JP2015163000A - Solar cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an energy loss in a solar cell system for supplying power to equipment which is driven with commercial power.SOLUTION: Switchover means (17a) is provided for switching between a charge state (S1), in which EDLC (16) is charged by a solar cell unit (12), and a discharge state (S2) in which the outputs of the solar cell unit (12) and the EDLC (16) are connected to a booster unit (14). Also, a current detection unit (18) is provided for detecting a current value (Id) on a current path which runs from the solar cell unit (12) to an inverter (213), so as to control the switchover means (17a) to switch to the charge state (S1) when the current value (Id) is smaller than a threshold (Th).

Description

  The present invention relates to a solar cell system that assists in powering a device driven by commercial power.

  In an air conditioner, a power conversion device including a converter and an inverter is often used. Such a power converter reconverts AC power (commercial power) supplied from a commercial power source into AC power, and drives a load such as a compressor motor with the reconverted AC power.

  In addition, for the purpose of energy saving and the like, a power generation apparatus (also referred to as a PV unit) that performs solar power generation (Photovoltaics: PV) using sunlight is being introduced into homes and offices. Since photovoltaic power generation has the characteristic that the output voltage fluctuation is small, if the power of photovoltaic power generation is DC fed to the DC link that is the connection point between the converter and inverter of the power converter, the power converter is power assisted. can do.

  On the other hand, solar power generation has a demerit that the generated power varies greatly depending on the amount of solar radiation. For this reason, solar power generation requires MPPT (Maximum Power Point Tracking) control for always taking out the maximum power with respect to changes in the amount of solar radiation, and power is supplied to the load via a DC / DC converter capable of MPPT control. It is common to do.

  In addition, an electric storage device such as an EDLC (Electric Double Layer Capacitor) may be used in combination to compensate for fluctuations in the generated power of solar power generation (see, for example, Patent Document 1).

JP 2002-272015 A

  However, when the power passing through the DC / DC converter is small (when the power generated by solar power generation is relatively small), the loss of the DC / DC converter tends to increase, and the generated energy can be used effectively. Not.

  The present invention has been made paying attention to the above-described problems, and aims to reduce the loss of generated power in a solar cell system that supplies power to equipment driven by commercial power.

In order to solve the above problems, the first invention is
A converter (211) that converts AC power supplied from a commercial power supply (30) into DC power, and an inverter (213) that converts the output of the converter (211) into AC power and supplies it to a load (M) In the solar cell system for supplying power to the power converter (210) provided,
A solar cell unit (12) for generating direct-current power in response to sunlight,
Electric double layer capacitor (16),
A step-up unit (14) for stepping up DC power of the solar cell unit (12) and the electric double layer capacitor (16) and supplying the boosted power to the inverter (213);
The charging state (S1) in which the electric double layer capacitor (16) is charged from the solar cell unit (12), and the outputs of the solar cell unit (12) and the electric double layer capacitor (16) are converted into the boost unit (14 Switching means (17a) for switching between the discharge state (S2) connected to
On the current path from the solar cell unit (12) to the inverter (213) via the switching means (17a) and the boosting unit (14), a current detector (Id) that detects a current value (Id) 18) and
And a control unit (19) for controlling the switching means (17a) to the charged state (S1) when the current value (Id) is smaller than a predetermined threshold value (Th).

  In this configuration, the current value on the current path from the solar cell unit (12) to the inverter (213) via the switching means (17a) and the booster unit (14) is used as an index to pass through the booster unit (14). The magnitude of power to be evaluated is evaluated. When the current value (Id) is smaller than the predetermined threshold value (Th), that is, when the power passing through the boosting unit (14) is smaller than the predetermined value, the electric double layer capacitor (16) is charged. The

In addition, the second invention,
In the first invention,
The controller (19) periodically checks the current value (Id) after switching the switching means (17a) to the charging state (S1), and the current value (Id) is the threshold value (Id). When it exceeds (Th), the switching means (17a) is switched to the discharge state (S2).

  In this configuration, when power passing through the boosting unit (14) can be increased, DC power feeding using the solar cell unit (12) is resumed.

In addition, the third invention,
In the second invention,
The current detector (18) is provided on a current path between the switching means (17a) and the boost unit (14),
After switching the switching means (17a) to the charged state (S1), the control section (19) is configured to switch the switching means in order to cause the current detection section (18) to detect the current value (Id). (17a) is periodically returned to the discharge state (S2).

In addition, the fourth invention is
In any one of the first to third inventions,
When the electric double layer capacitor (16) is in a fully charged state, the control unit (19) prioritizes switching based on the threshold value (Th) and switches the switching means (17a) to the discharging state (S2 ).

  In this configuration, when the electric double layer capacitor (16) need not be charged, the electric power of the electric double layer capacitor (16) is used.

  According to the first invention, in the solar cell system that supplies power to equipment driven by commercial power, it is possible to reduce the loss of generated energy.

  Further, according to the second and third inventions, when the power passing through the boosting unit (14) can be increased, the DC power supply using the solar cell unit (12) is resumed. It becomes possible to operate (14).

  Further, according to the fourth invention, the electric power of the electric double layer capacitor (16) is used without waste, and the efficiency of the entire system is improved.

FIG. 1 shows an air conditioning system including a solar cell system according to Embodiment 1 of the present invention. FIG. 2 shows a power system of the air conditioning system. FIG. 3 illustrates the conversion efficiency with respect to the load factor of the boosting unit. FIG. 4 illustrates the relationship between output power and solar radiation intensity in solar power generation. FIG. 5 shows an air conditioning system power system according to the second embodiment. FIG. 6 shows an electric power system of an air conditioning system according to the third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

Embodiment 1 of the Invention
FIG. 1 shows an air conditioning system (1) including a solar cell system (10) according to Embodiment 1 of the present invention. The air conditioning system (1) includes an air conditioner (20) in addition to the solar cell system (10).

<Air conditioner>
The air conditioner (20) is driven by AC power (commercial power) supplied from a commercial power source (30). The solar cell system (10) receives sunlight to generate electric power, and DC-feeds the generated power to the air conditioner (20) to assist the air conditioner (20) with electric power.

  The air conditioner (20) includes an indoor unit (21) installed indoors and an outdoor unit (22) set outdoor. The indoor unit (21) and the outdoor unit (22) are connected to each other by a connecting pipe (23, 23), thereby forming a refrigerant circuit.

  The indoor unit (21) includes an indoor heat exchanger (201), an indoor fan (202), and an indoor expansion valve (203). In the indoor heat exchanger (201), room air is blown by the indoor fan (202). Thereby, in the indoor heat exchanger (201), heat is exchanged between the refrigerant flowing inside the heat transfer tube and the room air. The indoor expansion valve (203) is constituted by, for example, an electronic expansion valve.

  The outdoor unit (22) includes an outdoor heat exchanger (204), an outdoor fan (205), an outdoor expansion valve (206), a compressor (207), a four-way switching valve (208), and a power converter (210). It is out. In the outdoor heat exchanger (204), outdoor air is blown by the outdoor fan (205). Thereby, in the outdoor heat exchanger (204), heat is exchanged between the refrigerant flowing inside the heat transfer tube and the outdoor air. The outdoor expansion valve (206) is constituted by, for example, an electronic expansion valve.

  The compressor (207) has a motor (M). For example, the compressor (207) is constituted by a rotary compressor such as a scroll compressor.

  The four-way switching valve (208) has four ports from first to fourth, and is configured to switch the circulation direction of the refrigerant in the refrigerant circuit. The four-way switching valve (208) is in a state where the first port and the second port communicate with each other during cooling operation and the third port and the fourth port communicate with each other (state indicated by a solid line in FIG. 1). And the third port communicate with each other and the second port and the fourth port communicate with each other (state indicated by a broken line in FIG. 1).

-Power converter (210)-
The power converter (210) drives the motor (M) by converting commercial power into desired output AC power and supplying it to the motor (M) of the compressor (207). In this example, the commercial power is single-phase AC power, and the output AC power is three-phase AC power. The commercial power may be three-phase AC power. The commercial air conditioner (20) may use 200V three-phase AC power as a power source.

  FIG. 2 shows a power system of the air conditioning system (1). As shown in FIG. 2, the power converter (210) includes a converter (211) and an inverter (213). The converter (211) converts AC power supplied from the commercial power source (30) into DC power (AC / DC conversion) and outputs the converted DC power. For example, the converter (211) can be realized by a diode bridge circuit.

  The inverter (213) converts the DC power output from the converter (211) into AC power (DC / AC conversion) by a switching operation and supplies the AC power to the load (motor (M) shown in FIG. 1). For example, the inverter (213) can be configured using a plurality of bridge-connected switching elements.

  Further, a smoothing capacitor (C) is provided in the DC link part (212) which is a connection node between the converter (211) and the inverter (213). The smoothing capacitor (C) smoothes the output of the converter (211) and generates a DC link voltage. For example, the smoothing capacitor (C) can be constituted by an electrolytic capacitor.

<Solar cell system>
As shown in FIG. 2, the solar cell system (10) includes a solar cell unit (12) (abbreviated as PV in the figure), a boost unit (14), an electric double layer capacitor (16) (hereinafter also referred to as EDLC). , A switch unit (17), a current detection unit (18), and a control unit (19).

  The solar cell unit (12) is provided on the roof of a house, the roof of a building, and the like, and receives direct sunlight to generate DC power. From the solar cell unit (12), so-called MPPT-controlled DC power is output.

  The step-up unit (14) is a so-called DC / DC converter, and boosts (DC / DC conversion) the supplied DC power and supplies it to the DC link unit (212) of the power converter (210). That is, the boosting unit (14) assists the power converter (210) with power by supplying DC power to the DC link unit (212).

  DC power is supplied to the booster unit (14) from the solar cell unit (12) and the EDLC (16). That is, the step-up unit (14) is also used as a DC / DC converter for discharging the EDLC (16). Since a general boost unit for photovoltaic power generation has a boost ratio of about 4 times at the maximum, the boost unit (14) has sufficient capacity to boost the discharge voltage of the EDLC (16). Yes.

−Switch part (17) −
The switch unit (17) includes a switch (17a) and a diode (17b). The switch (17a) has a charge state (S1) for charging the EDLC (16) from the solar cell unit (12), and a discharge for connecting the outputs of the solar cell unit (12) and the EDLC (16) to the boost unit (14). Switch to state (S2). In this example, the movable contact of the switch (17a) is connected to the output of the solar cell unit (12). The output of the EDLC (16) is connected to one fixed contact of the switch (17a), and the other fixed contact is connected to the input of the boosting unit (14). As the switch (17a), for example, a relay device for switching a DC electric circuit can be employed.

  When the movable contact of the switch (17a) is switched to the fixed contact on the EDLC (16) side, the solar cell unit (12) is connected to the EDLC (16), and the EDLC (16) is charged. That is, the switch (17a) is in the charged state (S1). When the movable contact of the switch (17a) is switched to the fixed contact on the boosting unit (14) side, the outputs of the solar cell unit (12) and the EDLC (16) are connected to the boosting unit (14). That is, the switch (17a) is in the discharge state (S2). Thus, the boosting unit (14) is supplied with DC power from the solar cell unit (12) and the EDLC (16). That is, the switch (17a) is an example of the switching means of the present invention.

  The diode (17b) has a cathode connected to the output of the solar cell unit (12) and an anode connected to the output of the EDLC (16). This diode (17b) prevents reverse current flow (flow from the solar cell unit (12) to the EDLC (16)) in the discharge state (S2).

-Current detector (18)-
On the current path from the solar cell unit (12) to the inverter (213) via the switch (17a) and the step-up unit (14), the current detector (18) is a direct current flowing through the current path. The value (Id) is detected. In this example, the current detection unit (18) is provided between the switch (17a) and the boosting unit (14). For example, a direct current transformer (DCCT) can be employed for the current detection unit (18). The detection value of the current detection unit (18) is input to the control unit (19).

-Control part (19)-
The control unit (19) switches the switch (17a). The control unit (19) is provided with a microcomputer and a memory storing a program for operating the microcomputer. In addition, the control unit (19) includes an amplifier circuit that amplifies the detection signal of the current detection unit (18), a comparator that compares the output of the amplifier circuit with a threshold value (described later), and a relay that configures a switch (17a). A driver circuit for driving is also provided.

<Control of switch (17a)>
The control unit (19) switches the switch (17a) according to the amount of power passing through the boosting unit (14). Specifically, when the DC power passing through the boosting unit (14) is smaller than a predetermined value, the EDLC (16) is charged. When the DC power exceeds the predetermined value, the solar cell unit (12) and the EDLC are charged. From (16), DC power is supplied to the inverter (213).

  Specifically, in this example, the boosting unit (14) is used as an index the current value on the current path from the solar cell unit (12) to the inverter (213) via the switch (17a) and the boosting unit (14). Evaluate the magnitude of power passing through. Therefore, the control unit (19) periodically monitors the detection value (current value (Id)) of the current detection unit (18) and compares it with a predetermined threshold value (Th). And a control part (19) controls a switch (17a) to a charge condition (S1), when the electric current value (Id) which the electric current detection part (18) detected is smaller than a threshold value (Th). That is, the EDLC (16) is charged with the electric power of the solar cell unit (12).

  In addition, the control unit (19) periodically checks the current value (Id) after switching the switch (17a) to the charged state (S1), and the current value (Id) exceeds the threshold value (Th). In this case, the switch (17a) is returned to the discharge state (S2), and DC power is supplied from the solar cell unit (12) and the EDLC (16) to the boost unit (14). That is, the power supply from the EDLC (16) to the boosting unit (14) is resumed.

  In this embodiment, when the switch (17a) is switched to the charged state (S1), no current flows through the current detection unit (18), and the control unit (19) cannot grasp the power passing through the boosting unit (14). . Therefore, the control unit (19) periodically switches the switch (17a) to the discharge state (S2), and causes the current detection unit (18) to detect the current. Thereby, a control part (19) can grasp | ascertain the electric power which passes an electric current value (Id), ie, a pressure | voltage rise unit (14).

<Effect in this embodiment>
FIG. 3 illustrates the conversion efficiency with respect to the load factor (%) of the boosting unit (14). Here, the load factor (%) is the output of the boost unit (14) ÷ the boost unit (14) rated capacity × 100. FIG. 4 illustrates the relationship between the output power (DC power) in solar power generation and the solar radiation intensity. In general, the output of photovoltaic power generation is proportional to the amount of solar radiation. Therefore, in the morning and evening when solar radiation is oblique to the solar cell panel, the power generation output of the solar cell decreases. That is, in solar power generation, a difference occurs in power generation output depending on the time zone. Moreover, since the solar radiation to the solar panel is oblique in winter compared to summer, the power generation output in winter is lower than in summer. That is, in solar power generation, a difference occurs in power generation output even between seasons. FIG. 3 illustrates the conversion efficiency in summer.

  In the following, the loss of the boosting unit (14) in the present embodiment is estimated. In addition, as a premise of trial calculation, the specification of a solar cell unit (12) shall be rated output 1KW and the maximum voltage 200V. Further, it is assumed that the conversion efficiency characteristic of the boosting unit (14) is shown in FIG. Moreover, the specification of EDLC (16) assumes that the rated capacity is 29.5F and the charge / discharge voltage range is 200V to 100V. And in this trial calculation, it aims at ensuring the conversion efficiency of a pressure | voltage rise unit (14) to 90% or more.

  As can be seen from FIG. 3, when the load factor is 20% or less, the conversion efficiency falls below 90%. Therefore, when the load factor is 20% or less, that is, when the output of the solar cell unit (12) is 0.2 KW or less which is 20% of the rated output 1 KW, the control is performed so that the EDLC (16) is charged. The threshold (Th) used in the part (19) is set.

  Under the sunshine conditions illustrated in FIG. 4, the solar cell unit (12) has an output of 0.2 kW or less for one hour in the morning and one hour in the evening. For example, the EDLC (16) is charged in one hour in the morning. The amount of energy applied is 1h × 200W / 2 = 100Wh. The same amount of energy can be charged even in the evening.

  On the other hand, since the specification of the EDLC (16) is the rated capacity of 29.5F and the charge / discharge voltage range is 200V to 100V, the amount of energy that can be charged / discharged to the EDLC (16) is (1/2 × 29.5 × 200). × 200−1 / 2 × 29.5 × 100 × 100) / 3600 = 123 Wh. That is, it can be seen that 100 Wh of energy generated by the solar cell unit (12) in the morning hour can be charged and discharged in the EDLC (16). The energy charged to the EDLC (16) (200Wh when morning and evening are combined) is discharged so that the load factor becomes 20% or more, so that the conversion efficiency of the boosting unit (14) is 90% or more. Can be used. Therefore, the loss in this case is approximately 200 Wh × 10% = 20 Wh.

  On the other hand, a system that does not control the switch (17a) based on the passing power of the boosting unit (14) as in this embodiment (referred to as a conventional system for convenience of explanation) is 100 Wh in the morning and 1 hour in the evening. The 100 Wh is subjected to DC / DC conversion in the boost unit (14), and it is estimated that the conversion efficiency in this case is about 80% (see FIG. 3). Then, in the conventional system, 200 Wh × 20% = 40 Wh is lost as a loss. Therefore, in this embodiment, the loss is halved compared to the conventional system. That is, it is possible to reduce the loss of generated energy in a solar cell system that supplies power to equipment driven by commercial power.

<< Embodiment 2 of the Invention >>
FIG. 5 shows a power system of the air conditioning system (1) according to the second embodiment. In this example, the current detection unit (18) is connected to the output of the solar cell unit (12) on the solar cell unit (12) side than the connection node between the diode (17b) and the switch (17a). . In the present embodiment, even when the switch (17a) is switched to the charged state (S1), the current detection unit (18) can detect the current. Therefore, it is not necessary to switch the switch (17a) when the control unit (19) periodically monitors the current value (Id).

<< Embodiment 3 of the Invention >>
FIG. 6 shows a power system of the air conditioning system (1) according to the third embodiment. In this example, the current detection unit (18) is connected to the output of the boosting unit (14). In the present embodiment, in the state where the switch (17a) is switched to the charging state (S1), the current detection unit (18) cannot detect the current, and therefore, similarly to the example of the first embodiment, the control unit (19) By periodically switching the switch (17a) to the discharge state (S2) and causing the current detection unit (18) to detect current, the power passing through the boosting unit (14) may be grasped.

<< Other Embodiments >>
When the EDLC (16) is in a fully charged state, the switch (17a) may be switched to the discharging state (S2) in preference to the switching based on the threshold value (Th). That is, when the EDLC (16) is fully charged, the switch (17a) is forcibly switched to the discharged state (S2) according to the size of the load so that energy can be used more efficiently. Is possible. In addition, if the voltage of EDLC (16) is detected, it can be detected whether EDLC (16) is a full charge state.

  The solar cell system (10) can also be applied to systems other than the air conditioning system. For example, the present invention can be applied to a refrigerator, a washing machine, an IH cooker, and the like.

  INDUSTRIAL APPLICABILITY The present invention is useful as a solar cell system that assists electric power for equipment driven by commercial power.

10 Solar Cell System 12 Solar Cell Unit 14 Booster Unit 16 EDLC (Electric Double Layer Capacitor)
17a switch (switching means)
18 Current detection unit 19 Control unit 30 Commercial power supply 210 Power converter 211 Converter 213 Inverter

Claims (4)

A converter (211) that converts AC power supplied from a commercial power supply (30) into DC power, and an inverter (213) that converts the output of the converter (211) into AC power and supplies it to a load (M) In the solar cell system for supplying power to the power converter (210) provided,
A solar cell unit (12) for generating direct-current power in response to sunlight,
Electric double layer capacitor (16),
A step-up unit (14) for stepping up DC power of the solar cell unit (12) and the electric double layer capacitor (16) and supplying the boosted power to the inverter (213);
The charging state (S1) in which the electric double layer capacitor (16) is charged from the solar cell unit (12), and the outputs of the solar cell unit (12) and the electric double layer capacitor (16) are converted into the boost unit (14 Switching means (17a) for switching between the discharge state (S2) connected to
On the current path from the solar cell unit (12) to the inverter (213) via the switching means (17a) and the boosting unit (14), a current detector (Id) that detects a current value (Id) 18) and
And a control unit (19) for controlling the switching means (17a) to the charged state (S1) when the current value (Id) is smaller than a predetermined threshold value (Th). system. In claim 1,
The controller (19) periodically checks the current value (Id) after switching the switching means (17a) to the charging state (S1), and the current value (Id) is the threshold value (Id). The solar cell system characterized by switching the switching means (17a) to the discharge state (S2) when exceeding Th). In claim 2,
The current detector (18) is provided on a current path between the switching means (17a) and the boost unit (14),
After switching the switching means (17a) to the charged state (S1), the control section (19) is configured to switch the switching means in order to cause the current detection section (18) to detect the current value (Id). (17a) is periodically returned to the discharge state (S2). In any one of Claims 1-3,
When the electric double layer capacitor (16) is in a fully charged state, the control unit (19) prioritizes switching based on the threshold value (Th) and switches the switching means (17a) to the discharging state (S2 The solar cell system characterized by switching to).

Images