JP5793005B2 - Power conversion device and control device thereof - Google Patents

Description

  Embodiments of the present invention relate to a power conversion device including a rectifier circuit and an inverter circuit, and a control device.

  Generally, in a power converter that receives power from an AC system of commercial frequency, a rectifier circuit that rectifies AC voltage from the AC system and converts it to DC voltage, and an inverter circuit that converts DC voltage to AC voltage are used in combination. Yes. Of these, the inverter circuit is used as a power source for supplying AC high-voltage high-frequency power via a transformer as well as a motor drive source, or a charging device that rectifies the secondary of the transformer and charges a battery such as an EV. Applied. On the other hand, the rectifier circuit is a DC power source that supplies a DC voltage to the inverter circuit, and a circuit that includes a switching element has been proposed as an element that exhibits an excellent power factor. Among them, the pwm converter is widely used because it can perform constant control of the DC voltage (for example, Patent Document 1).

  The power conversion device using the pwm converter as described above can exhibit a high power factor with a power source power factor of approximately 1, and can operate stably without fluctuations in DC voltage. On the other hand, this type of power conversion device has a problem of high cost because the pwm converter bridge is composed of an expensive switching element. In addition, it was pointed out that the efficiency was low due to the large loss. Therefore, conventionally, a diode rectifier circuit that is low-cost and highly efficient has been proposed (for example, Patent Document 2).

  However, since the diode rectifier circuit does not use an active element, the power factor cannot be denied. In order to achieve an improvement in the high power factor, the smoothness after rectification should be improved to reduce the peak current on the AC side. Specifically, it is effective to employ a multiphase rectifier circuit in which a small-capacitance capacitor is provided in the direct current section and the rectified current is smoothed by the small capacitor capacity.

JP 2005-94913 A JP 2010-239736 A

  In addition to the power factor reduction described above, the following problems have been pointed out in power converters including diode rectifier circuits and small capacitors. That is, unlike the pwm converter, in the diode rectifier circuit, the DC voltage directly receives the fluctuation of the AC input voltage, and is also vulnerable to the fluctuation of the load.

  If the DC voltage output from the diode rectifier circuit fluctuates due to fluctuations in the AC input voltage or load, the inverter circuit is also affected, and the voltage and power supplied to the load become unstable. For this reason, the power converter provided with the diode rectifier circuit can be applied only to a load that is not easily affected by the DC voltage fluctuation, and the narrow application range has been a problem.

  However, in recent years, the demand for power conversion devices has increased rapidly, and it has been emphasized that it is economically advantageous. Therefore, it has been desired to further expand the application field of the power conversion device including the diode rectifier circuit. Therefore, development of a control technique for a power conversion device that includes a diode rectifier circuit and that can respond quickly to fluctuations on the load side without being affected by fluctuations in DC voltage has been awaited.

  The power conversion device and the control device thereof according to the present embodiment have been proposed to solve the above problems. In this embodiment, in a control device for a power conversion device including a diode rectifier circuit, constant control of a DC voltage is possible, and stable load control is realized by supplying voltage and power to a load with high accuracy. Thus, the application range can be expanded.

In order to achieve the above object, a control device for a power conversion device according to an embodiment is characterized by the following points.
(1) The power conversion device includes a rectifier circuit that rectifies a commercial frequency AC system voltage including a diode element and outputs the rectified voltage to a DC bus, and includes a semiconductor switching element to convert the DC bus voltage to AC and power the load. And an inverter circuit for supplying.
(2) The DC bus is provided with voltage detection means for detecting the voltage value of the DC bus.
(3) An integrating means is connected to the voltage detecting means. The integrating means is configured to obtain a voltage integrated value for each cycle of the inverter frequency by taking in the voltage value detected by the voltage detecting means and resetting in synchronization with the frequency of the inverter circuit.
(4) The integration means is connected to the pwm signal generation means, and the pwm signal generation means is connected to the calculation means. The calculation means is configured to take a preset active power reference of the load and the frequency of the inverter circuit, and calculate the voltage reference for each cycle of the inverter frequency by dividing the active power reference by the frequency.
(5) The pwm signal generating means is configured to generate a pwm signal for driving the inverter circuit by comparing the voltage reference for each cycle of the inverter frequency obtained by the calculating means with the voltage integrated value obtained by the integrating means. Has been.

The circuit diagram of the power converter device which is a typical embodiment, and its control apparatus. The time chart in the case of converting a pwm signal into a phase shift type pwm signal in a typical embodiment. The circuit diagram of the pwm signal generation means in other embodiments.

1. Configuration of Representative Embodiment Hereinafter, a power conversion device and a control device thereof as a representative embodiment will be specifically described with reference to FIGS.

(1) Configuration of Power Conversion Device As shown in FIG. 1, the power conversion device A includes a converter unit including a rectifier circuit and an inverter unit connected thereto, and a commercial frequency is provided on the power receiving end side of the converter unit. A three-phase AC power source 1 is connected, and an ozone generator 14 as a load is connected to the power transmission end side of the inverter unit.

  The power converter A is provided with diode bridges 51 and 52 constituting a rectifier circuit. The AC power supply 1 is connected to the input side of the diode bridges 51 and 52 via the transformer 50, and the DC bus 7 is connected to the output side. The diode bridges 51 and 52 are provided with a small-capacitance capacitor 53 and a surge energy absorption circuit 54. That is, the converter unit of the power conversion device A includes diode bridges 51 and 52, a small-capacitance capacitor 53, and a surge energy absorption circuit 54.

  On the other hand, the inverter unit of the power conversion device A includes an inverter bridge 11, a transformer 12, and a reactor 13. The inverter bridge 11 is a circuit that converts the voltage of the DC bus 7 into AC and supplies it to the ozone generator 14, and has four IGBTs. Symbols GA to GD in FIG. 1 indicate IGBT gates in the inverter bridge 11. The transformer 12 is a step-up transformer, and is installed between the inverter bridge 11 and the ozone generator 14. The reactor 13 is connected to the transformer 12 in series.

  When such a power conversion device A receives three-phase alternating current from the alternating current power source 1, the diode bridges 51 and 52 receive alternating current via the transformer 50. The diode bridges 51 and 52 rectify the AC voltage taken from the AC power source 1 and output the rectified voltage to the DC bus 7. Then, the inverter bridge 11 converts the DC voltage of the DC bus 7 into an AC voltage. The transformer 12 boosts the AC voltage, and supplies power to the ozone generator 14 through the reactor 13 as a resonance state with the load.

(2) Control device for power conversion device The control device B for the power conversion device A is composed of three parts. The first part is output taking means of the converter unit of the power converter A, the second part is output taking means of the inverter part, and the third part is control signal generating means for the inverter part.

(2-1) Output Capture Unit of Converter Unit The output capture unit of the converter unit includes a voltage detector 6, an integration circuit 55, and a reset circuit 56. The voltage detector 6 is means for detecting the DC voltage output from the diode bridges 51 and 52, and takes in the DC voltage value VD from the small capacitor 53 and sends it to the integrating circuit 55.

  The reset circuit 56 is a circuit that takes in the inverter frequency F and outputs a reset signal to the integration circuit 55 at the start of one cycle. The integrating circuit 55 is a circuit that receives a DC voltage value VD from the voltage detector 6 and a reset signal from the reset circuit 56, and obtains an integrated voltage value ∫Vdt obtained by integrating the DC voltage value VD.

(2-2) Output take-in means of inverter unit As output take-in means of the inverter unit, current transformer 15, transformer 16, multipliers 17 and 18, low-pass filters 19 and 20, reactive power setting device 21 and reactive power A detection signal generator 25, an active power control circuit 63, a calculation circuit 64, and an active power setting unit 66 are provided.

  The current transformer 15 and the transformer 16 are installed between the inverter bridge 11 and the ozone generator 14. The current transformer 15 is a device that detects the current value I15 output from the inverter bridge 11, and the transformer 16 is a device that detects the voltage value V16 output from the ozone generator 14.

  Multipliers 17 and 18 are connected to the current transformer 15. In addition, a multiplier 18 and a reactive power detection signal generator 25 are connected to the transformer 16, and a multiplier 17 is connected to the reactive power detection signal generator 25. The multiplier 17 receives the reactive power detection signal V25 from the reactive power detection signal generator 25.

  A low pass filter 19 is connected to the multiplier 17, and a low pass filter 20 is connected to the multiplier 18. The multiplier 17 is a circuit that calculates the reactive power Q of the ozone generator 14, and the multiplier 18 is a circuit that calculates the active power P of the ozone generator 14.

  A reactive power setting device 21 and a reactive power control circuit 23 are sequentially connected to the low-pass filter 19. The reactive power setting device 21 sets a reactive power reference Q * for the ozone generator 14. The reactive power control circuit 23 is a circuit that adjusts the inverter frequency F of the inverter bridge 11 by controlling the reactive power Q of the ozone generator 14.

  An active power setting unit 66 and an active power control circuit 63 are sequentially connected to the low pass filter 20. The active power setting unit 66 sets the active power reference P * of the ozone generator 14. The active power control circuit 63 is a circuit that performs correction processing of P * / F (described later) as a calculation result of the calculation circuit 64 in addition to the control of the active power P.

  The calculation circuit 64 divides the set active power reference P * by the active power setter 66 by the inverter frequency F, whereby the voltage reference Vm * for each cycle of the inverter frequency (= αP * / F, where α is a coefficient). Is a circuit for calculating

(2-3) Inverter Control Signal Generation Unit The inverter control signal generation unit includes a comparator 58, a pwm circuit 59, and a phase shift pwm circuit 60. These circuits are sequentially connected to the output side of the integrating circuit 55.

  The comparator 58 compares the voltage reference Vm * obtained by the calculation circuit 64 with the voltage integration value ∫Vdt obtained by the integration circuit 55. The pwm circuit 59 is a circuit that generates a pwm signal based on the comparison of the comparator 58. The phase shift pwm circuit 60 is a circuit that converts the pwm signal generated by the pwm circuit 59 into a drive signal for phase shift type pwm control.

(2-4) Operation of the control device of the power conversion device The control device B composed of the above-described components operates as follows. On the output side of the diode bridges 51, 52, the voltage detector 6 detects the DC voltage value VD of the small-capacitance capacitor 53 and sends it to the integration circuit 55.

  Since the reset circuit 56 sends a reset signal to the integration circuit 55 at the start of one cycle of the inverter frequency F, the integration circuit 55 resets based on the reset signal. The integrating circuit 55 can obtain a voltage integrated value ∫Vdt obtained by integrating the DC voltage value VD of the small-capacitance capacitor 53 from the voltage detector 6 during the period from T0 to T1 sandwiched between the reset signals. send.

  On the other hand, on the output side of the inverter bridge 11, the current transformer 15 detects the current value I 15 output from the inverter bridge 11 and sends it to the multipliers 17 and 18. The transformer 16 detects the voltage value V 16 output from the ozone generator 14 and sends it to the multiplier 18 and the reactive power detection signal generator 25.

  The multiplier 17 receives the reactive power detection signal V25 from the reactive power detection signal generator 25, obtains the product of the reactive power detection signal V25 and the current value I15 output from the current transformer 15, and sends the product to the low-pass filter 19. Then, the reactive power Q of the ozone generator 14 is calculated. The reactive power control circuit 23 takes in the reactive power reference Q * set by the reactive power setting unit 21 and the reactive power Q, and adjusts the inverter frequency F of the inverter bridge 11 so that the reactive power reference Q * becomes zero. Thus, control is performed so that the power factor of the fundamental wave becomes 1.

  The multiplier 18 sends the product of the current value I15 and the voltage value V16 to the low-pass filter 20 to calculate the active power P of the ozone generator 14. The calculation circuit 64 takes in the active power reference P * set by the active power setting unit 66 and the inverter frequency F adjusted by the reactive power control circuit 23, divides by the active power reference P * inverter frequency F, and becomes the quotient inverter. A voltage reference Vm * (= αP * / F) for each frequency cycle is obtained.

  The active power control circuit 63 takes in the active power reference P * set by the active power setting unit 66 and the active power P. The active power control circuit 63 compares and amplifies the active power P and the active power reference P * to control the active power P, and corrects αP * / F, which is a calculation result of the calculation circuit 64.

The active power P for each cycle is obtained as the product of the discharge voltage Vz of the ozone generator 14, the current i whose power factor is controlled to approximately 1, and the inverter frequency F (Equation 1). Further, when the relational expression 2 of the current i, the discharge voltage Vz, and the voltage average value Vm for each cycle is substituted into the current i of the expression 1, the active power P for each cycle is the voltage average value Vm for each cycle. And the inverter frequency F (equation 3). Since such a relationship is established, the active power control circuit 63 can correct the voltage reference Vm * (= αP * / F) obtained by the calculation circuit 64 every cycle.
P = i · Vz · F (1)
i = k · (Vm / Vz) (2)
P = k · Vm · F (3)

  The comparator 58 receives the voltage integration value ∫Vdt from the integration circuit 55, receives the voltage reference Vm * from the calculation circuit 64, and compares them. The pwm circuit 59 generates a pwm signal based on the comparison between the voltage integrated value ∫Vdt and the voltage reference Vm * by the comparator 58.

(2-5) Generation of pwm Signal The generation of the pwm signal in the pwm circuit 59 will be described more specifically with reference to FIG. 2, in order from the top, a is an operating waveform of the inverter frequency F, b is an operating waveform of the reset signal output from the reset circuit 56, c is a waveform of the voltage integrated value ∫Vdt output from the integrating circuit 55, d Is the voltage value of the voltage reference Vm *.

  The time point at which the waveform c of the voltage integral value ∫Vdt reaches the voltage value d of the voltage reference Vm * per cycle is defined as t1, and the pwm signal is generated based on this. That is, when the waveform c of the voltage integral value ∫Vdt is equal to or less than the voltage value d of the voltage reference Vm * (from T0 to t1), the pwm signal becomes H, and the waveform c of the voltage integral value ∫Vdt is the voltage value of the voltage reference Vm *. If d is exceeded (from t1 to T1), the pwm signal becomes L.

  The phase shift pwm circuit 60 converts the pwm signal generated by the pwm circuit 59 into gate signals A, B, C, and D, and uses the gates GA, GB, and IGBT gates of the inverter bridge 11 as drive signals for phase shift pwm control. A drive signal is sent to GC and GD to control the inverter bridge 11.

(2-6) Phase shift type pwm control The gate signals A, B, C, D by the phase shift pwm circuit 60 are shown in the lower part of FIG. Each gate signal A, B, C, D has the following combined waveform.

  A waveform E in FIG. 2 indicates the output voltage of the transformer 12. When the load of the transformer 12 includes an inductance component and a capacitor portion, the zero portion of the output of the transformer 12 is stabilized by setting a mode in which the primary side of the transformer 12 is short-circuited.

  In the phase shift type pwm control, the drive signal is intentionally shifted to the diagonal IGBT gate of the inverter bridge 11. According to such phase shift type pwm control, zero voltage switching can be implemented, efficiency can be improved and control can be stabilized, and the ozone generator 14 has a counter electromotive force (inductance C or the like). It is effective for.

(3) Effects of Embodiment The present embodiment as described above exhibits the following functions and effects. That is, the DC voltage value VD flowing through the small-capacitance capacitor 53 varies depending on the voltage variation of the AC power supply 1, the ripple voltage on the output side of the diode bridges 51 and 52, and the like. In this case, the voltage integration value ∫Vdt obtained by the integration circuit 55 changes at the time point t1 when it reaches the voltage reference Vm *.

  However, the area of the voltage waveform of one time pwm specified by the voltage reference Vm * does not change. Therefore, even if the rectifier circuit is the diode bridges 51 and 52, the DC voltage can be controlled to be constant. In other words, even if the DC voltage varies, the magnitude of the voltage integral value ∫Vdt until the voltage reference Vm * is reached does not change, and the DC power can be controlled constantly.

  Further, since the integral value of the converter output is inversely proportional to the inverter frequency F, the output fluctuation on the converter side can be reflected in the voltage control of the inverter bridge 11, and the integral value is reset every cycle of the inverter frequency F. Therefore, it is possible to control the inverter voltage at a very high speed.

  Further, in the present embodiment, the pwm signal generated by the pwm circuit 59 is converted into a drive signal for phase shift type pwm control by the phase shift pwm circuit 60, and the ozone generator 14 is controlled stably and with high accuracy. It is possible. In this embodiment, even if the active power P of the ozone generator 14 fluctuates, the load control is performed because the active power control circuit 63 corrects the voltage reference Vm * for each cycle while controlling the active power P. It can contribute to stabilization of.

  Therefore, even if it is a power converter device provided with the diode rectifier circuit, it is not necessary to worry about the influence of a DC voltage fluctuation, and the applicable range of an economical power converter device can be expanded. Moreover, since the stability of load control is also improved, it is possible to provide a power conversion device that is excellent in reliability and economy.

2. Other Embodiments In this specification, a plurality of embodiments according to the present invention have been described. However, the above-described embodiments are presented as examples, and are intended to limit the scope of the invention. Absent. That is, the above-described embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

  For example, in the above-described representative embodiment, when the waveform of the pwm signal is generated, the voltage integral value ∫Vdt is compared with the voltage reference Vm * (= αP * / F), but the inverter frequency F is set to the voltage integral value ∫Vdt. A multiplier 68 for multiplying may be provided, and the output of the integrating circuit 55 may be an integrated value ∫VFdt (see FIG. 3).

  In such an embodiment, the comparator 58 does not compare the voltage integral value ∫Vdt with the voltage reference Vm * (= αP * / F), but instead calculates the integral value ∫VFdt obtained by multiplying both by the inverter frequency F and the effective value. By comparing with the power reference P *, the pwm circuit 59 can generate the pwm signal.

  Therefore, it is not necessary to use the voltage reference Vm * (= αP * / F) derived by performing the division, and the calculation circuit 64 becomes unnecessary. Compared with division, multiplication is lighter in calculation load, so that the pwm signal generated by the pwm circuit 59 is the same, but the processing speed is improved.

  Although the above embodiment has been described with reference to a block diagram of hardware control, it can also be achieved by digital control or microcomputer control. Therefore, in the claims, the circuit in the above-described embodiment is described as a means. However, this means includes both a hardware configuration such as a circuit and a configuration realized by a computer program. .

  Moreover, as an aspect of the invention, a power conversion device in which the entire control device is incorporated as a control circuit may be used. Furthermore, the correction process of the voltage reference V * obtained by dividing the active power reference by the frequency of the inverter circuit can be corrected by the power control output loop of the inverter. A circuit may be provided. The diode bridge, which is a rectifier circuit, is effective in a multi-phase rectifier circuit in order to improve the power reception rate, and can be implemented by 6-phase rectification, 12-phase rectification, 18-phase rectification, 24-phase rectification and the like.

DESCRIPTION OF SYMBOLS 1 ... AC power supply 2a, 2b, 2c ... Current detector 3a, 3b, 3c, 13 ... Reactor 5 ... Capacitor 6 ... Voltage detector 7 ... DC bus 11 ... Inverter bridge 12, 16, 50 ... Transformer 14 ... Ozone generation Device 15 ... Current transformers 17, 18, 68 ... Multiplier 19, 20 ... Low pass filter 21 ... Reactive power setting device 22 ... Active power setting device 23 ... Reactive power control circuit 24, 63 ... Active power control circuit 25 ... Reactive power Detection signal generators 51, 52 ... Diode bridge 53 ... Small capacitance capacitor 54 ... Surge energy absorption circuit 55 ... Integration circuit 56 ... Reset circuit 58 ... Comparator 59 ... pwm circuit 60 ... Phase shift pwm circuit 64 ... Calculation circuits A, C ... Power converter B, D ... Power converter control device F ... Inverter frequency P ... Active power P * ... Active power reference Vm * ... In Over data frequency 1 voltage reference of each cycle

Claims (6)

A rectifier circuit that rectifies a commercial frequency AC system voltage including a diode element and outputs the rectified voltage to a DC bus; and an inverter circuit that includes a semiconductor switching element and converts the voltage of the DC bus to AC and supplies power to a load. A control device used in a power converter,
DC voltage detecting means for detecting a DC voltage of the DC bus,
Integrating means for obtaining a voltage integral value for each cycle of the inverter frequency by resetting the DC voltage detected by the DC voltage detecting means in synchronization with the output frequency of the inverter circuit;
Active power setting means for setting an active power reference of the load;
A calculating means for dividing the active power reference set by the active power setting means by the frequency of the inverter circuit to calculate a voltage reference for each cycle of the inverter frequency;
A power converter comprising: a pwm circuit that compares the voltage integrated value obtained by the integrating means with a voltage reference calculated by the calculating circuit and generates a pwm signal for driving the inverter circuit. Control device. A rectifier circuit that rectifies a commercial frequency AC system voltage including a diode element and outputs the rectified voltage to a DC bus; and an inverter circuit that includes a semiconductor switching element and converts the voltage of the DC bus to AC and supplies power to a load. A control device used in a power converter,
DC voltage detecting means for detecting a DC voltage of the DC bus,
Integrating means for obtaining a voltage integral value for each cycle of the inverter frequency by resetting the DC voltage detected by the DC voltage detecting means in synchronization with the output frequency of the inverter circuit;
Active power setting means for setting an active power reference of the load;
Multiplication means for obtaining a product of the voltage integral value obtained by the integration means and the output frequency of the inverter circuit;
And active power reference of the load setting of the effective power setting hand stage, and wherein by comparing the product obtained in the multiplication means, equipped with a pwm circuit, for generating a pwm signal for driving the inverter circuit Control device for power conversion device.   The control apparatus for a power conversion apparatus according to claim 1, further comprising a phase shift pwm circuit that converts a pwm signal generated by the pwm circuit into a phase shift pwm signal.   The active power control means for taking in the active power of the load is provided, and the voltage reference calculated by the calculation circuit is corrected by the active power control means based on the active power of the load. The control apparatus of the power converter device of Claim 1.   A power conversion device, wherein the control device according to claim 1 is incorporated.   The power converter according to claim 5, wherein the rectifier circuit is a multiphase rectifier circuit.

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