JPH047667Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a harmonic generation device that is connected in parallel with a power source and generates a harmonic current for canceling harmonic current generated in a load, and relates to a control device for a harmonic suppression device.

FIG. 1 shows the configuration of a harmonic suppression device. A harmonic suppressor 3 is provided in parallel to the load 2 to supply power from the commercial power source 1 to the load 2. The harmonic suppression device 3 is
The magnitude of the harmonics generated in the load 2 is detected by the current transformer 4 and the current detection circuit 5, the current to be sent to the DC reactor 6 is determined according to this harmonic, and the self-extinguishing element such as the GTO thyristor is switched to the main switch. The bidirectional power converter 7 is controlled by pulse width modulation (PWM) or the like to inject or extract a current commensurate with the harmonics generated in the load 2 to the power source 1 side. 8 is a control circuit that modulates the PWM carrier wave according to the current detection signal to obtain a gate control signal, and 9 is a gate circuit that distributes and amplifies the gate control signal to control on/off of each main switch of the power converter 7. It is.

When performing normal PWM control to control the power converter 7, the control circuit 8, gate circuit 9, and converter 7
Due to unbalanced constants of various parts, a phase shift of the gate pulse and a delay in the response of the main circuit switch may occur, and a DC component may be included in the AC output for harmonic suppression. Although the purpose of the harmonic suppression device is to suppress and reduce harmonics, the DC component included in this AC output current has the problem of generating new harmonics of a lower order. Therefore, when a dedicated transformer is installed on the AC side of the power converter 7, attempts have been made to remove the low-order harmonic components by providing an air hole in the iron core of the transformer. This causes other problems such as an increase in noise.

The present invention detects the DC component included in the AC output current, and performs arithmetic correction in the PWM control circuit based on this detected value to reduce or eliminate the DC component, thereby solving the conventional problem of harmonics. It is an object of the present invention to provide a control device for a suppressor.

FIG. 2 shows an embodiment of the present invention. The same figure is the first
The parts that differ from the diagram are a current detector 10 that detects the AC output current of the power converter 7, and this current detector 1.
A DC component detector 11 that detects a DC component from a detection signal of The point is to adjust the control output of the control circuit 8. As the current detector 10, since a general current transformer is insufficient in terms of performance, a composite current detector using a Hall element or a resistor such as a shunt is used. Further, as the DC component detector 11, a waveform analyzer or the like is used. Control of the control circuit 8 using the detected DC component signal is achieved by adding an arithmetic circuit as a minor loop to the PWM control that reduces harmonic current to keep the area of the positive polarity side and negative polarity side of each phase current constant. be done.

Therefore, according to the present invention, it is possible to prevent a DC component superimposed on the AC output current of the harmonic suppression device or a harmonic current lower in order than the harmonic to be suppressed from flowing into the power supply 1 or the load side. In addition, by suppressing the DC component, even though a transformer is installed exclusively for the harmonic suppression device, it is not necessary to have an air core, which results in a reduction in noise generation from the transformer and DC biased magnetization. It is possible to suppress the rise in temperature of the transformer caused by this.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional harmonic suppression device, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1...Power source, 2...Load, 3...Harmonic suppressor, 5...Current detector, 6...DC reactor,
7... Power converter, 8... Control circuit, 9... Gate circuit, 10... Current detector, 11... DC component detector.

Claims (1)

[Scope of utility model registration request] In a harmonic suppression device that generates harmonic current from DC current by a power converter having a semiconductor switch configuration and cancels the harmonic current generated in a load, the DC component included in the harmonic suppression output of the power converter is and current detection means for detecting harmonic components lower than the harmonics to be harmonic suppressed, and a control minor loop using the detection signal from the current detection means to control the electric power in the direction in which the value of the detection signal becomes zero. 1. A control device for a harmonic suppression device, comprising: a control circuit that obtains a control output of a converter.