JPH02266870A - Power conversion device for battery - Google Patents

Abstract

PURPOSE:To shorten a time from starting until operation is shifted into stationary linkage operation by a method wherein a circuit is connected to an AC system to start the charging of a capacitor from the side of the AC system through the anti-parallel diode of an inverter upon the starting of the device to increase a voltage. CONSTITUTION:The supply of fuel into a fuel battery 1 is started at a starting time (t1) and a capacitor 6 is charged by the voltage ES of an AC system 9 through a resistor 11 and an anti-parallel diode 7b, then, the voltage of the battery arrives at the peak value sq. rt. 2ES of the voltage ES of the AC system 9 at a time (t2). In this case, a switch 8 is closed and another switch 10 is opened while an inverter 7 is put ON to increase the voltage EC of the capacitor 6 to a rated value. According to this operation, the switch 2 is closed and a booster chopper 5 is put ON. Then, the role of the control of the voltage EC of the capacitor 6 is changed from the inverter 7 into the booster chopper 5. The inverter 7 enters immediately into the active power control and the reactive power control of the AC system 9.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power conversion device for a battery that converts DC power from a fuel cell or the like into AC power and performs interconnected operation with a commercial AC system. be.

[Conventional technology]

FIG. 4 is a circuit diagram showing a conventional power conversion device for a fuel cell of this type, which was described in, for example, page 594 of the Proceedings of the National Conference of the Institute of Electrical Engineers of Japan in 1982. In FIG. 2) is a switch connected in series to this fuel cell (1), (3) and (4) are resistors and switches connected in series with each other and in parallel with the switch (2), ( A step-up chopper consisting of a 51-beam accelerator (5a), a transistor (5b) as a switching element, and a diode (5C) boosts the voltage of the fuel cell (1), which is generally low voltage and has large voltage fluctuations, and controls it to a predetermined voltage. (6) is a capacitor that smoothes the output voltage of the boost chopper (5), and (7) is a switching element transistor (7a) and an antiparallel diode (7b) connected in antiparallel to this transistor (7a). The input side of the inverter is connected to a capacitor (6), and the output side is connected to an AC system (9) via a switch to convert DC power to AC power.

Next, the operation will be explained with reference to the time chart in FIG. 5. Before time 0 t1, the device is in a stopped state, switches (2) (A) and B) are all opened, and the boost chopper (51 and inverter m is stopped.

Then, at time 11, the device is started. That is, the switch (a) is closed and the supply of fuel to the fuel cell (1) is started. As a result, the voltage EB of the fuel cell (1) starts to rise, and the capacitor (6) is connected to the fuel cell (
The capacitor (6) is charged by the voltage EB of 1), and the voltage EC of the capacitor (6) increases.

The voltage EB of the fuel cell (1) rises above the rated value, and the voltage EC of the capacitor (6) rises to the voltage E of the fuel cell (1).
When the battery is charged to B, at time t2), the switch (2) is closed and the switch (4) is opened. Then, the boost chopper ((6) is turned on and the voltage E of the capacitor (6) is
C is boosted from the level of voltage EB of the fuel cell (1) to the level of the rated DC voltage of the inverter (7).

Here, the operation of boosting the voltage by the boost chopper (5) will be explained as follows.That is, when the transistor (5b) is turned on, the output current of the fuel cell (1) flows out and increases through the accelerator (5a). Next, when the transistor (5b) is turned off, the increased amount of the output current accumulated in the accelerator (5a) passes through the diode (5C) and is transferred to the capacitor (6).
) and charges and boosts the voltage, resulting in a relationship of E C > E B. By controlling the on-off time ratio of the transistor (5b), the step-up ratio E C / E B can be arbitrarily adjusted. In this way, by providing a boost chopper (to), if the voltage EB of the fuel cell (1) fluctuates or decreases due to fluctuations in the amount of fuel supplied or fluctuations in the amount of power output to the AC system (9), etc. Also, the voltage E of the capacitor (6) which becomes the DC input voltage of the inverter (7)
C can be kept constant.

Then, at time t, when the voltage EC of the capacitor (6) reaches the rated DC voltage of the inverter (7), the inverter is turned on and an AC voltage is output. When this coincidence is obtained at time t4, the inverter (2) is controlled to match the magnitude and phase with the voltage of the inverter (2).When this coincidence is obtained at time t4, the switch is closed and the system shifts to regular operation with the AC system (9).

At time t, the operation is stopped; at this point, the inverter (7) and boost chopper (51) are turned off, the supply of fuel to the fuel cell (1) is stopped, and the switch (
21(5) is also opened. The charge in the capacitor (6) is discharged by a discharge resistor (not shown).

[Problem to be solved by the invention]

Since the conventional power converter for fuel cells is configured as described above, it takes a long time from the start of the device to the transition to regular operation with the AC system (9), and the operation sequence during this time is also difficult. There were problems such as complexity.

This invention was made in order to solve the above-mentioned problems, and provides a battery power conversion device that can shorten the time from startup to transition to regular system operation, and can also simplify the operation sequence. The purpose is to

[Means and effects for solving the problems] In the battery power conversion device according to the present invention, when starting the device, first, connection is made to the AC system, and the capacitor is connected from the AC system side via the anti-parallel diode of the inverter. The device is designed to start charging the battery. This allows synchronization with the AC system from the time the inverter starts operating.
No special time or sequence is required for synchronization.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (11 (21 (5) to (9) are the same or equivalent parts as before. QOI and (11) are the switch and resistor connected in series with each other and in parallel with switch 8 It is.

FIG. 2 is a time chart thereof, and the operation will be explained below along with FIG. As before, at time t, all switches (2) +8111 were opened, and the boost chopper (
51, the inverter (7) is also stopped. Then, at startup time t, the supply of fuel to the combustion cell (1) is started, and at the same time, the switch 00) is closed. This causes the capacitor (6) to connect to the resistor (11) and the anti-parallel diode (7b
), and the voltage EC of this capacitor (6) increases with a time constant determined by the resistor (11) and the capacitor (6). This charging voltage finally reaches the peak value (flEs) of the voltage ES of the AC system (9) at time t2.

Here, switch (a) is closed and switch (α) is opened, and at the same time, the inverter (7) is turned on to start DC output voltage control and the voltage EC of the capacitor (6) is increased to its rated value. .

When the voltage EC of the capacitor (6) reaches the rated value at time t, the switch (2) is closed and the boost chopper (
Turn on 9. Then, the role of controlling the voltage EC of the capacitor (6) is switched from the inverter ■ to the boost chopper ((5).The inverter (7) immediately controls the active power and reactive power of the AC system (9). The fuel cell (1) and the AC system (9) enter regular operation.

That is, conventionally, as shown in FIG. In the case shown in the figure, this time is not required, and the time until grid-connected operation is shortened.
Furthermore, the number of control modes is reduced by this amount, and the operation sequence is simplified.

Time t is the timing at which the operation is stopped, and since it is the same as in the conventional case, the explanation will be omitted.

In addition, in the above embodiment, the fuel cell (1) and the boost chopper (
5), and the lever switch (2) is closed at time t, which is the final point of activation. However, this switch (2) is omitted and the amount of fuel supplied to the fuel cell (1) is adjusted in parallel with the charging operation from the AC system (9) described above to the capacitor (6) that starts at time t1. However, by gradually increasing the voltage EB of the fuel cell (1), the capacitor (6) may be charged via the step-up chopper (51) and the diode (5c).

In addition, by turning on the boost chopper (51) at time t2 like the inverter (7), the boost chopper ((51)
) and inverter (7) at the same time as capacitor (6).
After completing the step-up, the step-up chopper (51 controls the DC voltage of the capacitor (6), and the inverter (to) controls the interconnection with the AC system (9). A switching method may also be used.

Furthermore, in the above embodiment, the AC system (9) and the inverter (
Although a switch (aa) is provided as a means of interconnection with 7), a switch using a semiconductor switching element such as a circuit breaker or a thyristor may also be used. (5b) (7a) are also not limited to transistors, but include GTOs and MOSFETs.

A self-extinguishing semiconductor switching element such as an IGBT may also be used.

Further, in the above embodiment, the case where the output end of the power conversion device is directly connected to the AC system (9) has been described, but the present invention also provides a method for suppressing ripples in the output AC current, The same can be applied to the case of connecting via a transformer for voltage matching or a filter for suppressing high frequencies.

FIG. 3 shows still another embodiment of the present invention, and in FIG. , (12A) (12B) beam axle, (13) a three-winding transformer for voltage matching between both inverters (7A) (7B) and the AC system (9), and (14) a filter.

In FIG. 3, two series of DC buses are connected in parallel to share the capacitor (6), but the DC buses may be separated and separate capacitors may be provided for each.

Further, in each of the above embodiments, a power conversion device for a fuel cell has been described, but the present invention can also be applied to other batteries such as a solar cell, and similar effects can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, when starting up the device, first, it is connected to the AC system and charging of the capacitor is started from the AC system side via the anti-parallel diode of the inverter to boost the voltage. This eliminates the need for special time for synchronization between the inverter and the AC system, shortens the time from device startup to transition to regular system operation with the AC system, and simplifies the operating sequence during this time. Become.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a fuel cell power conversion device according to one embodiment of the present invention, FIG. 2 is a time chart explaining its operation, and FIG. 3 is a circuit diagram showing the same device according to another embodiment of the present invention. FIG. 4 is a circuit diagram showing the conventional device,
FIG. 5 is a time chart illustrating the operation of the device shown in FIG. 4. In the figure, (1) is a fuel cell as a battery, (5) is a boost chopper, (6) is a capacitor, (7) is an inverter, (7a) is a transistor as a switching element, (7b) is an anti-parallel diode, (9) is an AC system. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent: Masuo Oiwa, Patent Attorney Fig. 3 Fig. 1 Fig. 7 ゛Inverter 7a-) Lange y Fig. 2 Fig. 4 Fig. 5

Claims (1)

[Claims] It consists of a battery, a boost chopper connected to the battery to boost its voltage and control it to a predetermined voltage, a capacitor connected to the output side of the boost chopper to smooth the output voltage, and a switching element and an anti-parallel diode. An inverter is connected between the capacitor and the AC system and converts between DC power and AC power. When starting up, the capacitor is first boosted, and after reaching a predetermined voltage, the inverter converts the battery and the AC system. for a battery, characterized in that boosting the voltage of the capacitor is started by charging from the AC system via an anti-parallel diode of the inverter. Power converter.