JPS63277470A - power generation system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a power generation system that performs hybrid operation of a power supply device such as a fuel cell or a solar cell and a battery, and particularly aims to improve the operation control form when the voltages of both are close to each other. Regarding the power generation system.

[Conventional technology]

Generally speaking, the characteristics of power supplies such as fuel cells or solar cells are that the output voltage (!2) is proportional to the output current (!2).
It is a power supply device that has a large change in V, ) and a large slope of I/V characteristics, so-called large voltage droop characteristics. On the other hand, the battery voltage (Va) varies greatly depending on its charging/discharging state. Therefore, both voltages are V r > V 1%
In such a state, it is necessary to perform step-down control, and in a state where Vr<Va, step-up control is required. As the control method, the methods shown in FIGS. 8 to 10 are known. Figure 8 shows what is commonly called a DC/DC converter system, where FC is a fuel cell, B is a battery, 1 is a boost control unit, L is a reactor, Dll is a rectifier diode, Qll is a switching transistor, SW is a switch, LD is a load. This method has been put into practical use with a small capacity of about several hundred W, but there is no track record of a large capacity of several kilowatts or more. This is because the design and manufacture of the reactor L is technically and economically difficult. Therefore,
It is difficult to apply it to a fuel cell system of several kilowatts or more. Figure 9 shows what is commonly called the INV method, and Q12
- Q19 are transistors, 012 to 019 are diodes, C1l is a capacitor, 2 is a booster, 3 is an AC voltage controller, and 4 is an Atl knee DC rectifier. This method has a complicated circuit configuration, is large in size and weight, and is inefficient. Therefore, it is difficult to employ it in a fuel cell system. Figure 10 shows what is commonly called the chopper method, and the Q
20 and Q21 are switching transistors, D20
and 021 are diodes, C12 and C13 are capacitors, and have a configuration in which a step-down chopper 5 and a step-up chopper 6 are combined. As this method, for example, the 6th
Materials from the 9th Power Electronics Study Group regular meeting (``Output current method solar power generation maximum output tracking control device and characteristics using series-parallel choppers'' and Shigeo Takada et al., University of Tokushima) are well known. In this method, the step-up chopper 6 is used after passing through the step-down chopper 5, so the current in the 020-L-Q21 path becomes large, which increases the size of the device, reduces efficiency, and requires a control method. It is complicated because it uses a CPU. [Problems to be Solved by the Invention] Therefore, an object of the present invention is to reduce the size of the device and improve efficiency by combining the well-known boost chopper and buck chopper in the order of boosting and bucking the voltage. As intended, efficiency is further improved by operating the boost chopper only when necessary, without having to operate both the boost chopper and the buck chopper all the time.
It is also an object of the present invention to provide a power generation system that is downsized by simplifying the configuration of the control circuit. [Means for Solving the Problems 1] In order to achieve such an object, the present invention provides a power generation system comprising a power supply device and a battery.
A feature is that a step-up chopper is connected to the power supply side, and a step-down chopper is connected to the battery side. [Operation] This invention provides a power supply device connected in the order of a step-up chopper and a step-down chopper so that the output voltage V' of a power supply device with a large voltage drop characteristic such as a fuel cell or a solar cell is greater than the battery voltage VB + chopper voltage drop Δυ. When (VP≧V, +Δυ
), only the step-down chopper is operated. Conversely, Δ
When υ>Vr-Va, the boost chopper is activated to stably supply a predetermined amount of power from a power supply device, such as a fuel cell, to the battery and load. [Examples] Examples of the present invention will be described below based on the drawings. An embodiment of the present invention is shown in FIG. 1. Here,
Although a fuel cell will be described as an example of a power supply device, the present invention can be similarly applied to a solar cell. In FIG. 1, step-up chopper CHI consists of reactor L1, diode D1, and transistor Q1, and step-down chopper 082 consists of reactor L2, diode D2, and transistor Q2. C1 is a capacitor, and a boost chopper CHI is connected to the fuel cell FC, and the output of the boost chopper CHI is supplied to the buck chopper CI2 via the capacitor C1. Battery B is connected to this step-down chopper CH2. It is assumed that a load LD is connected to battery B via a switch SW. An FC voltage detector VDI is connected between the terminals of the fuel cell FC. A B voltage detector VD2 is connected between the terminals of battery B. An FC current detector SR is connected to one terminal of the current battery FC. The difference IP-IF obtained by supplying the detection output LF of the FC current detector SH and the setting output 2 from the FC current setter VRI to the subtracter 5IIB1 is converted to PWM via the amplifier Q3.
Supplied to modulator Q4. The modulation signal from the modulator Q4 is supplied to the base of the transistor Q2, and the modulation signal switches the transistor Q2 to turn on the chopper switch of the step-down chopper CH2. Do off. Difference υ obtained by supplying each detection output υ2 and υ3 of voltage detectors voi and VO2 to a subtracter 51182. -υ, is supplied to the adder ^DD1 via the amplifier Q5,
Here, a signal obtained by adding the corrected output from the ΔV setter VR2 is supplied to the PWM modulator Q6. The modulation signal from the modulator Q6 is supplied to the base of the transistor Q1 to perform switching of the transistor Q1. This turns on and off the chopper switch of boost chopper CH1. Note that Δυ is a voltage drop value generated in chopper CH1 or CH2. Here, the operation of the circuit according to the embodiment of the present invention shown in FIG. 1 will be explained with reference to FIGS. 2 to 5. FIG. 2 is a modeling operation diagram of the circuit of FIG. 1. In Figure 6, the efficiency of choppers CHI and CH2 is set to 100.
%, since v, x I, = V, x IcH, ICH = VPX IF/VB, and as shown in Fig. 1, even if constant current control is performed on step-down chopper CH2, , the output current I of the step-down chopper CH2
CH changes as follows. Note that IL represents load current. When the load LD is in a steady state: ICH= (-Ia) ◆■ This means that only -Ia is charged. When the load LD is at its peak: IL=IcH+ (+l11) This means that only ◆I6 is discharged. In case of no load (switch SW open): ICH=(-In) This means charging with full ICH current. FIG. 3 shows the voltage-current characteristics of fuel cell FC and battery B. In FIG. 3, when the load LD is in a steady state, the current 0-a
Since tr constant current control is performed during this period, current 0 to a' = 0 to a flows through battery B, and current a-b flows through load LD. Here, 11:H-VFX Ir/Va=Icu”(-1a)
becomes. If the voltage of battery B at this time is VBa'≦V, -ΔV, then α: conductivity of transistor Q2 of buck chopper CI2 Rε: total resistance on the output side of buck chopper CH2; ■2 Constant control is performed by step-down operation. If we now assume that there is no load from this state, IcH-0
-b current is all battery B charging current -), =Q-b
'The battery voltage moves on the line ■v3 and increases. In other words, ■At the 0 point of Va, the transistor Q2 becomes fully conductive and becomes the limit value at which I, force (-) can flow.If Va further increases to point a, IF constant current control is no longer possible from the previous equation. Here, to explain the operation of the circuit shown in Figure 1 with reference to Figures 4 and 5, the input signal is υ.If VB is + and VB is -, then the input signal of amplifier Q5 is is V,
-VB, and as a result, the output signal S1 of the transistor QI in FIG. 5 can be obtained. That is, υ
It is arranged so that when it becomes p-VB, it passes through a. For this purpose, the chopper CH
If the voltage drop Δυ of I and CH2 is set, the human input signal S2 of the modulator Q6 will become as shown in FIG.
The signal becomes 10 from point b, generates a PIIIM chopping signal as the output signal S3 of the modulator Q6, and activates the transistor Q+ of the chopper CHI. As a result, the boost chopper CI starts boosting operation. According to such a configuration, when υ,)υ8+Δυ, the boost chopper CHI does not operate, and FC→Ll-DI-CH
2, a predetermined power is supplied to battery B or load LD. On the other hand, when v2≦υ, ◆ΔV, as mentioned above, the step-up chopper CH is activated, so the terminal voltage VC of the capacitor C1 in FIG.
The human power of H, becomes Vc>Va+ΔυCH2, and the step-down chopper CH2 can operate stably. Therefore, a predetermined amount of power can be continuously supplied to battery B or load LD. FIG. 6 and FIG. 7 show the operation when battery B is charged by the fuel cell FC in the conventional example and the present invention, respectively. Here, consider a case where battery B is being charged, voltage VB gradually increases, the state of charge approaches 100% in a stepwise manner, and the charging current is gradually lowered. In the conventional example shown in FIG. 6, depending on the state of charge of battery B,
Current I as In+ -IB2-1as-1e4. To lower the value of , use the FC current setting device VR.
Lower the I setting. Therefore, the FC output current decreases, and as a result, the I/ν characteristic VF in FIG.
The FC voltage increases as shown in F2-VF6-VF6 d'). On the other hand, in the present invention, as shown in FIG. 7, as battery B is charged with I1 (αIr+), the voltage VB of battery B gradually increases, and at point a, the boost chopper CI, operates and increases the voltage vc between the terminals of the capacitor C1, thereby ensuring stable operation of the step-down chopper CH2, and as a result, the I2 current becomes a constant current. In this way, 1112 (αIP2
)・”In5(αI, ri...I!14(αI, 4)) and completes charging of battery B. [Effects of the Invention] As is clear from the above, according to the present invention, By connecting these choppers in the order of step-up chopper to step-down chopper between a power supply device such as a fuel cell or a solar cell and a battery, chopper losses are reduced, and
By monitoring the voltage V of the power supply device and the voltage of the battery and activating the boost chopper only when the two come close to each other, the efficiency can be further improved.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a modeled operation diagram thereof, Fig. 3 is a voltage-current characteristic diagram of a fuel cell and battery, and Fig. 4 is a control of boost chopper CH. An explanatory diagram of the circuit; FIG. 5 is an explanatory diagram of the operation of the control circuit of the boost chopper CH; FIG. 6 is an explanatory diagram of the operation during conventional battery charging; FIG. 7 is an explanatory diagram of the operation during battery charging in the present invention; FC-...Fuel cell, B...Battery, SW-...Switch, LD...Load, CHI...Step-up chopper, CH2...Step-down chopper, Ll, L2-...Reactor, Ql, Q2 ...Switching transistor, Q3. Q
5...Amplifier, Q4. Q6-...PWM modulator, DI, 02...diode, CI...capacitor, VDI...-FC voltage detector, VO2...B voltage detector, SH---FC current detector, VRI ...FC current setter, VB2...∆υ setter, 5UBI, 50B2...subtractor, ADDI...adder. Schematic diagram of main scabbard Akiyacho Asahi flJ Fig. 1 Mon. Cow IJ and P times Luxury concave Figure 4 CHI Half+j Made P times! Kai) F = Button Meimei Map Figure 5 A Shiba Yoneri River's Hatsunari Full Words and Scolding Jukai ￥ - Tsuba Shikimei Map Figure 6 F4 Things 2 Clearly 7-b ＼゛Tsuderi tρ Sinking Figure 8 Figure 8

Claims (1)

[Claims] 1) In a power generation system composed of a power supply device and a battery, a boost chopper is connected to the side of the power supply device,
A power generation system characterized in that a step-down chopper is connected to the battery side. 2) In the power generation system according to claim 1, the capacitor disposed on the output side of the step-up chopper and the capacitor disposed on the input side of the step-down chopper are shared by one capacitor. , A power generation system characterized in that the step-up chopper and the step-down chopper are connected.