JPS59198876A - Power sources operated in parallel - Google Patents

Abstract

PURPOSE:To simplify the configuration of a power sources by interposing a transformer having single phase 3-wired coils and single phase 2-wired coils when an inverter which employs a solar battery as a power source and a single phase 3-wired commercial power source are operated in parallel with each other. CONSTITUTION:A single phase 3-wired commercial power source is connected to the primary side of a transformer 13 having a single phase 3-wired primary coils 13a and single phase 2-wired secondary coils 13b, an inverter 14 which employs a solar battery as a power source are connected to the secondary side, a solar battery system is connected to the primary side of a transformer 15 having single phase 2-wired primary coil 15a and single phase 3-wired secondary coils 15b, loads 16, 17 are connected to the secondary side to operate the solar battery and the commercial power source in parallel. Accordingly, even if the load is single phase 3-wired type, the output voltage of the inverter 14 is controlled to allow the phase of the current to coincide with the phase of the load current, thereby preventing the occurrence of a cross current and the decrease in the efficiency of the solar battery.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device using parallel operation in which an inverter system using a solar cell as a power source and a commercial power system are connected in parallel, and both systems are operated to supply power to a load, and the configuration can be simplified. At the same time, it is an object of the present invention to easily prevent the occurrence of cross currents and a decrease in the efficiency of solar cells.

In general, in-house power generation equipment is installed not as an emergency power source but to save energy, and most of the in-house power consumption is met by the electricity from the in-house power generation equipment. Conventionally, solar cells have been used as the in-house power generation equipment. The use of power generation equipment is being carried out.

At this time, in the above-mentioned solar cell power generation equipment, 1) the power generated by the solar cells varies greatly due to fluctuations in the amount of solar radiation during the day and night or in the seasons, so a ballast is installed to stably supply power to the load. In addition, in order to supply power to AC loads such as lighting, an inverter is required to convert the DC power of the solar cell into AC power.

When power is supplied to the load only by an inverter system that connects solar cells and inverters,
As mentioned above, it is necessary to install a storage battery such as a lead-acid battery in parallel with the solar cell to absorb fluctuations in the power generated by the solar cell, but this requires multiple storage batteries and the installation location is limited. As the size increases, problems arise, such as the need for maintenance.

If power is still supplied to the load only by the inverter system, if the total power demand of the load exceeds the power supplied by the inverter system, a power shortage will occur, especially in the winter, and the power generated by the solar cells will be lower than in the summer. Since the amount of power is significantly reduced compared to the current amount, the power shortage state will continue for a long time, and it will be necessary to back up the insufficient power by some means.

Therefore, power is supplied to the load using a so-called parallel-operated power supply device that connects and operates a commercial power system in parallel to the inverter system. By setting the ratio, it is possible to extract the maximum amount of power generated by the solar cell and operate the solar cell with high efficiency without using the buffer storage battery, and at the same time, the insufficient power can be transferred to the commercial power supply system. The load can be operated normally by compensating for this.

At this time, in the power supply device, care must be taken not to generate a so-called cross current in which power flows from both systems to the directly connected power supply system.

Now, Figure 1 shows the basic circuit of the power supply device using the parallel operation, and the inverter output voltage of the inverter system is
, the internal impedance is represented by Zl, the line voltage of the commercial power supply system is represented by Ec, and the power supply impedance is represented by Zc, and both systems are connected in parallel to a load of impedance Zz. Here, the voltage across the load is El
and the inverter current from the inverter system to the load is l
l, the commercial current from the commercial power supply system to the load is Ic, and the load current is 11! (=1i-1-Ic).

Since the inverter system is provided with a harmonic suppression filter (not shown), the impedance zi is not relatively large, and the impedance Zc of the commercial power system is small, so each of the impedances Between Zi, Zc, and Zg, there is Zc (Zi,
If the Zc (Zl) relationship holds true, the relationship El'::Ec must hold between the i pressures Ei and Ec, and the inverter current Ii is approximately as follows: Ii = (Ei −-Ec)/Zi When the voltages Ei, Ec, El and the currents IIc and If are expressed as a vector diagram, if the load is inductive, it becomes as shown in FIG.

Therefore, in order to perform appropriate power sharing between the two systems and prevent cross current, it is not enough to simply match the absolute value 9 phases of the inverter output voltage El and the absolute value 9 phases of the line voltage Ec. It is necessary to control the amplitude and phase of the output voltage Ei of the inverter system so that the phase of the inverter current 1 and the load current J4 coincides with Ii (IJ).

Therefore, a power supply device that operates in parallel as shown in FIG. 3 has conventionally been implemented.

In the figure, (1) is a solar cell, and (2) is an inverter system (3) whose input terminal is connected to the output terminal of the solar cell (1) and the solar cell (1) and a control unit (described later). Inverter, (4) is a commercial power supply system connected in parallel to inverter system (3), (5) is both systems + 31
, +41 is the load provided in parallel, (6) is the first current transformer provided on the output line (7) of the inverter system (3) and takes out the inverter current, (8) is the load line (9)
A second current transformer, QO, (1
11 are input terminals or both flow devices (6) and (81
1) Two current detectors that detect the inverter current and load current and output the detected bias.

(11) is a control unit consisting of a PLL circuit, etc. connected to the output terminal of the inverter (2).
((It is designed to output a control signal to control the output of the inverter (2), and as described above, the magnitude and phase of the output voltage of the inverter (2) are controlled by the control section (1), The phase of the inverter current matches the phase of the load current, the inverter current is controlled to be smaller than the load current, and cross current is prevented from occurring.

By the way, the above is a case where a so-called single-phase two-wire commercial power supply system and an inverter system are installed in parallel, and a single-phase three-wire commercial power system and an inverter system are installed in parallel.
To operate a single-phase 3-wire load by installing a wire-type commercial power supply system and an impark system in parallel, the power supply device shown in Figure 3 above is one of the best ways to operate a single-phase 3-wire load. It can be applied conventionally,
A power supply device as shown in FIGS. 4 to 6 has been implemented.

In each figure, (U), (0), and (V) are the lines of a single-phase three-wire commercial power system, (Zu) and (Zv) are the internal impedances of the commercial power system, and <ze), (
zt;>' is the load for single-phase 3-wire, (IV), (IV
)' is an inverter system powered by solar cells, (Zi)
, (Zi)'u i:/Vata lineage (IV).

(IV)' internal impedance.

In the case of Fig. 4, loads (Zl) and (ZJ)' are applied between the lines (U) and (0) and between the lines (0) and (V).
In the case of FIG. 5, the circuit of FIG. In the case of Fig. 6, the inverter system (■η) is connected in parallel to only one load (zl) of the circuit shown in Fig. 4.
′ in parallel with two inverters (IV), (
IV)' are connected.

However, in the case of FIG. 4, the phases of the currents Iu and iv flowing through the loads (zl) and (zz)' are different, so that the load current ■u.

It is possible to match the phase of Iv and the phase of the inverter current Ii.A cross current occurs, and in the case of Fig. 5, the phase of the current flowing through one load (cze) and the phase of the inverter current Although it is possible to prevent the occurrence of cross current by matching the power supply voltages, when the power of the power grid (IV) exceeds the power demand of one load (Zl), the surplus power is transferred to the commercial power grid. Since the power cannot be regenerated to the side, the power generated by the solar cells that are the power source of the inverter system (IV) must be reduced, which has the disadvantage of causing a decrease in the efficiency of the solar cells.

Furthermore, in the case of Fig. 6, while it is possible to prevent the occurrence of cross currents and a decrease in the efficiency of the solar cells that are the power source of Since two are required, the disadvantage is that it is expensive and has a complicated structure.

This invention has been made with the above-mentioned points in mind, and is intended to be applied to the solar power system and the single-phase three-way system, which uses solar cells as a power source.
In a power supply device for parallel operation in which a wire-type commercial power supply system is operated in parallel to supply power to a load, a transformer having a primary coil for single-phase 3-wire and a secondary coil for single-phase 2-wire is provided, The present invention provides a power supply device capable of parallel operation, characterized in that the commercial power supply system is connected to the secondary coil, and a parallel circuit consisting of the inverter system and the load is connected to the secondary coil.

Therefore, according to the parallel operation power supply device of the present invention, the configuration can be simplified by providing a transformer that connects the single-phase three-wire commercial power system and the single-phase two-wire inverter system in parallel. In addition, even if the commercial power supply system and the load are single-phase three-wire type, the output voltage of the inverter system can be controlled to easily match the phase of the inverter current and the phase of the load current, The configuration can be simplified, and the generation of cross currents and a decrease in the efficiency of the solar cells that are the power source of the inverter system can be easily prevented.

At this point, this invention will be explained in detail with reference to the drawings from FIG. 7 showing an embodiment thereof.

First, FIG. 7 showing one embodiment will be explained.

In the same figure, (1) is a single-phase three-wire primary coil (13
a) and a secondary coil (+3b) for single-phase two-wire use.It is a first transformer with a turns ratio of 1:n, and a primary coil (+3b).
3a) Both ends and center taps are each a line (U) 7 (V) of a single-phase three-wire commercial power system (not shown),
(0). (Zu) and (Zv) are the internal impedances of the commercial power supply system, (]4) is an inverter system whose power source is a solar cell (not shown) connected in parallel to the secondary coil (+3b), and (Zi) is the internal impedance of the inverter system 0, 00 is the second transformer with a turns ratio of nil connected to both ends of the secondary coil (13b) of single-phase two-wire It is a load for phase 3 wires, and is provided between one end of the secondary coil (+5b) of the second transformer and the intermediate tap, and between the intermediate tap and the other end of the secondary coil (15b). , the inverter system (14
) and are connected in parallel to the commercial power supply system.

At this time, the power sharing ratio between the two systems can be determined based on the power of both systems on the secondary coil (13b) side of the first transformer 0], and the power sharing ratio can be easily determined. It is possible to easily match the phase of the inverter current from the inverter system 04) and the phase of the current flowing through the load (zI and (zI), respectively), and it is also possible to easily adjust the inverter current to the load current. can be controlled to be smaller than

Therefore, according to the embodiment, the single-phase three-wire commercial power supply system and the load α! , a transformer Oa that connects Q71 and a single-phase two-wire inverter system 0 brown in parallel.

By providing θυ, the configuration can be simplified, and the commercial power supply system and load QQ can be simplified.

Even if qη is a single-phase three-wire system, the inverter system (one centimeter output voltage can be controlled to easily match the phase of the inverter current and the phase of the load current, simplifying the configuration. In addition, as shown in Figure 8, in the case of a single-phase two-wire type load, the first transformer (11-2
By connecting the single-phase two-wire load 08) and the parallel circuit of the inverter system (14) to both ends of the next coil (+3b), a simple device can easily generate a cross current and control the power supply of the inverter system 04). Preventing a decline in the efficiency of certain solar cells.

be able to.

[Brief explanation of drawings]

Figure 1 is a diagram showing the basic circuit of a power supply system with parallel operation of an inverter system and a commercial power supply system, Figure 2 is a voltage and current vector diagram for the power supply system in Figure 1, and Figure 3 is a diagram showing the power supply system in parallel operation of an inverter system and a commercial power supply system. A wiring diagram of a power supply device using conventional parallel operation in the case of a single-phase two-wire system, and Figures 4 to 6 are wiring diagrams of a power supply device using conventional parallel operation when the commercial power supply system is a single-phase three-wire system, respectively. , FIG. 7, and FIG. 8 are wiring diagrams of embodiments of the power supply device operating in parallel according to the present invention. α4...first transformer, (14), inverter system,
06j. 0η, 08)...Load.

Claims (1)

[Claims] ■ Inverter system and single-phase 3 power source powered by solar cells
In a power supply device for parallel operation in which a wire-type commercial power supply system is operated in parallel to supply power to a load, a transformer having a primary coil for single-phase 3-wire and a secondary coil for single-phase 2-wire is provided, A power supply device operating in parallel, characterized in that the commercial power supply system is connected to the secondary coil, and a parallel circuit consisting of the inverter system and the load is connected to the secondary coil.