JP3097348B2 - Load fluctuation countermeasure circuit for independent power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an independent power supply apparatus which uses a DC independent power supply having a slow load following capability as a power supply, converts the power into constant-voltage controlled AC power by a voltage type self-excited inverter, and supplies the AC power to a load. The present invention relates to a configuration of a load fluctuation countermeasure circuit added for compensating a load following capability of a DC independent power supply.

[0002]

2. Description of the Related Art In an independent DC power source such as a fuel cell power generation system, the output power is controlled by the amount of reactant gas supplied to the fuel cell. There is a drawback, and there is a problem in that the control of the voltage-type self-excited inverter which converts the output power into constant-voltage-controlled AC power and supplies it to the load is hindered. Therefore, there has been known an independent power supply device in which a load fluctuation countermeasure circuit for compensating the load followability of the independent DC power supply is added and the constant voltage control by the voltage type self-excited inverter is stabilized.

FIG. 4 is a block diagram showing a conventional load fluctuation countermeasure circuit of an independent power supply device. The output of, for example, a fuel cell power generator 1 as an independent DC power supply is supplied to a voltage type self-excited inverter 2.
An independent power supply device that converts the AC power into constant-voltage controlled AC power and supplies the AC power to the load 9 includes a current regulator 3 connected in series to the independent DC power source 1, and a parallel connection to the independent DC power source 1 via the current regulator 3. A load fluctuation countermeasure circuit 5 comprising a connected energy buffer such as a battery 4 is provided. The load fluctuation countermeasure circuit 5 adjusts the output current If of the fuel cell 3 to a predetermined current value corresponding to the load current Il by the current adjustment circuit 3 and performs a steady operation.
The increase in the input current Ic of the inverter 2 corresponding to the rapid increase of l is compensated by the discharge current Id of the battery 4, and the excess of the output current of the current adjusting circuit 3 caused by the rapid decrease of the load current Il is replaced by the battery. By absorbing the charging current Ic of FIG. 4, the following capability of the independent power supply unit with respect to the sudden increase and decrease of the load current Il is improved.

[0004]

In the conventional independent power supply, the current regulating circuit 3 of the load fluctuation countermeasure circuit 5 is connected in series to the output side of the independent DC power supply (fuel cell power generator) 1 to determine the output current If. Since the current control is continuously performed during the steady operation, there is a problem that a power loss is constantly generated in the current control circuit 3, for example, in a chopper circuit, and the total efficiency as an independent power supply is reduced due to this. There is a need for improvement.

An object of the present invention is to provide an independent power supply device having a load fluctuation countermeasure circuit which does not cause loss during steady operation and therefore does not adversely affect the total efficiency of the independent power supply device.

[0006]

According to the present invention, there is provided, according to the present invention, a constant voltage control of the output power of an independent DC power supply comprising a fuel cell having a low load following capability by a voltage type self-excited inverter. An independent power supply device that converts the converted AC power to a load and includes a battery as an energy buffer for compensating for a delay in the load following capability of the independent DC power supply. Is provided in parallel with the independent DC power supply, and the current control circuit comprises an anti-parallel circuit of a charge step-up chopper and a discharge step-down chopper, and the battery is connected through the current control circuit. The control system of the current control circuit is connected in parallel to the independent DC power supply and sets a change in the input current of the voltage type self-excited inverter. A discharge control system for controlling the discharge current of the battery flowing through the step-down chopper for discharging to follow an increase in load, using the battery current as a detection value, a set value of the output voltage of the independent DC power supply, and an output voltage of the battery And a charge control system for controlling the charging step-up chopper at a constant voltage using the detected value as a detection value. A current command limiter for preventing overcharging of the battery is provided with a minor control circuit of the charge control system.
It shall be included as a loop.

Furthermore, a circuit is provided for holding the set value of the discharge control system for a predetermined time after detecting an increase in the input current of the voltage type self-excited inverter. After the holding time has elapsed, the output current of the independent DC power supply is provided. , The independent power supply is operated in a steady state.

[0008]

In the configuration of the present invention, the current control circuit for controlling the charging current or the discharging current of the battery is provided in parallel with the independent DC power supply. In this case, only the discharge current and the charge current flowing to compensate for the delay of the battery are controlled, and the conventional current adjustment circuit adjusts the steady-state current to eliminate the loss that always occurs, and the independent power supply device is controlled by the current. The function to eliminate the adverse effect on the efficiency of the fuel cell is obtained. Also, the configuration is such that the battery is connected in parallel to the independent DC power supply via a current control circuit consisting of an anti-parallel circuit of a charge step-up chopper and a discharge step-down chopper, so that the input current of the inverter changes when the load increases. A discharge control system using the minute as a set value and the battery current as a detection value detects an increase in the inverter current and supplies the discharge current of the battery controlled by the discharge step-down chopper following the increase in the load. At the same time, when the load decreases, a charge control system that uses the output voltage of the fuel cell as a set value and the output voltage of the battery as a detection value detects the rise in the independent DC power supply voltage, and controls the charge boosting chopper with a constant voltage to control the load. Since the charging current is controlled in accordance with the decrease of the electric current, the function of cutting off the control of the discharging current and the charging current and preventing the interference between them is obtained. Also, by including a current command limiter for preventing overcharge as a minor loop of the charge control system, it is possible to prevent the life of the battery from being shortened due to overcharge.
A load fluctuation countermeasure circuit having excellent long-term stability can be provided.

Further, a circuit is provided for holding a set value of the discharge control system for a predetermined time after detecting an increase in the inverter input current, and after the holding time has elapsed, the independent power supply is normally operated by the output current of the independent DC power supply. If it is configured to operate, a function is obtained in which the discharge time of the battery is limited to the follow-up delay time of the independent DC power supply, for example, about 5 seconds, and the loss occurrence time of the discharge step-down chopper is reduced to a necessary minimum.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments and reference examples. FIG. 1 is a connection diagram showing a load fluctuation countermeasure circuit of an independent power supply device according to a reference example of the present invention. In the following, the same components as those of the prior art are denoted by the same reference numerals, and redundant description will be omitted. In the figure, an independent power supply for converting the output power of a fuel cell 1 as an independent DC power supply having a slow load following capability into AC power controlled at a constant voltage by a voltage-type self-excited inverter 2 and supplying the AC power to a load 9 is a fuel supply. Battery 1
Battery 4 as an energy buffer for compensating for the delay of the load following capability of the battery, and a discharging diode as a current control circuit for controlling its charging current Ic or discharging current Id.
A load fluctuation countermeasure circuit 11 comprising an anti-parallel circuit of a power supply 12, a charging step-down chopper 13, and a charge control system 14 is provided in parallel with the fuel cell 1.

That is, the load fluctuation countermeasure circuit 11 comprises a battery 4 connected in parallel to the fuel cell 1 via a discharging diode 12, and a charging step-down chopper connected in anti-parallel to the discharging diode 12. 13 and the output voltage Vf of the fuel cell 1 detected by the voltage detector 1v is set to a set value.
and a charge control system 14 for controlling the charge step-down chopper 13 at a constant voltage by using the output voltage Vb of the battery 4 detected by v as a detection value. And a current command limiter 17, and is provided with a minor loop 15 for preventing overcharging of the battery-4.

The load fluctuation countermeasure circuit 1 configured as described above.
In the independent power supply device having the discharge diode 1, the output voltage Vf of the fuel cell 1 due to the sudden increase of the load is reduced by the discharge diode 12
Detects the discharge current Id of the battery-4
To compensate for the delay in the increase in the output of the fuel cell 1, and the charge control system 14 detects the increase in the output voltage Vf of the fuel cell 1 due to a sudden decrease in the load as a difference from the battery voltage Vb. Since the charge current Ic of the step-down chopper 13 is controlled to absorb the excess output power of the fuel cell 1, the discharge diode 12 and the charge step-down chopper 13 as current control circuits follow the load of the fuel cell 1. The battery 4 controls only the discharge current and the charge current flowing to compensate for the delay in the power supply, and eliminates the constant loss caused by adjusting the steady-state current by the conventional current adjustment circuit. In addition, the adverse effect on the total efficiency of the inverter 2 can be eliminated, and the fluctuation of the input power of the inverter 2 can be eliminated, whereby the constant voltage control of the inverter 2 can be stabilized. Point is obtained.

Also, by providing a minor loop 15 including a current command limiter 17 for preventing overcharging in the charging control system 14, a reduction in the life of the battery due to overcharging is prevented, and long-term stability is achieved. An excellent load fluctuation countermeasure circuit 11 can be obtained. FIG. 2 is a connection diagram showing a load fluctuation countermeasure circuit of the independent power supply device according to the embodiment of the present invention, and FIG. 3 is a time chart showing an operation of the load fluctuation countermeasure circuit in the embodiment. In FIG. 2, a load fluctuation countermeasure circuit includes an anti-parallel circuit of a charge step-up chopper 22 and a discharge step-down chopper 23 serving as a current control circuit, and a fuel cell 1 as an independent DC power supply connected through the anti-parallel chopper circuit. A set value of the change ΔIi of the input current of the voltage-type self-excited inverter 2 detected by the battery 4 as the connected energy buffer and the current detector 2i, and the battery current detected by the current detector 4i A discharge control system 24 for generating a discharge current command value 24S for controlling the discharge current Id of the battery flowing through the discharge step-down chopper 23 to follow an increase in load, using the detected value Id as a detection value, and setting the output voltage Vf of the fuel cell to a set value. The charging step-up chopper 2 uses the negative output voltage Vb as a detection value.
And a charge control system 25 for outputting a charge current command value 25S for constant voltage control of the battery 2. The current command limiter 17 for preventing overcharging of the battery is provided with a minor control of the charge control system 25.
It is provided as a loop 15.

Further, at the output side of the current detector 2i for detecting the change ΔIi in the input current of the inverter 2, the set value of the discharge control system 24 is set for a predetermined time after the increase in the inverter input current is detected. A holding circuit, for example, a timer-switch circuit 26 is provided, and the holding time is limited to a follow-up delay time of the independent DC power supply 1, for example, about 5 seconds. The device is configured to operate in a steady state.

In the load fluctuation countermeasure circuit configured as described above, when the load increases, a discharge control system 24 using the change .DELTA.Ii of the input current of the inverter 2 as a set value and the battery current Id as a detected value is provided by an inverter. When the increase in the current is detected, the discharge current Id of the battery controlled by the discharge step-down chopper 23 is supplied in accordance with the increase in the load, and when the load decreases, the output voltage Vf of the fuel cell 1 is set to the set value. A charge control system 25 that uses the output voltage Vb of the negative value as a detection value.
Detects a rise in the output voltage of the fuel cell, controls the charge boost chopper 22 at a constant voltage, and controls the charge current Ic following the decrease in the load. In addition, overcharging is performed by the current command limiter 17.
Is blocked by the minor loop 15 having Therefore, since the control of the discharge current and the control of the charge current are optimally controlled without interfering with each other, the control is higher than that of the above-described reference example in which the control is performed using the difference between the regulation of the independent DC power supply and the battery. Accuracy can be obtained, and a battery can be selected without worrying about matching of regulation with an independent DC power supply. Therefore, there is an advantage that selection of a battery can be facilitated.

Further, a circuit 2 for holding the set value of the discharge control system for about 5 seconds after detecting an increase in the inverter input current.
6, the inverter 2 is provided as shown in FIG.
Control system 24 which has detected an increase ΔIi in the input current of
Sets the discharge current command value 24S to the discharge step-down chopper 23.
For 5 seconds, during which the input current I of the inverter
i is maintained as the sum of the output current If of the independent DC power supply and the discharge current Id from the battery, and thereafter, the operation shifts to the steady operation with the increased output current If of the independent DC power supply. An excessive rise in If and a decrease in Ii are detected by the charge control system 25, and the charge current Ic is controlled by the charge current command value 25S. Therefore, the discharge time of the battery is limited to the delay time of the follow-up of the independent DC power supply, for example, about 5 seconds.

[0017]

As described above, according to the present invention, a current control circuit for controlling a charging current or a discharging current of a battery is provided in parallel with an independent DC power supply. As a result, the current control circuit controls only the discharge current and the charge current flowing for the battery to compensate for the delay of the load following capability of the independent DC power supply, and the conventional current adjustment circuit adjusts the steady-state current. Thus, an independent power supply device provided with a load fluctuation countermeasure circuit that eliminates a loss that is constantly generated, generates a small loss, and has little adverse effect on the total efficiency of the independent power supply device can be provided. Further, by configuring the battery to be connected in parallel to the independent DC power supply via a current control circuit including an anti-parallel circuit of the charge boosting chopper and the discharging step-down chopper, the control of the discharge current and the charge current is cut off. Delay of the fuel cell can be compensated for without any interference.

Furthermore, by providing a circuit for holding the set value of the discharge control system for a predetermined time after detecting an increase in the inverter input current, the discharge time of the battery can be reduced by a load following delay of the fuel cell, for example, 5 times. This is limited to about seconds, so that the loss generation time of the step-down chopper for discharge can be reduced, and the effect on the total efficiency of the independent power supply can be reduced to the minimum.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing a load fluctuation countermeasure circuit of an independent power supply device according to a reference example of the present invention.

FIG. 2 is a connection diagram showing a load fluctuation countermeasure circuit of the independent power supply device according to the embodiment of the present invention;

FIG. 3 is a time chart showing the operation of the load fluctuation countermeasure circuit in the embodiment.

FIG. 4 is a configuration diagram showing a conventional load fluctuation countermeasure circuit of the independent power supply device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 independent DC power supply (fuel cell power generator) 2 voltage-type self-excited inverter 3 current control circuit 4 energy buffer (battery) 5 load fluctuation countermeasure circuit 9 load 11 load fluctuation countermeasure circuit 12 discharge diode 13 Step-down chopper for charging 14 Charge control system 15 Minor loop 16 Voltage regulator 17 Current command limiter 18 Current regulator 22 Step-up chopper for charging 23 Step-down chopper for discharge 24 Discharge control system 24S Command value of discharge current Id 25 Charge control System 25S Command value of charging current Ic 26 Circuit for holding discharge time If Output current of independent DC power supply Ii Input current of inverter ΔIi Change in input current of inverter Vf Output voltage of independent DC power supply Vb Output voltage

Claims (2)

(57) [Claims] 1. An independent power supply device for converting the output power of an independent DC power supply comprising a fuel cell having a slow load following capability into AC power controlled by a voltage-type self-excited inverter at a constant voltage and supplying the AC power to a load. In a device provided with a battery as an energy buffer for compensating for a delay in load following capability of a DC power supply, a current control circuit for controlling a charging current or a discharging current of the battery is provided in parallel with the independent DC power supply. And the current control circuit comprises an anti-parallel circuit of a charge step-up chopper and a discharge step-down chopper. The battery is connected in parallel to the independent DC power supply via the current control circuit, and a control system of the current control circuit is provided. Flows through the discharge step-down chopper as a set value of a change in the input current of the voltage type self-excited inverter and a detected value of the battery current. A discharge control system for controlling a discharge current of a battery to follow an increase in load; and a charge for controlling a voltage of the charging step-up chopper with an output voltage of the independent DC power source as a set value and an output voltage of the battery as a detection value. And a current command limiter for preventing overcharging of the battery as a minor loop of the charging control system. 2. A circuit for holding a set value of a discharge control system for a predetermined time after detecting an increase in the input current of the voltage-type self-excited inverter, and after the elapse of the holding time, the output current of an independent DC power supply. 2. The circuit according to claim 1, wherein the independent power supply is operated in a steady state.