JP2017153172A - Power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce loss in an element included in a power supply system.SOLUTION: In the power supply system, a power converter is controlled to a first control state forming a closed circuit by a first DC power supply 10a and a first reactor 10b without passing through a load and forming a closed circuit by a second DC power supply 12a and a second reactor 12b through the load and a second control state forming a closed circuit by the first DC power supply 10a and the first reactor 10b through the load and forming a closed circuit by the second DC power supply 12a and the second reactor 12b without passing through the load. A switching element common to a current path of a current flowing into the first reactor 10b and a current path of a current flowing into the second reactor 12b in the first control state and the second control state is provided, and by switching the first control state and the second control state at a time ratio, output voltage is controlled so as to become sum voltage of the first DC power supply 10a and the second DC power supply 12a.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a power supply system that transfers power between two DC power supplies and a load.

  A power supply system for supplying power from two DC power supplies to a load (for example, a vehicle drive motor) is disclosed (Patent Documents 1 to 5). Such a power supply system is also used to supply power from a plurality of solar cells to a load, for example. A step-up chopper (step-up converter) is connected to each of the solar cell modules, and control is performed so that the power generation efficiency in each solar cell module is maximized by MPPT control (maximum power point tracking). The reason for using a plurality of step-up choppers (step-up converters) in this way is that all the solar cell modules are connected in series when the power generation status of each solar cell module is different due to the influence of the installation location, etc. This is because if the control is performed by a converter, the power generation efficiency is lowered. As another reason, in a system with large generated power, if all the solar cell modules are connected in series, the output voltage becomes a high voltage, which may increase circuit design restrictions.

  For example, there is disclosed a power supply system in which a boost chopper circuit is provided for each of two DC power supplies, and a voltage from each DC power supply can be independently boosted by a boost chopper circuit and supplied to a load. In addition, a power supply system is disclosed in which two boost chopper circuits are connected by a bidirectional switching element, and power can be supplied from two DC power supplies to a load by cooperating the two boost chopper circuits. Furthermore, a series / parallel converter type power supply system is disclosed in which two DC power supplies can be connected in series and in parallel by switching elements.

  FIG. 11 shows a configuration example of a conventional power supply system 300. FIG. 12 shows a control state for the conventional power supply system 300. FIG. 13 shows changes in reactor currents I1 and I2 flowing through reactors L1 and L2 in each control state (state a to state e) in power supply system 300.

  In the state a, both the first switch S1 and the second switch S2 are on (time t1). In the state b, the second switch S2 is turned off (time t2). Thereafter, a natural commutation of current occurs from the diode D2 to the first switch S1, and the state c is shifted (time t3). In the state d, the first switch S1 is turned off, and at the same time, the second switch S2 is turned on (time t4). Thereafter, natural commutation of current occurs from the diode D1 to the second switch S2, and the state e is shifted (time t5). Then, the first switch S1 is turned on to return to the state a (time t6). Thus, one cycle of control is performed, and the voltages of the two DC power supplies are boosted and supplied to the load 302.

  FIG. 14 shows a configuration example of a series-parallel type power supply system 400. FIG. 15 shows a control state for the power supply system 400. FIG. 16 shows changes in reactor currents I1 and I2 flowing through reactor L1 and reactor L2 in each control state (state a to state c) in power supply system 400.

  In the state a, both the first switch S1 and the fourth switch S4 are in the off state, and both the second switch S2 and the third switch S3 are in the on state (time t1). In the state b, the second switch S2 is turned off and the first switch S1 is turned on (time t2). In the state c, the fourth switch S4 is turned off and the second switch S2 is turned on (time t3). Thereafter, the first switch S1 is turned off and the fourth switch S4 is turned on (time t4). Thus, one cycle of control is performed, and the voltages of the two DC power supplies are boosted and supplied to the load 402.

Japanese Patent No. 3655277 Japanese Patent No. 5492040 JP2013-13234A Japanese Patent Laying-Open No. 2015-165759 Japanese Patent Laying-Open No. 2015-162963

  In the conventional power supply system, the increase / decrease switching timing of the current flowing through the two reactors coincides only once per cycle at time t4. If the timing of increase / decrease switching of the current flowing through the two reactors coincides, there is an effect of reducing the loss, but the conventional power supply system cannot obtain the effect only once per cycle, and the loss reduction in the power supply system is insufficient. Met.

  One aspect of the present invention includes a first DC power supply, a first reactor connected in series to the first DC power supply, a second DC power supply, and a second DC power supply connected in series. And a power converter including a plurality of switching elements that perform voltage conversion of DC voltage from the first DC power source and the second DC power source, and the power converter includes: The first DC power source and the first reactor form a closed circuit without passing through a load, and the second DC power source and the second reactor form a closed circuit through a load. The first control state in which the plurality of switching elements are controlled, the first DC power source and the first reactor form a closed circuit via a load, and the second DC power source and the second Reactors form a closed circuit without going through a load And a second control state in which the plurality of switching elements are controlled, and in the first control state and the second control state, the current path flowing through the first reactor and the first control state A switching element that is common to the current path flowing through the two reactors, and switching the first control state and the second control state at a time ratio, thereby changing the output voltage to the first DC power source and the first The power supply system is controlled so as to be the sum voltage of the two DC power supplies.

  Here, the power converter is provided for the first DC power source, and includes a first power converter including at least one switching element that performs power conversion between the first DC power source and the load. And a second power converter provided with respect to the second DC power source, and comprising at least one switching element that performs power conversion between the second DC power source and the load; It is preferable to include a coupling element that regulates a current direction between the power conversion unit and the second power conversion unit.

  ADVANTAGE OF THE INVENTION According to this invention, the loss in the element contained in a power supply system can be reduced.

It is a figure which shows the structure of the power supply system in embodiment of this invention. It is a figure which shows the system using the power supply system in embodiment of this invention. It is a figure which shows the control state of the power supply system in embodiment of this invention. It is a figure which shows the change of the reactor current in each control state of the power supply system in embodiment of this invention. It is a figure which shows the loss in each element in a power supply system at the time of not controlling a line voltage to a sum voltage. It is a figure which shows the loss in each element in a power supply system at the time of controlling a line voltage to a sum voltage. It is a figure which shows the loss in each element in a power supply system at the time of not controlling a line voltage to a sum voltage. It is a figure which shows the structure of the power supply system in a modification. It is a figure which shows the control state of the power supply system in embodiment of this invention. It is a figure which shows the change of the reactor current in each control state of the power supply system in embodiment of this invention. It is a figure which shows the structural example of the conventional power supply system. It is a figure which shows the control state of the power supply system in the conventional power supply system. It is a figure which shows the change of the reactor current in each control state in the conventional power supply system. It is a figure which shows the structural example of the conventional power supply system. It is a figure which shows the control state of the power supply system in the conventional power supply system. It is a figure which shows the change of the reactor current in each control state in the conventional power supply system.

[Power system configuration]
As shown in FIG. 1, a power supply system 100 according to an embodiment of the present invention includes a first DC power supply 10a, a first reactor 10b, a second DC power supply 12a, a second reactor 12b, and a first power converter. 14, the 2nd power converter 16 and the connection element 18 are comprised. A load 102 is connected between the first power line X1 on the high voltage side of the power supply system 100 and the second power line X2 on the low voltage side.

  In the power supply system 100, power is supplied to the load 102 from at least one of the first DC power supply 10a and the second DC power supply 12a via at least one of the first power converter 14 and the second power converter 16. You can (powering). Further, power can be recovered from the load 102 to at least one of the first DC power supply 10a and the second DC power supply 12a via at least one of the first power converter 14 and the second power converter 16. (Regeneration).

  The first DC power supply 10a and the second DC power supply 12a are not particularly limited, but can be solar cells. The first DC power supply 10a and the second DC power supply 12a may include power storage means such as a rechargeable battery or an electric double layer capacitor that can be charged and discharged.

  The first power converter 14 includes a circuit that performs power conversion of the first DC power supply 10a. That is, the output voltage of the first DC power supply 10a can be boosted and supplied to the load 102, and the voltage of the electric power from the load 102 can be reduced and regenerated to the first DC power supply 10a. The first power converter 14 includes an upper arm 14a and a lower arm 14b. In the upper arm 14a, an upper arm side switching element 14d and a feedback diode 14e are connected in parallel. The lower arm 14b has a lower arm side switching element 14f and a feedback diode 14g connected in parallel. The upper arm 14a and the lower arm 14b are connected in series, and the load 102 is connected to both ends thereof. The first DC power supply 10a is connected to a connection point C1 between the upper arm 14a and the lower arm 14b via the first reactor 10b.

  The second power converter 16 includes a circuit that performs power conversion of the second DC power supply 12a. In other words, the output voltage of the second DC power source 12a can be boosted and supplied to the load 102, and the voltage of the power from the load 102 can be stepped down and regenerated to the second DC power source 12a. The second power converter 16 includes an upper arm 16a and a lower arm 16b. In the upper arm 16a, an upper arm side switching element 16d and a feedback diode 16e are connected in parallel. In the lower arm 16b, a lower arm side switching element 16f and a feedback diode 16g are connected in parallel. The upper arm 16a and the lower arm 16b are connected in series, and the load 102 is connected to both ends thereof. The second DC power supply 12a is connected to the connection point C2 between the upper arm 16a and the lower arm 16b via the second reactor 12b.

  The coupling element 18 is an element that regulates the current direction between the connection point C1 and the connection point C2. For example, the coupling element 18 is a rectifying element or a switching element, for example. The coupling element 18 is a bidirectional switching element, that is, has a low resistance value with respect to the current from the connection point C1 to the connection point C2 and the current from the connection point C2 to the connection point C1 when the switch is turned on. It is preferable that the element has pressure resistance on both sides of C1 and the connection point C2.

  In power supply system 100 in the present embodiment, by providing coupling element 18, the output voltage of first DC power supply 10 a is boosted not only through first power converter 14 but also through second power converter 16. The power can be supplied to the load 102 and the voltage of the power from the load 102 can be stepped down and regenerated to the first DC power supply 10a. Further, not only the second power converter 16 but also the first power converter 14, the output voltage of the second DC power supply 12a is boosted and supplied to the load 102, and the voltage of the power from the load 102 is also increased. The voltage can be stepped down and regenerated to the second DC power supply 12a.

  In the present embodiment, as shown in the system configuration diagram of FIG. 2, the direct current capable of controlling the output voltage of the power supply system 100 between the first power converter 14 and the second power converter 16 and the load 102. / The AC conversion circuit 104 (inverter) is provided. Note that a DC / DC conversion circuit (DC / DC converter) may be provided instead of the AC conversion circuit 104. For example, when the first DC power supply 10a and the second DC power supply 12a are solar cells, they can be used as a solar cell power supply system.

  The power supply system 100 is controlled by an external control unit (not shown). The control unit performs opening / closing control of switching elements included in the first power converter 14, the second power converter 16, and the coupling element 18. The control unit includes a microcomputer and the like. Control by the control unit will be described later.

[Control of power supply system]
Hereinafter, control when power is supplied from the power supply system 100 to the load 102 will be described. In the control of the power supply system 100 in the present embodiment, as in the prior art, the step-up operation on the first DC power supply 10a side is performed by controlling on / off the lower arm side switching element 14f, and the upper arm side switching element 16d. Is turned on / off to perform a boosting operation on the second DC power supply 12a side. Also on the second DC power supply 12a side, energy is stored in the second reactor 12b by turning on the upper arm side switching element 16d and boosted by releasing energy to the load 102 side by turning it off. can do.

  FIG. 3 shows a control state for the power supply system 100. FIG. 4 shows changes in reactor currents I1 and I2 flowing through the first reactor 10b and the second reactor 12b in each control state (state a to state d) in the power supply system 100. In the following description, since it is not necessary to consider the control during regeneration in the embodiment of the present invention, a part of the switching element is replaced with a diode. However, the control of the present invention can be applied to either the switching element as shown in FIG. 1 or the diode as shown in FIG.

  In this control, the upper arm side switching element 14d of the first power converter 14 and the lower arm side switching element 16f of the second power converter 16 are always turned off. Further, the connecting element 18 is always turned on. In such a state, the DC / AC conversion circuit 104 is controlled so that the output voltage of the power supply system 100, that is, the line voltage between the first power line X1 and the second power line X2 is the first DC power supply 10a. And the voltage of the second DC power supply 12a.

  In the power supply system 100, the power loss in the elements in the power supply system 100 can be reduced by providing the coupling element 18 to bypass the reactor current. Furthermore, by controlling the switching timing of the lower arm side switching element 14f and the upper arm side switching element 16d, the element loss can be suppressed to the maximum. Hereinafter, the control will be described.

  At time t1, the power supply system 100 is in the state a. In the state a, the lower arm side switching element 14f is turned on, and at the same time, the upper arm side switching element 16d is turned off. At this time, power is supplied to the load 102 from the second DC power supply 12a. Thereafter, natural commutation of current occurs from the feedback diode 16g to the lower arm side switching element 14f, and the state b is shifted (time t2).

  At time t3, the power supply system 100 is in the state c. In the state c, the lower arm side switching element 14f is turned off, and at the same time, the upper arm side switching element 16d is turned on. At this time, power is supplied to the load 102 from the first DC power supply 10a. Thereafter, natural commutation of the current occurs from the feedback diode 14e to the upper arm side switching element 16d, and the state d is shifted (time t4).

  At time t5, the power supply system 100 is returned to the state a. That is, the lower arm side switching element 14f is turned on, and at the same time, the upper arm side switching element 16d is turned off.

  The power supply system 100 is controlled in this way, but when the upper arm side switching element 16d is controlled to be switched off from the state d to the state a, the upper arm side switching element 16d has a reactor current I2 and a reactor current I1. Since only the difference current flows, the off loss can be reduced. Further, during the off control of the lower arm side switching element 14f when shifting from the state b to the state c, only the difference current between the reactor current I1 and the reactor current I2 flows through the lower arm side switching element 14f, so the off loss. Can be reduced.

  Here, the output voltage of the power supply system 100, that is, the line voltage between the first power line X1 and the second power line X2 is set to the sum voltage of the first DC power supply 10a and the second DC power supply 12a. The reason why the peaks and valleys of the reactor current I1 and the reactor current I2 can be matched as shown in FIG.

Voltage V1 of first DC power supply 10a, voltage V2 of second DC power supply 12a, line voltage VH between first power line X1 and second power line X2, ON ratio (duty) of lower arm side switching element 14f When D1 and the ON ratio (duty) D2 of the upper arm side switching element 16d, the following formulas 1 to 3 hold.

When these expressions are modified, the relationship between the ON ratio (duty) of the lower arm side switching element 14f and the upper arm side switching element 16d is expressed by Expression 4.

  As shown in FIG. 4, Equation 4 is obtained by controlling the sum of the ON ratios (duties) of the lower arm side switching element 14 f and the upper arm side switching element 16 d to coincide with one control cycle of the power supply system 100, as shown in FIG. This means that the peaks and valleys of the reactor current I1 and the reactor current I2 can be matched.

  For example, in the system configuration shown in FIG. 2, the first power converter 14 and the second power converter 16 are controlled so as to follow the optimum operating point, and the DC / AC conversion circuit 104 sets the line voltage VH to the first. What is necessary is just to control so that it may become the sum voltage of 1 direct current power supply 10a and 2nd direct current power supply 12a. Thereby, the element loss in the 1st power converter 14 and the 2nd power converter 16 can be reduced.

  FIG. 5 shows the respective elements when the line voltage VH between the first power line X1 and the second power line X2 is controlled to the sum voltage + 5V of the first DC power supply 10a and the second DC power supply 12a. Indicates loss. FIG. 6 shows the loss in each element when the line voltage VH between the first power line X1 and the second power line X2 is controlled to the sum voltage of the first DC power supply 10a and the second DC power supply 12a. Indicates. As shown in FIGS. 5 and 6, the line voltage VH between the first power line X1 and the second power line X2 is controlled to the sum voltage of the first DC power supply 10a and the second DC power supply 12a. In this case, it is possible to reduce the loss in the device as compared with the case where the voltage is not equal to the sum voltage.

  FIG. 7 shows a difference in loss of the entire power supply system 100 when the control according to the embodiment of the present invention is applied and when the conventional control is applied. As apparent from FIG. 7, when the control according to the embodiment of the present invention is applied, the loss of the entire power supply system 100 can be greatly reduced as compared with the case where the conventional control is applied.

[Modification]
In the present embodiment, the power supply system 100 including the coupling element 18 has been described as an example, but the scope of application of the present invention is not limited to this. For example, the present invention can be similarly applied to the series-parallel type power supply system 200 shown in FIG.

  Also in this modification, the output voltage of the power supply system 200, that is, the line voltage between the first power line X1 and the second power line X2 is equal to the sum voltage of the first DC power supply 10a and the second DC power supply 12a. Maintained. For example, the output voltage of the power supply system 200 can be controlled by connecting a DC / AC conversion circuit or a DC / DC conversion circuit between the first power line X1 and the second power line X2 of the power supply system 200.

  FIG. 9 shows a control state for the power supply system 200. FIG. 10 shows changes in reactor currents I1 and I2 flowing through first reactor 10b and second reactor 12b in each control state (state a and state b) in power supply system 200.

  In the state a, the first switch 20a, the third switch 24a, and the fourth switch 26a are in the on state, and the second switch 22a is in the off state (time t1). In the state b, the second switch 22a is turned on, and the fourth switch 26a is turned off (time t2). Thereafter, the fourth switch 26a is turned on, the second switch 22a is turned off, and the state returns to the state a (time t3). In this way, one cycle of control is performed, and the voltages of the two DC power supplies are boosted and supplied to the load 202.

  Also in the present modification, as in the power supply system 100 in the above embodiment, the loss of the entire power supply system 200 can be reduced as compared with the case where conventional control is applied.

  10a 1st DC power supply, 10b 1st reactor, 12a 2nd DC power supply, 12b 2nd reactor, 14 1st power converter, 14a upper arm, 14b lower arm, 14d upper arm side switching element, 14e feedback Diode, 14f lower arm side switching element, 14g feedback diode, 16 second power converter, 16a upper arm, 16b lower arm, 16d upper arm side switching element, 16e feedback diode, 16f lower arm side switching element, 16g feedback diode, 18 connecting element, 20a 1st switch, 22a 2nd switch, 24a 3rd switch, 26a 4th switch, 100 power supply system, 102 load, 104 AC conversion circuit, 200 power supply system, 202 load, 300 power supply system, 302 negative , 400 power system, 402 loads.

Claims (2)

A first DC power source, and a first reactor connected in series to the first DC power source;
A second DC power supply; a second reactor connected in series to the second DC power supply;
A power converter comprising a plurality of switching elements for performing voltage conversion of a DC voltage from the first DC power supply and the second DC power supply;
With
The power converter is
The first DC power source and the first reactor form a closed circuit without passing through a load, and the second DC power source and the second reactor form a closed circuit through a load. A first control state in which a plurality of switching elements are controlled;
The first DC power source and the first reactor form a closed circuit via a load, and the second DC power source and the second reactor form a closed circuit without a load. A second control state in which a plurality of switching elements are controlled;
Controlled by
In the first control state and the second control state, a common switching element is provided for a current path flowing through the first reactor and a current path flowing through the second reactor,
By switching between the first control state and the second control state at a time ratio, the output voltage is controlled to be the sum voltage of the first DC power source and the second DC power source. And power system. The power supply system according to claim 1,
The power converter is
A first power conversion unit provided with respect to the first DC power supply, the power conversion unit including at least one switching element that performs power conversion between the first DC power supply and the load;
A second power conversion unit provided with respect to the second DC power supply, and including at least one switching element that performs power conversion between the second DC power supply and the load;
A coupling element that regulates a current direction between the first power conversion unit and the second power conversion unit;
A power supply system comprising:

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