JPH04153713A - Bidirectional power conversion device - Google Patents

Abstract

PURPOSE:To preclude an electric shock accident in repairing operation for a commercial power failure detecting the power commercial failure from the drop of active power to zero and disconnecting the commercial power source from a converting circuit. CONSTITUTION:When the power failure occurs to the commercial power source 1, the electric power which is supplied from the side of the commercial power source 1 so far is not supplied, so the output of an active power detector 7 can not be held plus. At this time, the output of the detector 7 shifts from a plus value to zero. The detector 7 itself detects this variation and sends its detection signal to a comparator 71, which recognizes the occurrence of the power failure to open an exception switch 3, which disconnects the commercial power source 1 from the converting circuit 2 and isolates it from a solar battery 6. Consequently, even if the solar battery 6 continues to generate electric power during the repair of the commercial power source 1, there is no danger of an electric shock.

Description

[Detailed description of the invention] (a) Industrial application field The present invention is a device that uses both DC generated power by a solar cell and power supplied from a commercial power source, and is equipped with a DC load such as a household inverter air conditioner on the DC side. , relates to a bidirectional power converter equipped with an AC load such as household electrical equipment on the AC side,
In particular, the present invention relates to a control unit that disconnects a commercial power source from a solar cell during a commercial power outage.

(b) Conventional technology When operating the inverter of a commercial power system and a private power generation facility in parallel, a separately excited inverter device as shown in Japanese Patent Application Laid-open No. 55-94584, is The inverter operation inevitably becomes inoperable and stops functioning.

On the other hand, in the case of a self-commutated inverter device, it is possible to operate it independently in the event of a power outage in the grid.

Therefore, if a power outage occurs and the circuit breaker trips and the system is opened, the system will be charged by the 8-volt voltage of the inverter, causing problems in terms of safety and protection during maintenance work. .

Therefore, it is necessary to disconnect the inverter from the grid at the same time as the power grid enters a power outage state.

(c) Problems to be solved by the invention The problems to be solved by the present invention are to detect a power outage and transfer power to the commercial power source for safe and stable grid-connected operation of a power converter connected to a commercial power source. The goal is to prevent reverse power flow.

(d) Means for Solving the Problems The present invention provides a commercial power source, a bidirectional power conversion circuit connected to the commercial power source via a disconnection switch, and a bidirectional power conversion circuit connected to the connection point between the switch and the commercial power source. a DC load connected to the power conversion circuit; a solar cell connected to a connection point between the DC load and the power conversion circuit; and active power detection for detecting the active power of the commercial power source. means and
The bidirectional power conversion device includes a control section that opens and closes the switch and controls the power conversion circuit based on the detection output of the detection means.

(e) Detecting the active active power and controlling the bidirectional power conversion circuit, and opening the disconnection switch to disconnect the commercial power source from the bidirectional power conversion device.

(F) Embodiment The present invention has the basic configuration of the block circuit diagram shown in FIG. In the figure, 1 is a commercial power source, and 2 is a device that is connected via a disconnect switch 3 and converts AC input from the commercial power source 1 into DC, or converts DC input from the opposite direction into AC and converts the AC input from the commercial power source 1 into AC. 1 is a bidirectional power conversion circuit that regenerates electricity; 4 is a domestic load as an AC load connected to the connection point between the switch 3 and the commercial power source 1; 5 is an inverter air conditioner or the like connected to the conversion circuit 2; A DC load 6 with a built-in inverter is a solar cell connected to a connection point between the DC load 5 and the conversion circuit 5, and supplies DC power to the DC load 5 together with the conversion circuit 5.

7 is an active power detector connected to the commercial power source 1 and detects the active power of the power source 1 by detecting the output voltage and current from the power source 1; 8 is connected to the active power detector 7; A function generator 9 generates a predetermined output signal based on the input from the detector 7, and an adder 9 receives the output of the generator 8 as one input. The detected value of the active power detector 7 is compared with a reference value in a comparator 71, and the parallel disconnect switch 3 is controlled by the signal from the comparator 71. These active power detector 7 and comparator 71 constitute a control section 72.

10 is a band pass filter inserted between the domestic load 4 and the disconnection switch 3 to extract the fundamental wave component of the voltage of the commercial power supply l flowing therethrough; 11 is the same as the domestic load 4 and the switch. This is a current detector inserted between the power converter circuit 2 and the power converter circuit 3 to detect the current supplied from the power converter circuit 2 to the commercial power supply l side.

12 is a current detector inserted between the DC load 5 and the solar cell 6 to detect the current of the solar cell 6 flowing therethrough; 13 is a current detector that detects the input current from the current detector 12 and the solar cell 6; CPLj (Cen
tral Processing TJnit). This CPU calculates a gain to track the optimal operating point of the solar cell using the input current signal and the input voltage signal, outputs this gain signal to the D/A converter 13, and outputs the gain signal to the D/A converter 13. converted to an analog signal.

15 is a multiplier that multiplies the output signal of the filter 10, that is, the power supply voltage fundamental wave component, and the output signal of the D/A converter 13, that is, the gain, to calculate and output the current command value of the conversion circuit 2; 16 is a triangular wave generator that generates a triangular wave signal.

The adder 9 inputs the outputs of the multiplier 15, the current detector 11, and the function generator 8, and uses the current command value of the multiplier 15 to detect the bidirectional converter 2 detected by the current detection #11. A signal obtained by subtracting the output signal from the function generator 8 and the correction output signal from the function generator 8 is output. A comparator 17 is connected to the output of the adder 9 and the output of the triangular wave generator 16, which compares these signals and outputs a switching pulse to the conversion circuit 2 to control the conversion circuit 2.

Incidentally, as shown in FIG. 2, the output of the function generator 8 (second
The vertical axis in the figure) is the input active power detection @7 output signal (
(horizontal axis in Fig. 2); in other words, no output is produced even if the input decreases up to an appropriate specified value, and below the specified value, the output is proportional to the decrease in the input. Set it so that the output increases.

Now, during normal inverter operation, the decoupling switch 3 is closed, and the output of the solar cell 6 is supplied to the DC load 5, and at the same time, a part of it enters the bidirectional conversion circuit 2 and is converted into orthogonal current. Thereafter, it is supplied to the household load 5 via the switch 3. At this time, the power of the commercial power supply 1 is simultaneously supplied to the domestic load 4, and the domestic load 4 is driven by the power generated by the solar cell 6 partially supplemented by the power of the commercial power supply 1.

During this time, as the solar energy received by the solar cell 6 increases, the output of the solar cell 6 increases, and the power consumed by the domestic load 4 of the commercial power source 1 decreases, but the active power of the commercial power source 1 reaches a predetermined level. Until the value decreases to a positive value, the output voltage and current of the solar cell 6 are adjusted by the control signal of the CPIj 13 so that the solar cell 6 generates power at the optimum operating point.

In this way, when the power generated by the solar cell 6 increases and the active power of the commercial power supply 1 decreases to the specified value, the function generator 8 generates an output corresponding to the amount of decrease, and via the addition IS 9 and the comparator 17, performs bidirectional conversion. Sends a command signal to circuit 2. The conversion circuit 2 receives this signal, reduces its output signal, and operates while maintaining the positive state of the active power of the commercial power source 1. Therefore, it is possible to prevent a reverse power flow phenomenon in which the power generated by the solar cell 6 flows from the conversion circuit 2 to the commercial power supply 1. As a result, it becomes possible to always continue to supply a certain amount of power to the domestic load 4 from the commercial power supply l side.

By the way, when a power outage occurs in the commercial power source 1, the power that has been supplied from the commercial power source 1 until now is no longer supplied, making it impossible to maintain a positive output from the active power detector 7.

At this time, the output of the detector 7 shifts from a positive value to zero. The detector 9 #7 itself detects this change and sends this detection signal to the comparator 71. The comparator 71 recognizes the occurrence of a power outage, opens the disconnection switch 3, and disconnects the commercial power supply 1 from the conversion circuit 2. Separate. By this operation, the commercial power source 1 is insulated from the solar cell 6, and even if the solar cell 6 continues to generate electricity while the commercial power source 1 is being repaired, there is no fear of electric shock.

When the commercial power supply 1 is restored, the supply of power from the commercial power supply 1 to the domestic load 4 is started again.

At this time, the active power detector 7 detects the active power of the commercial power source 1, and the output of the active power detector 7 becomes a positive predetermined value. In response to this, the comparison @71 recognizes the end of the power outage and closes the series disconnection switch 3.

In this way, the control unit 72 reliably executes control during a power outage and restoration of the commercial power supply 1, thereby significantly increasing the safety of the system.

(g) Effects of the Invention As explained above, the present invention adjusts the output current of the conversion circuit by detecting the amount of decrease in the active power of the commercial power source during normal operation, and transfers the output current from the solar cell side to the commercial power source side. In addition to preventing reverse power flow, in the event of a commercial power outage, it is possible to detect a power outage by shifting the active power to zero, making it possible to disconnect the commercial power from the conversion circuit, and as a result, repair work in the event of a commercial power outage becomes easier. This has the effect of preventing electric shock accidents inside.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram showing the basic configuration of the bidirectional power converter of the present invention, and Fig. 2 is a diagram showing the input/output characteristics of a function generator using the output signal of the active power detector shown in Fig. 1 as input. be. ...commercial power supply, ...bidirectional power conversion circuit, ...coupling switch, ...domestic load, ...DC load, ...solar cell, ...active power detector, ...Function generator.

Claims (1)

[Claims] (1) A commercial power source, a bidirectional power conversion circuit connected to the commercial power source via a disconnection switch, an AC load connected to a connection point between the switch and the commercial power source, and a bidirectional power conversion circuit connected to the commercial power source via a disconnection switch; a connected DC load, a solar cell connected to a connection point between the DC load and the power conversion circuit, an active power detection means for detecting the active power of the commercial power supply, and a detection output of the detection means to detect the A bidirectional power conversion device comprising: a control unit that opens and closes a switch and controls the power conversion circuit.