JPH07200082A - Control method for maximum power followup control power converter and maximum power followup control power converter - Google Patents

Abstract

PURPOSE:To maintain a function as a switching power conversion circuit at all times by deciding the switching frequency of the switching power conversion circuit by the modulation frequency of a pulse width modulation circuit. CONSTITUTION:The pulse width modulation circuit 5m' inputs an on-duty ratio Dp(K+1) from an on-duty ratio command signal generation circuit 5j', performs the pulse width modulation of on-duty ratio command signals Dp with a sufficiently high modulation frequency and generates high frequency switch on/off command signals HFSHL provided with a pulse width proportional to the voltage ratio of the on-duty ratio command signals Dp. In this case, a driving circuit 5f' amplifies the high frequency switch on/off command signals HFSHL, generates switch driving signals PHL and drives a semiconductor switch inside the switching power conversion circuit 2. Thus, the function as the switching power conversion circuit 2 is maintained at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a maximum power follow-up control power for maximizing the generated power of a power generator by connecting to the output end of a power generator for charging a storage battery or a power generator for interconnected operation. The present invention relates to a control method of a converter and a maximum power tracking control power converter directly used for its implementation.

[0002]

2. Description of the Related Art A block diagram of a conventional maximum power tracking control power converter is shown in FIG. In the figure, A is a conventional maximum power tracking control power conversion device, 1 is a power generation device, 2 is a switching power conversion circuit, 3 is an input voltage detection circuit, 4 is an input current detection circuit, 5 is an input power calculation circuit 5a, and a current. Differentiator circuit 5
b, a power differentiation circuit 5c, a multiplier 5d, a comparator 5e, and a control circuit 5f, and 6a and 6b are output terminals.

The operation of the conventional maximum power tracking control power converter A is as follows. First, the input voltage detection circuit 3 detects the input voltage V of the switching power conversion circuit 2 and generates the input voltage signal Vs. The input current detection circuit 4 detects the input current I of the switching power conversion circuit 2 and generates an input current signal Is.

The input power calculation circuit 5a in the control circuit 5 is
The input voltage signal Vs from the input voltage detection circuit 3 and the input current signal Is from the input current detection circuit 4 generate an input power signal Ws.

The current differentiating circuit 5b performs a differential operation on the input current signal Is and outputs an input current differential signal dIs / dt. The power differentiating circuit 5c performs a differential operation on the input power signal Ws and outputs the input power differential signal dWs / dt.

The input current differential signal dIs / dt and the input power differential signal dWs / dt are multiplied by the multiplier 5d to generate a multiplication signal Mws, which is input to the comparator 5e. Comparator 5e
In, a switch-on / off signal SHL is generated which is turned on when the multiplication signal Mws is positive and is turned off when the multiplication signal Mws is negative.

The drive circuit 5f amplifies the switch on / off signal SHL from the comparator 5e and generates a switch drive signal PHL to drive the semiconductor switch 2a in the switching power conversion circuit 2.

Here, an example of the generated current-generated power correlation characteristic of the power generator 1 is shown in FIG. The maximum power follow-up control power converter A shown in FIG. 7 has a characteristic that the generated power has an extreme value Wmax with respect to the generated current as shown in FIG.
When the multiplication signal Mws is positive, that is, when the operating point of the input current and the input power of the switching power conversion circuit 2 (= the generated current and the generated power of the power generator 1) is on the left side of the optimum current Iopt. When it is, the semiconductor switch 2a of the switching power conversion circuit 2 is turned on.

On the contrary, when the operating point of the input current and the input power of the switching power conversion circuit (= the generated current and the generated power of the generator 1) is in the region on the right side of the optimum current Iopt, the switching power conversion circuit 2 The semiconductor switch 2a is turned off.

By operating in this manner, the operating points of the input current and the input power of the switching power conversion circuit 2 are
Since the power generator 1 is always moved toward the optimum power generation point (Iopt, Wmax), the power generator 1 can be operated near the optimum power generation point.

[0011]

However, the conventional maximum power tracking control power converter A has the following problems. That is, when applied to a device such as a solar cell in which the response of the input power (= generated power) to the ON or OFF operation of the semiconductor switch 2a is on the order of microseconds, the switching power conversion circuit 2 is close to the optimum power generation point. High-frequency on / off operation can be performed, input current and voltage (= generated current and generated voltage) can be easily controlled, and desired control can be easily performed.

However, when applied to a power generator using a heat engine or the like, which has a very slow response of input power (= generated power) to the ON or OFF operation of the semiconductor switch 2a, such as a second order, the switching frequency is abnormal. Therefore, the function as the switching power conversion circuit 2 may be impaired.

Further, since there is a very small change with time in the input voltage and the current (= the generated voltage and the current), there is a problem that a malfunction occurs due to the influence of noise or the like and a desired control effect cannot be obtained.

In view of the problems of the conventional device, the present invention provides a maximum power tracking control power conversion device that can follow the response of the power generation device on the order of seconds without impairing the function of the switching power conversion circuit. A control method and a maximum power tracking control power conversion device are provided.

[0015]

The solution of the above-mentioned problems can be achieved by adopting the novel characteristic construction method and means listed in the following by the present invention. That is, the feature of the method of the present invention is that a switching power conversion circuit, an input voltage detection circuit that detects an input voltage of the switching power conversion circuit to generate an input voltage signal, and an input current of the switching power conversion circuit are detected. Input current detection circuit for generating an input current signal by means of the input voltage signal from the input voltage detection circuit and the input current signal from the input current circuit In controlling the maximum power tracking control power conversion device configured by a control circuit that outputs a drive signal for operating so that the input power of the switching power conversion circuit becomes a maximum value, first, in the control circuit, , Multiplying the input power signal by the input voltage signal and the input current signal, and then from the input power signal every arbitrary period Obtaining the discretized discretized input power signal, and then subtracting the discretized input power signal detected one period before the arbitrary period from the discretized input power signal to calculate the discretized input power difference signal, and , Detecting an on-duty ratio of a switch of the switching power conversion circuit main circuit for each of the arbitrary cycles to calculate a discretized on-duty ratio signal, and
The discretized on-duty ratio difference signal is calculated by subtracting the discretized on-duty ratio signal detected one cycle before the arbitrary period from the discretized on-duty ratio signal, and further calculating the discretized on-duty ratio difference signal. The on-duty ratio increase / decrease command signal is obtained by multiplying the discretized input power difference signal, and in addition, the on-duty ratio is increased / decreased according to the polarity of the on-duty ratio increase / decrease command signal, and finally, the arbitrary In the control method of the maximum power follow-up control power converter that amplifies a signal obtained by pulse-width-modulating the on-duty ratio with a high-frequency modulation frequency within a cycle and operates a switch of the switching power conversion circuit main circuit. is there.

The device of the present invention is characterized by a switching power conversion circuit, an input voltage detection circuit for detecting an input voltage of the switching power conversion circuit, and generating an input voltage signal.
An input current detection circuit that detects an input current of the switching power conversion circuit to generate an input current signal, an input voltage signal from the input voltage detection circuit, and an input current signal from the input current circuit are input and operated. And a control circuit that outputs a drive signal for operating a switch of the switching power-to-power converter circuit main circuit, and controls so that the input power of the switching-to-power converter circuit becomes maximum value. In the control circuit, the control circuit calculates an input power from the input voltage signal and the input current signal, and a discretized input power discretized from the input power signal of the input power calculation circuit at every arbitrary cycle. A power signal detection circuit that calculates a signal, and one cycle before the arbitrary cycle from the discretized input power signal from the power signal detection circuit An input power difference signal arithmetic circuit that subtracts the discretized input power signal, and detects the on-duty ratio of the switch of the switching power conversion circuit main circuit at each arbitrary cycle to calculate the discretized on-duty ratio signal. An on-duty ratio difference signal arithmetic circuit for calculating a discretized on-duty ratio difference signal by subtracting the discretized on-duty ratio detected one cycle before from the arbitrary period, and the discretized on-duty ratio difference signal and the discrete signal. And a comparator that calculates and outputs an on-duty ratio increase / decrease command signal that increases / decreases the on-duty ratio according to the polarity of the multiplication signal from the multiplier. And an on-duty ratio increase / decrease command signal arithmetic circuit that receives the on-duty ratio increase / decrease command signal and calculates / outputs a pulse width modulation signal. A pulse width modulation circuit that receives the pulse width modulation signal, amplifies a signal obtained by pulse width modulating the on-duty ratio at a high frequency modulation frequency within the arbitrary period, and outputs a high frequency switch on / off signal, and the high frequency A maximum power tracking control power conversion device comprising a drive circuit for receiving a switch on / off signal and operating a switch of the switching power conversion circuit main circuit.

[0017]

Since the present invention takes the novel method and means as described above, since the switching frequency of the switching power conversion circuit is determined only by the modulation frequency of the pulse width modulation circuit, the function as the switching power conversion circuit is always maintained. It can be maintained and the generated current and generated voltage can be controlled.

Since the sampling cycle can be made infinitely long, the on-duty can be adjusted by adjusting the sampling cycle even when applied to a device having a very slow response speed such as a power generator using a heat engine. It is possible to easily detect the change in the input power, that is, the generated power due to the change in the ratio.

[0019]

(Example of Device) An example of the device of the present invention will be described with reference to the drawings. Figure 1
2 is a block diagram showing a configuration of a maximum power tracking control power conversion device of this device example, and FIG. 2 is a graph showing a drive waveform of a semiconductor switch and an input power waveform of a switching power conversion circuit, that is, a generated power waveform.

In the figure, B is a maximum power follow-up control power converter of this device example, 5'is an input power calculation circuit 5a ', a power signal detection circuit 5g', an input power difference signal calculation circuit 5h ', an on-duty ratio difference. Signal calculation circuit 5i ', multiplier 5
d ', a comparator 5e', an on-duty ratio command signal generation circuit 5j ', a pulse width modulation circuit 5m', and a drive circuit 5f '. In the figure, the same members as those in the conventional example are designated by the same reference numerals.

(Method example) The maximum power follow-up control power converter B of this device example will be described with reference to FIGS. Prior to the control of this method example, the power generator 1 is started, the input voltage detection circuit 3 detects the input voltage of the switching power conversion circuit 2, generates the input voltage signal Vs, and the input current detection circuit 4 switches. The input current I of the power conversion circuit 2 is detected and the input current signal Is is detected.
Occurs and puts.

First, the input power calculation circuit 5a 'calculates and generates the input power signal Ws from the input voltage signal Vs from the input voltage detection circuit 3 and the input current signal Is from the input current circuit 4.

Next, the power signal detection circuit 5g 'detects the input power signal Ws from the input power detection circuit 5a' at every sampling period Ts and outputs the discretized input power signal Ws (k) at time T (k). Occur.

Subsequently, the input power difference signal calculation circuit 5h '
Is the time T (k- before one sampling period from the discretized input power signal Ws (k) from the power signal detection circuit 5g '.
The discretized input power difference signal Ww (k) is generated by subtracting the discretized power signal Ws (k-1) detected in 1).

After that, the on-duty ratio difference signal calculation circuit 5i 'has an on-duty ratio command signal generation circuit 5j'.
From the on-duty ratio signal Dp (k) at the time T (k), and the on-duty ratio signal Dp (k-1) at the time T (k-1) from the on-duty ratio signal Dp (k). Then, the discretized on-duty ratio difference signal Dd (k) is generated.

In addition, the multiplier 5d 'has a discretized input power difference signal Ww from the input power difference signal calculation circuit 5h'.
(K) is multiplied by the discretized on-duty ratio difference signal Dd (k) from the on-duty ratio difference signal calculation circuit 5i 'to generate a multiplication signal Mwd (k), which is input to the comparator 5e'.

Then, the comparator 5e 'outputs the multiplication signal Mwd.
An on-duty ratio increase / decrease command signal CHL that is high when (k) is positive and is low when the multiplication signal Mwd (k) is negative
(K) is generated, and the on-duty ratio command signal generation circuit 5 is generated.
Enter in j '.

In addition, the on-duty ratio command signal generation circuit 5j 'outputs the on-duty ratio increase / decrease command signal CHL (k).
Is high, the increase / decrease command value ΔD is added to the on-duty ratio Dp (k) at time T (k) to obtain time T (k +
The on-duty ratio Dp (k + 1) in 1) is set to Dp
(K) + ΔD, on-duty ratio increase / decrease command signal CHL
When (k) is low, the increase / decrease command value ΔD is subtracted from the on-duty ratio Dp (k) at time T (k) to obtain the time T.
The on-duty ratio Dp (k + 1) at (k + 1) is generated as Dp (k) -ΔD, and the pulse width modulation circuit 5
Input in m '.

Finally, the pulse width modulation circuit 5m 'carries out pulse width modulation of the on-duty ratio command signal Dp at a sufficiently high modulation frequency and has a pulse width proportional to the voltage value of the on-duty ratio command signal Dp. A high frequency switch on / off command signal HFSHL is generated.

Therefore, the drive circuit 5f 'amplifies the high frequency switch on / off command signal HFSHL, generates the switch drive signal PHL, and drives the semiconductor switch 2a in the switching power conversion circuit 2. The main circuit of the switching power conversion circuit 2 is not limited to the single-step-down converter shown here, and any switching power conversion circuit can be applied as long as the input voltage / current can be controlled by the on-duty ratio. is there.

(Application Example) An example in which the maximum power tracking control power conversion device B of this device example and this method example are actually applied to a power device will be described with reference to the drawings. FIG. 3 is a block diagram in which the power generator is combined with the maximum power tracking control power converter B of this embodiment. In the figure, B is the maximum power tracking control power converter of this application example, 1a 'is a Stirling engine power generator which is the power generator in FIG. 1, and 1b' is a rectifier.

In this application example, a DC generator 1'which converts the AC output of the Stirling engine generator 1a 'into DC power by the rectifier 1b' is used as the generator 1, and a digital signal is used as means for executing the control algorithm. -A processor (DSP) was used. Further, as the switching power conversion circuit 2, the same one-stone step-down converter as shown in FIG. 1 was used.

FIG. 4 shows the generated current / power correlation characteristics of the Stirling engine generator 1a '. FIG. 4 shows the step response of input power, current and voltage (= generated power, current and voltage) to changes in the on-duty ratio of the switching power conversion circuit 2. Is shown in FIG.

From FIG. 4, the Stirling engine power generator 1a 'used in this application example has the maximum value of the generated power with respect to the generated current, so that the application of the maximum power tracking control power converter B'is effective. I understand. However,
As can be seen from FIG. 5, the response speed of the power generation device 1a ′ is very slow, the enactment time is about 1 second, and when the conventional maximum power tracking control power conversion device A is applied, the switching frequency is about 1 Hz. Therefore, the operation as the switching power conversion circuit 2 is practically impossible.

FIG. 6 shows the time variation of the input power, voltage and current (= generated power, voltage and current) of the switching power conversion circuit when the maximum power tracking control power conversion device B'of this application example is operated. .

The switching frequency of the switching power conversion circuit 2 is 10 kHz, and the sampling cycle is as shown in FIG.
In order to reliably detect the response of the generated power by making it longer than the set time in the step response in step 2, the increase / decrease command value ΔD is set to 8 μs (in order to suppress the oscillation of the generated power near the optimum power generation point to be small). The experiment was performed with 0.8% of the switching period).

In FIG. 6, when the switching power conversion circuit is started and when the pseudo load resistance is changed from 40% to 100%, that is, 40% of the pseudo load resistance is 100Ω as a specific numerical value. 100% when
Is 40 Ω, so when the pseudo load resistance value is reduced, the input power, that is, the generated power, is gradually increased to reach the optimum power generation point, as indicated by I in FIG.

Alternatively, when the conditions other than the optimum power generation point are changed by changing from 100% to 40%, that is, in terms of specific numerical values, in the above example, 100% of the pseudo load resistance is 40Ω. 40% is 100
Since it becomes Ω, it means that the pseudo load resistance value is increased, but even in this case, as in the part II in FIG.
It is possible to gradually increase the input power, that is, the generated power to reach the optimum power generation point (0.6 A, 48 W) in FIG. 4, and the effectiveness of this embodiment can be confirmed.

[0039]

As described above, according to the present invention, since the switching frequency of the switching power conversion circuit is determined by the modulation frequency of the pulse width modulation circuit, the function as the switching power conversion circuit can always be maintained. Becomes

Further, by adjusting the sampling period, it is possible to easily detect a change in the input power (= generated power) due to a change in the on-duty ratio, and therefore it is possible to always operate the power generator near the optimum power generation point. In addition, it exhibits excellent usefulness such as being able to always supply the maximum power when charging a storage battery or operating in an interconnected manner.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a maximum power tracking control power conversion device of an example device of the present invention.

FIG. 2 is a graph showing a drive waveform of a semiconductor switch and an input power waveform of a switching power conversion circuit, that is, a generated power waveform in the figure.

FIG. 3 is a block diagram showing a configuration of a maximum power tracking control power conversion device showing an application example of the present invention.

FIG. 4 is a graph showing a generated current / power correlation characteristic of the Stirling engine generator on the drawing.

FIG. 5 is a graph showing the step response of input power, current and voltage (= generated power, current and voltage) with respect to changes in the on-duty ratio of the switching power conversion circuit in the figure.

FIG. 6 is a graph showing changes over time in the input power, voltage and current (= generated power, voltage and current) of the switching power conversion circuit in the figure.

FIG. 7 is a block configuration diagram of a conventional maximum power tracking control power conversion device.

FIG. 8 is a graph showing an example of a generated current / power correlation characteristic of the power generator on the drawing.

[Explanation of symbols]

 A, B, B '... Maximum power tracking control power converter 1, 1' ... Generator 1a '... Stirling engine generator 1b' ... Rectifier 2 ... Switching power converter 3 ... Input voltage detector 4 ... Input current detector 5, 5 '... Control circuit 5a, 5a' ... Input power calculation circuit 5b ... Current differentiating circuit 5c ... Power differentiating circuit 5d, 5d '... Multiplier 5e, 5e' ... Comparator 5f, 5f '... Driving circuit 5g' ... Power signal detection circuit 5h '... Input power difference signal calculation circuit 5i' ... On-duty ratio difference signal calculation circuit 5j '... On-duty ratio command signal generation circuit 5m' ... Pulse width modulation circuit 6a, 6b ... Output end

Claims (2)

[Claims] 1. A switching power conversion circuit, an input voltage detection circuit for detecting an input voltage of the switching power conversion circuit to generate an input voltage signal, and an input current signal for detecting an input current of the switching power conversion circuit. Drive circuit for inputting / calculating an input current detection circuit for generating a voltage, an input voltage signal from the input voltage detection circuit and an input current signal from the input current circuit, and operating a switch of the switching power power conversion circuit main circuit. In controlling the maximum power tracking control power conversion device configured by a control circuit that outputs a signal so that the input power of the switching power conversion circuit has a maximum value, in the control circuit, first, the input voltage The input power signal is multiplied by the signal and the input current signal, and then the input power signal is discretized every arbitrary period. The input power signal is obtained, and then the discretized input power signal is subtracted from the discretized input power signal detected one cycle before the discretized input power signal to obtain the discretized input power difference signal, and then the discretized input power signal. The on-duty ratio of the switch of the switching power conversion circuit main circuit is detected for each time to calculate the discretized on-duty ratio signal, and further detected from the discretized on-duty ratio signal one cycle before the arbitrary cycle. The discretized on-duty ratio difference is calculated by subtracting the discretized on-duty ratio, and the on-duty ratio increase / decrease command signal is obtained by multiplying the discretized on-duty ratio difference signal and the discretized input power difference signal. In addition, the on-duty ratio is increased or decreased according to the polarity of the on-duty ratio increase / decrease command signal, and finally, the high frequency The method of controlling the on-duty ratio by amplifying the pulse width modulated signal at the modulation frequency, the maximum power follow-up control power conversion apparatus characterized by operating a switch of the switching power converter circuit main circuit. 2. A switching power conversion circuit, an input voltage detection circuit for detecting an input voltage of the switching power conversion circuit to generate an input voltage signal, and an input current signal for detecting an input current of the switching power conversion circuit. Drive circuit for inputting / calculating an input current detection circuit for generating a voltage, an input voltage signal from the input voltage detection circuit and an input current signal from the input current circuit, and operating a switch of the switching power power conversion circuit main circuit. In a maximum power tracking control power conversion device configured to include a control circuit that outputs a signal and controlling the input power of the switching power conversion circuit to a maximum value, the control circuit includes the input voltage signal and the input current signal. An input power calculation circuit that calculates the input power by and the input power signal of the input power calculation circuit at every arbitrary cycle A power signal detection circuit that calculates a dispersed discretized input power signal, and an input power that subtracts the discretized input power signal detected one cycle before the arbitrary period from the discretized input power signal from the power signal detection circuit. A differential signal arithmetic circuit, and detects the on-duty ratio of the switch of the switching power conversion circuit main circuit at every arbitrary cycle to calculate a discretized on-duty ratio signal, and then detects one cycle before the arbitrary cycle. An on-duty ratio difference signal arithmetic circuit that calculates the discretized on-duty ratio difference signal by subtracting the discretized on-duty ratio, and a multiplication signal by multiplying the discretized on-duty ratio difference signal by the discretized input power difference signal. And a on-duty ratio increase / decrease command signal that increases / decreases the on-duty ratio according to the polarity of the multiplication signal from the multiplier.・ A comparator to output, an on-duty ratio increase / decrease command signal arithmetic circuit that calculates and outputs a pulse width modulation signal by receiving the on-duty ratio increase / decrease command signal, and the above-mentioned arbitrary cycle upon receiving the pulse width modulation signal Within
A pulse width modulation circuit that amplifies a signal obtained by pulse-width modulating the on-duty ratio at a high-frequency modulation frequency and outputs a high-frequency switch on-off signal, and a switch of the switching power conversion circuit main circuit that receives the high-frequency switch on-off signal And a drive circuit for operating the maximum power tracking control power conversion device.