency fsw of the switching elements 1111 to 1114 so that the current fluctuation ΔIrip of the load current (output current) Iload becomes a set value, thereby controlling the switching frequency fsw.

[0185] Specifically, the input voltage Vout of the isolated DC / DC converter 11 obtained from the second voltage detector 72, the load voltage (output voltage) Vload obtained from the load voltage detector 1161, the inductance L of the isolation transformer 112, and the pre-set load current (output current) fluctuation command value ΔIrip_ref are substituted into equation (10), and the obtained feedforward operation term is added to the feedback control operation term of the feedback control based on equation (9), and the current fluctuation ΔIrip of the load current (output current) Iload is derived to become the switching frequency fsw of the set value. And, the switching frequency fsw is controlled in a manner that changes stepwise for each of the integer m intervals greater than 2 according to the operating range R1 of the load voltage (output voltage) Vload. In addition, with respect to the load voltage (output voltage) Vload, not only the detection value obtained from the load voltage detector 1161, but also the control command value can be used when setting the control command value.

[0186] Alternatively, the switching frequency ( Figure 7 fsw theoretical value of C).

[0187] [Formula 10]

[0188]

[0189] In addition, the operation mode and the setting method of the control gain (control constant) of the isolated DC / DC converter 11 are the same as those in the third embodiment, and thus the description thereof will be omitted.

[0190] In addition, in the above, the DC / DC converter includes a transformer as a magnetic component, and the switching frequency is determined based on a frequency derived in a manner such that the current fluctuation of the output current of the power converter, which is an electrical parameter of the power converter, becomes a set value, but the DC / DC converter may also include an inductor as a magnetic component, and the switching frequency is determined based on a frequency derived in a manner such that the current fluctuation of the output current of the power converter, which is an electrical parameter of the power converter, becomes a set value.

[0191] Furthermore, in the present embodiment, an example in which the current fluctuation of the output current of the power converter is used as the electrical parameter of the power converter is described, but the current fluctuation of the input current of the power converter may also be used.

[0192] [Effects of Embodiment 4]

[0193] As described above, according to this embodiment,

[0194] The power converter is a DC / DC converter that converts a DC voltage into a DC voltage.

[0195] The DC / DC converter includes at least one of a reactor and a transformer as the magnetic component.

[0196] In the controller, the switching frequency is determined based on a frequency derived in such a way that the current fluctuation of the output current of the power converter, which is an electrical parameter of the power converter, becomes a set value, and the switching frequency is changed in stages for each of M intervals according to the operating range of the output voltage of the power converter, which is the electrical quantity amplitude, wherein M is an integer greater than 2, so that the switching loss of the switching element, which accounts for most of the loss of the power conversion device, can be reduced.

[0197] In addition, the controller uses the command value ΔIrip_ref of the current fluctuation of the output current of the power converter, the inductance L of the reactor or the transformer, the input voltage detection value Vout of the power converter, and the output voltage detection value Vload of the power converter to determine the switching frequency in a manner that satisfies the formula (10), thereby reducing the switching loss of the switching element that accounts for most of the loss of the power conversion device.

[0198] Furthermore, since the controller performs feedback control to calculate the duty ratio of the switching element so that the input voltage of the power converter follows the target input voltage, it is possible to perform voltage control while converting DC power into DC power.

[0199] Furthermore, since the controller performs feedback control to calculate the duty ratio of the switching element so that the output current of the power converter follows the target output current, it is possible to perform conversion from DC power to DC power while performing current control.

[0200] Furthermore, since the controller sets the control constant of the feedback control based on either the control frequency or the output current of the power converter, it is possible to perform optimal feedback calculation according to the operating conditions of the power converter.

[0201] Implementation method 5.

[0202] In the above-mentioned embodiments 3 and 4, the structure in which the output terminal of the AC / DC converter 10 and the DC load 8 are connected via the insulating DC / DC converter 11 described in the first embodiment is described as an example. However, the embodiment of the present application is not limited to this. That is, a DC voltage may be provided before the insulating DC / DC converter 11, and the structure may be a single insulating DC / DC converter. In addition, a chopper circuit using a reactor instead of an insulating transformer may be used.

[0203] In the case of the structure as described above, in addition to the action mode described in the embodiment, there is also the following mode: calculating the voltage difference between the predetermined load voltage (output voltage) command Vload* and the detection value of the load voltage (output voltage) Vload, using the calculated voltage difference as feedback through proportional control or proportional-integral control operation, and outputting the duty cycle duty_fb related to the voltage control.

[0204] In addition, the calculation method of the switching frequency fsw and the control frequency fcont and the setting method of the control gain (control constant) are the same as those in the first to fourth embodiments, and thus the description thereof will be omitted.

[0205] According to this embodiment, in a structure in which power conversion is performed from a DC power supply via a DC / DC converter, the controller performs feedback control in such a way that the output voltage of the power converter follows the target output voltage and calculates the duty cycle of the switching element, so that DC power can be converted into DC power while performing voltage control.

[0206] Furthermore, since the controller sets the control constant of the feedback control based on either the control frequency or the output current of the power converter, it is possible to perform optimal feedback calculation according to the operating conditions of the power converter.

[0207] This application describes various exemplary embodiments and examples, but various features, modes, and functions described in one or more embodiments are not limited to application in specific embodiments and can be applied to the embodiments alone or in various combinations.

[0208] Therefore, numerous modifications not shown are contemplated within the scope of the technology disclosed in this application, including, for example, modifying, adding, or omitting at least one component, or extracting at least one component and combining it with components of other embodiments.

Claims

1. A power conversion device, comprising: Power converters, including magnetic components and switching elements, perform power conversion; and A controller controls the on / off state of the switching element according to the duty cycle of the switching element and the switching frequency of driving the switching element under a control period determined by the control frequency, In the controller, the switching frequency is determined based on at least one of the magnetic parameters of the magnetic part and the electrical parameters of the power converter, and the switching frequency is changed in stages for each of M intervals based on any one of a half cycle of the input AC voltage phase as a predetermined time width and an operating range of the output voltage of the power converter as a predetermined electrical quantity amplitude, wherein M is an integer greater than 2, and The control frequency is a value obtained by dividing the switching frequency by an integer P that is greater than or equal to 2.

2. The power conversion device according to claim 1, wherein: The power converter is an AC / DC converter that converts AC voltage into DC voltage. The AC / DC converter includes a reactor as the magnetic part, In the controller, the switching frequency is determined based on a frequency derived in such a way that the magnetic flux density of the magnetic core of the inductor, which is a magnetic parameter of the magnetic part, becomes a set value, and the switching frequency changes in stages for each of M intervals according to a half cycle of the input AC voltage phase, which is the time width, where M is an integer greater than 2.

3. The power conversion device according to claim 2, wherein: The controller determines the switching frequency in a manner satisfying equation (A) using a command value Bref of the magnetic flux density of the magnetic core of the reactor, the number of turns N of the reactor, an effective cross-sectional area Ae of the magnetic core of the reactor, an input voltage detection value Vin of the power converter, and an output voltage detection value Vout of the power converter. [Mathematical formula 1] 。 4. The power conversion device according to claim 1, wherein: The power converter is an AC / DC converter that converts AC voltage into DC voltage. The AC / DC converter includes a reactor as the magnetic part, In the controller, the switching frequency is determined based on a frequency derived in such a way that the current fluctuation of the input current of the power converter, which is an electrical parameter of the power converter, becomes a set value, and the switching frequency changes in stages for each of M intervals according to a half cycle of the input AC voltage phase, which is the time width, where M is an integer greater than 2.

5. The power conversion device according to claim 4, wherein: The controller determines the switching frequency so as to satisfy equation (B) by using the command value ΔIrip_ref of the current ripple of the input current, the inductance L of the reactor, the input voltage detection value Vin of the power converter, and the output voltage detection value Vout of the power converter. [Mathematical formula 2] 。 6. The power conversion device according to any one of claims 2 to 5, wherein: The controller calculates the duty ratio of the switching element by performing feedback control so that the input current of the power converter follows a sinusoidal current synchronized with the input voltage of the power converter.

7. The power conversion device according to any one of claims 2 to 5, wherein: The controller calculates the duty ratio of the switching element by performing feedback control so that the output voltage of the power converter follows a target output voltage.

8. The power conversion device according to claim 6, wherein: The controller sets a control constant of the feedback control according to either the control frequency or an input current of the power converter.

9. The power conversion device according to claim 1, wherein: The power converter is a DC / DC converter that converts a DC voltage into a DC voltage. The DC / DC converter includes at least one of a reactor and a transformer as the magnetic component. In the controller, the switching frequency is determined based on a frequency derived in such a way that the magnetic flux density of the inductor or the magnetic core of the transformer, which is a magnetic parameter of the magnetic part, becomes a set value, and the switching frequency changes in stages for each of M intervals according to the operating range of the output voltage of the power converter, which is the electrical quantity amplitude, where M is an integer greater than 2.

10. The power conversion device according to claim 9, wherein: The controller determines the switching frequency in a manner satisfying Formula (C) by using a command value Bref of the magnetic flux density of the reactor or the transformer, the number of turns N of the reactor or the transformer, an effective cross-sectional area Ae of the magnetic core of the reactor or the transformer, an input voltage detection value Vout of the power converter, and an output voltage detection value Vload of the power converter. [Mathematical formula 3] 。 11. The power conversion device according to claim 1, wherein: The power converter is a DC / DC converter that converts a DC voltage into a DC voltage. The DC / DC converter includes at least one of a reactor and a transformer as the magnetic component. In the controller, the switching frequency is determined based on a frequency derived in such a way that the current fluctuation of the output current of the power converter, which is an electrical parameter of the power converter, becomes a set value, and the switching frequency changes in stages for each of M intervals according to the operating range of the output voltage of the power converter, which is the electrical quantity amplitude, where M is an integer greater than 2.

12. The power conversion device according to claim 11, wherein: The controller determines the switching frequency in a manner satisfying equation (D) using a command value ΔIrip_ref of the current ripple of the output current of the power converter, an inductance L of the reactor or the transformer, an input voltage detection value Vout of the power converter, and an output voltage detection value Vload of the power converter. [Formula 4] 。 13. The power conversion device according to any one of claims 9 to 12, wherein: The controller calculates the duty ratio of the switching element by performing feedback control so that the input voltage of the power converter follows a target input voltage.

14. The power conversion device according to any one of claims 9 to 12, wherein: The controller calculates the duty ratio of the switching element by performing feedback control so that the output voltage of the power converter follows a target output voltage.

15. The power conversion device according to any one of claims 9 to 12, wherein: The controller calculates the duty ratio of the switching element by performing feedback control so that the output current of the power converter follows a target output current.

16. The power conversion device according to claim 13, wherein: The controller sets a control constant of the feedback control according to either the control frequency or an output current of the power converter.

17. The power conversion device according to claim 7, wherein: The controller sets a control constant of the feedback control according to either the control frequency or an input current of the power converter.

18. The power conversion device according to claim 14, wherein: The controller sets a control constant of the feedback control according to either the control frequency or an output current of the power converter.

19. The power conversion device according to claim 15, wherein: The controller sets a control constant of the feedback control according to either the control frequency or an output current of the power converter.

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