JPH0467729A - Reverse charge preventing system for distributed power supply - Google Patents

Abstract

PURPOSE:To reliably reverse charging of a distributed power supply by connecting a load for reverse power flow at a point closer to the power system side than a point where a reverse power flow detecting means is connected with a drop wire thereby generating reverse power flow upon opening of a circuit breaker. CONSTITUTION:Upon opening of a circuit breaker 15 in a power system 10, no power is fed from the power system 10 to a domestic load 23. In other words, reverse power flows through a reverse power flow monitoring point Z. When a reverse power flow detecting circuit 24 detects reverse power flow for a predetermined time or longer, an output control circuit 25 makes a judgment that the circuit breaker 15 is opened and interrupts output from am inverter 22. According to the arrangement, reverse charging from a distributed power supply 20 can be prevented.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention provides a method for charging the power system when a distributed power source operating in connection with the power system is separated from the power system on the power system side.
The present invention relates to a reverse charging prevention device for a distributed power source that prevents reverse charging.

[Conventional technology] In recent years, distributed power sources such as solar power generation have been installed on the consumer side, and the power from the distributed power sources is supplied to domestic loads, and the amount of power that cannot be covered by that power alone is also used. Systems have been developed that supply electricity through interconnection with the power grid.

However, in such a system interconnected with the power grid, for example, if an accident occurs on the distribution line or work is being done on the distribution line, it is necessary to open the circuit breaker installed on the distribution line. The power supply from the main power source of the power grid has been stopped. However, if voltage from distributed power sources is supplied to distribution lines, it may be impossible to eliminate accidents or it may be extremely dangerous for workers. For this reason, a device is installed that detects when the circuit breaker is opened and disconnects the distributed power source from the power system.

[Problems to be Solved by the Invention] By the way, when a distributed power source is interconnected with an electric power system, there are systems in which reverse power flow is recognized and systems in which reverse power flow is not recognized. The present invention relates to a charging prevention device that is applied to a system in which no reverse power flow is allowed.

Conventionally, the circuit breaker is opened using a method in which an opening detection circuit detects abnormalities in the frequency or voltage within the distributed power system. If the power generated by the distributed power source was balanced to some extent, it was not possible to detect the opening of the circuit breaker on the distribution line.

FIG. 2 shows an example in which an opening detection circuit 6 for detecting opening of a circuit breaker is applied to a system in which no reverse power flow occurs, that is, a system in which no reverse power flow is recognized.

In Figure 2, 1 is a distributed power source such as solar power generation, 2 is a domestic load, 3 is a reverse power flow detection circuit that detects when the power of the distributed power source 1 reverses, and 4 is a reverse power flow detection circuit. circuit 3
5 is a circuit breaker provided on the distribution line 8, S is a circuit breaker that disconnects the distributed power source 1 from the power system K, and 6 is a distributed power supply circuit. An opening detection circuit detects the opening of the circuit breaker 5 from the frequency fluctuation and voltage fluctuation in the system of the type power supply 1 and opens the circuit breaker S, 7 is the main power supply of the power system, 9 is the drop-in line, and R is monitoring the reverse power flow. It is a monitoring point.

In a system where reverse power flow is not recognized, the output control circuit 4 controls the output of the distributed power source 1 so that reverse power flow does not occur at the monitoring point 9.

Now, when the circuit breaker 5 of the distribution line 8 is opened, the power supply from the main power source 6 of the power system is stopped, and only the power from the distributed power source 1 is supplied to the domestic load 2.

At this time, if the power of the distributed power source 1 and the domestic load 2 are balanced to some extent, even if the circuit breaker 5 is opened, the changes in voltage and frequency fluctuations within the system of the distributed power source 1 will be small, and an opening will be detected. There was a problem in that the opening of the circuit breaker 5 could not be detected by the circuit 6.

[Purpose] This invention was made in view of the above-mentioned problems, and its purpose is to provide a power grid interconnection system in which reverse power flow is not allowed, and in which reverse power flow occurs when a circuit breaker is opened. It is an object of the present invention to provide a reverse charging prevention device for a distributed power source that can reliably prevent reverse charging of a distributed power source by generating a power flow and detecting the reverse power flow.

[Means for Solving the Problem] In order to achieve the above object, the present invention is a system that supplies power from a distributed power source to a load and supplements power that cannot be covered by the power alone from the power system. , reverse power flow detection means for detecting the reverse power flow when the power of the distributed power source reversely flows so as to be supplied to the power grid; A reverse charge prevention device for a distributed power source, comprising: output control means for stopping the output of the distributed power source; It is characterized by connecting.

[Function] With the above configuration, the power flow at the connection point to which the reverse power flow detection means is connected does not become a reverse power flow in normal times, and the reverse power flow load is connected to the power grid side from the connection point. Therefore, the power flow of the service line is always receiving power, and reverse power flow does not occur.

However, when the power supply from the power system is stopped by opening a circuit breaker provided on the power system side, power from the distributed power source is supplied to the load and the load for reverse power flow. Since the load for reverse power flow is connected to the power grid side from the connection point where the reverse power flow detection means is connected to the service line, the distributed power source is configured so that the reverse power flow detection means detects the reverse power flow and prevents the reverse power flow. Even if the output is controlled, the power of the distributed power source will flow in reverse and be supplied to the load for reverse power flow. Then, the reverse power flow detection means detects the reverse power flow, and when the reverse power flow detection means detects the reverse power flow for a certain period of time or more, the output control means stops the output of the distributed power source.

[Example] Hereinafter, an example of the reverse charge prevention device for a distributed power source according to the present invention will be described based on the drawings.

In FIG. 1, 10 is a power system, and this power system 10 includes a main power source 12 of a power plant 11 and a distribution substation 13.
, a distribution line 14 , and a circuit breaker 15 interposed in the distribution line 14
and a pole transformer 16 and the like. The voltage of the power generated by the main power source 12 is stepped down to a predetermined voltage by a power distribution transformer 13, and is branched and transmitted through a plurality of power distribution lines 14. Branch power of the distribution line 14 is supplied to pole transformers 16 installed at various locations via circuit breakers 15, where 100V or 200V
The voltage is stepped down to (2) and supplied to each home etc. via a drop-in line 17.

Further, in FIG. 1, 20 is a distributed power source installed in each home, and this distributed power source 20 includes, for example, a solar cell 21 and an inverter that converts the DC power output from the solar cell 21 into AC power. 22nd magnitude. 23 is a domestic load, and F is a circuit breaker that is opened when disconnecting the distributed power source 20 from the power system 10.

24 is a reverse power flow detection circuit (reverse power flow detection means) that detects when power from the distributed power source 20 is supplied to the power grid 10 side, that is, when a reverse power flow occurs. Reference numeral 25 denotes an output control circuit (output control means), which delays the phase angle of AC conversion by the inverter 22 when the reverse power flow detection circuit 24 detects a reverse power flow, and controls the output of AC power output from the inverter 22. This reduces the Further, the output control circuit 25 is configured to stop the output of the inverter 22 when the reverse power flow detection circuit detects a reverse power flow for a certain period of time or more.

26 is a reverse power flow resistor (
(reverse power flow load). A reverse charge prevention device 30 is constituted by the reverse power flow detection circuit 24, the output control circuit 25, and the reverse power flow resistors M and 26.

Next, the operation of the reverse charge prevention device 30 configured as described above will be explained.

When DC power is output from the solar cells 21 of the distributed power source 20, the inverter 22 converts it into AC power of a predetermined frequency, and the AC power is supplied to the household load 23.

The amount of power that cannot be covered by AC power is then
Supplied from 0. Further, when power is supplied from the power system 10 to the reverse power flow resistor 26 and the power output from the inverter 22 becomes larger than the power consumption of the household load 23, a reverse power flow occurs. Since the reverse power flow is detected and the output control circuit 25 reduces the output of the inverter 22 so as not to generate the reverse power flow, the reverse power flow does not occur under normal conditions.

Here, the power output from the distributed power source 20 is Pl, the power supplied to the household load 23 is P2, the power at the connection point (reverse power flow monitoring point) Z of the reverse power flow detection circuit 24 is P3,
It is assumed that the power supplied to the reverse power flow resistor 26 is Pc, and the power at the interconnection point Q with other consumers is P4. Moreover, the direction of each arrow shall indicate the direction of the current.

The reverse power flow detection circuit 24 and the output control circuit 25 are connected to the distributed power supply 2 to prevent reverse power flow from occurring at the reverse power flow monitoring point Z.
Since the output of 0 is controlled, the following equation holds true.

P3=P2-PL≧O...■ P4=P3+Pc>O...■ Now, when the circuit breaker 15 of the power system 10 is opened, power from the power system 10 will no longer be supplied to the domestic load 23. . In addition, since reverse power flow does not occur in the distributed power sources (not shown) of other connected consumers (because the system is configured such that no reverse power flow occurs), the power P4 at the customer grid point Q becomes O.

Therefore, the equation (2) becomes 0=P3+Pc, resulting in P3Pc. Also, from P3=~Pc, equation 0 is Pl−P2+
It becomes a PC.

Tsumelever Reverse power flow will occur at reverse power flow monitoring point Z. This reverse power flow is handled by the reverse power flow resistor 26 at the monitoring point 2.
Since the inverter 22 is connected to the power grid 10 side, the output control circuit 25 prevents the output of the inverter 22 from causing reverse power flow.
Even if the voltage is lowered by , it will always occur if the circuit breaker 15 is opened. When the reverse power flow detecting circuit 24 detects this reverse power flow for a certain period of time or more, the output control circuit 25 determines that the circuit breaker 15 has been opened and stops the output of the inverter 22. In other words, reverse charging by the distributed power source 20 is prevented.

In this way, when the circuit breaker 15 is opened, a reverse power flow is sure to occur, so that when the circuit breaker 15 is opened, reverse charging can be reliably prevented.

In the above embodiment, the reverse power flow resistor 26 is attached to the leader line 17.
However, if a control circuit power supply device (not shown) for the inverter 22 is connected in place of this resistor 26, the power loss caused by the resistor 26 can be effectively utilized.

[Effects] As explained above, according to the present invention, in a power system interconnection system in which reverse power flow does not occur, reverse power flow always occurs when a circuit breaker is opened, thereby preventing reverse charging of distributed power sources. This can definitely be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a reverse charge prevention device for a distributed power source according to the present invention, and FIG. 2 is a block diagram showing the configuration of a conventional reverse charge prevention device for a distributed power source. 23... Domestic load (load) 24... Reverse power flow detection circuit (reverse power flow detection means) 25...
・Output control circuit (output control means) 26... Resistor for reverse power flow (load for reverse power flow) 20... Distributed power supply

Claims (1)

[Claims] A system that supplies power from a distributed power source to a load and supplements power that cannot be covered by that power alone from a power grid, and when the power from the distributed power source reverses to be supplied to the power grid, A reverse power source of a distributed power source comprising a reverse power flow detection means for detecting this reverse power flow, and an output control means for stopping the output of the distributed power supply when the reverse power flow detection means detects a reverse power flow for a certain period of time or more. A charging prevention device,
A reverse charge prevention device for a distributed power source, characterized in that a reverse power flow load is connected to a power system side from a connection point where the reverse power flow detection means is connected to a lead-in line.