JP2011250656A - Power conversion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion apparatus capable of acquiring a full-wave voltage waveform having a small waveform distortion as desired at both ends of a capacitor even when capacitance of the capacitor decreases.SOLUTION: A step-up/step-down converter 14 is controlled by reflecting a correction duty k×Δic corresponding to a deviation Δic (Δic=iccom-ic) between capacitor current ic flowing in a capacitor 28 and capacitor current command value iccom respectively for a step-up duty (Vcom/Vin) and a step-down duty (1-Vin/Vcom) based on an output voltage correction command value Vcom (Vcom=Vmcom+ΔVn or Vcom=A×Vmcom) to acquire a full-wave voltage waveform Vm having a small waveform distortion as desired at both ends of the capacitor 28 even when capacitance of the capacitor 28 decreases.

Description

  The present invention relates to a buck-boost converter that receives a DC voltage supplied from a DC power source and outputs it as a full-wave voltage across an output-side capacitor, and the step-up / step-down converter based on an output voltage command value for obtaining the full-wave voltage. A power converter having a converter control unit for controlling a converter, wherein the full-wave voltage obtained by the step-up / step-down converter is converted into a desired AC voltage by a system-linking inverter and linked to a power system. The present invention relates to a power conversion device suitable for application.

  A solar cell, a fuel cell, or the like generates a DC voltage, but an AC voltage is suitable for transmission of electric power and driving of a motor, and a power conversion device that converts the DC voltage into an AC voltage is used. Further, a system-linked inverter is known as a circuit that links DC power supplied from a DC power source such as a solar cell or a fuel cell to the system and converts it into AC power.

  The inventor of this application proposes a power conversion device 200 shown in FIG. The power conversion device 200 converts, for example, a DC voltage 250 Vdc generated by the DC power source 202 into a full-wave voltage Vm of 330 Vpeak, for example, by a chopper type buck-boost converter 204 as a first power conversion device, The full-wave voltage Vm is converted to an AC voltage of 200 Vrms through a chopper type inverter 206 and LPF 208 as a second power converter, and is linked to the power system of the load 220.

  The converter control unit 210 outputs an output voltage command value Vcom obtained by multiplying the output voltage command value obtained by taking the absolute value of the 200 Vrms sine wave command value Vs input to the inverter control unit 218 by a predetermined constant (the waveform is a full-wave voltage waveform). The basic step-down duty and step-up duty are calculated from the DC voltage Vin detected by the voltage sensor 212, and the full-wave voltage Vm appearing on the output-side capacitor 214 is detected by the voltage sensor 216 to perform proportional integration (PI ) Control correction duty is calculated and corrected by adding to the step-down duty and the step-up duty, respectively, and the step-down / step-down converter is compared by comparing the corrected step-down duty and step-up duty with a triangular wave carrier signal (carrier signal). The driving signal 204 is configured to be calculated.

  On the other hand, the inverter control unit 218 generates a reference signal Vref = 1/2 (Vs / Vm + 1) from the sine wave command value Vs of 200 Vrms and the full wave voltage Vm, and the generated reference signal Vref and a triangular wave The drive signal of the inverter 206 is calculated by comparing the carrier signal (carrier signal).

JP 2009-254196 A (FIG. 9)

  According to the power conversion device 200 according to Patent Document 1, the correction duty by proportional integral control of the full-wave voltage Vm appearing at both ends of the capacitor 214 on the output side of the step-up / down converter 204 is taken into consideration, so that the load 220 is lightly weighted. It has been confirmed that a full-wave voltage Vm with a small waveform distortion can be output.

  However, it has been found that when the power converter 200 is used for a long time, the waveform distortion of the full-wave voltage Vm increases.

  The present invention has been made in consideration of such knowledge and problems, and makes it possible to keep the waveform distortion of the full-wave voltage appearing at the output of the buck-boost converter small over a long period of use. An object is to provide a power converter.

  Another object of the present invention is to provide a power conversion device that can keep the waveform distortion of the full-wave voltage that appears in the output of the buck-boost converter small even if the ambient temperature of the power conversion device fluctuates. To do.

  A power converter according to the present invention includes a step-up / down converter that receives a DC voltage supplied from a DC power source and outputs a full-wave voltage across a capacitor on the output side, and an output voltage for defining the full-wave voltage. A command value generating unit that generates a command value and generating a capacitor current command value for defining a current flowing through the capacitor, a capacity decrease amount calculating unit that calculates a capacity decrease amount of the capacitor, and a capacitance of the capacitor A correction value calculation unit for calculating a correction value for correcting the output voltage command value according to the amount of decrease; and the capacitor for the step-down duty and the step-up duty based on the output voltage correction command value corrected by the correction value. The buck-boost converter is controlled by reflecting a correction duty corresponding to a deviation between the capacitor current flowing through the capacitor and the capacitor current command value. A converter control unit which, characterized in that it comprises a.

  According to the inventors of this application, the waveform distortion of the full-wave voltage increases when the usage time is extended for a long time due to a decrease in the capacitance (capacitance) of the capacitor on the output side of the buck-boost converter, so-called capacitance loss. I found it to be a thing.

  Accordingly, a capacitance reduction amount calculation unit for calculating the capacitance reduction amount of the capacitor is provided, and a correction for calculating a correction value of the output voltage command value according to the capacitance reduction amount of the capacitor calculated by the capacitance reduction amount calculation unit. A value calculation unit is provided, and the converter control unit deviates between the capacitor current flowing through the capacitor and the capacitor current command value with respect to the step-down duty and the step-up duty based on the output voltage correction command value corrected by the correction value, respectively. By controlling the step-up / down converter by reflecting the correction duty according to the full-voltage voltage waveform with a small desired waveform distortion at both ends of the capacitor, in other words, A full-wave voltage waveform approximating the effective value conversion necessary for the inverter can be obtained.

  The command value generating unit generates a capacitor current command value for defining the current flowing through the capacitor by differentiating and generating an output voltage command value for defining the full-wave voltage, The capacitor current command value can be easily generated.

  Further, when obtaining the capacitor current flowing through the capacitor, it may be obtained directly from the output of the current sensor connected in series with the capacitor, or the output of the voltage sensor that measures the voltage across the capacitor is differentiated. It may be obtained indirectly based on the output.

  The power conversion device according to the present invention can provide a power conversion device with small waveform distortion of the full-wave voltage that appears in the output of the buck-boost converter even when the capacitance value of the output-side capacitor of the buck-boost converter decreases.

  In addition, the power converter according to the present invention provides a power converter with small waveform distortion of the full-wave voltage that appears in the output of the buck-boost converter even if the capacitance value of the output-side capacitor of the buck-boost converter changes with temperature. be able to.

It is a block diagram of the power converter device which includes the power converter device which concerns on one Embodiment of this invention as a 1st power converter device which concerns on a 1st Example. It is a block diagram which shows the detailed structure of the 1st power converter device which concerns on 1st Example. It is a wave form diagram with which it uses for operation | movement description of the power converter device which concerns on a 1st-3rd Example. It is a block diagram which shows the detailed structure of the 1st power converter device which concerns on 2nd Example. It is a wave form diagram with which it uses for operation | movement description of the command value production | generation part which comprises the 1st power converter device which concerns on 2nd Example. It is explanatory drawing of the capacity fall amount calculation part which comprises the 1st power converter device which concerns on 3rd Example. It is a block diagram of the power converter device which concerns on a prior art.

  Hereinafter, a preferred embodiment of a power conversion device according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a circuit configuration of an entire power conversion device (power conversion system) 10.

  As shown in FIG. 1, a power conversion device 10 according to this embodiment basically includes a first power conversion device 101, a second power conversion device 102, and the first power conversion device according to [First Example]. And a control unit 20 that constitutes a part of the second power converters 101 and 102.

  The first power converter 101 steps up and down the DC voltage Vin supplied from the DC power supply 12, for example, a nominal value 250 Vdc (= Vin), and outputs a full-wave voltage Vm of 330 Vpeak, for example, to both ends of the output-side capacitor 28. A step-up / down converter 14 is provided. In this case, the step-up / step-down converter 14 performs step-up / step-down control so that the total voltage Vm of 330 V peak is stepped down to 250 V peak corresponding to the DC voltage Vin and boosted by 70 V peak added to the 250 V peak.

  The second power converter 102 includes an inverter 16 that converts the full-wave voltage Vm to the AC voltage Vx, and a stabilization circuit that stabilizes the AC voltage Vx and outputs an output voltage Vo of, for example, an AC voltage of 200 Vrms to the load 220. 18.

  The control unit 20 controls the buck-boost converter 14 and the inverter 16.

  In this embodiment, the control unit 20 is configured by an ECU (Electronic Control Unit). The ECU is a computer including a microcomputer, such as a CPU (Central Processing Unit), a ROM (including EEPROM) as a memory, a RAM (Random Access Memory), an A / D converter, a D / A converter, etc. Input / output device, a timer as a time measuring means, etc., and the CPU reads and executes a program recorded in the ROM so that various function realizing units, for example, a control unit, a calculation unit (calculation unit), and a process It functions as a part.

  2 shows the step-up / step-down converter 14 in FIG. 1 reprinted, and detailed circuit configurations of the converter control unit 42 and the command value generation unit 26 in the control unit 20 of the power conversion apparatus 10 shown in FIG. Show. In FIG. 2, the second power conversion device 102 and the load 220 including the inverter 16 and the stabilization circuit 18 shown in FIG.

  In FIG. 1, the DC power supply 12 is, for example, a solar cell or a fuel cell, and the output DC voltage Vin can vary, but the output voltage Vo is made stable AC by the action of the power conversion device 10.

  1 and 2, the buck-boost converter 14 includes switching elements 80a, 80b, 80c, and 80d such as MOSFETs or IGBTs, and diodes connected in reverse to the switching elements 80a, 80b, 80c, and 80d, respectively. 23 and a reactor 82.

  The collector of the high-side switching element 80 a and the cathode of the diode 23 are connected to the plus side of the DC power supply 12, and the emitter of the low-side switching element 80 b and the anode of the diode 23 are connected to the minus side of the DC power supply 12.

  Further, the collector of the high-side switching element 80c and the cathode of the diode 23 are connected to the plus side of the full-wave voltage Vm. The emitter of the low-side switching element 80d and the anode of the diode 23 are connected to the negative side of the full-wave voltage Vm.

  Between the connection point between the emitter of the switching element 80a on the input phase arm side and the collector of the switching element 80b, and the connection point between the emitter of the switching element 80c on the output phase arm side and the collector of the switching element 80d, At this time, the reactor 82 for storing or releasing energy is connected.

  The full-wave voltage Vm that is the voltage across the capacitor 28 is taken in by the voltage sensor 29 and supplied to the duty calculator 62 in the inverter controller 44.

The capacitor current ic flowing in the capacitor 28 is taken in by the current sensor 30 and supplied to the reduction input terminal of the subtractor 104 and the capacity decrease amount calculation unit 32 in the converter control unit 42. Since the capacitor current ic is expressed as shown in the following equation (1) when the capacitance of the capacitor 28 is C, it is also possible to differentiate the full wave voltage Vm obtained by the voltage sensor 29 with a differentiator. can get. Note that equation (1) can be solved with full wave voltage Vm and changed to equation (2).
ic (t) = C × {dVm (t) / dt} (1)
Vm (t) = (1 / C) × ∫ic (t) dt (2)

  As shown in FIG. 1, the inverter 16 is formed as a bridge circuit by switching elements 22 a, 22 b, 22 c, and 22 d such as MOSFETs or IGBTs each having a reverse diode 23 connected in parallel.

  The collectors of the high-side switching elements 22a and 22c are connected to the plus-side line 34a, and the emitters of the low-side switching elements 22b and 22d are connected to the minus-side line 34b. The connection point between the emitter of the switching element 22a and the collector of the switching element 22b branches to the first output line 36a, and the connection point of the emitter of the switching element 22c and the collector of the switching element 22d branches to the second output line 36b. is doing.

  The inverter 16 basically steps down the full wave voltage Vm input to the inverter 16 to generate an output. In the step-down operation, the inverter output voltage Vx is output in relation to Vx = Vm × 2 × (Q−0.5) with respect to the full-wave voltage Vm that is an input voltage. Here, the values in parentheses are positive when the argument Q is 0.5 or more and negative when it is less than 0.5. Q is a basic signal described later.

  The stabilization circuit 18 is configured as a low-pass filter, and includes an inductor 38 (in-phase transformer) inserted in series with the first output line 36a and the second output line 36b, and a capacitor 40 provided on the downstream side of the inductor 38. And have. The output voltage Vo stabilized by the stabilization circuit 18 is supplied to the load 220.

  The control unit 20 includes a converter control unit 42 that performs chopper control of the buck-boost converter 14 and an inverter control unit 44 that controls the inverter 16. The converter control unit 42 and the inverter control unit 44 control the buck-boost converter 14 and the inverter 16 while synchronizing.

  As shown in FIG. 2, the first power conversion device 101 according to the first embodiment includes a DC voltage Vin supplied from the DC power supply 12 as an input and outputs a full-wave voltage Vm across the output-side capacitor 28. A voltage converter 14, a command value generation unit 26 for generating an output voltage command value Vmcom for defining the full-wave voltage Vm, and for generating a capacitor current command value iccom for defining the current ic flowing in the capacitor 28, a capacitor A capacity reduction amount calculation unit 32 for calculating the capacity reduction amount ΔCn in 28 time units, and a correction value in time units according to the capacity reduction amount ΔCn in time units of the capacitor 28 to be added to the output voltage command value Vmcom. (Command voltage increase amount) A correction value calculation unit 34 for obtaining ΔVn and a converter control unit 42 are provided.

  When obtaining the capacity decrease amount ΔCn in time units, the capacity decrease amount calculation unit 32 sets the time unit correction value (command voltage increase amount) ΔVn output from the correction value calculation unit 34 to a zero value, and the proportional unit 112. In addition, when the correction duty output from the proportional device 114 is zero, it can be calculated based on the difference between the capacitor current ic flowing in the capacitor 28 and the capacitor current command value iccom.

Specifically, as shown in the following equation (3), the amount of decrease in capacity ΔCn in units of time is calculated. In addition, (4) Formula shows average capacity | capacitance fall amount (DELTA) C.
ΔCn = Cini {(iccom (n) −ic (n)) / iccom (n)}
... (3)
ΔC = ΣΔCn / T (4)
Cini: initial value of the capacitance of the capacitor 28 stored in the initial value memory 122 iccom (n): capacitor instantaneous current command value ic (n): capacitor instantaneous current measured value ΔCn: capacitance decrease in time unit ( Capacity difference in hour unit)
ΣΔCn: sum of capacity differences for one period T: time for one period of full wave voltage [s] (see FIG. 3)

The correction value calculation unit 34 corrects the output voltage command value Vmcom according to the capacitance decrease amount ΔCn of the capacitor 28 in the time unit based on the following equation (5) (in time unit: Command voltage increase amount) ΔVn is calculated.
ΔVn = [{1 / (Cini−ΔCn)} − 1 / Cini] ×
∫iccom (n) · dt (5)

  The command value generator 26 includes a sine wave generator 46, an absolute value circuit 48, an adder 106, an amplifier 50, an initial value memory 122, a multiplier 124, a differentiator 110, and a buffer 56. Have.

  Hereinafter, description will be made with reference to the waveform diagram of FIG.

  The sine wave generator 46 has a sine waveform (sine wave command value) Vs having the same frequency and the same peak value (peak value) as the AC waveform scheduled to be obtained as the output voltage Vo (see FIGS. 1 and 3) at the load 220. (See FIGS. 2 and 3) is generated in real time.

  The absolute value circuit 48 obtains the absolute value of the sine waveform Vs supplied from the sine wave generation unit 46 to obtain a full-wave rectified waveform, and generates an output voltage command value Vmcom (see FIGS. 1 to 3).

  The adder 106 adds a correction value (command voltage increase amount) ΔVn corresponding to the temporal capacity decrease amount ΔCn of the capacitor 28 to the output voltage command value Vmcom as a full-wave rectified waveform in real time, thereby correcting the output voltage. Command value Vcom (see FIGS. 1 to 3) (Vcom = Vmcom + ΔVn) is output.

The output voltage correction command value Vcom is corrected to the output voltage command value Vmcom by the multiplier 107 in the command value generation unit 26A as shown in the equations of FIGS. 4, 5 and (6) according to the [second embodiment]. It can also be obtained by multiplying the value (constant value) A (A ≧ 1). The correction value A is calculated as shown on the right side of the following equation (6) using the average capacitance decrease amount ΔC and the initial value Cini of the equation (4) output from the capacitance decrease amount calculation unit 32A. It can be calculated by the unit 34A.
Vcom = A × Vmcom = Vmcom × Cini / (Cini−ΔC)
(6)

  The capacity reduction amount calculation unit 32A for calculating the average capacity reduction amount ΔC includes a timer 33 for accumulating the energization time for the capacitor 28, and the capacitor 28, as shown in FIG. 6 according to the [third embodiment]. It is also possible to include a memory 35 that stores in advance a characteristic 37 (capacitance value attenuation characteristic with respect to energization time) 37 of the capacity decrease amount ΔC with time from the initial capacity value Cini. In the case of the [third embodiment], it is not necessary to input the capacitor instantaneous current command value iccom (n) and the capacitor instantaneous current actual measurement value ic (n) to the capacity decrease amount calculation unit 32B. The capacity decrease amount ΔC can be obtained by referring to the characteristic 37 of the capacity decrease amount ΔC stored in the memory 35 based on the energization time measured by the timer 33. The characteristic 37 may be an approximate expression (formula).

  1, 2, and 4, the amplifier 50 amplifies the output voltage correction command value Vcom. This amplification factor is small, for example, about 1.1 times. The amplification by the amplifier 50 is performed in order to set a certain margin in order to obtain a desired output voltage Vo.

  As described above, the initial value memory 122 stores a capacitance initial value Cini that is an initial value of the capacitance of the capacitor 28.

  Differentiator 110 differentiates output voltage command value Vmcom. By multiplying this differential value by the initial capacitance value Cini of the capacitor 28 by the multiplier 124, a capacitor current command value iccom [iccom = Cini × {dVmcom / dt}] for defining the capacitor current ic flowing in the capacitor 28 is obtained. (Refer to FIGS. 1 to 4) and supplied to the converter control unit 42, the correction value calculation units 34 and 34A, and the capacity decrease amount calculation units 32 and 32A.

  The buffer 56 functions as a buffer for the sine waveform Vs supplied from the sine wave generation unit 46, and supplies the sine waveform Vs to the duty calculation unit 62 constituting the inverter control unit 44.

  On the other hand, the converter control unit 42 includes a step-down duty calculation unit 86, a step-up duty calculation unit 88, a subtractor 104, proportional devices 112 and 114, adders 92 and 94, comparators 96 and 98, and output inversion. Units 130 and 132, and a carrier wave generation unit 52.

  As shown in FIGS. 2 and 4, the step-down duty calculator 86 divides the output voltage correction command value Vcom by the DC voltage Vin detected by the voltage sensor 84 to obtain the step-down duty (Vcom / Vin).

  The step-up duty calculator 88 subtracts the quotient obtained by dividing the DC voltage Vin by the output voltage correction command value Vcom from the value 1 to obtain the step-up duty (1-Vin / Vcom).

  The subtractor 104 subtracts the actual capacitor current ic detected by the current sensor 30 from the capacitor current command value iccom to calculate the deviation Δic (Δic = iccom−ic).

  The proportional devices 112 and 114 multiply the deviation Δic by a proportionality constant k and supply it to the adders 92 and 94 as a corrected duty k · Δic. A proportional integrator may be used instead of the proportional units 112 and 114.

  The adder 92 adds the correction duty k · Δic to the step-down duty (Vcom / Vin) and supplies it to the comparison input terminal (+ input terminal) of the comparator 96.

  The adder 94 adds the correction duty k · Δic to the boosting duty (1−Vin / Vcom) and supplies it to the comparison input terminal (+ input terminal) of the comparator 98.

  The carrier wave generation unit 52 generates a high-frequency wave, for example, a 20 [kHz] triangular wave, which is the basis for chopper driving the buck-boost converter 14. The triangular wave generated by the carrier wave generation unit 52 has a waveform with a minimum value of 0 and an amplitude on the plus side.

  The comparator 96 receives the triangular wave supplied from the carrier wave generation unit 52 at the reference input terminal (−input terminal), compares it with the signal supplied from the adder 92, and turns on according to the magnitude of both waveforms. A signal or an off signal is output. The output signal is directly supplied to the gate of the switching element 80a and is supplied to the gate of the switching element 80b via the output inverter 130.

  The comparator 98 receives the triangular wave supplied from the carrier wave generation unit 52 at the reference input terminal (−input terminal), compares it with the signal supplied from the adder 94, and turns on the signal according to the magnitude of both waveforms. Alternatively, an off signal is output. This output signal is directly supplied to the gate of the switching element 80d and is also supplied to the gate of the switching element 80c via the output inverter 132.

  When the step-up / step-down converter 14 is boosted, the switching element 80a is turned on, the switching element 80b is turned off, the switching element 80c is turned off, and the switching element 80d is turned on / off, whereby the DC voltage Vin is controlled. Is boosted. That is, energy is stored in the reactor 82 from the DC power supply 12 through the switching element 80a when the switching element 80d to be controlled on / off is turned on, and energy stored in the reactor 82 is passed through the diode 23 (switching element 80d when the switching element 80d is turned off). If 80c is a MOSFET, it is boosted by being supplied to capacitor 28 and load R (through this MOSFET).

  When the step-up / step-down converter 14 is stepped down, the switching element 80b is turned off, the switching element 80c is turned on, and the switching element 80d is turned off, so that the switching element 80a is turned on / off, so that the DC voltage Vin is stepped down. Is done. That is, the DC voltage Vin is stepped down by the low-pass filter of the reactor 82 and the capacitor 28 (and the load R) when the switching element 80a to be turned on / off is turned on, energy is stored in the reactor 82, and further, when the switching element 80a is turned off. When the diode 23 is turned on and current is supplied from the reactor 82 to the capacitor 28 and the load R through the diode 23, the DC voltage Vin is lowered.

  Since the operation of the second power conversion device 102 is disclosed in Patent Document 1, in brief, the inverter control unit 44 includes a carrier wave generation unit 60, a duty calculation unit 62, a comparator 64, and output inversion. Instruments 68 and 70.

  The carrier wave generation unit 60 is a part that generates a high-frequency triangular wave that serves as a reference for PWM control of the inverter 16. As shown in FIG. 1, the triangular wave generated by the carrier wave generation unit 60 has a waveform that changes between a plus side and a minus side when the median is 0. The carrier wave generation unit 60 may use the triangular wave obtained from the carrier wave generation unit 52 by shifting it so that the positive side and the negative side have the same peak value.

  The duty calculator 62 determines the inverter operation command by dividing the sine waveform Vs supplied from the buffer 56 of the command value generator 26 by the full-wave voltage Vm obtained from the voltage sensor 29, and controls the inverter 16. A signal (inverter operation command) Q (see FIGS. 1 and 3) is generated.

  Specifically, the duty calculator 62 obtains the basic signal Q as Q = 1/2 × (Vs / Vm + 1). The level adjustment is performed by adding +1 to the divided result and multiplying by 1/2.

  The comparator 64 compares the basic signal Q supplied from the duty calculator 62 with the triangular wave supplied from the carrier wave generator 60, and outputs an ON signal or an OFF signal according to the magnitude of both waveforms, and the switching element 22a. And 22d. The output inverters 68 and 70 invert the output of the comparator 64 and supply it to the gates of the switching elements 22b and 22c.

  That is, with reference to the timing when the full-wave voltage Vm of the full-wave rectified waveform output from the step-up / down converter 14 becomes 0, the switching elements 22a and 22d of the first switching element pair are kept at a constant high value in every other period. The switching elements 22b and 22c of the second switching element pair are turned on with a constant duty having a small value. In every other period, the switching elements 22a and 22d of the first switching element pair are turned on with a constant value of a small value, and the switching elements 22b and 22c of the second switching element pair are turned on with a constant value of a high value. turn on. Thereby, the output voltage Vo (refer FIG. 3) which is a desired peak value is obtained.

  As described above, according to the above-described embodiment, the first power converter 101 receives the DC voltage Vin supplied from the DC power supply 12 and outputs the full-wave voltage Vm across the output-side capacitor 28. The step-up / step-down converter 14 generates an output voltage command value Vmcom for defining the full-wave voltage Vm, and a command value generation unit 26 for generating a capacitor current command value iccom for defining the capacitor current ic flowing in the capacitor 28. And capacitance reduction amount calculation units 32, 32A and 32B for calculating the capacitance reduction amounts ΔC and ΔCn of the capacitor 28, and a correction value ΔVn for correcting the output voltage command value Vmcom according to the capacitance reduction amounts ΔCn and ΔC of the capacitor 28. , A for calculating correction values 34 and 34A for calculating A, and output voltage correction command value Vcom corrected by correction values ΔVn and A The step-down duty (Vcom / Vin) and the step-up duty (1-Vin / Vcom) based on the deviation Δic (Δic = iccom-ic) between the capacitor current ic flowing through the capacitor 28 and the capacitor current command value iccom, respectively. By controlling the buck-boost converter 14 by reflecting the correction duty k · Δic, even if the capacitance of the capacitor 28 decreases, the full-wave voltage waveform Vm having a small desired waveform distortion at both ends of the capacitor 28, in other words, A full-wave voltage waveform Vm approximating the effective value conversion necessary for the inverter at the next stage can be obtained.

  Here, when generating the capacitor current command value iccom for defining the current flowing through the capacitor 28, the command value generation units 26 and 26A differentiate the output voltage command value Vmcom for defining the full wave voltage. Can be generated.

  Further, when the capacitor current flowing through the capacitor 28 is obtained, it may be obtained directly from the output of the current sensor 30 connected in series with the capacitor 28, and the output of the voltage sensor 29 for measuring the voltage across the capacitor 28 is differentiated. It may be obtained based on the output.

  Further, the capacity decrease amount calculation unit 32 calculates the capacity decrease amount ΔCn in time units as the initial capacity value Cini × {(capacitor instantaneous current command value iccom (n) −capacitor instantaneous current measured value ic (n)) / capacitor instantaneous. The correction value calculation unit 34 calculates the correction value ΔVn to be added to the output voltage command value Vmcom as [{1 / (capacity initial value Cini−capacity decrease in time unit)]. Amount ΔCn)} − 1 / capacitance initial value Cini] × ∫ (capacitor instantaneous current command value iccom (n)) dt.

  Furthermore, the capacity decrease amount calculation unit 32A sets the capacity decrease amount ΔCn in time units to the capacity initial value Cini × {(capacitor instantaneous current command value iccom (n) −capacitor instantaneous current measured value ic (n)) / capacitor. After calculating as the instantaneous current command value iccom (n)}, the capacity decrease amount ΔC is calculated by Σ (capacity decrease amount ΔCn in time unit) / time T of one cycle of the full-wave voltage, and the correction value calculation unit 34A Can calculate the correction value A for multiplying the output voltage command value Vmcom as a capacity initial value Cini / (capacity initial value Cini−capacity reduction amount ΔC).

  If the capacitor 28 is the electrolytic capacitor used in the present embodiment, the capacitance decrease amount ΔC generally decreases as the (ambient) temperature becomes low, but the first decrease in FIGS. According to the power conversion device 10 having the power conversion device 101, since the capacitor current ic is detected in real time, the temperature of the capacitor 28 is measured by the temperature sensor, and the temperature characteristic of the capacitance initial value Cini is held in the memory. Thus, it is possible to calculate the command voltage increase amount ΔVn or the correction value A as a correction value in consideration of the capacity decrease amount ΔC due to the change in the ambient temperature.

  It goes without saying that various configurations can be adopted without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Power converter 12 ... DC power supply 14 ... Buck-boost converter 16 ... Inverter 18 ... Stabilization circuit 20 ... Control part 22a-22d, 80a-80d ... Switching element 26, 26A ... Command value generation part 28 ... Output side capacitor | condenser 30 ... Current sensors 32, 32A, 32B ... Capacity reduction amount calculation units 34, 34A ... Correction value calculation unit 42 ... Converter control unit 44 ... Inverter control unit 62 ... Duty calculation unit

Claims (5)

A buck-boost converter that takes a DC voltage supplied from a DC power supply as an input and outputs a full-wave voltage across the capacitor on the output side;
A command value generator for generating an output voltage command value for defining the full-wave voltage and generating a capacitor current command value for defining a current flowing through the capacitor;
A capacity reduction amount calculating unit for calculating a capacity reduction amount of the capacitor;
A correction value calculation unit for calculating a correction value for correcting the output voltage command value according to the amount of capacitance decrease of the capacitor;
The step-up duty and the step-up duty based on the output voltage correction command value corrected by the correction value reflect the correction duty corresponding to the deviation between the capacitor current flowing through the capacitor and the capacitor current command value, respectively A converter control unit for controlling the pressure converter;
A power conversion device comprising: The power conversion device according to claim 1,
The command value generator is
A power conversion device, wherein when generating a capacitor current command value for defining a current flowing through the capacitor, the output voltage command value for defining the full-wave voltage is differentiated. In the power converter device according to claim 1 or 2,
The capacitor current flowing in the capacitor can be obtained directly from the output of the current sensor connected in series with the capacitor or based on the output obtained by differentiating the output of the voltage sensor that measures the voltage across the capacitor. Power converter. In the power converter device according to any one of claims 1 to 3,
The capacity decrease amount calculation unit
Calculate the amount of capacity decrease in time units as initial capacity value x {(capacitor instantaneous current command value-capacitor instantaneous current measured value) / capacitor instantaneous current command value}
The correction value calculation unit
The correction value to be added to the output voltage command value is [{1 / (capacity initial value−capacity decrease amount in time unit)} − 1 / capacity initial value] × ∫ (capacitor instantaneous current command value) dt. The power converter characterized by calculating. In the power converter device according to any one of claims 1 to 3,
The capacity decrease amount calculation unit
After calculating the capacity decrease amount in time units as initial capacity value x {(capacitor instantaneous current command value-capacitor instantaneous current measured value) / capacitor instantaneous current command value}, the capacity decrease amount is calculated as Σ (capacity in time unit Reduction amount) / time of the full wave voltage 1 period,
The correction value calculation unit
A power conversion device, wherein a correction value for multiplying the output voltage command value is calculated as capacity initial value / (capacity initial value−capacity decrease amount).

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