KR102378390B1 - 3-Phase 4-wire grid-connected power conditioning system with active/reactive power control of each phase individually based on the 4-leg hardware - Google Patents

Abstract

Disclosed is a 3-phase 4-wire grid-connected power conditioning system (PCS) capable of individually controlling active/reactive power of each phase based on 4-leg to supply stable power within a specified voltage range. According to a preferred embodiment of the present invention, the PCS comprises: an inverting unit formed of a 3-phase 4-wire 4-leg inverter, housing one end connected to an energy storage device and having the other end connected to commercial power and a load to receive power supplied by the commercial power, thereby charging the energy storage device or discharging and supplying power stored in the energy storage device to the load; and a controller receiving an active power reference value and an reactive power reference value for each phase from an energy management system or receiving a power factor command value for each phase from the energy management system to generate an active power reference value and reactive power reference value for each phase, and controlling on/off of switching elements included in the inverting unit according to a voltage value of each phase supplied by commercial power, a current value of each phase output by the inverting unit, the active power reference value, and the reactive power reference value, thereby independently controlling charging and discharging of the energy storage device and active power and reactive power for each phase of three phases.

Description

3-Phase 4-wire grid-connected power conditioning system with active/reactive power control of each phase individually based on the 4 -leg hardware}

The present invention relates to a power conversion device (PCS: Power Conditioning System), and more specifically, an ESS function and an active/reactive power compensation function for load imbalance in a 3-phase 4-wire low voltage consumer power system or an internal combustion power generation system in an island area It relates to a three-phase, four-wire power converter connected to a storage battery that simultaneously performs

In the configuration of an independent hybrid power system for a remote location using a renewable energy power source such as solar power generation and wind power generation and an energy storage device such as a storage battery, the prior art is for the purpose of absorbing surplus power and discharging insufficient power, And in order to achieve at least one of the objectives of solving the problem of load imbalance between phases of the three-phase power source, a three-phase power system was constructed using three 1-phase photovoltaic inverters and three 1-phase storage battery inverters each. .

For the control method of this three-phase power system, the frequency-active power droop method and the voltage-reactive power droop method were applied to the inverter for storage batteries, which means that when the power frequency increases than the rated frequency, the active power is set at a set ratio (droop). ratio), and control was performed by increasing the active power output when the power frequency decreased than the rated frequency, and this droop method was also applied to voltage and reactive power.

In addition, when the energy storage device is fully charged because the amount of each generation is sufficient and the load remains after consuming power, the output of solar power generation or wind power generation should be limited. was controlled to decrease.

An example of the stand-alone microgrid configuration according to the prior art is shown in FIG. 1 . Referring to FIG. 1 , a three-phase power source 6 is configured using three sets consisting of a solar cell 1 and a one-phase inverter 2 for photovoltaic power generation, and the surplus power is charged or insufficient power is used. To discharge the battery, three sets consisting of a storage battery (3) and a 1-phase inverter (4) for storage batteries are added to configure the entire power grid.

In the prior art, the three-phase power grid 6 is configured in this way to supply power to a one-phase or three-phase load 5, and each inverter 2, 4 is independently configured for each phase by the above-described droop method. The voltage and frequency of each phase are maintained while charging, discharging, or output-limiting operation.

This prior art has the advantage that it does not require control through a separate high-speed communication network, but by applying the droop method, the quality of voltage and frequency is sacrificed. The disadvantage is that the installation cost increases.

As a method of supplementing the problems of the prior art shown in FIG. 1 , there is a method using a three-phase, four-wire inverter 100 shown in FIGS. 2 and 3 . The inverting unit 40 of this inverter 100 operating in a grid-connected type consists of two power switches, that is, eight switches, and each phase is a three-phase four-wire power supply ( 50) is connected.

The sensing circuit unit 20 measures the current of the inverting unit 40 , the voltage of the system power supply 50 , and the current 70 of the load 60 . The control circuit unit 10 performs a necessary control operation from the measurement information of the sensing circuit unit 20 and outputs the result to the driving circuit unit 30 to control the power semiconductor switch of the inverting unit 40 . Such a conventional three-phase four-wire inverter can compensate for the current imbalance of the load 60 or be used as an active filter.

In general, the dq control technique of the rotation synchronous coordinate system is applied to the voltage or current control of a 3-phase 3-LEG inverter. For an unbalanced voltage or current, the voltage or current is individually controlled by separating the normal component and the negative phase component, and then it is compensated by synthesizing them again and switching them.

This problem is partially solved by using a PI controller based on a synchronously rotating reference frame dqo transformation, dividing the positive and negative phase components in the unbalanced current, installing an individual current controller for each component, and then synthesizing the results. can overcome However, this method based on a three-phase 3-LEG inverter has a fundamental problem because the voltage of the neutral line cannot be controlled.

In addition, when a 3-phase 4-wire power supply is used in the consumer, a load imbalance situation occurs due to the use of a 1-phase load, which causes a voltage imbalance phenomenon in which the balance of the 3-phase voltage is broken. It gets worse as the reactive power of In other words, in the case of using an unbalanced load for each phase within a consumer using a 3-phase 4-wire type power source, as in the prior art, if the magnitude of the current is balanced by controlling only the active power for each phase as in the prior art, it is still There is a possibility that a voltage deviation may occur.

4 is a case in which the receiving voltage imbalance occurs due to the inequality of the active power of the receiving point caused by the 1-phase unbalanced load in the low voltage consumer power system such as an apartment complex in the city, or the generator operation in an independent microgrid such as a small island It shows the situation in which the output voltage of the 3-phase generator becomes unbalanced due to the load active/reactive power imbalance due to the village load composed of the city and 1-phase unbalanced loads.

In order to solve the above-mentioned unbalanced voltage problem in the above situation, a three-phase 4-LEG type power conversion device (PCS) as shown in FIG. 3 has been proposed, but currently a three-phase 4-LEG type power conversion device ( The PCS control algorithm that can stably operate a three-phase power system by individually controlling active/reactive power for each phase using PCS) is insufficient.

The present invention is to solve the above-mentioned problems of the prior art, as a power conversion device (PCS) linked to a storage battery, including a 3-phase 4-wire 4-leg inverter, valid / invalid by one-phase load in the grid-connected operation mode An object of the present invention is to provide a power converter capable of supplying stable power within a specified voltage range by resolving the complex load imbalance of power and the resulting phase-to-phase voltage imbalance.

A power conversion device according to a preferred embodiment of the present invention for solving the above problems is composed of a three-phase, four-wire, four-leg inverter, one end is connected to the energy storage device, the other end is connected to commercial power and a load, an inverting unit receiving power supplied from commercial power to charge the energy storage device or discharging power stored in the energy storage device to provide a load; and receiving an active power reference value and reactive power reference value for each phase from the energy management system, or receiving a power factor command value for each phase from the energy management system to generate an active power reference value and reactive power reference value for each phase, and each phase supplied by commercial power By controlling the on/off of switching elements included in the inverting unit according to a voltage value, a current value of each phase output by the inverting unit, and the active power reference value and the reactive power reference value, the energy for each phase of three phases It includes a controller for independently controlling the charging and discharging of the storage device, and active power and reactive power.

In addition, the controller may include: a phase information generator configured to generate phase information θ_ut synchronized with commercial power using voltage values (Van, Vbn, Vcn) of each phase of the commercial power; Active power compensation standard for receiving the voltage values (Van, Vbn, Vcn) of the first phase, the second phase, and the third phase, the active power reference value for each phase, and the phase information (θ_ut), respectively, and controlling the active power for each phase an active power control module for outputting current signals (Va_d*, Vb_d*, Vc_d*); Reactive power compensation standard for receiving the current values (Ian, Ibn, Icn) of the first phase, the second phase and the third phase, the reactive power reference value for each phase, and the phase information (θ_ut), respectively, and controlling the reactive power for each phase a reactive power control module for outputting current signals (Va_q*, Vb_q*, Vc_q*); Receive the active power reference value and reactive power reference value for each phase from the energy management system, or receive the power factor command value for each phase from the energy management system to generate an active power reference value and reactive power reference value for each phase, the active power control module and the reactive power a reference value generator outputting each of the power control modules; And according to the active power compensation reference current signal and the reactive power compensation reference current signal, by generating a switching control signal (Sa, Sb, Sc, Sn) for controlling the on / off of the switches included in the inverting unit, It may include a control signal converting unit output to the inverting unit.

In addition, the active power control module includes a first phase active power control unit, a second phase active power control unit, and a third phase active power control unit, the first phase active power control unit, the second phase active power control unit and the Each of the third-phase active power control units receives the output voltage (Van, Vbn, Vcn) of the corresponding phase of the commercial power source, and outputs α, β components (Va_αβ, Vb_αβ, Vc_αβ) of the phase voltage delayed by 90 degrees an all-pass filter; The α,β component (Va_αβ, Vb_αβ, Vc_αβ) of the corresponding phase voltage is received from the all-pass filter, the phase information (θ_ut) is received, and the d-axis and q-axis voltage components (Va_d) are performed by performing rotation-synchronous coordinate system transformation. ,Vb_d,Vc_d,Va_q,Vb_q,Vc_q) a rotation synchronization coordinate system transforming unit that outputs; The d-axis and q-axis voltage components (Va_d, Vb_d, Vc_d, Va_q, Vb_q, Vc_q) and the corresponding phase d-axis and q-axis current components (Ia_d, Ib_d, Ic_d, Ia_q, Ib_q) input from the reactive power control module ,Ic_q) using the active power calculator to output the active power values (Pa, Pb, Pc) of the corresponding phase; Active power control for receiving an error value between the active power values of the corresponding phase (Pa, Pb, Pc) and the active power reference values (Pa_ref, Pb_ref, Pc_ref) input from the reference value generator, and controlling the input error value to decrease an active power controller for outputting signals (Ia_d*, Ib_d*, Ic_d*); and an error between the output active power control signals (Ia_d*, Ib_d*, Ic_d*) of the corresponding phase and the d-axis current component (Ia_d, Ib_d, Ic_d) of the corresponding phase input from the reactive power control module, and input It may include a d-current controller that generates and outputs the active power compensation reference current signals Va_d*, Vb_d*, Vc_d* of the corresponding phase to control the error to be reduced.

In addition, the reactive power control module includes a first phase reactive power control unit, a second phase reactive power control unit and a third phase reactive power control unit, the first phase reactive power control unit, the second phase reactive power control unit and the Each of the third phase reactive power control units receives the output current (Ian, Ibn, Icn) of the corresponding phase of the inverting unit, and outputs α, β components (Ia_αβ, Ib_αβ, Ic_αβ) of the phase current delayed by 90 degrees an all-pass filter; Receives α and β components (Ia_αβ, Ib_αβ, Ic_αβ) of the corresponding phase current from the all-pass filter, receives the phase information, performs rotation synchronous coordinate system transformation, and performs d-axis and q-axis current components (Ia_d, Ib_d, Ic_d, Ia_q, Ib_q, Ic_q) to output a rotation synchronization coordinate system transformation unit; The d-axis and q-axis current components (Ia_d, Ib_d, Ic_d, Ia_q, Ib_q, Ic_q) and corresponding phase d-axis and q-axis voltage components (Va_d, Vb_d, Vc_d, Va_q, Vb_q) input from the active power control module , Vc_q) using a reactive power calculator to output the reactive power values (Qa, Qb, Qc) of the corresponding phase; Reactive power control to receive the error value between the reactive power value (Qa, Qb, Qc) of the corresponding phase and the reactive power reference value (Qa_ref, Qb_ref, Qc_ref) input from the reference value generator, and to control the input error value to decrease a reactive power controller for outputting signals (Ia_q*, Ib_q*, Ic_q*); And receiving an error between the output reactive power control signal (Ia_q*, Ib_q*, Ic_q*) of the corresponding phase and the q-axis current component (Ia_q, Ib_q, Ic_q) of the corresponding phase, and controlling the input error to decrease It may include a q-current controller that generates and outputs the reactive power compensation reference current signals Va_q*, Vb_q*, Vc_q* of the corresponding phase.

In addition, the phase information generator, a rotation synchronous coordinate system conversion unit that receives the voltage values (Van, Vbn, Vcn) of each phase of the commercial power and the phase information, performs rotation synchronous coordinate system transformation, and outputs a d-axis voltage (V_de) ; and a phase lock loop that receives the d-axis voltage V_de from the rotation synchronization coordinate system converter and generates phase information θ_ut synchronized with commercial power.

In addition, with respect to the active power compensation reference current signal (Va_d*, Vb_d*, Vc_d*) and the reactive power compensation reference current signal (Va_q*, Vb_q*, Vc_q*) using the phase information (θ_ut), inverse Further comprising an inverse transform unit for sequentially performing dq transform and inverse α-β transform to generate α components (Va_α, Vb_α, Vc_α) of a three-phase signal and output it to the control signal converter, wherein the control signal converter includes the inverse transform The α component of the three-phase signal input from the unit may be converted into switching control signals (Sa, Sb, Sc, Sn) of each switch included in the inverting unit and output.

The power conversion device according to a preferred embodiment of the present invention adopts a structure having four LEGs by adding a neutral LEG for controlling a neutral point to a general 3-LEG structure, thereby a conventional single-phase dq control method based on 4-LEG hardware By combining , the output power of each phase can be independently individually controlled to solve the problems of the prior art and to stably control the unbalanced load response operation.

In addition, since the three-phase 4-LEG power conversion device (PCS) according to the preferred embodiment of the present invention operates the same as the topology of the three single-phase power conversion devices (PCS), the control method of the single-phase power conversion device (PCS) is reduced. Adopted, through this, the 4-LEG power conversion device (PCS) of the present invention can independently control the current or voltage of each phase.

In addition, since the general grid-connected mode operation to which the rotation synchronous coordinate system is applied, that is, the d-q control is a technique applied to the three-phase balanced current and power control, the compensation function for the unbalanced load cannot be performed. In order to compensate or output the unbalanced current, a separate controller that separates and controls the reverse phase is required, and finally, the outputs of the positive phase current controller and the negative phase current controller are summed and controlled. As such, the conventional general dq control algorithm has no choice but to control the power of three phases at once, so it was impossible to control the size of each phase differently during charge/discharge operation and to control the charge/discharge mode for each phase differently, but the present invention The power conversion device according to a preferred embodiment of , adopts a 4-leg type structure, and can perform dq control for each individual phase so that active/reactive power of each phase can be differently controlled.

In addition, as shown in FIG. 5, the prior art had no choice but to control the size of three-phase power at once during the charging/discharging operation, but the present invention provides not only the size of each phase active power, but also each phase during the charging/discharging operation. The size of reactive power can also be controlled, and the charging/discharging mode can be controlled differently for each phase. By using this technology to individually control the active and reactive power of each phase, the power and power factor of each phase can be individually controlled at the receiving point of the power supply system composed of many single-phase loads, such as power plants or apartment complexes in island areas. there appears to be an effect.

1 is a diagram showing an example of a stand-alone three-phase micro-grid configuration according to the prior art.
FIG. 2 is a diagram illustrating the configuration of a three-phase, four-wire inverter for improving the problems of the prior art shown in FIG. 1 .
FIG. 3 is a view showing the internal configuration of a three-phase, four-wire inverter of a three-phase 4-LEG method to supplement the prior art shown in FIG. 1. Referring to FIG.
4 is a case in which the receiving voltage unbalance phenomenon occurs due to the inequality of the active and reactive power of the receiving point caused by the 1-phase unbalanced load in the low voltage consumer power system such as an apartment complex in the city, or a generator in an independent microgrid such as a small island It is a diagram showing the operation situation in which the output voltage of the 3-phase generator becomes unbalanced due to load active/reactive power imbalance due to the village load composed of 1-phase unbalanced load during operation.
5 is a diagram comparing the dq control method of the prior art for collectively controlling the power of each phase and the respective phase control method for controlling the active power and the reactive power for each phase according to the present invention.
6 is a diagram showing the overall configuration of a 3-phase 4-wire 4-LEG power conversion device according to a preferred embodiment of the present invention.
7A and 7B are block diagrams showing a detailed configuration of a controller included in a 3-phase 4-wire 4-LEG power conversion device according to a preferred embodiment of the present invention.
8 is a diagram illustrating a configuration example of an independent micro-grid power system to which a 3-phase 4-wire 4-LEG power conversion device according to a preferred embodiment of the present invention is applied.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

6 is a diagram showing the overall configuration of a 3-phase 4-wire 4-LEG power conversion device according to a preferred embodiment of the present invention.

Referring to FIG. 6 , a three-phase, four-wire, four-legged power conversion device 1000 according to a preferred embodiment of the present invention is connected to an energy storage device such as a storage battery, and an inverting unit connected to the DC terminal 110 ( 130), the filter units 150 and 160 disposed at the output of the inverting unit 130, and disposed between the inverting unit 130 and the filter units 150 and 160, the current 140 of each phase output from the inverting unit 130 ), a voltage measuring unit (not shown) installed on the side of the commercial power supply 220 to measure the voltage 200 of each phase of the commercial power supply 220 (not shown) and the controller 270 is comprised of

The controller 270 receives the output current values (Ian, Ibn, Icn) 140 of each phase output from the inverting unit 130 from the current measuring unit (not shown), and receiving the voltage measuring unit (not shown) It receives the voltage values (Van, Vbn, Vcn) 200 of each phase output by the commercial power supply 220 from, and receives the active power reference value and the reactive power reference value, or the power factor command value from the energy management system 613 . In addition, the controller 270 generates a control signal (PWM signal) for controlling on/off of the plurality of switches included in the inverting unit 130 using the input values and outputs the generated control signal (PWM signal) to the inverting unit 130 . .

In the 3-phase 4-wire 4-leg power conversion device 1000 according to the preferred embodiment of the present invention, a capacitor bank is connected to the DC terminal 110, or a structure in which a storage battery or a step-down converter for storage batteries is combined may be connected. , a storage battery connected to the DC terminal 110 must be applied with a DC voltage of sufficient magnitude for grid-connected operation or stand-alone operation, and must be capable of emitting or absorbing power.

The inverting unit 130 of the present invention is composed of 4 legs by adding an arm 130b for a neutral point to a general three-phase inverter 130a composed of three legs. By implementing the inverting unit 130 as a three-phase, four-wire, four-leg type in this way, it is possible to solve the problem of unbalance of voltages between phases by individually controlling the active and reactive power of each phase to maintain the balance of power at the power receiving point.

Filter units 150 and 160 composed of a reactor 150 and a capacitor 160 are installed at the output end of the inverting unit 130 .

A current measuring unit (not shown) installed between the inverting unit 130 and the filter units 150 and 160 measures the output currents (Ian, Ibn, Icn) 140 of each phase output by the inverting unit 130, output to the controller 270 . A voltage measuring unit (not shown) measures the voltages (Van, Vbn, Vcn) 200 of each phase of the commercial power supply 220 and outputs it to the controller 270 (see 260 in FIG. 6 ).

In addition, in order to supply power from the inverting unit 130 to the load 250 in parallel to the path for supplying power from the commercial power source 220 to the load 250 , the output lines of the filter units 150 and 160 are commercial power sources. (220)/load 250 side.

The controller 270 receives the active power reference value and the reactive power reference value, or the power factor command value received from the energy management system (see 613 in FIG. 8 ), and the output current value 140 of the inverting unit 130 and commercial power It receives the voltage value 200 of 220 and performs grid-connected operation or current control through internal operation, and outputs a switching control signal (PWM control signal) 280 to the inverting unit 130 to the inverting unit 130 . (130) Controls the switching of the switches included therein.

In a preferred embodiment of the present invention, the commercial power 220 may be a power provided by a general power supply organization, or may be a power produced using a diesel generator.

7A and 7B are block diagrams showing the detailed configuration of a controller included in a 3-phase 4-wire 4-LEG power converter according to a preferred embodiment of the present invention.

7A and 7B , the controller 270 according to the preferred embodiment of the present invention operates in the grid-connected operation mode to individually control the current of each phase output from the inverting unit 130 .

The controller 270 includes an active power control module 271 , a reactive power control module 272 , a phase information generation unit 273 , an inverse transformation unit 509 , a control signal conversion unit 506 , and a reference value generation unit 274 . includes

The active power control module 271 includes a first phase active power control unit 301,303,305,308,310, a second phase active power control unit 321,323,325,328,330, and a third phase active power control unit 341,343,345,348,350, the first phase active power control unit, the Each of the second-phase active power control unit and the third-phase active power control unit includes an all-pass filter (301,321,341), a rotation synchronization coordinate system conversion unit (303,323,343), an active power calculator (305,325,345), an active power controller (308, 328, 348), and d-current controllers 310 , 330 , 350 .

The reactive power control module 272 includes a first phase reactive power control unit 401,403,405,408,410, a second phase reactive power control unit 421,423,425,428,430 and a third phase reactive power control unit 441,443,445,448,450, the first phase reactive power control unit, the Each of the second-phase reactive power control unit and the third-phase reactive power control unit is an all-pass filter (401, 421, 441), a rotation synchronization coordinate system conversion unit (403, 423, 443), a reactive power calculator (405, 425, 445) , reactive power controllers 408 , 428 , 448 , and q-current controllers 410 , 430 , 450 .

The phase information generator 273 includes a rotation synchronization coordinate system converter 501 and a phase locked loop (PLL) 503 .

The controller 270 operates when a charging current is introduced into an energy storage device such as a storage battery when the commercial power supply 220 operates normally, or when the energy storage device is discharged from the energy storage device to the load 250 .

In order to control the current, phase synchronization with the commercial power supply 220 is required, and for this, a phase locked loop 503 is used. The voltage values (Van, Vbn, Vcn) 500 of each phase of the commercial power source 220 measured by the voltage measuring unit (not shown) are input to the rotation synchronous coordinate system conversion unit 501, and the phase locked loop 503 generates phase information (θ_ut) 504 synchronized with the commercial power supply 220 using the d-axis voltage (V_de) 502 that is the output of the rotation synchronization coordinate system conversion unit 501, and the rotation synchronization coordinate system conversion units 501,303,323,343,403,423,443 ) and output to the inverse transform unit 509 .

Then, the rotation synchronous coordinate system conversion unit 501 performs rotation synchronous coordinate system transformation using the voltage values (Van, Vbn, Vcn) 500 and the phase information (θ_ut) 504 of each phase of the commercial power supply 220 , The d-axis voltage (V_de) 502 is output to the phase locked loop 503 .

At this time, each phase voltage (Van, Vbn, Vcn) of the commercial power supply 220 (Van, Vbn, Vcn) (300, 320, 340) and the phase lock loop, the rotation synchronous coordinate system conversion unit (303, 323, 343) corresponding to each phase voltage included in the active power control module 271 The d-axis and q-axis voltages 304, 324, and 344 are respectively output by using the phase information (θ_ut) 504 that is the output of (503).

In addition, the rotation synchronous coordinate system conversion unit 403,423,443 corresponding to each phase current, included in the reactive power control module 272, each phase current (Ian, Ibn, Icn) (400, 420, 440) of the inverter output and the phase lock loop 503 The d-axis and q-axis currents 404, 424, and 444 are output using the output phase information θ_ut 504, respectively.

좌표계-정지좌표계(αβ)-동기좌표계(dq)로의 변환과정을 거쳐야 한다. Meanwhile, in order to apply the dq control used in the three-phase control to the single-phase control, the present invention applies an APF (All Pass Filter) technique as an all-pass filter as follows. That is, the three-phase voltage and current signals on the AC input side are required for digital control.

Coordinate system-stationary coordinate system (αβ)-synchronized coordinate system (dq) must be converted.

-αβ 컨버터를 사용할 수 없다. 여기서, 정지좌표계는 2상 α-β로 구성되며, 이 α-β는 서로 90ㅀ 위상차인 점을 이용해 정지좌표계로의 변환을 위해 a상 신호와 크기는 같고 위상만 90ㅀ 뒤지는 가상의 파형을 생성한 후 αβ-dq 컨버터의 입력에 인가시킨다. 즉, 기준신호와 크기는 같고 위상만 90ㅀ 뒤지는 가상의 신호를 만드는 전역통과필터를 사용하여 단상제어 d-q변환에 적용하였다. However, since the voltage and current signal input is single-phase in each phase individual control method,

-The αβ converter cannot be used. Here, the stationary coordinate system is composed of two-phase α-β, and this α-β uses a point that is 90° out of phase with each other to generate a virtual waveform that has the same magnitude as the a-phase signal and lags 90° in phase for conversion to the stationary coordinate system. After generation, it is applied to the input of the αβ-dq converter. That is, an all-pass filter that creates a virtual signal that has the same magnitude as the reference signal and lags behind by 90° was used for single-phase control dq transformation.

성분이 되며, 위상정보를 이용하여 회전동기좌표계 dqo로 변환할 수 있다. 이와 같이, 단상도 3상처럼 직류성분으로 전압 혹은 전류제어기의 적용이 가능해지는 장점이 있다. Here, the all-pass filter is a filter that has a gain of 1 and a phase delay of 90 degrees, and is usually used in a current or voltage controller using dqo conversion when controlling a single-phase grid-connected inverter. That is, if a single-phase voltage or current is input to the all-pass filter, an output delayed by 90 degrees can be obtained, which is

It becomes a component and can be converted into a rotation synchronization coordinate system dqo using phase information. In this way, there is an advantage that a voltage or current controller can be applied as a DC component like a single-phase three-phase.

성분(Va_αβ,Vb_αβ,Vc_αβ)(302, 322, 342)이 회전동기좌표계 변환부(303, 323, 343)로 입력된다. As described above, when the voltage values 300, 320, and 340 of each phase measured by the voltage measuring unit (not shown) are input to the all-pass filters 301, 321, 341, each signal whose phase is delayed by 90 degrees can be obtained. and, from this, the voltage of each phase

Components (Va_αβ, Vb_αβ, Vc_αβ) 302 , 322 , 342 are input to the rotation synchronization coordinate system conversion units 303 , 323 , 343 .

The rotation synchronous coordinate system converters 303 , 323 , and 343 of each phase voltage perform dq transformation using the phase angle θ_ut 504 , thereby calculating the d-axis and q-axis components for each phase voltage, and each phase q-axis voltage components (Va_q, Vb_q, Vc_q) representing the voltage peak value of

성분(Ia_αβ,Ib_αβ,Ic_αβ)(402, 422, 442)이 회전동기좌표계 변환부(403, 423, 443)로 입력된다.On the other hand, when the output current values 400 , 420 , 440 of each phase output from the inverting unit 130 and measured by the inverter output current measuring unit (not shown) are input to the all-pass filters 401 , 421 , 441 , Each signal with a phase delay of 90 degrees can be obtained, from which the

Components (Ia_αβ, Ib_αβ, Ic_αβ) 402 , 422 , 442 are input to the rotation synchronization coordinate system conversion units 403 , 423 , 443 .

The rotation synchronous coordinate system conversion units 403,423 and 443 of each phase current perform dq transformation using the phase angle θ_ut 504 to calculate the d-axis, q-axis, and o-axis components for each phase current, and The q-axis current components (Ia_q, Ib_q, Ic_q) representing the current peak values and the d-axis current components (Ia_d, Ib_d, Ic_d) (404, 424, 444) representing the components lagged by 90 degrees are output.

The q-axis components and d-axis components (304, 324, 344), which are the DC components of the peak output voltage of each phase, and the q-axis components and the d-axis components (404, 424, 444), which are the DC components of the output current peak value, are the active power calculators, respectively. (305,325,345) and the reactive power calculator (405,425,445), the active power calculator (305,325,345) and the reactive power calculator (405,425,445) are active power detection amount (Pa, Pb, Pc) (306, 326, 346) and reactive power detection amount, respectively (Qa, Qb, Qc) (406, 426, 446) is generated and output.

Active power detection amounts (Pa, Pb, Pc) (306, 326, 346) and reactive power detection amounts (Qa, Qb, Qc) (406, 426, 446) are the active power reference values (Pa_ref, After comparing with Pb_ref, Pc_ref) (307, 327, 347) and reactive power reference values (Qa_ref, Qb_ref, Qc_ref) (407, 427, 447) of each phase, respectively, the error value is determined by the active power controllers 308, 328, 348) and the reactive power controllers 408, 428 and 448 of each phase, and the roles of each controller are as follows.

Active power controllers 308, 328, 348 of each phase using a proportional integral (PI) controller inside the active power detection amount (Pa, Pb, Pc) (306, 326, 346) and active power calculated for each phase An active power control signal that receives an error between the reference values (Pa_ref, Pb_ref, Pc_ref) (307, 327, 347) and controls the active power detection amount of each phase to match the active power reference value, that is, to reduce the input error (Ia_d*, Ib_d*, Ic_d*) (309, 329, 349) are generated and respectively output.

Reactive power controllers (408, 428, 448) of each phase using a proportional integral (PI) controller inside the reactive power detection amount (Qa, Qb, Qc) (406, 426, 446) calculated for each phase (406, 426, 446) and reactive power reference value (Qa_ref, Reactive power control signals (Ia_q*, Ib_q*, Ic_q*) (409, 429, 449) is generated and outputted, respectively.

The d-current controllers 310, 330, and 350 of each phase have active power control signals (Ia_d*, Ib_d*, Ic_d*) (309, 329, 349) calculated for each phase using a proportional integral (PI) controller inside and the actual output current detection amount ( Ia_d, Ib_d, Ic_d) receive an input error, and control the actual output current detection amount (Ia_d, Ib_d, Ic_d) of each phase to match the active power control signals (Ia_d*, Ib_d*, Ic_d*) (309,329,349), That is, the dq-αβ inverse transform unit ( 312,332,352).

The q-current controllers 410, 430, and 450 of each phase have the reactive power control signals (Ia_q*, Ib_q*, Ic_q*) calculated for each phase using the proportional integral (PI) controller inside (409, 429, 449) and the actual output current detection amount ( Ia_q, Ib_q, Ic_q) received an error between the input, and the actual output current detection amount (Ia_q, Ib_q, Ic_q) of each phase is controlled to match the reactive power control signals (Ia_q*, Ib_q*, Ic_q*) (409,429,449), That is, the dq-αβ inverse transform unit ( 312, 332, 352).

The dq-αβ inverse transform units 312 , 332 , 352 of each phase included in the inverse transform unit 509 use the phase information (θ_ut) 504 that is the output of the phase locked loop 503 to the active power compensation reference current signal ( Va_d*, Vb_d*, Vc_d*) (311,331,351) and reactive power compensation reference current signal (Va_q*, Vb_q*, Vc_q*) (411,431,451) are subjected to dq-αβ inverse transformation to α component (Va_α) of the three-phase signal , Vb_α, Vc_α) (313, 333, 353) is generated and output to the control signal conversion unit (Offset PWM) 506 . Meanwhile, in this process, the β components (Va_β, Vb_β, Vc_β) (314, 334, 354) of the three-phase signal generated together by the inverse transform units 312, 332, and 352 are not used.

The control signal conversion unit (Offset PWM) 506 converts the α component (Va_α, Vb_α, Vc_α) of the three-phase signal input from the inverse conversion unit 509 to the switching of each switch included in the 4 legs of the inverting unit 130 . After conversion into a control signal (PWM signal) (Sa, Sb, Sc, Sn) 507 , it is output to a switching element included in each leg of the inverting unit 130 .

On the other hand, the reference value generator 274 receives the active power reference values (Pa_ref, Pb_ref, Pc_ref) (307,327,347) and reactive power reference values (Qa_ref, Qb_ref, Qc_ref) (407,427,447) for each phase from the energy management system 613 and receives active power It can output to the control module 271 and the reactive power control module 272 .

In addition, the reference value generating unit 274 receives the power factor (PF) command value for each phase from the energy management system 613, and the active power reference value ( Pa_ref, Pb_ref, Pc_ref) (307, 327, 347) and reactive power reference values (Qa_ref, Qb_ref, Qc_ref) (407, 427, 447) may be converted to output to the active power control module 271 and the reactive power control module 272 .

The power factor-active/reactive power converter (PF-PQ) 274-1 receives a command for the power factor command value for each phase from the energy management system 613, and uses it according to the general equation below, the active power reference value for each phase and Convert to reactive power reference value.

Apparent power:

Power Factor (PF):

Active Power:

Reactive Power:

Here, since the apparent power (S) is a predefined value according to the hardware configuration of the power conversion device according to the preferred embodiment of the present invention, power factor-active/reactive power converter (PF-PQ) (274-1) may generate an active power reference value and a reactive power reference value using the power factor command value for each phase received from the energy management system 613 and the predetermined apparent power (S).

As described above, the active power reference value (Pa_ref, Pb_ref, Pc_ref) (307, 327, 347) of each phase, which is a result value that is directly input from the energy management system 613 or generated by the power factor-active/reactive power conversion process, and each phase Reactive power reference values (Qa_ref, Qb_ref, Qc_ref) 407 , 427 , 447 are input as reference values to the active power control module 271 and the reactive power control module 272 .

8 is a diagram illustrating a configuration example of an independent micro-grid power system to which a 3-phase 4-wire 4-LEG power conversion device according to a preferred embodiment of the present invention is applied.

Referring to FIG. 8 , as a power supply system in remote areas that are not connected to island regions or commercial power grids, an independent microgrid power system composed of energy storage devices 607 and 608 such as storage batteries and a diesel generator 600 can be implemented. , the 3-phase 4-wire type 4-LEG power conversion device according to a preferred embodiment of the present invention is particularly applicable to the power conversion device 608 connected to the storage battery 607. In this case, the diesel generator 600 and commercial power source can be applied in place of each other.

In this configuration, when the load ratio of the diesel generator 600 is low, the fuel efficiency is lowered. In order to maximize fuel efficiency, power is supplied to the load 609 to operate near the rated load and at the same time, the battery is charged. At this time, when an unbalanced load is applied to the load side, the power conversion device varies the amount of power in each phase to compensate for this and the amount of charge of the storage battery 607 must be adjusted, in this case, the power conversion device 608 and the generator control device 610, digital The watt-hour meter 611 may be configured to be connected to the energy management system 613 through a communication network 612 to enable collection and control of information.

The energy management system 613 reads the load amount information of each phase from the watt-hour meter 611 and determines the amount of charge/discharge to the storage battery 607 so that an appropriate load for each phase is applied to the output of the diesel generator 600, and the power conversion device for the storage battery (608), it is possible to output a charge/discharge active power for each phase and a reactive power command for each phase. With this operation method, the installed capacity of the storage battery 607 can be optimized, the operating fuel efficiency of the diesel generator 600 is maximized, and the active power of the generator output load is balanced for each phase, and the power factor can be maintained at 1. there is.

When the load increases to exceed the capacity of the generator, the power converter 608 operates to discharge power from the storage battery 607 . At this time, the load 609 is a mixture of one-phase and three-phase, and thus an imbalance of the load between the phases occurs. It can be discharged in different ways, and when necessary, one phase is charged and one phase is discharged stably to absorb and discharge power even during extreme unbalance compensation operation.

So far, the present invention has been looked at with respect to preferred embodiments thereof. Those of ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments are to be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

1000: 3-phase 4-wire 4-LEG power converter
110: DC link 130: inverting unit
150 : Reactor
160: capacitor
210: grid breaker
220: commercial power 250: load
270: controller
271: active power control module 272: reactive power control module
273: phase information generation unit 274: reference value generation unit
301, 321, 341, 401, 421, 441: all-pass filter
303, 323, 343, 403, 423, 443: rotation synchronization coordinate system transformation unit
305, 325, 345: Active Power Calculator
308, 328, 348: active power controller
310, 330, 350: d-current controller
405, 425, 445: reactive power calculator
408, 428, 448: reactive power controller
410, 430, 450: q-current controller
506: control signal conversion unit
509: inverse transform unit
610: generator control unit 613: energy management system

Claims (6)

delete Consists of a three-phase, four-wire, four-leg inverter, one end connected to an energy storage device, and the other end connected to commercial power and a load to receive power supplied by commercial power to charge the energy storage device, or to an inverting unit discharging the power stored in the storage device and providing it to a load; and
Receive the active power reference value and reactive power reference value for each phase from the energy management system, or receive the power factor command value for each phase from the energy management system to generate the active power reference value and reactive power reference value for each phase, and voltage of each phase supplied by commercial power value, the current value of each phase output by the inverting unit, and the on/off control of the switching elements included in the inverting unit according to the active power reference value and the reactive power reference value to store the energy for each phase of three phases Comprising a controller for independently controlling the charging and discharging of the device, active power and reactive power,

the controller
a phase information generator for generating phase information (θ_ut) synchronized with commercial power using voltage values (Van, Vbn, Vcn) of each phase of the commercial power;
Active power compensation standard for receiving the voltage values (Van, Vbn, Vcn) of the first phase, the second phase and the third phase, the active power reference value for each phase, and the phase information (θ_ut), respectively, and controlling the active power for each phase an active power control module for outputting current signals (Va_d*, Vb_d*, Vc_d*);
Reactive power compensation standard for receiving the current values (Ian, Ibn, Icn) of the first phase, the second phase and the third phase, the reactive power reference value for each phase, and the phase information (θ_ut), respectively, and controlling the reactive power for each phase a reactive power control module for outputting current signals (Va_q*, Vb_q*, Vc_q*);
Receive the active power reference value and reactive power reference value for each phase from the energy management system, or receive the power factor command value for each phase from the energy management system to generate an active power reference value and reactive power reference value for each phase, the active power control module and the reactive power a reference value generator outputting each of the power control modules; and
According to the active power compensation reference current signal and the reactive power compensation reference current signal, a switching control signal (Sa, Sb, Sc, Sn) for controlling the on/off of the switches included in the inverting unit is generated, and the It includes a control signal conversion unit for outputting to the inverting unit,

The active power control module is
a first phase active power control unit, a second phase active power control unit, and a third phase active power control unit;
Each of the first phase active power control unit, the second phase active power control unit and the third phase active power control unit,
an all-pass filter that receives the output voltages (Van, Vbn, Vcn) of the corresponding phase of the commercial power source and outputs α, β components (Va_αβ, Vb_αβ, Vc_αβ) of the phase voltage delayed by 90 degrees;
The α and β components (Va_αβ, Vb_αβ, Vc_αβ) of the corresponding phase voltage are received from the all-pass filter, the phase information (θ_ut) is received, and the d-axis and q-axis voltage components (Va_d) are performed by performing rotation-synchronous coordinate system transformation. ,Vb_d,Vc_d,Va_q,Vb_q,Vc_q) a rotation synchronization coordinate system transforming unit that outputs;
The d-axis and q-axis voltage components (Va_d, Vb_d, Vc_d, Va_q, Vb_q, Vc_q) and the corresponding phase d-axis and q-axis current components (Ia_d, Ib_d, Ic_d, Ia_q, Ib_q) input from the reactive power control module ,Ic_q) using the active power calculator to output the active power values (Pa, Pb, Pc) of the corresponding phase;
Active power control for receiving an error value between the active power values of the corresponding phase (Pa, Pb, Pc) and the active power reference values (Pa_ref, Pb_ref, Pc_ref) input from the reference value generator, and controlling the input error value to decrease an active power controller for outputting signals (Ia_d*, Ib_d*, Ic_d*); and
The error between the output active power control signals (Ia_d*, Ib_d*, Ic_d*) of the corresponding phase and the d-axis current components (Ia_d, Ib_d, Ic_d) of the corresponding phase input from the reactive power control module are received, and the input and a d-current controller for generating and outputting active power compensation reference current signals (Va_d*, Vb_d*, Vc_d*) of the corresponding phase to control the error to decrease,

The reactive power control module is
Comprising a first phase reactive power control unit, a second phase reactive power control unit and a third phase reactive power control unit,
Each of the first phase reactive power control unit, the second phase reactive power control unit and the third phase reactive power control unit,
an all-pass filter receiving the output currents (Ian, Ibn, Icn) of the corresponding phase of the inverting unit and outputting α, β components (Ia_αβ, Ib_αβ, Ic_αβ) of the phase current delayed by 90 degrees;
Receives α and β components (Ia_αβ, Ib_αβ, Ic_αβ) of the corresponding phase current from the all-pass filter, receives the phase information, performs rotation synchronous coordinate system transformation, and performs d-axis and q-axis current components (Ia_d, Ib_d, Ic_d, Ia_q, Ib_q, Ic_q) to output a rotation synchronization coordinate system transformation unit;
The d-axis and q-axis current components (Ia_d, Ib_d, Ic_d, Ia_q, Ib_q, Ic_q) and corresponding phase d-axis and q-axis voltage components (Va_d, Vb_d, Vc_d, Va_q, Vb_q) input from the active power control module , Vc_q) using a reactive power calculator to output the reactive power values (Qa, Qb, Qc) of the corresponding phase;
Reactive power control to receive the error value between the reactive power value (Qa, Qb, Qc) of the corresponding phase and the reactive power reference value (Qa_ref, Qb_ref, Qc_ref) input from the reference value generator, and to control the input error value to decrease a reactive power controller for outputting signals (Ia_q*, Ib_q*, Ic_q*); and
The corresponding phase receives the error between the output reactive power control signal (Ia_q*, Ib_q*, Ic_q*) of the corresponding phase and the q-axis current component (Ia_q, Ib_q, Ic_q) of the corresponding phase, and controls the input error to decrease Power conversion device comprising a q-current controller to generate and output the reactive power compensation reference current signal (Va_q*, Vb_q*, Vc_q*) of the phase. delete delete The method of claim 2, wherein the phase information generator
a rotation synchronous coordinate system transformation unit that receives voltage values (Van, Vbn, Vcn) and the phase information of each phase of the commercial power supply, performs rotation synchronous coordinate system transformation, and outputs a d-axis voltage (V_de); and
and a phase lock loop that receives the d-axis voltage (V_de) from the rotation synchronization coordinate system converter and generates phase information (θ_ut) synchronized with commercial power. 3. The method of claim 2,
With respect to the active power compensation reference current signal (Va_d*, Vb_d*, Vc_d*) and the reactive power compensation reference current signal (Va_ q*, Vb_q*, Vc_q*) using the phase information (θ_ut), inverse dq Further comprising an inverse transform unit that sequentially performs the transformation and inverse α-β transformation to generate α components (Va_α, Vb_α, Vc_α) of the three-phase signal and output it to the control signal converting unit,
The control signal converter converts the α component of the three-phase signal input from the inverse converter into switching control signals (Sa, Sb, Sc, Sn) of each switch included in the inverting part and outputs the converted power conversion device.

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