JPH04193071A - Method of detecting reference phase of regenerative inverter - Google Patents

Abstract

PURPOSE:To prevent the malfunction by the power source distortion of a phase detector by simple system constitution and operation method by providing a means, which detects the reference phase, with a timer, which follows the cycle of the power source, and controlling the phase of a regenerative inverter by the estimated power source cycle that the timer holds. CONSTITUTION:The reference phase that the reference phase detection circuit 7 detects is a power source phase zero cross signal, and the edge of zero cross exists three times between 0 and 2pi. Out of them, the two times in last transition are checked, and the section between them is made to correspond to sin table 11, and is made AC power source voltage detection signal. It is made to output the estimated reference phase by a timer besides the phase zero cross detection signal as the AC power source voltage detection signal. That is, though the power source reference phase is usually detected from the output voltage of a regenerative inverter 2, when instantaneous power stoppage or open phase occurs or in case that it loses the basic power source phase, the estimated reference phase by the timer is adopted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reference phase detection method for a regenerative inverter.
In particular, the present invention relates to a method of accurately determining the power supply phase in order to regenerate power to the power supply with a high power factor in a regenerative inverter.

[Prior Art] Conventional devices that regenerate electric power into a power source require phase detection by a special device and interrupt control by a highly accurate and fast-responsive processor in order to synchronize the phase of the regenerated electric power with the phase of the power source. I needed it.

More specifically, only the inspection signal at the time when the power supply phase crosses the zero point is used as the reference phase. This method requires the use of a special detector that responds instantaneously to sudden phase changes, and the processing circuit for the post-detection signal must also be an expensive circuit that responds quickly.

Furthermore, when a momentary power outage or an open phase occurs on the power supply side, the power supply phase that the regenerative inverter uses as a reference is lost, which affects the voltage waveform of the regenerative power. At this time, the regenerative inverter is controlled so as not to suppress its output. However, in this state, a self-excitation phenomenon occurs in which the device is operated by its own voltage, resulting in a runaway state and the detected voltage increasing automatically.

When the open phase is recovered, a large voltage difference will occur between the regenerative inverter output voltage and the recovered power supply voltage, and a correspondingly large amount of current will flow.

As a countermeasure, it may be possible to set the voltage of the phase detector to the primary voltage of the regenerative transformer instead of the output voltage of the regenerative inverter, but with this method, the phase difference of the power supply becomes large and the The constant power factor deteriorates.

In order to solve these problems, we have proposed a method in which the synchronous pull-in period is sufficiently long so that the voltage is pulled in after the voltage is attenuated and there is no voltage rise due to the self-excitation phenomenon of the regenerative inverter. A method has been proposed in which a delay element consisting of a so-called RC circuit consisting of a resistor and a capacitor is inserted for the purpose of removing ripples to prevent malfunction.

[Problem to be solved by the invention] However, in order to prevent excessive current from flowing when the power supply returns from a momentary power outage, the synchronous pull-in period is sufficiently long to prevent the voltage rise due to the self-excitation phenomenon of the regenerative inverter. If the system is pulled in from a state where the voltage is attenuated and there is no voltage, it takes too long to restart after power is restored, and some systems may become unusable. In this respect, there is a strong demand for faster synchronous pull-in.

In addition, in the method of inserting a delay element consisting of an RC circuit for the purpose of removing ripples so that the phase detector does not malfunction due to power supply distortion, in order to correct the difference between this delay and the true value, the next stage is This resulted in the adoption of a complex system configuration, which posed problems in terms of reliability.

The purpose of the present invention is to provide a reference phase for a regenerative inverter that prevents malfunctions caused by power supply distortion in a phase detector with a simple system configuration and operation method, and speeds up synchronization after power is restored from a momentary power outage. An object of the present invention is to provide a detection method.

[Means to solve the problem]

In order to achieve the above object, the present invention detects the phase of the output voltage of a regenerative inverter, multiplies the DC voltage command to the DC main circuit and the phase detection value to generate an AC phase voltage command, and outputs each AC phase. In a reference phase detection method for a regenerative inverter for synchronizing the phase of the output voltage of a regenerative inverter with the phase of a power supply using a current command of The present invention proposes a reference phase detection method for a regenerative inverter that controls the phase of the regenerative inverter based on the expected power cycle held by a timer to perform regeneration when recovering from a momentary power outage or phase loss.

The means for detecting the reference phase is also provided with means for comparing the phase detection value with the power supply specification cycle, and when the power supply phase detection value is close to the previous value + l/f seconds (where f is the power supply specification frequency), It is also possible to make the timer track the phase detection value, and set the timer to the power supply specification value if the phase detection value is far away.

Furthermore, a counter is provided to evaluate the power cycle detected by the phase detection value, and the power supply phase detection value is set to the previous value + l/'f.
If the cumulative value of the evaluation count exceeds a predetermined value, regeneration is performed based on the power supply phase detection signal, and the cumulative value of the evaluation count is a predetermined value. In the following cases, it is also possible to perform regeneration according to the expected power supply cycle based on the phase detection signal held by the timer of the phase detection circuit.

In this case, if the cumulative value of the evaluation count falls below a predetermined value that is lower than the predetermined value, the regenerative inverter is stopped.

In any of the above cases, it is possible to provide a plurality of evaluation counters for each predetermined deviation from the power supply specification cycle, and when the phase is outside the correction range, regeneration occurs at the power supply cycle in which the cumulative value of the evaluation counter is the maximum. .

[Operation] An outline of the reference phase detection method according to the present invention for realizing a regenerative inverter with a high power factor will be explained.

The regenerative inverter multiplies the DC voltage command that keeps the DC main circuit voltage constant by the phase detection value that converts this DC voltage command into an instantaneous AC value to create an AC phase voltage command.
It has a three-phase current control system for each phase.

At the start of the regenerative inverter, a function is required to match the phase of the inverter output voltage with the phase of the power supply voltage. The reference phase for creating these phase voltage commands and the reference phase for power supply voltage bias control require highly accurate synchronization of the power supply phases.

The present invention has this phase matching function separately from the current control system, and prevents overcurrent when starting the regenerative inverter and when recovering from a momentary power outage. That is,
Even if the reference power supply phase is lost due to a momentary power outage or phase loss, by updating the power cycle evaluation counter and holding the reference phase by the current timer, highly accurate synchronization is achieved when power is restored, and power supply voltage bias control is activated. Therefore, the voltage difference between the inverter output voltage and the power supply voltage becomes extremely small.
The regenerative inverter can be restarted without passing excessive current.

In order to achieve high-speed draw-in when power is restored from a momentary power outage, it is necessary to quickly synchronize the phase of the regenerated power with the power supply phase at the time of power restoration. Conventional phase detectors use the output voltage of the regenerative inverter itself as the voltage to be detected, resulting in a voltage difference between the output voltage and the phase of the power supply voltage.

In contrast, in the present invention, the phase zero detection circuit and
It includes a counter that detects the phase difference between the detected value and the previous detected value and evaluates the accuracy of the power supply cycle, and a timer.
The system predicts the power cycle from a momentary power outage to the time of power restoration, maintains the predicted power cycle with the highest probability, and waits for the power to return from a momentary power outage, allowing the regenerative inverter to restart smoothly.

That is, the phase detector of the present invention detects the phase from the output voltage of the regenerative inverter. When a momentary power outage or phase loss occurs and the reference power supply phase is lost, in the present invention, the evaluation counter value continues to be updated to -, and the edge phase of the power supply phase detection and the phase determined by the current timer are outside the correction range. In this case, the reference phase is switched based on the cumulative value of the evaluation counter, and becomes the reference phase determined by a timer that is not related to the output voltage of the regenerative inverter. Since the elapsed time is updated using this reference phase even during a momentary power outage, it becomes possible to synchronize with the power supply phase when the power is restored, realizing faster synchronization pull-in.

In the present invention, the power supply phase is detected at a constant sampling period, and the recognition of zero power supply phase detection is delayed, but the accuracy of the expected period is high and there is no problem with one-phase correction. Therefore, there is no need to perform synchronization using special interrupts.

〔Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the system configuration of an embodiment of a regenerative inverter that employs a reference phase detection method for a regenerative inverter according to the present invention.

The power from the DC rectifier power supply 1 is transferred to the DC main circuit capacitor 3.
It is supplied to a regenerative inverter 2 whose main circuit is, for example, a transistor. Regenerative power from the regenerative inverter 2 is regenerated to a power source (not shown) via a regenerative power transformer 6. Of the regenerative power from the regenerative inverter 2, current is detected by a current detector 4, while voltage is detected by a voltage transformer 5.

The voltage detected by the voltage transformer 5 is taken into a U-phase quasi-phase detection circuit 7u and a W-phase quasi-phase detection circuit 7w, respectively. Line-to-line correction is applied to the reference phase detected by the U-phase system quasi-phase detection circuit 7u using a phase command 8u. Further, the phase command 90 and the adder 10u correct the phase shift caused by the provision of the control circuit. This correction also applies to the W phase. The corrected reference phases of the U phase and W phase are sent to the sin table 11,
Converted to power supply voltage detection signal. On the other hand, DC voltage command]
The voltage command from 2 is compared with the voltage across the DC main circuit capacitor 3 by the adder 13, and the deviation thereof is input to the automatic voltage regulator 14. Automatic voltage regulator AVR1
4 and the power supply voltage detection signal output from sin table 1 are multiplier 15U.

15w, respectively, to obtain U-phase and W-phase current commands.

The U-phase and W-phase current commands are compared with the detected current of the current detector 4 by adders 20u and 20w, respectively, and the deviation is calculated by the automatic current regulator ACR25u.

It is input to 25w. These automatic current regulators ACR25
The outputs of u and 25w are converted to sir+ by adders 26u and w.
It is added to the current value of table l 1 and input to the pulse width control circuit 27. The pulse width control circuit 27
A WM signal is generated to control the regenerative inverter 2 made up of the above transistor main circuit. Note that the adders 16 and 21 and the inverters 17 and 22 are for creating a -phase signal from a U-phase signal and a W-phase signal. Further, the adder 18, the inverter 19, and the adders 26u, , v, and w are provided to align the phases at the start time.

In the regenerative inverter system shown in FIG. 1 configured in this way, the voltage of the DC main circuit smoothing capacitor 3 is detected,
When the deviation between this and the voltage command value set in the voltage command 12 is added to the automatic voltage regulator AVR14, its output becomes the regenerative current command value of the DC signal. This and the power supply voltage detection signal are multiplied by a multiplier 15 to obtain a sine wave regenerative current command value.

On the other hand, when the current detector 4 detects the alternating current of the regenerative inverter 2 and the deviation between the detected alternating current and the sine wave regenerative current command value is applied to the automatic current regulator ACR25, its output becomes the alternating current voltage of the regenerative inverter. (phase voltage) command value. This is pulse width controlled to obtain a regenerative inverter PWM signal.

With this control, the voltage of the DC main circuit smoothing capacitor follows the command value, and the phase of the power supply current is controlled to match the power supply voltage, so that control with a power factor of 1.0 can be realized.

A power supply voltage bias control output is added to the power supply voltage of the automatic current regulator ACR25, and the output voltage of the regenerative inverter is made to match the power supply voltage when the current control system is restarted from suppressed.

In this embodiment, the reference phase detected by the reference phase inspection circuit 7 is a power supply phase zero cross signal, as shown in FIG. 3, and there are three zero cross edges between O and 2π. Check the falling edge twice, and sin t between them.
An AC power supply voltage detection signal is made to correspond to ABLE.

In this embodiment, as an AC power supply voltage detection signal,
In addition to the above-mentioned phase zero cross detection signal, the expected reference phase by the timer can also be output. In other words, the power supply reference phase is normally detected from the output voltage of the regenerative inverter, but when a momentary power outage or phase loss occurs, or when the reference power supply phase is lost, the predicted reference phase by a timer is used. do.

In the present invention, a timer and a power supply phase evaluation counter are provided in the reference phase detection circuit 7.

FIG. 2 is a diagram illustrating a method for determining a reference phase according to the present invention.

The present invention is based on the fact that when the power supply frequency is, for example, 50 Hz, the electric power company guarantees that the number of peaks in the voltage waveform will always be 50 per second. 50 pieces/
Although the number of peaks per second is guaranteed, there are variations in the pitch of 20 milliseconds (ms). The present invention aims to execute regeneration control in response to this variation accurately.

In a startup state such as when the control power is turned on, the evaluation counter is reset to zero at the rising edge of the power supply voltage detection signal, and the current time is set as the reference time.

When the edge of the first power phase zero cross is detected, the difference between the current time and the first timer value + (1/jl) ms is determined, and the reference time is changed based on that value. Tatami, f
is the power frequency. In eastern Japan, the power frequency f is 50
Hz, 1/f is 20 m s. At the same time, when initialized, a value weighted by 1 or 2 is added to the evaluation counter value of O.

Now, in FIG. 2, the count value 31 of the timer increases almost linearly. The power supply phase calibration signal 32 is a signal that repeats ON and OFF at, for example, a zero-cross point of the power supply voltage waveform. The first time is below the timer value. Then, the current time when the edge of the power phase zero cross for the second and subsequent times is detected is set as the timer value T1. Below the first timer value to find the difference from the first time. These deviations Δt are determined by adding 20 m5 to the value T2.

Δt, =T, -T, =T, +20ms -T.

Since the phase shift is within the allowable range, the second and subsequent current timer values T3 are set as the new reference times. At this time, the existence probability is considered to be high on the state crime distribution curve, so the evaluation counter value is updated with a weight of 2.

Set the quasi-time by △ from the current timer value T1. The value obtained by subtracting /2 is T3-△L. /2. This is a correction method based on the policy of not drastically changing the reference phase. At this time,
The evaluation counter value is updated with a weight of 1.

Below the first timer value without following. The value T1 obtained by adding 20 m5 to the above is set as the new standard time. At this time, the evaluation counter value is updated with a weight of -1.

If the value of the evaluation counter that repeats up and down in this manner exceeds the predetermined value N1, the power supply phase zero detection signal is directly used as the reference phase.

If the value of the evaluation counter is less than the predetermined value N1, it is assumed that there has been an abnormality such as a momentary power outage on the power supply side, and the phase is switched to the internal reference phase by the timer and waits for the power supply to return.

Further, when the evaluation counter value falls below a predetermined value N, the output of the reference phase pulse is stopped and maintenance inspection is awaited.

Note that the number of evaluation counters is not limited to one. For example, it is also possible to divide the deviation of the power supply cycle into several sections, provide an evaluation counter for each division, and adopt the power supply cycle corresponding to the section with the largest count value to set the reference phase of the regenerative inverter.

[Effects of the Invention] According to the present invention, synchronization with the power supply can be reliably achieved even when the power supply phase changes widely, compared to the case where control is performed using only the power supply phase zero detection signal.

The period of synchronous pull-in can be shortened to two cycles.

Even if the phase is lost due to a momentary power outage, etc., the reference phase of the output voltage of the regenerative inverter can continue to be output as the predicted reference phase by an internal timer, so it is possible to quickly synchronize with the power supply phase when power is restored.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the system configuration of an embodiment of a regenerative inverter that employs the regenerative inverter reference phase calibration method according to the present invention, FIG. 2 is a diagram explaining the operation of the phase detection circuit according to the present invention, and FIG. The figure is a waveform diagram showing an example of power supply phase detection. 1...DC rectified power supply, 2...Regenerative inverter, 3...
- DC main circuit smoothing capacitor, 4... Current detector, 5... Voltage transformer, 6... Regenerative power transformer, 7 Reference phase detection circuit, 8.9... Phase command, ], O. ... Adder, 11 ... sin ta
ble, 12・voltage command, 13...adder, 14...
Automatic voltage regulator AVR115... Multiplier, 16. Adder, 17. Inverter, 18.. Adder, 19.. Inverter, 20.. Adder, 21.. Adder, 22. ...Inverter, 23...Adder, 25...Automatic current regulator AC
R126... Adder, 27... Pulse width control circuit, 3
1...Timer signal, 32...Power supply phase detection signal, 3
3...U-phase detection voltage, 34...V-phase detection voltage, 35...-V-phase detection voltage, 36...U-phase phase detection signal, 37...W-phase phase detection signal,

Claims (1)

[Claims] 1. Detect the phase of the output voltage of the regenerative inverter, and multiply the DC voltage command to the DC main circuit by the phase detection value to create an AC phase voltage command and calculate the current command for each AC phase. In the reference phase detection method for a regenerative inverter for synchronizing the phase of the output voltage of the regenerative inverter with the phase of the power source, the means for detecting the reference phase is provided with a timer that tracks the cycle of the power source, and the instantaneous voltage of the power source is A method for detecting a reference phase of a regenerative inverter, comprising controlling the phase of the regenerative inverter to perform regeneration based on a predicted power cycle held by the timer when recovering from a power outage, phase loss, or the like. 2. In the reference phase detection method for a regenerative inverter according to claim 1, means is provided for comparing the phase detection value with the power supply specification cycle, and the power supply phase detection value is the previous value + 1/f seconds (where f is the power supply specification frequency ), the timer is set to follow the phase detection value when the phase detection value is close to the phase detection value, and the timer is set to the power supply specification value when it is far from the phase detection value. 3. In the reference phase detection method for a regenerative inverter according to claim 2, a counter is provided to evaluate the power supply cycle detected by the phase detection value, and when the power supply phase detection value is close to the previous value + 1/f seconds, the counter is incremented. If the cumulative value of the evaluation count exceeds a predetermined value, regeneration is performed based on the power phase detection signal, and if the cumulative value of the evaluation count is less than or equal to the predetermined value, the phase A reference phase detection method for a regenerative inverter, characterized in that regeneration is performed according to an expected power supply cycle based on a phase detection signal held by a timer of a detection circuit. 4. The reference phase detection method for a regenerative inverter according to claim 3, wherein the regenerative inverter is stopped when the cumulative value of the evaluation count falls below a predetermined value that is lower than the predetermined value. Reference phase detection method for regenerative inverter. 5. In the reference phase detection method for a regenerative inverter according to any one of claims 2 to 4, a plurality of evaluation counters are provided for each predetermined deviation from the power supply specification cycle, and when the phase is outside the correction range, the evaluation counter is A reference phase detection method for a regenerative inverter, characterized in that regeneration is performed according to a power supply cycle in which the cumulative value of is maximized.