阅读说明：本技术 一种附加控制信号的电流源接入装置 (Current source access device with additional control signal ) 是由 王少荣 侯珏 苏鑫 李妍 于 2019-08-26 设计创作，主要内容包括：本发明属于电力系统自动控制领域,提供一种附加控制信号的电流源接入装置,该装置输入附加控制器发出的SPWM信号,经过内部三相逆变和滤波后输出三相附加电流信号作为附加控制信号,直接耦合至变流器控制单元的三相电流采样回路中,在原有采样电流信号的基础上产生一定的幅值、相位偏差；通过对三相采样电流信号进行微调来调整变流器控制单元的控制特性,进而改善变流器主电路连接的受控对象(如光伏发电/电动汽车等)的动态特性。本发明提供的附加控制信号的电流源接入装置,可以应用在各种附加控制应用场景下,本发明满足了在不改变变流器控制单元物理结构的基础上装配附加控制装置的应用需求,其原理简单可靠,成本低廉。(The invention belongs to the field of automatic control of an electric power system, and provides a current source access device with an additional control signal, wherein an SPWM signal sent by an additional controller is input into the device, a three-phase additional current signal is output as the additional control signal after internal three-phase inversion and filtering, the additional control signal is directly coupled into a three-phase current sampling loop of a converter control unit, and a certain amplitude value and phase deviation are generated on the basis of an original sampling current signal; the control characteristics of the converter control unit are adjusted by finely adjusting the three-phase sampling current signals, so that the dynamic characteristics of controlled objects (such as photovoltaic power generation/electric vehicles and the like) connected with the converter main circuit are improved. The current source access device for the additional control signal can be applied to various additional control application scenes, meets the application requirement of assembling the additional control device on the basis of not changing the physical structure of the converter control unit, and has the advantages of simple and reliable principle and low cost.)

1. A current source access device for adding a control signal, comprising: the input signal is a three-phase SPWM signal output by an additional controller, the output signal is a three-phase additional current signal after three-phase inversion and filtering, the three-phase additional current signal is directly coupled to a three-phase current sampling loop of a converter control unit as an additional control signal, certain amplitude and phase deviation are generated on the basis of the original sampling current signal, the control characteristic of the converter control unit is optimized by adjusting the three-phase current sampling signal, the dynamic characteristic of a controlled object connected with a main circuit of the converter is further improved, and the internal control mechanism of the converter control unit is not changed.

2. Current source access means for an additional control signal according to claim 1, characterized in that: the three-phase inverter circuit is characterized by comprising a three-phase inverter circuit and an LC filter circuit, wherein a PMOS (P-channel metal oxide semiconductor) tube and an NMOS (N-channel metal oxide semiconductor) tube are respectively adopted by an upper bridge arm and a lower bridge arm of the three-phase inverter circuit as switching elements, each phase is only driven by a group of SPWM (sinusoidal pulse width modulation) driving signals isolated by an optical coupler to realize complementary conduction of the switching tubes of the upper bridge arm and the lower bridge arm, the whole three-phase inverter circuit is driven by three groups of SPWM signals, a power supply of the driving circuit is provided by.

3. Current source access means for an additional control signal according to claim 2, characterized in that: the three-phase inverter circuit comprises a PMOS (P-channel metal oxide semiconductor) tube Q₁、Q₃、Q₅Is IRF9530, NMOS tube Q₄、Q₆、Q₂As IRF840, a fast diode D₁、D₂、D₃、D₄、D₅、D₆For FR207, resistor R in MOS transistor driving circuit₁、R₅、R₉Is 1.5 k.OMEGA.R₂、R₆、R₁₀Is 2.4 k.OMEGA.R₃、R₇、R₁₁Is 12.5 k.OMEGA.R₄、R₈、R₁₂13.5k omega, and a bridge arm connected in series with a load resistor R₁₃～R₁₈20 omega, optical coupler isolation element OC₁、OC₂、OC₃TLP521-1, a DC power supply V_DIs 30V; resistance R₁、R₅、R₉One end of the DC power supply V is connected together_DThe other end of the positive electrode is respectively connected with a PMOS tube Q₁、Q₃、Q₅Gate and resistor R of₂、R₆、R₁₀One terminal of (1), resistance R₂、R₆、R₁₀The other ends of the optical coupling and isolating elements OC are respectively connected with₁、OC₂、OC₃Output port high level node and resistor R₃、R₇、R₁₁One terminal of (1), resistance R₃、R₇、R₁₁the other ends of the two are respectively connected with an NMOS tube Q₄、Q₆、Q₂Gate and resistor R of₄、R₈、R₁₂One terminal of (1), resistance R₄、R₈、R₁₂The other ends of the two are connected with a DC power supply V_DNegative electrode of MOS transistor Q₁、Q₃、Q₅Are connected with a DC power supply V_DAnode of (2), MOS tube Q₄、Q₆、Q₂Respectively connected with resistors R₁₃、R₁₅、R₁₇One terminal of (1), resistance R₁₃、R₁₅、R₁₇The other ends of the two resistors are respectively connected with a resistor R₁₄、R₁₆、R₁₈ToTerminal, resistance R₁₄、R₁₆、R₁₈Are respectively connected with Q at the other end₄、Q₆、Q₂Drain electrode of, Q₄、Q₆、Q₂Are connected with a DC power supply V_DNegative pole of (2), inverted three-phase signal is respectively from R₁₃And R₁₄Inter node, R₁₅And R₁₆Inter node, R₁₇And R₁₈And outputting by the intermediate node.

4. Current source access means for an additional control signal according to claim 2, characterized in that: the LC filter circuit comprises a series inductor L₁、L₂、L₃40mH, a parallel capacitor C₁、C₂、C₃7.5uF, and the LC filter circuit is connected in a way that the phase A is taken as an example, and the inductor L₁One end of the first capacitor is connected with the A-phase output voltage signal, and the other end of the first capacitor is connected with the capacitor C₁Capacitor C₁The other end of which is connected to a reference ground.

Technical Field

The invention belongs to the field of automatic control of power systems, and particularly relates to a current source access device with an additional control signal.

Technical Field

In recent years, as a large amount of renewable energy power generation, distributed power sources, flexible loads, active loads and the like are connected to a power system, the problem of poor dynamics of the power system gradually becomes one of main factors influencing stable operation of the power system. In addition, due to intermittent power fluctuation of the renewable energy power generation system and the regulation effect introduced by the optimization scheduling system, the distributed power supply, the flexible load, the electric vehicle, the energy storage device and other systems have own feedback control systems, and the dynamic process of the power system becomes very complicated. Nowadays, it is a common idea to adopt an additional control principle to realize dynamic characteristic optimization control in the field of dynamic characteristic optimization of power generation and distribution links of a power system. For example, a difference adjustment system in an automatic excitation control system of a synchronous generator realizes voltage adjustment and reactive power distribution by adjusting generator excitation current or rotor current, and adopts a power system stabilizer to suppress low-frequency oscillation and the like.

The existing additional control strategy mainly comprises that a disturbance signal is directly or indirectly measured and is switched into a control system after being converted, so that an additional channel for compensating disturbance influence is formed. The additional control signals are coupled in such a way that they are superimposed on the d-and q-axis reference signals of the converter control unit, e.g. u_dref、u_qref、i_drefAnd i_qrefThe control characteristics of the whole control system are influenced by adjusting the reference signal of the converter control unit. However, since the implementation of the additional control method employs coupling the additional control signal to the d-axis and q-axis reference signals of the converter control unit, the implementation process of the method is complicated. Especially, in some applications where the converter control unit is integrally packaged and assembled to the control side of the main circuit of the converter, it is difficult to further improve the control characteristics of the converter control circuit by additional control.

Disclosure of Invention

The invention aims to solve the defects in the prior art, and provides a current source access device for an additional control signal, which aims to optimize an access strategy for additional control and solve the problem that an additional control signal cannot be coupled because a converter control unit is completely packaged; the current source access device of the additional control signal inputs an SPWM signal sent by an additional controller, outputs a three-phase additional current signal as an additional control signal after internal three-phase inversion and filtering, is directly coupled to a three-phase current sampling loop of a converter control unit, and generates certain amplitude and phase deviation on the basis of the original sampling current signal; the control characteristics of the converter control unit are adjusted by finely adjusting the three-phase sampling current signals, so that the dynamic characteristics of controlled objects (such as photovoltaic power generation/electric vehicles and the like) connected with the converter main circuit are improved.

The current source access device with the additional control signal outputs a current signal instead of a voltage signal as an additional coupling signal, and the main reason is that the voltage signal determines a phase signal theta output by a phase-locked loop in a converter control unit_PLL，θ_PLLDetermines the d and q axis components u of the internal voltage of the converter control unit_d、u_qIs influenced by the actual running state of the power system, if the three-phase voltage sampling signal of the converter control unit is changed, the theta output by the internal phase-locked loop_PLLFailure to accurately reflect the actual operating state of the power system may lead to control failure.

The invention relates to a current source access device with an additional control signal, which comprises a three-phase inverter circuit and an LC filter circuit.

The three-phase inverter circuit is different in the mode that SPWM signals drive switching tubes on bridge arms, the traditional three-phase inverter circuit has 6 groups of driving signals for respectively controlling A, B, C switching tubes on three-phase upper and lower bridge arms, and because the switching tubes of the same-phase upper and lower bridge arms are complementarily conducted, the driving signals are also complementary, the three-phase inverter circuit provided by the invention only adopts three groups of driving signals for respectively driving the three-phase bridge arms, and each group of driving signals synchronously drives the switching tubes on the upper and lower bridge arms after being processed by the corresponding driving circuit.

The three phasesThe topological structure of the inverter circuit is that a resistor R₁、R₅、R₉One end of the DC power supply V is connected together_DThe other end of the positive electrode is respectively connected with a P-channel enhanced MOS tube Q₁、Q₃、Q₅Gate and resistor R of₂、R₆、R₁₀One terminal of (1), resistance R₂、R₆、R₁₀The other ends of the optical coupling and isolating elements OC are respectively connected with₁、OC₂、OC₃Output port high level node and resistor R₃、R₇、R₁₁One terminal of (1), resistance R₃、R₇、R₁₁The other ends of the N-channel enhanced MOS tubes are respectively connected with an N-channel enhanced MOS tube Q₄、Q₆、Q₂Gate and resistor R of₄、R₈、R₁₂One terminal of (1), resistance R₄、R₈、R₁₂The other ends of the two are connected with a DC power supply V_DThe negative electrode of (1). MOS tube Q₁、Q₃、Q₅Are connected with a DC power supply V_DAnode of (2), MOS tube

Q₄、Q₆、Q₂Respectively connected with resistors R₁₃、R₁₅、R₁₇One end of (1), a resistor

R₁₃、R₁₅、R₁₇The other ends of the two resistors are respectively connected with a resistor R₁₄、R₁₆、R₁₈One terminal of (1), resistance R₁₄、R₁₆、R₁₈Are respectively connected with Q at the other end₄、Q₆、Q₂Drain electrode of, Q₄、Q₆、Q₂Are connected with a DC power supply V_DThe negative electrode of (1). The inverted three-phase signals are respectively from R₁₃And R₁₄Inter node, R₁₅And R₁₆Inter node, R₁₇And R₁₈And outputting by the intermediate node.

The working principle of the three-phase inverter circuit is that the resistor R is reasonably selected₁～R₁₂When the optocoupler is switched off, the NMOS tube of the lower bridge arm is switched on, when the optocoupler is switched on, the PMOS tube of the upper bridge arm is switched on, and the SPWM signal is input from the input port of the optocoupler. The driving strategyThe complementary conduction of the upper bridge arm switching tube and the lower bridge arm switching tube of the three-phase inverter circuit driven by three groups of driving signals is realized, and the source electrode of the PMOS tube of the upper bridge arm and the source electrode of the NMOS tube of the lower bridge arm are respectively connected to the DC power supply V_DThe power supply of the driving circuit can be a direct current power supply V_DThe voltage driving signal is provided without influencing the potential of the three-phase output signal. An anti-parallel diode between the drain and the source of each MOS tube plays a role of reverse freewheeling. Resistance R₁₃-R₁₈Because of the delayed turn-off phenomenon of the switching tube, the upper and lower bridge arms may have instantaneous short-circuit fault at the moment of switching, and the resistor is connected in series in the bridge arm loop to play a role of current-limiting protection. In addition, a resistance R₁₃-R₁₈As a load resistor, most of the AC voltage drop after inversion is borne by the load resistor, which is helpful for generating three-phase current output signals.

The LC filter circuit takes phase A as an example, and an inductor L₁One end of the first capacitor is connected with the A-phase output voltage signal, and the other end of the first capacitor is connected with the capacitor C₁Capacitor C₁The other end of which is connected to a reference ground. The values of the series inductor and the parallel capacitor are properly selected, and an LC filter circuit formed by the series inductor and the parallel capacitor can enable harmonic impedance voltage drop of higher harmonic current on the series inductor to be far larger than harmonic impedance voltage drop on the parallel capacitor, the harmonic current almost completely flows into the filter capacitor, and the load almost has no harmonic current.

Compared with the prior art, the invention has the following beneficial effects:

1. The current source access device with the additional control signal can be applied to various additional control application scenes, the three-phase additional current signals are directly applied to the three-phase sampling current of the converter control unit in parallel, the additional control signal coupling is realized, the amplitude value and the phase position of the coupled sampling current signal generate certain deviation and are input to the converter control unit, and the internal control mechanism of the converter control unit is not changed.

2. The coupling signal in the current source access device with the additional control signal is a current signal instead of a voltage signal, so that the normal work of the voltage phase-locked loop in the converter control unit can be prevented from being influenced.

3. The invention is composed of a three-phase inverter circuit and an LC filter circuit, wherein PMOS tubes and NMOS tubes are respectively adopted by upper and lower bridge arms of the three-phase inverter circuit as switching elements, each phase is driven by only one group of SPWM driving signals isolated by an optical coupler to realize complementary conduction of the switching tubes of the upper and lower bridge arms, the whole three-phase inverter circuit is driven by three groups of SPWM signals, the power supply of the driving circuit is provided by a direct current power supply of the three-phase inverter circuit, and the potential of a three-phase output signal cannot be influenced by a voltage driving signal.

4. The invention meets the application requirement of assembling the additional control device on the basis of not changing the physical structure of the converter control unit, and has simple and reliable principle and low cost.

Drawings

Fig. 1 is a schematic diagram of an overall connection structure of a current source access device with an additional control signal according to an embodiment of the present invention.

Fig. 2 is a vector diagram of a three-phase current signal coupling method according to an embodiment of the present invention.

Fig. 3 is a schematic circuit diagram of a current source connection device for additional control signals according to an embodiment of the present invention.

Fig. 4 is a simulated waveform of three-phase additional current signals of a current source access device of an additional control signal provided by the embodiment of the invention.

FIG. 5 shows a three-phase sampled current i on the grid side according to an embodiment of the present invention_a、i_b、i_cAnd the three-phase additional current signal i 'amplified by 10 times'_a、i'_b、i'_cThe simulated waveform of (2).

FIG. 6 shows an amplitude i ″' of a three-phase current signal after coupling and superposition according to an embodiment of the present invention_{a_Mag}、i″_{b_Mag}、i″_{c_Mag}And three-phase sampling current amplitude i on the network side_{a_Mag}、i_{b_Mag}、i_{c_Mag}And (4) obtaining a simulation result.

FIG. 7 shows a three-phase current signal phase i ″ after coupling and superposition according to an embodiment of the present invention_{a_Phase}、i″_{b_Phase}、i″_{c_Phase}AndThree-phase sampling current phase i of network side_{a_Phase}、i_{b_Phase}、i_{c_Phase}And (4) obtaining a simulation result.

Detailed Description

In order to facilitate understanding of the present invention, the present invention will be described in further detail below with reference to the accompanying drawings and examples. One embodiment of the present invention is shown in the drawings, it being understood that this example is intended to illustrate the invention only and is not intended to limit the invention. This embodiment is provided so that this disclosure will be thorough and complete.

The current source access device for the additional control signal provided by the embodiment of the invention aims to optimize the access strategy of the additional control and solve the problem that the converter control unit is completely packaged and cannot be coupled with the additional control signal; the current source access device of the additional control signal inputs an SPWM signal sent by an additional controller, outputs a three-phase current source as an additional coupling signal after internal three-phase inversion and filtering, is directly coupled to a three-phase current sampling loop of a converter control unit, and generates certain amplitude and phase deviation on the basis of the original sampling current signal; the control effect of the current source access device with the additional control signal is that the control characteristic of the converter control unit is optimized by adjusting the three-phase sampling current signal, and then the dynamic characteristic of a controlled object connected with the main circuit of the converter is improved.

The schematic diagram of the overall connection structure of the current source access device with the additional control signal provided by the embodiment of the invention is shown in the attached figure 1, wherein a photovoltaic power generation device is incorporated into a power distribution network of a power system by a converter main circuit, and a converter control unit applies a converter control signal to the converter main circuit and receives a sampling feedback signal. The additional controller samples three-phase voltage current signals at a main circuit grid-connected point of the converter, SPWM additional control signals are generated after internal comparison amplification, superposition processing and other links, the SPWM additional control signals are applied to a current source access device of the additional control signals, the three-phase additional current signals are coupled in a three-phase current sampling loop of a converter control unit after three-phase inversion, filtering and other links, the control characteristics of the converter control unit are adjusted by fine adjustment of the three-phase sampling current signals, and then the dynamic characteristics of an active power distribution network are improved.

A circuit schematic diagram of the current source access device with the additional control signal provided by the embodiment of the invention is shown in fig. 3, and the current source access device comprises a three-phase inverter circuit and an LC filter circuit.

The three-phase inverter circuit comprises PMOS transistor Q₁、Q₃、Q₅Is IRF9530, and NMOS tube is Q₄、Q₆、Q₂As IRF840, a fast diode D₁、D₂、D₃、D₄、D₅、D₆Is FR207, the resistance of the resistor in the MOS transistor driving circuit is R₁、R₅、R₉Is 1.5 k.OMEGA.R₂、R₆、R₁₀Is 2.4 k.OMEGA.R₃、R₇、R₁₁Is 12.5 k.OMEGA.R₄、R₈、R₁₂13.5k omega, and a bridge arm connected in series with a load resistor R₁₃～R₁₈20 omega, optical coupler isolation element OC₁、OC₂、OC₃Model number of TLP521-1, DC power supply V_DIs 30V.

The topological structure of the three-phase inverter circuit is that a resistor R₁、R₅、R₉One end of the DC power supply V is connected together_DThe other end of the positive electrode is respectively connected with a PMOS tube Q₁、Q₃、Q₅Gate and resistor R of₂、R₆、R₁₀One terminal of (1), resistance R₂、R₆、R₁₀The other ends of the optical coupling and isolating elements OC are respectively connected with₁、OC₂、OC₃Output port high level node and resistor R₃、R₇、R₁₁One terminal of (1), resistance R₃、R₇、R₁₁The other ends of the two are respectively connected with an NMOS tube Q₄、Q₆、Q₂Gate and resistor R of₄、R₈、R₁₂One terminal of (1), resistance R₄、R₈、R₁₂The other ends of the two are connected with a DC power supply V_DThe negative electrode of (1). MOS tube Q₁、Q₃、Q₅Are commonly connected toDC power supply V_DAnode of (2), MOS tube Q₄、Q₆、Q₂Respectively connected with resistors R₁₃、R₁₅、R₁₇One terminal of (1), resistance R₁₃、R₁₅、R₁₇The other ends of the two resistors are respectively connected with a resistor R₁₄、R₁₆、R₁₈One terminal of (1), resistance R₁₄、R₁₆、R₁₈Are respectively connected with Q at the other end₄、Q₆、Q₂Drain electrode of, Q₄、Q₆、Q₂Are connected with a DC power supply V_DThe negative electrode of (1). The inverted three-phase signals are respectively from R₁₃And R₁₄Inter node, R₁₅And R₁₆Inter node, R₁₇And R₁₈And outputting by the intermediate node.

The working principle of the three-phase inverter circuit is that an SPWM signal is input from an optical coupler input port, when the optical coupler is turned off, the source grid voltage of a PMOS (P-channel metal oxide semiconductor) tube of an upper bridge arm is lower than 2V, the PMOS tube is turned off, the grid source voltage of an NMOS (N-channel metal oxide semiconductor) tube of a lower bridge arm is higher than 9V, the NMOS tube is saturated, when the optical coupler is turned on, the source grid voltage of the PMOS tube of the upper bridge arm is higher than 9V, the PMOS tube is saturated, the grid source voltage of the NMOS tube of the lower bridge arm is. The driving strategy realizes complementary conduction of upper and lower bridge arm switching tubes of the three-phase inverter circuit driven by three groups of driving signals, and the source electrode of the PMOS tube of the upper bridge arm and the source electrode of the NMOS tube of the lower bridge arm are respectively connected to a direct-current power supply V_DThe power supply of the driving circuit can be a direct current power supply V_DThe voltage driving signal is provided without influencing the potential of the three-phase output signal. An anti-parallel diode between the drain and the source of each MOS tube plays a role of reverse freewheeling. Resistance R₁₃-R₁₈Because of the delayed turn-off phenomenon of the switching tube, instantaneous short-circuit faults may exist in the upper and lower bridge arms at the moment of switching, the resistor is connected in series in the bridge arm loop to play a role in current limiting protection, and the instantaneous short-circuit current is not higher than 0.75A. In addition, a resistance R₁₃-R₁₈As a load resistor, most of the AC voltage drop after inversion is borne by the load resistor, and the amplitude of the output signal of the three-phase current source is about 0.1A.

The LC filter circuit comprises series inductors L₁、L₂、L₃Has an inductance of 40mH, and a parallel capacitor C₁、C₂、C₃The capacitance value of (2) was 7.5 uF. The LC filter circuit is connected in a way that the phase A is taken as an example, and the inductor L₁One end of the first capacitor is connected with the A-phase output voltage signal, and the other end of the first capacitor is connected with the capacitor C₁Capacitor C₁The other end of which is connected to a reference ground. The values of the series inductor and the parallel capacitor are properly selected, and an LC filter circuit formed by the series inductor and the parallel capacitor can enable harmonic impedance voltage drop of higher harmonic current on the series inductor to be far larger than harmonic impedance voltage drop on the parallel capacitor, the harmonic current almost completely flows into the filter capacitor, and the load almost has no harmonic current.

In order to verify the technical feasibility of the current source access device with the additional control signal provided by the embodiment of the invention, a simulation example corresponding to fig. 3 is established by using board-level analog/digital circuit board simulation software multisim14.0 for simulation verification. In the simulation example, the input SPWM signal is modulated by a three-phase sine wave having an effective value of 10V and a frequency of 50Hz and a triangular wave having a peak-to-peak value of 20V, a frequency of 10kHZ, and a duty ratio of 50%. The simulation time length is set to 80ms, the external resistive load adopts a Y-shaped connection method, and the load size is 0.002 omega. The final output three-phase current source signal is shown in fig. 4, and the current source access device of the designed additional control signal can output a three-phase additional current signal of a 0.1A level, and the phase of the three-phase additional current signal is controlled by the SPWM signal. The simulation results show that the current source access device for the additional control signal provided by the embodiment of the invention is technically feasible.

In order to verify the technical feasibility of the coupling mode of the current signal output by the current source access device with the additional control signal provided by the embodiment of the invention, the current source signal can be effectively input to the converter control unit instead of flowing into the power grid in the coupling process, the amplitude and the phase of the coupled sampling current signal can generate a small deviation and input to the converter control unit, and a simulation example corresponding to the figure 1 is built by using international general direct-current power transmission simulation software PSCAD/EMTDC to perform simulation verification. In the simulation example, a three-phase 10kV voltage source passes through 10kV/0.3The 81kV delta/Y three-phase transformer supplies power to a three-phase load, the power factor of the three-phase load is 0.9, the rated power is 60kVA, and the three-phase load is formed by connecting a 0.726 omega resistor in series with an 1.1193mH inductor. The embodiment of the invention provides a three-phase sampling current i on a network side_a、i_b、i_cAnd the three-phase additional current signal i 'amplified by 10 times'_a、i'_b、i'_cThe simulation waveforms of (1) are shown in fig. 5, the effective value of each phase of the additional output current signal is given according to 2% of the original current at the coupling point, and the phase of each phase of the additional output current signal is given according to 30 degrees of the original current phase at the lagging coupling point. At the time t-1 s, three-phase additional current signal i'_a、i'_b、i'_cAnd the three-phase current signal sampling loop is coupled. The three-phase current signal amplitude i' after coupling superposition provided by the embodiment of the invention_{a_Mag}、i″_{b_Mag}、i″_{c_Mag}And three-phase sampling current amplitude i on the network side_{a_Mag}、i_{b_Mag}、i_{c_Mag}The simulation result is shown in fig. 6, and it can be seen that the three-phase current signal amplitude i ″, which is obtained after coupling and superposition_{a_Mag}、i″_{b_Mag}、i″_{c_Mag}A variation of about 0.1A is generated, and the three-phase sampling current amplitude i on the network side_{a_Mag}、i_{b_Mag}、i_{c_Mag}No change occurred. The embodiment of the invention provides a three-phase current signal phase i' after coupling and superposition_{a_Phase}、i″_{b_Phase}、i″_{c_Phase}And three-phase sampled current phase i on the network side_{a_Phase}、i_{b_Phase}、i_{c_Phase}The simulation result is shown in fig. 7, and it can be seen that the phase i ″' of the three-phase current signal after coupling and superposition_{a_Phase}、i″_{b_Phase}、i″_{c_Phase}A change of about 0.5 degrees is generated, and the three-phase sampling current phase i of the network side_{a_Phase}、i_{b_Phase}、i_{c_Phase}No change occurred. Therefore, simulation verification results show that the current signal output by the current source access device of the additional control signal provided by the embodiment of the invention can be effectively input to the converter control unit instead of flowing into the power grid in the coupling process. The simulation result tableThe current source signal can be effectively input to the converter control unit instead of flowing into the power grid in the coupling process, the amplitude and the phase of the coupled sampling current signal can generate small deviation and can be input to the converter control unit, and the signal coupling strategy of the current source access device with the additional control signal provided by the embodiment of the invention is technically feasible.

details not described in this specification are within the skill of the art that are well known to those skilled in the art.

The above description is only exemplary of the invention and should not be taken as limiting the invention, as any modification, equivalent replacement, or improvement made without departing from the spirit and principle of the invention should fall within the protection scope of the invention.