JPH0638537A - Pwm inverter with variable gain adaptive control function - Google Patents

Abstract

PURPOSE:To improve a distortion factor of an output voltage waveform without deteriorating stability at the time of loading a rectifier by instantaneously controlling an output voltage according to a gain adapted for a load mode. CONSTITUTION:The PWM inverter with a variable gain adaptive control function comprises a proportional element 2, a stabilized compensator 3, a comparator 6, an output voltage feedback circuit, etc. It detects a carrier signal included in an output voltage of a PWM inverter 7 through an adaptive compensator 20 having a high-pass filter 21, an absolute value detector 22, a low-pass filter 23 and a gain calculator 24, calculates a gain corresponding to the amplitude, and then feeds back it to the element 2. As a result, since the gain of the output signal from the element 2 becomes variable, a control signal for controlling the inverter 7 by the output signal can be switched to a gain adapted for the load mode. That is, a carrier component is used, thereby improving a distortion factor at the time of loading a rectifier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to UPS (Uninterrup
The present invention relates to an instantaneous control system of an output voltage in a PWM inverter that constitutes a tible power supply).

[0002]

2. Description of the Related Art Conventionally, a method for instantaneously controlling the output voltage of a PWM inverter is as shown in FIG. 2, which is fixed gain control. In FIG. 2, the voltage signal V detected from the output circuit of the PWM inverter 7 is fed back and input to the adder 1 to be added to the reference signal. The adder 1
The output signal of is input to the stabilizing compensator 3 via a proportional element 2'having a fixed gain. The output signal of the stabilization compensator 3 is added in the adder 4 with the reference signal u input via the feedforward path 8. Further, the output signal of the adder 4 is controlled by the comparator 6 together with the triangular carrier signal. The output signal of the comparator 6 becomes a control signal for controlling the PWM inverter 7. As described above, the output voltage instantaneous control system in the related art is controlled by a fixed gain, and
The carrier wave component included in the output voltage output from the PWM inverter was discarded as an unnecessary component.

[0003]

When constructing an instantaneous control system of the output voltage in the PWM inverter, the steady gain is determined from the specification of the distortion factor under the load of the rectifier, but this method tends to make the gain excessive. It has the drawback of impairing the stability under linear load. Conversely, if the gain is determined from the stability under linear load, it will be lower than the gain by the above method, but the distortion factor under rectifier load will be worse. The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and provides a PWM inverter having an adaptive control function for performing control while identifying a load state and calculating a gain according to the state. The purpose is to do.

[0004]

In order to achieve the above object, a PWM inverter having a variable gain adaptive control function according to the present invention includes a proportional element, a stabilizing compensator, a comparator, an output voltage feedback circuit, and the like. Prepared P
In the instantaneous control system of the output voltage of the WM inverter, PWM is performed via an adaptive compensating unit including a high-pass filter, an absolute value detecting circuit, a low-pass filter and a gain calculating unit.
A carrier signal included in the output voltage of the inverter is detected, a gain corresponding to the magnitude of this carrier component is calculated, and then the gain is fed back to the proportional element. As a result, the gain of the output signal from the proportional element becomes variable,
With this output signal, the control signal for controlling the PWM inverter can be switched to a gain adapted to the load mode. That is, the carrier component which has been unnecessary so far is positively utilized.

[0005]

The equivalent circuit in the discharge mode of the AC filter 11 when the rectifier load 16 is connected and the capacitance C _r of the rectifier filter of the rectifier load 16 in the discharge mode is shown in FIG. 3 (a), and the equivalent circuit in the charge mode is shown in FIG. 3 (b). As shown in. From the above equivalent circuit, the natural angular frequency ω _n of the discharge mode and the natural angular frequency ω _nch of the charge mode can be expressed by the following equations.

[0006]

[Equation 1]

Here, L is the inductance of the AC filter, C is the capacitance of the AC filter, C _r is the capacitance of the rectifying filter, and C _r >> C. Therefore, as is clear from the equations (1) and (2),
the ω _n »ω _nch. As is clear from the gain characteristic curve of the Bode diagram shown in FIG. 6, the response in the charging mode is slow, and the distortion factor of the voltage waveform is deteriorated as shown in FIG. In order to improve this distortion, the gain in the charge mode must be increased to increase the response speed, but if the gain is fixed, the gain in the discharge mode also rises and the gain in the high frequency range is increased. Since it becomes large, it loses stability. Now, as shown in FIG. 7, by maintaining a large gain in the charging mode and a small gain in the discharging mode, it is possible to reduce the stable control characteristic and the distortion factor of the voltage waveform. In order to switch the gain corresponding to the above-mentioned two modes, it is necessary to detect the discharge mode and the charge mode. As is clear from FIG. 5, since the magnitude δ _v of the carrier component of the output voltage is large in the discharge mode and small in the charge mode, two modes can be detected by detecting this δ _v . When the carrier angular frequency is ω _{ca r} and the amplitude of the carrier component is δ _v , it can be expressed by the following equation. δ _v ≈ (ω _n / ω _car ) ² (3) Therefore, as shown in FIG.
The filter provided at 0 detects δ _v , calculates the gain according to the magnitude thereof in the gain calculation unit 24, and feeds it back to the proportional element 2 to make the gain of the output signal variable.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a PWM inverter having a variable gain adaptive control function according to the present invention. In FIG. 1, the output voltage V of the PWM inverter 7 is fed back from the output side of the AC filter 11 including the inductance 9 and the capacitance 10, and is added to the reference signal in the adder 1. The output signal of the adder 1 is input to the stabilization compensator 3 via the proportional element 2, and this output signal is added in the adder 4 together with the reference signal u input via the feedforward path 8, and , And the triangular carrier signal is compared in the comparator 6. The output signal of this comparator 6 is PW
It serves as a control signal for controlling the M inverter 7.

A rectifier load 16 to which the PWM inverter 7 supplies its output is composed of a rectifying circuit 13, a load resistor 15, and a capacitance 14 of a rectifying filter.
The capacitance C _r of the capacitance 14 of this rectifying filter is A
It is considerably larger than the capacitance C of the capacitance 10 of the C filter 11.

P on the output side of the AC filter 11
The output voltage V of the WM inverter 7 is fed back and input to the adder 1, and the high pass filter 2
1, an absolute value detection circuit 22, a low-pass filter 23, and a gain calculator 24.

The carrier component contained in the output voltage V of the PWM inverter 7 is detected by the filter in the adaptive compensator 20 and input to the gain calculator 24 as δ _v . When δ _v is large, it means discharge mode, and δ _v
When is small, it means that the charging mode is set. Therefore, the gain calculation unit 24 calculates a gain according to the size, feeds this gain back to the proportional element 2, and makes the gain variable. FIG. 7 is a gain characteristic curve of the Bode diagram when compensation is performed by the variable gain. By maintaining a large gain in the discharge mode and a small gain in the discharge mode, stability is maintained. It is possible to improve the distortion factor of the output voltage waveform when the rectifier is loaded. 8 and 9
Shows the effectiveness of the present invention confirmed by simulation. FIG. 8 shows the case of variable gain, and FIG.
Shows the case of fixed gain, and it is understood that the distortion ratio of the output voltage is better in the case of variable gain. In FIG. 8, K _min = 2 and K _max = 20, and the gain changes from the discharge mode (K _min = 2) to the charge mode (K _max = 2).
You can see that it has been switched to 0).

[0012]

As described above, the PWM inverter having the variable gain adaptive control function according to the present invention is
In a momentary control system of the output voltage of a PWM inverter equipped with a proportional element, a stabilization compensator, a comparator, an output voltage feedback circuit, etc., a carrier component included in the output voltage of the PWM inverter is detected, and the magnitude of this detection signal is detected. The gain of the output signal of the proportional element is made variable by calculating the gain corresponding to this and feeding it back to the proportional element. That is, the load mode is detected by using the carrier wave component which has been unnecessary so far, and the gain corresponding to the amplitude of the carrier wave component is calculated and fed back, without deteriorating the stability when the rectifier is loaded. The distortion factor of the output voltage waveform can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment according to the present invention.

FIG. 2 is a block diagram of an instantaneous control system of a PWM inverter according to the related art.

FIG. 3 is an equivalent circuit diagram of a discharge mode and a charge mode.

FIG. 4 is a waveform diagram of an output voltage when a rectifier is loaded.

FIG. 5 is a waveform diagram of a carrier signal.

FIG. 6 is a gain characteristic curve of a Bode diagram of fixed gain compensation.

FIG. 7 is a gain characteristic curve of a Bode diagram for variable gain compensation.

FIG. 8 is a simulation during variable gain compensation.

FIG. 9 is a simulation during fixed gain compensation.

[Explanation of symbols]

 1, 4 Adder 2 Proportional element 3 Stabilization compensator 6 Comparator 7 PWM inverter 11 AC filter 16 Rectifier 20 Adaptive compensation unit 21 High-pass filter 22 Absolute value detection circuit 23 Low-pass filter 24 Gain calculation unit

Claims (1)

[Claims] 1. A voltage signal detected from an output circuit of a PWM inverter is fed back and added to a reference signal,
The addition signal is input to the stabilization compensator via a proportional element, the output signal of the stabilization compensator is added to the reference signal supplied via the feedforward path, and the addition signal and carrier wave are added. In the instantaneous control system of the output voltage of the PWM inverter, which controls the signal in the comparator and controls the PWM inverter by the detection signal of the comparator, the carrier wave component included in the output voltage of the PWM inverter is detected to obtain the detected value. The corresponding gain is calculated, the calculated gain is fed back to the comparison element to adjust the gain of the output signal, and the PWM is adjusted by the output signal from the proportional element via the stabilization compensator and the comparator. The gain of the control signal that controls the inverter is adjusted to suit the load mode. A PWM inverter having a variable gain adaptive control function, characterized in that the output voltage of the PWM inverter is instantaneously controlled by.