JP2580118Y2 - Electric water heater - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric water heater that is used in ordinary households, for example, using midnight power, and more particularly to an electric water heater that is effective in suppressing harmonic components contained in a power distribution system.

[0002]

[Background of the Invention] In recent years, the influence of harmonic components contained in a power distribution system in an urban power system has become a problem, and in particular, the problem of the fifth harmonic has become apparent. This is because the fifth harmonic is the largest among the harmonic components generated from the load system, and the characteristic of the power system is critical for the fifth harmonic as described later.

FIG. 3 is a circuit diagram schematically showing a power distribution system. In FIG. 3, reference numeral 1 denotes a higher harmonic voltage source generated by a large number of load systems, that is, a higher harmonic voltage source generated by harmonic currents flowing out from all the systems, 2 denotes a transformer for sending out a substation, and 3 denotes a customer. The phase-advancing capacitor 5 with a series reactor provided in the 6.6 kV power receiving unit on the side is a phase-advancing capacitor without a series reactor. 4 and 6 are general loads. The phase-advancing capacitor 3 with a series reactor is provided with a switch for power factor adjustment, and the series reactor suppresses an inrush current flowing at the time of switching control. Further, the series reactor acts so as to make the combined reactance inductive to the harmonic source so as not to expand the harmonic component. When a phase-advancing capacitor is always connected without performing such opening / closing control, a series reactor is not usually provided. However, in such a system, if the inductive reactance component of the transformer 2 in the substation and the capacitive reactance component of the cable system and the phase-advancing capacitor without the series reactor on the customer side are close to the series resonance, 6 The 0.6 kV bus has an increased distortion factor, and as a result, an overcurrent of the fifth harmonic flows through the phase-advancing capacitor with a series reactor connected to the system, which may burn it.

[0004] Here, the harmonic expansion rate (en / en /
En) is shown in FIG. As described above, the harmonic expansion rate is relatively small in the daytime and large in the nighttime. This is because the general load applied during the day works as a damping factor for the Q of the series resonance (steepness of resonance). Thus, the above problems are more acute at night than during the day.

[0005] Therefore, as countermeasures against such harmonic interference, guidelines for suppressing harmonic currents from general-purpose home appliances, suppressing harmonic currents from special consumers, and improving the harmonic withstand capability of equipment are presented. However, the current fear of harmonic interference cannot be immediately improved. A low-impedance circuit for a predetermined harmonic component by the LC circuit to absorb the harmonic component;
Alternatively, active filter type harmonic filter equipment that positively injects a harmonic current and absorbs a predetermined harmonic component is also used, but these are all various types of methods corresponding to an unspecified harmonic source. There is a problem, and it is usually used for local harmonic suppression measures corresponding to a specific load.

SUMMARY OF THE INVENTION The object of the present invention has been made in view of the above-mentioned background, and by improving electric water heaters used in ordinary households, it is possible to effectively eliminate harmonic interference by a so-called distributed filtering system. Is what you do.

[0007]

According to the electric water heater of the present invention, a plurality of electric heaters for heating water in a tank are provided as loads of a commercial power supply, respectively. Wherein a capacitor in series resonance with the pole transformer is connected in series to at least one of the plurality of electric heaters.

[0008]

In the electric water heater of the present invention, a plurality of electric heaters for heating water in the tank are provided, and at least one of the plurality of electric heaters is provided with a harmonic of a predetermined order of the commercial power supply frequency. A capacitor that resonates with the pole transformer in the distribution system is connected in series. With this configuration, the pole transformer of the distribution system and the capacitor resonate in series at a frequency of a predetermined order harmonic, and form a low impedance circuit with respect to the predetermined order harmonic. As a result, a predetermined-order harmonic component is consumed by the electric heater connected in series to the capacitor.
As a result, the harmonic component of a predetermined order on the primary side (for example, the 6.6 kV bus) of the pole transformer to which the harmonic component is shifted is absorbed. When the electric water heater of the present invention is used in many ordinary households, a predetermined order of harmonics will be absorbed at many points distributed in the load system. As described above, the harmonic components are dispersed and absorbed in the load system that is the harmonic generation source, thereby suppressing the harmonic components in the higher-order system to which the harmonic components are transferred. Harmonics of a predetermined order in the entire system are effectively suppressed. In particular, if this electric water heater is used as a late-night power water heater, harmonic components of a predetermined order that have been conventionally expanded at night can be suppressed, and harmonic interference can be effectively prevented.

[0009]

FIG. 2 shows the construction of an electric water heater according to an embodiment of the present invention. In FIG. 2, reference numeral 10 denotes a hot water storage tank;
2 is an electric heater for heating water (hot water) in the hot water storage tank 10, respectively. 13 is connected in series with the electric heater 11,
This is a capacitor that resonates in series with the pole transformer of the distribution system at the frequency of the fifth harmonic.

FIG. 1 is a diagram showing a configuration of an electric power system to which the electric water heater shown in FIG. 2 is connected.

In FIG. 1, reference numeral 16 denotes 77 kV in this example.
Main transformer at substation which transforms to 6.6 kV, 15
Is a pole transformer connected to the distribution line branched from the 6.6 kV bus and supplying 200 V to ordinary households. The electric water heater shown in FIG. 2 is connected to the consumer (general household) via a watt-hour meter 14. In this configuration, the capacitor 13 provided in the electric water heater resonates in series with the reactance component (substantially% impedance) of the pole transformer 15 at the fifth harmonic. Accordingly, for the fifth harmonic component, the impedance of the pole transformer 15 is almost zero.
As a result, the fifth harmonic component is consumed by the electric heater 11. As a result, the fifth harmonic energy of the distribution line branched from the 6.6 kV bus is absorbed by the load via the pole transformer 15, and the fifth harmonic of the 6.6 kV bus and the 77 kV system that is a higher system thereof. Ingredients are suppressed. Other harmonic components other than the fundamental wave component and the fifth harmonic are consumed by the electric heater 12. For example, when the 5th harmonic of 5% is included on the secondary side of the pole transformer 15, the 5th harmonic component is 1 when converted to the secondary side of the pole transformer 15.
Since it is 0 V, if the resistance value of the electric heater 11 is 1Ω, 10 A flows through the electric heater 11, and the fifth harmonic is consumed by the electric heater 11 at 100 W. As described above, the capacitance of the capacitor 13 is selected so as to resonate in series with the pole transformer at the fifth harmonic, and the resistance value of the electric heater 11 is determined by the distortion factor (the distortion behind the fifth harmonic component) included in the system. Rate) and the capacity of the pole transformer 15 are determined.

In the embodiment, an example is shown in which only the electric heater 11 for consuming the fifth harmonic component and the other ordinary electric heater 12 are arranged in parallel. However, the electric power consumed by the electric heater 11 is as follows. Since it is greatly affected by the distortion factor behind, according to the actual power consumption of the electric heater 11 that consumes the power of the fifth harmonic component in consideration of the required heat generation amount or the upper limit of the power consumption. Alternatively, the power consumption by another normal electric heater 12 may be adjusted. For example, a plurality of ordinary electric heaters without a capacitor may be provided, and the connection state may be switched to control the total power consumption to a required amount.

[0013]

According to the present invention, the following effects can be obtained.

(1) Not only can a predetermined harmonic component be suppressed, but also the energy of the harmonic component can be recovered as heat energy, so that electric power can be effectively used.

(2) Since the electric water heater according to the present invention is used in many ordinary households, many harmonic filters are distributed in the power system, and a distributed filtering system for harmonic components is provided. Can be realized.

(3) By dispersing and absorbing a harmonic component causing a harmonic disturbance in the vicinity of the source, the harmonic component of the load system is suppressed, and the higher-order system to which the harmonic component is transferred is provided. , And the distortion rate behind is reduced, so that a harmonic of a predetermined order in the entire power system can be effectively suppressed by a synergistic effect.

(4) By using the electric water heater of the present invention as a midnight power water heater, the electric water heater functions as a damping circuit for suppressing series resonance between a phase-advancing capacitor without a series reactor and a transformer, The expansion rate of the harmonic component at night is suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a power system including an electric water heater according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an electric water heater according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration example of a distribution system.

FIG. 4 is a diagram showing the relationship between the enlargement ratio of a harmonic component at night and during the day.

[Explanation of symbols]

 1-Harmonic voltage source 2-Transformer 3-Phase capacitor with series reactor 4,6-General load 5-Phase capacitor without series reactor 10-Tank 11,12-Electric heater 13-Capacitor 14-Watt hour meter

Claims (1)

(57) [Scope of request for utility model registration] A plurality of electric heaters for heating water in a tank are respectively provided as loads of a commercial power supply, and a capacitor that series-resonates with a pole transformer of a power distribution system at a harmonic of a predetermined order of the commercial power supply frequency is provided. An electric water heater connected in series to at least one of the plurality of electric heaters.