JPH0595626A - Dc power-supply parallel driving apparatus - Google Patents

Abstract

PURPOSE:To supply power respectively from a plurality of DC power supplies to a load by comparatively simple control. CONSTITUTION:In a DC power-supply parallel driving apparatus for parallel operating a plurality of DC power supplies to supply a load with power, LC smoothing filter circuit and voltage-drop chopper switching circuits S1, S2 are connected with the output side of each of the DC power supplies PS1. PS2 for outputting voltages E1, E2 higher than a load side voltage E1, the output sides of respective switching circuits S1, S2 are connected in parallel, these parallel connections are connected with the load via free-wheel diode Df and LC smoothing filter circuit, and respective switching circuits S1, S2 are ON-OFF controlled by a time division through a control circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply parallel operation apparatus for supplying a load with electric power by operating a plurality of DC power supplies such as a cogeneration power generator, a solar power generator and a fuel cell in parallel.

[0002]

2. Description of the Related Art In recent years, in DC power supply facilities such as buildings and factories, from the viewpoint of supply reliability and economical efficiency, in addition to rectifying the power output of a power purchase system, a rectified output of a cogeneration power generator, a solar battery, A system has been put into practical use in which a so-called new-type distributed power source such as a fuel cell is used, and these are connected to each other by direct current, that is, connected in parallel to supply power to a direct current load.

FIG. 5 shows a conventional DC power supply parallel operation apparatus of this type, in which a plurality of (two in the figure) DC power supplies PS _{1 and} PS ₂ each having a controllability are respectively connected to a backflow prevention diode D. _{1 and} D ₂ are connected in parallel, the parallel circuit is connected to the output terminals P and N through a smoothing filter circuit composed of a reactor L and a capacitor C, and power is supplied to the load from this.

The DC power supplies PS _{1 and} PS ₂ are composed of a rectified output of a power purchase system or a cogeneration power generator, various batteries, etc.
Although not particularly shown, each device has a device for measuring the voltage and current of each part and controlling the output voltages E _{1 and} E ₂ .
Each output voltage E _1, E ₂ is controlled to a voltage higher than the load side voltage El in consideration of the voltage drop due to the resistance of the diodes D _1, D ₂ and the reactor L.

In FIG. 5, the load power Pl (= El.Il) required for the load connected between the output terminals P and N is set.
) Is supplied, the respective output voltages E _{1 and} E ₂ of the DC power supplies PS _{1 and} PS ₂ are adjusted so that the power supply currents I _{1 and} I ₂ satisfying the relationship shown in the following formula ₁ are established. I am trying to output each. It should be noted that the loss amount is excluded from the equation (1).

[0006]

[Equation 1]

[0007]

In the above-mentioned conventional apparatus, the power supply currents I _{1 and} I ₂ are obtained by adjusting the output voltages E _{1 and} E ₂ of the DC power supplies PS _{1 and} PS ₂ , respectively. is a structure, in fact, the potential difference Delta] E 1 between the DC power supply PS _1, the output voltage E ₁ of the PS _2, E ₂ and the load side voltage _El, Delta] E _2, and by the respective line resistance R _1, R ₂ Power supply current I ₁ (=
ΔE ₁ / R ₁ ) and I ₂ (= ΔE ₂ / R ₂ ) are determined. In this case, since the line resistances R _{1 and} R ₂ are generally small values, a slight voltage fluctuation of the output voltages E _{1 and} E ₂ Output current E _1, E
There is a problem that a highly accurate method is required for the adjustment of ₂ , that is, the control of the potential differences ΔE _{1 and} ΔE ₂ .

In addition, when one output voltage, for example E ₁ , rises, as a result, the voltage Ea at the power source connection point rises, and E
Since a> E ₂ , the power source current I _{2 of the} other DC power source PS ₂ stops flowing (I ₂ = 0), and the other DC power source PS 2
_The phenomenon that power is not supplied from ₂ also occurs.

The present invention has been made in view of the above problems of the prior art, and the purpose thereof is to allow a plurality of DC power supplies having different output voltages to be connected in parallel. It is therefore an object of the present invention to provide a DC power supply parallel operation device capable of supplying electric power from each DC power supply to a load with relatively simple control.

[0010]

In order to achieve the above object, in a DC power supply parallel operation apparatus of the present invention, a smoothing filter circuit and a step-down voltage are provided on each output side of a DC power supply that outputs a voltage higher than the load side voltage. Connect the chopper circuit,
In addition to connecting the output side of each chopper circuit in parallel, connecting the parallel connection point to the load via the freewheel diode and the smoothing filter circuit, and providing a control circuit for on / off control of each step-down chopper circuit. is there.

[0011]

In the above-described structure, the step-down chopper circuits provided on the respective output sides of the plurality of DC power supplies are time-divisionally controlled to be turned on and off, whereby the respective DC power supplies output different voltages. Even if there is, you can connect these in parallel and supply power to the load from each,
Moreover, since the power control can be performed by the on / off duty control of each chopper circuit, it is not necessary to use the conventional highly accurate control method.

[0012]

EXAMPLES Examples will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, for two DC power supplies PS _{1 and} PS ₂ that output output voltages E _{1 and} E ₂ that are higher than the load-side voltage El, reactors L _{1 and} L ₂ and a capacitor C ₁ are provided on each output side. _connects the switch circuits S _1, S ₂ as the smoothing filter circuit and the step-down chopper circuit composed of C ₂ Prefecture, via the switch circuits S _1, S output side diode DS 1 for reverse breakdown voltage respectively _2, DS ₂ And the parallel connection point is connected to the output terminals P and N of the device through a free wheel diode D _f, a smoothing filter circuit including a reactor L and a capacitor C.

The DC power supplies PS _{1 and} PS ₂ are composed of a rectified output of a power purchase system or a cogeneration power generator, a solar cell, a fuel cell, etc., and have output voltages E _{1 and} E ₂ higher than the load side voltage El. On the condition that controllability is unnecessary. The switch circuits S _{1 and} S ₂ are composed of transistors, thyristors, etc., and are on / off controlled by the control circuit 1 shown in FIG.

That is, the control circuit 1 uses the load setting voltage El _ref and the load side voltage E measured between the output terminals P and N.
adder 2 for calculating the difference El _ref -El with l, controller 3 for calculating PI (proportional integration) of the difference El _ref -El, control reference signal E * from controller 3 and each DC power supply PS
_1, PS output voltage E _1, first formed by E ₂ or the like _2, the first and a second carrier signal for each of the switching circuits S _1, S _2, a pulse width modulator 4 to form the second gate signal, respectively , 5 are included.

As shown in FIG. 3, the first and second carrier signals are triangular waves having a constant period, respectively, and are formed by capacitors C _1,
The amplitude is controlled according to the magnitudes of the output voltages E _{1 and} E ₂ measured at both ends of C ₂ , and both carrier signals have a phase difference of ½ cycle with each other. The devices 4 and 5 form and output a gate signal for turning on the switch circuits S _{1 and} S ₂ when the levels of the first and second carrier signals become equal to or lower than the control reference signal E *.

When the operation is started in such a structure, both switch circuits S _{1 and} S ₂ are alternately turned on by the first and second gate signals from the control circuit _1, and when the switch circuit S ₁ is turned on, a direct current is generated. Power supply PS ₁ to reactor L
_{When the} power supply current I _{1 that} is determined by the inductance of ₁ flows and the switch circuit S ₂ turns on, the DC power supply P
The power supply current I ₂ flows from S _2, and the voltage / current waveform of each part as shown in FIG. 4 is obtained.

[0017] Now, the off period of both switching circuits S _1, S ₂ T, both the switch circuits S _1, each of the on-time T _1on of S _2, when the T _2on, each DC power supply PS _1, PS ₂ The respective average output current values I _a1, I _a2 are given by
It becomes like the formula of Formula 3.

[0018]

[Equation 2]

[0019]

[Equation 3]

Therefore, the required load power Pl (= El
· Il) to, as established the relationship indicated by the formula number of the next 4, each of the on-time T _{1o n} of both the switch circuits S _1, S _2, is controlled by the control circuit 1 to T _2on, the power It becomes possible to supply Pl to the load.

[0021]

[Equation 4]

As a result, even if the DC power supplies PS _{1 and} PS ₂ that output different voltages are connected in parallel, it is possible to supply electric power from the respective power supplies, and moreover, to the respective switch circuits S.
_The power control can be performed only by the on / off control of _{1 and} S ₂ , and the conventional high-precision control becomes unnecessary.

In the above embodiment, two DC power sources P
The case where S _{1 and} PS ₂ are operated in parallel has been described.
The same applies to the case of a plurality of M DC power supplies as described above, and the carrier signals corresponding to each DC power supply are sequentially formed with a phase difference of 1 / M period to control ON / OFF of each step-down chopper circuit in a time division manner. You can do it like this. Further, when the output voltage of any DC power supply is set equal to the load side voltage, the smoothing filter circuit and the step-down chopper circuit on the output side can be omitted.

[0024]

Since the present invention is configured as described above, it has the following effects. Multiple DC power supplies that output a voltage higher than the load voltage are connected in parallel via a step-down chopper circuit, and the output side is connected to the load via a flywheel diode and a smoothing filter circuit, and each step-down chopper circuit is time-shared. Since it is configured to supply power to the load by on / off control with, even if the output voltage of each DC power supply is different, these can be connected in parallel and power can be supplied from each to the load.
The power control can be performed by a relatively simple control of only the on / off control of each step-down chopper circuit, and the effect that there is no need to use a highly accurate control method as in the past can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a DC power source parallel operation apparatus according to the present invention.

FIG. 2 is a block diagram showing a control circuit of the embodiment.

FIG. 3 is a signal waveform diagram in the control circuit of FIG.

FIG. 4 is a voltage-current waveform diagram of each part in FIG.

FIG. 5 is a circuit diagram of a conventional example.

[Explanation of symbols]

PS _1, PS ₂ DC power supply L _1, L _2, L reactor C _1, C _2, C capacitor S _1, S ₂ switch circuit D _f freewheel diode 1 control circuit

Claims (1)

[Claims] 1. A DC power source parallel operation apparatus for operating a plurality of DC power sources in parallel to supply power to a load, wherein a smoothing filter circuit and a step-down chopper are provided on each output side of the DC power source that outputs a voltage higher than the load side voltage. A circuit is connected, the output side of each of the chopper circuits is connected in parallel, the parallel connection point is connected to a load through a freewheel diode and a smoothing filter circuit, and a control circuit for ON / OFF controlling each of the step-down chopper circuits is provided. A DC power source parallel operation device characterized by being provided.