JPH08308290A - Linkage inverter - Google Patents

Abstract

PURPOSE: To provide a linkage inverter which can always operate a system having an engine generator, a DC power source, and the linkage inverter in the maximum efficiency. CONSTITUTION: The linkage inverter comprises a fuel detector 21 for detecting the fuel consumption amount of an engine generator 6, a DC power source output detector 22 for detecting the output power of a DC power source 8, a load power detector 23 for detecting the power consumption of a load 7, and am efficiency calculator 24 for calculating the system efficiency from the outputs of these three detectors 21 to 23, wherein the shared amounts of the basic wave and the harmonic wave of the generator 6 and the inverter A can be varied according to the system efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for interconnecting an engine generator and a DC power source, and more particularly to an interconnected inverter device for effectively utilizing the energy of the engine generator and the energy of the DC power source.

[0002]

2. Description of the Related Art A conventional system of this type is shown in FIG. In the figure, C is a conventional interconnection inverter device, 1 is an inverter, 2 is a PWM circuit, 3 is a voltage synchronization signal generation circuit,
4 is a voltage synchronous oscillator, 5 is a multiplier, 6 is an engine generator, 7 is an AC load, 8 is a DC power supply, 9 is an adder, 10 is a multiplier, 11 is a subtractor, 12 is a current synchronous oscillator, and 13 is It is a bandpass filter.

The operation of the conventional interconnection inverter device C will be described below with reference to the drawings. Current synchronous oscillator 12
Bandpass filter 13 in detects the load current I _load, and outputs a load current fundamental signal I _{the If} consisting of only the fundamental wave component of the load current I _load. Load current fundamental wave signal I
_If is compared and subtracted with the load current I _load by the subtractor 11, and the load current harmonic signal I _Ih is obtained. The load current harmonic signal I _Ih is calculated by multiplying the preset harmonic sharing ratio Kh and the multiplier 10
To obtain the harmonic compensation signal I _Ch .

The voltage synchronous oscillator 4 in the voltage synchronous signal generating circuit 3 detects the output voltage V _ENG of the engine generator 6,
A reference sinusoidal wave SIN having a sinusoidal waveform having the same frequency and phase as the fundamental wave component is generated. The reference sine wave SIN is multiplied by a preset amplitude command value Kp in the multiplier 5 to obtain a current command value I _r of the fundamental wave component of the inverter output. The current command value I _r is added to the harmonic compensation signal I _Ch by the adder 9 to obtain the current command signal I _Cr . PWM circuit 2, equal current command signal I _Cr and polarity current command signal switch drive signal PWM having a pulse width proportional to the absolute value of I _Cr
Occurs.

The inverter 1 receives the DC voltage V _DC output from the DC power supply 8, operates the main switch according to the switch drive signal PWM, and outputs an inverter output current I _INV having a waveform similar to the current command signal I _Cr. appear.

By the above operation, the inverter output current I
_INV is a current obtained by adding the fundamental wave component synchronized with the fundamental wave component of the output voltage V _ENG of the engine generator 6 and the harmonic component of the load current I _load . Further, the output current of the engine generator 6 is a current obtained by adding the fundamental wave component and the harmonic component. Therefore, even if a non-linear load such as a capacitor input type is connected as the AC load 7, the harmonic component contained in the output current of the engine generator 6 can be reduced. As a result, the rated output of the engine generator 6,
By appropriately setting the amplitude command value Kp of the fundamental wave and the harmonic share ratio Kh in advance according to the standard value of the equivalent negative phase current and the harmonic current value flowing in the AC load, the standard of the equivalent negative phase current of the engine generator 6 is set. The value can be easily satisfied, and the engine generator 6
The rated output of can be secured.

[0007]

FIG. 5A shows the power generation efficiency characteristics of a fuel cell, for example, which can be used as the DC power source 8. The power generation voltage of the fuel cell decreases with the power generation current, and the fuel flow rate depends only on the power generation current. _Therefore , the power generation efficiency η _FUEL
Is a property that has a maximum value. It can also be considered as the engine generator 6. For example, the power generation efficiency η _ENG of the gas engine generator increases as it approaches the rated value as shown in FIG. 5 (b).

Considering a conventional system including a fuel cell having a power generation efficiency characteristic shown in FIGS. 5A and 5B, a gas engine generator, and an interconnection inverter, a fuel cell and a gas engine generator are considered. The output rated values are equal and the AC load power consumption is 1.5 times the output rated value of the fuel cell. In this case, the load factor of the fuel cell and the gas engine generator can be set from 50% to 100%, and the respective power generation efficiencies η _FUEL and η _ENG and the system efficiency η _SYS are shown in FIG. 6 (a). Next, assuming that the AC load power consumption decreases to 1.2 times the rated output value of the fuel cell, FIG.
Changes from FIG. 6 (b).

6 (a) and 6 (b), the system efficiency has the maximum value, but in the case of FIG. 6 (a), the maximum value A is the load factor of the gas engine generator (the output of the gas engine generator). Value / rated output value of gas engine generator) is 83%, that is, load sharing ratio (output value of gas engine generator / output value of gas engine generator + output value of fuel cell) is 60%,
In the case of FIG. 6B, the maximum value B is such that the load factor of the gas engine generator changes to 40%, that is, the load sharing factor changes to 33%.

However, in the case of the conventional interconnected inverter device, since the load sharing ratio is fixed, it is not always possible to operate at maximum system efficiency. The present invention has been made in view of the above circumstances, and an object thereof is to provide a grid-connected inverter device that can always operate a system including an engine generator, a DC power supply, and a grid-connected inverter device with maximum efficiency. .

[0011]

The above-mentioned problems can be solved by adopting the following novel characteristic constitutional means of the present invention. That is, the features of the present invention are a fuel detection circuit that detects the amount of fuel consumed by the engine generator, a DC power supply output detection circuit that detects the output power of the DC power supply, and a load power detection circuit that detects the power consumption of the load. A characteristic calculation circuit that calculates the system efficiency from the outputs of these three detection circuits is provided, and it is possible to change the sharing amount of the fundamental wave and the harmonic wave of the engine generator and the interconnection inverter device depending on the system efficiency. The point is that it has a structure.

Specifically, the invention is an interconnected inverter device having an input end connected to a DC power supply and an output end connected in parallel with an AC load to an engine generator, wherein a fundamental wave of an output voltage of the engine generator is provided. Voltage synchronization signal generating circuit that generates a sinusoidal current command value having an amplitude equal to the amplitude command value, and a load current fundamental wave signal consisting of only the fundamental wave component of the load current flowing into the AC load. , A subtractor that subtracts the load current fundamental wave signal from the load current, a multiplier that multiplies the output signal of the subtractor by a harmonic share ratio, and an output signal of the multiplier An adder for adding the current command values generated by the voltage synchronization signal generation circuit is provided, and the output signal of the adder is used as a current command signal, and the polarity is the same as that of the current command signal, and the current command signal In the interconnection inverter device including a control circuit including a PWM circuit that generates a switch drive signal having a pulse width proportional to a logarithmic value, and an inverter that drives a main switch according to the switch drive signal, the control The circuit is equipped with a fuel detection circuit for detecting the amount of fuel consumed by the engine generator, a DC power supply output detection circuit for detecting the output power of the DC power supply, and a load power detection circuit for detecting the power consumption of the load. A fuel consumption value that is the output of the detection circuit, a DC power supply output value that is the output of the DC power supply output detection circuit, and an efficiency calculation circuit that calculates the system efficiency by the load power consumption value that is the output of the load power detection circuit, The current command value of the sine waveform and the harmonic share are changed by the output of the efficiency calculation circuit,
The interconnected inverter device is characterized by controlling so that the output of the efficiency calculation circuit becomes maximum. Also, in the above-mentioned interconnection inverter device, the efficiency calculation circuit is configured by a neural network circuit.

[0013]

Since the present invention takes the above-mentioned novel means, it is possible to always operate the system including the engine generator, the DC power source and the interconnection inverter device with maximum efficiency.

[0014]

【Example】

[Embodiment 1] Embodiment 1 of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of the first embodiment. In the figure, A is the interconnection inverter device of the first embodiment, the input end of which is connected to the DC power supply 8 and the output end of which is connected in parallel with the AC load 7 to the engine generator 6. 21 is a fuel detection circuit, 2
2 is a DC power output detection circuit, 23 is a load power detection circuit,
Reference numeral 24 is an efficiency calculation circuit, 25 is a memory, and 26 is an arithmetic circuit. FIG. 2 is a principle diagram for maximizing system efficiency. The same parts as those in the conventional example will be designated by the same reference numerals, and duplicate description will be omitted.

The operation of the interconnection inverter device A according to the first embodiment will be described below with reference to FIG. The fuel detection circuit 21 detects the fuel consumption amount F′uel of the engine generator 6 and outputs the fuel consumption value F′u to the efficiency calculation circuit 24.
In the DC power supply output detection circuit 22, the output current I ′ of the DC power supply
By detecting the _DC output voltage V _DC 'calculates the _DC, the DC power supply output values W' DC power supply output value W and outputs the _DC to efficiently calculating circuit 24. In the load power detection circuit 23, the load current I
_Load power consumption value W ′ by detecting _load and load voltage V _{ENG
The load} is calculated and the load power consumption value W ′ _load is output to the efficiency calculation circuit 24. In the efficiency calculation circuit 24, the DC power supply output value _W'DC and the power generation efficiency of the DC power supply according to the DC power supply output value stored in the memory 25 in advance are multiplied by the arithmetic circuit 26 to calculate the energy consumption of the DC power supply. . further,
The system efficiency Q'is obtained by dividing the _load power consumption value W'load by a value obtained by adding the energy consumption of the DC power source and the fuel consumption value F'u in the arithmetic circuit 26. The harmonic sharing rate K'h and the amplitude command value K'p are determined by the obtained system efficiency Q'and the _load power consumption value W'load, and the harmonic sharing rate K'h is output to the multiplier 10 to output the amplitude command. The value K′p is output to the multiplier 5.

On the other hand, the bandpass filter 13 in the current synchronous oscillator 12 detects the load current I _load and detects the load current I load.
load current fundamental signal I _{the If} consisting of only the fundamental wave component of the _load
Is output. The load current fundamental wave signal I _If is input to the subtractor 11, and the subtracter 11 subtracts the load current fundamental wave signal I _If from the load current I _load to obtain the load current harmonic signal I _Ih . The load current harmonic signal I _Ih is multiplied by the harmonic share ratio K′h output from the efficiency calculation circuit 24 in the multiplier 10 to obtain a harmonic compensation signal I ′ _Ch .

The voltage-synchronized oscillator 4 in the voltage-synchronized signal generating circuit 3 generates a reference sine wave SIN having a sine waveform of amplitude 1 whose frequency and phase are equal to the fundamental wave component of the output voltage V _ENG of the engine generator 6. The reference sine wave SIN is multiplied by the amplitude command value K′p output from the efficiency calculation circuit 24 in the multiplier 5, synchronized with the fundamental wave component of the output voltage of the engine generator 6, and the amplitude command value K ′. current command value I _'r sine waveform having an amplitude equal to p are obtained. Current command value I _'r is the harmonic compensation signal I' is added by the adder 9 and _Ch, to obtain a current command signal I _'Cr. PWM circuit 2, the current command signal I _'Cr and polarity equal to the current command signal I' switch drive signal P having a pulse width proportional to the absolute value of _Cr
Generate WM '.

The inverter 1 receives the DC voltage V _DC output from the DC power source 8 as an input, and receives the switch drive signal PWM '.
According to operate the main switch to generate _INV 'inverter output current I having a waveform similar to the _Cr' of the current command signal I.

[0019] The by the output efficiency calculation circuit 24 to change the current command value I _'r and the harmonic sharing rate K'h of the sine wave, the output of said efficiency calculating circuit 24 is controlled to be maximum.

FIG. 2 shows a method of obtaining the harmonic share rate K'h and the amplitude command value K'p from the system efficiency Q'and the _load power consumption value W'load for operating the system at maximum efficiency. This will be described in detail using a flowchart.

At time t-Δt, it is assumed that the system is operated at the maximum efficiency by the following method, and Δt
After that, that is, a method of obtaining the harmonic share rate K'h and the amplitude command value K'p from the time t will be described.

Load power consumption value W'at time t
_load (t) and active power value W ′ _{load at} time t−Δt
When (t−Δt) is compared and equal, the harmonic share K′h (t) equal to the harmonic share K′h (t−Δt) at time t−Δt is output to the multiplier 10. Time t-Δ
An amplitude command value K′p (t) equal to the amplitude command value K′p (t−Δt) at t is output to the multiplier 5.

If they are different, the harmonic share K'h (t) obtained by adding α to the harmonic share K'h (t-Δt) at the time t-Δt is output to the multiplier 10, and the time t-Δt is obtained. The amplitude command value K'p (t) equal to the amplitude command value K'p (t- [Delta] t) is output to the multiplier 5. Next, the system efficiency after the time Δt is compared with the system efficiency at the time t, and when the system efficiency after the time Δt is large, α is further added to the harmonic share K′h (t−Δt) before the time Δt. The added harmonic share K'h (t) is output to the multiplier 10, and the amplitude command value K'p (t) equal to the amplitude command value K'p (t-Δt) before the time Δt is supplied to the multiplier 5. Output and repeat until system efficiency drops.

If it is small, the harmonic share K'h (t) obtained by subtracting α from the harmonic share K'h (t-Δt) before the time Δt is output to the multiplier 10, and the amplitude before the time Δt is output. Amplitude command value K'equal to command value K'p (t-Δt)
It outputs p (t) to the multiplier 5 and repeats until the system efficiency decreases.

When the system efficiency decreases, the higher harmonic sharing rate K'h (t-2Δt) is fixed. next,
The harmonic share is fixed, and the amplitude command value is changed and fixed in the same manner as in the process of fixing the harmonic share. With the fixed harmonic share K'h (t-2Δt) and the amplitude command value K'p (t-2Δt), the system efficiency can be maximized.

By making the cycle Δt for calculating the system efficiency sufficiently smaller than the cycle in which the load power consumption value changes, it is possible to always maximize the system efficiency before the load power consumption value changes, and the harmonic share ratio and the amplitude command. Needless to say, it can be set to a value and the system will always operate at maximum efficiency.

[Second Embodiment] A second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing the configuration of the second embodiment. In the figure, B is the interconnection inverter device of the second embodiment,
Reference numeral 31 is a neural network circuit which constitutes an efficiency calculation circuit. The same parts as those in the first embodiment are designated by the same reference numerals, and the duplicated description will be omitted.

The neural network circuit 31, fuel consumption value which is the output of the fuel detection circuit 21 F'u, the output of the DC power supply output values W _'DC, which is the output of the DC power supply output detection circuit 22 load power detecting circuit 23 Certain load power consumption value W '
Enter _load . Then, previously learned in advance fuel consumption value F'u was, the DC power supply output values W _'DC and the load power consumption value W'
Harmonic contribution ratio K'that maximizes _load and system efficiency
From the relationship between h and the amplitude command value K'p, the harmonic share rate K'h and the amplitude command value K'p that can maximize the system efficiency are determined, and the harmonic share rate K'h is output to the multiplier 10. The amplitude command value K′p is output to the multiplier 5. Neural network circuit 31, such as in the preliminary experiment and the device data, fuel consumption value F'u, the DC power supply output values W _'DC and the load power consumption value W' _load and harmonics sharing ratio K of the system efficiency can be maximized ' h, by previously learning the relation between the amplitude command k'P, harmonics can be consumed fuel value F'u input from the DC power supply output values W _'DC and the load power consumption value W' _load to maximize system efficiency Sharing ratio K'h and amplitude command value K'p
Can be output.

The operation other than the above is the same as the operation described in the first embodiment, and the description thereof will be omitted. Since the off-line learned neural network can be configured by a digital signal processor (DSP), it can be integrated into one chip and the control circuit can be downsized. Further, since it is not necessary to execute the calculation based on the flowchart as shown in FIG. 2, the harmonic share K'h and the amplitude command value K'that can maximize the system efficiency.
Since p can be obtained at high speed, the system operating cost can be further reduced.

[0030]

As described above, according to the present invention, the system including the engine generator, the DC power source, and the interconnection inverter device can be operated at the maximum efficiency, and the fuel consumption of the engine generator and the DC It is possible to reduce the fuel consumption of fuel cells and the like that can be used as a power source. Therefore, the operating cost of the system can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

2 is a flowchart for operating the system of FIG. 1 with maximum efficiency.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional interconnected inverter device.

5 (a) is a characteristic diagram showing power generation efficiency of a fuel cell. FIG. (B) It is a characteristic view which shows the power generation efficiency of a gas engine generator.

FIG. 6 is a characteristic diagram showing the efficiency of a system including a gas engine generator, a fuel cell, and an interconnection inverter device.

[Explanation of symbols]

A, B, C ... Connected inverter device 1 ... Inverter 2 ... PWM
Circuit 3 Voltage synchronous signal generation circuit 4 Voltage synchronous oscillator 5, 10 Multiplier 6 Engine generator 7 AC load 8 DC power source 9 Adder 11 Subtractor 12 Current synchronous oscillator 13 Bandpass filter 21 ... Fuel detection circuit 22 ... DC power supply output detection circuit 23 ... Load power detection circuit 24 ... Efficiency calculation circuit 25 ... Memory 26 ... Operation circuit 31 ... Neural network circuit

Claims (2)

[Claims] 1. An interconnected inverter device having an input end connected to a DC power source and an output end connected in parallel with an AC load to an engine generator, the synchronous inverter device being synchronized with a fundamental wave component of an output voltage of the engine generator. Then
And a voltage synchronization signal generation circuit that generates a sinusoidal current command value having an amplitude equal to the amplitude command value, and a current synchronization that outputs a load current fundamental wave signal consisting of only the fundamental wave component of the load current flowing into the AC load. An oscillator, a subtractor for subtracting the load current fundamental wave signal from the load current, a multiplier for multiplying the output signal of the subtractor by a harmonic share ratio, and a voltage synchronization signal generation for the output signal of the multiplier A pulse having an adder for adding the current command value generated by the circuit, the output signal of the adder being a current command signal, having the same polarity as the current command signal, and being proportional to the absolute value of the current command signal PWM for generating a switch drive signal having a width
A control circuit including a control circuit and an inverter that drives a main switch in response to the switch drive signal, wherein the control circuit includes a fuel detection circuit that detects a fuel consumption amount of an engine generator. A DC power supply output detection circuit for detecting the output power of the DC power supply, and a load power detection circuit for detecting the power consumption of the load, the fuel consumption value output from the fuel detection circuit, the DC power supply output detection circuit A DC power supply output value that is the output of the load power detection circuit and a load power consumption value that is the output of the load power detection circuit, and an efficiency calculation circuit that calculates the system efficiency. An interconnected inverter device, characterized in that a harmonic allocation ratio is changed and control is performed so that an output of the efficiency calculation circuit becomes maximum. 2. The interconnected inverter device according to claim 1, wherein the efficiency calculation circuit comprises a neural network circuit.