CN107332282B - Micro-grid pre-synchronization grid-connected control system and control method thereof - Google Patents
Micro-grid pre-synchronization grid-connected control system and control method thereof Download PDFInfo
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Abstract
A micro-grid pre-synchronization grid-connected control system comprises a frequency adjusting module, an SPLL phase-locked loop module, a voltage adjusting module, a phase generating module, a phase adjusting module and a PWM signal generator module; the presynchronization control method mainly comprises the steps of recording the working state in the grid-connected operation stage, controlling the mode in a proportional-integral mode during mode switching, adjusting the phase based on linear gradual approximation, and completing the adjustment of the voltage amplitude, the frequency and the phase of the microgrid; the advantages are that the stability of power supply quality is improved; realizing rapid error-free control; the speed of the phase ramp-up can be adjusted.
Description
The technical field is as follows:
the invention relates to the field of micro-grids or distributed power generation systems, in particular to a micro-grid pre-synchronization grid-connected control system and a working method thereof.
(II) background technology:
distributed power generation technology has gained rapid development in recent years, and has attracted more and more attention from people because of its characteristics such as little pollution, high energy utilization rate, flexible application, etc. Distributed power generation is connected to a main power grid in a micro-grid mode, various distributed power sources, energy storage units, power loads, a management control system and the like are combined together, the distributed power generation can work independently and can be used as electric energy support of the main power grid, and the distributed power generation system plays an increasingly important role in an intelligent power grid system in the future. However, it is because the idea of distributed power generation is in the root of the power system, so that the effect of distributed power generation on the system becomes more non-negligible.
The operation capability of the grid-connected state and the island state is the key for the micro grid to exert the advantages of the micro grid, and the stable operation under the dual modes, especially the smooth switching between the two modes, becomes one of the primary technologies for ensuring the smooth transition of the micro grid between the grid-connected mode and the island mode. If smooth switching cannot be realized, the power supply quality of the microgrid and the main power grid may be seriously affected.
Regarding the control strategy in the switching process of the working mode, it is difficult to achieve a good effect by only using a certain control strategy. Therefore, some new control strategy or control technique must be applied in the actual process. At present, many results have been obtained in the research on the working process, but most of the work is still in the experimental research stage, and particularly, the phase synchronization problem before grid connection is not well solved.
(III) the invention content:
the invention aims to provide a micro-grid pre-synchronization grid-connected control system and a working method thereof, which can overcome the defects of the prior art and are pre-synchronization control and a working method thereof with simple structure, easy realization and strong operability.
The technical scheme of the invention is as follows: a microgrid pre-synchronization grid-connected control system comprises a main power grid and is characterized by comprising a frequency adjusting module, an SPLL (Software Phase-Locked Loop) Phase-Locked Loop module, a voltage adjusting module, a Phase generating module, a Phase adjusting module and a PWM (Pulse Width Modulation) signal generator module; the input end of the frequency adjusting module is connected with a main power grid, the active power at a microgrid grid-connected point and a reference value signal of the active power of the control system are collected, and the output end of the frequency adjusting module is connected with the input end of the phase generating module; the input end of the voltage regulating module is connected with a main power grid, the reference value signals of reactive power at the grid-connected point of the microgrid and reactive power of the control system are collected, and the output end of the voltage regulating module is connected with the input end of the PWM signal generator module; the input end of the SPLL phase-locked loop module is connected with a main power grid, the voltage signal, the frequency signal and the phase signal of the main power grid are collected, and the output end of the SPLL phase-locked loop module is respectively connected with the input ends of the phase generation module, the phase adjustment module and the PWM signal generator module; the output end of the phase generation module is respectively connected with the input ends of the phase adjustment module and the PWM signal generator module; the output end of the phase adjusting module is connected with the input end of the PWM signal generator module; and the output end of the PWM signal generator module outputs a PWM signal to control the on-off of a power electronic switch at the grid-connected position.
The frequency adjusting module consists of a proportional amplifier I, an integral adjuster I, a control switch K1 and 2 accumulators; the accumulator superposes input signals of the frequency adjusting module, namely reference value signals of active power and active power of the control system; the input end of the proportional amplifier receives the superposed signal, and the output end of the proportional amplifier outputs an amplified signal to one input end of another accumulator; the input end of the integral regulator receives a superposed signal of the active power and a reference value signal of the active power of the control system through a control switch K1, and the output end of the integral regulator is connected with a second input end of another accumulator; and the output end of the second accumulator is connected with the input ends of the phase generation module and the PWM signal generator module.
The voltage regulation module consists of a proportional amplifier II, an integral regulator II, a control switch K2 and 2 accumulators; the accumulator superposes input signals of the frequency adjusting module, namely reference value signals of reactive power and reactive power of the control system; the input end of the proportional amplifier II receives the superposed signal, and the output end of the proportional amplifier II outputs an amplified signal to one input end of another accumulator; the input end of the integral regulator II receives a superposed signal of the reactive power and a reference value signal of the reactive power of the control system through a control switch K2, and the output end of the integral regulator II is connected with the second input end of another accumulator; and the output end of the second accumulator is connected with the input ends of the phase generation module and the PWM signal generator module.
The phase adjusting module consists of a linear gradual approximation phase unit, a phase amplitude limiting unit, a control switch K3 and 2 accumulators; two input ends of the accumulator are respectively connected with the input end of the linear gradual approximation phase unit through a phase output signal of the control switch acquisition phase generation module and a main power grid phase signal acquired by the SPLL phase-locked loop module; two input ends of the second accumulator respectively receive the phase output signal of the phase generation module and the output signal of the linear gradual approximation phase unit, and the output end of the second accumulator is connected with the input end of the phase amplitude limiting unit; and the output end of the phase amplitude limiting unit is connected with the input end of the PWM signal generator module.
The linear successive approximation phase unit is a step signal generator.
A presynchronization control method of a microgrid presynchronization grid-connected control system is characterized by comprising the following steps:
(1) And in the grid-connected operation stage, the microgrid works in a droop control mode. At this stage, the SPLL phase-locked loop module is used for acquiring the frequency and the phase of a main power grid and the voltage amplitude signal of the main power grid at any time, the micro-grid pre-synchronization grid-connected control system judges the current working state, and if the working state meets the requirement of grid-connected stable working, the current voltage, frequency and phase are stored;
(2) When the mode switching of grid connection-island occurs, the micro-grid no longer acquires the voltage, frequency and phase of the main power grid, but uses the previously stored values as reference values of the micro-grid in the island operation mode; meanwhile, a droop control strategy is changed, and an integration link is added on the basis of P-f and Q-V control respectively to reduce the frequency and the deviation between the voltage and a reference value in the microgrid and realize that the power supply quality of the microgrid fluctuates in a small range;
(3) K1, K2 are control switches, when the mode switching of "being incorporated into the power networks-the island" takes place, control signal control K1 and K2 that switch over by the mode are closed, insert the control system with the integral link for original proportional control mode changes the proportional-integral control mode into, namely:
wherein f and U are respectively the frequency and voltage in droop control, P and Q are the active and reactive outputs of the system, and f 0 、U 0 、P 0 、Q 0 For each corresponding control reference value, m and n are droop coefficients, m = K pf ，n＝K pu The integral control is utilized to eliminate the static difference of the system, so that the frequency and the amplitude of the microgrid are kept in a grid-connected state as far as possibleThe stability of the power supply quality of the microgrid system is improved in the same time or within a small fluctuation range;
(4) Obtaining a frequency signal and a voltage amplitude signal after the modulation by the frequency modulation module and the voltage modulation module through the steps (1) - (3), superposing the two signals with a main power grid frequency signal and a voltage amplitude signal acquired by the SPLL phase-locked loop module respectively, and generating a frequency signal f required by the phase generation module respectively 1 And a voltage amplitude signal U required by the PWM signal generator module 1 ；
(5) The phase generation module is used for generating the frequency signal f obtained in the step (4) 1 Converting the phase signal into a phase signal theta and sending the phase signal theta to the phase adjusting module as an input signal;
(6) The phase adjusting module closes the switch K3 by the grid-connected control signal before grid connection, and acquires and stores the phases theta and theta of the microgrid and the main power grid while closing the switch K3 0 Calculating the phase difference, and comparing the phase signal theta obtained in the step (5) with the main power grid phase signal theta acquired by the SPLL phase-locked loop module 0 The adjustment is made according to the following relation;
θ 2 ＝θ+kt(θ 0 -θ)
kt is a linear function of the time series, k is a time coefficient;
(7) Will theta 2 Clipping at theta and theta 0 Get θ in between 3 The output value is the output value of the linear gradual approximation correction algorithm; the key of the linear gradual approximation phase correction algorithm is that a time series linear function kt is utilized to convert the phase difference between the microgrid and the main power grid into a function which gradually increases along with time, and the aim of adjusting the speed of the phase gradual approximation can be achieved by adjusting a time coefficient k; having such a theta 3 Generating a phase signal theta required by a PWM signal generator module by superposing theta 1 ；
(8) Combined derived voltage amplitude signal U 1 Frequency signal f 1 Phase signal theta 1 And the PWM signal generator modules are controlled together to complete the adjustment of the voltage amplitude, the frequency and the phase of the microgrid.
The step (5) is carried out by a frequency signal f 1 The conversion into the phase signal θ is composed of the following steps:
(1) will frequency signal f 1 Multiplying by 2 π to obtain an angular frequency ω 1 ；
(2) Angular frequency omega 1 Through an integration link, the phase signal is converted into a phase signal theta.
The invention has the advantages that: an integration link is added, so that the stability of the micro-grid-connected mode and the isolated island mode during mutual switching is improved; the integral control has the effect of eliminating the static difference of the system, so that the frequency and the amplitude of the microgrid are kept as same as those in a grid-connected state as possible or within a small fluctuation range, and the stability of the power supply quality of the microgrid system is improved; by adding a phase feedforward compensation link, the rapid error-free control of the phase between the microgrid and the main power grid is realized; the key of the linear gradual approximation phase correction algorithm is that the time series linear function is utilized, and the aim of adjusting the speed of the phase gradual approximation can be achieved by adjusting the time coefficient k.
(IV) description of the drawings:
fig. 1 is a block diagram of an overall structure of a micro-grid pre-synchronization grid-connected control system according to the present invention.
Fig. 2 is a block diagram of the structures of a frequency adjusting module and a voltage adjusting module in the microgrid pre-synchronization grid-connected control system according to the present invention.
Fig. 3 is a structural block diagram of a phase adjustment module in a microgrid pre-synchronization grid-connected control system according to the present invention.
Fig. 4 is a control flow schematic diagram of a pre-synchronization control method of a microgrid pre-synchronization grid-connected control system according to the present invention.
Fig. 5 is a schematic flow chart of frequency adjustment and voltage adjustment in a pre-synchronization control method of a micro-grid pre-synchronization grid-connected control system according to the present invention.
Fig. 6 is a schematic flow chart of phase adjustment in the presynchronization control method of the microgrid presynchronization grid-connected control system according to the present invention.
(V) specific embodiment:
example (b): a micro-grid pre-synchronization grid-connected control system (shown in figure 1) comprises a main grid and is characterized by comprising a frequency adjusting module, an SPLL phase-locked loop module, a voltage adjusting module, a phase generating module, a phase adjusting module and a PWM signal generator module; the input end of the frequency adjusting module is connected with a main power grid, the active power at a microgrid grid-connected point and a reference value signal of the active power of the control system are collected, and the output end of the frequency adjusting module is connected with the input end of the phase generating module; the input end of the voltage regulating module is connected with a main power grid, the reference value signals of reactive power at the grid-connected point of the microgrid and reactive power of the control system are collected, and the output end of the voltage regulating module is connected with the input end of the PWM signal generator module; the input end of the SPLL phase-locked loop module is connected with a main power grid, the voltage signal, the frequency signal and the phase signal of the main power grid are collected, and the output end of the SPLL phase-locked loop module is respectively connected with the input ends of the phase generation module, the phase adjustment module and the PWM signal generator module; the output end of the phase generation module is respectively connected with the input ends of the phase adjustment module and the PWM signal generator module; the output end of the phase adjusting module is connected with the input end of the PWM signal generator module; and the output end of the PWM signal generator module outputs a PWM signal to control the on-off of a power electronic switch at the grid-connected position.
The frequency adjusting module (see fig. 2) is composed of a proportional amplifier I, an integral adjuster I, a control switch K1 and 2 accumulators; the accumulator superposes input signals of the frequency adjusting module, namely reference value signals of active power and active power of the control system; the input end of the proportional amplifier receives the superposed signal, and the output end of the proportional amplifier outputs an amplified signal to one input end of another accumulator; the input end of the integral regulator receives a superposed signal of the active power and a reference value signal of the active power of the control system through a control switch K1, and the output end of the integral regulator is connected with a second input end of another accumulator; and the output end of the second accumulator is connected with the input ends of the phase generation module and the PWM signal generator module.
The voltage regulation module (see fig. 2) is composed of a proportional amplifier II, an integral regulator II, a control switch K2 and 2 accumulators; the accumulator superposes input signals of the frequency adjusting module, namely reference value signals of reactive power and reactive power of a control system; the input end of the proportional amplifier II receives the superposed signal, and the output end of the proportional amplifier II outputs an amplified signal to one input end of another accumulator; the input end of the integral regulator II receives a superposed signal of the reactive power and a reference value signal of the reactive power of the control system through a control switch K2, and the output end of the integral regulator II is connected with the second input end of another accumulator; and the output end of the second accumulator is connected with the input ends of the phase generation module and the PWM signal generator module.
The phase adjusting module (see fig. 3) is composed of a linear gradual approximation phase unit, a phase amplitude limiting unit, a control switch K3 and 2 accumulators; two input ends of the accumulator are respectively used for acquiring a phase output signal of the phase generation module and a main power grid phase signal acquired by the SPLL phase-locked loop module through a control switch K3, and the output end of the accumulator is connected with the input end of the linear gradual approximation phase unit; two input ends of the second accumulator respectively receive the phase output signal of the phase generation module and the output signal of the linear gradual approximation phase unit, and the output end of the second accumulator is connected with the input end of the phase amplitude limiting unit; and the output end of the phase amplitude limiting unit is connected with the input end of the PWM signal generator module.
The linear successive approximation phase unit is a step signal generator.
A presynchronization control method of a microgrid presynchronization grid-connected control system is characterized by comprising the following steps:
(1) And in the grid-connected operation stage, the microgrid works in a droop control mode. At this stage, the SPLL phase-locked loop module is used for acquiring the frequency and the phase of a main power grid and the voltage amplitude signal of the main power grid at any time, the microgrid presynchronization grid-connected control system judges the current working state, and if the working state meets the requirement of grid-connected stable work, the current voltage, frequency and phase are stored (see figure 4);
(2) When the mode switching of grid connection-island occurs, the microgrid does not acquire the voltage, frequency and phase of a main power grid, but the previously stored numerical value is used as a reference value of the microgrid in an island operation mode; meanwhile, a droop control strategy is changed, and an integration link is added on the basis of P-f and Q-V control respectively to reduce the frequency and the deviation between the voltage and a reference value in the microgrid and realize that the power supply quality of the microgrid fluctuates in a small range;
(3) K1, K2 are control switches, when the mode switching of 'being incorporated into the power networks-isolated island' takes place, control signal control K1 and K2 that switch over by the mode are closed, insert the control system with the integral link for original proportional control mode changes into proportional-integral control mode, promptly:
wherein f and U are respectively the frequency and voltage in droop control, P and Q are the active and reactive outputs of the system, and f 0 、U 0 、P 0 、Q 0 For each corresponding control reference value, m and n are droop coefficients, m = K pf ，n＝K pu The integral control is utilized to eliminate the static difference of the system, the frequency and the amplitude of the microgrid are kept as same as those in a grid-connected state as possible or within a small fluctuation range, and the stability of the power supply quality of the microgrid system is improved (see fig. 4 and 5);
(4) The frequency adjusting module and the voltage adjusting module obtain a frequency signal and a voltage amplitude signal after being modulated through the steps (1) - (3), the two signals are respectively superposed with a main power grid frequency signal and a voltage amplitude signal collected by the SPLL phase-locked loop module, and a frequency signal f required by the phase generating module is respectively generated 1 And a voltage amplitude signal U required by the PWM signal generator module 1 (see fig. 4, 5);
(5) The phase generation module is used for generating the frequency signal f obtained in the step (4) 1 Converting the phase signal into a phase signal theta and providing the phase signal theta as an input signal to a phase adjusting module (see fig. 4 and 5);
(6) The phase adjusting module closes the switch K3 by the grid-connected control signal before grid connection, and collects and stores the phases theta and theta of the micro-grid and the main grid while closing the switch K3 0 Calculating the phase difference, and combining the phases obtained in the step (5)Bit signal theta and main power network phase signal theta acquired by SPLL phase-locked loop module 0 The adjustment is made according to the following relationship (see fig. 4, 6);
θ 2 ＝θ+kt(θ 0 -θ)
kt is a linear function of the time series, k is a time coefficient;
(7) Will theta 2 Clipping at theta and theta 0 Get theta between 3 The output value is the output value of the linear gradual approximation correction algorithm; the key of the linear gradual approximation phase correction algorithm is that a time series linear function kt is utilized to convert the phase difference between the microgrid and the main power grid into a function which gradually increases along with time, and the aim of adjusting the speed of the phase gradual approximation can be achieved by adjusting a time coefficient k; with such a theta 3 Generating a phase signal theta required by a PWM signal generator module by superposing theta 1 (see fig. 4, 6);
(8) Combined derived voltage amplitude signal U 1 Frequency signal f 1 Phase signal theta 1 And the PWM signal generator modules are controlled together to complete the adjustment of the voltage amplitude, the frequency and the phase of the microgrid (see figure 4).
The step (5) is carried out by a frequency signal f 1 The conversion into the phase signal θ is made by the following steps (see fig. 4):
(1) will frequency signal f 1 Multiplying by 2 pi to obtain angular frequency omega 1 ；
(2) Angular frequency omega 1 Through an integration link, the phase signal is converted into a phase signal theta.
Claims (4)
1. A micro-grid pre-synchronization grid-connected control system comprises a main grid and is characterized by comprising a frequency adjusting module, an SPLL phase-locked loop module, a voltage adjusting module, a phase generating module, a phase adjusting module and a PWM signal generator module; the SPLL phase-locked loop module is connected with a main power grid and used for collecting voltage signals, phase signals and frequency signals of the main power grid; the input end of the frequency adjusting module is connected with a main power grid, active power at a microgrid grid-connected point and a reference value signal of the active power of a control system are collected, an output signal of the output end of the frequency adjusting module and a frequency signal output by the output end of the SPLL phase-locked loop module are superposed according to an accumulator I and then are sent to the input end of the phase generating module and the input end of the PWM signal generator module; the input end of the voltage regulating module is connected with a main power grid, reactive power at a microgrid grid-connected point and a reference value signal of the reactive power of a control system are collected, and an output signal of the output end of the voltage regulating module and a voltage signal output by the output end of the SPLL phase-locked loop module are superposed by an accumulator II and then are sent to the input end of the PWM signal generator module; the output end of the phase generation module is connected with the phase adjustment module; the input end of the phase adjusting module is respectively connected with the output end of the phase generating module and the output end of the SPLL phase-locked loop module, and the output end of the phase adjusting module is connected with the input end of the PWM signal generator module; the output end of the PWM signal generator module outputs a PWM signal to control the on-off of a power electronic switch at the grid-connected position;
the frequency adjusting module consists of a proportional amplifier I, an integral adjuster I, a control switch K1, an accumulator III and an accumulator IV; the accumulator III superposes input signals of the frequency adjusting module, namely reference value signals of active power and active power of the control system; the input end of the proportional amplifier receives the superposed signal, and the output end of the proportional amplifier outputs an amplified signal to one input end of an accumulator IV; the input end of the integral regulator receives a superposed signal of the active power and a reference value signal of the active power of the control system through a control switch K1, and the output end of the integral regulator is connected with the second input end of the accumulator IV; the output end of the accumulator IV is connected with the input ends of the phase generation module and the PWM signal generator module; when the mode switching of 'grid connection-island' occurs, the control switch K1 is closed;
the voltage regulating module consists of a proportional amplifier II, an integral regulator II, a control switch K2, an accumulator V and an accumulator VI; the accumulator V superposes input signals of the frequency adjusting module, namely reference value signals of reactive power and reactive power of the control system; the input end of the proportional amplifier II receives the superposed signal, and the output end of the proportional amplifier II outputs an amplified signal to one input end of the accumulator VI; the input end of the integral regulator II receives a superposed signal of the reactive power and a reference value signal of the reactive power of the control system through a control switch K2, and the output end of the integral regulator II is connected with the second input end of the accumulator VI; the output end of the accumulator VI is connected with the input ends of the phase generation module and the PWM signal generator module; when the mode switching of 'grid connection-island' occurs, the control switch K2 is closed;
the phase adjusting module consists of a linear gradual approximation phase unit, a phase amplitude limiting unit, a control switch K3, an accumulator VII and an accumulator VIII; two input ends of the accumulator VII are respectively connected with the input end of the linear gradual approximation phase unit through a phase output signal of the control switch acquisition phase generation module and a main power grid phase signal acquired by the SPLL phase-locked loop module; two input ends of the accumulator VIII respectively receive a phase output signal of the phase generation module and an output signal of the linear gradual approximation phase unit, and the output end of the accumulator VIII is connected with the input end of the phase amplitude limiting unit; the output end of the phase amplitude limiting unit is connected with the input end of the PWM signal generator module; when grid connection is needed, the control switch K3 is closed.
2. The microgrid presynchronization grid-connected control system according to claim 1, wherein the linear successive approximation phase unit is a step signal generator.
3. The presynchronization control method applied to the microgrid presynchronization grid-connected control system of claim 1 is characterized by comprising the following steps of:
(1) In a grid-connected operation stage, the microgrid works in a droop control mode; at this stage, the SPLL phase-locked loop module is used for acquiring the frequency and the phase of a main power grid and the voltage amplitude signal of the main power grid at any time, the micro-grid pre-synchronization grid-connected control system judges the current working state, and if the working state meets the requirement of grid-connected stable working, the current voltage, frequency and phase are stored;
(2) When the mode switching of grid connection-island occurs, the micro-grid no longer acquires the voltage, frequency and phase of the main power grid, but uses the previously stored values as reference values of the micro-grid in the island operation mode; meanwhile, a droop control strategy is changed, and an integration link is added on the basis of P-f and Q-V control respectively to reduce the frequency and the deviation between the voltage and a reference value in the microgrid and realize that the power supply quality of the microgrid fluctuates in a small range;
(3) K1, K2 are control switches, when the mode switching of 'being incorporated into the power networks-isolated island' takes place, control signal control K1 and K2 that switch over by the mode are closed, insert the control system with the integral link for original proportional control mode changes into proportional-integral control mode, promptly:
wherein f and U are respectively the frequency and voltage in droop control, P and Q are the active and reactive outputs of the system, and f 0 、U 0 、P 0 、Q 0 For each corresponding control reference value, m and n are droop coefficients, m = K pf ，n＝K pu The integral control is utilized to eliminate the static difference of the system, the frequency and the amplitude of the microgrid are kept as same as those in a grid-connected state as possible or within a small fluctuation range, and the stability of the power supply quality of the microgrid system is improved;
(4) Obtaining a frequency signal and a voltage amplitude signal after the modulation by the frequency modulation module and the voltage modulation module through the steps (1) - (3), superposing the two signals with a main power grid frequency signal and a voltage amplitude signal acquired by the SPLL phase-locked loop module respectively, and generating a frequency signal f required by the phase generation module respectively 1 And a voltage amplitude signal U required by the PWM signal generator module 1 ；
(5) The phase generation module is used for generating the frequency signal f obtained in the step (4) 1 Converting the phase signal into a phase signal theta and sending the phase signal theta to the phase adjusting module as an input signal;
(6) The phase adjusting module closes the switch K3 by the grid-connected control signal before grid connection, and collects and stores the microgrid and the main power grid while closing the switch K3Phases theta and theta of 0 Calculating the phase difference, and comparing the phase signal theta obtained in the step (5) with the main power grid phase signal theta acquired by the SPLL phase-locked loop module 0 The adjustment is made according to the following relation;
θ 2 ＝θ+kt(θ 0 -θ)
kt is a linear function of the time series, k is a time coefficient;
(7) Will theta 2 Clipping at theta and theta 0 Get theta between 3 Namely, the output value is the output value of the linear successive approximation correction algorithm; the key of the linear gradual approximation phase correction algorithm is that a time series linear function kt is utilized to convert the phase difference between the microgrid and the main power grid into a function which gradually increases along with time, and the aim of adjusting the speed of the phase gradual approximation can be achieved by adjusting a time coefficient k; with such a theta 3 Generating a phase signal theta required by a PWM signal generator module by superposing the theta 1 ；
(8) Combined derived voltage amplitude signal U 1 Frequency signal f 1 Phase signal theta 1 And the PWM signal generator modules are controlled together to complete the adjustment of the voltage amplitude, the frequency and the phase of the microgrid.
4. The presynchronization control method for the microgrid presynchronization grid-connected control system according to claim 3, characterized in that in the step (5), the frequency signal f is used for generating the frequency signal 1 The conversion into the phase signal θ is composed of the following steps:
(1) will frequency signal f 1 Multiplying by 2 pi to obtain angular frequency omega 1 ；
(2) Angular frequency omega 1 Through an integration link, the phase signal is converted into a phase signal theta.
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