JP2016181977A - Power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit which does not stop either one of a dispersed power source whose output rapidly drops and a dispersed power source whose transient response is slow even when both the dispersed power sources are connected in parallel to each other.SOLUTION: The power supply unit includes: a first dispersed power source with a first converter 4 which is connected with a solar battery 1, performs constant voltage control, and droops an output voltage when an input voltage is not more than a predetermined value, an input current is not less than a predetermined value or an output current is not less than a predetermined value; a second dispersed power source with a second converter 5 which is connected with a battery 2 other than a solar battery, connected in parallel to the first dispersed power source, performs constant voltage control, and droops an output voltage when an input voltage is not more than a predetermined value, an input current is not less than a predetermined value or an output current is not less than a predetermined value. The first converter controls an output voltage according to a voltage command, detects a decrease variation of an input voltage, and when the decrease variation of the input voltage exceeds the predetermined value, decreases a voltage command by the predetermined voltage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply apparatus including a plurality of distributed power supplies.

  Distributed power systems combining solar power generation, storage batteries, fuel cells, etc. are becoming widespread. However, this distributed power supply system has a problem that the number of power conversions is large and high system efficiency cannot be obtained.

  The storage battery is used in an emergency where there is no other power source, and since there is a concept that natural energy such as sunlight is actively used, it is necessary to give priority to the power used from each power source.

  There are methods described in Patent Document 1 and Patent Document 2 for connecting power sources in parallel. The power supply device of Patent Document 1 connects a distributed power supply and a centralized power supply in parallel, and limits the current supplied from the distributed power supply. Using a distributed power supply with voltage drooping characteristics that matches the terminal voltage of the centralized power supply when the load current is a predetermined value, and maintains a voltage slightly higher than the terminal voltage of the centralized power supply when the load current is less than the predetermined value Yes.

  The power supply device of Patent Document 2 includes a first power supply device that outputs a constant voltage regardless of the magnitude of the output current, and a second DC power supply device that outputs a DC voltage that monotonously decreases with the magnitude of the output current. The second power supply devices connected in parallel switch between the variable voltage mode and the constant voltage mode according to whether the power supply possible amount is equal to or less than a predetermined threshold.

Japanese Unexamined Patent Publication No. 01-081621 JP 2009-232675 A

  In addition, the distributed power source includes a distributed power source whose output sharply decreases and a distributed power source having a slow transient response.

  However, when these distributed power supplies are connected in parallel, the distributed power supply whose output rapidly decreases may stop.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply apparatus that does not stop any distributed power supply even if a distributed power supply whose output rapidly decreases and a distributed power supply with a slow transient response are connected in parallel.

  A power supply apparatus according to the present invention includes a first converter that is connected to a solar cell, controls a constant voltage, and drops an output voltage when an input voltage is a predetermined value or less, an input current is a predetermined value or more, or an output current is a predetermined value or more. Connected to the first distributed power source and a battery other than the solar cell and connected in parallel to the first distributed power source, and controlled at a constant voltage, the input voltage is below a predetermined value, the input current is above a predetermined value, or the output current is a predetermined value A second distributed power source including a second converter that droops the output voltage when the above is reached, the first converter controls the output voltage in accordance with a voltage command, detects a decrease change in the input voltage, When the amount of change in decrease exceeds a predetermined value, the voltage command is decreased by a predetermined voltage.

  According to the present invention, the first converter controls the output voltage in accordance with the voltage command, detects the decrease change amount of the input voltage, and outputs the voltage command when the decrease change amount of the input voltage exceeds a predetermined value. Provides a power supply that does not stop any distributed power supply even if a distributed power supply using a battery whose output drops sharply and a distributed power supply using a battery with a slow transient response are connected in parallel because the output is reduced by a predetermined voltage. can do.

1 is a configuration block diagram of a power supply device according to a first embodiment of the present invention. It is a figure which shows the characteristic of the output voltage and output current of each converter in the power supply device which concerns on Example 1 of this invention. It is a timing chart which shows the waveform of the inverter input voltage of this invention, the output voltage of a 1st converter, and the input current of a 2nd converter. It is a figure which shows the detailed circuit structure of the 1st converter of this invention. It is a figure which shows the detailed characteristic of the output voltage and electric current of the 1st converter of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration block diagram of a power supply device according to Embodiment 1 of the present invention. The power supply device shown in FIG. 1 is an integrated composite power conditioner in which respective converters are connected by a high-voltage DC bus, and includes two power sources, a solar cell (PV) 1 and a fuel cell (FC) 2, and 2 1 and the 2nd converters 4-5 provided corresponding to one electric power source, and the inverter 7 connected to the output of the 1st and 2nd converters 4-5 are provided.

  The solar cell 1 and the first converter 4 constitute a first distributed power source, and the fuel cell 2 and the second converter 5 constitute a second distributed power source. The solar cell 1 is connected to the first converter 4 and outputs DC power obtained by sunlight to the first converter 4. The fuel cell 2 is connected to the second converter 5, and outputs DC power obtained from the fuel to the second converter 5.

  Each of the first and second converters 4 to 5 performs constant voltage control during the independent operation, and reduces the output voltage when the input voltage is equal to or lower than the predetermined voltage or when the input current is equal to or higher than the predetermined current. Each of the first and second converters 4 to 5 converts the input DC power into predetermined DC power.

  Among the two distributed power sources, the high-priority distributed power source converter has a higher output voltage and lower output voltage than the low-priority distributed power source converter according to the priority of the two distributed power sources. The current is set low.

  Each of the first and second converters 4 to 5 is connected in parallel and connected to the input terminal of the inverter 7. The inverter 7 converts the DC power from the first converter 4 and the second converter 5 into AC power and supplies a self-sustained output to a load (not shown).

  FIG. 2 is a diagram illustrating the characteristics of the output voltage and output current of each converter according to the first embodiment. In this example, the first converter 4 has the highest priority, the output voltage is 390V and the output current is I1, the second converter 5 has the next highest priority, the output voltage is 380V, and the output current is I2 (I1 < I2).

  Next, the operation of each of the converters 4 to 5 will be described with reference to FIG. First, in the self-sustaining operation mode of the power supply apparatus when the system is out of power, that is, when the output current of the converters 4 to 5 is equal to or less than a predetermined output current, the converters 4 to 5 are operating with constant voltage control. .

  Here, the output voltage command value of the converter is set higher in descending order of priority (priority) of the power source to be used. In the example shown in FIG. 2, the output voltage command value of the first converter 4 is set to 390V, and the output voltage command value of the second converter 5 is set to 380V.

  In this case, since the output voltage command value of the first converter 4 is the highest, the first converter 4 preferentially uses the power of the solar cell 1.

  Next, when the self-sustained output load becomes large or the generated power of the solar cell 1 decreases and the self-sustained output voltage cannot be maintained with only the generated power of the solar cell 1, that is, the input voltage is lower than the predetermined voltage or the input When the current is greater than or equal to the predetermined current, the first converter 4 droops the output voltage.

  When the output voltage of the first converter 4 reaches the output voltage command value of the second converter 5 and the current becomes I1, the first converter 4 and the second converter 5 operate, and the DC power from the solar cell 1 is operated. The DC power from the fuel cell 2 is supplied to the inverter 7 and supplied to the load.

  For this reason, priority can be given to each power source 1-2 by the increase in load, and electric power can be supplied to the inverter 7 from each power source 1-2.

  Thus, normally, when the output voltage of the first converter 4 decreases to the output voltage of the second converter 5, power is added from the second converter 5, and the voltage does not further decrease.

  However, the output voltage of first converter 4 actually decreases rapidly at times t1 to t2, as shown in FIG. Since the fuel cell 2 has a slow response to a sudden change in load, the output decreases due to the sudden change in load. However, as shown in FIG. 3, the input current of the second converter 5 rises from about time t2. For this reason, since the output voltage of the 1st converter 4 will fall to a stop voltage, the 1st converter 4 may stop.

  In order to solve this problem, the first converter 4 according to the first embodiment includes the power conversion unit 11, the current detection unit 12, the voltage detection unit 13, the control circuit 14, and the dv / dt detection unit 15 illustrated in FIG. .

  The power conversion unit 11 converts DC power from the solar cell 1 into predetermined DC power based on the PWM signal from the control circuit 14. The current detection unit 12 detects an output current based on the predetermined DC power converted by the power conversion unit 11 and outputs a current command to the control circuit 14.

  The voltage detector 13 detects an output voltage based on the predetermined DC power converted by the power converter 11 and outputs a voltage command to the control circuit 14. The dv / dt detector 15 detects the solar cell output voltage at a predetermined interval in order to detect a change in the voltage of the solar cell 1, and the previous solar cell output voltage value held in the memory and the current solar cell A difference value from the battery output voltage value is output, and the current solar battery output voltage value is held in the memory.

  When the difference value output from the dv / dt detection unit 15 is equal to or less than a predetermined value, the control circuit 14 generates a PWM signal based on the voltage command and the current command and outputs the PWM signal to the power conversion unit 11.

  The control circuit 14 subtracts the voltage command by a predetermined decrease voltage Vd when the difference value ΔV (a decrease change amount of the input voltage) output from the dv / dt detector 15 exceeds a predetermined value. Thereby, the output voltage of the 1st converter 4 falls. In the first converter 4, the input current decreases as the output voltage decreases. Then, since the voltage of the solar cell 1 rises, the output voltage of the first converter 4 maintains this voltage.

  However, at this time, if the difference value ΔV output from the dv / dt detector 15 exceeds a predetermined value, the voltage command is further subtracted by a predetermined reduced voltage Vd. This subtraction process is performed until the difference value ΔV does not exceed a predetermined value.

  Even if the output voltage of the first converter 4 decreases, the first converter 4 does not stop if the output voltage is equal to or higher than the stop voltage of the first converter 4.

  The above processing will be described with reference to the characteristics of the output voltage and current of the first converter 4 shown in FIG.

  First, the output voltage of the first converter 4 operating at the point A is lowered by the drooping function and moves to the point B. Since the difference value between the voltage Va at the point A and the voltage Vb at the point B exceeds a predetermined value, the control circuit 14 subtracts the voltage command by a predetermined reduced voltage Vd. Then, the operating state of the first converter 4 moves to the point C.

  For this reason, the output voltage of the first converter 4 decreases, and the input current decreases. At this time, since the output power of the solar cell 1 decreases, the output voltage increases. Since the input voltage from the solar cell 1 increases, the first converter 4 maintains the operation state at the point C.

  Since it operates as described above, the first converter 4 is not stopped. Thereafter, since the second converter 5 starts up, the voltage input to the inverter 7 does not drop greatly, and the output of the inverter 7 is not affected.

1 Solar cell (PV)
2 Fuel cell (FC)
4 First converter 5 Second converter 7 Inverter 11 Power converter 12 Current detector 13 Voltage detector 14 Control circuit 15 dv / dt detector

Claims (3)

A first distributed power source including a first converter connected to the solar cell and controlled to perform a constant voltage and causes the output voltage to drop when the input voltage is equal to or lower than a predetermined value, the input current is equal to or higher than a predetermined value, or the output current is equal to or higher than a predetermined value;
Connected to a battery other than the solar battery and connected in parallel to the first distributed power source, and controlled at a constant voltage, the output voltage is adjusted when the input voltage is below a predetermined value, the input current is above a predetermined value, or the output current is above a predetermined value. A second distributed power source including a second converter to be suspended,
The first converter controls an output voltage in accordance with a voltage command, detects a decrease change amount of the input voltage, and if the decrease change amount of the input voltage exceeds a predetermined value, the voltage command is set to a predetermined voltage only. A power supply device characterized by being lowered. An inverter that converts DC power output from a converter included in the first distributed power source and the second distributed power source into AC power and supplies the load to a load;
Of the first distributed power supply and the second distributed power supply, the high-priority distributed power converter has a higher output voltage than the low-priority distributed power converter according to the priority of the distributed power. The power supply device according to claim 1, wherein:   The power supply apparatus according to claim 1, wherein the second distributed power supply is a fuel cell.

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