KR20210138984A - 3 Phase 4 wire grid-connected power conditioning system - Google Patents

Abstract

The present invention discloses a 3-phase 4-wire power conversion device capable of individual power control of each phase based on 4-leg. 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, to combine the existing single-phase d-q control method based on 4-LEG hardware, so that the output power of each phase is individually controlled differently and independently. In addition, by using this technology, the present invention is capable of individually controlling the active power and reactive power of each phase. When using this, the power factor of each phase is individually controlled at the power receiving point of the power supply system composed of many single-phase loads, such as power plants or apartment complexes in island areas.

Description

3-phase 4-wire power conversion device capable of individual power control of each phase based on 4-leg {3 Phase 4 wire grid-connected power conditioning system}

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

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 for solving the problem of load imbalance between phases of the three-phase power supply, a three-phase power system was constructed using three one-phase photovoltaic inverters and three one-phase storage battery inverters each. .

For the control method of this three-phase power system, the frequency-active power droop method and voltage-reactive power droop method were applied to the inverter for storage batteries. 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 such a 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. In order 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.

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

A method of supplementing the problems of the prior art shown in FIG. 1 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 3-phase 4-wire inverter can compensate for current imbalance of the load 60 or be used as an active filter type.

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 separately 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 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 three-phase four-wire power supply is used in a consumer according to the prior art, a load unbalance situation occurs due to the use of a one-phase load, which causes a voltage unbalance phenomenon in which the three-phase voltage balance is broken.

Figure 4 is a three-phase load unbalance caused by a one-phase unbalanced load when a power reception voltage imbalance occurs due to power unevenness at the reception point caused by a 1-phase unbalanced load in a low-voltage consumer power system, or when a generator is operated in an independent microgrid. It indicates a situation in which the output voltage of the generator becomes unbalanced.

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 a three-phase 4-LEG type power conversion device (PCS) ), there is a problem that the control algorithm that can operate stably is insufficient.

The present invention is to solve the problems of the prior art described above, as a power conversion device (PCS) linked to a storage battery, including a 3-phase 4-wire 4-leg inverter, load imbalance due to 1-phase load in an independent operation mode, and to provide a power conversion device capable of supplying stable power within a specified voltage range by resolving the resulting imbalance of the phase voltage.

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 an 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 by controlling on/off of switching elements included in the inverting unit according to the voltage value of each phase supplied by the commercial power and the current value of each phase output by the inverting unit, the energy storage device for each phase of three phases Includes a controller that independently controls the charging and discharging of

In addition, the controller may include: 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; An active power compensation reference current signal (Va_d*, an active power control module that outputs Vb_d*,Vc_d*); Reactive power compensation reference current signal (Va_q*, a reactive power control module that outputs Vb_q*,Vc_q*); And according to the active power compensation reference control 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 unit,

an all-pass filter receiving the output voltages (Van, Vbn, Vcn) of the corresponding phases of the commercial power supply and outputting α, β components (Va_αβ, Vb_αβ, Vc_αβ) of the phase voltage delayed by 90 degrees; α, 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) for outputting a rotation synchronization coordinate system transformation unit; 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 an active power calculator for outputting the active power values (Pa, Pb, Pc) of the corresponding phase; An active power control signal (Ia_d*) for receiving an error value between the active power values of the corresponding phase (Pa, Pb, Pc) and a preset active power reference value (Pa_ref, Pb_ref, Pc_ref) and controlling the input error value to decrease ,Ib_d*,Ic_d*) an active power controller that outputs; and an error between the output active power control signal (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 the 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 for outputting the reactive power value (Qa, Qb, Qc) of the corresponding phase; Reactive power control signal (Ia_q*) for receiving an error value between the reactive power value of the corresponding phase (Qa, Qb, Qc) and a preset reactive power reference value (Qa_ref, Qb_ref, Qc_ref), and controlling the input error value to decrease ,Ib_q*,Ic_q*) a reactive power controller that outputs; And receiving 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 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 generation unit, 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, the power conversion device, 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*) with respect to the inverse dq conversion, and an inverse transform unit for sequentially performing inverse α-β transformation and outputting a three-phase signal to the control signal converting unit (Space Vector PWM), wherein the control signal converting unit converts the three-phase signal input from the inverse transform unit to the It can be converted into a switching control signal (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 must be summed and controlled. As such, the conventional dq control algorithm has no choice but to control the power of three phases in a batch, so it was impossible to control the size of each phase power 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 structure of a 4-leg scheme so as to control the power of each phase differently, and can control each of them based on dq control.

In addition, by using this technology, the present invention can control the active power and reactive power of each phase individually, and by using this, the power receiving point of the power supply system composed of many single-phase loads, such as a power plant or an apartment complex in an island area There is also the effect that the power factor of each phase can be individually controlled.

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 diagram showing an extreme unbalanced driving state in which the current of two phases is charged and the current of one phase is discharged in a linked operation situation.
5 is a diagram comparing the functions of the dq control method according to the prior art and the respective phase control method according to the present invention.
6 is a view showing the overall configuration of a 3-phase 4-wire 4-LEG power conversion device according to a preferred embodiment of the present invention.
7 is a block diagram illustrating 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 view 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-leg 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 are disposed between the inverting unit 130 and the filter unit 150 and 160 to measure the current of each phase output from the inverting unit 130 It is installed on the side of the current measuring unit 140, the commercial power supply 220, and is configured to include a voltage measuring unit 200 and a controller 270 for measuring the voltage of each phase of the commercial power supply 220.

The controller 270 receives the output current values Ian, Ibn, Icn of each phase output from the inverting unit 130 from the current measuring unit 140 , and the commercial power supply 220 is supplied from the voltage measuring unit 200 . Voltage values (Van, Vbn, Vcn) of each phase to be output are received. In addition, the controller 270 generates a control signal (PWM signal) for controlling the on/off of the plurality of switches included in the inverting unit 130 by 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 inverter 100 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 storage battery and a step-up converter for storage batteries are 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, the neutral point of the three-phase voltage can be adjusted, thereby solving the problem of unbalance of voltages between phases.

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 .

The current measuring unit 140 installed between the inverting unit 130 and the filter units 150 and 160 measures the output currents Ian, Ibn, and Icn of each phase output by the inverting unit 130 to the controller 270 . print out The voltage measuring unit 200 measures the voltages (Van, Vbn, Vcn) of each phase of the commercial power supply 220 and outputs it to the controller 270 .

In addition, in order to supply power from the commercial power source 220 to the load 250 , or to supply power from the inverting unit 130 to the load 250 , the output lines of the filter units 150 and 160 are connected to the commercial power source 220 . It is withdrawn to the /load 250 side.

The controller 270 receives the output current value 140 of the inverting unit 130 and the voltage value 200 of the commercial power supply 220, and performs a grid-connected operation or current control through internal calculation to control the switching. A signal (PWM control signal) 280 is output to the inverting unit 130 to control switching of switches included in the inverting unit 130 .

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

7 is a block diagram illustrating 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.

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 current control unit 508 and the control signal conversion unit 506 ) is included.

The current control unit 508 includes an active power control module, a reactive power control module, and a phase information generation unit.

The active power control module 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 second phase Each of the active power control unit and the third phase active power control unit includes all-pass filters 301, 321, 341, rotation synchronous coordinate system transformation units 303, 323, 343, active power calculators 305, 325, 345, active power controller 308, 328 , 348 , and d-current controllers 310 , 330 , 350 .

The reactive power control module 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 second phase Each of the 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 transformation unit (403,423,443), a reactive power calculator (405,425,445), a reactive power controller (408,428,448), and q- current controllers 410 , 430 , and 450 .

The phase information generating unit includes a rotation synchronization coordinate system transformation unit 501 and a phase locked loop (PLL) 503 .

The current control unit 508 operates when the commercial power source 220 operates normally, and when charging current is introduced into an energy storage device such as a storage battery 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 source 220 is required, and for this, a phase locked loop 503 is used. Voltage values (Van, Vbn, Vcn) 500 of each phase of the commercial power source 220 measured by the voltage measuring unit 200 are input to the rotation synchronous coordinate system conversion unit 501, and the phase locked loop 503 is rotated The phase information (θ_ut) 504 synchronized with the commercial power supply 220 is generated using the d-axis voltage (V_de) 502 that is the output of the synchronous coordinate system transformation unit 501 to the rotation synchronous coordinate system transformation units 501,303,323,343,403,423,443. print out

Then, the rotation synchronization coordinate system transformation unit 501 performs rotation synchronization 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, the rotation synchronization coordinate system conversion unit 303,323,343 of each phase voltage is the phase information (θ_ut) 504 that is the output of each phase voltage (Van, Vbn, Vcn) (300, 320, 340) of the commercial power supply 220 and the phase lock loop 503 ) to output the d-axis and q-axis voltages 304, 324, and 344, respectively.

In addition, the rotation synchronization coordinate system conversion unit 403,423,443 of each phase current is the output of each phase current (Ian, Ibn, Icn) (400,420,440) of the commercial power supply 220 and the phase lock loop 503 (θ_ut) (504) Outputs the d-axis and q-axis currents 404, 424, and 444 using .

좌표계-정지좌표계(αβ)-동기좌표계(dq)로의 변환 과정을 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 90도 위상차인 점을 이용해 정지좌표계로의 변환을 위해 a상 신호와 크기는 같고 위상만 90도 뒤지는 가상의 파형을 생성한 후 αβ-dq 컨버터의 입력에 인가시킨다. 즉, 기준신호와 크기는 같고 위상만 90도 뒤지는 가상의 신호를 만드는 전역통과필터를 사용하여 단상 제어 d-q 변환에 적용하였다. However, since the voltage and current signal input is single-phase in each phase individual control method,

-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 degrees out of phase with each other to convert to a 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 90 degrees in phase is used and applied to the single-phase controlled dq transform.

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 회전 동기 좌표계 변환부(303, 323, 343)로 입력된다. As described above, when the voltage values 300, 320, 340 of each phase measured by the voltage measuring unit 200 are input to the all-pass filters 301, 321, 341, each signal having a phase delayed by 90 degrees can be obtained, From this, each phase voltage

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

The rotation synchronous coordinate system transformation units 303 , 323 , and 343 of each phase voltage perform dq transformation using the phase angle θ_ut 504 to calculate the d-axis, q-axis, and o-axis components for each phase voltage. Then, the q-axis voltage components (Va_q, Vb_q, Vc_q) representing the voltage peak values of each phase and the d-axis voltage components (Va_d, Vb_d, Vc_d) (304, 324, 344) representing the components lagging by 90 degrees are output.

성분(402, 422, 442)이 회전 동기 좌표계 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 140 are input to the all-pass filters 401, 421, 441, the phase is changed Each signal delayed by 90 degrees can be obtained, from which the

The components 402 , 422 , and 442 are input to the rotation synchronization coordinate system transformation units 403 , 423 , 443 .

The rotation synchronous coordinate system transformation 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 component and d-axis component (304, 324, 344), which are the DC components of the peak output voltage of each phase, and the q-axis component and the d-axis component (404, 424, 444), which are the DC components of the output current peak value, are the active power calculator. (305,325,345) and reactive power calculator (405,425,445) to generate active power detection amount (Pa, Pb, Pc) (306, 326, 346) and reactive power detection amount (Qa, Qb, Qc) (406,426,446). These signals are compared with the active power reference signals (Pa_ref, Pb_ref, Pc_ref) (307, 327, 347) of each phase and the reactive power reference signals (Qa_ref, Qb_ref, Qc_ref) of each phase, and then the error value is determined by the active power controller ( 308, 328, 348) and each phase reactive power controller (408, 428, 448), the role of each controller is 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 detected amount of active power in each phase to match the active power reference value, that is, controls the input error to decrease s (Ia_d*, Ib_d*, Ic_d*) 309, 329, and 349 are generated and output to the d-current controllers 310, 330, and 350, respectively.

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 output to the q-current controllers (410,430,450).

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 an internal proportional integral (PI) controller and the actual output current detection amount ( Ia_d, Ib_d, Ic_d) receive an 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 active power compensation reference current signals Va_d*, Vb_d*, Vc_d* (311, 331, 351) of each phase controlled to reduce the input error are generated and output to the dq-αβ-abc inverse transform unit 509 .

The q-current controllers (410, 430, 450) of each phase use the proportional integral (PI) controller inside the reactive power control signals (Ia_q*, Ib_q*, Ic_q*) calculated for each phase (409, 429, 449) and the actual output current detection amount ( Ia_q, Ib_q, Ic_q) receive the error between the input, and control the actual output current detection amount (Ia_q, Ib_q, Ic_q) of each phase to match the reactive power control signals (Ia_q*, Ib_q*, Ic_q*) (409,429,449), That is, the reactive power compensation reference current signals (Va_q*, Vb_q*, Vc_q*) 411,431,451 of each phase controlled to reduce the input error are generated and output to the dq-αβ-abc inverse transform unit 509 .

Inverse conversion unit 509 for 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), inverse dq Transformation and inverse α-β transformation are sequentially performed to output a three-phase signal to a control signal converter (Space Vector PWM) 506 .

The control signal converting unit (Space Vector PWM) 506 converts the three-phase signal input from the inverting unit 509 into the switching control signal (PWM signal) of each switch included in the 4 legs of the inverting unit 130 (Sa, Sb, Sc, Sn) (507), and then output to the switching element included in each leg of the inverting unit (130).

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 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 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 charge amount of the storage battery 607 must be adjusted. At this time, 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 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 storage battery power conversion device 608 can output the charge command for each phase. With this operation method, the installed capacity of the storage battery 607 can be optimized, the fuel efficiency of the operation of the diesel generator 600 can be maximized, and the load amount of the generator output can be balanced.

When the load increases to exceed the capacity of the generator, the power conversion device 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. and, when necessary, one phase can be charged and one phase can be stably absorbed and released even during extreme unbalance compensation operation such as discharging.

So far, with respect to the present invention, the preferred embodiments have been looked at. 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
140: current measuring unit 150: reactor
160: capacitor
200: voltage measuring unit 210: system breaker
220: commercial power 250: load
270: controller
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 (SVPWM)
508: current controller
509: inverse transform unit
610: generator control unit 613: energy management system

Claims (6)

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
By controlling the on/off of the switching elements included in the inverting unit according to the voltage value of each phase supplied by the commercial power and the current value of each phase output by the inverting unit, the energy storage device for each phase of the three phases A power conversion device comprising a controller for independently controlling charging and discharging. The method of claim 1, wherein the controller is
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;
An active power compensation reference current signal (Va_d*, an active power control module that outputs Vb_d*,Vc_d*);
Reactive power compensation reference current signal (Va_q*, a reactive power control module that outputs Vb_q*,Vc_q*); and
According to the active power compensation reference control 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, Power conversion device comprising a control signal conversion unit output to the inverting unit. The method of claim 2, wherein 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 receiving the output voltages (Van, Vbn, Vcn) of the corresponding phases of the commercial power supply and outputting 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) to output a rotation synchronization coordinate system transforming unit;
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 an active power calculator for outputting the active power values (Pa, Pb, Pc) of the corresponding phase;
An active power control signal (Ia_d*) for receiving an error value between the active power values of the corresponding phase (Pa, Pb, Pc) and a preset active power reference value (Pa_ref, Pb_ref, Pc_ref) and controlling the input error value to decrease ,Ib_d*,Ic_d*) an active power controller that outputs; and
An error between the output active power control signal (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 is received, and the input Power conversion device comprising a d-current controller for generating and outputting the active power compensation reference current signal (Va_d*, Vb_d*, Vc_d*) of the corresponding phase to control the error to decrease. The method of claim 2, wherein 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 that receives the output currents (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;
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 the 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 for outputting the reactive power values (Qa, Qb, Qc) of the corresponding phase;
Reactive power control signal (Ia_q*) for receiving an error value between the reactive power value of the corresponding phase (Qa, Qb, Qc) and a preset reactive power reference value (Qa_ref, Qb_ref, Qc_ref), and controlling the input error value to decrease ,Ib_q*,Ic_q*) a reactive power controller that outputs; and
Receives 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 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. The method of claim 2, wherein the phase information generating unit
a rotation synchronous coordinate system transformation unit that receives voltage values (Van, Vbn, Vcn) of each phase of commercial power and the phase information, 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,
For 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*), inverse dq transformation and inverse α-β transformation are sequentially performed Further comprising an inverse transform unit for outputting a three-phase signal to the control signal converting unit (Space Vector PWM) by performing,
The control signal converter converts the three-phase signal input from the inverse converter into a switching control signal (Sa, Sb, Sc, Sn) of each switch included in the inverting part and outputs the converted signal.

Images