CN113765140A - Operation mode control method, device and system suitable for current source type photovoltaic grid-connected inverter - Google Patents

Abstract

The invention discloses an operation mode control method, a device and a system suitable for a current source photovoltaic grid-connected inverter, which can calculate the inner loop current reference in the current source operation mode; Output active power and reactive power; based on grid voltage, inverter actual output active power and reactive power, grid voltage amplitude, inverter active power given value and reactive power given value, voltage amplitude given value, calculate the inner loop current reference in the voltage source operation mode; connect the inner loop current reference in the current source operation mode or the inner loop current reference in the voltage source operation mode, combine the inverter output current and grid voltage phase to calculate the inverter The inverter modulates the wave, modulates the carrier signal, and generates a control signal that controls the power switch of the inverter. The invention can realize that when the inverter needs to operate in the voltage source mode after receiving the control signal sent by the field controller, the external controller signal is connected to realize the voltage source mode operation of the photovoltaic grid-connected inverter.

Description

Operation mode control method, device and system suitable for current source type photovoltaic grid-connected inverter

Technical Field

The invention belongs to the technical field of grid-connected inverter control, and particularly relates to a control method, a device and a system for a current source type photovoltaic grid-connected inverter.

Background

By the end of 2019, installed capacities of wind power generation and photovoltaic power generation in China are 210GW and 204GW, which account for about 20.63% of total capacity of power supplies in China, and new energy becomes the second largest energy in China. New energy represented by wind power and photovoltaic will continue to develop rapidly, and finally a high-proportion new energy power system is formed nationwide. However, the conventional photovoltaic grid-connected inverter installed in a large scale at present generally adopts a current source operation mode and works along with grid voltage/frequency grid connection, and in a high-proportion new energy power system, the photovoltaic inverter lacks inertia, frequency modulation and voltage regulation functions, so that the challenges are brought to the safe and stable operation of the power system.

Disclosure of Invention

Aiming at the problems, the invention provides a method, a device and a system for controlling the operation mode of a current source type photovoltaic grid-connected inverter, wherein the photovoltaic grid-connected inverter adopts the traditional current source operation mode under the normal working condition, and the software and hardware functions of the original inverter are reserved; when the inverter receives a control signal sent by the station controller and needs to operate in a voltage source mode, the external controller is accessed to realize the voltage source mode operation of the photovoltaic grid-connected inverter.

In order to achieve the technical purpose and achieve the technical effects, the invention is realized by the following technical scheme:

in a first aspect, the invention provides an operation mode control system suitable for a current source type photovoltaic grid-connected inverter, which comprises a direct current voltage measurement module, a direct current measurement module, an alternating voltage measurement module, a PLL phase locking module, an MPPT and direct current voltage outer loop control module, a current inner loop control module, a pulse width modulation module, an actual power calculation module and a self-synchronous voltage source droop control and virtual impedance control module;

the direct current voltage measuring module acquires the direct current voltage U of the inverter_dcAnd output to MPPT and direct current voltage outer loop control module;

the direct current measuring module acquires direct current I of the inverter_dcAnd output to MPPT and direct current voltage outer loop control module;

the alternating current measuring module acquires the output current i of the inverter_LabcAnd output to the actual power calculation module and the current inner loop control module;

the alternating voltage measurement module collects the voltage u of the power grid_gabcRespectively output to a PLL phase locking module, an actual power calculation module, a droop control module of a self-synchronizing voltage source and a virtual impedance control module;

the PLL phase locking module is used for locking the phase according to the power grid voltage u_gabcCalculating the voltage amplitude U of the power grid_gmAnd grid voltage phase theta_g；

The MPPT and DC outer ring control module is used for controlling the DC voltage U of the inverter_dcAnd the DC current I of the inverter_dcAnd calculating to obtain an inner ring current reference i in the current source operation mode_{ref_abc}；

The actual power calculation module outputs current i according to the inverter_LabcAnd the network voltage u_gabcAnd calculating to obtain the actual output active power P of the inverter_eAnd reactive power Q_e；

The droop control and virtual impedance control module of the self-synchronizing voltage source is used for controlling droop according to the voltage u of the power grid_gabcActual output active power P of inverter_eAnd reactive power Q_eGiven value P of active power of inverter_refAnd given value of reactive power Q_refAnd the grid voltage amplitude U_gmGiven value of voltage amplitude value U_nAnd calculating to obtain an inner ring current reference i in the voltage source operation mode_{ref_abc_vir}；

The current inner loop control module responds to different operation mode control instructions and is connected to an inner loop current reference i in a current source operation mode in combination with a gating signal output by a gating switch S_{ref_abc}Or inner loop current reference i in voltage source operation mode_{ref_abc_vir}And an inverter output current i_LabcAnd grid voltage phase theta_gObtaining the modulation wave V of the photovoltaic grid-connected inverter_mabc；

The pulse width modulation module modulates a wave V_mabcFor carrier signal V_rAnd modulating, generating a control signal D for controlling a power switch of the photovoltaic inverter, and sending the control signal D to the inverter so that the inverter finishes the control of the operation mode.

Optionally, the inner loop current reference i in the current source operation mode_{ref_abc}The calculation formula of (2) is as follows:

in the formula: u shape_dcrefDC voltage i corresponding to maximum power point for photovoltaic array working after MPPT control_{ref_abc_d}、i_{ref_abc_q}Current reference i in current source mode_{ref_abc}Dq component, K, in a two-phase rotating coordinate system_pv、K_ivAnd the parameter is the outer loop PI parameter of the direct current voltage.

Optionally, the inner loop current reference i in the voltage source operation mode_{ref_abc_vir}The calculation formula of (2) is as follows:

in the formula: u shape_nTo a nominal voltage amplitude, D_qIs a reactive sag factor, K_qAs integral coefficient, ω_nAt a nominal angular frequency, D_pIs the active droop coefficient, J is the virtual moment of inertia, s is the Laplace operator, U_VSGAmplitude, omega, of modulated wave generated for virtual synchronous machine control_VSGModulated wave angular frequency, theta, generated for virtual synchronous machine control_VSGControlling the generated phase, U, for a virtual synchronizer_VmabcThe virtual synchronizer is used for controlling self-generated three-phase voltage, L is the inductance value of a main circuit filter, and r is the parasitic resistance of the filter inductance.

Optionally, the inverter modulates the wave V_mabcThe calculation formula of (2) is as follows:

wherein: i is_dref、I_qrefAre respectively inner ring current reference i_{ref_abc}Or i_{ref_abc_vir}Dq-axis component in a two-phase rotating coordinate system, I_d、I_qAre respectively the inductive current i_LabcDq component, K, in a two-phase rotating coordinate system_pi、K_iiIs the current regulator PI parameter, omega is the grid angular frequency, s is the Laplace operator, L is the inductance value of the main circuit filter，V_d、V_qIs u_gabcDq-axis component in a two-phase rotating coordinate system, M_d、M_qIs a dq axis modulation component under the two-phase rotating coordinate system of the inverter.

In a second aspect, the present invention provides an operation mode control method suitable for a current source type photovoltaic grid-connected inverter, including:

based on dc current I of inverter_dcAnd a DC voltage U_dcCalculating the inner loop current reference i in the current source operation mode_{ref_abc}；

Based on the voltage u of the network_gabcCalculating the voltage amplitude U of the power grid_gmGrid voltage phase theta_g；

Based on the output current i of the inverter_LabcAnd the network voltage u_gabcCalculating the actual output active power P of the inverter_eAnd reactive power Q_e；

Based on the voltage u of the network_gabcActual output active power P of inverter_eAnd reactive power Q_eAnd the voltage amplitude U of the power grid_gmGiven value P of active power of inverter_refAnd given value of reactive power Q_refGiven value of voltage amplitude value U_nCalculating the inner loop current reference i in the voltage source operation mode_{ref_abc_vir}；

Responding to different operation mode control instructions, and switching in an inner ring current reference i in a current source operation mode_{ref_abc}Or inner loop current reference i in voltage source operation mode_{ref_abc_vir}Combined with inverter output current i_LabcAnd grid voltage phase theta_gCalculating the modulation wave V of the inverter_mabcFor carrier signal V_rAnd modulating, generating a control signal D for controlling the inverter power switch, and sending the control signal D to the inverter so that the inverter finishes the control of the operation mode.

Optionally, the inner loop current reference i in the current source operation mode_{ref_abc}The calculation formula of (2) is as follows:

in the formula: u shape_dcrefDC voltage i corresponding to maximum power point for photovoltaic array working after MPPT control_{ref_abc_d}、i_{ref_abc_q}Is a current reference i in a current source mode_{ref_abc}Dq component, K, in a two-phase rotating coordinate system_pv、K_ivAnd the parameter is the outer loop PI parameter of the direct current voltage.

Optionally, the inner loop current reference i in the voltage source operation mode_{ref_abc_vir}The calculation formula of (2) is as follows:

in the formula: u shape_nTo a nominal voltage amplitude, D_qIs a reactive sag factor, K_qAs integral coefficient, ω_nAt a nominal angular frequency, D_pIs the active droop coefficient, J is the virtual moment of inertia, s is the Laplace operator, U_VSGAmplitude, omega, of modulated wave generated for virtual synchronous machine control_VSGModulated wave angular frequency, theta, generated for virtual synchronous machine control_VSGControlling the generated phase, U, for a virtual synchronizer_VmabcThe virtual synchronizer is used for controlling self-generated three-phase voltage, L is the inductance value of a main circuit filter, and r is the parasitic resistance of the filter inductance.

Optionally, the inverter modulates the wave V_mabcThe calculation formula of (2) is as follows:

wherein: i is_dref、I_qrefAre respectively inner ring current reference i_{ref_abc}Or i_{ref_abc_vir}Dq-axis component in a two-phase rotating coordinate system, I_d、I_qAre respectively the inductive current i_LabcDq component, K, in a two-phase rotating coordinate system_pi、K_iiIs the current regulator PI parameter, omega is the grid angular frequency, s is the Laplace operator, L is the main circuit filter inductance value, V_d、V_qIs u_gabcDq-axis component in a two-phase rotating coordinate system, M_d、M_qIs a dq axis modulation component under the two-phase rotating coordinate system of the inverter.

In a third aspect, the present invention provides an operation mode control device suitable for a current source type photovoltaic grid-connected inverter, including:

a first calculation module for calculating a DC current I based on the inverter_dcAnd a DC voltage U_dcCalculating the inner loop current reference i in the current source operation mode_{ref_abc}；

A second calculation module for calculating a grid voltage u based on_gabcCalculating the voltage amplitude U of the power grid_gmAnd grid voltage phase theta_g；

A third calculation module for outputting a current i based on the inverter_LabcAnd the network voltage u_gabcCalculating the actual output active power P of the inverter_eAnd reactive power Q_e；

A fourth calculation module for calculating a grid voltage u based on_gabcActual output active power P of inverter_eAnd reactive power Q_eAnd the voltage amplitude U of the power grid_gmGiven value P of active power of inverter_refAnd given value of reactive power Q_refGiven value of voltage amplitude value U_nCalculating the inner loop current reference i in the voltage source operation mode_{ref_abc_vir}；

A control module for responding to different operation mode control instructions and accessing an inner ring current reference i in the current source operation mode_{ref_abc}Or inner loop current reference i in voltage source operation mode_{ref_abc_vir}Combined with inverter output powerStream i_LabcAnd grid voltage phase theta_gCalculating the modulation wave V of the inverter_mabcFor carrier signal V_rAnd modulating, generating a control signal D for controlling the inverter power switch, and sending the control signal D to the inverter so that the inverter finishes the control of the operation mode.

Optionally, the inner loop current reference i in the current source operation mode_{ref_abc}The calculation formula of (2) is as follows:

in the formula: u shape_dcrefDC voltage i corresponding to maximum power point for photovoltaic array working after MPPT control_{ref_abc_d}、i_{ref_abc_q}Current reference i in current source mode_{ref_abc}Dq component, K, in a two-phase rotating coordinate system_pv、K_ivAnd the parameter is the outer loop PI parameter of the direct current voltage.

Optionally, the inner loop current reference i in the voltage source operation mode_{ref_abc_vir}The calculation formula of (2) is as follows:

in the formula: u shape_nTo a nominal voltage amplitude, D_qIs a reactive sag factor, K_qAs integral coefficient, ω_nAt a nominal angular frequency, D_pIs the active droop coefficient, J is the virtual moment of inertia, s is the Laplace operator, U_VSGAmplitude, omega, of modulated wave generated for virtual synchronous machine control_VSGModulated wave angular frequency generated for virtual synchronous machine control，θ_VSGControlling the generated phase, U, for a virtual synchronizer_VmabcThe virtual synchronizer is used for controlling self-generated three-phase voltage, L is the inductance value of a main circuit filter, and r is the parasitic resistance of the filter inductance.

Optionally, the inverter modulates the wave V_mabcThe calculation formula of (2) is as follows:

wherein: i is_dref、I_qrefAre respectively inner ring current reference i_{ref_abc}Or i_{ref_abc_vir}Dq-axis component in a two-phase rotating coordinate system, I_d、I_qAre respectively the inductive current i_LabcDq component, K, in a two-phase rotating coordinate system_pi、K_iiIs the current regulator PI parameter, omega is the grid angular frequency, s is the Laplace operator, L is the main circuit filter inductance value, V_d、V_qIs u_gabcDq-axis component in a two-phase rotating coordinate system, M_d、M_qIs a dq axis modulation component under the two-phase rotating coordinate system of the inverter.

In a fourth aspect, the present invention provides an operation mode control system for a current source type photovoltaic grid-connected inverter, comprising a storage medium and a processor;

the storage medium is used for storing instructions;

the processor is configured to operate in accordance with the instructions to perform a method according to any of the second aspects.

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

the invention discloses a control method, a device and a system for a current source type photovoltaic grid-connected inverter, wherein the photovoltaic grid-connected inverter adopts a traditional current source operation mode under normal working conditions, and software and hardware functions of the original inverter are reserved; when the photovoltaic grid-connected inverter receives a control signal sent by the site controller and needs to operate in a voltage source mode, the external controller is accessed to realize the voltage source mode operation of the photovoltaic grid-connected inverter. Therefore, the method not only provides an important technical basis for the inverter control scheme applied to the distributed new energy power generation and high-proportion new energy power system, but also completely reserves the software and hardware structure of the traditional photovoltaic inverter and can effectively reduce the production cost.

Drawings

In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which:

fig. 1 is a block diagram showing an overall configuration of an inverter operation mode control device according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of the invention.

The following detailed description of the principles of the invention is provided in connection with the accompanying drawings.

Example 1

The embodiment of the invention provides an operation mode control method suitable for a current source type photovoltaic grid-connected inverter, which specifically comprises the following steps:

based on dc current I of inverter_dcAnd a DC voltage U_dcCalculating the inner loop current reference i in the current source operation mode_{ref_abc}；

Based on the voltage u of the network_gabcCalculating the voltage amplitude U of the power grid_gmGrid voltage phase theta_g；

Based on the output current i of the inverter_LabcAnd the network voltage u_gabcCalculating the actual output active power P of the inverter_eAnd reactive power Q_e；

Based on the voltage u of the network_gabcActual output active power P of inverter_eAnd reactive power Q_eAnd the voltage amplitude U of the power grid_gmGiven value P of active power of inverter_refAnd is idleGiven value of power Q_refGiven value of voltage amplitude value U_nCalculating the inner loop current reference i in the voltage source operation mode_{ref_abc_vir}；

Responding to different operation mode control instructions, and switching in an inner ring current reference i in a current source operation mode_{ref_abc}Or inner loop current reference i in voltage source operation mode_{ref_abc_vir}Combined with inverter output current i_LabcAnd grid voltage phase theta_gCalculating the modulation wave V of the inverter_mabcFor carrier signal V_rAnd modulating, generating a control signal D for controlling the inverter power switch, and sending the control signal D to the inverter so that the inverter finishes the control of the operation mode.

In a specific implementation manner of the embodiment of the present invention, the inner loop current reference i in the current source operation mode_{ref_abc}The calculation formula of (2) is as follows:

in the formula: u shape_dcrefDC voltage i corresponding to maximum power point for photovoltaic array working after MPPT control_{ref_abc_d}、i_{ref_abc_q}Current reference i in current source mode_{ref_abc}Dq component, K, in a two-phase rotating coordinate system_pv、K_ivAnd the parameter is the outer loop PI parameter of the direct current voltage.

In a specific implementation manner of the embodiment of the invention, the inner loop current reference i in the voltage source operation mode_{ref_abc_vir}The calculation formula of (2) is as follows:

in the formula: u shape_nTo a nominal voltage amplitude, D_qIs a reactive sag factor, K_qAs integral coefficient, ω_nAt a nominal angular frequency, D_pIs the active droop coefficient, J is the virtual moment of inertia, s is the Laplace operator, U_VSGAmplitude, omega, of modulated wave generated for virtual synchronous machine control_VSGModulated wave angular frequency, theta, generated for virtual synchronous machine control_VSGControlling the generated phase, U, for a virtual synchronizer_VmabcThe virtual synchronizer is used for controlling self-generated three-phase voltage, L is the inductance value of a main circuit filter, and r is the parasitic resistance of the filter inductance.

In a specific implementation of the embodiment of the invention, the inverter modulation wave V_mabcThe calculation formula of (2) is as follows:

wherein: i is_dref、I_qrefAre respectively inner ring current reference i_{ref_abc}Or i_{ref_abc_vir}Dq-axis component in a two-phase rotating coordinate system, I_d、I_qAre respectively the inductive current i_LabcDq component, K, in a two-phase rotating coordinate system_pi、K_iiIs the current regulator PI parameter, omega is the grid angular frequency, s is the Laplace operator, L is the main circuit filter inductance value, V_d、V_qIs u_gabcDq-axis component in a two-phase rotating coordinate system, M_d、M_qIs a dq axis modulation component under the two-phase rotating coordinate system of the inverter.

Example 2

Based on the same inventive concept as embodiment 1, an embodiment of the present invention provides an operation mode control device suitable for a current source type photovoltaic grid-connected inverter, including:

a first calculation module for calculating a DC current I based on the inverter_dcAnd a DC voltage U_dcInner in current source operation modeLoop current reference i_{ref_abc}；

A second calculation module for calculating a grid voltage u based on_gabcCalculating the voltage amplitude U of the power grid_gmGrid voltage phase theta_g；

A third calculation module for outputting a current i based on the inverter_LabcAnd the network voltage u_gabcCalculating the actual output active power P of the inverter_eAnd reactive power Q_e；

A fourth calculation module for calculating a grid voltage u based on_gabcActual output active power P of inverter_eAnd reactive power Q_eAnd the voltage amplitude U of the power grid_gmGiven value P of active power of inverter_refAnd given value of reactive power Q_refGiven value of voltage amplitude value U_nCalculating the inner loop current reference i in the voltage source operation mode_{ref_abc_vir}；

A control module for responding to different operation mode control instructions and accessing an inner ring current reference i in the current source operation mode_{ref_abc}Or inner loop current reference i in voltage source operation mode_{ref_abc_vir}Combined with inverter output current i_LabcAnd grid voltage phase theta_gCalculating the modulation wave V of the inverter_mabcFor carrier signal V_rAnd modulating, generating a control signal D for controlling the inverter power switch, and sending the control signal D to the inverter so that the inverter finishes the control of the operation mode.

In a specific implementation manner of the embodiment of the present invention, the inner loop current reference i in the current source operation mode_{ref_abc}The calculation formula of (2) is as follows:

in the formula: u shape_dcrefDC voltage i corresponding to maximum power point for photovoltaic array working after MPPT control_{ref_abc_d}、i_{ref_abc_q}Current reference i in current source mode_{ref_abc}Dq component, K, in a two-phase rotating coordinate system_pv、K_ivAnd the parameter is the outer loop PI parameter of the direct current voltage.

In a specific implementation manner of the embodiment of the invention, the inner loop current reference i in the voltage source operation mode_{ref_abc_vir}The calculation formula of (2) is as follows:

in the formula: u shape_nTo a nominal voltage amplitude, D_qIs a reactive sag factor, K_qAs integral coefficient, ω_nAt a nominal angular frequency, D_pIs the active droop coefficient, J is the virtual moment of inertia, s is the Laplace operator, U_VSGAmplitude, omega, of modulated wave generated for virtual synchronous machine control_VSGModulated wave angular frequency, theta, generated for virtual synchronous machine control_VSGControlling the generated phase, U, for a virtual synchronizer_VmabcThe virtual synchronizer is used for controlling self-generated three-phase voltage, L is the inductance value of a main circuit filter, and r is the parasitic resistance of the filter inductance.

In a specific implementation of the embodiment of the invention, the inverter modulation wave V_mabcThe calculation formula of (2) is as follows:

wherein: i is_dref、I_qrefAre respectively inner ring current reference i_{ref_abc}Or i_{ref_abc_vir}Dq-axis component in a two-phase rotating coordinate system, I_d、I_qAre respectively the inductive current i_LabcDq component, K, in a two-phase rotating coordinate system_pi、K_iiIs the current regulator PI parameter, omega is the grid angular frequency, s is the Laplace operator, L is the main circuit filter inductance value, V_d、V_qIs u_gabcDq-axis component in a two-phase rotating coordinate system, M_d、M_qIs a dq axis modulation component under the two-phase rotating coordinate system of the inverter.

Example 3

Based on the same inventive concept as embodiment 1, the embodiment of the invention provides an operation mode control system suitable for a current source type photovoltaic grid-connected inverter, which comprises a storage medium and a processor;

the storage medium is used for storing instructions;

the processor is configured to operate in accordance with the instructions to perform a method according to any of the embodiments 1.

Example 4

As shown in fig. 1, a photovoltaic inverter main circuit 1 is a photovoltaic cell panel, and is incorporated into a power grid after passing through a three-phase inverter main circuit and an LC filter circuit, and an embodiment of the present invention provides an operation mode control system suitable for a current source type photovoltaic grid-connected inverter, which specifically includes a dc voltage measurement module 2, a dc current measurement module 3, an ac current measurement module 4, an ac voltage measurement module 5, a PLL phase locking module 6, an MPPT and dc voltage outer loop control module 7, an actual power calculation module 8, a self-synchronous voltage source droop control and virtual impedance control module 9, a current inner loop control module 10, and a pulse width modulation module 11;

the direct current voltage measuring module 2 collects the direct current voltage U of the inverter_dcAnd output to MPPT and direct current voltage outer loop control module;

the direct current measuring module 3 collects direct current I of the inverter_dcAnd output to MPPT and direct current voltage outer loop control module;

the alternating current measuring module 4 collects the output current i of the inverter_LabcAnd output to the actual power calculation module and the current inner loop control module;

the alternating voltage measuring module 5 collects the voltage u of the power grid_gabcRespectively transportThe output signals are sent to a PLL phase locking module, an actual power calculation module and a droop control and virtual impedance control module of a self-synchronizing voltage source;

the PLL phase-locking module 6 is used for locking the phase according to the power grid voltage u_gabcCalculating the voltage amplitude U of the power grid_gmAnd grid voltage phase theta_g；

The MPPT and DC voltage outer loop control module 7 is used for controlling the DC voltage U according to the inverter_dcAnd the DC current I of the inverter_dcAnd calculating to obtain an inner ring current reference i in the current source operation mode_{ref_abc}；

The actual power calculation module 8 outputs current i according to the inverter_LabcAnd the network voltage u_gabcAnd calculating to obtain the actual output active power P of the inverter_eAnd reactive power Q_e；

The droop control and virtual impedance control module 9 of the self-synchronizing voltage source is used for controlling droop according to the voltage u of the power grid_gabcActual output active power P of inverter_eAnd reactive power Q_eGiven value P of active power of inverter_refAnd given value of reactive power Q_refAnd the voltage amplitude U of the power grid_gmGiven value of voltage amplitude value U_nAnd calculating to obtain an inner ring current reference i in a voltage source operation mode_{ref_abc_vir}；

The current inner loop control module 10 responds to different operation mode control instructions, and signals gated after passing through the gating switch S are accessed to the inner loop current reference i in the current source operation mode_{ref_abc}Or inner loop current reference i in voltage source operation mode_{ref_abc_vir}And an inverter output current i_LabcAnd grid voltage phase theta_gObtaining the modulation wave V of the photovoltaic grid-connected inverter_mabc；

The pulse width modulation module 11 modulates the wave V_mabcFor carrier signal V_rAnd modulating, generating a control signal D for controlling a power switch of the photovoltaic inverter, and sending the control signal D to the inverter so that the inverter finishes a current source operation mode or a voltage source operation mode.

The MPPT and DC voltage outer loop control module, the current inner loop control module and the pulse width modulation module are traditionalAnd the actual power calculation module, the droop control of the self-synchronizing voltage source and the virtual impedance control module are realized by an external embedded controller. Under normal working conditions, the photovoltaic inverter operates in an MPPT mode, and the inner ring current reference is an inner ring current reference i under a current source operation mode_{ref_abc}(ii) a When the photovoltaic grid-connected inverter receives a signal of a station control system and needs to operate in a voltage source mode, the inner ring current reference is switched to be the inner ring current reference i in the voltage source operation mode_{ref_abc_vir}。

The gating switch S in the embodiment of the invention can adopt a logic gating switch in the prior art, and the gating signal can be manually controlled by an upper computer or automatically controlled by a system. When the inverter works in the current source operation mode, the gating switch S gates the inner-loop current reference i in the current source operation mode_{ref_abc}Connecting a current inner ring control module; when the inverter operates in the voltage source operation mode, the gating switch S gates the inner loop current reference i in the voltage source operation mode_{ref_abc_vir}And connecting the current inner ring control module.

The device of the invention is mainly implemented as follows:

when the photovoltaic grid-connected inverter works in a current source operation mode, firstly, the grid voltage u obtained through sampling_gabcSending into PLL phase-locked module 6, calculating power grid voltage amplitude U by PLL phase-locked module 6 based on phase-locked loop algorithm in prior art_gmAnd grid voltage phase theta_gThen the inverter DC voltage U obtained by sampling_dcAnd the DC current I of the inverter_dcSending the current to an MPPT and DC voltage outer ring control module 7, and obtaining an inner ring current reference i under a current source operation mode by the MPPT and DC voltage outer ring control module 7 according to MPPT control and DC voltage outer ring PI control_{ref_abc}(ii) a Inner loop current reference i in gating switch S gating current source operation mode_{ref_abc}Sampling to obtain the output current i of the inverter_LabcAnd grid voltage phase theta_gThe current is sent to a current control module 10, and a grid-connected inverter modulation wave V under the current source control scheme is obtained through calculation_mabc(ii) a The obtained modulated wave V_mabcInput pulse width modulation module 11, for carrierSignal V_rAnd modulating to generate a control signal D for controlling the inverter power switch. The control signal D controls the on-off of a power switch device in the inverter, the amplitude, the frequency and the phase of alternating voltage can be adjusted, the output current of the alternating voltage is enabled to be synchronous with the phase and the frequency of the voltage of a power grid, and the inverter works in a current source operation mode at the moment.

The MPPT in the MPPT and dc voltage outer loop control module 7 is controlled by a hill climbing method, the dc voltage outer loop is controlled by a PI, and the specific calculation formula is as follows:

in the formula: u shape_dcrefDC voltage i corresponding to maximum power point for photovoltaic array working after MPPT control_{ref_abc_d}、i_{ref_abc_q}Current reference i in current source mode_{ref_abc}Dq component, K, in a two-phase rotating coordinate system_pv、K_ivThe outer ring PI parameter of the direct current voltage is obtained;

the current inner loop control module 10 adopts a conventional grid-connected inverter control scheme, and the invention indirectly obtains a corresponding active current instruction I under a two-phase rotating coordinate system (dq coordinate system)_drefAnd a reactive current command I_qrefThen, current closed loop regulation is carried out under two-phase rotating coordinate by feeding back inverter inductive current, and finally the regulator under the two-phase rotating coordinate system (dq coordinate system) is output M_d、M_qThree-phase modulation wave V is obtained in three-phase static coordinate system through coordinate transformation_mabc. The specific calculation formula is as follows:

wherein: i is_dref、I_qrefAre respectively inner ring current reference i_{ref_abc}Or i_{ref_abc_vir}Dq-axis component in a two-phase rotating coordinate system, I_d、I_qAre respectively the inductive current i_LabcAt two sidesDq component, K, in a phase rotation coordinate system_pi、K_iiIs the current regulator PI parameter, omega is the grid angular frequency, s is the Laplace operator, L is the main circuit filter inductance value, V_d、V_qIs u_gabcDq-axis component in a two-phase rotating coordinate system, M_d、M_qIs a dq axis modulation component under the two-phase rotating coordinate system of the inverter.

When the photovoltaic grid-connected inverter works in a voltage source operation mode, firstly, the inverter output current i obtained by sampling is used_LabcAnd the network voltage u_gabcSending the actual power calculation module 8 (the power calculation method is the prior general technology) to obtain the actual output active power P of the grid-connected inverter_eAnd reactive power Q_eThe obtained actual output active power P of the grid-connected inverter_eAnd reactive power Q_eGiven value of active power P_refAnd given value of reactive power Q_refGiven value of voltage amplitude U_nGrid voltage u_gabcAnd the PLL phase locking module 6 calculates to obtain the power grid voltage amplitude U_gmSending the voltage to a droop control and virtual impedance control module 9 of the self-synchronizing voltage source, and calculating to obtain an inner loop current reference i in a voltage source operation mode_{ref_abc_vir}(ii) a Inner loop current reference i in gated switch S-gated voltage source operating mode_{ref_abc_vir}Sampling to obtain the output current i of the inverter_LabcThe current is sent to a current control module 10, and a grid-connected inverter modulation wave V under the current source control scheme is obtained through calculation_mabc(ii) a The obtained modulated wave V_mabcInput to a pulse width modulation module 11 for a carrier signal V_rAnd modulating to generate a control signal D for controlling the inverter power switch. The control signal D is used for controlling the on-off of a power switch device in the inverter, so that the amplitude, the frequency and the phase of the alternating voltage can be adjusted, and the inverter works in a voltage source operation mode.

The calculation formula of the droop control and virtual impedance control module 9 of the self-synchronous voltage source is as follows:

in the formula: u shape_nTo a nominal voltage amplitude, D_qIs a reactive sag factor, K_qAs integral coefficient, ω_nAt a nominal angular frequency, D_pIs the active droop coefficient, J is the virtual moment of inertia, s is the Laplace operator, U_VSGAmplitude, omega, of modulated wave generated for virtual synchronous machine control_VSGModulated wave angular frequency, theta, generated for virtual synchronous machine control_VSGControlling the generated phase, U, for a virtual synchronizer_VmabcThe virtual synchronizer is used for controlling self-generated three-phase voltage, L is the inductance value of a main circuit filter, and r is the parasitic resistance of the filter inductance.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (13)

1. An operation mode control system suitable for a current source photovoltaic grid-connected inverter, characterized in that it comprises a DC voltage measurement module, a DC current measurement module, an AC current measurement module, an AC voltage measurement module, and a PLL phase locking module , MPPT and DC voltage outer loop control module, current inner loop control module, pulse width modulation module, actual power calculation module and self-synchronized voltage source droop control and virtual impedance control module; The DC voltage measurement module collects the inverter DC voltage U _dc and outputs it to the MPPT and the DC voltage outer loop control module; The DC current measurement module collects the inverter DC current I _dc and outputs it to the MPPT and the DC voltage outer loop control module; The AC current measurement module collects the inverter output current i _Labc and outputs it to the actual power calculation module and the current inner loop control module; The AC voltage measurement module collects the grid voltage u _gabc and outputs it to the PLL phase locking module, the actual power calculation module, the self-synchronized voltage source droop control and the virtual impedance control module; The PLL phase locking module calculates the grid voltage amplitude U _gm and the grid voltage phase θ _g according to the grid voltage u _gabc ; The MPPT and the DC voltage outer loop control module calculates the inner loop current reference i _{ref_abc} in the current source operation mode according to the inverter DC voltage U _dc and the inverter DC current I _dc ; The actual power calculation module calculates and obtains the actual output active power P _e and reactive power Q _e of the inverter according to the inverter output current i _Labc and the grid voltage u _gabc ; The self-synchronized voltage source droop control and virtual impedance control module is based on the grid voltage u _gabc , the actual output active power P _e and reactive power Q _e of the inverter, the inverter active power given value P _ref and the reactive power supply The fixed value Q _ref , the grid voltage amplitude U _gm , and the voltage amplitude given value U _n are calculated to obtain the inner loop current reference i _{ref_abc_vir} in the voltage source operation mode; The current inner loop control module is connected to the inner loop current reference i _{ref_abc} in the current source operation mode or the inner loop current in the voltage source operation mode in response to different operation mode control commands and in combination with the gating signal output by the gating switch S. With reference to i _{ref_abc_vir} , as well as the inverter output current i _Labc and the grid voltage phase θ _g , obtain the photovoltaic grid-connected inverter modulation wave V _mabc ; The pulse width modulation module modulates the carrier signal V _r with the modulated wave V _mabc to generate a control signal D for controlling the power switch of the photovoltaic inverter, and sends it to the inverter, so that the inverter completes the control of the operation mode. 2 . The operation mode control system suitable for a current source photovoltaic grid-connected inverter according to claim 1 , wherein the calculation formula of the inner loop current reference i _{ref_abc} in the current source operation mode is: 2 .

In the formula: U _dcref is the DC voltage corresponding to the maximum power point of the photovoltaic array after MPPT control, i _{ref_abc_d} , i _{ref_abc_q in the} current source mode, the current reference i _{ref_abc} in the two-phase rotating coordinate system dq-axis components, K _pv , K _iv is the DC voltage outer loop PI parameter. 3 . The operation mode control system suitable for a current source photovoltaic grid-connected inverter according to claim 1 , wherein the calculation formula of the inner loop current reference i _{ref_abc_vir} in the voltage source operation mode is: 3 .

Where: U _n is the rated voltage amplitude, D _q is the reactive power droop coefficient, K _q is the integral coefficient, ω _n is the rated angular frequency, D _p is the active power droop coefficient, J is the virtual moment of inertia, s is the Laplace U _VSG is the modulation wave amplitude value generated by the virtual synchronous machine control, ω _VSG is the modulation wave angular frequency generated by the virtual synchronous machine control, θ _VSG is the phase generated by the virtual synchronous machine control, and U _Vmabc is the virtual synchronous machine control. Self-generated three-phase voltage, L is the main circuit filter inductance value, r is the filter inductance parasitic resistance. 4 . The operation mode control system suitable for a current source photovoltaic grid-connected inverter according to claim 1 , wherein the calculation formula of the inverter modulation wave V _mabc is: 4 .

Among them: I _dref and I _qref are respectively the dq-axis components of the inner loop current reference i _{ref_abc} or i _{ref_abc_vir} in the two-phase rotating coordinate system, and I _d and I _q are respectively the dq of the inductor current i _Labc in the two-phase rotating coordinate system Shaft component, K _pi , K _ii are the PI parameters of the current regulator, ω is the grid angular frequency, s is the Laplace operator, L is the inductance value of the main circuit filter, V _d , V _q are the u _gabc in the two-phase The dq-axis components in the rotating coordinate system, M _d and M _q are the dq-axis modulation components in the two-phase rotating coordinate system of the inverter. 5. An operation mode control method suitable for a current source photovoltaic grid-connected inverter, characterized in that it comprises: Based on the inverter DC current I _dc and the DC voltage U _dc , calculate the inner loop current reference i _{ref_abc} in the current source operation mode; Based on the grid voltage u _gabc , the grid voltage amplitude U _gm and the grid voltage phase θ _g are calculated; Calculate the actual output active power P _e and reactive power Q _e of the inverter based on the inverter output current i _Labc and the grid voltage u _gabc ; Based on grid voltage u _gabc , inverter actual output active power Pe and reactive power _{Q e ,} grid voltage amplitude U _gm , inverter active power given value P _ref and reactive power given value Q _ref , voltage Amplitude given value U _n , calculate the inner loop current reference i _{ref_abc_vir} in voltage source operation mode; In response to different operating mode control commands, the inner loop current reference i ref_abc in the current source operating mode or the inner loop current reference i _{ref_abc_vir} in the voltage source operating mode is _connected , and is calculated by combining the inverter output current i _Labc and the grid voltage phase θ _g The inverter modulated wave V _mabc is output, the carrier signal V _r is modulated, a control signal D for controlling the power switch of the inverter is generated, and sent to the inverter, so that the inverter completes the control of the operation mode. 6 . The operation mode control method suitable for a current source photovoltaic grid-connected inverter according to claim 5 , wherein the calculation formula of the inner loop current reference i _{ref_abc} in the current source operation mode is: 6 .

In the formula: U _dcref is the DC voltage corresponding to the maximum power point of the photovoltaic array after MPPT control, i _{ref_abc_d} , i _{ref_abc_q} are the dq-axis components of the current reference i _{ref_abc} in the two-phase rotating coordinate system in the current source mode, K _pv , K _iv is the DC voltage outer loop PI parameter. 7 . The operation mode control method suitable for a current source photovoltaic grid-connected inverter according to claim 5 , wherein the calculation formula of the inner loop current reference i _{ref_abc_vir} in the voltage source operation mode is: 8 .

Where: U _n is the rated voltage amplitude, D _q is the reactive power droop coefficient, K _q is the integral coefficient, ω _n is the rated angular frequency, D _p is the active power droop coefficient, J is the virtual moment of inertia, s is the Laplace U _VSG is the modulation wave amplitude value generated by the virtual synchronous machine control, ω _VSG is the modulation wave angular frequency generated by the virtual synchronous machine control, θ _VSG is the phase generated by the virtual synchronous machine control, and U _Vmabc is the virtual synchronous machine control. Self-generated three-phase voltage, L is the main circuit filter inductance value, r is the filter inductance parasitic resistance. 8 . The operation mode control method suitable for a current source photovoltaic grid-connected inverter according to claim 5 , wherein the calculation formula of the inverter modulation wave V _mabc is: 8 .

Among them: I _dref and I _qref are respectively the dq-axis components of the inner loop current reference i _{ref_abc} or i _{ref_abc_vir} in the two-phase rotating coordinate system, and I _d and I _q are respectively the dq of the inductor current i _Labc in the two-phase rotating coordinate system Shaft component, K _pi , K _ii are the PI parameters of the current regulator, ω is the grid angular frequency, s is the Laplace operator, L is the inductance value of the main circuit filter, V _d , V _q are the u _gabc in the two-phase The dq-axis components in the rotating coordinate system, M _d and M _q are the dq-axis modulation components in the two-phase rotating coordinate system of the inverter. 9. An operation mode control device suitable for a current source photovoltaic grid-connected inverter, characterized in that it comprises: a first calculation module, configured to calculate the inner loop current reference i _{ref_abc} in the current source operation mode based on the inverter DC current I _dc and the DC voltage U _dc ; a second calculation module, configured to calculate the grid voltage amplitude U _gm and the grid voltage phase θ _g based on the grid voltage u _gabc ; The third calculation module is used to calculate the actual output active power Pe and reactive power Q _e of the inverter based on the inverter output current i _Labc and the grid voltage u _{gabc ;} The fourth calculation module is configured to be based on the grid voltage u _gabc , the actual output active power Pe and reactive power Q _e of the inverter _, the grid voltage amplitude U _gm , the inverter active power given value P _ref and the reactive power The given value Q _ref and the given voltage amplitude value U _n are used to calculate the inner loop current reference i _{ref_abc_vir} in the voltage source operation mode; The control module is used for responding to different operating mode control commands, accessing the inner loop current reference i _{ref_abc} in the current source operating mode or the inner loop current reference i _{ref_abc_vir} in the voltage source operating mode, combined with the inverter output current i _Labc and the grid The voltage phase θ _g calculates the inverter modulation wave V _mabc , modulates the carrier signal V _r , generates a control signal D that controls the power switch of the inverter, and sends it to the inverter, so that the inverter completes the control of the operating mode . 10 . The operation mode control device suitable for a current source photovoltaic grid-connected inverter according to claim 9 , wherein the calculation formula of the inner loop current reference i _{ref_abc} in the current source operation mode is: 10 .

In the formula: U _dcref is the DC voltage corresponding to the maximum power point of the photovoltaic array after MPPT control, i _{ref_abc_d} , i _{ref_abc_q in the} current source mode, the current reference i _{ref_abc} in the two-phase rotating coordinate system dq-axis components, K _pv , K _iv is the DC voltage outer loop PI parameter. 11 . The operation mode control device suitable for a current source photovoltaic grid-connected inverter according to claim 9 , wherein the calculation formula of the inner loop current reference i _{ref_abc_vir} in the voltage source operation mode is: 11 .

Where: U _n is the rated voltage amplitude, D _q is the reactive power droop coefficient, K _q is the integral coefficient, ω _n is the rated angular frequency, D _p is the active power droop coefficient, J is the virtual moment of inertia, s is the Laplace U _VSG is the modulation wave amplitude value generated by the virtual synchronous machine control, ω _VSG is the modulation wave angular frequency generated by the virtual synchronous machine control, θ _VSG is the phase generated by the virtual synchronous machine control, and U _Vmabc is the virtual synchronous machine control. Self-generated three-phase voltage, L is the main circuit filter inductance value, r is the filter inductance parasitic resistance. 12 . The operating mode control device suitable for a current source photovoltaic grid-connected inverter according to claim 9 , wherein the calculation formula of the inverter modulation wave V _mabc is: 12 .

Among them: I _dref and I _qref are respectively the dq-axis components of the inner loop current reference i _{ref_abc} or i _{ref_abc_vir} in the two-phase rotating coordinate system, and I _d and I _q are respectively the dq of the inductor current i _Labc in the two-phase rotating coordinate system Shaft component, K _pi , K _ii are the PI parameters of the current regulator, ω is the grid angular frequency, s is the Laplace operator, L is the inductance value of the main circuit filter, V _d , V _q are the u _gabc in the two-phase The dq-axis components in the rotating coordinate system, M _d and M _q are the dq-axis modulation components in the two-phase rotating coordinate system of the inverter. 13. An operation mode control system suitable for a current source photovoltaic grid-connected inverter, characterized in that it comprises a storage medium and a processor; the storage medium is used to store instructions; The processor is adapted to operate in accordance with the instructions to perform a method according to any of claims 5-8.

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