JP3405076B2 - PWM converter device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PWM converter device for converting power between AC and DC.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a circuit configuration of a conventional PWM converter described in, for example, Japanese Patent Publication No. 63-1831. In the figure, 1 is a voltage type PWM converter using a gate turn-off thyristor (hereinafter referred to as GTO) which is a self-extinguishing element, 2 is a capacitor for smoothing the output voltage of the converter 1, 3 is a load device such as a PWM inverter. 4 is an AC reactor as a reactance component.

Reference numeral 5 is a voltage command circuit for outputting a command signal of the DC output voltage of the converter 1, 6 is voltage detection means for detecting the voltage of the capacitor 2, and 7 is a voltage for abutting and amplifying the voltage command signal and the voltage detection signal. A deviation amplifier 8 is a transformer (hereinafter referred to as power supply voltage detection means) for isolating and extracting the voltage of the AC power supply connected to the converter 1, and a signal having the same phase as each phase voltage of the AC power supply and each transformer. A total of 6 signals, that is, a signal having the same phase as the phase voltage and a signal having a 90 ° phase difference with respect to each phase voltage, are output.

Reference numeral 9 is a current detecting means for detecting an AC input current (instantaneous value) of the converter 1, and 10 is an arithmetic circuit for outputting a command signal 15 of a fundamental wave component (instantaneous value) of the AC input voltage of the converter 1. is there. Reference numeral 11 is an oscillator that generates a triangular wave carrier signal 16, 12 is a comparator that compares the carrier signal 16 and the output signal 15 of the arithmetic circuit 10, and outputs a pulse width modulation signal,
Reference numeral 13 is a gate amplifier that outputs a gate signal for controlling ON / OFF of the GTO of the converter 1, and reference numeral 14 is an overvoltage detector that generates a signal when the voltage of the capacitor 2 is a predetermined value or more.

FIG. 5 is a diagram showing waveforms of various signals of the apparatus of FIG. Next, the operation of the apparatus shown in FIG. 4 will be described with reference to FIG. First, the operation of the converter 1 will be described.
(A) shows the output signal 15 of the arithmetic circuit 10 and the output signal 16 of the oscillator 11. The two signals are compared in the comparator 12, and as shown in (b) according to the magnitude relation. A signal whose pulse width is modulated (hereinafter referred to as a PWM signal) is obtained. G that constitutes the R phase of the converter 1
A gate signal is supplied to the TO element (Trp, Trn) according to the PWM signal. T if the PWM signal is positive
A gate signal is applied so that rp can be turned on and Trn can be turned off, and conversely, if negative, Trn can be turned on and Trp can be turned off.

As a result, the AC input terminal (R phase) of the converter 1
When the neutral point potential of the DC circuit (potential at the point O shown in FIG. 4) is zero, the potential of changes in the same manner as the PWM signal of FIG. 5B. By the way, in the same waveform, the output signal 15 of the arithmetic circuit 10 includes a fundamental wave component of the same phase as shown by a broken line in the figure, and its magnitude is proportional to the output signal. And
Since similar control is performed for the other S-phase and T-phase as well, regarding the fundamental wave component, voltages different in phase by 120 degrees are generated at the AC input terminal of the converter 1.

On the other hand, the sine wave shown in FIG. 5 (c) represents the AC power supply current IR (R phase), the current is in phase with the AC input voltage of the converter 1, and the power supply power factor is approximately 1. In the state of 0,
The case where the converter 1 is performing the forward conversion operation is shown. In order for the power source power factor to be exactly 1.0, the current must be in a phase ahead of the AC input voltage due to the voltage drop in the reactor 4, but for simplicity, the current and the AC input voltage are in phase. The case is illustrated.

The power supply current IR flows to the DC circuit through Drp or Trn for the positive half-wave and Trp or Drn for the negative half-wave.
Since the off state is controlled, the direct current Id flowing from the converter 1 to the P side of the direct current circuit is as shown in FIG.
Similarly, the DC current Id flowing into the converter 1 from the N side of the DC circuit is as shown in FIG. 5 (e). That is, on the P side of the DC circuit, on the average, Id flows from the converter 1 to the capacitor 2, and on the N side, the Id flows from the capacitor 2 to the converter 1.
Flow toward.

Note that Id is as shown in FIG.
Although it pulsates as shown in (e), since the actual Id is the sum of the three phases R to T, the amount of pulsation is considerably reduced as compared with only one phase. As is clear from FIG. 5, the magnitude of the DC current is the power supply current (a component in phase with the AC power supply voltage).
Proportional to the size of. Therefore, the magnitude of the direct current can be controlled by controlling the magnitude of the power supply current.

FIG. 6 is a vector diagram showing the relationship between the AC power supply voltage E0, the AC input voltage Et of the converter 1 and the power supply current I. The figure shows the case where ψ = 0 and the power source power factor is 1.0. Because of the reactor 4, the voltage of Et drops by xI from E0, so that Et moves on the broken line in the figure according to the magnitude of I under the condition of ψ = 0. In other words, if the magnitude and phase of Et are controlled so that Et moves on the broken line,
The magnitude and direction of the current I (in-phase component with E0) can be controlled while maintaining ψ = 0.

The AC input voltage Et of the converter 1 is controlled according to the output signal of the arithmetic circuit 10 as described above, and its operation will be described below. In the voltage deviation amplifier 7, the DC voltage command and the DC voltage detection signal are matched with each other, and a signal proportional to the deviation is taken out. In the arithmetic circuit 10, with the signal of the power supply voltage detecting means 8 as a reference, a signal in-phase with the power supply voltage having a predetermined amplitude (sine wave signal).
Also, a signal having a phase difference of 90 degrees with this is created, and by adding them, an Et command signal is created. Here, the amplitude and polarity of the former signal change in proportion to the constant value proportional to E0 in the steady state, and the latter signal in proportion to the output signal of the voltage deviation amplifier 7 in the steady state. This relationship is similar to the vector diagram of FIG.

As described above, the AC input voltage E of the converter 1 is
Since t is controlled, the power supply current I is controlled so as to be proportional to the output signal of the voltage deviation amplifier 7, and the direct current is controlled in the same manner. At this time, the operation of the voltage deviation amplifier 7 is controlled so that the DC output current increases when the DC voltage is insufficient and decreases when the DC voltage is insufficient, so that the DC voltage can be maintained at the command value. .

As described above, it operates normally, but if a failure occurs in the control circuit or the like, the DC output voltage may become abnormally high due to the operating principle of this converter.
This is for the following reason. As described above, the power supply current I is E0
And Et, and the DC output current Id flows in proportion to the component perpendicular to E0 of the difference voltage. When the DC voltage rises due to the increase of the DC current, Et rises, but the difference between E0 and Et becomes small and the current becomes zero.
There is no so-called equilibrium. This will be described below.

FIG. 7 is a diagram showing the relationship between DC current and DC voltage. In the figure, initially Et is Et1 and I is I1. At this time, the DC output current Id changes to the load device 3
If the DC voltage rises due to the increase in the charge-up of the capacitor 2 due to the larger current than that required by Et, Et rises as Et2 unless there is a change in the operation of the control circuit. Then, the difference between E0 and Et is further increased from xI1 to xI2, and proportionally increases from I1 to I2.
At this time, the in-phase component of E of I also increases, so that the DC current Id increases and the DC voltage increases at an accelerating rate.

As described above, in the PWM converter, the DC voltage may become excessive at the time of failure, and the following method is used to prevent the overvoltage. When the DC voltage is equal to or higher than the predetermined value, the overvoltage detector 14 outputs a signal. Then, from the gate amplifier 13, the GTO of the converter 1 is all turned off accordingly.
A gate signal for turning off is supplied. As a result, the converter 1 becomes equivalent to a diode converter and the subsequent overcharging of the capacitor 2 is prevented. That is, overvoltage is prevented. Note that the output signal of the overvoltage detector is held by a flip-flop circuit or the like. Meanwhile converter
For final protection, open the breaker on the AC input side of 1.

[0016]

The conventional method for protecting the PWM converter device is as described above, and there is a phenomenon in which the DC voltage rises due to the circuit principle when the circuit, which should originally control the DC voltage to be constant, fails. It detects that the voltage has risen to a predetermined value, and the predetermined value is fixed as, for example, the overvoltage protection level of the element. Therefore, when the power supply voltage is low, if a failure occurs in the control circuit, the operation is continued until it reaches a predetermined value despite the failure of the circuit, so that a circuit abnormality can be notified to the outside early. There was a problem that I could not do it.

Further, even if the circuit fails, it can be detected only by the rise of the voltage, so that if the DC voltage is controlled to be lower than the command value, it cannot be detected. was there.

The present invention has been made to solve the above-mentioned problems. When an abnormality occurs in the control circuit regardless of the power supply voltage, the abnormality is promptly detected and the output is stopped, and only the voltage rises. It is an object of the present invention to obtain a PWM converter device that can detect a voltage drop abnormality.

[0019]

A PWM converter device according to the present invention has a diode bridge in which a self-extinguishing element is connected in antiparallel with each diode, and the self-extinction element is pulse-width modulated. In a PWM converter device that controls and converts power between AC and DC, a DC voltage conversion unit that converts a detection voltage from a power supply voltage detection unit for detecting a power supply voltage into a DC voltage, and a converted DC voltage value DC voltage command calculation means for adding a predetermined value to create a DC output voltage command value, and the difference between the DC output voltage command value and the detected voltage from the DC output voltage detection means
Calculated, an error voltage computing means for outputting an error voltage,
An error voltage excess detection means for inputting an error voltage output from the error voltage calculation means and determining an error voltage excess for making the self-extinguishing element non-conductive when the error voltage is a predetermined value or more. Is.

The error voltage excess detecting means is adapted to detect the error voltage from the error voltage calculating means as an absolute value.

Further, a PWM converter is provided which has a diode bridge in which a self-extinguishing element is connected in antiparallel with each diode, and the self-extinguishing element is subjected to pulse width modulation control to convert power between AC and DC. In the device, a DC voltage converting means for converting the detected voltage from the power supply voltage detecting means for detecting the power supply voltage into a DC voltage, and a predetermined value is added to the converted DC voltage value to create a DC output voltage command value. a DC voltage command calculation means, the difference between the DC output voltage command value and the detected voltage from the DC output voltage detecting means
Calculated, an error voltage computing means for outputting an error voltage,
A first PI calculation means for inputting the error voltage output from the error voltage calculation means to perform PI calculation, a phase detection means for detecting the power supply phase by inputting the output from the power supply voltage detection means, and this phase detection. A sine wave generating means for outputting a reference sine wave of the same phase to each phase voltage by the output from the means;
The output of the PI calculation means and the output from the sine wave generation means are input, the multiplication means for calculating the current command value, the power supply current detection means for detecting the power supply current, and the power supply current detection means are used for detection. A deviation calculating means for matching the power supply current and the output of the multiplying means to calculate the deviation, and a second PI calculating means for calculating the PI of the output of the deviation calculating means are provided.

Furthermore, a first-order lag filter for applying a first-order lag filter to the DC output voltage command value created by the DC voltage command calculation means is provided.

[0023]

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1. FIG. 1 shows an example of a PWM converter that is an embodiment of the present invention. 2 to
Reference numerals 4, 6, 8 and 9 are the same as those in the above-mentioned conventional example shown in FIG.

1a is a voltage type PWM using an IGBT element
A converter, 20 is a DC voltage conversion means, 21 is a DC voltage command calculation means, 22 is a first-order lag filter, and 23 is a second PI.
Calculating means, 24 is multiplying means, 25 is phase detecting means for detecting the power source phase, 26 is sine wave generating means for outputting a reference sine wave of the same phase for each phase voltage, and 27 is when the value of the error voltage becomes excessive. Error voltage excess detection means for generating a signal, 28 is first PI calculation means, 30 is deviation calculation means, and 31 is error voltage calculation means.

Here, the DC voltage conversion means 20 inputs the power supply voltage detected by the power supply voltage detection means 8 and applies a predetermined coefficient (for example, 1.4) to convert the AC power supply voltage into a DC voltage. The DC voltage command calculation means 21 inputs this DC voltage conversion value and adds a predetermined value to create a DC voltage command value. Therefore, the DC voltage command value can be calculated by the following formula. DC voltage command value = AC power supply voltage x predetermined coefficient
+ Predetermined value

The first-order lag filter 22 receives the DC voltage command value output from the DC voltage command calculator 21 and applies the first-order lag filter to make a sudden change in the power supply voltage (for example, a momentary drop or rise in the power supply voltage). ), So that the DC voltage command value is not affected.

The error voltage calculation means 31 matches the DC voltage command value output from the first-order lag filter 22 with the DC output voltage detected by the DC voltage detection means 6, and calculates the error voltage by the following equation (1). . Error voltage = DC voltage command value-DC output voltage (1)

The first PI calculation means 28 performs PI calculation on the error voltage output from the error voltage calculation means 31 and outputs it to the multiplication means 24. On the other hand, the sine wave generation means 26 inputs the power supply phase detected from the power supply voltage detected by the power supply voltage detection means 8 by the phase detection means 25, and outputs the reference sine wave of the same phase to each phase voltage to the multiplication means 24. The multiplication means 24
The current command value is calculated by the following equation (2). Current command value = error voltage x sine wave generation circuit output (2)

The deviation calculating means 30 calculates the current command value and
The output of the current detection means 9 for detecting the AC input current of the converter 1a is matched and the deviation thereof is calculated. Second PI
The calculation means 23 performs a PI calculation on the deviation and outputs it to the comparator 12. The following control is performed so that the AC input current flows in the state where the power source power factor is approximately 1.0 as in the conventional example.

Since the current minor loop is included in the DC voltage constant control by the current control based on the above current command value, the DC voltage can be controlled by controlling the magnitude of the power supply current with respect to load fluctuations and the like. Can be controlled more stably and constantly.

Next, the protection method will be described. The error voltage output from the error voltage calculation unit 31 is input to the error voltage excess detection unit 27, and the error voltage excess is detected when the error voltage is a predetermined value or more. When an excessive error voltage is detected, an abnormal signal is output to the gate amplifier circuit 13 and the self-extinguishing element is made non-conductive, so that the excessive phenomenon of the DC output voltage due to the failure of the PWM control circuit or the like can be prevented. .

FIG. 2 is a diagram showing the relationship of error voltage with respect to load fluctuation. The relationship between the error voltage and the load fluctuation will be described below. During normal operation, the DC output voltage is controlled so as to match the DC voltage command value, so that the error voltage becomes 0 steadily. Here, considering the case where the load 3 fluctuates, for example, from 0% load to power running 10
Although the DC output voltage transiently rises when the voltage rises stepwise to 0%, the error voltage rises once and converges to 0 because it coincides with the DC voltage command value by the DC voltage constant control. Similarly, when the load changes to 100% regeneration,
The error voltage rises to the negative side and converges to zero.

Here, if a failure occurs in the control circuit and, for example, the DC output voltage becomes zero, from the equation (1), the error voltage = DC voltage command value, the error voltage exceeds a predetermined value, and it becomes plus excessive. Become.
On the contrary, when the DC voltage command value becomes zero, the error voltage becomes equal to −DC output voltage according to the equation (1), and the error voltage exceeds the predetermined negative value and becomes minus too large. Therefore, in any case, the error voltage excess detection means 27 outputs an abnormal signal to the gate amplifier 13 and makes the self-extinguishing element non-conductive, so that the PWM converter device can be protected.

As described above, as the possibility that the control circuit may fail, the error voltage is considered to be both excessive and excessive. Therefore, the excessive error voltage detecting means 27 detects the error voltage as an absolute value. Regardless of the polarity, PW can be achieved by quickly turning off the self-extinguishing element.
The M converter device can be protected.

FIG. 3 is a diagram showing the operating characteristics of the error voltage excessive protection against the power supply fluctuation. In the figure, the overvoltage protection level of the element corresponds to a predetermined value as a reference value for determining the DC output voltage as excessive in the conventional protection method. On the other hand, in the present invention, the deviation between the power supply voltage and the DC output voltage is always detected and compared, and the control circuit is provided with a value outside the range of the predetermined value ΔV on the basis of the value obtained by converting the fluctuating AC power supply voltage into DC. It is determined that an abnormality has occurred, and the self-extinguishing element is made non-conductive to protect the PWM converter device.

By the way, in the above description, the converter 1a has an IG
Although the example using the BT element is shown, the same effect can be obtained by using a transistor or a general thyristor.

In the above description, the example in which the current detecting means 9 is provided for three phases is shown, but the current detecting means 9 is provided for two phases,
The same effect can be obtained by calculating the other one phase.

[0038]

Since the present invention is constituted as described above, it has the following effects.

In a PWM converter device having a diode bridge in which a self-extinguishing element is connected in anti-parallel with each diode, and controlling the pulse width modulation of the self-extinguishing element to perform power conversion between AC and DC. DC voltage converting means for converting the detected voltage from the power supply voltage detecting means for detecting the power supply voltage into a DC voltage, and a DC voltage for adding a predetermined value to the converted DC voltage value to create a DC output voltage command value and command calculating means calculates a difference between the DC output voltage command value and the detected voltage from the DC output voltage detecting means, and an error voltage computing means for outputting an error voltage, the error voltage output from the error voltage calculation means When the input voltage exceeds the predetermined value, the error voltage excess detection means for determining the error voltage excess for making the self-extinguishing element non-conducting is provided. Can control the DC output voltage while maintaining a constant relationship, the operation of the PWM converter, a stable control can be realized without being affected by fluctuations in the power supply voltage.

Since the error voltage excess detection means detects the error voltage from the error voltage calculation means as an absolute value, it is not affected by the disturbance of the power supply system, and at the same time, the DC voltage constant control is Even if the DC output voltage rises or falls due to a failure of the PWM control circuit or the like, it is possible to protect it by detecting an abnormal operation and turning off the self-extinguishing element.

Further, a PWM converter is provided which has a diode bridge in which a self-extinguishing element is connected in anti-parallel with each diode, and the self-extinguishing element is subjected to pulse width modulation control to perform power conversion between AC and DC. In the device, a DC voltage converting means for converting the detected voltage from the power supply voltage detecting means for detecting the power supply voltage into a DC voltage, and a predetermined value is added to the converted DC voltage value to create a DC output voltage command value. a DC voltage command calculation means, the difference between the DC output voltage command value and the detected voltage from the DC output voltage detecting means
Calculated, an error voltage computing means for outputting an error voltage,
A first PI calculation means for inputting the error voltage output from the error voltage calculation means to perform PI calculation, a phase detection means for detecting the power supply phase by inputting the output from the power supply voltage detection means, and this phase detection. A sine wave generating means for outputting a reference sine wave of the same phase to each phase voltage by the output from the means;
The output of the PI calculation means and the output from the sine wave generation means are input, the multiplication means for calculating the current command value, the power supply current detection means for detecting the power supply current, and the power supply current detection means are used for detection. Since the deviation calculating means for calculating the deviation by comparing the power supply current with the output of the multiplying means and the second PI calculating means for calculating the PI of the output of this deviation calculating means are provided, it is possible to provide a constant DC voltage control loop. Since it has a current minor loop, by controlling the magnitude of the power supply current with respect to load fluctuations and the like, the DC voltage can be controlled more stably and constantly.

Furthermore, since a first-order lag filter for applying a first-order lag filter to the DC output voltage command value created by the DC voltage command calculation means is provided, a sudden change in the power supply voltage causes
Since it is possible to prevent the DC voltage command value from being affected, it is possible to secure robustness of control due to disturbance of the power supply system.

[Brief description of drawings]

FIG. 1 is an example of a PWM converter that is an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship of error voltage with respect to load fluctuation.

FIG. 3 is a diagram showing operating characteristics of error voltage excess protection against power supply fluctuations.

FIG. 4 is a diagram showing a circuit configuration of a conventional PWM converter.

5 is a diagram showing waveforms of various signals of the apparatus of FIG.

FIG. 6 is a vector diagram showing a relationship between an AC power supply voltage E0, an AC input voltage Et of the converter 1 and a power supply current I.

FIG. 7 is a diagram showing a relationship between a DC current and a DC voltage.

[Explanation of symbols]

1, 1a converter, 2 smoothing capacitor, 3 load, 4 AC reactor, 5 voltage command circuit, 6
DC voltage detector, 7 voltage deviation amplifier, 8 power supply voltage detecting means, 9 current detecting means, 10 arithmetic circuit,
11 Oscillator for generating triangular wave carrier signal, 12
Comparator, 13 gate amplifier, 14 overvoltage detector,
20 DC voltage conversion means, 21 DC voltage command calculation means, 22 first-order lag filter, 23 second PI calculation means, 24 multiplication means, 25 phase detection means, 2
6 sine wave generation means, 27 error voltage excess detection means,
28 first PI calculating means, 30 deviation calculating means,
31 Error voltage calculation means.

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Claims (4)

(57) [Claims] 1. A PWM converter having a diode bridge in which a self-extinguishing element is connected in antiparallel with each diode, and the self-extinguishing element is subjected to pulse width modulation control to perform power conversion between AC and DC. In the device, a power supply voltage detecting means for detecting the power supply voltage, a direct current voltage converting means for converting the detected voltage from the power supply voltage detecting means into a direct current voltage, and a direct current by adding a predetermined value to the converted direct current voltage value. DC voltage command calculation means for creating an output voltage command value, DC output voltage detection means for detecting a DC output voltage, and a difference between the DC output voltage command value and the detected voltage from the DC output voltage detection means. , to an error voltage computing means for outputting an error voltage, and inputs the error voltage output from the error voltage calculation means, when the predetermined value or more, the self-turn-off devices non-conductive PWM converter apparatus having an error voltage excessive detecting means, the determining the error voltage excess for. 2. The PWM converter device according to claim 1, wherein the error voltage excess detection means detects the error voltage from the error voltage calculation means as an absolute value. 3. A PWM converter having a diode bridge in which a self-extinguishing element is connected in anti-parallel with each diode, and the self-extinguishing element is subjected to pulse width modulation control to perform power conversion between AC and DC. In the device, a power supply voltage detecting means for detecting the power supply voltage, a direct current voltage converting means for converting the detected voltage from the power supply voltage detecting means into a direct current voltage, and a direct current by adding a predetermined value to the converted direct current voltage value. DC voltage command calculation means for creating an output voltage command value,
A DC output voltage detecting means for detecting a DC output voltage, an error voltage calculating means for calculating a difference between the DC output voltage command value and a detection voltage from the DC output voltage detecting means, and outputting the error voltage as an error voltage, and this error First PI calculation means for inputting an error voltage output from the voltage calculation means and performing PI calculation, phase detection means for detecting the power supply phase by inputting the output from the power supply voltage detection means, and this phase detection means The sine wave generating means for outputting the reference sine wave of the same phase to each phase voltage, the output of the first PI calculating means and the output from the sine wave generating means are input by the output from the above, and the current command value is calculated. Multiplier means, power supply current detection means for detecting the power supply current, deviation calculation means for matching the power supply current detected by the power supply current detection means with the output of the multiplication means, and calculating the deviation, and the deviation calculation means. Second for PI computing an output of the arithmetic means
A PI converter, and a PWM converter device. 4. The PWM according to claim 1, further comprising a first-order lag filter that applies a first-order lag filter to the DC output voltage command value created by the DC voltage command calculation means. Converter device.