JP7147667B2 - Power supply device, relay welding determination device, and relay welding determination method - Google Patents

Description

The present disclosure relates to a power supply device, a relay welding determination device, and a relay welding determination method.

An uninterruptible power supply is a device that maintains power supply to loads virtually uninterruptedly by switching extremely quickly from a storage battery to AC power generated via an inverter in the event of a power failure in the commercial power system. (See, for example, Patent Document 1.). A relay is generally used for switching the power feeding path. For example, in a bypass type uninterruptible power supply that normally supplies power to the load by simply passing it through the device from the commercial power system, during the self-sustained output that converts power from the storage battery and outputs it, the relay for connecting with the commercial power system is open. When the commercial power system recovers from this state, the relay is closed to restore the original state and stop the isolated output.

International Publication No. WO2017/094142

In rare cases, relays may have their contact portions welded together. In this case, even if off control is performed to open the relay, the contact remains on in reality. Even in this state, the control unit intends to open the relay, so there may be a "collision" between the power supply from the commercial power system and the power supply from the stand-alone output. At this time, if there is a phase difference between the voltages, an unfavorable state occurs in which overcurrent flows in the uninterruptible power supply, or conversely, current flows from the uninterruptible power supply to the commercial power system.

In order to prevent such a state, for example, a relay with an auxiliary contact may be used to provide a circuit for checking whether the main circuit contact is opened or closed.
However, an auxiliary contact and a circuit therefor are required, which contributes to an increase in cost. Further, detection by mechanical confirmation of the operation of the auxiliary contact cannot be performed at high speed.

In view of this problem, an object of the present disclosure is to quickly determine whether or not a relay is welded without requiring an auxiliary contact or a dedicated circuit.

The present disclosure includes the following inventions. However, the present invention is defined by the claims.

(power supply)
A power supply device that is connected to an external AC electric circuit and a load and can selectively perform bypass power supply from the AC electric circuit to the load and power supply to the load by a self-sustained output,
a relay provided between a first electric line that draws in the AC electric line and a second electric line connected to the load and having a contact that can be opened and closed;
a power conversion unit provided between the DC power supply and the second electric circuit and having a function of performing power conversion from DC to AC;
a first voltage sensor that detects a voltage between two lines of the first electric circuit;
a second voltage sensor that detects a voltage between two lines of the second electrical circuit;
A control unit that controls the power conversion unit and the relay,
When a voltage is detected in the first electrical circuit by the first voltage sensor during power supply of the self-sustained output, the control unit shifts the phase based on the detection of the second voltage sensor to the detection of the first voltage sensor. The power supply device determines whether or not the relay is welded based on whether or not the frequency deviates from a predetermined range in the synchronization process of matching the phase.

(Relay welding determination device)
When the first AC power supply for normal use is connected to the first electric path on one side of the relay that can be opened and closed, and the load and the second AC power supply for backup are connected to the second electric path on the other side, A welding determination device for a relay,
a first voltage sensor that detects a voltage between two lines of the first electric circuit;
a second voltage sensor that detects a voltage between two lines of the second electrical circuit;
A control unit that controls the second AC power supply and the relay,
The control unit adjusts the phase based on the detection of the second voltage sensor to the first electric circuit when the first voltage sensor detects a voltage in the first electric circuit during power supply from the second AC power supply to the load. 1. This relay weld determination device determines whether or not the relay is welded based on whether or not the frequency deviates from a predetermined range in the synchronization process of matching the phase based on the detection of the voltage sensor.

(Relay welding determination method)
When the first AC power supply for normal use is connected to the first electric path on one side of the relay that can be opened and closed, and the load and the second AC power supply for backup are connected to the second electric path on the other side, A relay welding determination method comprising:
When the first AC power supply fails in a state in which the relay is closed and power is supplied from the first AC power supply to the load, the relay is opened to supply power to the load from the second AC power supply;
When a voltage is detected in the first electric circuit during power supply from the second AC power supply to the load, the frequency exceeds a predetermined range in the synchronization process of matching the phase of the second electric circuit with the phase of the first electric circuit. A welding determination method for relays, wherein the presence or absence of welding of the relays is determined based on whether or not there is a deviation.

According to the present disclosure, it is possible to quickly determine whether or not the relay is welded without requiring an auxiliary contact or a dedicated circuit.

FIG. 1 is a circuit diagram of a power supply. FIG. 2 is a circuit diagram when the power supply device is in a state of power supply by self-sustained output. FIG. 3 is a circuit diagram when the power supply device is in a state of power supply by independent output in a welded state. FIG. 4A is a graph showing waveforms of Vα and Vβ. FIG. 4B is a graph showing linear waveforms of Vd and Vq. FIG. 5 is a control block diagram of the PLL after Vα and Vβ, which are required as a single-phase AC PLL. FIG. 6 is an example of a flowchart showing a process executed by the control unit after starting self-sustaining operation. FIG. 7 is a graph showing an example where the frequency changes beyond the threshold when the relay is welded.

[Description of Embodiments of the Present Disclosure]
Embodiments of the present disclosure include at least the following as gists thereof.

(1) Disclosed is a power supply device that is connected to an external AC circuit and a load, and that can selectively perform bypass power supply from the AC circuit to the load and power supply to the load through a self-sustained output. A relay provided between a first electric line that draws in the AC electric line and a second electric line connected to the load and having a contact that can be opened and closed, and a DC power supply and the second electric line, A power conversion unit having a function of converting power from direct current to alternating current, a first voltage sensor that detects voltage between two lines of the first electric line, and a second voltage sensor that detects voltage between two lines of the second electric line. 2 voltage sensors, and a control unit that controls the power conversion unit and the relay. Then, whether or not the relay is welded based on whether or not the frequency deviates from a predetermined range in the synchronization process of matching the phase based on the detection of the second voltage sensor with the phase based on the detection of the first voltage sensor. is determined.

In the power supply device configured as described above, it is assumed that voltage is detected in the first electric circuit by the first voltage sensor when power is supplied to the load by the self-sustaining output due to a power failure in the first electric circuit. Power is restored. However, it is possible that the contacts of the relay are welded even though the power is not restored. When the relay is normally open and the power is restored, the frequency does not deviate from the predetermined range during the synchronization process of matching the phase based on the detection of the second voltage sensor with the phase based on the detection of the first voltage sensor. . On the other hand, if power is not restored but the contacts of the relay are welded, the frequency will deviate from the predetermined range during the synchronization process. Therefore, the control unit can determine whether or not the relay is welded based on whether or not the frequency deviates from a predetermined range during the synchronization process. In this way, it is possible to quickly determine whether or not the relay is welded without requiring an auxiliary contact or a dedicated circuit.

(2) In the power supply device of (1) above, the control unit adjusts the phase adjustment value for bringing the phase based on the detection of the second voltage sensor closer to the phase based on the detection of the first voltage sensor. It may be determined based on the frequency of the voltage detected by the voltage sensor.
In this case, if the relay is welded, the power conversion unit will adjust its own phase based on its own output, and a situation can be created in which the frequency deviation expands (diverges). .

(3) In the power supply device of (1) or (2), the control unit may determine that the relay is welded when the state of deviation from the predetermined range continues for a predetermined time.
In this case, erroneous determination can be prevented, and reliability and stability of determination can be improved.

(4) In the power supply device according to any one of (1) to (3) above, the control unit determines whether or not the welding occurs during the process of determining whether or not power supply by the self-sustained output can be shifted to the bypass power supply. carry out the judgment.
In this case, even if the determination of the presence/absence of welding is not prepared as a separate process, it can be executed during the determination of whether or not the power supply by the self-sustained output can be shifted to the bypass power supply.

(5) It can also be considered as a relay welding determination device. That is, when the first AC power supply for normal use is connected to the first electric path on one side of the relay that can be opened and closed, and the load and the second AC power supply for backup are connected to the second electric path on the other side. 2, the welding determination device for the relay, the first voltage sensor detecting the voltage between the two lines of the first electric circuit, the second voltage sensor detecting the voltage between the two lines of the second electric circuit, and the a control unit that controls a second AC power supply and the relay, wherein the control unit detects a voltage in the first electric circuit by the first voltage sensor while power is being supplied from the second AC power supply to the load. The welding of the relay is based on whether or not the frequency deviates from a predetermined range in the synchronization process of matching the phase based on the detection of the second voltage sensor with the phase based on the detection of the first voltage sensor. It is a relay welding determination device that determines the presence or absence of welding.

In the welding determination device configured as described above, when power is supplied from the second AC power supply to the load due to a power failure of the first AC power supply, the first voltage sensor detects a voltage in the first electric circuit. , the assumed situation is the power recovery of the first AC power supply. However, it is possible that the contacts of the relay are welded even though the power is not restored. When the relay is normally open and the power is restored, the frequency does not deviate from the predetermined range during the synchronization process of matching the phase based on the detection of the second voltage sensor with the phase based on the detection of the first voltage sensor. . On the other hand, if power is not restored but the contacts of the relay are welded, the frequency will deviate from the predetermined range during the synchronization process. Therefore, the control unit can determine whether or not the relay is welded based on whether or not the frequency deviates from a predetermined range during the synchronization process. In this way, it is possible to quickly determine whether or not the relay is welded without requiring an auxiliary contact or a dedicated circuit.

(6) As a method, the first AC power supply for normal use is connected to the first electric path on one side of the relay that can be opened and closed, and the load and the second AC power supply for backup are connected to the second electric path on the other side. A method for determining welding of a relay when the relay is connected, wherein the relay is closed and the relay is closed when power is lost to the first AC power supply from a state in which power is supplied from the first AC power supply to the load. Power is supplied from the second AC power source to the load by opening the circuit, and when a voltage is detected in the first electrical circuit during power feeding from the second AC power source to the load, the phase of the second electrical circuit is changed to the first power supply. In the relay welding determination method, the presence or absence of welding of the relay is determined based on whether or not the frequency deviates from a predetermined range in the synchronization process for matching the phase of one electric circuit.

In the relay welding determination method as described above, when a voltage is detected in the first electric circuit while power is being supplied from the second AC power supply to the load due to a power failure of the first AC power supply, the situation assumed is This is the power recovery of the first AC power supply. However, it is possible that the contacts of the relay are welded even though the power is not restored. When the relay is normally open and the power is restored, the frequency does not deviate from the predetermined range during the synchronization process of matching the phase of the second electric line with the phase of the first electric line. On the other hand, if power is not restored but the contacts of the relay are welded, the frequency will deviate from the predetermined range during the synchronization process. Therefore, welding of the relay can be detected based on whether or not the frequency deviates from a predetermined range during the synchronization process. In this way, it is possible to quickly determine whether or not the relay is welded without requiring an auxiliary contact or a dedicated circuit.

[Details of the embodiment of the present disclosure]
《Power Supply》
Hereinafter, specific examples of the power supply device (including the relay welding determination device) of the present disclosure will be described with reference to the drawings.
FIG. 1 is a circuit diagram of the power supply device 100. As shown in FIG. The power supply device 100 is connected to the first electric line L<b>1 , which is an AC electric line connected to the commercial power system 11 , and the load 13 . In the electric circuit, the power supply device 100 exists between the external AC electric line and the load 13 in the first electric line L1.

The power supply device 100 includes a storage battery 1 , a power conversion section 2 , a relay (interconnected relay) 3 , a control section 4 , and voltage sensors 5 and 6 . However, the storage battery 1 may be provided outside the power supply device 100 . A breaker for overcurrent protection is provided at the input end of the power supply device 100 connected to the commercial power system 11, but is not shown here. The power converter 2 is provided between the storage battery 1, which is a DC power supply, and the first electric line L1, and includes an inverter and a DC/DC converter (not shown).

The power converter 2 performs DC/AC power conversion between the voltage of the storage battery 1 and the voltage of the first electric line L1. The power conversion unit 2 is capable of bi-directional operation, and can charge the storage battery 1 based on the voltage of the first electric line L1, discharge the storage battery 1, convert the discharged power into AC power, and supply the power to the load 13. can supply. Power converter 2 is controlled by controller 4 .

The relay 3 is provided between the power converter 2 and the first electric line L1. Here, two lines from the power converter 2 to the load 13 are referred to as a second electric line L2, in contrast to the first electric line L1, which is two lines of an AC electric line from the relay 3 to the commercial power system 11. FIG. That is, the system side as viewed from the relay 3 is the first electric line L1. When viewed from the relay 3, the load side and the power converter 2 side is the second electric line L2.

The voltage sensor 5 is provided between two lines of the first electric line L1 and detects a voltage Vg between the two lines. The voltage sensor 6 is provided between the two lines of the second electric line L2 and detects the voltage Vo applied to the load 13 . Detection outputs of the voltage sensors 5 and 6 are sent to the control section 4 . The control unit 4 controls the switching operation of the power conversion unit 2 and the opening/closing operation of the relay 3 . The control unit 4 has a phase locked loop (PLL: Phase Locked Loop) 4p as an internal function. The control unit 4 includes a computer, and the computer executes software (computer program) to implement necessary control functions. Software is stored in a storage device (not shown) of the control unit 4 .

2 and 3 are similar to FIG. 1, but the states of the contacts of the relay 3 and the paths of power supply are different in FIGS. 1 shows the state of "bypass power supply", FIG. 2 shows the state of "power supply by self-sustained output", and FIG. 3 shows the state of "power supply by self-sustained output in the welding state".

In FIG. 1 , the relay 3 is closed and power is supplied to the load 13 from the first electric line L1 through the relay 3 . At this time, the power conversion unit 2 performs power conversion from alternating current to direct current as necessary, and charges the storage battery 1 . This state is a state of bypass power supply in which power is supplied from the first electric line L1 to the load 13 so as to bypass the power supply device 100 . As long as the commercial power system 11 is normal, the state of FIG. 1 is maintained.

FIG. 2 shows a state in which the commercial power system 11 has lost power. Control unit 4 detects a power outage due to a drop in voltage Vg from the state of bypass power supply in FIG. and feeds the load 13 . In this way, power is supplied to the load 13 by the self-sustained output. When the commercial power system 11 recovers power, the control unit 4 detects the power recovery from the increase in the voltage Vg and adjusts the phase of the self-sustained output to the phase of the voltage Vg. When the phases are aligned, the controller 4 closes the relay 3 and stops the switching operation of the power converter 2 . Thus, the state returns to the state of bypass power supply in FIG.

Next, welding of the relay 3 (welding of contacts) will be considered. The welding of the relay 3 may occur due to, for example, a rush current at the moment when the open relay 3 is closed, an overcurrent caused by the load 13, aged deterioration of the contacts, and the like. Even if welding occurs during bypass power supply, the welding will not be found unless a power failure occurs. However, if a power failure occurs or if the unillustrated plug of the power supply device 100 is accidentally pulled out from the outlet, the power supply will be powered by the self-sustained output.

FIG. 3 shows a state in which the relay 3 is welded in such a case. At this time, the control unit 4 opens the relay 3 in terms of control. However, the welding actually closes the relay 3 . The voltage of the self-sustaining output is detected not only by voltage sensor 6 but also by voltage sensor 5 . When the voltage sensor 5 detects that voltage is generated in the first electric line L1, the control unit 4 may determine that the power has been restored. can be identified, the presence or absence of welding can be determined. The key to identification is phase.

《Phase-locked loop》
Here, a single-phase AC PLL will be described.
For an AC PLL, it is common to extract the zero crossings of a single-phase AC voltage and calculate the phase and frequency. However, when the waveform of the input voltage contains distortion, or when the measurement accuracy is poor due to noise, the accuracy tends to deteriorate.

On the other hand, for reference, in the case of a three-phase AC PLL, if the voltages of the phases u, v, and w are Vu, Vv, and Vw, these are converted from three phases to two phases in quadrature by the following equation (1). It can be converted into voltages Vα and Vβ in the α-β coordinate system after the coordinate conversion.

From this, the voltages Vd and Vq in the dq coordinate system, which is a rotating coordinate, can be converted by the following equation (2) using the phase θr.

The voltages Vd and Vq are linear waveforms, and Vq=0 when the PLL is properly performed. Therefore, by performing feedback control so that the voltage Vq=0, accurate phase synchronization can be achieved.

Next, a single-phase AC PLL using the concept of a three-phase AC PLL will be described as a single-phase AC phase-locked loop 4p. A single-phase AC PLL applies a single-phase AC input voltage to Vα in the α-β coordinate system. Vβ does not exist, but is artificially created from Vα.
The graph in FIG. 4A is the waveforms of Vα and Vβ. These can be further converted into voltages Vd and Vq in the dq coordinate system by the above equation (2).

The graph of FIG. 4B is a linear waveform of Vd and Vq, and Vq=0 when the PLL is properly performed. It should be noted that Vd=0 can also be set depending on how the coordinate axes are taken, but essentially the same is true in any case.

FIG. 5 is a control block diagram of the PLL after Vα and Vβ, which are required as a single-phase AC PLL. In the figure, voltages Vα and Vβ in the α-β coordinate system become voltages Vd and Vq by conversion to the dq coordinate system (block B1). Then, feedback control is performed so that the voltage Vq=0 (block B2), and the frequency f and the phase adjustment value Δωt are determined. This .DELTA..omega.t is added to .omega.t one step before (block B3) to determine a new .omega.t.

As the voltage Vβ, for example, differential of Vα can be used.
Assuming that the single-phase AC frequency is f1, the time is t, Vα=sin θ, and Vβ=−cos θ, Vβ can be regarded as a Vα waveform delayed by 90 degrees (π/4 [rad]).
Assuming Vα=A sin(2πf1t) and Vβ=-Acos(2πf1t),
dVα/dt=2πf1·Acos(2πf1t)=−2πf1Vβ (3)
becomes.

from here,
Vβ=−1/(2πf1)×dVa/dt (4)
As a result, an expression using the differential of Vα can be obtained.
In a discretized representation such as calculation by software, the number of samples in one cycle is N, the sampling frequency is fs (=N f1), the sampling period is Δt (=1/fs), and any natural number within the range of N is n (≦N), and the value obtained by subtracting the (n−1)th Vα from the nth Vα is ΔVα, the following equation is obtained.
Vβ=(−1/2πf1)×(ΔVa/Δt)
=(−fs/2πf1)×ΔVa (5)
However, ΔVa=Va (n-th)-Va (n-1-th).
According to the above equations (4) and (5), f1 is included in the coefficient of Vβ, and the coefficient is a function of f1. Therefore, even if there is a phase variation, Vβ changes following the change in f1. That is, the responsiveness to phase fluctuations is good.

Detailed contents of "feedback control so that Vq=0" in block B2 in FIG. 5 will be described.
Proportional integral control is used for feedback control. From formula (2), Vq is
Vq=Vα×cos(ωt)+Vβ×sin(ωt) (6)
is. This Vq is the output of the feedback control.

Since the target value of Vq is 0, the proportional term p_fb assumes the proportional gain g_p as p_fb=g_p×(0−Vq)=−g_p×Vq (7)
becomes. Assuming that the integral term i_fb is g_i as the integral gain and i_fb_before as the integral term one control step before,
i_fb=i_fb_before+g_i*Vq (8)
becomes. The integral term is limited to prevent infinite divergence. As for the upper and lower limit values, an upper limit value of +6 to +10 and a lower limit value of -6 to -10 are appropriate.

The proportional integral term pi_fb is pi_fb=p_fb+i_fb (9)
becomes. The proportional integral term has the same limit as the integral term. A frequency initial value f_init for frequency calculation is determined, and the frequency f_fb calculated from feedback control is: f_fb=pi_fb+f_init (10)
becomes. Note that the frequency initial value f_init is, for example, 55 Hz. This value in between is preferred if the phase locked loop is to accommodate both 50 Hz and 60 Hz.

《Uninterrupted switching between bypass power supply and power supply by stand-alone output》
When the power supply device 100 switches operation from power supply by the isolated output to bypass power supply, it is desirable to switch in a state where there is no voltage difference between the voltage of the isolated output and the system voltage, or even if there is, it is extremely small. For this purpose, the phase and voltage of the isolated output voltage measured by the voltage sensor 6 and the phase and voltage of the system voltage measured by the voltage sensor 5 must be synchronized (matched) with each other.

For phase synchronization, for example, for each zero crossing of the self-sustained output voltage, (phase of Vg - phase of Vo) x coefficient is added to the phase of the self-sustained output voltage to bring the phase difference closer to 0. Feedback control is considered. be done. Also, if the effective value of Vg is a certain voltage or more (for example, 90 V or more), the phase adjustment value Δωt for each control step of the self-sustained output voltage is set to be the same as the phase adjustment value of Vg to synchronize the phase step width. Furthermore, the target voltage of the self-sustaining output voltage is assumed to be a sinusoidal voltage having the same effective value as the system voltage effective value. According to this idea, if the difference between the phases of Vg and Vo becomes a value close to 0, such as 0.01 rad, there is virtually no difference between the instantaneous voltages of Vg and Vo. After switching to power supply, the power supply to the load 13 continues without interruption.

Conversely, when switching from bypass power supply to power supply by self-sustained output, self-sustained operation is started with the instantaneous value of Vg at the moment when a power failure is detected as the start phase of the self-sustained output voltage. As a result, the power supply to the load 13 can be continued substantially without interruption.

《Sample Flowchart》
FIG. 6 is an example of a flow chart showing the process executed by the control unit 4 after starting the self-sustaining operation. In the figure, it is determined whether or not voltage is detected in the first electric line L1 (step S1). When the relay 3 is normal, the relay 3 is open. Therefore, the voltage is not detected until the power is restored, and the self-sustained operation is continued (step S10).

When a voltage equal to or higher than a predetermined value is detected in step S1 due to power recovery, the control unit 4 obtains the phases of the voltages Vg and Vo. Also, the frequency of Vg is calculated (step S2). A phase adjustment value (Δωt) is calculated from this (step S3), and the phase of Vo is brought closer to the phase of Vg (step S4). As a result, the frequency of Vo increases (step S5). Next, the control unit 4 determines whether or not the frequency of Vg is within the normal range (step S6). If the relay 3 is normally open circuited, the frequency of Vg is within the normal range. Next, the control unit 4 determines whether or not the phase and voltage of Vo match the phase and voltage of Vg (step S7).

In step S7, if they do not match yet, the control unit 4 determines whether or not the frequency of Vg exceeds the threshold (step S11). If the relay 3 is normally open circuited, the frequency of Vg will not exceed the threshold. Therefore, steps S2 to S7 and S11 are repeated thereafter. Then, in step S7, when the phase and voltage of Vo match the phase and voltage of Vg, respectively, and synchronization is completed, the control unit 4 closes the relay 3 (step S8) and stops the self-sustained operation ( step S9). When the relay 3 is normally open, the self-sustained operation is stopped through such synchronization processing, and thereafter the state of bypass power supply is restored.

<During relay welding>
On the other hand, if the relay 3, which should normally be open, is welded after starting the self-sustained operation, the self-sustained output voltage is output to the second electrical circuit L2, and the voltage is also output to the system side of the relay 3. , a voltage is detected in the first electric line L1. The control unit 4 obtains the phases of the voltages Vg and Vo. During self-sustained operation, the control unit 4 synchronizes the phase of the self-sustained output voltage Vo in the second electric line L2 with the phase of the voltage Vg in the first electric line L1, and adjusts the frequency of the voltage Vg by the single-phase AC phase-locked loop. Calculate.

In step S2, the control section 4 calculates the voltage frequency from the voltage Vg by means of a phase-locked loop, and the calculated voltage frequency is the frequency of the self-sustaining output voltage. Therefore, the frequency calculated by the phase-locked loop is used to calculate the frequency by the phase-locked loop. The control unit 4 determines the phase adjustment value (Δωt) of Vo based on the calculated frequency (step S3). The phase adjustment value of the voltage Vo of the self-sustaining output is set to the same value as the phase adjustment value of the voltage Vg.

In order to match the phase of the voltage Vo with the phase of the voltage Vg, the control unit 4 performs feedback control to make the phase difference zero. For example, the frequency of the self-sustaining output voltage after adding {(Phase of Vg−Phase of Vo)×Coefficient} increases by the amount that advances the phase. Then, the frequency calculated by the phase-locked loop also becomes higher. The calculated frequency becomes the target value, the frequency is calculated by the phase-locked loop, and the phase adjustment value of the system voltage is calculated from that frequency. and reach the limit. Then the proportional integral term pi_fb will also reach its limit. If the initial frequency value f_init for frequency calculation is set to 55 Hz, the frequency of the voltage measured at Vg calculated by the phase-locked loop is pi_fb+55 Hz. If the upper and lower limits are set to values of ±6 to 10, for example, the self-sustaining output voltage frequency will be 61 Hz to 65 Hz, and the frequency of the voltage measured at Vg will also be the same frequency.

Thus, the frequency of Vo increases (step S5), and the welding of the relay 3 also increases the frequency of Vg. If the relay 3 is normally open and in self-sustained operation, it will output a self-sustaining output voltage of 50 Hz or 60 Hz, and the system voltage will take a frequency of 61 Hz to 65 Hz within the standard frequency ± 0.2 Hz. never. Therefore, if the frequency of Vg continues to exceed the threshold value for a predetermined time or longer, it can be determined that the relay 3 is welded.

Therefore, the control unit 4 determines whether or not the frequency of Vg is within the normal range (step S6). Here, assuming that they are still within the normal range, the control unit 4 determines whether or not the phase and voltage of Vo match those of Vg (step S7), but they do not match.

In step S7, if they do not match yet, the control unit 4 determines whether or not the frequency of Vg exceeds the threshold (step S11). Assuming that the threshold value is not exceeded at this point, steps S2 to S7 and S11 are repeated thereafter. As a result of this repetition, the frequency of Vg deviates from the normal range in step S6, and the frequency of Vg exceeds the threshold in step S11. The control unit 4 determines whether or not the state of exceeding the threshold has continued for a predetermined time (step S12), and repeats steps S2 to S6, S11, and S12 until the predetermined time continues. When the state exceeding the threshold continues for a predetermined time, the control unit 4 determines that the relay is welded (step S13), issues an alarm (step S14), and stops the synchronization (step S15). Note that the synchronization may be stopped and the self-sustained operation may be stopped (step S9).

《Example of waveform》
FIG. 7 is a graph showing an example where the frequency changes beyond the threshold when the relay is welded.
This is a case in which an AC voltage of 101 V and 60 Hz was applied to the AC electric circuit (first electric circuit) as the voltage on the system side, and relay welding occurred. It is a waveform of Vg (upper) and Vo (lower) when a power failure is detected on the grid side from the state of bypass power supply and immediately switched to self-sustained operation in which power is supplied by self-sustaining output of AC 101 V, 60 Hz.

When the standard frequency is 60 Hz, the detection threshold for relay welding detection is set to 63.5 Hz or higher or 56.5 Hz or lower, and the detection time limit is set to 250 ms. In the feedback of the phase-locked loop, the initial frequency value for frequency calculation was set to 55 Hz, and the limiter for the integral term was set to +10 for the upper limit and -10 for the lower limit.

In FIG. 7, voltages applied from the commercial power system are detected as voltage Vg and voltage Vo during bypass power supply. After the power failure, the voltage of the self-sustaining output appears as the voltage Vo and the voltage Vg. However, during self-sustained operation, the frequency rises to 65 Hz. Such a large deviation cannot occur with the frequency of the voltage due to power recovery. Therefore, it can be determined that relay welding has occurred.

《Summary of Disclosure》
As described above, in the power supply device 100 of the present disclosure, when voltage is detected by the voltage sensor 5 in the first electric line L1 during power supply of the self-sustained output, the phase based on the detection of the voltage sensor 6 is detected by the voltage sensor 5. Whether or not the relay 3 is welded can be determined based on whether or not the frequency deviates from a predetermined range in the synchronization process for matching the phase based on the above.

In such a power supply device 100, when a voltage is detected in the first electric line L1 by the voltage sensor 5 while power is being supplied to the load by the self-sustaining output due to a power failure in the first electric line L1, the situation assumed is Power is restored. However, it is possible that the contacts of the relay 3 are welded even though the power is not restored. When the relay 3 is normally open and the power is restored, the frequency does not deviate from the predetermined range in the synchronization process of matching the phase based on the detection of the voltage sensor 6 with the phase based on the detection of the voltage sensor 5. On the other hand, if the contact of the relay 3 is welded even though the power is not restored, the frequency deviates from the predetermined range during the synchronization process. Therefore, the control unit 4 can determine whether or not the relay 3 is welded based on whether or not the frequency deviates from a predetermined range during the synchronization process. In this way, it is possible to quickly determine whether or not the relay is welded without requiring an auxiliary contact or a dedicated circuit.

Based on the frequency of the voltage detected by the voltage sensor 5, the control unit 4 can determine a phase adjustment value for bringing the phase based on the detection of the voltage sensor 6 closer to the phase based on the detection of the voltage sensor 5.
In this case, if the relay 3 is welded, the power converter 2 will adjust its own phase based on its own output, creating a situation in which the frequency deviation expands (diverges). can be done.

Furthermore, it is preferable to determine that the relay 3 is welded when the frequency deviates from the predetermined range for a predetermined period of time. In this case, erroneous determination can be prevented, and reliability and stability of determination can be improved.

In addition, it is preferable that the control unit 4 determines whether or not welding occurs during the process of determining whether or not to switch from the power supply based on the self-sustained output to the bypass power supply. In this case, even if the determination of the presence/absence of welding is not prepared as a separate process, it can be executed during the determination of whether or not the power supply by the self-sustained output can be shifted to the bypass power supply.

Note that the power supply device 100 of the present disclosure can also be said to be a welding determination device for relays. That is, in FIG. 1, the first electric line L1 on one side of the relay 3 that can be opened and closed is connected to the first AC power supply (commercial power system 11) that is normally used, and the second electric line L2 on the other side is connected to the load 13 and , a welding determination device for a relay when a second AC power supply 12 for backup is connected. When the voltage sensor 5 detects the voltage in the first electric line L1 while the second AC power supply 12 is supplying power to the load 13, the control unit 4 changes the phase based on the detection of the voltage sensor 6 to the detection of the voltage sensor 5. Whether or not the relay 3 is welded can be determined based on whether or not the frequency deviates from a predetermined range in the synchronization process for matching the phase.

From the point of view of the method, the first AC power supply (commercial power system 11) that is normally used is connected to the first electric line L1 on one side of the relay 3 that can be opened and closed, and the second electric line L2 on the other side is connected to the load 13 and , a relay welding determination method when the second AC power supply 12 for backup is connected. Then, when the first AC power supply fails in a state in which the load 13 is being supplied with power from the first AC power supply by closing the relay 3, the relay 3 is opened to supply power to the load 13 from the second AC power supply 12, 2. When a voltage is detected in the first electric line L1 during power supply from the AC power supply 12 to the load 13, the frequency deviates from the predetermined range in the synchronization process of matching the phase of the second electric line L2 with the phase of the first electric line L1. and determining whether or not the relay is welded.

"others"
The reasons for setting the numerical values of the limits described in relation to equation (8) are as follows.
In the present disclosure, the voltage of the self-sustained output in the state where the relay 3 is welded is output to the system side of the relay 3, and the relay welding is detected by detecting that the system voltage frequency calculated value deviates from the standard frequency of 50 Hz or 60 Hz. If this limit is too small, it will be difficult to detect welding. On the other hand, if the value is too large, the load will be supplied with a voltage whose frequency deviates too much from the standard frequency, which is not preferable.

In addition, although the welding determination method in the above disclosure has been described with respect to the power supply 100, the method is not limited to the power supply, and can be applied to other devices that perform self-sustained operation due to power failure and switch with a relay.

《Supplement》
It should be noted that the embodiments disclosed this time should be considered as examples in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope of equivalence to the scope of claims.

REFERENCE SIGNS LIST 1 storage battery 2 power conversion unit 3 relay 4 control unit 4p phase locked loop 5, 6 voltage sensor 11 commercial power system (first AC power supply)
12 second AC power supply 13 load 100 power supply device L1 first electric circuit L2 second electric circuit

Claims (6)

A power supply device that is connected to an external AC electric circuit and a load and can selectively perform bypass power supply from the AC electric circuit to the load and power supply to the load by a self-sustained output,
a relay provided between a first electric line that draws in the AC electric line and a second electric line connected to the load and having a contact that can be opened and closed;
a power conversion unit provided between the DC power supply and the second electric circuit and having a function of performing power conversion from DC to AC;
a first voltage sensor that detects a voltage between two lines of the first electrical circuit;
a second voltage sensor that detects a voltage between two lines of the second electrical circuit;
A control unit that controls the power conversion unit and the relay,
When a voltage is detected in the first electrical circuit by the first voltage sensor during power supply of the self-sustained output, the control unit shifts the phase based on the detection of the second voltage sensor to the detection of the first voltage sensor. determining whether or not the relay is welded based on whether or not the frequency deviates from a predetermined range in the synchronization process of matching the phase. The control unit determines a phase adjustment value for bringing the phase based on detection by the second voltage sensor closer to the phase based on detection by the first voltage sensor based on the frequency of the voltage detected by the first voltage sensor. The power supply device according to claim 1 . 3. The power supply device according to claim 1, wherein the control unit determines that the relay is welded when the state of deviating from the predetermined range continues for a predetermined time. 4. The control unit according to any one of claims 1 to 3, wherein the control unit determines whether or not the welding occurs in a process of determining whether or not to switch from power supply based on the self-sustained output to the bypass power supply. Power supply. When the first AC power supply for normal use is connected to the first electric path on one side of the relay that can be opened and closed, and the load and the second AC power supply for backup are connected to the second electric path on the other side, A welding determination device for a relay,
a first voltage sensor that detects a voltage between two lines of the first electrical circuit;
a second voltage sensor that detects a voltage between two lines of the second electrical circuit;
A control unit that controls the second AC power supply and the relay,
The control unit adjusts the phase based on the detection of the second voltage sensor to the first electric circuit when the first voltage sensor detects a voltage in the first electric circuit during power supply from the second AC power supply to the load. 1. A welded relay determination device for determining whether or not the relay is welded based on whether or not a frequency deviates from a predetermined range in a synchronization process for matching a phase based on detection by a voltage sensor. When the first AC power supply for normal use is connected to the first electric path on one side of the relay that can be opened and closed, and the load and the second AC power supply for backup are connected to the second electric path on the other side, A relay welding determination method comprising:
When the first AC power supply fails in a state in which the relay is closed and power is supplied from the first AC power supply to the load, the relay is opened to supply power to the load from the second AC power supply;
When a voltage is detected in the first electric circuit during power supply from the second AC power supply to the load, the frequency exceeds a predetermined range in the synchronization process of matching the phase of the second electric circuit with the phase of the first electric circuit. A method for determining welding of a relay, wherein the presence or absence of welding of the relay is determined based on whether or not the relay is deviated.

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