JPH02230304A - Invertor voltage controller for fuel battery - Google Patents

Abstract

PURPOSE:To compensate the drop of a voltage due to secular deterioration without complicating a harmonic filter and increasing the capacity of an invertor by switching and controlling a boosting tap arranged in a transformer in accordance with the voltage drop based on the secular deterioration of a fuel battery and controlling the voltage of an output AC power with constant while balancing the control of the invertor. CONSTITUTION:The transformer 14 is provided with N pieces of the boosting tap terminals 17B and 17C apart from a tap terminal 17 on the primary winding-side. Whenever they are switched by one tap, the rate of a control factor is reduced by lambda1/N.lambda2. Consequently, the rate of the control factor can be set to '1' at the beginning of switching when a tap switching device 15 switches the boosting tap one level by one whenever the rate of the control factor is deteriorated by lambda1/N.lambda2 due to the secular deterioration, of the fuel battery and the range of the control factor of the invertor 2 can be reduced to that in an initial characteristic. Even when the range of the control rate stretches widest that is immediately before switching, the range is needed only by adding lambda1/N.lambda2 to the range of an initial control rate. Thus, the drop of the voltage due to secular deterioration is compensated without complicating and enlarging the harmonic filter and increasing the capacity of the invertor.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to direct-failure integrated circuits with a large voltage drop, such as fuel cells.
The output of the E source is converted into AC power κ of a predetermined voltage and the load circuit K is
This article relates to voltage control devices for fuel cell inverter devices. [Prior art] A connection diagram of a conventional device is shown in Figure 2K. The electric power generated by the fuel cell 1 is converted into AC power by the inverter 2,
The voltage is transformed to a commercial voltage by a transformer 4 connected via the output side K reactor 3t, and power is supplied to a load 5. Alternatively, as shown by the dotted line in the figure, Kl! When connected to the commercial system 8, the inverter 2 applied here is a voltage-type PWM inverter], and the control rate λ can be changed.
The output voltage of the inverter 2 can be changed by changing the output voltage of the inverter 2 to the input voltage of the inverter 1k.
Vf and the control rate are given by the following equation. Vi=K−Vf. λ (K is constant a) ・・・・・・
... (1) This control rate compensates for impedance drops such as voltage fluctuations due to the V-1 characteristic of the λ company fuel cell 1 and reactance drops due to the size of the load, and the AC output voltage v
1t - Controlled by a control unit 7 which receives a detection signal from a voltage detector 6 and issues a control signal so that the voltage is always constant. [Problems to be Solved by the Invention] As shown in FIG. 3, an example of the voltage-current characteristic diagram of a fuel cell, in the initial characteristic curve 101K, the output voltage Vf changes from the open-circuit voltage Vfo to the increase in the current f. It exhibits a drooping characteristic that decreases (due to an accompanying increase in reactance drop). In addition, the fuel cell does not deteriorate over time, and the final characteristic song #1
There is no noticeable voltage drop towards 02K, showing a trend. In the conventional device K, the output current IIf varies from zero to the rated current 1fn.
In order for the inverter 2 to cover the actance drop voltage and its secular change, the range of the control rate λ of the inverter 2 becomes wide. Expanding the control range widens the number of harmonics generated, and especially at the end of aging, low-order harmonic components increase. Therefore, a problem arises in that the configuration of the filter for blocking harmonics becomes complicated and large. Also, when the output voltage of the fuel cell decreases, the inverter requires a large current to maintain the output voltage, so it is necessary to take this into account and increase the inverter capacity in advance. There are drawbacks that may cause disadvantages.

The purpose of this system is to supply constant-voltage controlled AC power to the load circuit by correcting it without increasing the capacity. [Means for Solving the Problems] In order to solve the above problems, according to the present invention, the output of the fuel cell is controlled at a constant voltage by a voltage type PWM inverter and a transformer, and is converted into AC power to power the load circuit. An output voltage control device for a K supply device, wherein the transformer is equipped with a tap switching device, and when there is a significant drop in the output voltage of the fuel cell, the voltage is boosted by switching the tap switching device, and the voltage is increased by switching the tap switching device. In combination with the control rate control of the PWM inverter, the output AC voltage will be controlled at a constant voltage. [Operation] The above measures were taken with the focus on the fact that the deterioration of the characteristics of fuel cells progresses gradually over a period of several months to several years.
By adding a tap switching device to the external voltage transformer to compensate for the voltage drop due to deterioration of the fuel cell over time, it is possible to reduce the control rate range of the inverter to a range K that mainly covers the initial characteristics of the fuel cell. , thus eliminating negative effects on harmonic filters and inverter capacity. [Examples] The present invention will be explained below based on examples.

FIG. 1 is a connection diagram of an apparatus for explaining an embodiment of the present invention. In FIG. K, the transformer 14 includes a plurality of tap terminals 17A, 17B, 17C, etc. on its primary winding side, and a non-voltage tap switching device 15 for selecting the tap terminals.

In the device K configured in this way, if the load power factor of the load 5 is 1k1, the open circuit voltage of the fuel cell 1 is Vfo, the output voltage of the inverter is t-Vi, and the primary voltage of the transformer 4 is t-VO, then the inverter 2 The control rate λ0 at the time of opening is expressed by the following equation.

λowVo/K-Vfo ・・・・・・・・・
・・・・・・(2) Maku, in the brush stroke diagram in Figure 3,
Fuel that corresponds to the rated output current fn of the fuel cell! The output voltage of the battery is Vf in the initial characteristic, and v in the final characteristic.
r,, If the reactance drop voltage is Vx, the initial control force of the inperter is λ! , #% period control force λ weight is calculated by the following formula λm. -9T so-called shiK-vfl ・・・・・・・・・(3
)A,=Vo"+Vx"/K-Vf.・－・－
”(4) Therefore, the ratio of the initial and final control rates λ1/λ8
becomes Vf, /Vf. In embodiment K, the transformer 14 has N step-up tap terminals 17B on its primary winding side in addition to the lowest tap terminal 17A.
Equipped with 170 etc., Kλs/N・λ every time one tap is switched.
, the control force ratio can be reduced by .

Consequently, due to aging of the fuel cell, the control rate ratio decreases to λ.
If the tap switching device 15 switches the step-up tap 1i-1 step each time the tap switching device 15 decreases by s/N·λ3, the control rate ratio can be set to 1 at the beginning of switching, and the control rate range of the imperter 2 can be set to 1. Even when the control rate range is widest just before switching, λs/
Since the range is N・λst−, the control rate range can be significantly reduced compared to the conventional device κ, which covers the entire control rate range due to aging K, which is λ1/λ. Since the control rate range of the imperter 20 is shortened, the spread of each harmonic component and the change in the component ratio are also reduced, which simplifies the configuration of the high frequency filter, making it possible to reduce the size of the fuel cell. Since the inverter no longer requires a large current to compensate for the voltage drop due to aging deterioration κ, there is no need to increase the inverter capacity t in advance in anticipation of aging deterioration. It can be made smaller. Since the transformer tap is a full capacity tap, the transformer 14 becomes larger by providing the tap and the tap switching device t''.
Since the capacity unit cost of an inverter is much higher than that of a transformer, the control rate range of the inverter device can be reduced without sacrificing economic efficiency. [Effects of the Invention] As described above, the present invention switches and controls the external pressure tag provided in the transformer in response to the voltage drop caused by aging of the fuel cell. The power was configured to be controlled at a constant voltage. As a result, it is possible to reduce the control rate range to be covered by the imperter.
To provide a voltage control device AT- that eliminates problems such as complication and enlargement of harmonic filters and increase in inverter capacity, which conventionally occurred due to a wide control rate range, and allows voltage-type PWM inverter devices to be made smaller and more convenient. can do.

[Brief explanation of the drawing]

FIG. 1 is a device connection diagram for explaining an embodiment of Jin's invention, FIG. 2 is a device connection diagram for explaining a conventional device,
Figure 3 shows the voltage-current characteristics diagram of a fuel cell. DESCRIPTION OF SYMBOLS 1... Combustion IE pond, 2... Voltage type PWM inverter, 4... Transformer, 5... Load, 6... Voltage detector, 7... Control part, 14... Transformer with tap, 16.
・・Tap switching V 1st side of 2 locks■ Fig. 3

Claims (1)

[Claims] 1) An output voltage control device for a device that converts the output of a fuel cell into constant-voltage controlled AC power using a voltage-type PWM inverter and a transformer and supplies it to a load circuit, wherein the transformer includes a tap switching device. When there is a significant drop in the output voltage of the fuel cell, the output AC voltage is controlled at a constant voltage by boosting the voltage by switching the tap switching device and controlling the control rate of the voltage type PWM inverter. A voltage control device for a fuel cell inverter device, characterized by: