Active smoothing control DC power supply

Abstract

When a DC power supply is connected to a single-phase power supply or a single-phase load via a DC-AC converter, extremely large power pulsations occur. Therefore, electrolytic capacitors, which can provide large capacitance, are widely used in smoothing circuits in DC power supplies. However, they have major issues with their vulnerability to temperature rise and short lifespan. [Solution] A smoothing capacitor circuit using a film capacitor with few lifespan issues is configured in parallel with the DC power supply circuit via a step-up or step-down DC / DC converter, and significant charge / discharge control of the capacitor is performed using switching control to suppress DC voltage pulsation, thereby realizing a capacitor with an equivalently large capacity and achieving the elimination of electrolytic capacitors.

Description

[Technical Field]

[0001] The present invention does not use an electrolytic capacitor used in a DC power supply circuit as a smoothing capacitor, but uses a capacitor with a relatively small capacity and a switch circuit that have few life problems to smooth DC voltage pulsation. Active smoothing control DC power supply It is related to. [Background technology]

[0002] When a DC power supply is connected to a single-phase power supply or a single-phase load via a DC-AC converter, extremely large power pulsations occur. Therefore, electrolytic capacitors, which can provide large capacitance, are widely used in smoothing circuits in DC power supplies. However, they have major issues, such as their vulnerability to temperature rise and short lifespan.

[0003] For this reason, electrolytic capacitors are used in power supply devices that handle single-phase power, from small-capacity DC power adapters to general-purpose DC power supply devices, DC power supplies for inverter air conditioners with relatively large capacities, and even larger DC power supplies for electric railways. There are Since this is a bottleneck in product lifespan, research and development has been focused on single-phase power supply circuits, excluding electrolytic capacitors. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5813934: "Electrolytic capacitor-less motor drive inverter" [Patent Document 2] Patent No. 5820544: "Output voltage ripple compensation for PFC converters" [Patent Document 3] Patent Publication No. 2024-173477: "Active Capacitor" Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, when connected to a single-phase power supply or load, large power pulsations occur, twice the AC circuit frequency, which causes large DC voltage pulsations, and large-capacity electrolytic capacitors are used for smoothing purposes.

[0006] However, because electrolytic capacitors have a significant impact on the lifespan of power supply devices, it is possible to use film capacitors instead of electrolytic capacitors, but film capacitors have a smaller capacitance value than electrolytic capacitors, so they cannot be used as a direct replacement.

[0007] Furthermore, in the case of single-phase power supplies, capacitor-input rectifier circuits distort the AC current waveform, so recently PFC converters, which use a control method to convert the AC current waveform into a sine wave to obtain DC output, have become widely used, and when moving towards electrolytic capacitor-less systems, it is necessary to achieve both of these requirements.

[0008] Figure 1 shows the operating waveforms of a circuit in which a DC voltage controlled power supply is configured from a single-phase power supply ea and a PFC converter, a large electrolytic capacitor Cd is connected to the DC output terminal, and a DC voltage ed with suppressed DC voltage pulsation is connected to a DC load.

[0009] Here, if the single-phase AC voltage ea is ea = / 2 Ea sinωat and the AC current ia is ia = / 2 Ia sinωat, the power pa from the PFC converter is expressed by the following equation: pa=ea*ia=EaIa (1-cos2ω a t) ----------------------------------------------------- (1) Not only the DC power EaIa but also the power ripple component EaIa cos2ω, which is twice the power frequency, is shown. a If the output voltage ed of the PFC converter is controlled by the electrolytic capacitor Cd to a pulsation-free voltage ed=Ed (constant) equal to the reference value, including the power of t, then the output current ids from the PFC converter is expressed as Id=(EaIa / Ed), as follows: ids=pa / Ed=(EaIa / Ed)* (1-cos2ω at)= Id (1-cos2ω a t) --------------------------- (2) The current waveform is shown below.

[0010] Therefore, in order to pass a constant current idL=IdL to the DC load with respect to the output current ids from the PFC converter, the current ic of the electrolytic capacitor Cd is expressed as the difference current between the two currents in the following equation: ic=ids-idL= Id (1-cos2ω a t)-IdL= -Id cos2ω a t ------------------------------------ (3) It is necessary to connect an electrolytic capacitor Cd of the required size to pass the current.

[0011] Figure 2 shows the operating current waveform in a circuit configuration in which a single-phase sinusoidal wave PWM control inverter outputs an AC output voltage to a power bus using a pulsation-free DC voltage control power supply or storage battery.

[0012] In this case, as in the case of a PFC converter, a DC current containing power pulsation with a frequency twice the AC output frequency flows into the DC power supply, so the following equation is used, similar to equation (3): ic=ids-idL= Ids-IdL (1-cos2ω b t) = IdL cos2ω b t---------------------------------- (4) It is necessary to connect an electrolytic capacitor Cd of the required size to pass the current.

[0013] Figure 3 shows the circuit configuration and operating waveforms when the DC voltage control power supply is configured with a PFC converter and the DC load is outputted with an AC output voltage by a single-phase sinusoidal wave PWM control inverter.

[0014] In this case, power pulsation from the DC voltage control power supply side and power pulsation from the DC load side will flow into the DC bus, so in order to sufficiently reduce the DC voltage pulsation, the electrolytic capacitor must be ic=ids-idL= Id (1-cos2ω a t) -IdL (1-cos2ω b t)= Id(cos2ω b t-cos2ω a t)------------(5) It is necessary to connect an electrolytic capacitor Cd of the required size to pass the current Id = IdL.

[0015] "Patent Document 1" is an inverter air conditioner that drives a motor via a three-phase inverter with the full-wave rectified output of a single-phase power supply, and is characterized by a low-cost inverter that can simultaneously achieve measures against power supply harmonics and eliminate the need for electrolytic capacitors without using a PFC converter, and has been put into practical use.

[0016] In this case, the need for an electrolytic capacitor is eliminated by reducing the current difference between the full-wave rectified output current of the single-phase power supply and the DC load current due to the load current of the motor connected to the three-phase inverter connected as a DC load.

[0017] However, because the DC load circuit is limited to the inverter air conditioner drive motor load and is based on a special control method that is realized by the drive power pulsation to the motor, while it achieves an electrolytic capacitor-less air conditioning system, it does not provide a countermeasure against power pulsation as a general stable DC power supply.

[0018] "Patent Document 2" describes a method for connecting a storage battery to the DC output terminal of a PFC converter, whereby the power pulsating current of the PFC converter flows into the storage battery, causing the temperature of the storage battery to rise. Instead of a large-capacity smoothing electrolytic capacitor, a film capacitor connected to the DC bus via a step-down DC / DC converter is used. Ta The aim is to reduce DC voltage pulsation in a DC bus to which a storage battery is connected by using a capacitor to pass charge / discharge current.

[0019] Specifically, the step-down DCDC converter is controlled by PWM switching using PI control, with the command voltage being the sum of the amplified amount of the detected output voltage ripple component of the DC bus voltage and the deviation between the voltage of the film capacitor connected to the step-down DCDC converter and a fixed reference value.The equivalent capacitor value is changed depending on the amplified amount of the output voltage ripple component, and the DC output voltage ripple is compensated for using a film capacitor instead of a large-capacity electrolytic capacitor which has lifespan issues.

[0020] In "Patent Document 2," a step-down DC-DC converter is used as the main circuit configuration, so a large current in the form of a large switching pulse due to PWM control flows from the DC bus, which is a concern as it may have a significant impact on peripheral devices. In addition, the maximum operating voltage of the film capacitor is 1000 V, which is the DC bus voltage. below Considering that the energy stored in a capacitor is proportional to the square of the voltage, the maximum operating voltage is From DC bus voltage Low-cost film capacitors with large capacitance values but It is necessary.

[0021] Furthermore, with this proposed control method, if the amount of amplification of the output voltage ripple component is increased, there is a concern that the proportion of this component will increase and the average voltage control of the capacitor connected to the step-down DC-DC converter will become ineffective.Furthermore, since the PWM switching signal is obtained directly via the PI controller based on the above-mentioned command voltage, there is a problem with the control system configuration, such as the risk of an uncontrollable pulse-like excessive current flowing in the DC-DC converter.

[0022] Patent Document 3 also proposes a control method for suppressing the ripple voltage of a DC power supply by using a circuit configuration that uses a step-down DC-DC converter similar to that of Patent Document 2, which is composed of a set of half-bridge circuits and capacitors, as an active capacitor, as a technology for omitting or miniaturizing the smoothing capacitor of a DC circuit.

[0023] However, similar to the circuit configuration using a step-down DC-DC converter in the aforementioned "Patent Document 2," there are problems such as a low operating voltage of the capacitor and a large switching pulse current flowing into the connected DC bus.

[0024] Furthermore, Patent Document 3 proposes other forms of active capacitors, such as a method of halving the capacitance of the capacitors used by configuring them with two sets of half-bridge circuits and capacitors, and a method of combining multiple sets of active capacitors, but these do not perform control operations as a boost DC-DC converter, which has many notable advantages as an active capacitor as applied in the present invention. [Means for solving the problem]

[0025] "Patent Document 2" and "Patent Document 3" Charging and discharging with DC bus using DC / DC converter As an active capacitor Control actions are common control techniques, The present invention provides a specific and more effective solution for realizing a DC power supply that does not use an electrolytic capacitor by using an active smoothing control capacitor.

[0026] The present invention provides As in "Patent Document 1" Not limited to special load circuits, but also as a voltage ripple countermeasure for general DC power supply circuits, Instead of the step-down DC-DC converter used in Patent Document 2 and Patent Document 3, a step-up DC-DC converter, which is more effective as an active capacitor, is connected, and by operating the capacitor at a voltage higher than the DC bus voltage, an active capacitor that realizes an equivalently larger capacity capacitor is connected to the DC output terminal for smoothing, thereby achieving an electrolytic capacitor-less DC power supply circuit.

[0027] Figure 4 shows a smoothing circuit using a large-capacity electrolytic capacitor as a smoothing capacitor for the output of a DC voltage control power supply such as a PFC converter, and a smoothing circuit using an active capacitor in parallel. Weapon 1 shows a circuit with a capacitor connected.

[0028] Figure 5 shows the operating waveforms of the two circuit configurations. (a) In the smoothing capacitor circuit, the PFC converter Electricity As shown in equation (2), the current ids flows as a large pulsating current twice the AC power supply frequency, but the pulsation of the DC terminal voltage ed can be reduced by appropriately flowing the current ic from the electrolytic capacitor or the controlled current icx as a smoothing circuit current.

[0029] Here, the DC voltage ripple reduction width is (a) a value (Δec) determined by the circuit constants including the capacitance of the capacitor in the case of a smoothing capacitor using an electrolytic capacitor, but (b) Weapon In the case of a smoothing capacitor, the smoothing capacitor Cx can be charged and discharged within a range in which the voltage fluctuation width Δecx of the smoothing capacitor Cx can be controlled, so that even a smoothing capacitor Cx with a small capacitance value can sufficiently reduce DC voltage pulsation, which is a feature of the basic control principle utilized in this invention.

[0030] FIG. 6 shows an active Weapon Capacita Active smoothing control DC power supply includingThe main circuit configuration and basic configuration diagram of the control system are shown. By controlling the DC current waveform ids and DC output voltage Ed (average value), the DC voltage control that matches the reference value with a sinusoidal AC current waveform from a single-phase power supply in the PFC converter circuit is achieved. For DC output of power supply circuit The DC bus line to which the DC load is connected is connected to a smoothing capacitor Cx, and the smoothing capacitor Cx is connected to a bidirectional DC / DC converter that controls the current icx to reduce DC voltage ripple while maintaining the operating voltage Ecx of the smoothing capacitor Cx at an appropriate reference value. 。

[0031] Figure 7 shows As a bidirectional DC / DC converter The DC voltage control power supply unit is a PFC converter circuit using a boost chopper circuit, and the active element is configured by connecting a smoothing capacitor cx to the DC side of a boost type DCDC converter consisting of a half-bridge circuit and an inductor L2. Weapon Includes capacitor circuit Main circuit configuration as an active smoothing control DC power supply 1 shows a control block diagram.

[0032] In a step-up DC-DC converter circuit, the smoothing capacitor 2 can be operated at an operating voltage equal to or higher than the DC bus voltage, so the energy that can be stored in the capacitor is greater than in a configuration using a step-down DC-DC converter circuit, and the characteristics of film capacitors, which have excellent high-voltage resistance, can be utilized.

[0033] In addition, since the DC bus is connected via a coupling reactor of the boost DC-DC converter, the charge / discharge current of the smoothing capacitor circuit to the DC bus does not flow as a switching pulse current, which significantly reduces the impact of the charge / discharge current caused by switching control on the surrounding environment.

[0034] The basic configuration of the control system of the present invention is a method for controlling the charge and discharge of smoothing capacitor 2, in which, under the DC voltage control of the DC voltage control power supply, the magnitude of the voltage ripple component of smoothing capacitor 1 or the quantity proportional to the current of smoothing capacitor 1 is used as the current reference quantity to control the charge and discharge current of smoothing capacitor 2, which is changed depending on the deviation from the reference voltage when controlling the average voltage of smoothing capacitor 2 to be constant, and the control issues are solved by PWM switching control of the boost DC-DC converter circuit by comparing and controlling the current reference quantity with the current flowing in the inductor that constitutes the boost DC-DC converter circuit.

[0035] Here, the activity Weapon When a smoothing capacitor is connected, the capacitance of the smoothing capacitor 1 used in combination can be made small enough so that it can be replaced with a film capacitor.

[0036] According to the present invention, the amount of current in the smoothing capacitor 1 can also be used as a control amount for reducing DC voltage pulsation without directly detecting the amount of DC voltage pulsation.

[0037] Here, the equivalent capacitor value can be easily changed by adjusting the magnitude of the voltage ripple component of smoothing capacitor 1 or the amount proportional to the current of smoothing capacitor 1 to the amount that controls the average voltage of smoothing capacitor 2 to a constant value.

[0038] On the other hand, if these proportional control variables for reducing DC voltage ripple are made too large, the average voltage of smoothing capacitor 2 cannot be controlled to a constant value. This problem is solved by adjusting the gain Kr of the control variable that compensates for the voltage ripple component in accordance with the deviation from the reference voltage when controlling the average voltage of smoothing capacitor 2 to a constant value.

[0039] Then, by PWM controlling the boost DC-DC converter by comparing this current reference amount with the current flowing through the inductor that makes up the boost DC-DC converter circuit, a control system is constructed that reduces DC voltage pulsation while controlling the instantaneous current amount, thereby solving the problem of being unable to control the voltage of smoothing capacitor 2.

[0040] It goes without saying that the bidirectional DC-DC converter is not limited to a boost DC-DC converter, and can be applied to any converter that can be expected to have a similar effect.

[0041] Figure 8 shows For reference, the bidirectional DC-DC converter is configured with an active capacitor circuit when a step-down DC-DC converter is used, as in Patent Document 2 and Patent Document 3, and the control system is that of the present invention.

[0042] In this case, As shown in the figure Since the current of a step-down DC-DC converter is a switching pulse current, when connecting a step-down DC-DC converter to a DC bus, it is necessary to connect it directly to the smoothing capacitor 1 before connecting it to reduce the impact on the surrounding circuits.

[0043] Also, As shown in Figure 7 In controlling the above current reference amount, it is also necessary to take measures such as using the current flowing through the inductor L2 of the step-down DC-DC converter circuit as the current detection amount for controlling the charging and discharging of the smoothing capacitor 2.

[0044] The PFC converter DC power supply according to the present invention shown in FIG. 7 is an example of the configuration of an active smoothing control DC power supply using a boost DC / DC converter circuit, and does not specify a DC voltage / current source. [Effects of the Invention]

[0045] The above main circuit configuration and control system Weapon By connecting the smoothing capacitors in parallel to the DC bus, DC voltage pulsation caused by power pulsation from the DC power supply side or the DC load circuit side on the DC bus can be suppressed, and smoothing capacitors 1 and 2 can be constructed using film capacitors without using large electrolytic capacitors.

[0046] The activity according to the present invention WeaponBy connecting a smoothing capacitor in parallel to the DC bus, DC voltage pulsation can be reduced with a capacitor of a relatively small capacitance instead of the large capacitance smoothing capacitor required to reduce DC voltage pulsation caused by large power pulsation when the DC voltage control power supply is configured with a PFC converter fed from a single-phase power supply.

[0047] In addition, the active Weapon By connecting a smoothing capacitor in parallel to the DC bus, DC voltage pulsation can be reduced with a capacitor of a relatively small capacitance instead of the large capacitance smoothing capacitor required to reduce DC voltage pulsation caused by large power pulsation when the DC load circuit is configured with a single-phase inverter circuit.

[0048] Furthermore, the active Weapon By connecting a smoothing capacitor in parallel to the DC bus, DC voltage pulsation can be reduced using a capacitor with a relatively small capacitance instead of the large capacitance smoothing capacitor required to reduce DC voltage pulsation even when large power pulsations from both the DC voltage controlled power supply and the DC load circuit are configured as a single-phase PFC converter circuit and a single-phase inverter circuit, respectively.

[0049] The present invention is Weapon We have proposed a control method that overcomes issues including the main circuit configuration for a bidirectional DC-DC converter that constitutes a capacitor, and the effects of the invention are described below, divided into the main circuit configuration and the control method.

[0050] From the viewpoint of the main circuit configuration, "Patent Document 2" , "Patent Document 3" Compared to the step-down DC / DC converter used in the past, the use of a step-up DC / DC converter allows for: 1) Since the operating voltage of the smoothing capacitor 2 can be made to be equal to or higher than the DC bus voltage, a high-voltage film capacitor with a large amount of stored energy can be used, thereby significantly increasing the capacity as a smoothing capacitor. 2) Active WeaponWhen connecting a capacitor to a DC bus, a step-down DC-DC converter generates a switching pulse current, whereas a step-up DC-DC converter generates a charge / discharge current via an inductance, resulting in a continuous current waveform that reduces the impact on peripheral devices.

[0051] Next, from the viewpoint of the control method, the control method of the present invention is different from the control method of "Patent Document 2". 1) PWM control is performed by comparing the instantaneous current between the charge / discharge current control reference and the actual current of the inductor of the bidirectional DC / DC converter, enabling stable control of the charge / discharge current. 2) A method of controlling by the sum of the operating voltage control amount of smoothing capacitor 2 and the voltage ripple suppression control amount in In order to adjust the magnitude of the voltage pulsation suppression control amount based on the deviation amount of the voltage control of the smoothing capacitor 2, function DC voltage ripple control can be applied stably without impairing the efficiency. 3) In addition to detecting the DC voltage ripple component, the current of the smoothing capacitor 1 can also be used without any problems as a control variable for reducing DC voltage ripple, and the detection circuit can be simplified compared to using an isolation amplifier for DC voltage detection. [Brief explanation of the drawings]

[0052] [Figure 1] Smoothing circuit operation of PFC converter (a) PFC converter, (b) operating waveform [Figure 2] Smoothing circuit operation when an inverter load is connected to a DC / DC converter. (a) DC / DC converter and inverter load, (b) operating waveforms [Figure 3] Smoothing circuit operation when an inverter load is connected to the PFC converter output: (a) PFC converter and inverter load, (b) operating waveforms [Figure 4] Smoothing capacitor circuit and active capacitor circuit (a) Smoothing capacitor circuit, (b) Active capacitor circuit [Figure 5]Comparison of operating waveforms between a smoothing capacitor circuit and an active capacitor circuit: (a) smoothing capacitor operating waveform, (b) active capacitor operating waveform [Figure 6] Basic configuration of the active smoothing control DC power supply of the present invention [Figure 7] System configuration of an active smoothing controlled DC power supply using a boost type DC / DC converter [Figure 8] System configuration of an active smoothing controlled DC power supply using a step-down DC / DC converter [Figure 9] Smooth operation waveform using electrolytic capacitor (Cd=100uF) [Figure 10] Operating waveforms of a step-down active smoothing control DC power supply (Cd=5uF, Cx=100uF, krv=1) [Figure 11] Operating waveforms of a step-down active smoothing control DC power supply (Cd=5uF, Cx=50uF, krv=1) [Figure 12] Operating waveforms of a boost-type active smoothing control DC power supply (Cd=5uF, Cx=25uF, Krv=5) [Figure 13] Smooth operation waveform using a large capacity electrolytic capacitor (Cd=500uF) [Figure 14] Operating waveforms of an active smoothing control DC power supply (Cd=5uF, Cx=20uF, Krv=5) [Figure 15] Operating waveforms of an active smoothing control DC power supply (Cd=5uF, Cx=50uF, Krv=5) [Figure 16] Operating waveforms of an active smoothing control DC power supply (Cd=5uF, Cx=25uF, Krv=1) [Figure 17] Operating waveforms when a single-phase inverter load (fb=50Hz) is connected to the PFC converter output (fa=60Hz) [Figure 18] Operating waveform when current detection of smoothing capacitor 1 is used as the control amount (Cd=5uF) DETAILED DESCRIPTION OF THE INVENTION

[0053] In order to verify the embodiment of the present invention, the main circuit configuration and control system shown in Figure 6 are used as the basis. Active smoothing control DC power supply Simulation analysis was performed on

[0054] The simulation analysis conditions are AC power supply voltage Ea=100V, frequency fa=60Hz, DC output reference voltage Edr=200V of the PFC converter, and DC load resistance R=100ohm. Weapon When a smoothing capacitor is connected, the capacitance of the smoothing capacitor 1 is set to Cd=5 uF.

[0055] The operating reference voltage of the smoothing capacitor 2 (Cx) when configured as a step-up DC / DC converter is Ecxr=300V, and when configured as a step-down DC / DC converter, Ecxr=140V.

[0056] The PFC converter's PWM switching frequency is f1 = 40 kHz, the inductor is L1 = 5 mH, the DCDC converter's PWM switching frequency is f2 = 40 kHz, and the inductor L2 is L2 = 0.1 mH for both the step-up and step-down types. (1) Smooth operation waveform of PFC converter using only electrolytic capacitor

[0057] Figure 9 shows the operating waveform when only an electrolytic capacitor with Cd = 100uF is connected as the smoothing capacitor 1. The PFC converter causes a nearly sinusoidal current iac to flow, and the pulsating component current of the pulsating current ids, which contains components twice the power supply frequency, flows into the current icd (high-frequency removal waveform) of the smoothing capacitor 1, thereby smoothing the DC voltage waveform. However, because the capacitance value is insufficient, some pulsation is seen in the DC voltage ed, and a pulsating current also flows in the DC load current idL. (2) Buck DC / DC converter control active Weapon Capacitor control characteristics

[0058] In contrast, FIG. 10 shows the active power supply of the present invention when the smoothing capacitor 1 is configured with a small value of Cd=5uF and a smoothing capacitor 2 with the same capacitance (Cx=100uF) as the step-down DC / DC converter, and the operating voltage of the smoothing capacitor 2 is set to Ecxr=140V and the DC ripple reduction control gain Kr=100. Weapon This is the operating waveform when a capacitor is connected.

[0059] From the figure, the pulsating component of the pulsating component current ids from the PFC converter is Weapon By passing the capacitor charge / discharge current icx, the DC voltage pulsation is significantly reduced and a sufficient filtering effect can be confirmed.

[0060] At this time, the average voltage ecx of the smoothing capacitor 2 is constant at the reference voltage Ecxr=140V, and the active Weapon It can be seen that the capacitor's charge / discharge current icx fluctuates greatly.

[0061] By charging and discharging the smoothing capacitor 2, the active Weapon The effect of active current control is that it allows the capacitor charge / discharge current icx to flow.

[0062] However, as shown in FIG. 11, when the capacitance value of the smoothing capacitor 2 is reduced to Cx=50 uF, the voltage of the smoothing capacitor 2 fluctuates greatly, and the active Weapon There will be a period when the charge / discharge current of the capacitor cannot be controlled. (3) Boost DC / DC converter control active Weapon Capacitor control characteristics

[0063] FIG. 12 shows the active power supply voltage of the present invention when a smoothing capacitor 2 having a smaller capacitance Cx=25 uF is used, the boost DC-DC converter is configured, the operating voltage of the smoothing capacitor 2 is set to Ecxr=300 V, and the DC ripple reduction control gain is set to Kr=500. Weapon The waveforms are those when a capacitor is connected, and the pulsating component of the pulsating component current ids from the PFC converter is actively Weapon This allows the capacitor's charge / discharge current icx to flow, significantly reducing DC voltage pulsation and providing a sufficient filtering effect.

[0064] This is because, as a step-up DC-DC converter is used, the operating voltage of smoothing capacitor 2 is higher than the voltage of the DC bus and is operated at Ecxr = 300V. Compared to the operating voltage Ecxr = 140V in the case of a step-down DC-DC converter, the energy that can be stored in the capacitor is proportional to the square of the voltage, so this is approximately 4.6 times larger. This means that a capacitor with a capacitance value that is approximately 20% smaller can be used, which is suitable when connecting a film capacitor to smoothing capacitor 2.

[0065] Figure 13 shows the active area when only an electrolytic capacitor with Cd=500uF is connected to the smoothing capacitor 1 of the PFC converter. Weapon It can be seen that the operating waveform is almost as smooth as that of the capacitor.

[0066] Figure 14 shows an active voltage regulator using a boost DC / DC converter. Weapon 10 shows the operating waveform when the capacitance of the smoothing capacitor 2 of the capacitor is further reduced, and it can be seen that the capacitance value at which the control limit operation is observed under these conditions is about Cx=20 uF.

[0067] From this, it can be seen that, depending on the set operating voltage of the smoothing capacitor 2, the capacitance of the smoothing capacitor 2 of an active capacitor using a boost type DCDC converter can be reduced to about one-twentieth.

[0068] Figure 15 shows an active voltage regulator using a boost DC / DC converter. Weapon This is the operating waveform when the capacitance of the smoothing capacitor 2 of the capacitor is further increased, and the operating voltage ecx of the smoothing capacitor 2 is the lowest voltage eecx = 250V and the DC voltage Ed=200V It can be seen that there is sufficient margin for

[0069] Figure 16 shows the activity WeaponThis is the operating waveform when the DC ripple reduction control gain is reduced to Kr=100 as the control amount of the capacitor. effect is suppressed hand , pulsating components are observed in the DC voltage So it will be like this Therefore, the DC ripple reduction control gain Kr must be set to an appropriate value. (4) Control characteristics when a single-phase inverter load is connected as a DC load

[0070] Figure 17 shows the active load when a single-phase inverter load is connected to a DC bus where the DC voltage control power supply is configured with a PFC converter, and the AC power supply frequency is fa = 60 Hz and the inverter operating frequency is fb = 50 Hz. Weapon 10 shows the operating waveform of the capacitor.

[0071] At this time, in order to reduce the DC voltage pulsation due to the current idL caused by the power pulsation from the DC load in addition to the current ids caused by the power pulsation from the DC power supply, an active Weapon A charge / discharge current that compensates for the component current of the difference between the two frequencies flows through the capacitor, and the operating voltage ecx of smoothing capacitor 2 also fluctuates greatly, but it can be confirmed that DC voltage pulsation is sufficiently suppressed and the capacitor is able to operate. (5) Control characteristics when the current of smoothing capacitor 1 is used as the control variable

[0072] The simulation results so far have shown that the active Weapon The control signal for the capacitor was a quantity proportional to the DC voltage ripple component. Figure 18 shows the operating waveform when the current icd flowing through the smoothing capacitor 1 is used, the switching component is removed, and the adjustment gain Kr is set to Kr=500.

[0073] Acty WeaponA sufficient filtering effect can be achieved without changing the basic operating waveform of the capacitor, and since the current ICD flowing through the smoothing capacitor 1 can be detected using a CT, as opposed to isolating it and detecting and calculating the DC voltage ripple, it is expected that a control system can be easily constructed. [Explanation of symbols]

[0074] 100…power supply 110...Single-phase AC power supply 120…DC power supply 200...Conversion device 210...PFC converter 200...DC-DC converter 300... DC voltage control power supply 400...Smoothing capacitor 1 410...Smoothing capacitor 1-2 500...Activity Weapon Capacita 510...PFC converter 520...DCDC converter 530...Smoothing capacitor 2 600…DC load 610...Single-phase inverter 620…AC circuit load 700...DC power supply control circuit 800...Activity Weapon Capacitor control circuit

Claims

[Claim 1] In a DC power supply circuit in which a DC load circuit is connected across a smoothing capacitor 1 connected to a DC output terminal of a DC voltage / current control power supply, A smoothing capacitor 2 is connected between DC side terminals of a half-bridge circuit configured by connecting in series two switch circuits, each of which has a semiconductor switch element and a diode connected in anti-parallel, an inductor is connected to the connection point of the two switch circuits, and the other end of the inductor and the negative end of the half-bridge circuit are connected to both ends of the smoothing capacitor 1, and a boost type DCDC converter circuit is connected. The voltage ripple component amount of the smoothing capacitor 1 or the amount proportional to the current of the smoothing capacitor 1 is adjusted by the deviation amount of the regulator of the smoothing capacitor 2, and the amount obtained by adding the adjusted amount to the control amount of the regulator that controls the average voltage of the smoothing capacitor 2 to a voltage reference value higher than the voltage of the DC output terminal is used as a current reference for controlling the charge / discharge current of the smoothing capacitor 2, and the step-up DC / DC converter circuit is PWM switched by instantaneous comparison control with the current of the inductor; An active smoothing control DC power supply that smooths the DC voltage of a DC voltage / current control power supply using an active capacitor, characterized by realizing a large equivalent capacitor by controlling the large charge / discharge of a capacitor with a small capacitance value at a voltage higher than the DC power supply voltage.

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