TWI807641B - Uninterruptible power device and method of magnetic flux compensation the same - Google Patents

Abstract

An uninterruptible power device is configured to be coupled between a grid and a load, and the uninterruptible power device includes a bypass path, a power conversion module, and a control module. The bypass path is coupled to the grid through the grid end, and is coupled to the load through the load end. The bypass path includes a first thyristor and a second thyristor connected in reverse parallel, and a DC/AC conversion circuit of the power conversion module is coupled to the load end. During a forced commutation period that the load end injects a second voltage to turn off the first thyristor and the second thyristor, the control module calculates a flux offset based on an error between the second voltage and a voltage command, and provides a compensation command in response to the flux offset. The control module controls the DC/AC conversion circuit to provide a third voltage to the load end based on the compensation command and the voltage command.

Description

Uninterruptible Power Device and Its Magnetic Flux Compensation Method

The invention relates to an uninterruptible power device and its magnetic flux compensation method, especially to an uninterruptible power device with magnetic flux compensation and its magnetic flux compensation method.

Due to the increasing popularity of key electronic systems (such as servers, central control systems, etc.) in the current electronic system field, more and more attention has been paid to the continuity and stability of power supply. Most of today's solutions will add uninterruptible power supply units to meet the needs of critical electronic systems. Taking the conventional uninterruptible device 100A in FIG. 1A as an example, the uninterruptible device 100A includes a bypass path 1 and a power conversion module 2 , and the power conversion module 2 is connected to the bypass path 1 in parallel. The bypass path 1 includes a switch unit 12 , and the switch unit 12 includes a first thyristor 122 and a second thyristor 124 connected in antiparallel. The voltage provided by the grid 200 passes through the grid terminal 100 - 1 , the switch unit 12 to the load terminal 100 - 2 to supply power to the load 300 . When the power grid 200 fails, the UPS 100 controls the switch unit 12 to turn off, and controls the power conversion module 2 to provide backup power to the load 300 .

However, due to the switching characteristics of the thyristor, when there is current passing through, the switch unit 12 cannot be turned off by the control signal. During the forced commutation period FC, a reverse voltage is applied to the load terminal 100 - 2 , so that the first thyristor 122 and the second thyristor 124 are quickly turned off. However, as shown in FIG. 1B , when a transformer is installed inside the load 300 , when FC applies a reverse voltage to the load terminal 100 - 2 during the forced commutation period, the magnetic flux of the transformer will deviate to generate an inrush current, thereby triggering the overcurrent protection mechanism and causing the voltage supplied to the load 300 by the uninterruptible power supply 100A to be abnormal.

Therefore, how to design an uninterruptible power supply device with magnetic flux compensation and its magnetic flux compensation method to maintain the balance of magnetic flux and avoid triggering the overcurrent protection mechanism of the power conversion module due to excessive inrush current is a major topic that the author of this project wants to study.

In order to solve the above problems, the present invention provides an uninterruptible power supply device with magnetic flux compensation to overcome the problems of the prior art. Therefore, the uninterruptible device of the present invention is configured to be coupled between the grid and the load, and the uninterruptible device includes a bypass path, a power conversion module and a control module. The bypass path is coupled to the grid through the grid end and coupled to the load through the load end. The bypass path includes a switch unit, and the switch unit includes a first thyristor and a second thyristor, and the first thyristor and the second thyristor are connected in antiparallel. The bypass path is used for receiving the first voltage through the grid end and transmitting the first voltage to the load end. The power conversion module includes an AC-DC conversion circuit and a DC-AC conversion circuit. The AC-DC conversion circuit is coupled to the grid terminal, and the DC-AC conversion circuit is coupled to the AC-DC conversion circuit and the load terminal. The control module is coupled to the DC-AC conversion circuit, and the control module calculates the magnetic flux offset based on the error between the second voltage and the voltage command during the forced commutation of the first thyristor and the second thyristor by injecting the second voltage into the load end, and provides a response magnetic flux offset compensation order. The control module controls the DC-AC conversion circuit to provide the third voltage to the load terminal based on the compensation command and the voltage command.

In order to solve the above problems, the present invention provides a magnetic flux compensation method for an uninterruptible power supply with magnetic flux compensation to overcome the problems of the prior art. Therefore, the magnetic flux compensation method of the present invention performs magnetic flux compensation on the uninterruptible power supply configured to be coupled between the power grid and the load. The UPS includes a bypass path and a power conversion module, and the bypass path is coupled to the grid and the load. The bypass path includes a switch unit, and the switch unit includes a first thyristor and a second thyristor connected in antiparallel. The bypass path receives the first voltage provided by the grid through the grid terminal, and transmits the first voltage to the load terminal coupled to the load. The magnetic flux compensation method includes the following steps: (a) Knowing that the first voltage is abnormal. (b) Injecting a second voltage into the load terminal during the period of forced commutation according to the abnormality of the first voltage, so as to turn off the first thyristor and the second thyristor. (c) calculating a magnetic flux offset based on an error amount between the second voltage and the voltage command, and calculating a compensation amount based on the magnetic flux offset. (d) providing a compensation command corresponding to the compensation amount, so as to control the DC/AC conversion circuit of the power conversion module to provide the third voltage to the load terminal based on the compensation command and the voltage command.

The main purpose and function of the present invention is that the control module detects and records the magnetic flux offset of the load terminal voltage during the forced commutation period, and after the thyristor is successfully turned off, adjusts the third voltage output by the DC-AC conversion circuit to compensate the magnetic flux, so as to maintain the balance of the magnetic flux and achieve the effect of suppressing large currents.

In order to further understand the technology, means and effects of the present invention to achieve the intended purpose, please refer to the following detailed description and accompanying drawings of the present invention. It is believed that the purpose, features and characteristics of the present invention can be obtained from this. A deep and specific understanding, however, the attached drawings are only for reference and illustration, and are not used to limit the present invention.

100, 100’, 100A: UPS

100-1: grid end

100-2: load end

1, 1': bypass path

12: switch unit

122: The first thyramid

124: The second thyramid

2: Power conversion module

22: AC-DC conversion circuit

24: Energy storage unit

26, 26': DC to AC conversion circuit

28: DC-DC conversion circuit

3, 3': control module

32: The first control module

322, 322': the first control unit

322-1: Integral unit

322-2: filter unit

324, 324': the second control unit

324-1, 324-1': Restriction unit

S1: selector

ka~kc: constant

kmin: minimum value

324-2: Zero sequence balance unit

34: Second control module

4: Detection unit

200: grid

300: load

V1: first voltage

V2, V2a~V2c: the second voltage

V3: the third voltage

Vbus: DC voltage

Sc: control signal

Son: conduction signal

Soff: shutdown signal

Vx, cmd, Va, cmd~Vc, cmd: voltage command

Vcmd: compensation command

Er, Era~Erc: error amount

Vx, Va~Vc: Magnetic flux offset

Δ’Vx,cmp, Δ’Va,cmp~Δ’Vc,cmp: compensation amount

ΔVx,cmp, ΔVa,cmp~ΔVc,cmp: residual compensation amount

Vmax: the maximum amount of compensation

Vinj: injection volume

I~III, IIIa~IIIc: waveform

t0~t3: time

FC: during forced commutation

(S100)~(S400): Steps

Fig. 1A is a circuit block diagram of a known uninterruptible power device; Fig. 1B is a schematic diagram of magnetic flux offset; Fig. 2A is a circuit block diagram of the first embodiment of the uninterruptible power device with magnetic flux compensation according to the present invention; Fig. 2B is a circuit block diagram of the second embodiment of the uninterruptible power device with magnetic flux compensation according to the present invention; Schematic diagram; FIG. 4A is a schematic block diagram of the second embodiment of the first control module of the present invention; FIG. 4B is a schematic block diagram of the second embodiment of the limiting unit of the present invention; FIG. 4C is a schematic diagram of the compensation waveform of the second embodiment of the uninterruptible power supply device of the present invention; and FIG.

The technical content and detailed description of the present invention are explained as follows with the drawings: please refer to FIG. 2A which is the circuit block diagram of the first embodiment of the uninterruptible power supply device with magnetic flux compensation of the present invention, and refer to FIGS. 1A~1B for complex cooperation. In this embodiment, the UPS 100 is configured as a single-phase system. The UPS 100 is configured to be coupled between the grid 200 and the load 300, and includes a grid terminal 100-1 and a load terminal 100-2. The grid terminal 100 - 1 is coupled to the grid 200 and receives a first voltage V1 provided by the grid 200 . The load terminal 100-2 is coupled to the load 300 and provides power to the load 300 to maintain The load 300 operates stably and normally. The UPS 100 also includes a bypass path 1, at least one power conversion module 2 (one is shown) and a control module 3, and one end of the bypass path 1 is coupled to the grid 200 through the grid terminal 100-1, and the other end is coupled to the load 300 through the load terminal 100-2. The bypass path 1 includes a switch unit 12 , and the switch unit 12 is serially connected to the bypass path 1 . The switch unit 12 includes a first thyristor 122 and a second thyristor 124 , and the first thyristor 122 and the second thyristor 124 are connected in antiparallel. The bypass path 1 is used to receive the first voltage V1 through the grid terminal 100-1, and transmit the first voltage V1 to the load terminal 100-2 through the switch unit 12, so as to supply power to the load terminal 100-2.

The power conversion module 2 is coupled to the grid terminal 100 - 1 and the load terminal 100 - 2 , and is used for converting the first voltage V1 into a third voltage V3 to provide the third voltage V3 to supply power to the load 300 . Specifically, the power conversion module 2 includes an AC-DC conversion circuit 22 , an energy storage unit 24 and a DC-AC conversion circuit 26 . The AC-DC conversion circuit 22 is coupled to the grid terminal 100 - 1 and used for converting the first voltage V1 into a DC bus voltage Vbus. The DC-AC conversion circuit 26 is coupled to the AC-DC conversion circuit 22, the energy storage unit 24 and the load terminal 100-2, and is used for converting the DC bus voltage Vbus into a third voltage V3. Wherein, the power conversion module 2 may further include a DC-DC conversion circuit 28 , and the DC-DC conversion circuit 28 is coupled between the AC-DC conversion circuit 22 , the energy storage unit 24 and the DC-AC conversion circuit 26 . The DC-DC conversion circuit 28 is used to convert the voltage stored in the energy storage unit 24 into a DC bus voltage Vbus, so that the converted DC bus voltage Vbus is suitable for the DC-AC conversion circuit 26 to generate the third voltage V3.

The control module 3 is coupled to the DC-AC conversion circuit 26 and the switch unit 12, and can detect the voltage and current of the load terminal 100-2 through the detection unit 4 to control the switch unit 12 to turn on or off, and provide a control signal Sc (which can be a pulse width modulation signal) to control the DC-AC conversion circuit 26 to provide the third voltage V3. Specifically, the control module 3 can determine whether the first voltage V1 is abnormal by detecting the grid terminal 100-1, or by receiving a detection signal provided by, for example but not limited to, an external device (not shown in the figure). Judging or learning whether the first voltage V1 is abnormal. It is worth mentioning that the control module 3 can include several microprocessors (Microprocessor), so the control module 3 can not only control the DC-AC conversion circuit 26 and the switch unit 12, but also can be used to control other circuits of the uninterruptible power supply device 100 (such as but not limited to the AC-DC conversion circuit 22, the DC-DC conversion circuit 28, etc.), and the control module 3 and the power conversion module 2 can be installed in the same housing or belong to different housings. describe.

When the first voltage V1 is normal, the UPS 100 can operate in a high-efficiency mode, and the control module 3 provides a conduction signal Son to control the switch unit 12 to conduct (that is, to control the conduction of the first thyristor 122 and the second thyristor 124 ), so that the first voltage V1 is provided to the load 300 through the bypass path 1 . At this time, the control module 3 can control the power conversion module 2 to stand by and not operate, or the control module 3 can also control the power conversion module 2 to perform harmonic compensation for the load 300 .

When the first voltage V1 is abnormal, the control module 3 uses the DC/AC conversion circuit 26 to forcibly shut down the path of the UPS 100 . After the path is forcibly shut down, the control module 3 controls the DC/AC conversion circuit 26 to provide the third voltage V3 to supply power to the load 300 . Furthermore, due to the characteristics of the thyristor, when the thyristor still has current flowing, the thyristor cannot be shut off quickly through the control signal. Therefore, when the first voltage V1 is abnormal, the control module 3 first provides the shutdown signal Soff to the first thyristor 122 and the second thyristor 124 to ensure that the thyristor is not triggered again, and controls the uninterruptible device 100 to inject the second voltage V2 into the load terminal 100-2, so as to provide a reverse bias voltage to the unturned thyristor and quickly shut off the thyristor. Wherein, the period during which the thyristor is turned off is called the forced commutation period in the present invention, and the second voltage V2 injected into the load terminal 100-2 may be provided by the control module 3 controlling an additional auxiliary circuit (not shown in the figure), or provided by the control module 3 controlling the DC/AC conversion circuit 26.

After the aforementioned period of forced commutation, both the first thyristor 122 and the second thyristor 124 are turned off, and the power conversion module 2 operates in the uninterruptible power supply mode, that is, the third voltage V3 provided by the power conversion module 2 provides backup power to the load 300 . It is worth mentioning that in one embodiment of the present invention, the first voltage V1 being normal means that the voltage amplitude, phase, and frequency of the AC voltage are within a predetermined range that meets the specifications. It may tolerate some harmonic distortion or unstable amplitude, but still meet the standards required for the load 300 to operate. On the other hand, the abnormality of the first voltage V1 may indicate that the voltage amplitude, phase and frequency of the AC voltage do not meet the specifications, which may be caused by insufficient stability of the grid 200, poor contact of components, excessive harmonic distortion, or power failure of the grid 200.

Since the second voltage V2 injected into the load terminal 100 - 2 during the forced commutation is to quickly turn off the thyristor, it is easy to cause the magnetic flux deviation of the transformer inside the subsequent load 300 . This phenomenon will cause the transformer to be saturated and generate inrush current, which may trigger the overcurrent protection mechanism of the UPS 100 . Therefore, the main purpose and function of the present invention is that the control module 3 detects and records the magnetic flux offset of the load terminal 100-2 voltage during the forced commutation period (i.e. the period during which the second voltage V2 is injected), and compensates the magnetic flux after the thyristor is successfully turned off (i.e. adjusts the third voltage V3 output by the DC/AC conversion circuit 26 to compensate the magnetic flux) to maintain the balance of the magnetic flux and suppress the inrush current.

Specifically, the control module 3 includes a first control module 32 and a second control module 34 , the first control module 32 is coupled to the load terminal 100 - 2 , and the second control module 34 is coupled to the DC/AC conversion circuit 26 and the first control module 32 . The first control module 32 calculates the flux offset during the forced commutation based on the error between the second voltage V2 and the voltage command, and the first control module 32 calculates a compensation amount based on the flux offset to provide a compensation command Vcmd corresponding to the compensation amount. The second control module 34 modulates the control signal Sc based on the compensation command Vcmd and the voltage command, so as to control the DC/AC conversion circuit 26 through the control signal Sc. It is hereby stated that the first control module 32 and the second control module 34 are only for the convenience of illustration. The control method of the invention does not mean that the first control module 32 and the second control module 34 must be separate modules, nor is it limited to be composed of circuit elements. In one embodiment, the first control module 32 and the second control module 34 are implemented by a microprocessor (Microprocessor) with a corresponding program.

After the control module 3 provides the shutdown signal Soff to the first thyristor 122 and the second thyristor 124, and the uninterruptible power supply 100 injects the second voltage V2 into the load terminal 100-2. During the forced commutation of injecting the second voltage V2, the control module 3 calculates the flux offset based on the error between the second voltage V2 and the voltage command, and provides a compensation command Vcmd corresponding to the flux offset after the thyristor is turned off. The control module 3 provides a control signal Sc to the DC-AC conversion circuit 26 based on the compensation command Vcmd, so as to control the DC-AC conversion circuit 26 to provide the third voltage V3 to the load terminal 100-2, so as to compensate the magnetic flux offset and prevent the downstream transformer from being saturated.

The voltage command is usually a sine wave command (fundamental frequency). When the first voltage V1 is normal (that is, when the first thyristor 122 and the second thyristor 124 are conducting), the control module 3 obtains its phase by observing the first voltage V1 by itself through the detection unit 4, and then generates a voltage command with the same phase as the first voltage V1, or the voltage command can be generated by the control module 3 itself (the phase may be different from the first voltage V1). Even if the first voltage V1 is abnormal, the voltage command is not disturbed by the abnormal first voltage V1 and still maintains the sine wave command. The purpose of the voltage command is that when the UPS 100 operates in the UPS mode (that is, the power conversion module 2 provides power to the load 300 ), the control module 3 controls the DC/AC conversion circuit 26 to provide the third voltage V3 based on the voltage command.

Please refer to FIG. 2B , which is a circuit block diagram of the second embodiment of the uninterruptible power supply device with magnetic flux compensation according to the present invention, and refer to FIG. 2A for the combination. The difference between the uninterruptible device 100' of this embodiment and the uninterruptible device 100 of FIG. 2A is that the uninterruptible device 100' is configured as a three-phase system. The bypass path 1' correspondingly includes three sets of switch units 12, and each power conversion module 2' (shown in multiple sets) is a three-phase input, three phase output, and the control module 3' controls the uninterruptible power supply 100' based on whether the first voltage V1 is normal or not. Wherein, the detailed structure and its control method not shown in the uninterruptible power supply device 100' in FIG. 2B can be referred to in FIG. 2A , and will not be repeated here.

Please refer to FIG. 3A which is a schematic block diagram of the first embodiment of the first control module of the present invention, and refer to FIGS. 2A-2B for complex cooperation. In this embodiment, the DC-AC conversion circuit 26 is a single-phase output circuit. The first control module 32 includes a first control unit 322 and a second control unit 324, and the first control unit 322 includes an integration unit 322-1. During the forced commutation period, the first control unit 322 generates an error amount Er based on the second voltage V2 and the voltage command Vx,cmd, and the integrating unit 322-1 receives and integrates the error amount Er to achieve the purpose of accumulation. Since the magnetic flux is the integral of the voltage, the error Er is integrated by the integrating unit 322-1 to obtain the magnetic flux offset Vx, which can be regarded as the total offset of the magnetic flux during the forced commutation. Optionally, the first control unit 322 may further include a filtering unit 322-2, and the filtering unit 322-2 may be a low-pass filter (LPF). The filtering unit 322-2 is coupled to the integrating unit 322-1 and the second control unit 324, and is used for filtering noise generated by sampling.

When the forced commutation period ends, the UPS 100 will operate in the UPS mode, that is, the power conversion module 2 starts to supply power to the load 300, and the second control unit 324 receives the magnetic flux offset Vx at this stage, and provides a compensation command Vcmd corresponding to the magnetic flux offset. Specifically, the second control unit 324 includes a limiting unit 324-1, and the limiting unit 324-1 is configured to receive the magnetic flux offset Vx to limit the output compensation command Vcmd. Since the magnetic flux compensation will cause a certain degree of voltage distortion (that is, the distortion of the third voltage V3 ), if the amount of compensation is too large, the distortion of the third voltage V3 will be too severe, which may have adverse effects on the load 300 . Therefore, the first control module 32 avoids overcompensation via the limiting unit 324-1. Specifically, the second control unit 324 generates the remaining compensation amount ΔVx,cmp based on the magnetic flux offset Vx and the compensation amount Δ'Vx,cmp, and the limiting unit 324-1 limits the compensation amount of the remaining compensation amount ΔVx,cmp to provide compensation. The compensation amount Δ'Vx,cmp, and the second control unit 324 provides the compensation command Vcmd to the second control module 34 based on the compensation amount Δ'Vx,cmp. The second control module 34 modulates the control signal Sc based on the compensation command Vcmd and the voltage command Vx,cmd to superimpose the compensated voltage on the sinusoidal voltage to demagnetize the transformer of the downstream load 300 to avoid saturation.

In short, after the second control unit 324 obtains the magnetic flux offset Vx, the actual compensation amount (that is, the compensation amount Δ'Vx,cmp) is obtained through the limiting unit 324-1. Then, after deducting the actual compensation amount from the magnetic flux offset Vx, the remaining uncompensated amount (ie, the remaining compensation amount ΔVx,cmp) is obtained. In this way, after several loops, the amount of offset can be gradually compensated. For example, assume that the limiting unit 324 - 1 sets the compensable amount of one turn as 10, and the first control unit 322 calculates the magnetic flux offset Vx during the forced commutation as 45. In this way, after the magnetic flux offset Vx is limited by the limiting unit 324-1, the actual compensation amount that can be provided is 10, and after the magnetic flux offset Vx deducts the actual compensation amount (10) of this loop, there remains a remaining compensation amount ΔVx,cmp of 35. Therefore, after several loops, the remaining compensation amount ΔVx,cmp(35) is gradually made up to 0.

Please refer to FIG. 3B , which is a schematic block diagram of the first embodiment of the restriction unit of the present invention, and refer to FIGS. 2A-3A for the combination. The limiting unit 324-1 mainly limits the amount that can be compensated by setting the maximum amount of compensation Vmax and the calculation of the injection amount Vinj. The remaining compensation amount ΔVx,cmp is limited to the compensation amount Δ’Vx,cmp after passing through the limiting unit 324-1, so as to avoid voltage distortion caused by too much compensation at one time. Furthermore, the maximum amount of compensation Vmax can be a value defined by the user, and the injection amount Vinj is mainly the error amount between the DC bus voltage Vbus and the voltage command Vx,cmd to avoid over-modulation, and the smaller value of the two is the limit value of the limiting unit 324-1 to limit the remaining compensation amount ΔVx,cmp.

Please refer to FIG. 3C , which is a schematic diagram of the compensation waveform of the first embodiment of the uninterruptible device of the present invention, and refer to FIGS. 2A to 3B for the combination. In this embodiment, the compensation waveform of the single-phase uninterruptible power supply 100 is illustrated. Wherein, the waveform I is the voltage command Vx,cmd, the waveform II is the voltage waveform detected by the load terminal 100-2, and the waveform III is a schematic diagram of flux compensation changes. During time t0˜t1, the first voltage V1 is normal, so the voltage waveform detected by the load terminal 100-2 is the first voltage V1. At time t1˜t2, it is assumed that the first voltage V1 is abnormal, so the uninterruptible device 100 enters the forced commutation period FC. At this time, the control module 3 controls the DC-AC conversion circuit 26 to output the second voltage V2 to the load terminal 100-2 for forced commutation. In order to quickly turn off the first thyristor 122 and the second thyristor 124 , the voltage waveform of the load terminal 100 - 2 is not a sine wave voltage, but is the second voltage V2 at this time. Therefore, at time t1~t2, the first control unit 322 calculates the magnetic flux offset, and it can be seen from the waveform III that the magnetic flux change generated by the difference between the second voltage V2 and the voltage command Vx,cmd is accumulated. After time t2, the thyristor is completely turned off, the control module 3 controls the DC-AC conversion circuit 26 to provide the third voltage V3, and the second control unit 324 compensates for the magnetic flux offset of FC during the forced commutation. Therefore, it can be clearly seen that the magnetic flux gradually returns to zero. Also because the limiting unit 324-1 limits the amount of compensation, even though the waveform distortion caused by the injection of the second voltage V2 is serious, the third voltage V3 is only slightly different from the waveform of the voltage command Vx,cmd, but still roughly similar to a sine wave. Until time t3, the magnetic flux has been compensated, and the third voltage V3 returns to be the same as the voltage command Vx,cmd.

Please refer to FIG. 4A , which is a schematic block diagram of the second embodiment of the first control module of the present invention, and refer to FIGS. 2A to 3C for complex cooperation. In this embodiment, the DC-AC conversion circuit 26' is a three-phase output circuit. The first control unit 322' of the first control module 32' generates the error amounts Era~Erc of each phase based on the second voltages V2a~V2c of each phase and the voltage commands Va,cmd~Vc,cmd, and after being integrated by the integration unit 322-1, the magnetic flux offsets Va~Vc of each phase can be obtained. The second control unit 324' includes a limiting unit 324-1' and a zero sequence balance unit 324-2. The second control unit 324' generates a residual compensation amount ΔVa,cmp~ΔVc,cmp based on the flux offset Va~Vc and the compensation amount Δ'Va,cmp~Δ'Vc,cmp, and the zero sequence balance unit 324- 2 Carry out zero-sequence component deduction for the residual compensation amount ΔVa,cmp~ΔVc,cmp of each phase respectively, so as to deduct invalid zero-sequence components. Specifically, since the DC-AC conversion circuit 26' is a three-phase output circuit, the three-phase parameters under ideal conditions are all symmetrical. However, due to differences in three-phase loads, three-phase lines and power sources, they generally operate asymmetrically. Therefore, when analyzing the asymmetrical three-phase output, it can be decomposed into positive sequence component, negative sequence component and zero sequence component by using the symmetrical component method. Since the zero-sequence component belongs to three components of the same size and phase, if the zero-sequence component is not deducted, the compensation for this component is invalid compensation.

The limiting unit 324-1' limits the compensation amount of the remaining compensation amount ΔVa,cmp~ΔVc,cmp of each phase to provide the compensation amount Δ'Va,cmp~Δ'Vc,cmp of each phase, so as to provide the compensation command Vcmd to the second control module 34' accordingly. d. The second control module 34' modulates the control signal Sc based on the compensation command Vcmd and the voltage commands Va,cmd~Vc,cmd to superimpose the compensated voltage on the original sine wave voltage. The second control module 34, 34' can be a pulse width modulation controller known to those skilled in the art, and generates a corresponding pulse width modulation signal according to a voltage command, and details will not be repeated here.

Please refer to FIG. 4B , which is a schematic block diagram of the second embodiment of the restriction unit of the present invention, and refer to FIGS. 2A-4A for the combination. The difference between the limiting unit 324-1' and the limiting unit 324-1 in FIG. 3B is that the limiting unit 324-1' is suitable for a three-phase circuit. The maximum amount of compensation Vmax and the injection amount Vinj of each phase will be selectively switched by the selector S1, the maximum amount, the injection amount and the minimum amount, and then divided by the corresponding residual compensation amount ΔVa,cmp~ΔVc,cmp by the divider to obtain constants ka~kc. The constants ka~kc will pass through a control block Min to obtain the minimum value kmin of the three constants ka~kc, so as to multiply the remaining compensation amount ΔVa, cmpa~ΔVc,cmp by the minimum value kmin between 0-1 to obtain the compensation amount Δ’Va,cmp~Δ’Vc,cmp. It is worth mentioning that in one embodiment of the present invention, shown in Figure 3B, 4B The limiting methods and control blocks of the limiting units 324-1 and 324-1' for the remaining compensation amount ΔVx,cmp, ΔVa,cmp˜ΔVc,cmp are just an exemplary embodiment and are not limited thereto. Therefore, any limiting method and control block that can limit the remaining compensation amount ΔVx,cmp, ΔVa,cmp~ΔVc,cmp to avoid causing voltage distortion should be included in the scope of this embodiment. For example, the limiting unit can also be set to a fixed and small magnification, and the compensation can still be completed. The difference is only the difference in the compensation speed.

Please refer to FIG. 4C , which is a schematic diagram of the compensation waveform of the second embodiment of the uninterruptible device of the present invention, and refer to FIGS. 2A-4B for complex cooperation. In this embodiment, it shows the compensation waveform of the three-phase uninterruptible device 100'. Among them, the waveform I is the voltage command Va,cmd~Vc,cmd, and the waveforms IIIa~IIIc are the schematic diagrams of the magnetic flux compensation changes of each phase. Waveform II is the voltage waveform detected by the load terminal 100-2, wherein the codes a~c can represent R phase, S phase and T phase respectively, and in one embodiment of the present invention, the difference between FIG. 4C and FIG. 3C is only the single-phase or three-phase compensation waveform. Therefore, the specific waveform description of the waveform in FIG. 4C can be equivalently deduced by referring to FIG.

Please refer to FIG. 5 , which is a flowchart of the magnetic flux compensation method of the uninterruptible power supply device with magnetic flux compensation according to the present invention, and refer to FIGS. 2A to 4C for complex cooperation. The magnetic flux compensation method of the present invention mainly compensates the magnetic flux offset caused by FC during the forced commutation period of the uninterruptible power supply 100 , so as to avoid the unbalanced magnetic flux of the transformer inside the subsequent load 300 . Therefore, the magnetic flux compensation method of the uninterruptible power supply 100 includes learning that the first voltage is abnormal ( S100 ). The control module 3 can determine whether the first voltage V1 is abnormal by detecting the grid terminal 100-1, or determine or know whether the first voltage V1 is abnormal by receiving detection signals provided by, for example but not limited to, external devices (not shown in the figure). Then, according to the abnormality of the first voltage, a second voltage is injected into the load terminal during the period of forced commutation, so as to turn off the first thyristor and the second thyristor (S200). The control module 3 ensures that the thyristor will not be triggered again by providing the shutdown signal Soff to the thyristor, and controls the uninterruptible device 100 to inject the second voltage V2 into the load terminal 100-2, so as to provide a reverse bias voltage to the unturned thyristor and turn off the thyristor. The period during which the thyristor is turned off is also referred to as the forced commutation period. The second voltage V2 injected into the load terminal 100-2 can be provided by the control module 3 controlling an additional auxiliary circuit (not shown in the figure), or by the control module 3 controlling the DC/AC conversion circuit 26 to provide.

Then, a magnetic flux offset is calculated based on an error amount between the second voltage and the voltage command, and a compensation amount is calculated based on the magnetic flux offset ( S300 ). A preferred embodiment is to use the control module 3 to calculate the flux offset Vx of FC during the forced commutation based on the error Er between the second voltage V2 and the voltage command, which can mainly obtain the flux offset Vx by integrating the error Er. Then, after the control module 3 obtains the flux offset Vx, the compensation amount is limited by the limiting unit 324-1 to obtain the actual compensation amount (that is, the compensation amount Δ'Vx,cmp), so as to avoid voltage distortion (that is, the distortion of the third voltage V3) caused by excessive single compensation. Finally, a compensation command corresponding to the compensation amount is provided to control the DC/AC conversion circuit of the power conversion module to provide a third voltage to the load terminal based on the compensation command and the voltage command ( S400 ). In a preferred embodiment, the control module 3 modulates the control signal Sc based on the compensation command Vcmd and the voltage command Vx,cmd, so as to control the DC/AC conversion circuit 26 to provide the third voltage V3 to the load terminal 100-2 through the control signal Sc. It is worth mentioning that in one embodiment of the present invention, the detailed flow of the magnetic flux compensation method of the uninterruptible power supply device 100 can be referred to in conjunction with FIGS.

However, the above is only the detailed description and drawings of the preferred specific embodiments of the present invention, but the features of the present invention are not limited thereto, and are not intended to limit the present invention. The scope of the present invention should be based on the scope of the following patent application. All embodiments that conform to the spirit of the scope of the patent application of the present invention and similar changes should be included in the scope of the present invention. Any changes or modifications that can be easily conceived by those familiar with the art in the field of the present invention can be covered by the scope of the patent application below.

100: UPS

100-1: grid end

100-2: load end

1: Bypass path

12: switch unit

122: The first thyramid

124: The second thyramid

2: Power conversion module

22: AC-DC conversion circuit

24: Energy storage unit

26: DC to AC conversion circuit

28: DC-DC conversion circuit

3: Control module

32: The first control module

34: Second control module

4: Detection unit

200: grid

300: load

V1: first voltage

V2: second voltage

V3: the third voltage

Vbus: DC bus voltage

Sc: control signal

Son: conduction signal

Soff: shutdown signal

Vcmd: compensation command

Claims (13)

An uninterruptible device configured to be coupled between a grid and a load, the uninterruptible device includes: a bypass path, coupled to the grid through a grid end, and coupled to the load through a load end; the bypass path includes a switch unit, and the switch unit includes a first thyristor and a second thyristor, the first thyristor and the second thyristor are connected in antiparallel; the bypass path is used to receive a first voltage through the grid end, and transmit the first voltage to the load end; a power conversion module, including an AC-DC conversion circuit and A DC-AC conversion circuit; the AC-DC conversion circuit is coupled to the power grid terminal, and the DC-AC conversion circuit is coupled to the AC-DC conversion circuit and the load terminal; and a control module is coupled to the DC-AC conversion circuit; wherein, the control module calculates a magnetic flux offset based on an error between the second voltage and a voltage command during a forced commutation period when a second voltage is injected into the load terminal and the first thyristor and the second thyristor are turned off, and provides a compensation command in response to the magnetic flux offset; the control module is based on the compensation command and the second thyristor. The voltage command controls the DC-AC conversion circuit to provide a third voltage to the load end. The uninterruptible power supply device as claimed in claim 1, wherein the control module detects the first voltage to obtain the voltage command corresponding to the first voltage. The uninterruptible power supply device as described in claim 1, wherein the control module includes: a first control module coupled to the load terminal; and a second control module coupled to the DC-AC conversion circuit and the first control module; Wherein, the first control module provides the compensation command based on the second voltage and the voltage command, and the second control module modulates a control signal based on the compensation command and the voltage command, so as to control the DC-AC conversion circuit to output the third voltage through the control signal. The uninterruptible power supply device as described in claim 3, wherein the first control module includes: a first control unit, including: an integration unit, used to integrate the error amount to obtain the magnetic flux offset during the forced commutation period; and a filter unit, used to perform a noise filtering on the magnetic flux offset; a second control unit, used to receive the magnetic flux offset. The uninterruptible power supply device as described in claim 4, wherein the DC/AC conversion circuit is a single-phase output circuit, and the second control unit includes: a limiting unit; wherein, the second control unit generates a residual compensation amount based on the difference between the magnetic flux offset and a compensation amount, and provides the compensation command based on the compensation amount; the limiting unit performs a compensation amount limit on the remaining compensation amount to provide the compensation amount. The uninterruptible power supply device as described in claim 4, wherein the DC-AC conversion circuit is a three-phase output circuit, and the second control unit includes: a zero-sequence balance unit; and a limiting unit; wherein, the second control unit generates a residual compensation amount based on the difference between the magnetic flux offset and a compensation amount, and provides the compensation command based on the compensation amount; the zero-sequence balance unit performs a residual compensation amount The zero-sequence component is subtracted, and the limiting unit performs a compensation amount limitation on the remaining compensation amount to provide the compensation amount. A magnetic flux compensation method for an uninterruptible device, which is to perform a magnetic flux compensation on an uninterruptible device configured to be coupled between a grid and a load; the uninterruptible device includes a bypass path and a power conversion module, and the bypass path is coupled to the grid and the load; the bypass path includes a switch unit, and the switch unit includes a first thyristor and a second thyristor connected in antiparallel; the bypass path receives a first voltage provided by the grid through a grid terminal, and transmits the first voltage to a load coupled to the load terminal; the magnetic flux compensation method includes the following steps: (a) knowing the first voltage anomaly; (b) injecting a second voltage into the load terminal during a forced commutation according to the first voltage anomaly to shut off the first thyristor and the second thyristor; (c) calculating a flux offset based on an error amount between the second voltage and a voltage command, and calculating a compensation amount based on the flux offset; The current-to-alternate conversion circuit provides a third voltage to the load terminal. The magnetic flux compensation method as described in Claim 7 further includes the following steps: (a00) knowing that the first voltage is normal; (a01) detecting the first voltage to obtain the voltage command corresponding to the first voltage. The magnetic flux compensation method as claimed in item 7, wherein step (b) includes: controlling the DC/AC conversion circuit to provide the second voltage during the forced commutation period. The magnetic flux compensation method as claimed in item 7, wherein step (d) includes: (d1) modulating a control signal based on the compensation command and the voltage command; and (d2) controlling the DC-AC conversion circuit to provide the third voltage through the control signal. The magnetic flux compensation method as claimed in item 7, wherein step (c) includes: (c1) integrating the error amount to obtain the magnetic flux offset during the forced commutation; (c2) performing a noise filter on the magnetic flux offset. The magnetic flux compensation method as described in Claim 7, wherein the DC/AC conversion circuit is a single-phase output circuit, and the step (c) includes: (c31) generating a residual compensation amount based on the magnetic flux offset and the compensation amount; and (c41) limiting the compensation amount to the residual compensation amount to provide the compensation amount. The magnetic flux compensation method as described in claim 7, wherein the DC/AC conversion circuit is a three-phase output circuit, and step (c) includes: (c32) generating a residual compensation amount based on the magnetic flux offset and the compensation amount; and (c42) performing a zero-sequence component deduction and a compensation amount limitation on the residual compensation amount to provide the compensation amount.

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