JPS58201577A - Inverter device - Google Patents

Abstract

PURPOSE:To reduce the power loss of an inverter device by switching from power supply to a load by a converter circuit to power supply to the load by a commercial power supply when the demand power for the load varies from the prescribed value or larger. CONSTITUTION:A converter 6 converts DC power to AC power and supplies power to a load from a load terminal 15. The load current is detected by a current transformer 16, and when it is judged by a comparator 17 so that the demand power is larger than the reference value, a switch 10 is opened and a switch 13 is closed by the drive signal from a switch drive unit 21. Thus, the power supply to the load by the converter 6 is switched to the power supply to the load from a commercial power supply, the converter 6 becomes no load operation state, and the converter 6 has a drooping characteristic by a regulation signal from a regulator 25.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter device, and an object of the present invention is to reduce power loss by reducing the output of a conversion circuit section in a no-load operation state when a commercial power supply section supplies power to a load. do.

Generally, DC power is generated by solar cells.

Alternatively, in a so-called private power generation and distribution device that converts DC power etc. from a fuel cell into AC power and supplies power to a power load system such as lighting in a private residence, there is a large temporal change in the power demand of the power load system. The ratio of the average power demand to the maximum power demand during the day.

In other words, since the daily load factor becomes small, if the inverter device that converts DC power to AC power is designed so that the rated power of the inverter device allows the maximum power demand in one day, the inverter device converts DC power into AC power for most of the day. The required power of the band becomes smaller than the rated power of the inverter device, and the operating efficiency of the impark device decreases.

Therefore, if the inverter device is designed so that the rated power of the inverter device is smaller than the maximum power demand and is equal to the average daily power demand, for example, and the power demand of the load system exceeds the rated power of the inverter device, 2. Description of the Related Art In order to improve the operating efficiency of an inverter device, the power source is switched so that commercial power is supplied to a load from a normal commercial power supply section.

However, if the rated power of the inverter device is lowered, overload operation conditions where the demand power exceeds the rated power frequently occur, and the power supply from the inverter device to the power supply from the commercial power supply system is frequently switched. Therefore, while commercial power is being supplied to the load, the inverter is in a no-load operation state in order to prepare for fluctuations in the demand power below the rated power. Since the inverter is operated at the rated value even in the operating state, there is a drawback that the power loss of the inverter device increases during no-load operation.

This invention was made with the above points in mind,
a conversion circuit unit that converts DC power into AC power and supplies it to a load; a commercial power supply unit that supplies commercial power to the load; a detection unit that is installed in a load line and detects the power demand of the load; a control unit that switches the power supply from the conversion circuit unit to the commercial power supply unit to supply power to the load and reduces the output of the conversion circuit unit when the demand power detected by the detection unit fluctuates above a predetermined value; The present invention provides an inverter device characterized by the following features.

Therefore, according to the inverter device of the present invention, when the power demand of the load fluctuates above a predetermined value, the control unit changes the power supply from the conversion circuit unit to the load to the commercial power supply unit from supplying power to the load. In addition, when the commercial power supply unit supplies power to the load, the output of the conversion circuit unit in the no-load operation state can be reduced, and power loss can be reduced.

Next, this invention will be explained in detail with reference to drawings showing one embodiment thereof.

(1) is the first terminal which is the output terminal of a lead-acid battery that stores the electromotive force of a solar cell (not shown), and (2) has one end connected to the first armature (1) and is activated when overcurrent flows. 1st to open the circuit
breaker, (3) is a switch for turning on DC power, one end of which is connected to the other end of the first breaker (2), and (4) is a first reactor, one end of which is connected to the other end of the switch (3). ,(5)
has one end connected to the other end of the 117th actor (4) and the first
The first component that constitutes an input filter together with the reactor (4)
The capacitor (6) is a modulation circuit section whose input end is connected to the other end of the first reactor (4), which consists of a bridge circuit of four switching elements and outputs a pulse width modulated square wave AC voltage. and converts DC power to AC power.

(7) is a second reactor with one end connected to the output end of the conversion circuit section (6), and (8) is a second reactor (7) with one end connected to the output end of the conversion circuit section (6).
a second capacitor connected to the other end and forming an output filter for removing harmonic components together with the second reactor (7);
(9) is a transformer whose primary coil is connected to the other end of the second reactor (7) to boost the output voltage of the conversion circuit (6), and 00 is a transformer whose one end is connected to the second coil of the transformer (9). A first switch section consisting of a switching element such as a thyristor, 0◇ is a second terminal which is an output terminal of a commercial power supply section that supplies commercial power to a load, which will be described later, and one end of α is connected to the second terminal α. A second circuit that operates and opens when overcurrent flows.
The breaker, a, has one end connected to the other end of the second breaker α, and dΦ is a second switch part consisting of a switching element such as a cyrisk, and one end of the breaker, a, is connected to the other end of the second breaker, α. Second switch part QO, α
The eighth breaker is connected to the other end of the circuit and opens when an overcurrent flows. At 0, the load terminal is connected to a plurality of load systems, and al19 is the load terminal connected to the first breaker. 2nd switch part oi
, a current transformer Q, which is a detection unit installed in the load line between the other end of a3 and the eighth breaker ■ and detects the load current ■;
7) Convert the load current ■ detected by the Fi current transformer a into a voltage signal, and convert the load current Ir into a voltage signal when the reference voltage of the first reference voltage generator Q8) matches a predetermined value. The first comparison unit αη compares the voltage signal corresponding to the detected load current with the reference voltage of the first reference voltage generation unit 08) to determine the demand. It is determined whether the power used is larger than a predetermined value corresponding to the rated power of the conversion circuit section (6).

Q'J is determined by comparing the average value of the output voltage of the secondary coil of the transformer (9) with the reference voltage of the second reference voltage generating section.
The second comparison section that outputs the comparison signal, ■υ, is the first and second switch section 01. A switch drive unit outputs a drive signal to α1, @ is a sine wave generator that outputs a sine wave modulation signal phase synchronized with the commercial frequency of the commercial power supply unit, and (C) is a carrier signal output consisting of a high frequency triangular wave. Triangular wave generator, (
(c) is a modulation unit that receives a modulation signal and a carrier signal and outputs a pulse width modulation signal (hereinafter referred to as a PWM signal) as a modulated signal; An adjustment section receives the second comparison signal and outputs an adjustment signal for adjusting the modulation degree of the m signal of the modulation section (e), which amplifies the PWM signal from the modulation section (c) and generates a control signal. This is an amplification section that outputs to the conversion circuit section (6), and the control section (A) is constituted by the circuit surrounded by the one-dot chain line in Fig. 1. When power is supplied to the load by 6), the output voltage of the conversion circuit section (6) is kept constant, and when the commercial power supply section is supplying power to the load, the conversion circuit section (6) is in a no-load operation state. output voltage is reduced.

Next, the operation of the above embodiment will be explained.

Now, for example, taking the margin factor into account and setting the power supplied to the load line when the conversion circuit section (6) outputs power equivalent to 120% of the rated power as a predetermined reference value, the first comparison section Qη calculates In response to the drive signal from the reference section Q1), the first switch section 00 is turned on and closed, and the second switch section 00 is turned off and opened, and the control signal from the amplifier section (a) is output. The modulation circuit unit (6) is operated, and the modulation circuit 5 (6) converts the DC voltage from the first terminal (1) into a pulse width modulated square wave AC voltage, and the second reactor (7 ) and the output filter of the second capacitor (8), high frequency components of the square wave AC voltage are removed and shaped into a sine wave of the commercial frequency, and the sine wave AC voltage is passed through the transformer (9).
The predetermined AC power is boosted by the first switch unit 00.
．． It is supplied to the load via the eighth breaker circuit.

At this time, the secondary voltage of the transformer (9) is detected by the second comparison section α, and an adjustment signal is output from the adjustment section (c) in response to the second comparison signal output from the wj2 comparison section 0. The modulation degree of the PWM signal of the modulation section (c) is controlled so that the secondary voltage of the transformer (9), that is, the output voltage of the conversion circuit section (6) is controlled to be constant.

Next, as shown in FIG. 2(a), the load current detected at time t1 becomes I)lr, and the first comparator Q7) determines that the demanded power is larger than the reference value. In this case, the first
The switch section 00 is turned off to open the circuit, and the second switch section α [with] is turned on to close the circuit, and the conversion circuit section (6
) is switched from the power supply to the load to the power supply from the commercial power supply section, and the conversion circuit section (6) enters a no-load operation state. ) is adjusted, and the output voltage of the conversion circuit section (6) in the no-load operation state is adjusted as shown in Fig.
) and the conversion circuit section (6
) now has a drooping characteristic, resulting in power loss in the elements of the conversion circuit section (6) during no-load operation, as well as iron loss, copper loss, and second reactor (7), ) lance (9), and Loss due to invalid theft of the capacitor (8) is reduced.

Further, as shown in FIG. 2(a), the load current l detected at time t2 becomes 1 (lr) again, and the first comparison unit Q7'
If it is determined that the required power is smaller than the predetermined value according to the rated power of the conversion circuit section (6), the first switch section 04 is turned on again by the drive signal from the switch drive section Qυ to close the circuit. At the same time, when the second switch section α is turned on and opened, the output voltage of the conversion circuit section (6) is instantaneously increased, and the conversion circuit section (6) is restarted from power supply to the load by the commercial power supply section. The control section automatically determines whether or not the demanded power is larger than a predetermined value according to the rated power of the conversion circuit section (6). When the commercial power supply is larger or smaller than the reference value, the commercial power supply section supplies power to the load and the conversion circuit section (
6), the switching of the power supply to the load is automatically performed. Note that even if the power supply source to the load is switched as described above, the load voltage is always controlled to be constant, as shown in FIG. 2(C).

Therefore, according to the embodiment, when the power demand of the load fluctuates to a predetermined value or more, the control unit (a) changes the power supply from the conversion circuit unit (6) to the load to the commercial power supply unit. In addition, when the commercial power supply unit is supplying power to the load, the output voltage of the conversion circuit unit (6) in the no-load operation state is reduced to provide a droop characteristic to the conversion circuit unit (6). It is possible to reduce power loss in the elements of the conversion circuit section (6) during no-load operation, and power loss such as iron loss and copper loss in the second reactor (7) and transformer (9).

[Brief explanation of the drawing]

The drawings show one embodiment of the inverter device of the present invention,
Figure 1 is a block wiring diagram, Figures 2 (a) to (C) are load current, output voltage of the conversion circuit section, and relationship diagram between load voltage and time, respectively, and Figure 8 is demand for power reference value. FIG. 3 is a relationship diagram between the power ratio and the output voltage of the conversion circuit section. (6)...conversion circuit section, 0Q...current transformer,
...Control unit. Agent: Patent Attorney Ryuta Fujita Figure 1

Claims (1)

[Claims] ■ A conversion circuit section that converts DC power into AC power and supplies it to the load, a commercial power supply section that supplies commercial power to the load, and a detection section that is installed in the load line and detects the power demand of the load. , a control unit that switches the conversion circuit unit to supply power to the load by the commercial power supply unit and reduces the output of the conversion circuit unit when the demand power detected by the detection unit fluctuates above a predetermined value; An inverter device comprising: