Microgrid multi-source coordination control system based on time synchronization

Abstract

The invention discloses a micro-grid multi-source coordinated control system based on time synchronization, belongs to the field of micro-grid regulation and control, and aims to solve the problems that an existing control method cannot realize coordinated control of multiple inverter devices and distributed power generation and is poor in control stability. The phasor measurement unit is used for collecting bus voltage and sending the bus voltage to the control module on each distributed power supply; the control module is also used for providing pulse per second for the control module on each distributed power supply and controlling the control module on each distributed power supply to synchronously output a PWM (Pulse-Width Modulation) signal; the control module is used for converting the bus voltage into a two-axis reference voltage and converting the two-axis reference voltage into a two-axis reference current; and the control module is also used for collecting three-phase actual current output by each distributed power supply, converting the three-phase actual current into two-axis actual current, and outputting a PWM (Pulse Width Modulation) signal to act on an inverter of each distributed power supply according to the two-axis actual current and the two-axis reference current, so as to adjust the output voltage of the inverter on each distributed power supply. The method is used for micro-grid regulation and control.

Description

Technical Field

[0001] The present invention belongs to the field of microgrid regulation and control, and relates to the regulation and control of a microgrid. Background Art

[0002] As microgrid systems become increasingly complex and large-scale, their distributed power sources and load types become increasingly diverse, and the requirements for power supply reliability and power quality continue to increase, which puts higher demands on the operation and control technology of microgrids. Therefore, developing advanced microgrid operation and control technology and improving its stability and reliability have become key issues that need to be urgently addressed, and are also an important part of promoting the green and low-carbon transformation of the economy and sustainable development.

[0003] The existing control method for island operation of new energy microgrids adopts constant voltage and frequency (V / f) control, which cannot achieve coordinated control of multiple inverter devices and distributed generation;

[0004] However, the traditional peer-to-peer control method is complex and has problems with frequency stability and power oscillation.

[0005] The existing control methods for switching between on-grid and off-grid operation modes of new energy microgrids generally have problems such as complex switching algorithms, slow switching speeds, poor dynamic performance, and difficulty in effectively avoiding impact currents.

[0006] The current controllable resource operation methods based on fixed-time charging and discharging or fixed historical load curves are difficult to adapt to the random fluctuations of renewable energy output and load, affecting the reliability and economy of renewable energy microgrid operation.

[0007] Therefore, based on the existing new energy microgrid island operation control method, it is impossible to achieve coordinated control of multiple inverter devices and distributed power generation. The traditional peer control method, the controllable resource operation method based on fixed time charging and discharging or based on a fixed historical load curve, and the new energy microgrid island operation control method have poor stability. It is urgent to carry out research on key technologies of power electronics new energy microgrid autonomy and flexible grid connection and form demonstration applications to solve the safety, stability and economic operation problems brought about by large-scale access of distributed resources on the distribution side. Summary of the invention

[0008] The purpose of the present invention is to solve the problem that the existing control method cannot achieve coordinated control of multiple inverter devices and distributed power generation and has poor control stability, and proposes a microgrid multi-source coordinated control system based on time synchronization.

[0009] A microgrid multi-source coordinated control system based on time synchronization, the system comprising a plurality of control modules and a phasor measurement unit;

[0010] Phase measurement unit, used to collect bus voltage u pccIt is sent to the control module on each distributed power source; it is also used to provide second pulses for the control modules on each distributed power source, and control the control modules on each distributed power source to synchronously output PWM signals;

[0011] Control module, used to convert bus voltage u pcc It is converted into a two-axis reference voltage, and the two-axis reference voltage is converted into a two-axis reference current. It is also used to collect the three-phase actual current output by each distributed power source and convert it into a two-axis actual current. According to the two-axis actual current and the two-axis reference current, a PWM signal is output to act on the inverter of each distributed power source to adjust the output voltage of the inverter on each distributed power source.

[0012] Preferably, each control module includes a Parker converter, a No. 1 Parker inverse converter, a No. 2 Parker inverse converter, an IU droop controller, a current loop and an SPWM module;

[0013] Parker converter, used to receive bus voltage u pcc Transform the coordinate system to obtain the reference voltage u on the d-axis dpcc and the reference voltage u on the q axis qpcc Send to IU droop controller;

[0014] The IU droop controller is used to adjust the reference voltage u on the d-axis dpcc Converted to the reference current i on the d-axis dref The reference voltage u on the q axis is sent into the current loop. qpcc Converted to the reference current i on the q axis qref Feed into the current loop;

[0015] The No. 1 Parker inverse converter is used to transform the coordinate system of the three-phase actual current output by each distributed power source, and output the actual current i on the q axis after the transformation. 1q and the actual current i on the d-axis after transformation 1d Feed into the current loop;

[0016] The current loop is used to calculate the reference current i on the d-axis. dref , the actual current i on the d-axis 1d , the reference current i on the q axis qref and the actual current i on the q axis 1q The output control voltage is sent to the second Park inverse transformer;

[0017] The second Parker inverse converter is used to convert the control voltage into a coordinate system, and the output transformed control voltage is sent to the SPWM module;

[0018] The SPWM module is used to generate a PWM signal according to the converted control voltage and apply it to the inverter of the distributed power source to adjust the output voltage of the inverter on the distributed power source.

[0019] Preferably, the IU droop controller comprises a first droop control module and a second droop control module;

[0020] Droop control module No. 1, used to calculate the reference voltage u on the d-axis dpcc The difference between the preset d-axis voltage and the reference current i on the d-axis is output through the d-axis droop link. dref ;

[0021] The second droop control module is used to calculate the reference voltage u on the q axis qpcc The difference between the preset q-axis voltage and the reference current i on the q-axis is output through the q-axis droop link. qref .

[0022] Preferably, the d-axis droop link is: 1 / r d , r d is the d-axis droop coefficient.

[0023] Preferably, the q-axis droop link is: 1 / r q , r q is the q-axis droop coefficient.

[0024] Preferably, the current loop includes a No. 1 current control module and a No. 2 current control module;

[0025] The first current control module is used to receive the q-axis harmonic voltage u oq Convert it into q-axis harmonic current, and convert the q-axis harmonic current and the reference current i on the d-axis dref and the actual current i on the d-axis 1d The difference is adjusted by the No. 1 proportional adjustment and No. 1 integral link respectively, and the difference between the two outputs is calculated. The difference is the actual voltage of the q-axis and the harmonic voltage u of the d-axis after transformation. od The actual voltage on the q-axis after transformation is calculated by the actual current i on the q-axis. 1q Transformation acquisition;

[0026] The second current control module is used to control the received d-axis harmonic voltage u od Convert it into d-axis harmonic current, and convert the d-axis harmonic current and the reference current i on the q-axis qref and the actual current i on the q axis 1q The difference is adjusted by the second integral link and the second proportional link respectively, and the output of the two is subtracted. The difference is compared with the transformed d-axis actual voltage and q-axis harmonic voltage u oq The actual voltage on the d-axis after transformation is calculated by the actual current i on the d-axis. 1d Transformation obtained.

[0027] Preferably, the q-axis harmonic voltage u oq The conversion into q-axis harmonic current is achieved by:

[0028] The q-axis harmonic voltage u oq Multiplying by ωC, we get the q-axis harmonic current, where ω is the angular frequency and C is the capacitance;

[0029] d-axis harmonic voltage u od The conversion into d-axis harmonic current is achieved by:

[0030] The d-axis harmonic voltage u od Multiplying by ωC, we get the d-axis harmonic current.

[0031] Preferably, the implementation method of obtaining the transformed actual q-axis voltage is:

[0032] The actual current i on the q axis 1q With ωL f Multiply them to get the transformed actual voltage on the q axis, ω is the angular frequency, L f is the inductor;

[0033] The implementation method of obtaining the transformed actual voltage of the d-axis is:

[0034] The actual current i on the d-axis 1d With ωL f Multiply them to get the transformed actual d-axis voltage.

[0035] Preferably, the first integral link and the second integral link are both expressed as: k i / s,k i is the integral coefficient and s is the Laplace transform.

[0036] The beneficial effects of the present invention are:

[0037] The present invention utilizes the PMU (Phasor Measurement Unit) satellite timing signal pulse per second (PPS) to enable the inverter to generate a sinusoidal current with a phase of zero (relative to the synchronous clock signal) and a frequency fixed to the industrial frequency (50Hz), and controls the control modules on each distributed power source to synchronously output a PWM signal, thereby realizing synchronous control of each distributed power source and solving the problem that the use of droop control may cause frequency deviation and inaccurate power distribution when the microgrid is operating in an isolated island.

[0038] The present invention adopts vector control based on current loop to make each inverter in the microgrid output power frequency current with consistent phase and adjustable amplitude, and the control of the present invention is more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is the principle block diagram of the multi-source coordinated control system of microgrid based on time synchronization;

[0040] Figure 2 This is the schematic diagram of the IU droop controller and current loop. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0043] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0044] Example:

[0045] Combination Figure 1 and Figure 2 This embodiment describes a microgrid multi-source coordinated control system based on time synchronization, wherein the system includes a plurality of control modules and a phasor measurement unit;

[0046] Phase measurement unit, used to collect bus voltage u pcc It is sent to the control module on each distributed power source; it is also used to provide second pulses for the control modules on each distributed power source, and control the control modules on each distributed power source to synchronously output PWM signals;

[0047] Control module, used to convert bus voltage u pcc It is converted into a two-axis reference voltage, and the two-axis reference voltage is converted into a two-axis reference current. It is also used to collect the three-phase actual current output by each distributed power source and convert it into a two-axis actual current. According to the two-axis actual current and the two-axis reference current, a PWM signal is output to act on the inverter of each distributed power source to adjust the output voltage of the inverter on each distributed power source.

[0048] Specifically, Figure 1 The function of synchronous rotation phase angle calculation is to enable the Parker converter to generate the real-time rotation phase angle of the unified reference coordinate system.

[0049] The following describes the composition of the control modules: Each control module includes a Parker converter, a Parker inverter No. 1, a Parker inverter No. 2, an IU droop controller, a current loop and an SPWM module;

[0050] Parker converter, used to receive bus voltage u pccTransform the coordinate system to obtain the reference voltage u on the d-axis dpcc and the reference voltage u on the q axis qpcc Send to IU droop controller;

[0051] The IU droop controller is used to adjust the reference voltage u on the d-axis dpcc Converted to the reference current i on the d-axis dref The reference voltage u on the q axis is sent into the current loop. qpcc Converted to the reference current i on the q axis qref Feed into the current loop;

[0052] The No. 1 Parker inverse converter is used to transform the coordinate system of the three-phase actual current output by each distributed power source, and output the actual current i on the q axis after the transformation. 1q and the actual current i on the d-axis after transformation 1d Feed into the current loop;

[0053] The current loop is used to calculate the reference current i on the d-axis. dref , the actual current i on the d-axis 1d , the reference current i on the q axis qref and the actual current i on the q axis 1q The output control voltage is sent to the second Park inverse transformer;

[0054] The second Parker inverse converter is used to convert the control voltage into a coordinate system, and the output transformed control voltage is sent to the SPWM module;

[0055] The SPWM module is used to generate a PWM signal according to the converted control voltage and apply it to the inverter of the distributed power source to adjust the output voltage of the inverter on the distributed power source.

[0056] The following introduces the composition of the IU droop controller: The IU droop controller includes a No. 1 droop control module and a No. 2 droop control module;

[0057] Droop control module No. 1, used to calculate the reference voltage u on the d-axis dpcc The difference between the preset d-axis voltage and the reference current i on the d-axis is output through the d-axis droop link. dref ;

[0058] The second droop control module is used to calculate the reference voltage u on the q axis qpcc The difference between the preset q-axis voltage and the reference current i on the q-axis is output through the q-axis droop link. qref .

[0059] The following introduces the d-axis droop link: The d-axis droop link is: 1 / r d , r dis the d-axis droop coefficient.

[0060] The following introduces the q-axis droop link: The q-axis droop link is: 1 / r q , r q is the q-axis droop coefficient.

[0061] The current loop composition is introduced below: the current loop includes a No. 1 current control module and a No. 2 current control module;

[0062] The first current control module is used to receive the q-axis harmonic voltage u oq Convert it into q-axis harmonic current, and convert the q-axis harmonic current and the reference current i on the d-axis dref and the actual current i on the d-axis 1d The difference is adjusted by the No. 1 proportional adjustment and No. 1 integral link respectively, and the difference between the two outputs is calculated. The difference is the actual voltage of the q-axis and the harmonic voltage u of the d-axis after transformation. od The actual voltage on the q-axis after transformation is calculated by the actual current i on the q-axis. 1q Transformation acquisition;

[0063] The second current control module is used to control the received d-axis harmonic voltage u od Convert it into d-axis harmonic current, and convert the d-axis harmonic current and the reference current i on the q-axis qref and the actual current i on the q axis 1q The difference is adjusted by the second integral link and the second proportional link respectively, and the output of the two is subtracted. The difference is compared with the transformed d-axis actual voltage and q-axis harmonic voltage u oq The actual voltage on the d-axis after transformation is calculated by the actual current i on the d-axis. 1d Transformation obtained.

[0064] The following describes the transformation method: q-axis harmonic voltage u oq The conversion into q-axis harmonic current is achieved by:

[0065] The q-axis harmonic voltage u oq Multiplying by ωC, we get the q-axis harmonic current, where ω is the angular frequency and C is the capacitance;

[0066] d-axis harmonic voltage u od The conversion into d-axis harmonic current is achieved by:

[0067] The d-axis harmonic voltage u od Multiplying by ωC, we get the d-axis harmonic current.

[0068] The following describes the transformation method: the method for obtaining the actual voltage of the q-axis after the transformation:

[0069] The actual current i on the q axis1q With ωL f Multiply them to get the transformed actual voltage on the q axis, ω is the angular frequency, L f is the inductor;

[0070] The implementation method of obtaining the transformed actual voltage of the d-axis is:

[0071] The actual current i on the d-axis 1d With ωL f Multiply them to get the transformed actual d-axis voltage.

[0072] The following introduces the representation of the first integral link and the second integral link: The first integral link and the second integral link are both represented as: k i / s,k i is the integral coefficient and s is the Laplace transform.

[0073] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A microgrid multi-source coordinated control system based on time synchronization, characterized in that: The system includes a plurality of control modules and a phasor measurement unit; Phase measurement unit, used to collect bus voltage u pcc It is sent to the control module on each distributed power source; it is also used to provide second pulses for the control modules on each distributed power source, and control the control modules on each distributed power source to synchronously output PWM signals; Control module, used to convert bus voltage u pcc It is converted into a two-axis reference voltage, and the two-axis reference voltage is converted into a two-axis reference current. It is also used to collect the three-phase actual current output by each distributed power source and convert it into a two-axis actual current. According to the two-axis actual current and the two-axis reference current, a PWM signal is output to act on the inverter of each distributed power source to adjust the output voltage of the inverter on each distributed power source.

2. The microgrid multi-source coordinated control system based on time synchronization according to claim 1 is characterized in that: Each control module includes a Parker converter, a Parker inverter No. 1, a Parker inverter No. 2, an IU droop controller, a current loop and an SPWM module; Parker converter, used to receive bus voltage u pcc Transform the coordinate system to obtain the reference voltage u on the d-axis dpcc and the reference voltage u on the q axis qpcc Send to IU droop controller; The IU droop controller is used to adjust the reference voltage u on the d-axis dpcc Converted to the reference current i on the d-axis dref The reference voltage u on the q axis is sent into the current loop. qpcc Converted to the reference current i on the q axis qref Feed into the current loop; The No. 1 Parker inverse converter is used to transform the coordinate system of the three-phase actual current output by each distributed power source, and output the actual current i on the q axis after the transformation. 1q and the actual current i on the transformed d-axis 1d Feed into the current loop; The current loop is used to calculate the reference current i on the d-axis. dref , the actual current i on the d-axis 1d , the reference current i on the q axis qref and the actual current i on the q axis 1q The output control voltage is sent to the second Park inverse transformer; The second Parker inverse converter is used to convert the control voltage into a coordinate system, and the output transformed control voltage is sent to the SPWM module; The SPWM module is used to generate a PWM signal according to the converted control voltage and apply it to the inverter of the distributed power source to adjust the output voltage of the inverter on the distributed power source.

3. The microgrid multi-source coordinated control system based on time synchronization according to claim 2 is characterized in that: The IU droop controller includes a No. 1 droop control module and a No. 2 droop control module; Droop control module No. 1, used to calculate the reference voltage u on the d-axis dpcc The difference between the preset d-axis voltage and the reference current i on the d-axis is output through the d-axis droop link. dref ; The second droop control module is used to calculate the reference voltage u on the q axis qpcc The difference between the preset q-axis voltage and the reference current i on the q-axis is output through the q-axis droop link. qref .

4. The microgrid multi-source coordinated control system based on time synchronization according to claim 3 is characterized in that: The d-axis droop link is: 1 / r d , r d is the d-axis droop coefficient.

5. The microgrid multi-source coordinated control system based on time synchronization according to claim 3 is characterized in that: The q-axis droop link is: 1 / r q , r q is the q-axis droop coefficient.

6. The microgrid multi-source coordinated control system based on time synchronization according to claim 2 is characterized in that: The current loop includes a No. 1 current control module and a No. 2 current control module; The first current control module is used to receive the q-axis harmonic voltage u oq Convert it into q-axis harmonic current, and convert the q-axis harmonic current and the reference current i on the d-axis dref and the actual current i on the d-axis 1d The difference is adjusted by the No. 1 proportional regulator and the No. 1 integral regulator respectively, and the difference between the two outputs is calculated. The difference is the actual voltage of the q-axis and the harmonic voltage u of the d-axis after transformation. od The actual voltage on the q-axis after transformation is calculated by the actual current i on the q-axis. 1q Transformation obtained; The second current control module is used to control the received d-axis harmonic voltage u od Convert it into d-axis harmonic current, and convert the d-axis harmonic current and the reference current i on the q-axis qref and the actual current i on the q axis 1q The difference is adjusted by the second integral link and the second proportional link respectively, and the output of the two is subtracted. The difference is compared with the transformed d-axis actual voltage and q-axis harmonic voltage u oq The actual voltage on the d-axis after transformation is calculated by the actual current i on the d-axis. 1d Transformation obtained.

7. The microgrid multi-source coordinated control system based on time synchronization according to claim 6 is characterized in that: q-axis harmonic voltage u oq The conversion into q-axis harmonic current is achieved by: The q-axis harmonic voltage u oq Multiplying by ωC, we get the q-axis harmonic current, where ω is the angular frequency and C is the capacitance; d-axis harmonic voltage u od The conversion into d-axis harmonic current is achieved by: The d-axis harmonic voltage u od Multiplying by ωC, we get the d-axis harmonic current.

8. The microgrid multi-source coordinated control system based on time synchronization according to claim 6 is characterized in that: The implementation method of obtaining the transformed actual voltage of the q-axis is: The actual current i on the q axis 1q With ωL f Multiply them to get the transformed actual voltage on the q axis, ω is the angular frequency, L f is the inductor; The implementation method of obtaining the transformed actual voltage of the d-axis is: The actual current i on the d-axis 1d With ωL f Multiply them to get the transformed actual d-axis voltage.

9. The microgrid multi-source coordinated control system based on time synchronization according to claim 6, characterized in that: Both the first integral link and the second integral link are expressed as: k i / s,k i is the integral coefficient and s is the Laplace transform.

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