JP5385118B2 - Voltage compensation device and DC power supply system - Google Patents

Description

  The present invention relates to a DC power supply system that supplies electric power to a load in a direct current and a voltage compensation device that is used to compensate a load voltage in the DC power supply system.

  In recent years, with the increase in information communication devices used in information communication systems, the power consumed in information communication systems has also increased. For this reason, a DC power supply system that supplies power with direct current is attracting attention as a power supply system for efficiently supplying power to various information communication devices used in information communication systems. In particular, power is supplied at a high voltage of, for example, 400 V DC. The movement toward high efficiency is progressing with the high-voltage DC power supply system.

  In such a DC power supply system, a voltage compensator having a storage battery is provided as a backup when the DC voltage supplied from the power supply device to the load decreases for some reason, and this voltage is reduced when the DC voltage from the power supply device decreases. It is common to compensate the DC voltage to the load by the compensator (ie, this voltage compensator supplies the DC voltage to the load instead of the power supply).

The voltage compensator can be configured by simply connecting the storage battery between two positive and negative power supply lines that supply power from the power supply device to the load. However, depending on the storage battery voltage, sufficient DC power can be supplied to the load. The voltage may not be supplied. Therefore, a voltage compensator configured to provide a power converter that boosts or lowers the voltage of the storage battery in addition to the storage battery and compensates for the voltage drop of the storage battery by the power converter is known (for example, a patent) (See Reference 1.)
Patent Document 1 describes a technology in which a booster circuit that boosts the voltage of a backup battery is provided and the output voltage of the booster circuit is supplied between two power supply lines.

  By the way, as a direct current power supply system, there is known a high resistance grounding system in which two power supply lines from a power supply device to a load are grounded to a common grounding point through a resistor having a high resistance value. In such a DC power supply system in which each power supply line is grounded with a high resistance, the inside of the storage battery is generally grounded. Since the resistance value of each resistor in a high-resistance grounding DC power supply system is normally set to the same value, the ground point inside the storage battery is also set to the midpoint between the positive and negative electrodes of the storage battery. The

  Also in the high-resistance grounding type DC power supply system configured as described above, it is useful to provide a voltage compensator having a power converter in order to compensate for the voltage drop of the storage battery. As a specific method, for example, a method of providing a booster circuit that boosts the voltage of the storage battery can be considered, as in the technique described in Patent Document 1.

Japanese Patent Laid-Open No. 7-15888

  However, in the high-resistance grounding DC power supply system in which each power supply line is grounded via a resistor and the inside of the storage battery is also grounded as described above, it is described in Patent Document 1 in order to compensate for the voltage drop of the storage battery. If a method of providing a voltage compensation device composed of a booster circuit as described above is adopted, it is possible to compensate the DC voltage to the load, but it is not intended to the ground potential side through the respective resistors for grounding. Current (ground current) flows.

  That is, since the storage battery voltage is boosted by the booster circuit, the voltage between the ground point in the storage battery and the power supply line on the positive electrode side with respect to the voltage between the ground point (ground potential) in the storage battery and the power supply line on the negative electrode side. Is higher by the boosted voltage. Due to this voltage difference, the current flowing through the loop returning from the positive side of the voltage compensation device (that is, the positive side of the storage battery) to the ground point of the storage battery through the power supply line on the positive side and the grounding resistor connected thereto, The balance between the negative current side of the voltage compensator (ie, the negative side of the storage battery) and the current flowing through the loop returning to the ground point of the storage battery via the power supply line from the negative side and the grounding resistance connected to this is lost. An unintended ground current flows between the ground point of each resistor and the ground point of the storage battery.

  The present invention has been made in view of the above problems, and provides a direct current power supply system configured to supply power from a power supply device that outputs a direct current voltage to a load through two resistance-grounded positive and negative power supply lines. In a voltage compensator that is used to compensate the DC voltage to the load when the DC voltage from the power supply device decreases, it prevents the unintended ground current from flowing along with the operation of the voltage compensator. The purpose is to do.

  In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that the power from the power supply device that outputs a DC voltage is supplied to the positive and negative power supply lines that are grounded through resistors of the same resistance value. In a DC power supply system configured to be supplied to a load through a certain positive electrode power supply line and negative electrode power supply line, the DC power supply system is provided between the positive electrode power supply line and the negative electrode power supply line and is supplied from the power supply device to the load. The voltage compensator compensates the DC voltage for operating the load when the DC voltage is lower than a predetermined voltage value.

  The voltage compensator of the present invention (Claim 1) includes a storage battery in which a midpoint between the positive electrode and the negative electrode is grounded for supplying the compensation DC voltage to the load, and a compensation voltage generating means. I have.

  The compensation voltage generation means makes the potential of the positive-side power supply line higher by a predetermined positive-side compensation voltage than the potential of the positive electrode of the storage battery based on the voltage of the storage battery, and supplies the negative-side power based on the voltage of the storage battery The potential of the line is made lower than the potential of the negative electrode of the storage battery by a predetermined negative compensation voltage.

  The voltage compensator according to claim 1 configured as described above compensates for the DC voltage to the load, that is, from the voltage compensator to the load while the DC voltage is normally supplied from the power supply device to the load. The DC voltage is not supplied. Then, when the DC voltage from the power supply device to the load becomes lower than a predetermined voltage value for some reason, the DC voltage to the load is compensated. That is, the voltage compensation device supplies a DC voltage to the load instead of the power supply device.

  At this time, if the voltage of the storage battery is lower than the voltage required to operate the load, it is difficult to compensate the direct current voltage to the load by the storage battery, but since the compensation voltage generating means is provided, The voltage shortage of the storage battery can be compensated by this compensation voltage generating means. That is, a DC voltage higher than the voltage of the storage battery can be applied between the power supply lines and supplied to the load.

  In addition, the compensation voltage generating means makes the potential of only one of the power supply lines (for example, only the positive power supply line) different from the corresponding electrode (positive electrode in this example) in the storage battery (in this example) The positive-side power supply line is higher than the positive-electrode potential of the storage battery by the positive-side compensation voltage for both of the power supply lines. Therefore, the negative electrode side compensation voltage is made lower than the negative electrode potential of the storage battery.

  In other words, the compensation voltage generation means makes the voltage between the ground potential and the positive power supply line higher than the voltage between the ground potential and the positive electrode of the storage battery by the positive compensation voltage. The voltage between the negative power supply line and the ground potential also operates so as to be higher by the negative compensation voltage than the voltage between the negative electrode of the storage battery and the ground potential. That is, it operates so that both the ground potential and the potential difference between each power supply line become large.

  Therefore, according to the voltage compensation device of the first aspect, the operation of supplying a voltage higher than the voltage of the storage battery between the power supply lines by the compensation voltage generating means is performed between the ground potential and each power supply line. Since it can be realized by boosting the voltages in an appropriate balance, it is possible to prevent an unintended ground current from flowing.

  Here, the positive-side compensation voltage and the negative-side compensation voltage may be appropriately set to values within a range in which the DC voltage to the load can be compensated and the ground current can be suppressed. More specifically, for example, It may be set as described in claim 2.

That is, the invention described in claim 2 is the voltage compensator according to claim 1, wherein the compensation voltage generating means sets the positive side compensation voltage and the negative side compensation voltage to the same voltage value.
According to the voltage compensator according to claim 2 configured as described above, the voltage between the ground potential and the positive power supply line and the voltage between the ground potential and the negative power supply line have the same voltage value. Therefore, it is possible to reliably prevent an unintended ground current from flowing.

  By the way, if the positive side compensation voltage and the negative side compensation voltage are set as described in claim 2, at least theoretically, an unintended ground current can be prevented. However, in reality, each compensation voltage is simply set to the same voltage value due to various factors such as voltage variations in the storage battery, tolerance of resistance values of each resistance, various circuit constants existing between the voltage compensation device and each resistance, etc. There is a possibility that the ground current cannot be effectively prevented only by setting to.

Therefore, in order to more surely prevent an unintended ground current, for example, a voltage compensation device may be configured as described in claim 3.
That is, the invention according to claim 3 is the voltage compensator according to claim 1 or 2, wherein the ground current detecting means for detecting the ground current flowing from the storage battery to the ground potential side through each resistor is provided. I have. The compensation voltage generation means individually sets the positive-side compensation voltage and the negative-side compensation voltage so that the ground current detected by the ground-current detection means is not more than a predetermined current value.

  In other words, in order to reliably achieve the purpose of preventing the ground current, the ground current is actually detected, and the voltage value of each compensation voltage is individually set so that the detected value is not more than a predetermined current value. is there. The predetermined current value can be set as appropriate, and may be set to 0, for example.

  Various specific methods of individual setting are conceivable. For example, if a ground current flows in a direction from the ground potential side to the ground point in the storage battery, the positive compensation voltage is lowered or the negative compensation voltage is set to be lower. By making it higher, the ground current can be reduced or prevented. Also, for example, if a ground current flows in a direction from the ground point in the storage battery toward the ground potential side, the ground current is reduced by lowering the negative side compensation voltage or raising the positive side compensation voltage. -It can be prevented.

  Therefore, according to the voltage compensation device of the third aspect, since the voltage value of each compensation voltage is set so that the ground current is actually detected and the detected value is equal to or less than the predetermined current value, it is not intended. It becomes possible to more reliably prevent the ground current from flowing.

  Next, the invention according to claim 4 is the voltage compensation device according to any one of claims 1 to 3, wherein the compensation voltage generation means includes the positive power conversion means and the negative power conversion. Means. The positive-side power conversion means is provided between the storage battery and the positive-side power supply line, and generates and outputs a positive-side compensation voltage based on the input voltage of the storage battery. The negative electrode side power conversion means is provided between the storage battery and the negative electrode side power supply line, and generates and outputs a negative electrode side compensation voltage based on the input voltage of the storage battery.

  Thus, by providing the power conversion means for each compensation voltage in order to generate each compensation voltage, the resistance (internal resistance in the voltage compensation device) viewed from each power supply line to the voltage compensation device is also properly balanced. It becomes. That is, for example, if power converters having the same configuration are provided, the internal resistance of the voltage compensator viewed from each power supply line can be set to the same value. Therefore, the effect of preventing ground current can be further enhanced.

  Here, various specific configurations of each power conversion means are conceivable, and for example, an insulation type configuration in which the input side and the output side are insulated by a transformer may be used. At least one of the conversion means and the negative electrode side power conversion means may be configured as a non-insulated type in which the input side and the output side are not insulated.

  If the power conversion means is configured as a non-insulated type, the number of components constituting the power conversion means can be reduced compared to the case where the power conversion means is configured as an insulating type, for example, by eliminating the need for an insulation transformer. As a result, the power conversion means can be reduced in size and efficiency.

  When at least one of the power conversion units is configured as a non-insulated type as described above, for example, as described in claim 6, both the positive side power conversion unit and the negative side power conversion unit are provided. The step-up / step-down chopper circuit may be configured such that the input voltage can be stepped up or stepped down and a voltage in which the positive / negative polarity is inverted with respect to the input voltage is output.

  If a step-up / step-down chopper is used as each power converter for generating each compensation voltage, the storage battery voltage can be boosted or stepped down, so that each compensation voltage can be generated appropriately and reliably according to fluctuations in the storage battery voltage. Moreover, since the step-up / step-down chopper has a configuration in which the polarities of the input and output are reversed, it is easily provided both between the positive electrode and the positive power supply line of the storage battery and between the negative electrode and the negative power supply line of the storage battery. Can do.

  Next, the invention according to claim 7 is the voltage compensator according to any one of claims 4 to 6, wherein the positive-side power conversion means and the negative-side power conversion means are of a switching type. A corresponding compensation voltage is generated by turning on / off each switching element, which is configured by a power conversion circuit, according to drive signals having a phase difference from each other.

  Since the switching type power conversion circuit is configured to perform power conversion by controlling on / off of the switching element, the output voltage includes a ripple. Therefore, for example, when the switching elements of both the positive-side power conversion means and the negative-side power conversion means are turned on / off at the same timing, a ripple change also occurs at the same timing, and as a result, the voltage compensation device outputs the load to the load. The DC voltage includes a large ripple obtained by adding ripples generated by each power conversion means. Moreover, the peak value of the current discharged from the storage battery also increases.

  This ripple can be reduced to some extent by the output smoothing filter normally provided in the power conversion circuit. However, if the reduction effect is increased, the size of the filter is increased.

  Therefore, in the voltage compensation device according to the seventh aspect, the switching elements in the power conversion units are not turned on / off at the same timing, but are turned on / off according to drive signals having a phase difference.

  With such a configuration, the phase of the ripple included in each compensation voltage output from each power conversion means also shifts, so that the ripple of the entire DC voltage output from the voltage compensation device to the load can be reduced. . Therefore, the output smoothing filter in each power conversion means can be reduced in size, and the cost can be reduced. In addition, since the peak value of the current discharged from the storage battery can be reduced, the life of the storage battery is extended and the reliability thereof is improved.

  Next, according to an eighth aspect of the present invention, there is provided a positive power supply line, which is a positive / negative power supply line grounded via a resistor having the same resistance value, respectively, from the power supply device that outputs a DC voltage. And a negative power supply line configured to supply power to a load between the positive power supply line and the negative power supply line according to any one of claims 1 to 7. The described voltage compensation device is provided.

  According to the DC power supply system configured as described above, when the DC voltage from the power supply device is reduced for some reason, the DC voltage supply to the load is compensated by the voltage compensator. Moreover, since the voltage compensation device according to any one of claims 1 to 7 is used as the voltage compensation device, the same effects as those of the above-described claims can be obtained.

It is a lineblock diagram showing a schematic structure of a direct-current power supply system of a 1st embodiment. It is a block diagram showing schematic structure of the voltage compensation apparatus of 1st Embodiment. It is explanatory drawing for demonstrating operation | movement of the voltage compensation apparatus of 1st Embodiment. It is explanatory drawing for demonstrating operation | movement of the voltage compensation apparatus of 1st Embodiment. It is a block diagram showing schematic structure of the voltage compensation apparatus of 2nd Embodiment. It is a block diagram showing the modification of a voltage compensation apparatus. It is a block diagram showing the modification of a voltage compensation apparatus.

Preferred embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 shows a schematic configuration of the DC power supply system of the present embodiment. As shown in FIG. 1, the DC power supply system 1 of the present embodiment is a system configured to supply power to a load 3 with DC, and mainly uses a three-phase AC voltage input from the outside as a predetermined value. A rectifying device 2 that converts and outputs a DC voltage (400 V in this example), and a positive-side power supply line 6 and a negative-side power supply line 7 for supplying the DC voltage output from the rectifying device 2 to the load 3. And a voltage compensator 5 that compensates the DC voltage for operating the load 3 when the DC voltage supplied from the rectifier 2 to the load 3 becomes lower than a predetermined voltage value.

  Between each of the power supply lines 6 and 7, two resistors (hereinafter also referred to as “high resistance”) R1 and R2 having a large resistance value (several tens of kΩ in this example) are connected in series. Each of the high resistances R1 and R2 has the same resistance value, and the middle point thereof, that is, the connection point of the high resistances R1 and R2 is grounded.

  That is, the DC power supply system 1 of the present embodiment is configured as a high resistance grounding / midpoint grounding system in which the power supply lines 6 and 7 are grounded via the high resistances R1 and R2, respectively. Therefore, when a DC voltage of 400 V is output from the rectifier 2, the potential of the positive power supply line 6 with respect to the ground potential is 200 V, and the potential of the negative power supply line 7 with respect to the ground potential is -200 V.

  A voltage compensation device 5 is provided between the power supply lines 6 and 7. The voltage compensation device 5 includes a storage battery 10 having a predetermined rated voltage (380 V in this example) with a midpoint between the positive electrode and the negative electrode grounded, and a positive electrode side of the storage battery 10, more specifically, a positive electrode of the storage battery 10. A high-side power converter 11 connected between the positive-side power supply line 6 and the negative-side of the storage battery 10, more specifically, a low-side power converter connected between the negative-electrode of the storage battery 10 and the negative-side power supply line 7. 12 and a control unit 13 that controls the operation of each of the power converters 11 and 12. That is, the voltage compensation device 5 has a configuration in which the power converters 11 and 12 are symmetrically connected to the positive electrode side and the negative electrode side of the storage battery 10, respectively.

  The high-side power converter 11 connected to the positive electrode side of the storage battery 10 includes a diode D1 having an anode connected to the positive electrode of the storage battery 10 and a cathode connected to the positive power supply line 6 via the positive electrode output terminal 8. Based on the voltage Vb of the storage battery 10 (hereinafter referred to as “storage battery voltage”), the high-side step-up / step-down voltage for making the voltage of the positive-side power supply line 6 higher than the potential of the positive electrode of the storage battery 10 by a predetermined high-side compensation voltage VoutH A chopper 14 is provided.

The high-side buck-boost chopper 14 generates a high-side compensation voltage VoutH by boosting or stepping down the input storage battery voltage Vb and outputs it to both ends of the diode D1.
The low-side power converter 12 connected to the negative electrode side of the storage battery 10 includes a diode D2 having a cathode connected to the negative electrode of the storage battery 10 and an anode connected to the negative power supply line 7 via the negative electrode output terminal 9, A low-side buck-boost chopper 15 for lowering the voltage of the negative-side power supply line 7 by a predetermined low-side compensation voltage VoutL from the negative-electrode potential of the storage battery 10 based on the voltage Vb is provided.

  The low-side buck-boost chopper 15 generates a low-side compensation voltage VoutL by boosting or stepping down the input storage battery voltage Vb and outputs it to both ends of the diode D2. The diode D1 and the diode D2 have the same electrical characteristics.

  In this embodiment, the high-side compensation voltage VoutH output from the high-side buck-boost chopper 14 and the low-side compensation voltage VoutL output from the low-side buck-boost chopper 15 have the same voltage value.

  Based on the storage battery voltage Vb, the control unit 13 outputs a high-side compensation voltage VoutH and a low-side compensation voltage VoutL with appropriate voltage values corresponding to the storage battery voltage Vb from the high-side buck-boost chopper 14 and the low-side buck-boost chopper 15, respectively. Thus, the operation of each step-up / down chopper 14 or 15 is controlled.

  The appropriate voltage value here is a constant voltage value required for operating the load 3 by the DC voltage output from the voltage compensator 5 to the load 3 via the power supply lines 6 and 7 (this example). In this case, the voltage value is 380V).

  Therefore, if the storage battery voltage Vb itself is 380 V, a sufficient DC voltage can be supplied to the load 3 only by the storage battery 10, and therefore the control unit 13 does not operate the step-up / step-down choppers 14 and 15. Note that the voltage drop due to each of the diodes D1 and D2 is ignored here.

  On the other hand, when the storage battery voltage Vb decreases and the storage battery 10 alone cannot supply a sufficient DC voltage to the load 3, the control unit 13 operates the step-up / step-down choppers 14 and 15 so that the compensation voltages VoutH and VoutL. Is output. As a result, the voltage compensation device 5 outputs a voltage value (380 V) obtained by summing the storage battery voltage Vb, the low-side compensation voltage VoutL, and the high-side compensation voltage VoutH to the load 3.

  In the DC power supply system 1 configured as described above, the voltage compensating device 5 is provided for backup when the DC voltage from the rectifying device 2 is reduced or cut off. Therefore, when the DC voltage is normally supplied from the rectifier 2 to the load 3, power supply from the voltage compensator 5 to the load 3 is not performed.

  On the other hand, if the input of the three-phase AC voltage to the rectifier 2 is interrupted due to, for example, a power failure or the DC voltage from the rectifier 2 to the load 3 is reduced or cut off due to a failure of the rectifier 2, etc. The backup operation by the device 5 is performed, and the DC voltage to the load 3 is continuously maintained at a normal value (a value at which the load 3 can operate). That is, the voltage compensation device 5 supplies all the power to the load 3.

  Specifically, when the DC voltage supplied from the rectifier 2 to the load 3 is lower than a predetermined voltage value, that is, when the DC voltage is lower than the storage battery voltage Vb, the DC voltage from the rectifier 2 and the storage battery voltage Vb. Is reversed, the discharge from the storage battery 10 (output to the load 3) starts.

  At this time, if the storage battery voltage Vb itself is 380 V, the step-up / step-down choppers 14 and 15 do not operate as described above, and the storage battery voltage Vb is output to the load 3 through the diodes D1 and D2. On the other hand, when the storage battery voltage Vb is lower than 380 V and only the storage battery 10 cannot supply a sufficient DC voltage to the load 3, the step-up / step-down choppers 14 and 15 operate to compensate for the decrease in the storage battery voltage Vb.

  By the way, in the present embodiment, as described above, the high side compensation voltage VoutH and the low side compensation voltage VoutL are set to the same value, but this is from the storage battery 10 via the high resistances R1 and R2 to the ground potential side. This is to prevent a ground current from flowing into the circuit.

  If the high-side compensation voltage VoutH and the low-side compensation voltage VoutL are set to different values, since the middle point of the storage battery 10 is grounded, the voltage between the ground point and the positive power supply line 6 is The voltage between the ground point and the negative power supply line 7 has a different voltage value. In contrast, the high resistances R1 and R2 have the same resistance value as described above.

  Therefore, the voltage compensation device 5 returns from the positive electrode side (positive electrode output terminal 8) to the ground point in the storage battery 10 via the positive electrode side power supply line 6, the high resistance R1 connected thereto, and the ground line (not shown). The current flowing through the loop and the negative side (negative output terminal 9) of the voltage compensation device 5 returns to the ground point in the storage battery 10 via the negative side power supply line 7, the high resistance R2 connected thereto, and the ground line. The balance with the current flowing through the loop is lost, and as a result, an unintended ground current flows through the ground line between the ground point of each of the high resistances R1 and R2 and the ground point of the storage battery 10.

  Therefore, in this embodiment, in order to prevent such an unintended ground current from flowing, the high side compensation voltage VoutH and the low side compensation voltage VoutL are set to the same voltage value, and the ground potential and the power supply lines 6 and 7 are connected. The voltage is made equal. Thus, the ground current is prevented by uniformly controlling the output voltages from the step-up / step-down choppers 14 and 15.

  In the present embodiment, the storage battery 10 is charged not by floating charging but by the charging device 4 provided separately. The charging device 4 generates a charging voltage for charging from an externally input three-phase AC voltage, outputs the charging voltage to the storage battery 10, and charges the storage battery 10. However, the configuration in which the storage battery 10 is charged by the charging device 4 is merely an example, and the charging method of the storage battery 10 is not particularly limited.

  Next, the configurations of the step-up / step-down choppers 14 and 15 and the control unit 13 constituting the voltage compensation device 5 will be described with reference to FIG. FIG. 2 is a configuration diagram showing a schematic configuration of the voltage compensation device 5, and particularly shows a more specific configuration of each of the step-up / step-down choppers 14, 15 and the control unit 13.

  As shown in FIG. 2, the high-side buck-boost chopper 14 is a non-insulated power converter whose input and output are not insulated, and has a reactor L1 whose one end is connected to the positive electrode of the storage battery 10 and a drain that is a reactor. A MOSFET 16 (hereinafter referred to as “high-side switch”) having a source connected to the other end of L1 and a source connected to the negative electrode of the storage battery 10 via a diode D17 in the low-side buck-boost chopper 15, and one end connected to one end of the reactor L1 The connected capacitor C1, the diode D11 whose anode is connected to the other end of the reactor L1 and the cathode is connected to the other end of the capacitor C1, and the anode is connected to the other end of the capacitor C1 and the cathode is the cathode of the diode D1. And a diode D12 connected to the positive output terminal 8 (that is, connected to the positive output terminal 8). The high side drive signal SP1 from the control unit 13 is input to the gate of the high side switch 16. The circuit including the reactor L1 and the capacitor C1 also functions as an output smoothing filter for reducing the ripple of the output voltage (high side compensation voltage VoutH).

  The high-side buck-boost chopper 14 configured as described above is configured such that the input storage battery voltage Vb is changed to the high-side compensation voltage VoutH by turning on / off the high-side switch 16 by the high-side drive signal SP1 from the control unit 13. Is converted to The principle that the high-side compensation voltage VoutH is generated by the switching of the high-side switch 16 is basically the same as that of a generally well-known step-up / step-down chopper circuit, and therefore description thereof is omitted here (to be described next). The same applies to the low-side buck-boost chopper 15).

  The low-side buck-boost chopper 15 is also a non-insulated power converter in which the input and output are not insulated, and a MOSFET (hereinafter referred to as “low-side switch”) 17 whose drain is connected to the positive electrode of the storage battery 10 and one end of which is low-side. A reactor L2 connected to the source of the switch 17, a capacitor C2 having one end connected to the other end of the reactor L2 and the other end connected to the anode of the diode D2 (that is, connected to the negative output terminal 9), and the anode being a capacitor A diode D16 connected to the other end of C2 and having a cathode connected to the source of the low-side switch 17 and a diode D17 having an anode connected to the connection point of the reactor L2 and the capacitor C2 and a cathode connected to the negative electrode of the storage battery 10 It is prepared. The low-side drive signal SP <b> 2 from the control unit 13 is input to the gate of the low-side switch 17. The circuit composed of the reactor L2 and the capacitor C2 also functions as an output smoothing filter for reducing the ripple of the output voltage (low side compensation voltage VoutL).

  In the low-side buck-boost chopper 15 configured in this way, the input storage battery voltage Vb is converted to the low-side compensation voltage VoutL when the low-side switch 17 is turned on / off by the low-side drive signal SP2 from the control unit 13. .

  The step-up / down chopper generally has a property that the polarity of the output is inverted with respect to the input. Therefore, in this embodiment, as each power converter 11 and 12 provided in the positive electrode side and the negative electrode side of the storage battery 10, the electric potential of the positive electrode side power supply line 6 is made with respect to the positive electrode of the storage battery 10 by using a buck-boost chopper. Both raising and lowering the potential of the negative-side power supply line 7 with respect to the negative electrode of the storage battery 10 are easily realized.

  The control unit 13 includes a voltage detection unit 13a that detects the storage battery voltage Vb, a drive duty and drive timing for driving the high-side switch 16 based on the storage battery voltage Vb detected by the voltage detection unit 13a, and a low side A microcomputer 13b that calculates a driving duty and driving timing for driving the switch 17 and outputs a driving command indicating the calculation result, and a high-side driving for driving the high-side switch 16 based on the driving command from the microcomputer 13b And a drive unit 13c that generates and outputs a signal SP1 and a low-side drive signal SP2 for driving the low-side switch 17.

  Each drive signal SP1, SP2 is a pulse signal having a predetermined duty ratio for turning on / off the corresponding switch 16, 17, and the corresponding switch is turned on when it is at a high level and turned off when it is at a low level. To do. The drive duty of each drive signal SP1, SP2 is determined according to the values of the high side compensation voltage VoutH and the low side compensation voltage VoutL to be generated.

  On the other hand, the output timings of the drive signals SP1 and SP2 are not the same, and are output with a phase difference. An example is shown in FIGS. Note that the waveforms of the high-side switch and the low-side switch (changes between ON and OFF) in FIGS. 3 and 4 can be regarded as high-low changes in the corresponding drive signals as they are.

  FIG. 3 shows an example in which the drive duty of each of the drive signals SP1 and SP2 is 50%. Since the drive duty is 50%, the switches 16 and 17 have the same on period and off period. The high side compensation voltage VoutH decreases when the high side switch 16 is turned on and increases when the high side switch 16 is turned off. That is, the high side compensation voltage VoutH is a voltage including a ripple. The same applies to the low-side compensation voltage VoutL.

  For this reason, if the high-side switch 16 and the low-side switch 17 are turned on / off at the same timing, the fluctuation patterns of the compensation voltages VoutH and VoutL are the same, so that the amount of ripple increases additively. Moreover, the peak value of the current discharged from the storage battery 10 also increases.

  Therefore, in the present embodiment, the drive signals SP1 and SP2 have a phase difference (180 degrees in this example), and during the period when the high-side switch 16 is on and the high-side compensation voltage VoutH decreases, the low-side switch 17 Is turned off so that the low side compensation voltage VoutL is increased. On the other hand, during the period when the high side switch 16 is off and the high side compensation voltage VoutH is increased, the low side switch 17 is turned on and the low side compensation voltage VoutL is decreased. I am doing so. In addition, when the drive duty is 50%, the phase difference of 180 degrees means that, in other words, as shown in FIG. 3, the signal obtained by inverting the logic of one drive signal is directly applied to the other. It can be used as a drive signal.

  In this way, by shifting the phases of the drive signals SP1 and SP2 by 180 degrees, the ripple of the high-side compensation voltage VoutH and the ripple of the low-side compensation voltage VoutL cancel each other, and as a result, the voltage compensator 5 to the load 3 A DC voltage (load voltage VL) with reduced ripple is supplied. Moreover, the peak value of the current discharged from the storage battery 10 can also be suppressed.

  FIG. 4 shows an example in which the drive duty of each of the drive signals SP1 and SP2 is 70% and has a phase difference of 180 degrees from each other. In this case as well, there is a difference between the on / off timing of the high-side switch 16 and the on / off timing of the low-side switch 17, so that the ripple of the DC voltage output to the load 3 is reduced and the peak value of the current discharged from the storage battery 10 is reduced. The effect that it can suppress is acquired.

  In each of the examples of FIGS. 3 and 4, the phase difference between the drive signals SP1 and SP2 is set to 180 degrees. However, this is only an example. It can be determined as appropriate.

  As described above, in the DC power supply system 1 of the high resistance grounding system / midpoint grounding system of the present embodiment, as the voltage compensating device 5 for backup when the DC voltage from the rectifying device 2 to the load 3 is reduced, A storage battery 10 whose middle point is grounded is used, and a power conversion device including a step-up / step-down chopper is connected to both the positive electrode side and the negative electrode side of the storage battery 10.

  When the storage battery voltage Vb is normal, the step-up / step-down choppers 14 and 15 do not operate and a DC voltage is supplied from the storage battery 10 to the load 3. At this time, since the power converters are symmetrically arranged on both the positive electrode side and the negative electrode side of the storage battery 10, the voltage between the ground point of the storage battery 10 and each of the power supply lines 6 and 7 is uniform, and the ground current is It is surely prevented.

  On the other hand, when the output voltage from each step-up / step-down chopper 14 or 15 compensates for the decrease due to the decrease in the storage battery voltage Vb, each step-up / step-down chopper 14 or 15 receives a voltage of the same voltage value (high side compensation voltage VoutH , Low side compensation voltage VoutL) is output. Therefore, also in this case, the voltage between the ground point of the storage battery 10 and each of the power supply lines 6 and 7 becomes uniform, and the ground current is reliably prevented.

  Each of the power converters 11 and 12 is composed of a non-insulated power converter (specifically, a high-side buck-boost chopper 14 and a low-side buck-boost chopper 15). Therefore, compared with the case where it comprises with an insulation type power converter, the number of parts which comprise a power converter can be reduced, for example, the transformer for insulation is unnecessary. Thus, the power converter can be reduced in size and efficiency.

  As described with reference to FIGS. 3 and 4, the switching of the step-up / step-down choppers 14 and 15 is performed according to the drive pulses SP <b> 1 and SP <b> 2 having a phase difference from each other, so that the voltage compensation device 5 outputs to the load 3. It is possible to reduce the ripple of the entire DC voltage. Therefore, the output smoothing filter in each of the step-up / step-down choppers 14 and 15 can be reduced in size, and the cost can be reduced. Moreover, since the peak value of the current discharged from the storage battery 10 can also be reduced, the life of the storage battery 10 is extended and the reliability thereof is improved.

  In the present embodiment, the high side compensation voltage VoutH corresponds to the positive side compensation voltage of the present invention, and the low side compensation voltage VoutL corresponds to the negative side compensation voltage of the present invention. The high-side power converter 11 corresponds to the positive-side power conversion unit of the present invention, and the low-side power converter 12 corresponds to the negative-side power conversion unit of the present invention.

[Second Embodiment]
Next, the voltage compensation device of the second embodiment will be described with reference to FIG. As shown in FIG. 5, the voltage compensation device 20 of the present embodiment is different from the voltage compensation device 5 of the first embodiment (see FIGS. 1 and 2) between the midpoint of the storage battery 10 and the ground potential. The high-side switch of the high-side buck-boost chopper 14 is controlled by the control unit 21 based on the fact that the current detection resistor R3 for detecting the ground current is connected and the ground current detected using the current detection resistor R3. 16 and the low-side switch 17 of the low-side step-up / down chopper 15 are individually controlled. Since other configurations are the same as those of the voltage compensation device 5 of the first embodiment, the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

  In the voltage compensation device 20 of the present embodiment, the voltage at the connection point between the current detection resistor R3 and the middle point of the storage battery 10 is input to the current detection unit 21a in the control unit 21. The voltage input to the current detector 21a is a value corresponding to the ground current. Therefore, the current detection unit 21a detects the ground current based on the voltage input from the current detection resistor R3. Then, data (ground current detection data) indicating the value of the detected ground current is output to the microcomputer 21b.

  Based on the input ground current detection data, the microcomputer 21b individually controls the switches 16 and 17 so that the ground current becomes a predetermined current value or less. That is, the high-side compensation voltage VoutH from the high-side buck-boost chopper 15 and the low-side compensation voltage VoutL from the low-side buck-boost chopper 15 are not set to the same voltage value as in the first embodiment, but the ground current is a predetermined current. It is set individually so that it is less than the value. The predetermined current value can be determined as appropriate and may be zero.

  As a specific method of the individual setting, for example, if a ground current flows in a direction from the ground potential side toward the ground point in the storage battery 10, the high side compensation voltage VoutH is set lower or the low side compensation voltage VoutL is set. By making it higher, the ground current can be reduced or prevented. On the contrary, if the ground current flows in the direction from the ground point in the storage battery 10 toward the ground potential side, the ground current can be reduced by lowering the low side compensation voltage VoutL or increasing the high side compensation voltage VoutH. Can be reduced or prevented.

  Although each compensation voltage may be set individually from the beginning, for example, each compensation voltage is initially set to the same voltage value as in the first embodiment, and is detected at that time. Based on the value of the ground current, thereafter, either one or both of the compensation voltages may be set individually as appropriate.

  According to the voltage compensation device 20 of the present embodiment configured as described above, each compensation voltage is simply set to the same voltage due to various factors such as variations in the voltage of the storage battery 10 and tolerances of the resistance values of the high resistances R1 and R2. Even when the ground current cannot be effectively prevented only by setting the value, the ground current can be more reliably prevented.

[Modification]
Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments, and can take various forms as long as they belong to the technical scope of the present invention. Needless to say.

  For example, in the above-described embodiment, the power converters 11 and 12 provided on both the positive electrode side and the negative electrode side of the storage battery 10 in the voltage compensation device are shown as being configured by the step-up / step-down chopper. The configuration of the chopper is merely an example.

  For example, when both are configured by a chopper, the high-side power converter 11 can also be configured by a boost chopper. An example of a voltage compensation device in which the high-side power converter 11 is configured by a boost chopper is shown in FIG.

  A voltage compensation device 30 shown in FIG. 6 is obtained by replacing the high-side buck-boost chopper 14 with a high-side boost chopper 31 in the voltage compensation device 5 (see FIGS. 1 and 2) of the first embodiment.

  As shown in FIG. 6, the high-side boost chopper 31 includes a reactor L21 having one end connected to the positive electrode of the storage battery 10, and a drain connected to the other end of the reactor L2 and a source connected to the diode D17 in the low-side buck-boost chopper 15. A MOSFET (high side switch) 33 connected to the anode, a diode D31 whose anode is connected to the drain of the high side switch 33, one end connected to the cathode of the diode D31, and the other end connected to the source of the high side switch And a diode D32 having an anode connected to the cathode of the diode D31 and a cathode connected to the cathode of the diode D1 (that is, connected to the positive output terminal 8).

  The high-side drive signal SP1 from the control unit 32 is input to the gate of the high-side switch 33. The circuit composed of the reactor L21 and the capacitor C21 also functions as an output smoothing filter for reducing the ripple of the output voltage (high side compensation voltage VoutH).

  The high-side boost chopper 31 configured as described above generates a DC voltage higher than the input storage battery voltage Vb by turning on and off the high-side switch 33 by the high-side drive signal SP1 from the control unit 32. Is done. The generated DC voltage is applied between the negative electrode of the storage battery 10 and the cathode of the diode D1.

  Therefore, if the high-side boost chopper 31 is controlled such that the output voltage from the high-side boost chopper 31 is higher than the storage battery voltage Vb by the high-side compensation voltage VoutH, as a result, the positive-side power supply line 6 can be made higher than the potential of the positive electrode of the storage battery 10 by the high-side compensation voltage VoutH, and the voltage compensation device 30 having a function equivalent to that of each of the above embodiments is realized.

  In the description so far, the case where each power converter constituting the voltage compensator is configured by a non-insulated power converter is shown, but an example of using a non-insulated power converter is also an example. However, an insulated power converter may be used. FIG. 7 shows an example of a voltage compensator in which each power converter is constituted by an insulated power converter.

  The voltage compensator 40 shown in FIG. 7 receives the voltage (storage battery voltage Vb) of the storage battery 10 and temporarily converts the storage battery voltage Vb into alternating current, and a high voltage provided on the positive electrode side of the storage battery 10. A side output side converter 42 and a low side output side converter 43 provided on the negative electrode side of the storage battery 10 are provided. Each of these converters 41, 42, 43 constitutes one insulated power converter as a whole.

  The diodes D1 and D12 connected to the positive electrode of the storage battery 10 and the diodes D2 and D17 connected to the negative electrode of the storage battery 10 are similarly connected to the storage battery 10 in the voltage compensator 5 of the first embodiment. It was what it was. Therefore, the same reference numerals as those in the first embodiment are given.

  As shown in the figure, the input side converter 41 is a well-known full-bridge type power conversion circuit (self-excited voltage type inverter) including four switching elements (MOSFETs) 51, 52, 53, and 54. AC voltage is supplied to the primary winding L11. Each diode D21, D22, D23, D24 connected in parallel between the drain and source of each switching element 51, 52, 53, 54 is a known flyback diode. The capacitor C11 connected in parallel to the input side of the input side converter 41 is for stabilizing the input voltage.

  The transformer 45 has a configuration in which the secondary side is divided into two, a first secondary winding L12 and a second secondary winding L13, and the number of turns of each secondary winding L12, L13 is the same. is there. Therefore, an alternating voltage corresponding to the ratio between the number of turns of the primary winding L11 and the number of turns of each secondary winding L12, L13 is generated in each secondary winding L12, L13. By this transformer 45, the input side and the output side are insulated.

  The high-side output side converter 42 is a rectifying / smoothing circuit including a diode D26, a reactor L14, and a capacitor C12 for smoothing the AC voltage induced in the first secondary winding L12 and converting it to a DC voltage. It has.

  Similarly, the low-side output side converter 43 smoothes and converts the AC voltage induced in the second secondary winding L13 into a DC voltage, and is a rectifying / smoothing composed of a diode D28, a reactor L15, and a capacitor C13. Circuit.

The high-side output side converter 42 and the low-side output side converter 43 both output a DC voltage having the same voltage value.
Therefore, the ground current can be prevented also by the voltage compensator 40 having the insulation type power converter as shown in FIG. 7, similarly to the voltage compensator 5 of the first embodiment.

  In the DC power supply system of the above embodiment, when the DC voltage from the rectifying device 2 decreases and becomes lower than the storage battery voltage Vb, the DC voltage is naturally output from the storage battery 10 to the load 3 due to the voltage difference. However, this is merely an example. For example, the storage battery 10 and the power supply lines 6 and 7 are shut off by a switch or the like, and the DC voltage from the rectifier 2 is less than or equal to a predetermined threshold value. At this time, a switch or the like may be turned on to output a DC voltage from the storage battery 10 to the load 3.

  Moreover, in the said embodiment, when the storage battery voltage Vb became lower than 380V and it became the state which cannot supply sufficient DC voltage to the load 3 only by the storage battery 10, each buck-boost chopper 14 and 15 demonstrated as what operate | moves. However, regardless of the magnitude of the storage battery voltage Vb, as soon as the output of the DC voltage from the voltage compensator to the load 3 is started, the step-up / step-down choppers 14 and 15 are operated, and the voltage value higher than the storage battery voltage Vb. The direct current voltage may be output to the load 3.

  In the above embodiment, the DC voltage for load operation is generated by converting the three-phase AC voltage into DC by the rectifier 2. However, such a configuration is merely an example, and the DC voltage is applied to the load 3. The configuration on the power source side for supply (excluding the voltage compensation device) is not particularly limited.

  DESCRIPTION OF SYMBOLS 1 ... DC power supply system, 2 ... Rectifier, 3 ... Load, 4 ... Charger, 5, 20, 30, 40 ... Voltage compensator, 6 ... Positive side power supply line, 7 ... Negative side power supply line, 8 ... Positive output terminal, 9 ... Negative output terminal, 10 ... Storage battery, 11 ... High side power converter, 12 ... Low side power converter, 13, 21, 32 ... Control part, 13a ... Voltage detection part, 13b, 21b ... Microcomputer, 13c ... Drive unit, 14 ... High-side buck-boost chopper, 15 ... Low-side buck-boost chopper, 16, 33 ... High-side switch, 17 ... Low-side switch, 21a ... Current detector, 31 ... High-side boost chopper, 41 ... Input side Converter, 42 ... High side output side converter, 43 ... Low side output side converter, 45 ... Transformer, C1, C2, C11, C12, C13, C21, C22 ... Capacitor, D , D2, D11, D12, D16, D17, D21 to D24, D26, D28, D31, D32 ... diode, L1, L2, L14, L15, L21 ... reactor, L11 ... primary winding, L12 ... first secondary Winding, L13 ... second secondary winding, R1, R2 ... high resistance, R3 ... current detection resistance

Claims (8)

Power from a power supply device that outputs a DC voltage is supplied to a load by a positive power supply line and a negative power supply line, which are positive and negative power supply lines that are grounded through resistors of the same resistance value. In the configured DC power supply system, the DC power supply line is provided between the positive electrode power supply line and the negative electrode power supply line, and the DC voltage supplied from the power supply device to the load is lower than a predetermined voltage value. A voltage compensator for compensating a DC voltage for operating a load,
A storage battery in which a midpoint between a positive electrode and a negative electrode is grounded to supply the compensation DC voltage to the load;
Based on the voltage of the storage battery, the potential of the positive power supply line is made higher by a predetermined positive compensation voltage than the potential of the positive electrode of the storage battery, and the negative power supply line is based on the voltage of the storage battery. Compensation voltage generation means is provided for lowering the potential of the storage battery by a predetermined negative-side compensation voltage than the negative-electrode potential of the storage battery. The voltage compensator according to claim 1,
The compensation voltage generating means sets the positive compensation voltage and the negative compensation voltage to the same voltage value. The voltage compensator according to claim 1 or 2,
Ground current detection means for detecting a ground current flowing from the storage battery to the ground potential side through the resistors,
The compensation voltage generation means individually sets the positive-side compensation voltage and the negative-side compensation voltage so that the ground current detected by the ground-current detection means is a predetermined current value or less. A voltage compensation device. The voltage compensator according to any one of claims 1 to 3,
The compensation voltage generating means includes
A positive-side power conversion means that is provided between the storage battery and the positive-side power supply line and generates and outputs the positive-side compensation voltage based on the voltage of the input storage battery;
A negative-side power conversion means that is provided between the storage battery and the negative-side power supply line, and generates and outputs the negative-side compensation voltage based on the input voltage of the storage battery;
A voltage compensator characterized by comprising: The voltage compensator according to claim 4,
At least one of the positive side power conversion unit and the negative side power conversion unit is configured as a non-insulated type in which the input side and the output side are not insulated. The voltage compensator according to claim 5,
The positive-side power conversion means and the negative-side power conversion means are both capable of boosting or stepping down the input voltage and outputting a voltage whose positive / negative polarity is inverted with respect to the input voltage. It is comprised by these. The voltage compensation apparatus characterized by the above-mentioned. The voltage compensator according to any one of claims 4 to 6,
The positive-side power conversion means and the negative-side power conversion means are configured by a switching-type power conversion circuit, and each switching element is turned on / off according to a drive signal having a phase difference. A voltage compensation device for generating the compensation voltage. DC configured to supply power from a power supply device that outputs a DC voltage to a load via a positive power supply line and a negative power supply line, which are positive and negative power supply lines that are grounded via resistors, respectively. A power supply system,
The DC power supply system according to any one of claims 1 to 7, wherein the voltage compensating device according to any one of claims 1 to 7 is provided between the positive electrode side power supply line and the negative electrode side power supply line.

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