JP5575046B2 - Grid connection power conditioner - Google Patents

Description

  The present invention relates to a power conditioner that links electric power generated by a solar battery to a commercial system, particularly when performing a test for confirming the function of a protective relay built into the power conditioner during normal grid connection operation. It is related with the structure of the voltage phase detection transformer for detecting the voltage of a system | strain and the phase which can respond to both.

  The grid-connected power conditioner converts the DC power generated by solar cells into AC power according to the frequency and voltage of commercial systems such as single-phase three-wire or three-phase three-wire by an electric power company using an inverter. Convert and output power to the commercial system. In order to output a current synchronized with the phase of the system voltage, the power conditioner that performs system interconnection needs to detect the voltage and phase of the system. Usually, a transformer is used to detect the phase, and the primary side of the transformer is configured with a system voltage, and the secondary side is configured with a winding ratio that outputs several volts that can be handled by the control circuit.

The power conditioner for grid connection is a power conversion function that converts DC power generated by solar cells into AC power, and grid connection protection that stops the power conditioner to stop photovoltaic power generation in the event of a grid failure A function is required, and the grid connection provision JEAC 9701-2010
The specifications of the protective relay to be installed are instructed. Among protective relays, overvoltage relays (OVR), undervoltage relays (UVR), frequency up relays (OFR), and frequency down relays (UFR) have been installed in most power conditioners in recent years. The function of a small capacity power conditioner such as a conditioner has been confirmed by a certification body.

  In order to confirm the function of the protective relay built in the inverter, a dedicated system simulation power supply is often used in the manufacturer's factory. During the completion inspection and maintenance inspection, as shown in Fig. 5, the output of the power conditioner was disconnected from the system, the power conditioner was set to the maintenance mode, and the system voltage and phase were detected during normal system interconnection operation. The connection of the transformer 9 is switched by the relay test switching relay 14 so that the voltage from the relay tester can be detected. The function of the protective relay is confirmed by applying a voltage from the outside to the inverter in a simulated manner using a relay tester. Currently, a relay tester called a cogeneration relay tester (for example, RCG-1C manufactured by Musashi Intec) is often used.

Japanese Patent No. 3796384 (FIG. 6 and its description)

  However, with the above technology, solar power generation, which has been increasing in capacity in recent years, may have a large capacity power conditioner linked to a 400V system, and in the above configuration, the relay test terminal Since the voltage to be applied must be the same as the system voltage, the test voltage of the cogeneration relay tester currently on the market can only support up to 200V system, and is often carried by maintenance and inspection companies. Since the relay tester is compatible only with the 100V applied voltage, it is not possible to test the protective relay mounted on the power conditioner linked to the 400V system.

  The present invention has been made in view of the above-described conventional situation, and a voltage (100V system) that can be generated by a commercially available standard relay tester generally carried by a maintenance / inspector is 400V system or the like. Easily conducts a confirmation test of the protective relay function of the power conditioner connected to the commercial power system, making it easy to test the protective relay installed in the power conditioner at the time of factory shipment, on-site inspection, and maintenance The purpose is to obtain a grid-connected power conditioner that can be implemented.

Power conditioner according to the present invention, it converts the DC power solar cell generates power into AC power by the inverter unit, the grid-connected power conditioner that outputs power to a commercial system, provided plurality primary winding A voltage phase detection transformer for detecting the system voltage of the commercial system, and by changing the connection of the plurality of primary side windings, even if the voltage applied to the primary side windings is different, the voltage voltage output to the secondary winding of the phase detecting transformer is a voltage Do that system Mitsururen system power conditioner comparable, the side and the commercial system of the solar cell when an accident of the commercial system A grid interconnection protection function for stopping the interconnection of the power supply system, and by changing the connection of the plurality of primary side windings, the turn ratio of the voltage phase detection transformer is tested for the grid interconnection protection function. Time is In which from smaller when the actual operation state.

According to the present invention, it converts the DC power solar cell generates power into AC power by the inverter unit, the grid-connected power conditioner that outputs power to a commercial system, the commercial primary winding is provided with a plurality A voltage phase detection transformer for detecting the system voltage of the system is provided, and the voltage phase detection transformer is changed even if the voltages applied to the primary side windings are different by changing the connection of the plurality of primary side windings. voltage output to the transformer secondary winding is a voltage Do that system Mitsururen system power conditioner comparable, interconnection of the side and the commercial system of the solar cell when an accident of the commercial system The grid connection protection function is stopped, and by changing the connection of the plurality of primary side windings, the turn ratio of the voltage phase detection transformer is the test of the grid connection protection function, When in actual operation Than smaller, because it can perform the test of the protective relay is built in the power conditioner by using a general relay tester on the market today, particularly 400V system by photovoltaic power generation has progressed in recent years capacity The operation confirmation test of the protective relay mounted on the power conditioner linked to the power system can be easily performed at the time of completion on site, maintenance inspection, and protection during the shipping test at the factory. Since the relay test can also be performed using a commercially available standard relay tester, it is not necessary to purchase expensive system simulation power supply equipment that includes a protective relay test function in the actual system voltage. The test can be carried out, and the quality inspection of the protective relay mounted on the power conditioner can be carried out.

It is a figure which shows Embodiment 1 of this invention, and is a block diagram which shows the structure of a grid connection power conditioner. It is a figure which shows Embodiment 1 of this invention, and is a figure which shows an example of the coil | winding form of a voltage phase detection transformer. In the figure which shows Embodiment 1 of this invention, when a power conditioner is a real driving | running state, in order to enlarge the turns ratio of a transformer, the primary winding of a transformer is connected in series and the number of turns of a primary side is increased. FIG. FIG. 5 is a diagram illustrating the first embodiment of the present invention, and is a diagram illustrating reducing the turn ratio by connecting all the primary windings of the transformer in parallel when performing a test of the protective relay in the power conditioner. . The internal block diagram of the conventional inverter is shown.

Embodiment 1 FIG.
In order to achieve the above-described object of the present invention, Embodiment 1 is a grid-connected power conditioner that converts DC power generated by a solar cell into AC power using an inverter and outputs power to a commercial system. In order to carry out the operation test of the protective relay mounted on the power conditioner using the standard relay tester currently on the market, especially in the power conditioner linked to the 400V system. By devising the connection of the primary side winding of the voltage phase detection transformer that detects the voltage, even if the voltage applied to the primary winding is different, the voltage output to the secondary winding becomes the same level voltage. A voltage phase detection transformer is installed in the power conditioner and applied to the primary winding by changing the connection of the primary winding of the phase detection transformer that detects the system voltage. By installing a voltage phase detection transformer in the power conditioner with the same voltage output to the secondary winding even if the pressure is different, the power conditioner can be operated using a general relay testing machine that is currently available on the market. Because it is possible to carry out tests on protective relays built into the power plant, in the field of photovoltaic power generation, which has been increasing in capacity in recent years, in particular, on-site testing of protective relays installed in power conditioners linked to 400V systems Because it is possible to easily perform inspections at the time of completion and maintenance inspections at the factory, and it is also possible to perform protection relay test at the time of factory shipment test using a commercially available standard relay testing machine. It is possible to perform a factory test without purchasing expensive system simulation power supply equipment that includes a protective relay test function for the actual system voltage, and is installed in the inverter. Quality inspection of the relay is also one that can be implemented.

  A preferred embodiment 1 of a system interconnection power conditioner according to the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, a grid-connected power conditioner (hereinafter simply referred to as “power conditioner”) 1 is provided between a solar cell 2 that generates DC power and a commercial power supply 3 of 50 Hz or 60 Hz. Be placed.
The commercial power source 3 is a single-phase three-wire system or a three-phase three-wire power distribution system.
The power conditioner 1 includes a boosting unit 4 for boosting the voltage of the solar cell 2 (there may be no boosting unit), and an inverter unit 5 that converts DC power generated by the solar cell 2 into AC power, A filter unit 6 is placed at the output of the inverter unit 5 to smooth the output current waveform of the inverter.
The control circuit 7 calculates the power of the solar cell from the voltage Vs of the solar cell and the solar cell current Is detected by the current sensor 8, detects the voltage and phase of the commercial power supply 3 by the voltage phase detection transformer 9, Outputs a current synchronized with the phase of the grid power supply.
The voltage phase detection transformer 9 is provided with a fuse 10 for protection coordination in case of a short circuit failure. In addition, a protective relay 11 for detecting that an abnormality has occurred in the system and that the voltage and frequency of the system have become abnormal is mounted inside the power conditioner, and the control circuit 7 is connected through the voltage phase detection transformer 9. Detects an abnormality, stops the output of the power conditioner 1, opens the electromagnetic contactor 12, and mechanically disconnects from the system. A circuit breaker 13 is installed on the AC output side of the power conditioner 1 to prevent inflow of overcurrent from the system due to an internal accident.

  FIG. 2 shows an example of the winding form of the transformer for detecting the voltage and phase of the commercial power supply used in the first embodiment.

  The primary winding of each phase of the transformer is composed of a plurality of identical windings for each phase, and a plurality of windings can be connected in both serial connection and parallel connection for each phase. It has become.

When the inverter is in an actual operation state, the primary winding of the transformer is connected in series as shown in FIG. 3, and the number of turns on the primary side is increased to increase the turns ratio of the transformer.
On the other hand, when carrying out the test of the protective relay in the power conditioner, all the primary windings of the transformer are connected in parallel as shown in FIG. 4 to reduce the turn ratio.
Therefore, when the voltage applied to the primary side of the transformer is large, the primary side winding is connected in series, and when the voltage applied to the primary side is small, the primary side winding is connected in parallel and the induced voltage on the secondary side is It is possible to keep it almost unchanged.

The voltage phase detection transformer can be connected in series or in parallel. The primary side winding is provided on the terminal block and connected by wiring, or the connection is automatically changed using a relay, etc. be able to.

  A specific example will be described below.

When the primary side winding of the voltage phase detection transformer is composed of four identical windings and connected in series, the primary side windings are all in parallel when the turn ratio with the secondary side is 50: 1. When this is done, the turns ratio is 12.5: 1.
For example, when the system voltage is 400 V, the primary windings of the voltage phase detection transformer are all connected in series during normal power conditioner operation. Since the winding ratio is 50: 1, the voltage induced on the secondary side with respect to the system voltage 400V is 8V. When the set value of the overvoltage relay (OVR) which is one of the protective relays is 120% (actual system voltage is 480V), the voltage induced on the secondary side of the transformer, that is, the detection voltage of the control circuit is 9.6V. Then, the control circuit stops the operation of the power conditioner as system overvoltage protection when a voltage of 9.6 V or more is detected for a specified time, and opens the interconnection electromagnetic switch to disconnect from the system.

  Next, when confirming the operation of the protective relay, the power conditioner stops the interconnection operation, and the control circuit in the power conditioner shifts to the maintenance mode for confirming the operation of the protective relay. Subsequent to the maintenance mode, the changeover switch provided on the control board is used. In this case, all the primary side windings of the voltage phase detection transformer are changed to the parallel connection. Since the recognized value of the control circuit of the power conditioner is 8V with respect to the average value of the actual system voltage of 400V, the primary side input voltage having the same recognized value (the secondary side of the transformer is 8V) has a turn ratio of 12.2. Since it is 5: 1, it becomes 100V. In order to test the function of the overvoltage relay (OVR) with a set value of 120%, the applied voltage for testing from the relay tester is gradually increased from 100V, and when the voltage exceeds 120V, OVR is detected from the inverter. This can be done by checking the test output signal. That is, when the output voltage of the relay tester is 120V, the detection voltage of the control circuit of the power conditioner is 9.6V because the winding ratio of the voltage phase detection transformer is 12.5: 1, and the power conditioner is actually connected to the system. It is possible to perform an accurate operation test of the protective relay in accordance with the voltage recognition value of the control circuit during the interconnection operation.

  As described above, the grid interconnection power conditioner according to the present invention divides the primary winding of the transformer for detecting the voltage and phase of the grid into a plurality of windings having the same number of windings, and is connected in series and in parallel. By using the connection together, the primary winding is connected in series during normal grid connection operation. When testing the protective relay mounted on the inverter at the time of factory shipment, on-site completion test, and maintenance inspection using a standard relay testing machine used by maintenance inspection companies By connecting the primary windings in parallel, the test can be easily performed with high accuracy. Therefore, without using an expensive cogeneration relay tester that tests by applying an actual voltage, a test of a protective relay mounted on a power conditioner is performed using a standard relay tester that is usually used by maintenance and inspection companies. Therefore, it is possible to always maintain and provide a high-quality inverter. In particular, for power conditioners linked to a 400V system, a relay tester that can directly apply a 400V system voltage, which is the actual system voltage, is not commercially available. Demonstrate the effect. In addition, it cannot be overemphasized that this invention can be diverted not only to the power conditioner for photovoltaic power generation but to the power converter connected to other systems.

  In the drawings, the same reference numerals denote the same or corresponding parts.

1 grid-connected power conditioner,
2 solar cells,
3 Commercial power supply,
4 Booster,
5 Inverter part,
6 Filter section,
7 Control circuit,
8 Current sensor (current transformer),
9 Voltage phase detection transformer,
10 fuses,
11 Protection relay mounted on the inverter
12 Magnetic contactor for grid connection,
13 Circuit breaker,
14 Relay test switching relay.

Claims (3)

Converts DC power solar cell generates power into AC power by the inverter unit, the grid-connected power conditioner that outputs power to a commercial system, it detects a system voltage of the commercial system the primary winding is provided with a plurality The voltage phase detection transformer includes a secondary side winding of the voltage phase detection transformer even if the voltage applied to the primary side winding is different by changing the connection of the plurality of primary side windings. a voltage to be output to the line a voltage Do that system Mitsururen system power conditioner comparable, the grid interconnection stop the interconnection of the side and the commercial system of the solar cell when an accident of the commercial system By providing a protection function and changing the connection of the plurality of primary side windings, when the voltage phase detection transformer turns ratio is tested during the grid connection protection function, the smaller it Grid-connected power conditioner to symptoms.   2. The grid-connected power conditioner according to claim 1, wherein a plurality of primary windings of each phase of the voltage phase detection transformer are provided, and the connection of the plurality of primary windings is changed for each phase. Thus, even if the voltage applied to the primary side winding is different, the voltage output to the secondary side winding of the voltage phase detection transformer becomes the same level voltage. Inverter. The grid interconnection power conditioner according to claim 1 or 2, further comprising a grid interconnection protection function for stopping the interconnection between the solar cell side and the commercial grid in the event of an accident in the commercial grid. The grid-connected power conditioner is characterized in that the primary side windings are connected in series during the actual operation and in parallel during the grid connection protection function test .

Images