JPH07302130A - Power controller - Google Patents

Abstract

PURPOSE:To effectively take the electric power out of plural battery units which are conneted in series and/or in parallel to each other. CONSTITUTION:A power controller takes the electric power out of plural battery units SB and is provided with the 1st power inverter means EFT, L and D which are placed against each unit SB, a control means CNT which detects the fluctuation of the output voltage-output current curve of each unit SB and controls the 1st power inverter means corresponding to each unit SB so as to acquire the maximum output from each unit SB, and a 2nd power inverter means INV1 which inverts the electric power obtained by synthesizing the output of the 1st power inverter means into the electric power of the prescribed value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for efficiently extracting electric power from a power source such as a solar cell.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of energy saving, a solar power generation device which converts solar energy into electric power by a solar cell has been attracting attention.

The wafer, which is the body of this solar cell, is 1
There is an electromotive force of about 0.5 V per element, and several tens of wafers are combined to form a solar cell panel. Then, in order to actually generate power, a power generation module is constructed by connecting several panels to several tens of them in series and parallel so as to meet the required amount of power generation,
Generating power.

As shown in FIG. 3, the output of this solar cell module varies greatly depending on the sunshine, the temperature, and the amount of deterioration of the solar cell at that time. Therefore, the power that can be extracted is limited under certain operating conditions. If you generate electricity in an actual natural environment despite the fact that there is a power conversion efficiency of about 10% under ideal sunlight, the operating point of the solar cell will deviate from the ideal position, so the ideal state There was a defect that it could not take out half the power of the above.

As a countermeasure, a solar cell for detecting the output of the battery panel, which closely resembles the characteristics of the solar cell element used in the panel, is arranged near the solar cell panel, and the operating point of the solar cell panel is simulated. How to estimate and determine the control value,
Utilizing the fact that the operating point of a solar cell is easily affected by temperature, a method was used in which a temperature detecting element was placed on the back side of the solar cell panel and the operating point of the solar cell was determined from the temperature on the back surface of the panel. .

[0006]

However, in the pilot output detection method in which the solar cell for detecting the battery panel output is arranged in the vicinity of the solar cell panel, the solar radiation for the output detecting solar cell and the solar cell for extracting electric power is used. However, there was a possibility that only the solar cells for electric power extraction would be shaded, and the maximum amount of electric power generated by the solar cells was not extracted.

Further, in the method of arranging the temperature detecting element on the back side of the solar cell panel and determining the operating point of the solar cell from the temperature on the back surface of the panel, the temperature characteristic of the solar cell can be corrected, but the entire panel is uniform. It is not always the temperature, and there is no particular correlation between the amount of solar radiation and the back surface temperature of the panel, so it was hard to say that the maximum value of the power generated by the solar cell at that time was taken out.

As a countermeasure, the fluctuation of the solar cell VI straight line in FIG. 3 is detected from the solar cell generated voltage Vin and the battery output current Iin as in the power controller shown in FIG. 4, and the maximum power is calculated from the fluctuation amount. A method has been devised in which the maximum power point is detected by the circuit MPP1 and the power control value is given to the DC-AC power conversion inverter INV1, so that the operating point of the solar cell is tracked to the maximum power point. However, even with this method, when a large number of panels are connected in series and parallel, the solar cell conversion efficiency and temperature characteristics are different, so that the characteristics of each panel must be averaged to operate at the maximum power point. Therefore, each solar cell panel operates at a point outside the maximum point of the light-power conversion efficiency, so that the power generated by each solar cell panel cannot be efficiently extracted.

Further, in the method of detecting the maximum power operating point from the VI curve, the solar cell generated voltage Vbatt is obtained when the maximum power point is tracked as shown in the diagram of the daily power generation amount of FIG.
Fluctuates drastically, and the input voltage of the inverter unit that converts DC voltage into AC power fluctuates significantly, so the control range of the DC-AC conversion inverter unit widens and the operation stability tends to decrease, and Since the input voltage fluctuates, the power conversion efficiency is reduced.

The present invention has been made in view of the problems in the above-mentioned conventional example, and efficiently takes out electric power from each solar cell panel, thereby improving the electric power conversion efficiency of the solar cell module and the entire solar power generation device. An object of the present invention is to provide an improved power control device.

[0011]

In order to solve the above-mentioned problems, in the present invention, a first power conversion means such as a DC-DC converter is provided for each battery unit such as each solar cell panel, and By using the control means for detecting the fluctuation of the VI curve, detecting the maximum power point from the fluctuation amount, and determining the operating point of the first power conversion means, the operating point of each battery unit is determined to be the most efficient. By setting it to a good point and combining the power combined with the output of the power converter for each unit and performing a second power conversion, for example, DC-AC conversion, it is possible to efficiently extract the battery-generated power. It is a thing.

[0012]

According to the present invention, by providing the first power conversion means for each battery unit, it becomes possible to most efficiently take out the power from each battery unit. Also,
When a solar cell panel is used as the battery unit, a DC-DC converter is used as the first power conversion means, and a DC-AC inverter device is used as the second power conversion means, the DC-AC inverter device has a constant input voltage. Since the maximum power can be taken out from the solar cell with simple control, the control circuit of the inverter device can be simplified, and the power switch element used in the inverter device can be optimized because the voltage fluctuation is small. It is possible to improve the power conversion efficiency and reduce the cost of the entire device. Normally, if you do not install solar panels with the same characteristics under the same conditions as much as possible, the power that can be generated will greatly decrease due to the differences in the characteristics of each solar cell. By using the configuration provided, it becomes possible to efficiently extract electric power even if the solar cell panels having different output powers are combined.

[0013]

EXAMPLES Examples of the present invention will be described below. FIG. 1 shows the configuration of a power control device according to an embodiment of the present invention. Figure 1
4, the same reference numerals as those in FIG. 4 indicate the same components.
In FIG. 1, the DC-DC power conversion module EM is
Solar cell panel SB, voltage conversion coil L, power switch element MOS-FET, power output diode D, solar cell voltage detection circuits R1 and R2, solar cell output current detection circuit CT, and control circuit CNT that controls the input / output. It consists of A plurality (4 sets in the figure) of the power conversion modules EM are connected in parallel and connected to the capacitor C1. The capacitor C1 is an electrolytic capacitor for absorbing power supply ripple. INV1 is a DC-AC power conversion circuit, which receives the DC voltage stored in the capacitor C1 as input, generates AC power, and outputs the power to an AC load.

Next, the operation will be described. When sunlight is incident on the solar cell panel SB of the power conversion module EM, an electromotive voltage is generated at both ends of the solar cell panel SB.
The generated power at that time is almost proportional to the amount of light incident on the panel as shown in FIG. When the generated power exceeds a certain level, the control circuit operates to measure the output voltage and output power of the solar cell, and to set the operating point of the solar cell to the maximum power point on the VI curve. -A PWM pulse is applied from the control circuit CNT to the gate of the FET, and M
A chopping current flows through the voltage conversion coil as the OS-FET is turned on and off. That is, MOS-FET
When is turned on, the power generated by the solar cell panel is stored in the coil. When the MOS-FET is turned off, the power stored in the coil and the power generated by the solar cell are added, and the power is transferred to the smoothing capacitor C1 through the voltage output diode. By repeating these operations, each power conversion module EM continues to transfer the maximum power that can be extracted from each solar cell panel SB to the smoothing capacitor C1.

Inverter INV1 for DC-AC power conversion
When the total power generated by the power conversion module exceeds a certain value, the power stored in C1 activates the inverter circuit to generate the AC power required on the load side. In this inverter INV1, when the electric power stored in the capacitor C1 becomes large, the operation of the inverter unit is stable because the control is simple enough to increase the output electric energy, and as a result of the power control of the inverter unit, the input voltage is Since the voltage is almost constant, the power conversion efficiency is improved.

FIG. 5 shows the construction of a photovoltaic power generator according to another embodiment of the present invention. In order to enhance the control of the device of FIG. 1, this device has an overall control device CNT1 and is connected to each module or device by an electromagnetic or optical signal transmitting / receiving means. With such a configuration, the control of the maximum power by the VI curve of the solar cell panel SB, which is individually controlled, can be processed by the overall control device CNT1, so that the accuracy of the maximum power control can be improved and Since the start and stop sequence of power conversion for each module can be controlled by the entire power conversion device, it is possible to effectively take out power even when the solar cell generated power is small.
In addition, by adopting such a configuration, it is possible to perform self-diagnosis function of each module and inverter device, check and report the operating status between each module, and disconnect each module when the function is abnormal. Also, there is an advantage that the maintenance of the device can be promptly performed because the user can be alerted when an abnormality occurs.

Further, by connecting a telephone line interface device as shown in FIG. 5, it is possible to realize the above-mentioned function even in a remote place to monitor the device and receive an alarm.

As described above, by providing a DC / DC converter for each solar cell panel, it becomes possible to most efficiently take out electric power from each solar cell panel, and the DC / AC inverter device has an input voltage. Since the maximum power can be taken out from the solar cell with a simple and constant control, the control circuit of the inverter device can be simplified, and the power switch elements used in the inverter device should also be optimized because there is little voltage fluctuation. It is possible to improve the power conversion efficiency and reduce the cost of the entire device. Normally, if the solar cell panels with the same characteristics are not installed under the same conditions as much as possible, the power that can be generated will greatly decrease due to the difference in the characteristics of each solar cell, but a DC-DC converter is required for each such panel. By using the configuration provided, it becomes possible to efficiently extract electric power even if the solar cell panels having different output powers are combined.

Although the solar cell panel is used as the battery unit in the above embodiment, the present invention is
It can also be applied to a power generator or power supply device that uses a primary battery such as a fuel cell or a secondary battery as a battery unit. Moreover, when supplying electric power to a DC load, a DC-DC converter, not a DC-AC inverter, is used as the second power converter.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a power control device according to an embodiment of the present invention.

FIG. 2 is a graph showing an example of daily generated power of a solar cell and an optimum operating voltage.

FIG. 3 is a graph showing an example of received light amount vs. VI characteristics of a solar cell.

FIG. 4 is a block diagram showing a configuration of a conventional power control device.

5 is a block diagram of a power control device in which an overall control device for highly controlling the device of FIG. 1 is added.

[Explanation of symbols]

SB: solar cell, CNT: control circuit, L: coil, D:
Diode, C1: Smoothing capacitor, INV1: DC-AC power converter, EM: Power converter module, CNT
1: Overall control device, MPP1: Maximum power calculation circuit.

Claims (8)

[Claims] 1. A power control device for extracting power from a plurality of battery units, the first power converting means being provided corresponding to each battery unit, and the fluctuation of the output voltage-output current curve of each battery unit. And a control means for controlling the first power conversion means corresponding to each battery unit so as to obtain the maximum output from each battery unit, and a predetermined combined electric power obtained by combining the outputs of the first power conversion means. A power control device comprising: a second power conversion means for converting into electric power. 2. The power control device according to claim 1, wherein the second power conversion means converts the combined output voltage of the first power conversion means into a constant voltage and outputs the constant voltage. 3. The power control device according to claim 1, wherein the second power conversion means is a DC-AC power conversion device. 4. The power control device according to claim 1, wherein the first power conversion means is a DC-DC voltage converter. 5. The power control device according to claim 1, wherein each of the first power conversion means is incorporated in a voltage conversion module including each battery unit. 6. The overall control device for detecting the states of the first power conversion means and the second power conversion means using a communication means and controlling the entire power conversion device is used. The power control device according to any one of to 4. 7. The power control device according to claim 6, wherein the overall control device that controls the entire power conversion device includes a communication unit with the outside. 8. The power control according to claim 1, wherein the battery unit is a solar cell panel in which a plurality of solar cell elements are connected in series and / or in parallel. apparatus.