JPH01263806A - Inverter device - Google Patents

Abstract

PURPOSE:To prevent an overcurrent by using a current/voltage instantaneous value control circuit and its switch circuit against the common main circuit constitution and a PWM pulse amplifying circuit. CONSTITUTION:A power generation system includes a DC power supply 1 like a solar battery, etc., an inverter device 2, an output filter 3, an AC transformer 4, an AC breaker 5, a load changeover switch 6, an electric power system 7, and a load 8. The inverter device 2 contains a self-exciting inverter main circuit 21, an instantaneous current value control circuit 22, an instantaneous voltage value control circuit 23, a control output switch 24, and a gate pulse amplifying/ distributing circuit 25. The circuit 22 is used in an interlocking operation mode and works in a self-exciting system. While the circuit 23 is used in an independent operation mode and works also in a self-exciting system. Thus both circuits 22 and 23 are operable by switching the circuit 22 to the circuit 23 when the power is supplied to the load 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an inverter device that converts DC power into AC power and supplies power to a power system or a general load.

(Prior Art) Development of new power generation systems that convert direct current power from solar cells, fuel cells, etc. into alternating current power using an inverter to supply power to power grids or general loads is underway both domestically and internationally.

As is well known, inverters are broadly classified into separately excited type and self-excited type, but inverters up to MW class often use self-excited type using transistors or GT○ thyristors as main circuit switching elements, and even AC The output is made to have a waveform as close to a sine wave as possible by pulse width modulation (PWM) and a filter.

Conventionally, this sine wave AC output was often obtained in the form of voltage, but in systems connected to the power grid, the grid impedance is small, so even small voltage fluctuations can cause large changes in the current flowing from the inverter to the grid. Therefore, there are many cases in which an "instantaneous current value control method" that controls the current waveform from moment to moment is applied.

On the other hand, when power is supplied to a general load, since a current corresponding to the load impedance needs to flow, a sine wave AC output is obtained in the form of voltage as before. The so-called CVCF (constant voltage, constant frequency) type is the mainstream.

Therefore, depending on whether the inverter supplies power to the power grid or to general loads, it is common practice to prepare dedicated inverter devices for each.The former is called the grid-connected type, and the latter is called the independent power type. I'm here.

(Problem to be solved by the invention) However, there are cases where it is desired to use the same inverter for both.In this case, it is possible to deal with this by using a system that obtains AC output in the form of voltage, but in the case of grid connection, However, as mentioned above, there is a problem in that the current fluctuation is large.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inverter device in which an excessive current does not flow when one inverter is connected to both an independent load and an electric power system.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, in the present invention, the main circuit configuration of the inverter device is common, and the control circuits include an instantaneous current value control circuit (A) and an instantaneous voltage value control circuit ( B) and a switching circuit for switching to either of them.

(Function) In the inverter device configured as described above, when connecting to the power grid, the control circuit (A) is switched to the control circuit (A), and when supplying power to the general load, the control circuit (B) is switched to the control circuit (B). It will also be possible to drive.

(Example) The figure is a configuration diagram of a power generation system using an inverter device according to an example of the present invention.

1 is a DC power source such as a solar cell or a fuel cell, 2 is an inverter device of this embodiment, 3 is an output filter, 4 is an AC transformer, 5 is an AC breaker, 6 is a load changeover switch, 7 is a power system, and 8 is a This is a general load. In the inverter device 2, 21 is a self-excited inverter main circuit, 22 is an instantaneous current value control circuit (A), 23 is an instantaneous voltage value control circuit (B), 24
25 is a control output switch; 25 is an amplification/distribution circuit for gate pulses to a group of switching elements (transistors, GTO thyristors, etc.) constituting the inverter main circuit 21;
It is operated by the output signal of the control circuit (A) or (B).

1. Since the usually required DC circuit breaker, DC voltage and AC voltage, current detection elements and their circuits are well known, their display and description will be omitted.

The instantaneous current value control circuit (A) 22 is used in the case of grid-connected operation. In other words, the PWM control signal compares the magnitude and phase of the reference sine wave signal created from the system voltage 9 frequency and the reference current signal and the output current detection signal from time to time, and performs feedback control to eliminate the deviation. This is a circuit that outputs , and operates separately excited. in this case,
The changeover switch 6 is connected to the grid side, and the changeover switch 24 is connected to the A side.

The voltage instantaneous value control circuit (B) 23 is used for independent operation. In other words, it is a circuit that outputs a PWM control signal that performs feedback control to eliminate deviations by comparing the two phases of the constant voltage, constant frequency reference sine wave signal and the output voltage detection signal every moment. Yes, it operates with self-excitation.

In this case, the changeover switch 6 is connected to the general load side, and the changeover switch 24 is connected to the B side.

The output signals of both the control circuits (A) and (B) are given to the gate pulse amplification distribution circuit 25 via the changeover switch 24, and the DC power of the DC power supply 1 is sent to the inverter main circuit 21.
．． Output filter 3. AC transformer 4° AC breaker 5.
Via the changeover switch 6, it is supplied to the power system 7 or the general load 8 in the form of a predetermined current or voltage.

The voltage instantaneous value control circuit (B) in the present invention may be a voltage control circuit used in another so-called "voltage type inverter" system.

[Effects of the Invention] As explained above, according to the present invention, when converting DC power from a DC power source into AC power using a self-excited inverter and supplying a predetermined power to a power system or general load, a common The main circuit configuration and PWM pulse amplification distribution circuit are equipped with an instantaneous current value control circuit (A), an instantaneous voltage value control circuit (B), and their switching circuits, making it suitable for both grid-connected operation and independent operation. Accordingly, it is possible to provide an inverter device that allows the selection of different control methods.

[Brief explanation of the drawing]

The figure is a circuit configuration diagram showing an embodiment of the present invention. 1... DC power supply 2... Inverter device 3.
... Output filter 4 ... AC transformer 5 ... AC breaker 6 ... Load changeover switch 7 ... Power system 8 ... General load 21 ... Self-excited inverter main circuit 22 ... Current Instantaneous value control circuit (A) 23... Voltage instantaneous value control circuit (B) 24... Control output changeover switch 25... Gate pulse amplification distribution circuit Agent Patent attorney Noriyuki Chika Yudo Ken Daishimaru

Claims (1)

[Claims] In a self-excited inverter device that converts DC power from a DC power supply into AC power and supplies power to the power grid or general load, the inverter control circuit is equipped with an instantaneous current value control circuit (
It is equipped with two control circuits: A) and a voltage instantaneous value control circuit (B), and a switching circuit for switching to either of them. When supplying power to the power grid, the switching circuit switches the control circuit (A) to the An inverter device characterized in that when power is supplied to a general load, switching is performed to a control circuit (B).