TWI599134B - Synchronization method for two separate areas in independent microgrid - Google Patents

Description

Synchronization method of two separate regions in independent microgrid

The present invention relates to a method for synchronizing two separate regions in an independent microgrid, and more particularly to a new method for synchronizing between two separate regions having different frequencies and voltages in an independent microgrid, in particular, to synchronize The controller uses Clarke conversion and Mandini fuzzy rules and combines with the inverter to reduce the phase difference between the two separate areas, which can achieve the practical effect of fast and seamless synchronization.

Renewable energy, gas turbine generators and energy storage systems are important sources of local load power in the microgrid. Microgrids can be connected to large power systems or independent of outlying islands or remote areas. When an area fails, the fault area must be disconnected from the non-faulty area by a static switch (SS) between the two areas. After troubleshooting, this recovery area must be reconnected to the non-faulty area by the inverter of the distributed power or energy storage system. Different areas within the smart microgrid have their own main distributed power or energy storage systems with voltage/frequency control. Therefore, the separation areas caused by faults in the microgrid have different frequencies and voltages that are quite close to the nominal value. Therefore, paralleling the two separate areas in the microgrid is a major challenge. Many studies have proposed synchronization techniques in normal or adverse environments (References 1 to 4). Document 1 proposes a synchronization technique based on the pq rule under the condition of distortion or unbalanced voltage by Rolim et al. (Rolim, LGB, Costa, DRd, Jr., and Aredes, M.: 'Analysis and software implementation of a robust synchronizing PLL Circuit based on the pq theory, ' IEEE Trans. on Industrial Electronics , 2006, 53, (6), pp. 1919-1926); but its pq rule and control theory are too complicated. Document 2 implements the feedforward action for Liccardo et al. to ensure the dynamic performance of the controller associated with the feedback operation to eliminate the estimation error of the phase angle (Liccardo, F., Marino, P., and Raim, G.: '"Robust and fast Three-phase PLL tracking system, ' IEEE Trans. on Industrial Electronics , 2011, 58, (1), pp. 221-231); but its feedforward and feedback control theory is too complex. Document 3 uses Fractal impulse response for Fran et al. The notch filter resists the abnormal harmonics of the controller circuit (Gonz□lez-Esp□n, F., Figueres, E., and Garcer□, G.: 'An adaptive synchronous-reference-frame phase-locked loop for power quality improvement In a polluted utility grid, ' IEEE Trans. on Industrial Electronics , 2012, 59, (6), pp. 2718-2731). Document 4 is for Balaguer et al. to utilize uncontaminated three-phase voltages in large power systems and microgrids. Estimated phase angle difference (Balaguer, IJ, Lei, Q., Yang, ST, Supatti, U. and Peng, FZ: 'Control for grid-connected and intentional islanding operations of distributed power generation,' IEEE Trans. on Industrial Electronics , 201 1, 58, (1), pp. 147-157). In view of the above-mentioned synchronization techniques, complex control rules or conversion control gains are required, and there are no separate microgrids in the current published technology. The separation of frequency and voltage must be synchronized to re-parallel reporting. However, this is a real problem in the independent microgrid. It is necessary to develop a new method. Therefore, the general practitioners cannot use the current technology. In actual use, it is required for synchronous control between two different areas in an independent microgrid.

The main object of the present invention is to overcome the above problems encountered in the prior art and to provide an independent microgrid that fully considers the actual phase angle difference caused by the frequency and phase angle difference, and realizes two different frequencies and voltages. A new way to synchronize between separate areas. A secondary object of the present invention is to provide a simulation result of using an actual independent microgrid by the present invention by applying a Clarke conversion and a Mandene fuzzy rule to a synchronous controller to reduce the phase difference between the two separated regions. It proves that this method does not require complicated control rules or conversion control gains, and can achieve the practical effects of fast and seamless synchronization. For the purpose of the above, the present invention is a method for synchronizing two separate regions in an independent microgrid, which is a separate region of the first region and the second region having different frequencies and voltages in an independent microgrid composed of multiple regions. Inputting a three-phase voltage of the first region and the second region to a synchronization controller, the synchronization controller being located in the first region or the second region, performing operation, Clark transform, and blurring by the synchronization controller After the comparison and comparison, a full phase angle difference is obtained, and the full phase angle difference is fed back to the inverter in the region to utilize the full phase angle difference as a reference angle of the first region and the second region in parallel. And the synchronous controller controls the inverter to synchronize, so that the inverter can output seamlessly synchronized voltage, frequency, phase and current; wherein the independent micro-grid is connected to the synchronous controller, and the synchronous controller The system comprises a filter, a full phase angle calculator connected to the filter, a fuzzy controller connected to the full phase angle calculator, and a phase locked loop connected with the fuzzy controller (P Hase-locked Loop, PLL), and a voltage/current controller connected to the fuzzy controller. In the above embodiment of the present invention, the full-phase angle calculator performs the required operations in accordance with the Clarke conversion for each of the three-phase voltages of the first region and the second region, and cooperates with the fuzzy controller to use the Mandini fuzzy rule ( Mamdani fuzzy rules) fine-tune the results of the operation. In the above embodiment of the present invention, the three-phase voltage of the first region is , , And the three-phase voltage of the second region is , , If you convert to Clark , can be obtained by the full phase angle calculator after the Clark conversion operation. In the above embodiment of the present invention, the fuzzy controller will obtain Unfuzzification And cooperate with the phase-locked loop to obtain the phase angle of the region where the synchronous controller is located. Get a new phase angle - After that, abc/dq is used as a park conversion. In the above embodiment of the present invention, the Less than A real number. In the above embodiment of the present invention, the fuzzy controller uses the Center of Gravity to defuzzify. In the above embodiment of the invention, the voltage/current controller is used to control the inverter so that the inverter can output seamlessly synchronized voltage, frequency, phase and current.

Standalone microgrids have distributed generation sources (DMS) or energy storage systems (ESS) that exist in coastal islands or remote areas. When the independent microgrid generates a fault condition, the microgrid splits into several areas, each of which pre-designates a distributed power source or energy storage system to provide the area's electrical load. The three-phase voltage and frequency of these areas may vary after the fault is removed. In order to restore the original microgrid architecture, these regions must be interconnected again by synchronous synchronization. In this regard, the present invention proposes a synchronous control technique suitable for use in inverters of two different three-phase voltages and frequencies. Please refer to FIG. 1 to FIG. 8 respectively, which are schematic diagrams of the block flow of the present invention, and the present invention is connected in a t=0.4 second state in comparison with the situation, and the present invention is only considered in the context. And in t=0.4 seconds, the schematic diagram is connected, and the present invention considers the situation one. And at t=0.55 seconds, the seamless connection diagram is reached, and the present invention is considered in the context 2 And at t=0.70 seconds, the seamless connection diagram is reached, and the invention is obtained by the situation 2 Schematic diagram of the change, the present invention considers the situation three And at t=0.70 seconds, the seamless connection diagram is reached, and the present invention is obtained in the context three. A schematic diagram of the changes. As shown in the figure: the present invention is a method for synchronizing two separate regions in an independent microgrid, which is a separation of two different frequencies and voltages between the first region 11 and the second region 12 in the independent microgrid 1 composed of multiple regions. a region, inputting the three-phase voltages of the first region 11 and the second region 12 to a synchronization controller 2, the synchronization controller 2 being positionable in either the first region 11 or the second region 12 by the synchronization controller 2 After performing the operation, Clark transform, blurring and comparison, a full phase angle difference is obtained, and the full phase angle difference is fed back to the inverter 13 in the region to utilize the full phase angle difference. As the reference angle of the first region 11 and the second region 12 are synchronously connected in parallel, the synchronous controller 2 controls the inverter 13 to synchronize, so that the inverter 13 can output the seamlessly synchronized voltage, frequency, phase and current. From the first figure, the independent microgrid 1 is connected to the synchronous controller 2, and the synchronous controller 2 includes a filter 21, a full phase angle calculator 22 connected to the filter 21, and a fuzzy controller 23 connected to the full phase angle calculator 22, a phase-locked loop (PLL) 24 connected to the fuzzy controller 23, and a voltage/current controller 25 connected to the fuzzy controller 23, The all-phase angle calculator 22 cooperates with the three-phase voltages of the first region 11 and the second region 12 to perform the required operations in Clark conversion, and cooperates with the fuzzy controller 23 to use the Mandani fuzzy rules. ) Fine-tune the result of the operation. When operating, it is assumed that there are two regions - the first region 11 and the second region 12 - in the independent microgrid 1. The two regions 11, 12 have a phase difference And there are different frequencies w ₁ and w ₂ . When the two areas 11, 12 are synchronized, Must be reduced to zero, not just Must be reduced to zero. Let the three-phase voltage of the first region 11 be as follows: ; ; . The three-phase voltage of the second region 12 is as follows: ; ; . Consider the first area 11 and Clark conversion: Therefore, you can get: . Similarly, in the second area 12, it is obtained: . Reuse the literature 1 versus To consider different frequencies (w ₁ and w ₂ ) to get the following: ; . The present invention does not use the complex control gain of Document 1, but can be Divide the right side of the formula And then use the inverse sine to get Items to synchronize. The formula contains the cosine and provides the decision With the aid of quadrants, therefore, the advantages of the proposed synchronization method are: (1) and and Regardless of size; (2) consider different frequencies w ₁ and w ₂ ; and (3) consider full phase angle difference Instead of just considering . If forced directly A value of zero will result in a transient. So the present invention proposes 25 Mandini fuzzy rules to make Smoother and lesser to achieve seamless synchronization. Order symbol for . The Mandene fuzzy rule adopted by the fuzzy controller 23 is as follows: Is A and For B, then For C, where versus They are normally in the range of [-0.33, 1] and [-0.1, 0.4]. Unfuzzified Expressed as less than a real number to slow down Rapid change. The membership functions A, B, and C are represented by a ladder function. The invention uses 5, 5 and 4 membership functions respectively , versus . The present invention uses the Center of Gravity to deblur. Figure 1 illustrates the synchronous controller of the present invention. Before using the method, it is necessary to determine that the voltages of the first region 11 and the second region 12 are noise-free. Assuming that the proposed synchronous controller 2 is in the second region 12, the phase angle is obtained by the phase-locked loop circuit 24 . When obtaining a new phase angle - After that, abc/dq is used for park conversion, and the voltage/current controller 25 is executed by the d-axis and q-axis voltages to control the inverter 13, so that the inverter 13 can output seamlessly synchronized voltage, frequency, and phase. The current is synchronized to reduce the phase difference between the two regions 11, 12. The following is a simulation comparison result of the present invention: The synchronization method of the present invention uses the microgrid system of FIG. 1 for research and analysis. In the independent microgrid 1, the first region 11 has a solar photovoltaic array 111 (fixed power/virtual power mode, 60 kW) and micro-turbine generator 112 (voltage/frequency mode, 65 kW), where micro-turbine generator 112 is a voltage and frequency reference. The second zone 12 has a solar photovoltaic array 121 (fixed power/virtual power mode, 60 kW) and an energy storage system 122 (voltage/frequency mode, 65 kWh), wherein the energy storage system 122 has the synchronous controller of the present invention. The first region 11 is connected to the second region 12 via a static switch 14 (Static Switch, SS). The microgrid 1 has a rated load voltage of 380V. Situation 1: The voltage and frequency of the two regions are the same, the phase angle It is 120°. As shown in Fig. 2, the static switch is closed at t = 0.4 seconds, and at this time, there is no synchronization, so a huge transient occurs. As shown in Figure 3, in the same situation, if only apply (not That is, there is no Mandene fuzzy rule) and a small transient occurs. Figure 4 shows the use of Mandene's fuzzy rule, near t = 0.55 seconds, by Make the two areas seamlessly linked. Scenario 2: In order to prove the feasibility of the present invention, it is assumed that the frequencies of the first region and the second region are 60 Hz and 62 Hz, respectively, and between the two regions. The initial value is 120°, and the synchronous controller of the present invention starts synchronization at t = 0.4 seconds. Figure 5 shows that the two regions can achieve seamless synchronization at t = 0.70 seconds. Figure 6 shows Change. Scenario 3: The voltages of the first region and the second region are 1 p.u. and 0.9 pu, respectively, and their phase angles Also at 120°, the synchronous controller of the present invention starts synchronizing at t = 0.4 seconds. Figure 7 and Figure 8 show the seamless connection and phase angle of the two voltages at t = 0.7 seconds. Approaching zero. The present invention is directed to a new method of synchronizing between two different regions in an independent microgrid. The actual phase angle difference caused by the difference in frequency and phase angle is fully taken into account in the present invention by reducing the phase difference between the two separation regions by applying the Clarke conversion and Mandini fuzzy rules to the inverter. The actual independent microgrid simulation results of the present invention are sufficient to verify that the method does not require complicated control rules or conversion control gains, and can achieve the practical effect of fast and seamless synchronization. In summary, the present invention is a synchronization method for two separate areas in an independent microgrid, which can effectively improve various shortcomings of the conventional microgrid, and realizes synchronization between two separate regions with different frequencies and voltages in an independent microgrid. The new method, by using the synchronous controller to apply the Clark conversion and Mandini fuzzy rules to the inverter to reduce the phase difference between the two separated regions, the present invention uses the actual independent microgrid simulation results to prove that the method does not need to be complicated. The control law or the conversion control gain can achieve the practical effect of rapid and seamless synchronization, so that the invention can be more advanced, more practical and more suitable for the user, and indeed meets the requirements of the invention patent application.提出 Submit a patent application in accordance with the law. However, the above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto; therefore, the simple equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the invention are modified. All should remain within the scope of the invention patent.

1‧‧‧Independent microgrid

11‧‧‧First area

111‧‧‧Solar Photovoltaic Array

112‧‧‧Micro Turbine Generator

12‧‧‧Second area

121‧‧‧Solar Photovoltaic Array

122‧‧‧ Energy storage system

13‧‧‧Inverter

14‧‧‧Static switch

2‧‧‧Synchronous controller

21‧‧‧ filter

22‧‧‧All Phase Angle Calculator

23‧‧‧Fuzzy controller

24‧‧‧ phase-locked loop

25‧‧‧Voltage/current controller

Figure 1 is a schematic diagram of the block flow of the present invention. Fig. 2 is a schematic diagram showing the connection of the present invention at t = 0.4 seconds in the context of a comparison. Figure 3 is a comparison of the present invention with contextual comparison The link diagram is connected at t=0.4 seconds. Figure 4 is a scenario considering the present invention. The seamless connection diagram is reached at t=0.55 seconds. Figure 5, the present invention is considered in context 2 The seamless connection diagram is reached at t=0.70 seconds. Figure 6, the present invention is derived from the situation 2 A schematic diagram of the changes. Figure 7, the present invention is considered in context three The seamless connection diagram is reached at t=0.70 seconds. Figure 8, the present invention is obtained in the context of the third A schematic diagram of the changes.

1‧‧‧Independent microgrid

11‧‧‧First area

111‧‧‧Solar Photovoltaic Array

112‧‧‧Micro Turbine Generator

12‧‧‧Second area

121‧‧‧Solar Photovoltaic Array

122‧‧‧ Energy storage system

13‧‧‧Inverter

14‧‧‧Static switch

2‧‧‧Synchronous controller

21‧‧‧ filter

22‧‧‧All Phase Angle Calculator

23‧‧‧Fuzzy controller

24‧‧‧ phase-locked loop

25‧‧‧Voltage/current controller

Claims (3)

A method for synchronizing two separate regions in an independent microgrid is a separate region of the first region and the second region having different frequencies and voltages in an independent microgrid composed of multiple regions, and inputting the first region and the second region a three-phase voltage of the region to a synchronous controller, the synchronous controller being located in the first region or the second region, after the operation, Clark transform, blurring and comparison by the synchronous controller Obtaining a full phase angle difference, and feeding back the full phase angle difference to the inverter of the region, to utilize the full phase angle difference as a reference angle of the first region and the second region in parallel, thereby allowing The synchronous controller controls the inverter to synchronize, so that the inverter can output seamlessly synchronized voltage, frequency, phase and current; wherein the independent micro-grid is connected to the synchronous controller, and the synchronous control The device includes a filter, a full phase angle calculator connected to the filter, a fuzzy controller connected to the full phase angle calculator, and a phase locked loop connected to the fuzzy controller (Phas An e-locked loop (PLL), and a voltage/current controller connected to the fuzzy controller, wherein the full phase angle calculator cooperates with each of the three-phase voltages of the first region and the second region by Clark conversion The required operation is combined with the fuzzy controller to fine-tune the operation result by the Mamdani fuzzy rules. When operating, the three-phase voltage of the first region is V _{a 1} =V ₁ sin ω ₁ t , , And the three-phase voltage of the second region is V _{a 2} =V ₂ sin( ω ₂ t + θ ), , If you convert to Clark Then, the full phase angle calculator can obtain Δ θ =( ω ₂ - ω ₁ ) t + θ by Clark transform operation; the fuzzy controller blurs the obtained Δ θ into Δ θ _new , and cooperates with The phase angle ω ₂ t + θ _{old of the} region where the synchronous controller is located is obtained by the phase-locked loop, and a new phase angle ω ₂ t + θ _old - Δ θ _{new is obtained} , and then abc/dq is used for park conversion, wherein The Δ θ _new is less than a real number of Δ θ . A method for synchronizing two separate regions in an independent microgrid according to claim 1 of the patent application, wherein the fuzzy controller utilizes a Center of Gravity to defuzzify. A method for synchronizing two separate regions in an independent microgrid according to claim 1 of the patent application, wherein the voltage/current controller is used to control the inverter so that the inverter can output a seamless synchronous voltage , frequency, phase and current.