JP2014027761A - Power conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to effectively use generated power in an area where system voltage is chronically high while keeping the quality of system power without performing restriction of effective power in a range consumed by a building electric load if the system voltage is high.SOLUTION: A power conditioner 2 outputs generated power to a building electric load in cooperation with a commercial power system and controls output power such that the output power can be reversely flowed to the commercial power system. The power conditioner 2 comprises reverse current flow determination means for determining whether the output power is reversely flowing to the commercial power system or not and is configured not to reduce the effective power of the output power if an output power restriction control start condition is met but there is no reverse current flow, and to reduce the effective power of the output power only when there is reverse current flow.

Description

  The present invention relates to a power conditioner that supplies AC power to a premises electrical load linked to a commercial power system and allows reverse power flow to the commercial power system.

  The power conditioner for this type of conventional solar battery power generation system normally allows reverse power flow to the system while the system voltage exceeds a predetermined value, as disclosed in Patent Documents 1 and 2 below. When the power is on, voltage rise suppression control is performed to suppress the rise in system power voltage. That is, the Electricity Business Law stipulates that the system voltage of the commercial power system when the standard voltage is 100 V should be maintained in the range of 95 to 107 V with a 30-minute moving average value. In order to satisfy such requirements, in general power conditioners, in order to maintain the quality of the system power, when the system voltage rises to near 107V, first the phase advance reactive power control is performed. If it exceeds, output suppression control is performed.

JP 2009-17758 A JP 2006-29635 A

  However, in areas where there are substations or large factories in the vicinity, the system voltage may be chronically high at around 107V, and when a large electrical load at nearby factories stops. May temporarily increase the system voltage to about 110V.

  In the conventional power generation system installed in such an area, output suppression control is frequently performed, and the generated power of the solar cell panel cannot be effectively used.

  Therefore, even if the system voltage is high, the present invention does not suppress the active power within the range consumed by the on-site electrical load, thereby ensuring the quality of the system power while maintaining the quality of the system power. It is intended to enable effective use of generated power in an area where the system voltage is high.

  In order to achieve the above object, the present invention takes the following technical means.

  That is, according to the present invention, the generated power is grid-connected to the commercial power system and the generated power is output to the on-site electrical load. When the system voltage does not satisfy the predetermined output suppression control start condition, the output power is reversed to the commercial power system. In the power conditioner that controls the output power so as to enable power flow, the power conditioner includes reverse power flow determination means for determining whether or not the output power is flowing backward into the commercial power system, and satisfies the output suppression control start condition Even if it is a case, the active power of the output power is reduced only when the reverse power is flowing without reducing the active power of the output power if the reverse power is not flowing. (Claim 1).

  According to the power conditioner of the present invention, since the presence or absence of reverse power flow can be determined by the power conditioner itself, an external power measurement unit or the like becomes unnecessary, and control according to the presence or absence of reverse power flow is performed. be able to. Even if the power suppression control start condition such as the system voltage exceeding 107V is satisfied, if the power flow is not reversed and all the generated power is consumed by the on-site electrical load, the output power Without reducing the effective power, all the generated power can be output to the on-site electric load, and the generated power can be efficiently used even in an area where the system voltage is chronically high. When the effective power of the output power is reduced during the output suppression control, the active power is rapidly increased with a gradient that can reduce the output power to 0 W within a predetermined time (500 milliseconds) defined in the grid connection regulations. It is preferable to stop the reduction of the active power at the time when it is detected that the reverse power flow has stopped.

  In the power conditioner of the present invention, even when the output suppression control start condition is satisfied, when the reverse power flow determination unit determines that the reverse power flow is not flowing, an increase in the effective power of the output power is allowed. It may be configured (claim 2). According to this, even when the power suppression control start condition is satisfied due to the high system voltage, the active power can be increased within the range where no reverse power flow occurs, and the on-site electrical load can be operated with the generated power. Preferably, in order to prevent hunting, it is preferable to control the output power so that the minimum predetermined power (for example, 10 W) is purchased from the commercial power system.

  And a current transformer detection signal input unit for detecting a current value flowing from the commercial power system to the premises electric load, wherein the reverse power flow determination unit is configured to perform reverse power flow based on the current transformer detection signal input to the input unit. It is possible to determine the presence or absence of (claim 3). In this way, the reverse power flow determination means is built in the power conditioner, and the power conditioner alone detects the presence or absence of reverse power flow by supplying the current transformer detection signal to the reverse power flow determination means via the input unit. In addition, it is possible to increase the response speed of control depending on the presence or absence of reverse power flow, and to easily and flexibly design a control configuration for effective use of generated power while complying with the grid connection regulations. .

  As described above, according to the power conditioner of the first aspect of the present invention, the presence or absence of reverse power flow can be determined by the power conditioner itself, so that an external power measurement unit or the like is not necessary and Control according to the presence or absence of tidal current can be performed. Even if the power suppression control start condition such as the system voltage exceeding 107V is satisfied, if the power flow is not reversed and all the generated power is consumed by the on-site electrical load, the output power Without reducing the effective power, all the generated power can be output to the on-site electric load, and the generated power can be efficiently used even in an area where the system voltage is chronically high.

  According to the power conditioner of claim 2 of the present invention, even when the power suppression control start condition is satisfied due to the high system voltage, the active power is increased within a range in which no reverse power flow occurs, and the generated power The on-site electrical load can be activated.

  Further, according to the power conditioner of claim 3 of the present invention, the reverse power flow determination means is built in the power conditioner, and the detection signal of the current transformer is supplied to the reverse power flow determination means through the input unit. It is possible to detect the presence or absence of reverse power flow with the inverter alone, and to increase the response speed of control based on the presence or absence of reverse power flow, effectively using generated power while complying with the grid connection regulations. Therefore, it is possible to easily and flexibly design the control configuration for this purpose.

It is a block block diagram of the electric power generation system which concerns on one Embodiment of this invention.

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

  FIG. 1 shows a photovoltaic power generation system according to an embodiment of the present invention. The power generation system uses a power conditioner 2 to generate direct-current power generated by a power generation unit mainly composed of solar cell panels 1a and 1b. The AC power is converted into AC power and connected to a single-phase three-wire commercial power system so that the AC power is supplied to the on-site electrical load 3 and the surplus power is reversely flowed to the commercial power system. . The outputs of the plurality of solar cell panels 1a and 1b are once collected in the booster connection box 4, and the generated power is boosted to a constant voltage and then input to the power conditioner 2.

  A single-phase three-wire lead-in line composed of a U phase, a V phase, and an N phase of a commercial power system is connected to a switchboard 7 via a power purchase meter 5 and a power sale meter 6. The switchboard 7 is provided with an ampere breaker 8 (contract breaker), an earth leakage breaker 9 and a safety breaker 10, and system power is supplied to the premises electrical load 3 via these breakers 8, 9, 10. The output of the power conditioner 2 is connected in parallel to the system at a connection portion 13 between the ampere breaker 8 and the earth leakage breaker 9 via the power generation breaker 12.

  Further, a current transformer 14 for detecting a current value flowing from the commercial power system toward the premises electric load is provided outside the connection portion 13, and the current transformer 14 is connected to the power conditioner 2. It is electrically connected so that a detection signal is output to the power conditioner 2.

  The power conditioner 2 has the same basic internal configuration as a conventionally known one, but includes a detection signal input unit 2a of the current transformer 14 and is built in based on the detection signal input to the input unit 2a. The point which determines whether the reverse power flow is carried out by the microcomputer (reverse power flow determination means) is a characteristic configuration different from the conventional one. That is, a control unit including a microcomputer and an inverter drive circuit, a DC / DC converter that boosts and outputs the generated power from the power generation unit, and an inverter that performs DC / AC conversion on the output of the converter, Since the configuration in which the output is the output of the power conditioner 2 is conventionally known, the illustration is omitted. Note that the connection box 4 can also serve as a DC / DC converter. In this case, the power conditioner 2 does not need to incorporate a DC / DC converter. The power conditioner 2 is provided with an instrument transformer (system voltage detecting means) for detecting the system voltage at the system connection point. The instrument transformer is electrically connected to the control unit. The system voltage detection value is connected to the control unit.

  Then, in the built-in microcomputer, the average purchased power per unit time is calculated based on the detection signal of the current transformer 14 and the system voltage detection value. If this average purchased power value is a positive value, a reverse power flow is generated. On the other hand, if the average purchased power value is a negative value, it can be determined that a reverse power flow has occurred. Thus, the microcomputer functions as purchased power calculation means and reverse power flow determination means.

  When the system voltage does not satisfy the predetermined output suppression control start condition, the control unit outputs all the generated power to the premises, and controls the output power so as to allow a reverse power flow to the commercial power system. That is, by controlling the output so that the output voltage is slightly higher than the system voltage, the surplus power that cannot be consumed by the premises electrical load 3 is controlled to flow backward to the commercial power system due to the potential difference. In addition, when almost all of the generated power is consumed on the premises, the output voltage of the power conditioner 2 drops, so that power flows from the commercial power system to the premises.

  The control unit also includes a reactive power control unit that suppresses an increase in the system voltage by controlling a power factor of the output AC power, an output suppression control unit that suppresses the active power of the output, and a system voltage A disconnection control means for disconnecting the power generation system from the system when a predetermined voltage defined in the grid interconnection regulations is exceeded is provided. Each of these means may be realized by sequence control of a microcomputer, may be constituted by an FPGA, or may be realized by a dedicated control circuit for each means.

  The reactive power control means performs power factor control of the output mainly by controlling the inverter, and keeps the system voltage higher than a predetermined voltage rise suppression control start voltage (eg, 106 V) for a certain time (eg, 3 minutes to (30 minutes) If it continues, reactive power control is started, the phase of the current output with respect to the system voltage is shifted stepwise, and the reactive power is increased until the power factor reaches 85%. If the system voltage becomes lower than the voltage rise suppression control start voltage during the control, the reactive power control is terminated.

  The output suppression control means suppresses the active power of the inverter output by the converter output control or the inverter PWM control, and the system voltage continues to rise even by the reactive power control, and the voltage increase suppression control start voltage When the system voltage becomes higher than a higher predetermined output suppression control start voltage (for example, 107 V), the output suppression control is started. When the system voltage becomes lower than the output suppression control start voltage, the output suppression control is ended.

  In the output suppression control in the power conditioner 2 of the present embodiment, the active power is sharply reduced when it is determined that the microcomputer is in reverse power flow. This reduction in active power is determined by obtaining an output suppression gradient that can reduce the active power output of the power conditioner 2 to 0 W within a predetermined time (500 milliseconds) defined in the grid connection regulations. It is preferable to reduce the active power stepwise every 10 milliseconds according to the gradient. And every time it decreases by one step or several steps, the presence or absence of reverse power flow is re-determined, and when the reverse power flow stops, the decrease in active power can be stopped.

  On the other hand, when it is determined that the microcomputer is not in reverse power flow, it is prohibited to decrease the active power, and the active power is gradually increased in a range where the reverse power flow is not achieved. Even if this output increase is made, if the reverse power flow is not made, the increase will be consumed by the on-site electrical load 3 and will not adversely affect the commercial power system. It is preferable to control the power (for example, 10 W) so as to increase the output as much as possible while maintaining the purchased state. In addition, even if it is controlled to maintain the state of purchasing predetermined power, a reverse power flow may temporarily occur due to fluctuations in the power consumption of the premises electrical load, but in that case, as described above The active power is drastically decreased until no reverse power flow occurs.

  The disconnection control means disconnects the power conditioner 2 from the system by operating a circuit breaker built in the inverter when a predetermined disconnection condition is satisfied. As the predetermined disconnection condition, For example, it can be made a condition that it is not less than the disconnection threshold (for example, 109 to 112 V) higher than the output suppression control start voltage and the output power of the power conditioner 2 is 0 W. Under such conditions, in the absence of reverse power flow, the output of the power conditioner 2 can be continuously supplied to the premises electrical load 3 without being disconnected even if the system voltage exceeds the disconnection threshold. In this embodiment, since the reverse power flow prevention control is performed as described above, even if the system voltage exceeds the disconnection threshold during reverse power flow, the inverter gate is not disconnected. It is also possible to release the gate block instantaneously by the block and then gradually increase the output within the range where the reverse flow does not occur by releasing the gate block.

  The present invention is not limited to the above-described embodiment, and the design can be changed as appropriate. For example, in the above embodiment, the detection signal of the current transformer 14 is directly input to the power conditioner 2, but the detection signal is input to a power measurement unit separated from the power conditioner 2, and the purchased power and It is also possible to detect the presence or absence of a reverse power flow and output it to the power conditioner 2. In addition, the control unit constituting the reverse power flow determination means may be provided in a case different from the inverter that mainly constitutes the power conditioner 2, but it is assumed that it is provided in the same case. preferable.

DESCRIPTION OF SYMBOLS 1 Solar cell panel 2 Power conditioner 3 On-site electric load 14 Current transformer

Claims (3)

The system is connected to the commercial power system to output the generated power to the on-site electrical load, and when the system voltage does not satisfy the predetermined output suppression control start condition, the output power can flow backward to the commercial power system. In a power conditioner for controlling the output power,
A reverse power flow determining means for determining whether or not the output power is flowing backward into the commercial power system is provided, and even if the output suppression control start condition is satisfied, the active power of the output power is calculated if the reverse power flow is not performed. A power conditioner configured to reduce the active power of the output power only during reverse power flow without being reduced.   2. The power conditioner according to claim 1, wherein even if the output suppression control start condition is satisfied, an increase in the effective power of the output power is permitted when the reverse flow determination unit determines that the reverse flow is not flowing. A power conditioner that is configured as described above.   The power conditioner according to claim 1 or 2, further comprising a current transformer detection signal input unit for detecting a current value flowing from the commercial power system to the premises electric load, wherein the reverse power flow determination means is input to the input unit. A power conditioner that determines the presence or absence of reverse power flow based on a detected current transformer detection signal.

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