KR102557010B1 - System for resolving current imbalance and improving power factor by using regeneration of 3-phase unbalanced load current - Google Patents

Abstract

The present invention relates to a system for resolving current imbalance and improving power factor using regeneration of three-phase unbalanced load current. It is to equalize consumption, improve power factor, efficiency and distortion by resupplying unbalanced current as balanced regenerative power, and stabilize system power by supplying balanced three-phase power from the power supply side.
For example, a current sensor unit for measuring load current for each of the three-phase power lines; a load current deficiency calculation unit that calculates a load current deficiency of another phase as a ratio based on a load current of one phase among load currents; an undercurrent extractor for extracting power supplied to a load through a three-phase power line, extracting a load current deficiency of a phase having a current imbalance according to a switching operation performed for each of the three phases, and converting the extracted power into DC; A switching control signal is generated for each phase based on the load current shortfall ratio calculated through the load current shortfall calculation unit and the load current ratio set as a standard, and the switching operation is performed for each of the three phases of the undercurrent extraction unit using the switching control signal. an undercurrent regeneration controller for controlling; and a PFC inverter unit that converts DC power converted through the undercurrent extractor into AC power and regenerates the converted AC power to a three-phase power line through three-phase distribution.

Description

System for resolving current imbalance and improving power factor using regeneration of 3-phase unbalanced load current

An embodiment of the present invention relates to a system for resolving current imbalance and improving power factor using regeneration of three-phase unbalanced load current, and more specifically, current imbalance and power factor of loads connected to a switchgear, a motor control panel, a distribution panel, etc. using a power system. It relates to a system for compensating for degradation and the like.

In general, small factories, shopping malls, etc. receive three-phase power through distribution lines in order to use three-phase devices. Consumers use single-phase devices as well as three-phase devices, and when power is distributed to load facilities at the beginning, the three-phase devices are configured and operated so that they are balanced. .

This difference may cause a difference in reactive power and active power as well as a difference in voltage of each phase. Internally, the neutral point may be moved, which may affect power quality such as distortion of each phase.

The reactive power of each device, i.e., the power factor, can be improved through compensation with a reactive power compensator such as 'STATCOM'. Since the current imbalance between the three phases can be eliminated, power loss can be improved not only to the consumer but also to the supply side.

Since three-phase power is used in three or single phases on the load side, most of the currents in each phase are inevitably used unbalanced. Since the three-phase current differs according to the type of load and the operating state, in order to balance the three-phase current, there is no choice but to adjust the balance of the load in real time.

In general, for loads that use high power, a system for power balancing is applied, so the rate of rapid imbalance for power balance is low. However, for loads that use low power, the system is not applied. The current imbalance phenomenon appears conspicuously.

Registered Patent Publication No. 10-2484100 (registration date: December 29, 2022)

An embodiment of the present invention equalizes the power consumption of the three-phase system by equally controlling the unbalanced current applied to the three-phase load from the three-phase power system, and converts the unbalanced current into balanced regenerative power (active power and reactive power). A current imbalance resolution and power factor improvement system capable of stabilizing system power by improving power factor, efficiency, and distortion by re-supplying and supplying balanced three-phase power from the power supply side is provided.

A system for resolving current imbalance and improving power factor using regeneration of three-phase unbalanced load current according to an embodiment of the present invention includes a current sensor unit for measuring load current for each three-phase power line; a load current deficiency calculating unit for calculating a load current deficiency of another phase as a ratio based on a load current of one phase among the load currents; an undercurrent extractor for extracting power supplied to a load through a three-phase power line, extracting a load current deficiency of a phase having a current imbalance according to a switching operation performed for each of the three phases, and converting the extracted power into DC; A switching control signal is generated for each phase based on the load current shortfall ratio calculated through the load current shortfall calculation unit and the load current ratio set as a reference, and the three-phase current shortfall of the undercurrent extraction unit is generated using the switching control signal. an undercurrent regeneration control unit that controls switching operations for each unit; and a PFC inverter unit for converting the DC power converted through the undercurrent extraction unit into AC power and regenerating the converted AC power to a three-phase power line through three-phase distribution.

In addition, the load current deficiency calculation unit sets the load current of one phase having the maximum value within a predefined cycle among the load currents measured through the current sensor unit as the reference load current, and sets the load current of the other two phases as the reference load current. a load current setting unit that sets an unbalanced load current; and an undercurrent ratio calculating unit that calculates a load current shortfall ratio for each of the other two phases according to the following formula, wherein the formula is , wherein I _{dev _phase} (%) is the ratio of the load current deficiency for each of the other two phases, I _{ref _phase} is the value of the reference load current, and I _{rms _ref_phase} is within one predefined cycle. The reference load current may be a value calculated as RMS (Root Mean Square), and the I _{rms_phase} may be a value obtained by calculating the unbalanced load current as RMS (Root Mean Square) within a predefined cycle.

In addition, the load current deficiency calculation unit may apply the result data calculated through the undercurrent ratio calculation unit to a cycle immediately following the current cycle, based on a calculation starting point preset for each phase.

In addition, the undercurrent extraction unit may include a current input unit that receives current for each phase from the three-phase power line at the load side; a phase-by-phase undercurrent output amount control unit including a plurality of power semiconductor devices that receives currents for each of the three phases through the current input unit and outputs currents for each phase, respectively, and controls the amount of current output for each phase according to a switching operation; and a current output unit that converts the current output through the undercurrent output amount adjusting unit for each phase into DC, merges the converted DC current into one, and supplies the converted DC current to the PFC inverter unit.

In addition, the undercurrent regeneration control unit calculates the load current shortfall ratio (100%) calculated by the load current shortfall calculation unit for each phase and the load current ratio (I _{dev _phase} (%) < 100%) set as a standard. ), and a PI loop controller that generates PWM control signals for each phase by performing proportional integral control on the input value.

In addition, the undercurrent extraction unit can adjust the total load amount of system power supplied to the load of each phase by adjusting the switching-on time of each phase through the PWM control signal.

According to the present invention, by equally controlling the unbalanced current applied to the three-phase load from the three-phase power system, the three-phase system power consumption is equalized and the unbalanced current is re-supplied as balanced regenerative power (active power and reactive power). By doing so, it is possible to provide a current imbalance resolution and power factor improvement system capable of improving power factor, efficiency, and distortion factor, and stabilizing system power by supplying balanced three-phase power from the power supply side.

1 is a diagram showing the overall configuration of a three-phase current imbalance resolution and power factor improvement system according to an embodiment of the present invention.
2 is a block diagram showing the configuration of a load current shortfall calculation unit according to an embodiment of the present invention.
3 is a diagram illustrating three-phase waveforms including undercurrent according to an embodiment of the present invention.
FIG. 4 is a diagram for explaining a method of applying result data for a load current deficiency calculated in one cycle to the next cycle according to an embodiment of the present invention.
5 is a circuit diagram illustrating the configuration of an undercurrent extraction unit according to an embodiment of the present invention.
6 is a circuit diagram illustrating the configuration of an undercurrent regeneration control unit according to an embodiment of the present invention.
7 is a graph shown to explain the increase in energy efficiency and the improvement in power quality of a three-phase device through a reduction in reactive power consumption according to an embodiment of the present invention.
8 is a diagram showing a power factor in a general three-phase power load.
9 is a diagram illustrating a power factor improvement effect in a three-phase power load when a PFC inverter unit (STATCOM) according to an embodiment of the present invention is installed.
10 is a diagram illustrating phase imbalance, power factor, and efficiency improvement effects in a three-phase power load through a three-phase current imbalance resolution and power factor improvement system according to an embodiment of the present invention.

The terms used in this specification will be briefly described, and the present invention will be described in detail.

The terms used in the present invention have been selected from general terms that are currently widely used as much as possible while considering the functions in the present invention, but these may vary depending on the intention of a person skilled in the art or precedent, the emergence of new technologies, and the like. In addition, in a specific case, there is also a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the invention. Therefore, the term used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, not simply the name of the term.

When it is said that a certain part "includes" a certain component throughout the specification, it means that it may further include other components without excluding other components unless otherwise stated. In addition, terms such as "...unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software or a combination of hardware and software. .

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

1 is a diagram showing the overall configuration of a three-phase current imbalance resolution and power factor improvement system according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a load current shortfall calculation unit according to an embodiment of the present invention. 3 is a diagram illustrating three-phase waveforms including undercurrent according to an embodiment of the present invention, and FIG. 4 shows result data for the load current shortage calculated within one cycle according to an embodiment of the present invention in the next cycle. Figure 5 is a circuit diagram shown to explain the configuration of an undercurrent extraction unit according to an embodiment of the present invention, and Figure 6 is a diagram showing an undercurrent regeneration control unit according to an embodiment of the present invention. It is a circuit diagram shown to explain the configuration.

Referring to FIG. 1 , a three-phase current imbalance resolution and power factor improvement system 1000 according to an embodiment of the present invention includes a current sensor unit 100, a load current deficit calculation unit 200, an undercurrent extraction unit 300, At least one of the undercurrent regeneration control unit 400 and the PFC inverter unit 500 may be included.

The current sensor unit 100 is installed in a three-phase power line to measure AC load current for each of the three phases. A CT sensor (Current Transformer Sensor) can be applied as a means to measure AC load current for each phase. In this case, a CT sensor for measuring R-phase load current, a CT sensor for measuring S-phase load current, and a T-phase load A CT sensor for current measurement may be included, and data sensed by each CT sensor may be provided to the load current deficiency calculation unit 200 .

The load current deficiency calculation unit 200 may calculate the load current deficiency of another phase as a ratio based on the load current of one phase among the load currents.

To this end, the load current deficit calculator 200 may include at least one of a load current setter 210 and a load current ratio calculator 220 as shown in FIG. 2 .

The load current setting unit 210 is based on the load current of any one phase having the maximum value within one predefined cycle among the load currents (R, S, and T load currents) measured through the current sensor unit 100. It can be set as the load current, and the load current of the other two phases can be set as the unbalanced load current.

For example, when the R-phase load current Isr, S-phase load current Iss, and T-phase load current Ist are measured through the current sensor unit 100, respectively, as shown in FIG. 4, the R-phase When the load current (Isr) has the maximum value within one preset cycle, the R-phase load current (Isr) is set as the standard load current, and the S-phase load current (Iss) and T-phase load current (Ist) are the R-phase load current (Isr). Each can be set as an unbalanced load current based on the load current (Isr).

As shown in FIG. 4 , the load current ratio calculation unit 220 calculates a shortfall ratio for each unbalanced load current based on the reference load current. The calculation method may be performed according to the following formula.

[formula]

In the above formula, I _{dev _phase} (%) means the ratio of the load current deficiency for the other two phases (ex. S, T phase), I _{ref _phase} means the value of the reference load current (Isr), and I _{rms_ref_phase} means the value calculated by RMS (Root Mean Square) of the reference load current (Isr) within one predefined cycle, and I _{rms_phase} is the value calculated by RMS (Root Mean Square) of the unbalanced _load current within one predefined cycle. ) is the value calculated by

For example, if Idev_s(%) = I_r * (Irms_r - Irms_s) / Irms_r, if Irms_r = 100 and Irms_s = 80, Idev_s(%) = I_r * 0.2 = 20%. That is, if Irms_r = 100 and Irms_s = 80, a current shortfall corresponding to 20% should be extracted from the S-phase line.

Assuming I_sr to be the original steady current, the ratio of undercurrent to I_ss (Idev_s) is However, since the current angle (phase) varies according to the power factor, waveform distortion may occur when calculated in this way.

Accordingly, it is preferable to calculate the ratio of the shortfall of each phase using RMS (Root Mean Square) as described above, and it is preferable to prevent waveform distortion by calculating the undercurrent ratio using RMS current.

The reason why the RMS method is applied in this way is that, when calculating the current within each cycle having a time in units of μsec, the distortion factor and power factor of the power may be damaged and the quality of the power may be changed. Accordingly, the current within one cycle is calculated as the root mean square (RMS) (i.e., the RMS value for the undercurrent within one cycle is calculated), and the shortfall ratio for the unbalanced load current in one cycle unit is calculated using this value to determine the specific Since it is possible to exclude the phase value, it may not be affected by distortion or power factor.

Meanwhile, the load current shortfall calculator 200 applies the result data calculated through the undercurrent ratio calculator 220 to the cycle immediately following the current cycle, based on a preset calculation starting point for each phase. .

For example, as shown in FIG. 4, current shortage is checked in n cycle, the check result is applied to the next cycle, n+1 cycle, and the data checked in n+1 cycle is the next cycle, n. It can proceed by applying in +2 cycle.

In addition, in this embodiment, in order to maintain continuity when applied to the next cycle, it is possible to prevent the starting point of the current from being different by starting from the synchronization point for each phase. Here, the sync point means a point at which calculation for a specific phase starts, or a specific point based on 360 degrees. In addition, the sync point means synchronization between generators or a reference point for frequency detection of an inverter. do it too

In addition, in this embodiment, the 'S-Curve' type can be used to avoid linear addition and subtraction through soft increase and decrease. If there is a deviation between cycles, an increase or decrease may occur for the output of the result. At this time, a linear increase or decrease method that changes to a constant deceleration or acceleration is not applied at the time of output, but if there is an influence such as inertia during acceleration or deceleration, ' If the S-curve type acceleration/deceleration method is applied, the over-shoot can be reduced because the acceleration/deceleration can be adjusted more smoothly (by reducing the amount of acceleration/deceleration at the beginning and end).

The undercurrent extraction unit 300 extracts power supplied to a load through a three-phase power line, extracts a load current deficit of a phase having a current imbalance according to a switching operation performed for each three phases, and extracts the extracted power can be converted to DC.

To this end, the undercurrent extraction unit 300 may include at least one of a current input unit 310, a phase-by-phase undercurrent output amount adjusting unit 320, and a current output unit 330, as shown in FIG.

The current input unit 310 may receive currents Idr, Ids, and Idt for each phase (R, S, and T) from the three-phase power line on the load side.

The undercurrent output amount control unit 320 for each phase receives currents (Idr, Ids, and Idt) for each of the three phases through the current input unit 310 and outputs them as (R, S, and T) for each phase, and performs a switching operation. It may include a plurality of power semiconductor devices each controlling the amount of current output for each phase according to the above.

For example, the plurality of power semiconductor devices may include first to third power semiconductor devices 321 , 322 , and 323 . Here, the first power semiconductor element 321 is connected to the power line of phase R to receive the current supplied to the load of phase R, and the second power semiconductor element 322 is connected to the power line of phase S and supplied to the load of phase S. receiving current, and the third power semiconductor element 323 is connected to the power line of phase T and can receive current supplied to the load side of phase T. 'Triac' or 'IGBT' may be applied to the first to third power semiconductor devices 321, 322, and 323.

The current output unit 330 is connected to the output terminals of the first to third power semiconductor devices 321, 322, and 423, respectively, and receives the AC current output from the first to third power semiconductor devices 321, 322, and 323. The DC current may be converted into DC current, and the converted DC current may be joined into one and fed back to the PFC inverter unit 500.

As described above, the undercurrent extractor 300 serves to extract the current shortfall for each phase. For example, Idev_s(%) = I_r * (Irms_r - Irms_s) / Irms_r where Irms_r = 100, If Irms_s = 80, then Idev_s(%) = I_r * 0.2 = 20%. That is, if Irms_r = 100 and Irms_s = 80, a current shortfall corresponding to 20% should be extracted from the S-phase line.

That is, in order to extract a current shortfall corresponding to 20% from the S-phase power line, a load equivalent to 20% is required. control), it is possible to adjust the rectified amount of each of the R, S, and T phases when AC is rectified to DC. The rectified DC current for each phase is added to one place, and this summed DC current can act as a load for each phase in the grid (i.e. load R = 0, load S = 20, load T = 0). act as).

In this way, in order to extract the current shortfall corresponding to 20% from the S-phase line, a load corresponding to 20% is required. By adjusting the switching amount of each of the power semiconductor devices (Triac or IGBT), when AC power is rectified into DC power, inflow amounts for each of the R, S, and T phases can be adjusted. The DC current rectified for each phase is combined into one place, and this DC current acts as a load for each phase when viewed on the grid (for example, R load = 0, S load = 20, T load = 0). acts as a load). In this way, the undercurrent extraction unit 300 receives the PWM control signal (or switching control signal) generated by the undercurrent regeneration control unit 400 and, accordingly, the power semiconductor device (Triac or IGBT) provided for each phase. By adjusting the switching-on time, the amount of power supplied to the load for each phase can be adjusted.

The under current regeneration control unit 400 generates a switching control signal (PWM control signal) for each phase based on the load current shortfall ratio calculated through the load current shortfall calculation unit 200 and the load current ratio set as a standard. It is possible to adjust the rectification amount for each of the R, S, and T phases by generating and controlling the switching operation of the undercurrent extractor 300 using the generated switching control signal.

As shown in FIG. 6, the undercurrent regeneration control unit 400 calculates the load current shortfall ratio (I _{dev_phase} (%) < 100%) and It may include a PI loop controller that receives the ratio (100% Calculated) of the load current set as a reference and generates a PWM control signal for each phase by performing proportional integral control on the input value. .

Here, '100% Calculated' is the ratio (100%) of the maximum current consumed in each phase when the undercurrent is rectified for the load of each phase, and the same is applied to each phase (R/S/T).

The PWM control signal (PWM out) output from the PI loop controller is 'PWM out = K(E+ Edt)' can be calculated according to the formula. Here, K means total gain, but may mean P gain in some cases. E is an error value and is defined as 'Set point - Present value', and t has a value of 0 to infinite (Δ). If the 'Differential' term is inserted in the formula for calculating the PWM output according to the present embodiment, instability characteristics due to discontinuity appear, so it is preferable not to use the differential term.

In this embodiment, different currents can be supplied because three phases are connected to three PI loop controllers, respectively, unlike general inverters, and each phase is controlled differently. Assuming that there are three power sources, 'Pr, Ps, and Pt', to form DC power, and that there is a load 'Pdc' to consume these three power sources, 'Pr+Ps+Pt = Pdc' , and the consumption of DC power is determined by 'Pdc', and 'Pr, Ps, and Pt' can be controlled to make up for 'Pdc' insufficient due to current imbalance.

For example, if 'Pr, Ps, Pt' is made up of a general one-loop, the same power is supplied in a balanced way to each, but if the same amount of power is supplied to each loop for different times, , the amount of power finally supplied is inevitably different. Therefore, during rectification through the undercurrent extractor 300, the rectification time in µsec units is adjusted using the 'Triac' or 'IGBT' of the undercurrent extractor 300 to adjust the amount of power supplied to each phase. The load (viewed from the grid) can be balanced (however, if the Pdc is not consumed, the control amount will inevitably be zero).

The PFC inverter unit (Power Factor Control Invertor) 500 includes an inverter having both a STATCOM (Static Compensator) and a power factor control function, and through this configuration, the DC power converted through the undercurrent extractor is converted to AC power , and through the three-phase equal distribution of the converted AC power, equivalent AC current can be supplied to the three-phase power line. That is, the DC current converted through the rectifier (AD-DC Converter) of the current output unit 300 is equally distributed to each phase using the 3-phase power semiconductor device (ex. Triac or IGBT) of the PFC inverter unit 500. The current imbalance of the three-phase power line can be solved by distribution regeneration.

7 is a graph showing energy efficiency and power quality improvement of a three-phase device through a reduction in reactive power consumption according to an embodiment of the present invention, and FIG. 8 is a diagram showing the power factor in a general three-phase power load. 9 is a diagram showing the power factor improvement effect in a three-phase power load when a PFC inverter unit (STATCOM) is installed according to an embodiment of the present invention, and FIG. 10 is a three-phase current imbalance solution according to an embodiment of the present invention. and a diagram showing phase imbalance, power factor, and efficiency improvement effects in a three-phase power load through a power factor correction system.

According to the calculation result (PWM out) of the undercurrent regeneration control unit 400 according to the present embodiment, the power factor control of the PFC inverter unit 500 controls the extracted energy, that is, as shown in FIG. 7, 'Edc = k * ( By generating active power and reactive power by Vdc - Vset and applying them to the system line, as a result, consumption of reactive power can be reduced, thereby increasing energy efficiency and contributing to the improvement of power quality. In addition, it is possible to compensate for the reactive power of the system power by measuring the amount of phase imbalance of the system load power, extracting an amount of power capable of resolving the phase imbalance of the system load power, and using the regenerative power.

8 to 10 are diagrams showing power factor improvement and efficiency improvement in a three-phase power load. At this time, the power used at this time regenerates the amount of current imbalance in the three-phase power load and uses it as power factor improvement and efficiency improvement to improve phase imbalance, power factor Improvements and efficiency improvements are possible.

What has been described above is only one embodiment for implementing a current imbalance resolution and power factor improvement system using regeneration of three-phase unbalanced load current according to the present invention, and the present invention is not limited to the above embodiment, and the following patents As claimed in the claims, anyone skilled in the art without departing from the gist of the present invention will say that the technical spirit of the present invention exists to the extent that various changes can be made.

1000: 3-phase current imbalance cancellation and power factor correction system
100: current sensor unit
200: load current shortfall calculation unit
210: load current setting unit
220: undercurrent ratio calculation unit
300: undercurrent extraction unit
310: current input unit
320: Undercurrent output amount control unit for each phase
321: first power semiconductor device
322: second power semiconductor device
323: third power semiconductor device
330: current output unit
400: undercurrent regeneration control unit
500: PFC inverter unit

Claims (6)

a current sensor unit for measuring load current for each of the three-phase power lines;
a load current deficiency calculating unit for calculating a load current deficiency of another phase as a ratio based on a load current of one phase among the load currents;
an undercurrent extractor for extracting power supplied to a load through a three-phase power line, extracting a load current deficiency of a phase having a current imbalance according to a switching operation performed for each of the three phases, and converting the extracted power into DC;
A switching control signal is generated for each phase based on the load current shortfall ratio calculated through the load current shortfall calculation unit and the load current ratio set as a reference, and the three-phase current shortfall of the undercurrent extraction unit is generated using the switching control signal. an undercurrent regeneration control unit that controls switching operations for each unit; and
A PFC inverter unit converting the DC power converted through the undercurrent extractor into AC power and regenerating the converted AC power to a three-phase power line through three-phase distribution;
The load current shortfall calculation unit,
Load current setting to set the load current of one phase having the maximum value within a predefined cycle among the load currents measured through the current sensor unit as the reference load current, and setting the load currents of the other two phases as the unbalanced load current. wealth; and
An undercurrent ratio calculation unit that calculates a load current shortfall ratio for each of the other two phases according to the following formula;
The above formula is , wherein I _{dev_phase} (%) is the ratio of the load current deficiency for each of the other two phases, I _{ref_phase} is the value of the reference load current, and I _{rms_ref_phase} is the reference load within one predefined cycle. A value obtained by calculating the current as RMS (Root Mean Square), and the I _{rms_phase} is a value obtained by calculating the unbalanced load current as RMS (Root Mean Square) within a predefined cycle. Current imbalance resolution and power factor correction system using regeneration.
delete According to claim 1,
The load current shortfall calculation unit,
Resolving current imbalance using regeneration of three-phase unbalanced load current, characterized in that the result data calculated through the undercurrent ratio calculator is applied to the cycle immediately following the current cycle, based on the calculation starting point preset for each phase, and Power factor correction system.
According to claim 1,
The undercurrent extraction unit,
a current input unit that receives current for each phase from the load-side three-phase power line;
a phase-by-phase undercurrent output amount control unit including a plurality of power semiconductor devices that receives currents for each of the three phases through the current input unit and outputs currents for each phase, respectively, and controls the amount of current output for each phase according to a switching operation; and
A current using regeneration of three-phase unbalanced load current comprising a current output unit that converts the current output through the phase-specific undercurrent output amount control unit into DC, joins the converted DC current, and supplies the converted DC current to the PFC inverter unit. Imbalance resolution and power factor correction system.
According to claim 1,
The undercurrent regeneration control unit,
For each phase, the load current shortfall ratio (100%) calculated through the load current shortfall calculation unit and the load current ratio (I _{dev _phase} (%) < 100%) set as a standard are input, and the input value A current imbalance resolution and power factor improvement system using regeneration of three-phase unbalanced load current, characterized in that it includes a PI loop controller for generating a PWM control signal for each phase by performing proportional integral control for each phase.
According to claim 5,
The undercurrent extraction unit,
Current imbalance resolution and power factor improvement system using regeneration of three-phase unbalanced load current, characterized in that the switching on time of each phase is adjusted through the PWM control signal to adjust the total load amount of system power supplied to the load of each phase. .