WO2018153222A1 - 一种基于内模控制的微电网并离网平滑切换控制方法 - Google Patents
一种基于内模控制的微电网并离网平滑切换控制方法 Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- the invention belongs to the field of micro-grid operation control, and in particular relates to a micro-grid based on internal model control and an off-grid smooth switching control method.
- micro-sources in micro-grids include photovoltaics, wind power, batteries, micro-turbines, etc., usually operated in parallel by power electronics (such as converters).
- power electronics such as converters
- the output power is greatly affected by the weather. Generally, it is output according to the maximum power or constant power, which is called slave power.
- slave power For micro-sources with storage characteristics such as batteries and fuel cells, the control is relatively flexible. It can be used either as a constant power control or as a voltage source in island mode, called the main power supply.
- the microgrid can be operated in parallel with the large power grid, or can be operated in an island under the grid fault, independently supplying power to the local load, and has high power supply safety and reliability.
- the main control methods of the microgrid can be summarized as master-slave control and droop control. Since the master-slave control can easily apply the existing commercial inverters, the current micro-grid demonstration project and corresponding research are still dominated by the master-slave structure. It relies on a power supply with stable power and large capacity to bear the power supply of the network (such as energy storage converter). It adopts PQ control when it is connected to the grid. It works in v/f mode when it is isolated, and it can flexibly adjust the active/none.
- the throughput of the power power provides voltage and frequency support for other DGs. Therefore, when the microgrid is switched between the grid-connected/islanding mode, the control structure of the main inverter also needs to be adjusted accordingly. How to reduce the disturbance of the structural switching of different controllers to the dynamic performance of the system has always been the master-slave structure. The difficulty of the next mode conversion. In addition, compared with the traditional power grid, the microgrid has small inertia. A series of disturbances such as output power fluctuation of intermittent power supply such as wind and light, load power consumption and model parameter perturbation will cause significant instantaneous fluctuations. How to ensure fast and accurate DG?
- the microgrid must have an effective control system to actively suppress the influence of supply and demand power disturbance and control structure disturbance on the dynamic performance of the system during the operation of the microgrid, so that the impact control is within a reasonable range, even eliminate the disturbance and improve the stability of the microgrid.
- sexual and dynamic performance to improve power quality
- the technical problem to be solved by the present invention is to provide a micro-grid and off-grid smooth switching control method based on internal model control, which can avoid different inverter control loops when switching between microgrid and off-grid operation modes
- the disturbance caused by the road switching, and the internal model control based on the disturbance observer can actively suppress the supply and demand power disturbance, and has the ideal tracking performance and anti-interference performance.
- a micro-grid and off-grid smooth switching control method based on internal model control comprising the following steps:
- Step 10 Using the microgrid energy manager to collect the main grid operation information, selecting the microgrid operation mode according to the operation information of the main grid, and issuing an operation instruction to the microgrid main inverter; if the main grid is in normal operation, the microgrid works on Grid-connected mode; if the main power grid fails, the micro-grid works in off-grid mode;
- Step 20 The main inverter power loop adopts a droop control mode to generate a reference voltage and a reference frequency of the main inverter, as shown in equations (1) and (2):
- v n represents the rated value of the main inverter output voltage, in kilovolts
- n represents the voltage droop characteristic coefficient of the distributed power supply, unit: kV / Mega lack
- Q indicates the actual output reactive power of the distributed power supply, the unit: mega
- the Q n indicates the distributed power output reactive power at the rated voltage, the unit: mega
- the inv represents the local inverter local angular frequency Reference instruction
- w n represents the main inverter angular frequency rating, unit: radians / sec
- m represents the frequency droop characteristic coefficient of the distributed power supply, unit: radians / sec ⁇ megawatts
- P represents the actual output active power of the distributed power supply , unit: megawatt
- P n represents the distributed power output active power at rated angular frequency, in megawatts
- Step 30 collecting microgrid operation data, applying the internal model control based on the disturbance observer to the voltage and current double loop controller, improving the robustness and tracking performance of the control system;
- Step 40 Perform voltage and phase control according to the operating mode of the microgrid: when the microgrid is switched from the grid-connected mode to the off-grid mode, the operating value of the previous moment is maintained to avoid transient disturbance; the microgrid is switched from the off-grid mode to In the net mode, a pre-synchronization operation is performed to reduce the deviation to the allowable range.
- the step 30) includes: the voltage outer loop adopts a proportional integral controller, as shown in the formula (3):
- d-axis component in kilo amps; k up represents the proportional term coefficient in the voltage proportional integral controller, k ui represents the integral term coefficient in the voltage proportional integral controller, and 1 s represents the integral action; Indicated in the dq reference coordinate system, The d-axis component, v od represents the d-axis component of the main inverter output voltage v o in the dq reference coordinate system, and C f represents the capacitor value in the LC filter to which the inverter terminal is connected, in units of: Farad; oq expressed in the dq reference frame, the main q-axis component of the inverter output voltage v o, unit: kV; Indicates the current loop reference setpoint in the dq reference coordinate system Q-axis component, unit: thousand amps; Indicated in the dq reference coordinate system, The q-axis component, in kilo amps; k up represents the proportional term coefficient in the voltage proportional integral controller
- the current inner loop uses a proportional controller, as shown in equation (4):
- v id represents the d-axis component of the modulated wave voltage output by the main inverter current controller in the dq reference coordinate system
- v iq represents the modulation of the main inverter current controller output in the dq reference coordinate system q-axis component of the voltage wave
- k ip represents a proportional term proportional controller coefficient current
- i id represents the dq reference frame, d-axis component of the output current value of the main inverter
- i iq represents The dq reference coordinate system, the q-axis component of the output current value of the main inverter, the unit: kiloamperes
- L f represents the inductance value of the LC filter connected to the inverter terminal, unit: Henry;
- G(s) represents a generalized controlled object
- k pwm represents the main inverter voltage gain
- R f represents the filter resistance in the filter
- s represents the differential
- f(s) represents the low-pass filter of the internal model control feedforward term
- G n (s) represents the nominal model of the generalized controlled object
- ⁇ represents the filter time constant of f(s), in seconds
- Q(s) represents the low-pass filter of the feedforward term of the disturbance observer
- T f represents the filter time constant of Q(s), in seconds
- the internal model control feedforward term corresponds to the tracking performance of the control system.
- the input and output transfer function is unitized by feedforward compensation to improve the setpoint tracking performance.
- the disturbance observer feedforward term corresponds to the control system's anti-interference performance, and the microgrid operation is estimated in real time. Under the condition of equivalent power disturbance, and through the feedforward compensation to the current loop set value, improve the system robustness, the internal model control based on the disturbance observer is applied to the voltage and current loop to improve the dynamic performance of the control system.
- the main inverter local output voltage reference instruction The difference from the main inverter output voltage v o is eliminated by the voltage outer loop.
- the disturbance observer feedforward term estimates the equivalent power disturbance in the microgrid operating condition in real time, and the disturbance includes distributed power output disturbance, load consumption power disturbance, and model parameter. move.
- the step 40) specifically includes: firstly locking the grid voltage, collecting the grid side phase angle ⁇ g and comparing the main inverter phase angle ⁇ inv , and obtaining the frequency compensation amount ⁇ w c by integrating
- the frequency compensation amount ⁇ w c is compensated in the local inverter local angular frequency reference command w inv ; in order to ensure that the microgrid side frequency and phase angle simultaneously follow the grid side rating, it is necessary to maintain the phase angle coincidence state for a certain time, when the satisfaction is satisfied
- the frequency pre-synchronization is completed; for the amplitude pre-synchronization, the acquisition main inverter output voltage v o is compared with the grid-side rated voltage v g , and the voltage compensation amount ⁇ v c is obtained by integration, and the voltage compensation amount is compensated Main inverter local output voltage reference command
- the pre-synchronization is compensated in the local inverter local output voltage reference command
- the present invention has the following beneficial effects: in the grid-connected mode and the off-grid mode, the main inverter power loop uses the droop control to generate the voltage loop reference value and the frequency reference value, thereby avoiding the conventional
- the control loop switching caused by the mode conversion process in the algorithm lays a foundation for the smooth transition of the microgrid working mode.
- the internal model control based on the disturbance observer is applied to the voltage-current dual-loop control structure, which can effectively offset the supply and demand power in the system. Balancing the effects and improving the robustness of the model parameters perturbation, while optimizing the control loop tracking performance, further improving the dynamic quality of the mode switching process.
- the control method is simple to implement, but the linear control structure is added to the traditional scheme, and is suitable for the inverter algorithm implemented by the digital signal processor DSP, and has good practical promotion value.
- Figure 1 is a flow chart of an embodiment of the present invention
- FIG. 2(a) is a structural diagram of voltage droop control in an embodiment of the present invention.
- 2(b) is a structural diagram of frequency droop control in an embodiment of the present invention.
- FIG. 3 is a structural diagram of voltage and current double loop control based on internal mode control in an embodiment of the present invention
- phase pre-synchronization control in a microgrid transition process according to an embodiment of the present invention
- 4(b) is a block diagram of voltage pre-synchronization control during a microgrid transition process according to an embodiment of the present invention
- FIG. 5 is a schematic diagram of a micro-grid simulation system used in an embodiment of the present invention.
- 6(a) is a simulation result of the output voltage of the main inverter of the grid-connected island mode in the embodiment of the present invention
- 6(b) is a simulation result of the output current of the main inverter of the grid-connected island mode in the embodiment of the present invention.
- Figure 7(a) shows the simulation results of the output voltage of the main inverter with grid-connected island mode using traditional no-mode control
- Figure 7(b) is the simulation result of the output current of the main inverter with grid-connected island mode using traditional no-mode control
- Fig. 8(c) is a simulation result of the angular frequency of the island mode microgrid in the embodiment of the present invention.
- a method for controlling a micro-grid and off-grid smooth switching based on internal model control includes the following steps:
- Step 10 Using the microgrid energy manager to collect the main grid operation information, select the microgrid operation mode according to the operation information of the main grid, and issue an operation command to the microgrid main inverter. If the main power grid is operating normally, the microgrid works in the grid-connected mode; if the main grid fails, the microgrid works in the off-grid mode.
- Step 20 The main inverter power loop adopts a droop control mode to generate a reference voltage and a reference frequency of the main inverter, as shown in equations (1) and (2):
- v n represents the rated value of the main inverter output voltage, in kilovolts
- n represents the voltage droop characteristic coefficient of the distributed power supply, unit: kV / Mega lack
- Q indicates the actual output reactive power of the distributed power supply, the unit: mega
- the Q n indicates the distributed power output reactive power at the rated voltage, the unit: mega
- the inv represents the local inverter local angular frequency Reference instruction
- w n represents the main inverter angular frequency rating, unit: radians / sec
- m represents the frequency droop characteristic coefficient of the distributed power supply, unit: radians / sec ⁇ megawatts
- P represents the actual output active power of the distributed power supply , unit: megawatt
- P n represents the distributed power output active power at rated angular frequency, in megawatts.
- v n and w n are taken as grid side ratings.
- Main inverter local output voltage reference command when the microgrid is connected to the grid The angular frequency reference command w inv is clamped by the large power grid, and outputs active power P n and reactive power Q n .
- the main inverter acts as the main power source to support the voltage/frequency of the system and maintains power balance.
- Step 30 Collect microgrid operation data, apply the internal model control based on the disturbance observer to the voltage and current double loop controller, and improve the robustness and tracking performance of the control system.
- the step 30) includes: the voltage outer loop adopts a proportional integral controller, as shown in the formula (3):
- the current inner loop uses a proportional controller, as shown in equation (4):
- v id represents the d-axis component of the modulated wave voltage output by the main inverter current controller in the dq reference coordinate system
- v iq represents the modulation of the main inverter current controller output in the dq reference coordinate system
- k ip represents the proportional term coefficient in the current proportional controller
- i id represents the d-axis component of the main inverter output current value in the dq reference coordinate system
- i iq is expressed in The dq reference coordinate system, the q-axis component of the output current value of the main inverter, the unit: kiloamperes
- L f represents the inductance value of the LC filter connected to the inverter terminal, unit: Henry;
- G(s) represents a generalized controlled object
- k pwm represents the main inverter voltage gain
- R f represents the filter resistance in the filter
- s represents the differential
- f(s) represents the low-pass filter of the internal model control feedforward term
- G n (s) represents the nominal model of the generalized controlled object
- ⁇ represents the filter time constant of f(s), in seconds
- Q(s) represents the low-pass filter of the feedforward term of the disturbance observer
- T f represents the filter time constant of Q(s), in seconds
- the internal model control feedforward term corresponds to the tracking performance of the control system.
- the input and output transfer function is unitized by feedforward compensation to improve the setpoint tracking performance.
- the disturbance observer feedforward term corresponds to the control system's anti-interference performance, and the microgrid operation is estimated in real time. Under the condition of equivalent power disturbance, and through the feedforward compensation to the current loop set value, improve the system robustness, the internal model control based on the disturbance observer is applied to the voltage and current loop to improve the dynamic performance of the control system.
- the current inner loop adopts a proportional controller, and the main inverter local output voltage reference command Main inverter output voltage v o to eliminate the difference between the outer loop voltage.
- the disturbance observer feedforward term estimates the equivalent power disturbance in the microgrid operating condition in real time, the disturbance includes distributed power supply output disturbance, load consumption power disturbance, and model parameter perturbation.
- the design priorities of the internal model controller feedforward term and the disturbance observer feedforward term are the filter time constants ⁇ and T f , respectively .
- debugging ⁇ makes the controller tracking performance optimal; then add the disturbance observer feedforward term, and debug T f to improve the system immunity performance.
- Step 40) Perform voltage and phase control according to the operating mode of the microgrid: when the microgrid is switched from the grid-connected mode to the off-grid mode, the operating value of the previous moment is maintained to avoid transient disturbance; the microgrid is switched from the off-grid mode to In the net mode, a pre-synchronization operation is performed to reduce the deviation to the allowable range.
- the step 40) specifically includes: first locking the grid voltage. In the present embodiment, it is preferable to extract the positive sequence component using the second-order generalized integral, and the influence of the unbalanced load or the like can be avoided.
- the collecting grid side phase angle ⁇ g is compared with the main inverter phase angle ⁇ inv , and the frequency compensation amount ⁇ w c is obtained by integrating, and the frequency compensation amount ⁇ w c is compensated in the main inverter local angular frequency reference command w inv ;
- the frequency pre-synchronization is completed; for the amplitude pre-synchronization, the main inverter is collected.
- the output voltage v o is compared with the rated voltage v g of the grid side, and the voltage compensation amount ⁇ v c is obtained by integration, and the voltage compensation amount is compensated to the local inverter local output voltage reference command.
- the phase angle deviation and the voltage amplitude deviation of the microgrid side and the grid side are simultaneously reduced to the allowable range, the pre-synchronization process is completed, and the grid-connecting operation is performed.
- a micro-grid smooth switching control method based on internal model control is formed.
- the power loop adopts droop control to avoid control loop switching caused by switching of different operating modes;
- the internal model control based on the disturbance observer is applied to the voltage current loop to realize the microgrid operation process.
- Active suppression of mid-power disturbance effects and improved tracking performance of setpoints improve system stability and dynamic performance.
- the control method simultaneously suppresses control structure disturbance and power disturbance.
- the microgrid voltage droop control block diagram in the embodiment of the present invention is as shown in 2(a), and the frequency droop control block diagram is as shown in FIG. 2(b).
- the voltage droop control obtains a voltage reference value by the relationship between the reactive power output of the main inverter and the output voltage.
- the frequency droop control obtains the inverter reference frequency by the relationship between the active power and the frequency of the main inverter output, and then obtains the phase angle of the inverter.
- the block diagram of the voltage-current double-loop control based on the internal model control in the embodiment of the present invention is shown in FIG. 3.
- the control block diagram mainly includes three parts, one part is a basic voltage-current double-loop controller, and the other part is a disturbance observer feedforward item, and the last part. It is the internal model controller feedforward item.
- the current inner loop of the voltage and current double loop adopts a proportional controller, and the loop error is eliminated by the voltage controller.
- the disturbance observer estimates the equivalent power disturbance in real time by comparing the current loop set value with the inverter output voltage, and feeds forward compensation to the current setpoint.
- the internal model controller feedforward term unitizes the input and output transfer functions by set value feedforward compensation, improving tracking performance.
- the feedback channel and the feedforward channel complement each other, satisfying the two-degree-of-freedom design criterion, realizing the synchronous improvement of the tracking performance and the anti-interference performance during the operation of the microgrid, and improving the dynamic quality of the system.
- the phase angle pre-synchronization control block diagram in the embodiment of the present invention extracts the grid-side dq transformation reference phase based on the second-order generalized integral through the grid phase extraction link, and provides the microgrid grid-connected operation or pre-synchronization operation process.
- Phase angle reference when the pre-synchronization command triggers the pre-synchronization module, the inverter side angle frequency is adjusted by proportional integral to make the inverter side phase angle synchronously follow the grid side phase angle.
- the voltage amplitude pre-synchronization control block diagram in the embodiment of the present invention is as shown in 4(b), and the inverter output voltage is adjusted to follow the grid side voltage amplitude by proportional integral.
- the simulation system is shown in Figure 5. It consists of an energy manager, a static switch STS, a main inverter (storage unit), and a number of slave inverters (photovoltaic inverters/wind power inverters) and electrical loads.
- the energy manager collects the grid side signals and determines the microgrid operating mode. In different operating modes, the wind power inverter and the photovoltaic inverter are in the PQ control mode, so the focus of the microgrid operation is the main inverter control method. Under normal circumstances, the microgrid is connected to the grid and the STS is closed. The voltage and frequency of the micro grid side are determined on the grid side, and the main inverter outputs the rated active power and reactive power according to the set droop control.
- the simulation micro-grid model is built based on MATLAB/Simulink platform, and the micro-grid and off-grid mode switching and the loading or de-loading of the island microgrid are simulated respectively.
- the microgrid control method and the traditional microgrid are compared in the embodiment of the present invention. Differences in control methods.
- the traditional off-grid control method is to make the current controller control amount follow the previous controller control amount at the switching instant, and only includes the basic voltage and current double loop feedback channel, without the set value internal mode control feedforward term and load current. Disturbance observation feedforward channel.
- FIG. 6 is a simulation result of the grid-connected islanding of the microgrid using the control method of the invention. Compared to planned silos, unplanned islands are more difficult to achieve smooth switching, especially when there is a large power transfer at the tie line.
- the main inverter operates in the grid-connected mode. Since the rated active power P n and the reactive power Q n are zero in the droop control, the inverter has zero power output, and the load power is all supplied by the grid; at 0.2 s, the grid The fault causes the microgrid to enter the island mode, the load power is all supplied by the micro grid, and the power supply on the grid side is zero.
- Figure 6(a) shows the output voltage waveform of the main inverter during the switching of the microgrid from grid-connected to island operation mode.
- the abscissa indicates time, the unit is second, and the ordinate indicates the output voltage in volts.
- the initial output voltage is consistent with the grid side rating, and decreases after entering the island, but the transient process is short, the two cycle adjustments are stable, and the three-phase voltage does not oscillate.
- Figure 6(b) shows the output current waveform of the main inverter during the switching of the microgrid from grid-connected to island operation mode.
- the abscissa indicates time, the unit is second, and the ordinate indicates the output current.
- the unit is ampere. As shown in Fig.
- FIG. 7 is a microgrid simulation result using a conventional control strategy.
- the main inverter operates in the grid-connected mode. Since the rated active power P n and the reactive power Q n are zero in the droop control, the inverter has zero power output, and the load power is all supplied by the grid; at 0.2 s, the grid The fault causes the microgrid to enter the island mode, the load power is all supplied by the micro grid, and the power supply on the grid side is zero.
- Figure 7(a) shows the output voltage waveform of the main inverter during the switching of the microgrid from grid-connected to island operation mode.
- the abscissa represents time, the unit is second, and the ordinate represents the output voltage in volts.
- the initial output voltage is consistent with the grid side rating, and it is reduced after entering the island. It takes eight or nine cycles to stabilize.
- Figure 7(b) shows the output current waveform of the main inverter during the switching of the microgrid from grid-connected to island operation mode.
- the abscissa indicates the time, the unit is second, and the ordinate indicates the output current.
- the unit is ampere.
- the initial microgrid side main inverter current output is zero.
- the output current increases, and a certain distortion and transition occur at the beginning.
- the process oscillates. This is because although the state following can be a smooth running process, the controller loops in the control loop during the mode conversion, causing the control process to oscillate.
- the smooth transition of the running process can be realized as shown in FIGS. 6(a) and 6(b).
- Figure 8 shows the simulation results of the load-shedding operation using the method of the present invention in the micro-grid island mode.
- the system first runs in the island no-load mode, puts the load at 0.2s, and removes the load at 0.4s.
- Figure 8(a) shows the output voltage waveform of the main inverter of the microgrid.
- the abscissa represents time, in seconds, and the ordinate represents the output voltage in volts.
- Figure 8(b) shows the output current waveform of the main inverter of the microgrid.
- the abscissa indicates the time, the unit is second, and the ordinate indicates the output current.
- the unit is ampere.
- Figure 8(c) shows the angular frequency waveform of the main inverter of the microgrid.
- the abscissa represents time, the unit is second, and the ordinate represents the output current in radians/second.
- the output voltage is slightly reduced, the output current is increased to provide power to the load, and only very small jitter occurs, and the steady state value is quickly entered; at this time, the system frequency is lowered according to the set droop coefficient. 0.5Hz (that is, the angular frequency is reduced by ⁇ rad, about 311rad), which is consistent with the drooping characteristics.
- the load shedding operation is subsequently performed, the output voltage returns to the rated value within one or two cycles, and the current returns to zero output, while the angular frequency rises back to 100 ⁇ .
- This control method has good dynamic regulation performance for the microgrid in island mode.
- the control method of the embodiment of the present invention is a micro-grid based on internal model control and an off-grid smooth switching control method.
- This control method uses droop control in the power loop to avoid switching between different controllers.
- the improved voltage-current double-loop structure including the internal model control feedforward term and the disturbance observation feedforward term improves the anti-interference performance and tracking performance of the control system, realizes seamless switching from the network, smoothes the dynamic process, and effectively improves the micro Dynamic performance and power quality of the grid.
Abstract
一种基于内模控制的微电网并离网平滑切换控制策略，包括下述步骤：步骤10）微电网能量管理器采集主电网运行信息，根据电网的运行状态进行微电网操作模式决策，并下发操作指令到微电网主逆变器；步骤20）并网运行时，主逆变器采用下垂控制方式输出额定功率，逆变器参考电压和参考频率由主电网决定；离网运行时，逆变器根据下垂控制承担系统的电压/频率支撑；步骤30）根据逆变器输出电压参考指令及相角参考指令，建立基于内模控制的电压电流双环控制器用以提高逆变器动态性能；步骤40）基于微电网操作模式，进行电压和相位的预同步控制，避免模式切换的瞬时影响。
Description
本发明属于微电网运行控制领域，具体来说，涉及一种基于内模控制的微电网并离网平滑切换控制方法。
随着传统能源供应短缺以及对用电可靠性的提高，以高效、清洁的分布式电源(distributedgeneration，DG)为基础，结合储能单元、负荷和相关控制装置的微电网成为一种灵活、先进的新型供电方式，是近年来国内外研究的热点。微网中的微源包括光伏、风电、蓄电池、微型燃气轮机等，通常通过电力电子装置(如变流器)并联运行。对于光伏、风机等微源，其输出功率大小受天气影响较大，一般按最大功率或恒功率输出，称之为从电源；对于蓄电池、燃料电池等具有储能特性的微源，控制相对灵活，既可采用恒功率控制，也可在孤岛模式下作为电压源应用，称之为主电源。
微网既可以与大电网并联运行，也可以在电网故障下孤岛运行，独立为本地负载供电，具有较高的供电安全性和可靠性。微网的主要控制方法可归结为主从控制和下垂控制。由于主从控制可以方便地应用现有的商用逆变器，现阶段微网示范工程及相应研究仍以主从结构为主。它是依托一台功率稳定且容量较大的电源担负组网电源(如储能变流器)，在并网时采用PQ控制；在孤岛时工作于v/f模式，灵活快速调整有功/无功功率的吞吐，为其他DG提供电压频率支撑。因此，当微网在并网/孤岛模式间进行切换时，主逆变器的控制结构也需要进行相应调整，如何减少不同控制器的结构切换对系统动态性能的扰动，一直以来是主从结构下模式转换的难点。此外相对于传统电网，微电网惯性小，不论风、光等间歇性电源的输出功率波动、负载消耗功率以及模型参数摄动等一系列扰动均将引起显著的瞬时波动，如何保证DG快速、准确响应功率需求，保持负载电压稳定，对微电网的控制方法提出了挑战，尤其是实现并网/孤岛模式的平滑切换，已成为微网控制的重要技术特征。因此，微电网必须要有一套有效的控制系统，主动抑制微电网运行过程中供需功率扰动和控制结构扰动对系统动态性能的影响，使影响控制在合理范围内，甚至消除扰动，提升微网稳定性、动态性能，提高电能质量。
发明内容
技术问题：本发明所要解决的技术问题是：提供一种基于内模控制的微电网并离网平滑切换控制方法，该控制方法能够避免微电网并离网运行模式切换时不同逆变器控制环路切换带来的扰动，而且基于扰动观测器的内模控制可主动抑制供需功率扰动，并具有理想的跟踪性能和抗扰性能。
技术方案：为解决上述技术问题，本发明采取以下技术方案：
一种基于内模控制的微电网并离网平滑切换控制方法，该控制方法包括下述步骤：
步骤10)利用微电网能量管理器采集主电网运行信息，根据主电网的运行信息选择微电网操作模式，并下发操作指令到微电网主逆变器；若主电网正常运行，微电网工作于并网模式；若主电网发生故障，微电网工作于离网模式；
步骤20)主逆变器功率环采用下垂控制方式，产生主逆变器参考电压及参考频率，如式(1)和式(2)所示：
w
inv＝w
n-m(P-P
n) 式(2)
式中，
表示主逆变器本地输出电压参考指令，单位：千伏；v
n表示主逆变器输出电压的额定值，单位：千伏；n表示分布式电源的电压下垂特性系数，单位：千伏/兆乏；Q表示分布式电源实际输出无功功率，单位：兆乏；Q
n表示在额定电压下，分布式电源输出无功功率，单位：兆乏；w
inv表示主逆变器本地角频率参考指令，w
n表示主逆变器角频率额定值，单位：弧度/秒；m表示分布式电源的频率下垂特性系数，单位：弧度/秒·兆瓦；P表示分布式电源实际输出有功功率，单位：兆瓦；P
n表示在额定角频率下，分布式电源输出有功功率，单位：兆瓦；
步骤30)采集微电网运行数据，将基于扰动观测器的内模控制应用于电压电流双环控制器，提高控制系统鲁棒性和跟踪性能；
步骤40)根据微电网运行模式，进行电压和相位的控制：微电网由并网模式切换至离网模式时，保持上一时刻操作值，避免暂态扰动；微电网由离网模式切换至并网模式时，进行预同步操作，使偏差减小至允许范围内。
作为优选例，所述的步骤30)包括：电压外环采用比例积分控制器，如式(3)所示：
式中，
表示在dq参考坐标系下，电流环参考设定值
的d轴分量，单位：千安；k
up表示电压比例积分控制器中比例项系数，k
ui表示电压比例积分控制器中积分项系数，1/s表示积分作用；
表示在dq参考坐标系下，
的d轴分量，v
od表示在dq参考坐标系下，主逆变器输出电压v
o的d轴分量，C
f表示逆变器终端所连接的LC滤波器中电容器数值，单位:法拉；v
oq表示在dq参考坐标系下，主逆变器输出电压v
o的q轴分量，单位：千伏；
表示在dq参考坐标系下，电流环参考设定值
的q轴分量，单位：千安；
表示在dq参考坐标系下，
的q轴分量，单位：千伏；dq参考坐标系是指将abc交流坐标系经过派克变换得到的直流旋转坐标系；
电流内环采用比例控制器，如式(4)所示：
式中，v
id表示在dq参考坐标系下，主逆变器电流控制器输出的调制波电压的d轴分量，v
iq表示在dq参考坐标系下，主逆变器电流控制器输出的调制波电压的q轴分量，单位：千伏；k
ip表示电流比例控制器中比例项系数，i
id表示在dq参考坐标系下，主逆变器输出电流值的d轴分量，i
iq表示在dq参考坐标系下，主逆变器输出电流值的q轴分量，单位：千安；L
f表示逆变器终端所连接的LC滤波器中电感数值，单位：亨利；
根据式(3)和式(4)，建立电压电流双环模型作为广义被控对象，如式(5)所示：
式中，G(s)表示广义被控对象，k
pwm表示主逆变器电压增益，R
f表示滤波器中滤波电阻，s表示表示微分；
内模控制器前馈项如式(6)所示，扰动观测器前馈项如式(7)所示：
式中，f(s)表示内模控制前馈项的低通滤波器，G
n(s)表示广义被控对象的标称模型； λ表示f(s)的滤波时间常数，单位：秒；
表示L
f的标称值；
表示C
f的标称值；
表示R
f的标称值；Q(s)表示扰动观测器前馈项的低通滤波器，T
f表示Q(s)的滤波时间常数，单位:秒；
内模控制前馈项对应控制系统跟踪性能，通过前馈补偿将输入输出传递函数单位化，提高设定值跟踪性能；扰动观测器前馈项对应控制系统抗扰性能，实时估计微电网运行工况下等效功率扰动，并通过前馈补偿于电流环设定值，提高系统鲁棒性，将基于扰动观测器的内模控制应用于电压电流环，提高控制系统动态性能。
作为优选例，所述的步骤30)中，主逆变器本地输出电压参考指令
与主逆变器输出电压v
o的差值由电压外环消除。
作为优选例，所述的步骤30)中，扰动观测器前馈项实时估计微电网运行工况下等效功率扰动，所述扰动包括分布式电源功率输出扰动、负载消耗功率扰动以及模型参数摄动。
作为优选例，所述的步骤40)具体包括：首先对电网电压锁相，采集电网侧相角θ
g与主逆变器相角θ
inv进行比较，经过积分作用得到频率补偿量Δw
c，将频率补偿量Δw
c补偿于主逆变器本地角频率参考指令w
inv中；为保证微网侧频率及相角同时跟随电网侧额定值，需维持两侧相角重合状态一定时间，当满足设定时间时，频率预同步完成；对于幅值预同步，采集主逆变器输出电压v
o与电网侧额定电压v
g进行比较，经过积分作用得到电压补偿量Δv
c，将电压补偿量补偿于主逆变器本地输出电压参考指令
中；当微网侧和电网侧的相角偏差和电压幅值偏差同时减小至允许范围内，预同步过程完成，进行并网操作。
有益效果：与现有技术相比，本发明具有以下有益效果：在并网模式和离网模式下，主逆变器功率环都采用下垂控制产生电压环参考值及频率参考值，避免了常规算法中模式转换过程引起的控制环路切换，为实现微网工作模式的平滑过渡奠定基础；将基于扰动观测器的内模控制应用于电压电流双环控制结构，不仅能够有效抵消系统中供需功率不平衡的影响并提高对模型参数摄动的鲁棒性，同时优化控制环路跟踪性能，进一步改善模式切换过程的动态品质。该控制方法实现简单，只是在传统方案上增加线性控制结构，适用于采用数字信号处理器DSP等实现的逆变器算法，具有较好的实际推广价值。
图1是本发明实施例的流程图；
图2(a)是本发明实施例中电压下垂控制结构图；
图2(b)是本发明实施例中频率下垂控制结构图；
图3是本发明实施例中基于内模控制的电压电流双环控制结构图；
图4(a)是本发明实施例中微电网过渡过程中相位预同步控制框图；
图4(b)是本发明实施例中微电网过渡过程中电压预同步控制框图；
图5是本发明实施例中中采用的微电网仿真系统图；
图6(a)是本发明实施例中并网转孤岛模式主逆变器输出电压仿真结果；
图6(b)是本发明实施例中并网转孤岛模式主逆变器输出电流仿真结果；
图7(a)是采用传统无内模控制的并网转孤岛模式主逆变器输出电压仿真结果；
图7(b)是采用传统无内模控制的并网转孤岛模式主逆变器输出电流仿真结果；
图8(a)是本发明实施例中孤岛模式主逆变器输出电压仿真结果；
图8(b)是本发明实施例中孤岛模式主逆变器输出电流仿真结果；
图8(c)是本发明实施例中孤岛模式微电网角频率仿真结果。
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施案例对本发明进行深入地详细说明。应当理解，此处所描述的具体实施案例仅仅用以解释本发明，并不用于限定发明。
如图1所示，本发明实施例的一种基于内模控制的微电网并离网平滑切换控制方法，包括下述步骤：
步骤10)利用微电网能量管理器采集主电网运行信息，根据主电网的运行信息选择微电网操作模式，并下发操作指令到微电网主逆变器。若主电网正常运行，微电网工作于并网模式；若主电网发生故障，微电网工作于离网模式。
步骤20)主逆变器功率环采用下垂控制方式，产生主逆变器参考电压及参考频率，如式(1)和式(2)所示：
w
inv＝w
n-m(P-P
n) 式(2)
式中，
表示主逆变器本地输出电压参考指令，单位：千伏；v
n表示主逆变器输出电压的额定值，单位：千伏；n表示分布式电源的电压下垂特性系数，单位：千伏/兆乏；Q表示分布式电源实际输出无功功率，单位：兆乏；Q
n表示在额定电压下，分布式电源输出无功功率，单位：兆乏；w
inv表示主逆变器本地角频率参考指令，w
n表示主逆变器角频率额定值，单位：弧度/秒；m表示分布式电源的频率下垂特性系数，单位：弧度/秒·兆瓦；P表示分布式电源实际输出有功功率，单位：兆瓦；P
n表示在额定角频率下，分布式电源输出有功功率，单位：兆瓦。
实际中，v
n和w
n取为电网侧额定值。微电网并网运行时，主逆变器本地输出电压参考指令
和角频率参考指令w
inv受大电网钳制，输出有功功率P
n、无功功率Q
n。微电网离网运行时，主逆变器作为主电源承担系统的电压/频率支撑，维持功率平衡。
步骤30)采集微电网运行数据，将基于扰动观测器的内模控制应用于电压电流双环控制器，提高控制系统鲁棒性和跟踪性能。
具体来说，步骤30)包括：电压外环采用比例积分控制器，如式(3)所示：
式中，
表示在dq参考坐标系下，电流环参考设定值
的d轴分量，单位：千安；k
up表示电压比例积分控制器中比例项系数，k
ui表示电压比例积分控制器中积分项系数，1/s表示积分作用；
表示在dq参考坐标系下，
的d轴分量，v
od表示在dq参考坐标系下，主逆变器输出电压v
o的d轴分量，C
f表示逆变器终端所连接的LC滤波器中电容器数值，单位:法拉；v
oq表示在dq参考坐标系下，主逆变器输出电压v
o的q轴分量，单位：千伏；
表示在dq参考坐标系下，电流环参考设定值
的q轴分量，单位：千安；
表示在dq参考坐标系下，
的q轴分量，单位：千伏；dq参考坐标系是指将abc交流坐标系经过派克变换得到的直流旋转坐标系；
电流内环采用比例控制器，如式(4)所示：
式中，v
id表示在dq参考坐标系下，主逆变器电流控制器输出的调制波电压的d轴分量，v
iq表示在dq参考坐标系下，主逆变器电流控制器输出的调制波电压的q轴分量，单位：千伏；k
ip表示电流比例控制器中比例项系数，i
id表示在dq参考坐标系下，主逆 变器输出电流值的d轴分量，i
iq表示在dq参考坐标系下，主逆变器输出电流值的q轴分量，单位：千安；L
f表示逆变器终端所连接的LC滤波器中电感数值，单位：亨利；
根据式(3)和式(4)，建立电压电流双环模型作为广义被控对象，如式(5)所示：
式中，G(s)表示广义被控对象，k
pwm表示主逆变器电压增益，R
f表示滤波器中滤波电阻，s表示表示微分；
内模控制器前馈项如式(6)所示，扰动观测器前馈项如式(7)所示：
式中，f(s)表示内模控制前馈项的低通滤波器，G
n(s)表示广义被控对象的标称模型；λ表示f(s)的滤波时间常数，单位：秒；
表示L
f的标称值；
表示C
f的标称值；
表示R
f的标称值；Q(s)表示扰动观测器前馈项的低通滤波器，T
f表示Q(s)的滤波时间常数，单位:秒；
内模控制前馈项对应控制系统跟踪性能，通过前馈补偿将输入输出传递函数单位化，提高设定值跟踪性能；扰动观测器前馈项对应控制系统抗扰性能，实时估计微电网运行工况下等效功率扰动，并通过前馈补偿于电流环设定值，提高系统鲁棒性，将基于扰动观测器的内模控制应用于电压电流环，提高控制系统动态性能。
作为优选，所述的步骤30)中，为提高电流内环响应速度，电流内环采用比例控制器，主逆变器本地输出电压参考指令
与主逆变器输出电压v
o的差值由电压外环消除。
步骤30)中，扰动观测器前馈项实时估计微电网运行工况下等效功率扰动，所述扰动包括分布式电源功率输出扰动、负载消耗功率扰动以及模型参数摄动。
步骤30)中，内模控制器前馈项及扰动观测器前馈项的设计重点分别为滤波时间常数λ和T
f。在实际调试过程中，首先假设模型无差，调试λ使控制器跟踪性能最优；再加入扰动观测器前馈项，调试T
f提高系统抗扰性能。
步骤40)根据微电网运行模式，进行电压和相位的控制：微电网由并网模式切换至离网模式时，保持上一时刻操作值，避免暂态扰动；微电网由离网模式切换至并网模式时，进行预同步操作，使偏差减小至允许范围内。所述的步骤40)具体包括：首先对电 网电压锁相。本实施例中优选使用二阶广义积分提取正序分量，可以避免不平衡负载等影响。采集电网侧相角θ
g与主逆变器相角θ
inv进行比较，经过积分作用得到频率补偿量Δw
c，将频率补偿量Δw
c补偿于主逆变器本地角频率参考指令w
inv中；为保证微网侧频率及相角同时跟随电网侧额定值，需维持两侧相角重合状态一定时间，当满足设定时间时，频率预同步完成；对于幅值预同步，采集主逆变器输出电压v
o与电网侧额定电压v
g进行比较，经过积分作用得到电压补偿量Δv
c，将电压补偿量补偿于主逆变器本地输出电压参考指令
中；当微网侧和电网侧的相角偏差和电压幅值偏差同时减小至允许范围内，预同步过程完成，进行并网操作。
通过以上步骤，形成了基于内模控制的微电网平滑切换控制方法。在微电网离网/并网模式下，功率环采用下垂控制，避免不同运行模式切换引起的控制环路切换；将基于扰动观测器的内模控制应用于电压电流环，实现了微电网操作过程中功率扰动影响的主动抑制以及设定值跟踪性能的改善，提升了系统稳定性和动态性能。相比于其他微电网平滑切换方法，本控制方法同时抑制了控制结构扰动和功率扰动。
本发明实施例中的微电网电压下垂控制框图如2(a)所示，频率下垂控制框图如图2(b)所示。电压下垂控制通过主逆变器输出无功功率与输出电压之间的关系得到电压参考值。频率下垂控制通过主逆变器输出有功功率与频率之间的关系得到逆变器参考频率，进而得到逆变器相角。
本发明实施例中的基于内模控制的电压电流双环控制框图如3所示，该控制框图主要包括三部分，一部分是基本的电压电流双环控制器，一部分是扰动观测器前馈项，最后一部分是内模控制器前馈项。电压电流双环中电流内环采用比例控制器，环路误差由电压控制器消除。扰动观测器通过比较电流环设定值与逆变器输出电压，实时估计出等效功率扰动，并前馈补偿于电流设定值中。内模控制器前馈项通过设定值前馈补偿将输入输出传递函数单位化，提高了跟踪性能。通过上述作用，反馈通道与前馈通道相互补充，满足二自由度设计准则，实现了微电网操作过程中跟踪性能与抗扰性能的同步改善，提升了系统动态品质。
本发明实施例中的相角预同步控制框图如4(a)所示，通过电网相位提取环节基于二阶广义积分提取电网侧dq变换参考相位，为微电网并网运行或者预同步操作过程提供相角参考；当预同步指令触发预同步模块时，通过比例积分调整逆变器侧角频率使逆变器侧相角同步跟随电网侧相角。本发明实施例中的电压幅值预同步控制框图如4(b) 所示，通过比例积分调整逆变器输出电压跟随电网侧电压幅值。当微电网侧与电网侧相角差、电压幅值差都小于阀值时下发并网指令，有效实现了离网至并网模式的无缝切换。
下面例举一个实施例。
仿真系统如图5所示，由能量管理器、静态开关STS、主逆变器(储能单元)和若干从逆变器(光伏逆变器/风电逆变器)以及用电负荷等构成。能量管理器采集电网侧信号，决定微电网运行模式。在不同运行模式下，风电逆变器、光伏逆变器处于PQ控制模式，因此微电网操作运行的重点是主逆变器控制方法。正常情况下，微电网并网运行，STS闭合。微电网侧电压、频率决定于电网侧，主逆变器根据设定的下垂控制输出额定有功功率和无功功率。当主电网故障，系统进入离网模式，STS断开，主逆变器根据下垂控制提供微网频率、电压支撑。基于MATLAB/Simulink平台搭建仿真微电网模型，分别对微电网并离网模式切换及孤岛微电网发生加载或减载等情况进行了仿真，比较本发明实施例的微电网控制方法与传统的微电网控制方法的差异。传统的并离网控制方法是在切换瞬间使当前的控制器控制量跟随先前的控制器控制量，只包含基本的电压电流双环反馈通道，不含设定值内模控制前馈项和负载电流扰动观测前馈通道。
图6为微电网采用本发明控制方法的微电网并网转孤岛仿真结果。相对于计划性孤岛，非计划孤岛实现平滑切换难度更高，尤其是联络线处有较大的功率传输时。开始时主逆变器运行于并网模式，由于下垂控制中额定有功功率P
n和无功功率Q
n为零，则逆变器零功率输出，负载功率全部由电网供给；0.2s时，电网故障导致微网进入孤岛模式，负载功率全部由微电网供给，电网侧功率供给为零。图6(a)给出了微电网由并网至孤岛运行模式切换过程中主逆变器输出电压波形，横坐标表示时间，单位：秒，纵坐标表示输出电压，单位：伏。如图6(a)所示，最初输出电压与电网侧额定值一致，进入孤岛后降低，但瞬时过程很短，两个周波调节稳定，三相电压未出现振荡。图6(b)给出了微电网由并网至孤岛运行模式切换过程中主逆变器输出电流波形，横坐标表示时间，单位：秒，纵坐标表示输出电流，单位：安。如图6(b)所示，由于主逆变器下垂额定功率设置为0，最初微网侧主逆变器电流输出为零，进入孤岛模式后输出电流快速增加，三相未没有出现振荡。由图6(a)、图6(b)可知，采用本控制方法能够实现并网/孤岛运行模式的无缝切换，过程平滑、切换时间短，这是由于切换过程整套控制环路保持一致，未发生控制器切换，而且新增加的内模控制器前馈项和扰动观测前馈项分别能够提前估计并补偿扰动，提高系统跟踪性能和抗扰性能，提高了系统动态特性。
为了显示本发明实施例中微电网运行控制策略的优势，图7为采用常规控制策略的微电网仿真结果。开始时主逆变器运行于并网模式，由于下垂控制中额定有功功率P
n和无功功率Q
n为零，则逆变器零功率输出，负载功率全部由电网供给；0.2s时，电网故障导致微网进入孤岛模式，负载功率全部由微电网供给，电网侧功率供给为零。图7(a)给出了微电网由并网至孤岛运行模式切换过程中主逆变器输出电压波形，横坐标表示时间，单位：秒，纵坐标表示输出电压，单位：伏。如图7(a)所示，最初输出电压与电网侧额定值一致，进入孤岛后降低，需要八九个周波才能稳定。图7(b)给出了微电网由并网至孤岛运行模式切换过程中主逆变器输出电流波形，横坐标表示时间，单位：秒，纵坐标表示输出电流，单位：安。如图7(b)所示，由于主逆变器下垂额定功率设置为0，最初微网侧主逆变器电流输出为零，进入孤岛模式后输出电流增加，初期出现了一定的畸变并且过渡过程出现振荡，这是由于虽然状态跟随能一定平缓运行过程，但在模式转化过程中控制环路发生控制器切换，导致控制过程出现振荡。而本发明实施例中由于采用跟踪值前馈项和扰动前馈项的补偿作用，如图6(a)、6(b)所示可以实现运行过程平滑切换。
图8所示为微电网孤岛模式下采用本发明方法进行加减载操作的仿真结果。系统首先运行于孤岛空载模式，0.2s时投入负载，0.4s时切除负载。图8(a)给出了微电网主逆变器输出电压波形，横坐标表示时间，单位：秒，纵坐标表示输出电压，单位：伏。图8(b)给出了微电网主逆变器输出电流波形，横坐标表示时间，单位：秒，纵坐标表示输出电流，单位：安。图8(c)给出了微电网主逆变器角频率波形，横坐标表示时间，单位：秒，纵坐标表示输出电流，单位：弧度/秒。由图可知，在孤岛模式下加载操作时，输出电压稍微降低、输出电流增加为负载提供功率，仅出现非常微小的抖动，很快进入稳态值；此时根据设定的下垂系数系统频率降低0.5Hz(即角频率降低πrad，约为311rad)，符合下垂特性。随后进行减载操作时，输出电压在一两个周波内恢复至额定值，而电流恢复至零输出，同时角频率升回至100π。本控制方法对孤岛模式下微电网具有良好的动态调节性能。
本发明实施例的控制方法是基于内模控制的微电网并离网平滑切换控制方法。针对微电网运行过程中存在的供需功率功率扰动，尤其是不同操作模式下不同控制器切换引起的结构扰动。本控制方法在功率环中采用下垂控制，避免不同控制器切换。此外，采用包含内模控制前馈项和扰动观测前馈项的改进电压电流双环结构，提高控制系统抗扰 性能和跟踪性能，实现了并离网无缝切换，平滑了动态过程，有效提高微电网的动态性能和电能质量。
以上显示和描述了本发明的基本原理、主要特征和优点。本领域的技术人员应该了解，本发明不受上述具体实施例的限制，上述具体实施例和说明书中的描述只是为了进一步说明本发明的原理，在不脱离本发明精神和范围的前提下，本发明还会有各种变化和改进，这些变化和改进都落入要求保护的本发明范围内。本发明要求保护的范围由权利要求书及其等效物界定。
Claims (5)
- 一种基于内模控制的微电网并离网平滑切换控制方法，其特征在于，该控制方法包括下述步骤：步骤10)利用微电网能量管理器采集主电网运行信息，根据主电网的运行信息选择微电网操作模式，并下发操作指令到微电网主逆变器；若主电网正常运行，微电网工作于并网模式；若主电网发生故障，微电网工作于离网模式；步骤20)主逆变器功率环采用下垂控制方式，产生主逆变器参考电压及参考频率，如式(1)和式(2)所示：
w inv＝w n-m(P-P n) 式(2)式中，表示主逆变器本地输出电压参考指令，单位：千伏；v n表示主逆变器输出电压的额定值，单位：千伏；n表示分布式电源的电压下垂特性系数，单位：千伏/兆乏；Q表示分布式电源实际输出无功功率，单位：兆乏；Q n表示在额定电压下，分布式电源输出无功功率，单位：兆乏；w inv表示主逆变器本地角频率参考指令，w n表示主逆变器角频率额定值，单位：弧度/秒；m表示分布式电源的频率下垂特性系数，单位：弧度/秒·兆瓦；P表示分布式电源实际输出有功功率，单位：兆瓦；P n表示在额定角频率下，分布式电源输出有功功率，单位：兆瓦；
步骤30)采集微电网运行数据，将基于扰动观测器的内模控制应用于电压电流双环控制器，提高控制系统鲁棒性和跟踪性能；步骤40)根据微电网运行模式，进行电压和相位的控制：微电网由并网模式切换至离网模式时，保持上一时刻操作值，避免暂态扰动；微电网由离网模式切换至并网模式时，进行预同步操作，使偏差减小至允许范围内。 - 按照权利要求1所述的基于内模控制的微电网并离网平滑切换控制方法，其特征在于，所述的步骤30)包括：电压外环采用比例积分控制器，如式(3)所示：
式中，表示在dq参考坐标系下，电流环参考设定值
的d轴分量，单位：千安；k up表示电压比例积分控制器中比例项系数，k ui表示电压比例积分控制器中积分项系数，1/s表示积分作用；
表示在dq参考坐标系下，
的d轴分量，v od表示在dq参考坐标系下，主逆变器输出电压v o的d轴分量，C f表示逆变器终端所连接的LC滤波器中电容器数 值，单位:法拉；v oq表示在dq参考坐标系下，主逆变器输出电压v o的q轴分量，单位：千伏；
表示在dq参考坐标系下，电流环参考设定值
的q轴分量，单位：千安；
表示在dq参考坐标系下，
的q轴分量，单位：千伏；dq参考坐标系是指将abc交流坐标系经过派克变换得到的直流旋转坐标系；
电流内环采用比例控制器，如式(4)所示：
式中，v id表示在dq参考坐标系下，主逆变器电流控制器输出的调制波电压的d轴分量，v iq表示在dq参考坐标系下，主逆变器电流控制器输出的调制波电压的q轴分量，单位：千伏；k ip表示电流比例控制器中比例项系数，i id表示在dq参考坐标系下，主逆变器输出电流值的d轴分量，i iq表示在dq参考坐标系下，主逆变器输出电流值的q轴分量，单位：千安；L f表示逆变器终端所连接的LC滤波器中电感数值，单位：亨利；根据式(3)和式(4)，建立电压电流双环模型作为广义被控对象，如式(5)所示：
式中，G(s)表示广义被控对象，k pwm表示主逆变器电压增益，R f表示滤波器中滤波电阻，s表示表示微分；内模控制器前馈项如式(6)所示，扰动观测器前馈项如式(7)所示：
式中，f(s)表示内模控制前馈项的低通滤波器，G n(s)表示广义被控对象的标称模型；λ表示f(s)的滤波时间常数，单位：秒；表示L f的标称值；
表示C f的标称值；
表示R f的标称值；Q(s)表示扰动观测器前馈项的低通滤波器，T f表示Q(s)的滤波时间常数，单位:秒；
内模控制前馈项对应控制系统跟踪性能，通过前馈补偿将输入输出传递函数单位化，提高设定值跟踪性能；扰动观测器前馈项对应控制系统抗扰性能，实时估计微电网运行工况下等效功率扰动，并通过前馈补偿于电流环设定值，提高系统鲁棒性，将基于扰动观测器的内模控制应用于电压电流环，提高控制系统动态性能。 - 按照权利要求1所述的基于内模控制的微电网并离网平滑切换控制方法，其特征在于，所述的步骤30)中，主逆变器本地输出电压参考指令与主逆变器输出电压v o的差值由电压外环消除。
- 按照权利要求1所述的基于内模控制的微电网并离网平滑切换控制方法，其特征在于，所述的步骤30)中，扰动观测器前馈项实时估计微电网运行工况下等效功率扰动，所述扰动包括分布式电源功率输出扰动、负载消耗功率扰动以及模型参数摄动。
- 按照权利要求1所述的基于内模控制的微电网并离网平滑切换控制方法，其特征在于，所述的步骤40)具体包括：首先对电网电压锁相，采集电网侧相角θ g与主逆变器相角θ inv进行比较，经过积分作用得到频率补偿量Δw c，将频率补偿量Δw c补偿于主逆变器本地角频率参考指令w inv中；为保证微网侧频率及相角同时跟随电网侧额定值，需维持两侧相角重合状态一定时间，当满足设定时间时，频率预同步完成；对于幅值预同步，采集主逆变器输出电压v o与电网侧额定电压v g进行比较，经过积分作用得到电压补偿量Δv c，将电压补偿量补偿于主逆变器本地输出电压参考指令中；当微网侧和电网侧的相角偏差和电压幅值偏差同时减小至允许范围内，预同步过程完成，进行并网操作。
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| CN108736576A (zh) * | 2018-06-01 | 2018-11-02 | 三峡大学 | 一种基于内模鲁棒控制的超导磁储能电压控制方法 |
| CN108808665B (zh) * | 2018-06-14 | 2019-12-17 | 广西电网有限责任公司电力科学研究院 | 一种逆变型分布式电源并网暂态稳定性的判断方法 |
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| CN113328429B (zh) * | 2021-04-25 | 2022-05-24 | 湖南大学 | 一种并-离网平滑切换与离网滚动优化调度方法、设备及介质 |
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