Cooperative control method of DC distribution system based on distributed model predictive control

Abstract

The present invention belongs to the field of predictive control technology, and relates to a method for coordinated control of a DC power distribution system based on distributed model predictive control, the steps of which include: in a DC power distribution system, the power module at the power supply end is equivalent to a voltage source power module, and the distributed power supply unit and the DC load are equivalent to a load power module; the state space equations of the voltage source power module and the load power module are established; the objective function is established respectively with the minimum value of the incremental weighted sum of the output voltage deviation and the inertia adjustment coefficient of the voltage source power module as the optimization target, and the minimum value of the weighted sum of the current signal and the output duty cycle of the load power module as the target; the consistency voltage-power controller is improved to achieve the final coordinated control. The present invention eliminates the voltage observation error caused by the time delay, can accurately estimate the actual mean value of the system voltage, and realizes the compensation of the output voltage of the voltage source power module and the precise distribution of power.

Description

Technical Field

[0001] The present invention belongs to the technical field of predictive control, and in particular relates to a coordinated control method for a DC power distribution system based on distributed model predictive control. Background Art

[0002] At present, the large-scale access of distributed power sources and DC loads represented by electric vehicles has posed new challenges to the reliability and flexibility of traditional distribution networks. With the development of power electronic converters, DC distribution systems have received increasing attention due to their advantages such as flexibility and control, long power supply radius, and large power supply capacity. However, with the rapid increase in the installed capacity of renewable energy power generation, the consumption of renewable energy has become a difficult problem that the power system needs to solve urgently. The DC distribution system can accommodate distributed power sources more flexibly and efficiently, and has become an important development trend of modern distribution systems, but the DC distribution system is a typical low-inertia, weak-damping system. For systems using traditional droop control, the randomness of renewable energy output and the sudden change of load power may cause DC voltage oscillation and even induce system instability.

[0003] At present, distributed cooperative control represented by consistency control has been widely used in multi-terminal DC distribution systems. It is based on sparse communication between adjacent nodes, and can achieve control under low communication requirements. It has the advantages of consistent control variables, flexibility and reliability. However, compared with DC microgrids, DC distribution systems have more nodes and a wider power supply range, which also leads to an increase in the physical distance between converters in the system and between local control and upper-level controllers. At the same time, the DC distribution system is in its early development stage, and the communication equipment is still imperfect. Due to the differences in communication networks in various regions and the performance of communication equipment, communication delay has a great impact on the performance of distributed cooperative control. Therefore, combined with the characteristics of DC distribution systems with many points and wide areas, considering the construction economy of actual DC distribution systems and the impact of communication delay on control performance, a distributed cooperative control strategy for multi-terminal DC distribution systems with certain delay resistance is studied, which can eliminate the voltage deviation problem caused by communication delay while realizing DC voltage oscillation control, which is of great significance for the promotion and application of DC distribution systems. Summary of the invention

[0004] In view of the above deficiencies in the prior art, the present invention provides a collaborative control method for a DC distribution system based on distributed model predictive control, which eliminates the voltage observation error caused by time delay and realizes accurate estimation of the actual mean value of the system voltage; through dynamic consistency control of voltage and power, compensation of the output voltage of the voltage source power module and precise distribution of power are realized.

[0005] To achieve the above objectives, the present invention provides a DC power distribution system coordinated control method based on distributed model predictive control, comprising the following steps:

[0006] S1. In the DC power distribution system, the power module at the power supply end is equivalent to a voltage source power module, and the distributed power supply unit and the DC load are equivalent to a load power module;

[0007] S2, inertia adjustment coefficient As the input control variable, the state space equation of the i-th voltage source type power module is established;

[0008] S3, filter current and output voltage As the state variable, establish the state space equation of the kth load-type power module;

[0009] S4, based on the output voltage deviation of the voltage source power module and The minimum value of the incremental weighted square sum is the optimization goal, the objective function is established, and its constraints are set;

[0010] S5. Based on the disturbance source positioning index of the voltage source power module ,as well as The oscillation situation can be adjusted adaptively ;

[0011] S6. Taking the minimum value of the weighted square sum of the current signal of the load-type power module and the output duty cycle as the target, establish the objective function, and locate the disturbance source index of the load-type power module according to the load-type power module And the output voltage deviation of the load-type power module, adaptively handle the transient response of voltage control;

[0012] S7, The measurable output value of the Luenberger Observer is designed to accurately estimate the The instantaneous state value of

[0013] S8. Design a consistent voltage-power controller to achieve coordinated control;

[0014] S9. Improve the consistent voltage-power controller to achieve ultimate coordinated control.

[0015] In the above S1, according to the characteristics of the power module at the power supply end in the DC power distribution system, the power module at the power supply end is equivalent to a voltage source type power module; according to the negative impedance characteristics of the distributed power supply unit and the DC load in the DC power distribution system, the distributed power supply unit and the DC load are equivalent to a load type power module.

[0016] In the S2, As the input control variable, the state space equation of the i-th voltage source power module is established as:

[0017] ;

[0018] In the formula, , , , are the droop coefficient, voltage measured value, voltage reference value, and power measured value of the i-th voltage source power module respectively; and are the measured values ​​of the d-axis current and q-axis current of the i-th voltage source type power module respectively; , is the control parameter of the voltage outer loop of the i-th voltage source type power module; , are the proportional coefficient and integral coefficient of the d-axis current inner loop of the i-th voltage source power module respectively; , are the proportional coefficient and integral coefficient of the q-axis current inner loop of the i-th voltage source power module respectively; , are the AC side filter inductance and equivalent resistance of the i-th voltage source power module respectively; , is the switching function of the dq axis current; is an intermediate variable; , , are the intermediate variables of the proportional-integral link of the i-th voltage source power module; is the output current of the DC side of the i-th voltage source power module; is the capacitance on the DC side of the i-th voltage source power module; T is the time constant of the high-pass filter; t is time, and d is the differential sign.

[0019] In the S3, and The state space equation for the kth load-type power module is established as:

[0020] ;

[0021] In the formula, , Divided into the duty cycle and the steady-state value of the duty cycle of the kth load-type power module; , are the DC bus voltage and its steady-state value respectively; is the filter inductance at the output side of the kth load-type power module; is the filter capacitor on the output side of the kth load-type power module; is the output side load of the kth load-type power module.

[0022] In the above S4, the objective function is:

[0023] ;

[0024] Where J is the objective function, which represents the output voltage deviation and The incremental weighted sum of squares of ; , They are the output voltage matrix and reference voltage matrix of the voltage source power module at time h respectively; is the value of the i-th voltage source power module The incremental weight coefficient of ; is the inertia adjustment coefficient matrix of the voltage source power module at time h; p is the prediction time domain, M is the control time domain, and M≤p is satisfied; represents the increment of discrete variables at adjacent moments; f is the prediction moment;

[0025] The constraints are:

[0026] ;

[0027] In the formula, is the maximum active power of the i-th voltage source power module; , They are the minimum control increment and the maximum control increment that the voltage source type power module can withstand respectively; It is the actual control increment of the voltage source type power module.

[0028] The S5 adaptively adjusts The way is, for :

[0029] when hour, The increment is greater than the maximum control increment that the DC power distribution system can withstand. Keep it at the minimum value, limiting the control increment while ensuring the maximum control effect;

[0030] when hour, The increment is within the maximum range that the DC power distribution system can bear. Adaptive adjustment according to the status of DC power distribution system;

[0031] thus, It is expressed as:

[0032] ;

[0033] In the formula, for The minimum value of (this minimum value is determined by the different characteristics of the DC power distribution system, specifically according to the control structure, circuit parameters, etc. of the DC power distribution system); , are the voltage reference value and the voltage measured value of the i-th voltage source type power module at time h respectively; It is the actual control increment of the voltage source power module at time h-1.

[0034] In the above S6, the objective function established is:

[0035] ;

[0036] In the formula, is the weighted square sum of the current signal and output duty cycle of the kth load-type power module; , are respectively the current signal of the kth load-type power module at time h and the current signal reference value; is the duty cycle increment weight coefficient of the kth load-type power module; is the duty cycle of the kth load-type power module at time h;

[0037] pass Adaptively handles transient response of voltage control, It is expressed as:

[0038] ;

[0039] In the formula, , are the output voltage and voltage reference value of the kth load-type power module at time h respectively; The initial value of the weight coefficient of the kth load-type power module control incremental target item.

[0040] In S7, the Luenberger Observer is expressed as:

[0041] ;

[0042] , , ;

[0043] ;

[0044] In the formula, , are the estimated values ​​of the state variables and output variables of the kth load-type power module; is the deviation between the state variable of the kth load-type power module and the estimated value of the state variable; , are the state variables and output variables of the kth load-type power module; The output duty cycle of the kth load-type power module; , , are the coefficient of the estimated value of the state variable of the kth load-type power module, the coefficient of the output duty cycle, and the coefficient of the estimated value of the output variable; yes The differential form of .

[0045] In the above-mentioned S8, the designed consistent voltage-power controller is expressed as:

[0046] ;

[0047] in:

[0048] ;

[0049] In the formula, , are the voltage observation values ​​of the i-th voltage source type power module and the j-th voltage source type power module respectively; is the neighbor node set of the i-th voltage source power module; is the power allocation deviation of the i-th voltage source power module; is the output voltage of the i-th voltage source type power module; , They are the gain of voltage consistency control and the gain of management consistency control; , are the output power deviations of the i-th voltage source type power module and the j-th voltage source type power module respectively; is the output power of the i-th voltage source power module; represents the communication weight between the i-th voltage source type power module and the j-th voltage source type power module; is the integration variable.

[0050] In the above-mentioned S9, the improved consistent voltage-power controller is expressed as:

[0051] ;

[0052] In the formula, is the input reference command adjustment value of the voltage outer loop of the i-th voltage source type power module; yes The differential form of , are the voltage consistency coefficient and power consistency coefficient of the i-th voltage source type power module respectively; is the deviation coefficient of the i-th voltage source power module; , are the intermediate variables introduced by the i-th voltage source type power module and the j-th voltage source type power module respectively; yes The differential form of ; N is the number of voltage source power modules.

[0053] The algorithm involved in the present invention can be executed by an electronic device. The electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. The algorithm is implemented by executing the program by the processor.

[0054] The beneficial effects of the present invention are:

[0055] The present invention proposes a virtual inertia control method based on voltage feedforward compensation, optimizes virtual inertia parameters through decentralized model predictive control, and effectively enhances the inertia support of the system by the local control of the voltage source power module; for the load power module, combined with the voltage deviation and the disturbance source positioning index, it proposes a method of using adaptive model predictive control as the current control link, thereby improving the dynamic performance of the converter. During collaborative control, in order to solve the problems of uneven power distribution and large voltage deviation caused by factors such as line impedance and communication delay, a voltage-power controller based on an improved consistency algorithm is proposed, which eliminates the voltage observation error caused by the delay and realizes the accurate estimation of the actual mean value of the system voltage; through the dynamic consistency control of voltage and power, the output voltage compensation of the voltage source power module and the precise distribution of power are realized.

[0056] The present invention designs an adaptive model predictive control based on the output voltage deviation of the load-type power module and the disturbance source positioning index. The designed adaptive model predictive control is used to process the transient response of voltage control, and the voltage control link only needs to compensate for the signal offset caused by parameter uncertainty, which effectively improves the transient response performance of the module.

[0057] The present invention adopts an improved consistency voltage-power controller, which eliminates the voltage observation error caused by time delay by designing an improved observer, and realizes accurate estimation of the actual mean value of system voltage. At the same time, through the dynamic consistency control of voltage and power, the output voltage compensation of voltage source power module and the accurate distribution of power are realized.

[0058] The present invention eliminates the voltage observation error caused by time delay and realizes accurate estimation of the actual mean value of system voltage; through dynamic consistency control of voltage and power, compensation of output voltage of voltage source power module and accurate distribution of power are realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a schematic diagram of the process of the present invention;

[0060] Figure 2 It is a topological structure diagram of a four-terminal DC distribution network in the verification process of the present invention;

[0061] Figure 3 It is a schematic diagram of the DC bus voltage oscillation in Verification Example 1 of the present invention;

[0062] Figure 4 It is a schematic diagram of the dynamic situation of the output voltage of the voltage source type power module 1-4 in the verification example 1 of the present invention;

[0063] Figure 5 Schematic diagram of the dynamic situation of the output power of the voltage source type power modules 1-4 in the verification example 1 of the present invention;

[0064] Figure 6 It is a schematic diagram of the dynamic situation of the output voltage of the load-type power module 1 in the verification example 1 of the present invention;

[0065] Figure 7 It is a schematic diagram of the dynamic situation of the output voltage of the load-type power module 2 in the verification example 1 of the present invention;

[0066] Figure 8 It is a schematic diagram of the output voltage curve of the voltage source type power module 1-4 under the method proposed in this patent in Verification Example 2 of the present invention;

[0067] Fig. 9 It is a schematic diagram of the output voltage curve of the voltage source type power module 1-4 under the existing control method in Verification Example 2 of the present invention. DETAILED DESCRIPTION

[0068] The embodiments of the present invention are further described below in conjunction with the accompanying drawings:

[0069] like Figure 1 As shown, the coordinated control method of a DC power distribution system based on distributed model predictive control includes the following steps:

[0070] S1. In the DC power distribution system, the power module at the power supply end is equivalent to a voltage source power module, and the distributed power supply unit and the DC load are equivalent to a load power module;

[0071] S2. The random disturbance caused by the lack of inertial rotating equipment in the DC power distribution system is likely to cause DC voltage oscillation. As the input control variable, the state space equation of the i-th voltage source type power module is established;

[0072] S3. In order to solve the problem that the load-type power module controller cannot fully utilize the dynamic characteristics of the converter and has poor transient response, the distributed model predictive control is used as the current inner loop part of the load-type power module voltage control to filter the current. and output voltage As the state variable, establish the state space equation of the kth load-type power module;

[0073] S4, based on the output voltage deviation of the voltage source power module and The minimum value of the incremental weighted square sum is the optimization goal, the objective function is established, and its constraints are set;

[0074] S5. Based on the disturbance source positioning index of the voltage source power module ,as well as The oscillation situation can be adjusted adaptively ;

[0075] S6. Taking the minimum value of the weighted square sum of the current signal of the load-type power module and the output duty cycle as the target, establish the objective function, and locate the disturbance source index of the load-type power module according to the load-type power module And the output voltage deviation of the load-type power module, adaptively handle the transient response of voltage control;

[0076] S7, The measurable output value of the Luenberger Observer is designed to accurately estimate the The instantaneous state value of

[0077] S8. Design a consistent voltage-power controller to achieve coordinated control;

[0078] S9. Improve the consistent voltage-power controller to achieve ultimate coordinated control.

[0079] for and , can be obtained according to the prior art, for example, based on the following paper:

[0080] Z. Zhao, K. Peng, R. Xian and X. Zhang. Localization of oscillation source in DC distribution network based on power spectral density [J]. Journal of Modern Power Systems and Clean Energy, 2023, 11(01): 156-167.

[0081] In S1, according to the characteristics of the power module at the power supply end in the DC distribution system, the power module at the power supply end is equivalent to a voltage source type power module; according to the negative impedance characteristics of the distributed power supply units represented by wind turbines and photovoltaics and the DC loads represented by energy storage units and electric vehicles in the DC distribution system, the distributed power supply units and DC loads are equivalent to load type power modules.

[0082] In S2, a virtual inertia control of the current control link is proposed in combination with a high-pass filter, and an inertia adjustment coefficient is introduced in this process. When the DC power distribution system oscillates due to disturbance, the designed decentralized model predictive control is used based on local information. Real-time optimization was performed to solve the problem of voltage oscillation instability at the local control layer. As the input control variable, the state space equation of the i-th voltage source power module is established as:

[0083] ;

[0084] In the formula, , , , are the droop coefficient, voltage measured value, voltage reference value, and power measured value of the i-th voltage source power module respectively; and are the measured values ​​of the d-axis current and q-axis current of the i-th voltage source type power module respectively; , is the control parameter of the voltage outer loop of the i-th voltage source type power module; , are the proportional coefficient and integral coefficient of the d-axis current inner loop of the i-th voltage source power module respectively; , are the proportional coefficient and integral coefficient of the q-axis current inner loop of the i-th voltage source power module respectively; , are the AC side filter inductance and equivalent resistance of the i-th voltage source power module respectively; , is the switching function of the dq axis current; is an intermediate variable; , , are the intermediate variables of the proportional-integral link of the i-th voltage source power module; is the output current of the DC side of the i-th voltage source power module; is the capacitance on the DC side of the i-th voltage source power module; T is the time constant of the high-pass filter; t is time, and d is the differential sign.

[0085] In S3, and The state space equation for the kth load-type power module is established as:

[0086] ;

[0087] In the formula, , Divided into the duty cycle and the steady-state value of the duty cycle of the kth load-type power module; , are the DC bus voltage and its steady-state value respectively; is the filter inductance at the output side of the kth load-type power module; is the filter capacitor on the output side of the kth load-type power module; is the output side load of the kth load-type power module.

[0088] In S4, the objective function is:

[0089] ;

[0090] Where J is the objective function, which represents the output voltage deviation and The incremental weighted sum of squares of ; , They are the output voltage matrix and reference voltage matrix of the voltage source power module at time h respectively; is the value of the i-th voltage source power module The incremental weight coefficient of ; is the inertia adjustment coefficient matrix of the voltage source power module at time h; p is the prediction time domain, M is the control time domain, and M≤p is satisfied; represents the increment of discrete variables at adjacent moments; f is the prediction moment;

[0091] The constraints are:

[0092] ;

[0093] In the formula, is the maximum active power of the i-th voltage source power module; , They are the minimum control increment and the maximum control increment that the voltage source type power module can withstand respectively; It is the actual control increment of the voltage source type power module.

[0094] In S5, adaptive adjustment The way is, for :

[0095] when hour, The increment is greater than the maximum control increment that the DC power distribution system can withstand. Keep it at the minimum value, limiting the control increment while ensuring the maximum control effect;

[0096] when hour, The increment is within the maximum range that the DC power distribution system can bear. Adaptive adjustment according to the status of DC power distribution system;

[0097] thus, It is expressed as:

[0098] ;

[0099] In the formula, for The minimum value of , are the voltage reference value and the voltage measured value of the i-th voltage source type power module at time h respectively; It is the actual control increment of the voltage source power module at time h-1.

[0100] In S6, the objective function established is:

[0101] ;

[0102] In the formula, is the weighted square sum of the current signal and output duty cycle of the kth load-type power module; , are respectively the current signal of the kth load-type power module at time h and the current signal reference value; is the duty cycle increment weight coefficient of the kth load-type power module; is the duty cycle of the kth load-type power module at time h;

[0103] pass Adaptively handles transient response of voltage control, It is expressed as:

[0104] ;

[0105] In the formula, , are the output voltage and voltage reference value of the kth load-type power module at time h respectively; The initial value of the weight coefficient of the kth load-type power module control incremental target item.

[0106] In S7, the Luenberger Observer is expressed as:

[0107] ;

[0108] , , ;

[0109] ;

[0110] In the formula, , are the estimated values ​​of the state variables and output variables of the kth load-type power module; is the deviation between the state variable of the kth load-type power module and the estimated value of the state variable; , are the state variables and output variables of the kth load-type power module; The output duty cycle of the kth load-type power module; , , are the coefficient of the estimated value of the state variable of the kth load-type power module, the coefficient of the output duty cycle, and the coefficient of the estimated value of the output variable; yes The differential form of .

[0111] In S8, at the collaborative control layer, the designed consistent voltage-power controller is expressed as follows to address the problem of decreased voltage and power control accuracy of the DC power distribution system caused by line impedance:

[0112] ;

[0113] in:

[0114] ;

[0115] In the formula, , are the voltage observation values ​​of the i-th voltage source type power module and the j-th voltage source type power module respectively; is the neighbor node set of the i-th voltage source power module; is the power allocation deviation of the i-th voltage source power module; is the output voltage of the i-th voltage source type power module; , They are the gain of voltage consistency control and the gain of management consistency control; , are the output power deviations of the i-th voltage source type power module and the j-th voltage source type power module respectively; is the output power of the i-th voltage source power module; represents the communication weight between the i-th voltage source type power module and the j-th voltage source type power module; is the integration variable.

[0116] In S9, the improved consistent voltage-power controller is expressed as:

[0117] ;

[0118] In the formula, is the input reference command adjustment value of the voltage outer loop of the i-th voltage source type power module; yes The differential form of , are the voltage consistency coefficient and power consistency coefficient of the i-th voltage source type power module respectively; is the deviation coefficient of the i-th voltage source power module; , are the intermediate variables introduced by the i-th voltage source type power module and the j-th voltage source type power module respectively; yes The differential form of ; N is the number of voltage source power modules.

[0119] The verification process is:

[0120] The effectiveness and superiority of the present invention are specifically illustrated below through two simulation examples, respectively taking the voltage dynamics of a DC distribution network in an ideal communication scenario and a DC distribution network in a scenario with communication delay as examples.

[0121] like Figure 2The figure shows the topological structure of the four-terminal DC distribution network built in this simulation case. In the figure, the DC bus voltage level is 600V, and the AC source is connected to the DC distribution network through VSC1-VSC4 to supply power to the grid. VSC1-VSC4 and its components are voltage source power modules 1-4, among which the reference power of voltage source power module 1 is 100kW and the droop coefficient is 3.4; the rated power of voltage source power module 2-4 is 50kW and the droop coefficient is 6.8. Load power module 1-2 uses Buck1 and Buck2 circuits in series to connect the load equivalent (load 1 and load 2 in the figure are load power module 1 and load power module 2), and adopts constant voltage control, with a reference voltage of 400V.

[0122] Figure 2 In the figure, u1-u4 represents the input voltage of VSC1-VSC4, i e1 -i e4 represents the output current of VSC1-VSC4, R e1 -R e4 Represents the equivalent resistance of VSC1-VSC4, L e1 -L e4 represents the filter inductance of VSC1-VSC4, i1 and i2 represent the input current of Buck1 and Buck2.

[0123] Verification Example 1:

[0124] To verify the effectiveness of the present invention in a scenario without delay, the initial load power of load-type power module 1 and load-type power module 2 is set to 32kW. At 2.0s, the load power of load-type power module 1 suddenly changes to 112kW, causing the DC bus voltage to oscillate. At this time, the total load power of the DC power distribution system is 144kW. At this time, the specific oscillation of the DC bus voltage is as follows: Figure 3 shown.

[0125] Depend on Figure 4 and Figure 5 It can be seen that before 2.0s, the DC power distribution system did not start collaborative control, and the voltage source power module automatically distributed power according to the load of the load module in the system. At this time, the port voltage was less than the DC voltage reference value of 600V. After 2.0s, the load power of the load power module 1 increased suddenly, causing the DC bus to oscillate. At this time, the control method proposed in the present invention is applied. The local distributed model predictive control is used for rapid response, and the inertia adjustment coefficient is optimized in real time to provide inertia support for the system and suppress voltage oscillation. The consistency control uses a voltage controller and a power divider to collaboratively control the output voltage and power of each voltage source power module, maintain the average voltage of each port at 600V, and distribute the output power in a ratio of 2:1:1:1.

[0126] The output voltage dynamic characteristics of the load-type power module under the control method proposed in the present invention (the method proposed in the present patent in each figure) and the constant DC voltage dual-loop control are as follows: Figure 6 and Figure 7 As shown. Figure 6 and Figure 7 It can be seen that compared with the traditional dual-loop control, the adaptive model predictive control designed by the present invention in combination with the disturbance source positioning index has better transient response and can achieve rapid tracking of the output current and duty cycle signals, especially for the power module where the disturbance source is located, both the adjustment time and the overshoot are smaller than the traditional PI control.

[0127] Verification Example 2:

[0128] In order to verify the effectiveness of the control method proposed by the present invention under the condition of time delay, under the conditions of verification example 1, the input delay between the voltage source type power modules is set to 0.1s, and when the DC voltage oscillates, the control method proposed by the present invention and the existing consistency control method (i.e., Figure 8 , Fig. 9 In the existing control method in the literature), since the communication delay only affects the voltage estimate of the voltage observer and has no effect on the final convergence value of the power divider, the output power distribution of the existing consistency control is no longer concerned. At this time, the output voltage dynamics of the voltage source power supply module under different controls are as follows: Figure 8 and Fig. 9 shown.

[0129] according to Figure 8 and Fig. 9 It can be seen that in the scenario where communication delay exists, the control method proposed in the present invention and the existing consistency control can converge, but the traditional voltage observer will have observation deviation under the influence of delay, resulting in a deviation between the voltage estimate and the actual value of the system. The method proposed in the present invention improves the voltage observer to ensure that the estimated state output by the observer will not be affected by the instantaneous change of the communication delay, thereby ensuring that the estimated value eventually converges to the true value of the system. Therefore, the control proposed in the present invention can reach the system reference value of 600V, and the traditional consistency control can reach 597V. In addition, the present invention can achieve voltage stabilization more quickly, which helps to improve the convergence speed of consistency control. Therefore, by comparing Figure 4 It can be seen that in the scenario where time delay exists, although the convergence speed of the control method proposed in the present invention decreases, it is still faster than the existing consistency control.

Claims

1. A coordinated control method for DC power distribution system based on distributed model predictive control, characterized in that The following steps are involved: S1. In the DC power distribution system, the power module at the power supply end is equivalent to a voltage source power module, and the distributed power supply unit and the DC load are equivalent to a load power module; S2, inertia adjustment coefficient As the input control variable, the state space equation of the i-th voltage source type power module is established; S3, filter current and output voltage As the state variable, establish the state space equation of the kth load-type power module; S4, based on the output voltage deviation of the voltage source power module and The minimum value of the incremental weighted square sum is the optimization goal, the objective function is established, and its constraints are set; S5. Based on the disturbance source positioning index of the voltage source power module ,as well as The oscillation situation can be adjusted adaptively ; S6. Taking the minimum value of the weighted square sum of the current signal of the load-type power module and the output duty cycle as the target, establish the objective function, and locate the disturbance source index of the load-type power module according to the load-type power module And the output voltage deviation of the load-type power module, adaptively handle the transient response of voltage control; S7, The measurable output value of the Luenberger Observer is designed to accurately estimate the The instantaneous state value of S8. Design a consistent voltage-power controller to achieve coordinated control; S9, improve the consistent voltage-power controller to achieve the ultimate coordinated control; In the S2, As the input control variable, the state space equation of the i-th voltage source power module is established as: ； In the formula, , , , are the droop coefficient, voltage measured value, voltage reference value, and power measured value of the i-th voltage source power module respectively; and are the measured values ​​of the d-axis current and q-axis current of the i-th voltage source type power module respectively; , is the control parameter of the voltage outer loop of the i-th voltage source type power module; , are the proportional coefficient and integral coefficient of the d-axis current inner loop of the i-th voltage source power module respectively; , are the proportional coefficient and integral coefficient of the q-axis current inner loop of the i-th voltage source power module respectively; , are the AC side filter inductance and equivalent resistance of the i-th voltage source power module respectively; , is the switching function of the dq axis current; is an intermediate variable; , , are the intermediate variables of the proportional-integral link of the i-th voltage source power module; is the output current of the DC side of the i-th voltage source power module; is the capacitance on the DC side of the i-th voltage source power module; T is the time constant of the high-pass filter link; t is time, d is the differential sign; In the S3, and The state space equation for the kth load-type power module is established as: ； In the formula, , Divided into the duty cycle and the steady-state value of the duty cycle of the kth load-type power module; , are the DC bus voltage and its steady-state value respectively; is the filter inductance at the output side of the kth load-type power module; is the filter capacitor on the output side of the kth load-type power module; is the output side load of the kth load-type power module; In the above S4, the objective function is: ； Where J is the objective function, which represents the output voltage deviation and The incremental weighted sum of squares of ; , They are the output voltage matrix and reference voltage matrix of the voltage source power module at time h respectively; is the value of the i-th voltage source power module The incremental weight coefficient of ; is the inertia adjustment coefficient matrix of the voltage source power module at time h; p is the prediction time domain, M is the control time domain, and M≤p is satisfied; represents the increment of discrete variables at adjacent moments; f is the prediction moment; The constraints are: ； In the formula, is the maximum active power of the i-th voltage source power module; , They are the minimum control increment and the maximum control increment that the voltage source type power module can withstand respectively; is the actual control increment of the voltage source type power module; The S5 adaptively adjusts The way is, for : when hour, The increment is greater than the maximum control increment that the DC power distribution system can withstand. Keep it at the minimum value, limiting the control increment while ensuring the maximum control effect; when hour, The increment is within the maximum range that the DC power distribution system can bear. Adaptive adjustment according to the status of DC power distribution system; thus, It is expressed as: ； In the formula, for The minimum value of , are the voltage reference value and the voltage measured value of the i-th voltage source type power module at time h respectively; It is the actual control increment of the voltage source power module at time h-1.

2. The method for coordinated control of a DC power distribution system based on distributed model predictive control according to claim 1, characterized in that: In the above S1, according to the characteristics of the power module at the power supply end in the DC power distribution system, the power module at the power supply end is equivalent to a voltage source type power module; according to the negative impedance characteristics of the distributed power supply unit and the DC load in the DC power distribution system, the distributed power supply unit and the DC load are equivalent to a load type power module.

3. The method for coordinated control of a DC power distribution system based on distributed model predictive control according to claim 1, characterized in that: In the above S6, the objective function established is: ； In the formula, is the weighted square sum of the current signal and output duty cycle of the kth load-type power module; , are respectively the current signal of the kth load-type power module at time h and the current signal reference value; is the duty cycle increment weight coefficient of the kth load-type power module; is the duty cycle of the kth load-type power module at time h; pass Adaptively handles transient response of voltage control, It is expressed as: ； In the formula, , are the output voltage and voltage reference value of the kth load-type power module at time h respectively; The initial value of the weight coefficient of the kth load-type power module control incremental target item.

4. The method for coordinated control of a DC power distribution system based on distributed model predictive control according to claim 3 is characterized in that: In S7, the Luenberger Observer is expressed as: ； 、 、 ； ； In the formula, , are the estimated values ​​of the state variables and output variables of the kth load-type power module; is the deviation between the state variable of the kth load-type power module and the estimated value of the state variable; , are the state variables and output variables of the kth load-type power module; The output duty cycle of the kth load-type power module; , , are the coefficient of the estimated value of the state variable of the kth load-type power module, the coefficient of the output duty cycle, and the coefficient of the estimated value of the output variable; yes The differential form of .

5. The method for coordinated control of a DC power distribution system based on distributed model predictive control according to claim 4 is characterized in that: In the above-mentioned S8, the designed consistent voltage-power controller is expressed as: ； in: ； In the formula, , are the voltage observation values ​​of the i-th voltage source type power module and the j-th voltage source type power module respectively; is the neighbor node set of the i-th voltage source power module; is the power allocation deviation of the i-th voltage source power module; is the output voltage of the i-th voltage source power module; , They are the gain of voltage consistency control and the gain of management consistency control; , are the output power deviations of the i-th voltage source type power module and the j-th voltage source type power module respectively; is the output power of the i-th voltage source power module; represents the communication weight between the i-th voltage source type power module and the j-th voltage source type power module; is the integration variable.

6. The method for coordinated control of a DC power distribution system based on distributed model predictive control according to claim 5, characterized in that: In the above-mentioned S9, the improved consistent voltage-power controller is expressed as: ； In the formula, is the input reference command adjustment value of the voltage outer loop of the i-th voltage source type power module; yes The differential form of , are the voltage consistency coefficient and power consistency coefficient of the i-th voltage source type power module respectively; is the deviation coefficient of the i-th voltage source power module; , are the intermediate variables introduced by the i-th voltage source type power module and the j-th voltage source type power module respectively; yes The differential form of ; N is the number of voltage source power modules.

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