Device and method for improving power quality of new energy micro-grid with light storage coordinated feed-in

Abstract

The invention provides a light storage coordinated feed-in new energy microgrid power quality improving device and method, and relates to the technical field of microgrid distributed control. The light storage coordinated feed-in new energy microgrid power quality improving device comprises a series converter, a parallel converter, a battery energy management system and a direct current power supply unit. According to the optical storage coordinated feed-in new energy microgrid power quality improvement method, a prediction equation is established for a series converter to decouple a control target, and power grid current can be accurately compensated. An adaptive compensation control technique based on a VLLMS algorithm is employed for the parallel converter to generate a control signal for the parallel converter. A virtual inertia control strategy is provided for a battery energy management system, and inertia support is provided for a series converter and a parallel converter. And aiming at a non-ideal voltage condition, constructing a PB-SM compensation strategy of the new energy micro-grid power quality improving device based on optical storage coordinated feed-in.

Description

Technical Field

[0001] The present invention relates to the technical field of microgrid distributed control, and particularly to a device and method for improving the power quality of a new energy microgrid with coordinated optical storage feeding. Background Art

[0002] With the rapid development of modern industry, the number of high-end industrial users such as semiconductors and automobile manufacturing is increasing day by day. The access of a large number of precision equipment and sensitive loads has made these modern industrial equipment have higher and higher requirements for power quality. Voltage sags and voltage interruptions are inevitable power quality disturbance events in the power system, which will have a significant impact on high-end industrial users. In addition, the progress of semiconductor technology has led to an increasing penetration rate of power electronics-based equipment in the form of power electronic converters and nonlinear loads into the distribution system. The non-sinusoidal current drawn by the nonlinear load from the power grid flows through the power supply system, which will deteriorate the power quality in the distribution network and cause non-sinusoidal voltage drops, thereby causing interference to the load terminal voltage. The harmonic current and reactive power generated by nonlinear loads such as power electronic devices will cause damage to various equipment and users in the power grid.

[0003] The main objectives of the low-voltage distribution system are to improve the end-user experience, enhance power quality and power supply security, economically distribute power, and have flexibility. Compared with traditional power distribution, the microgrid system has the advantages of higher efficiency, lower losses, personnel protection, cable maximum power transmission capacity, and easy integration with renewable energy reserves. In a DC microgrid, the number of conversion stages can be reduced by selecting an appropriate voltage level. In addition, the energy storage system (EES) can be coupled to the primary DC grid or connected through a DC-DC converter. The structure of the DC microgrid consists of distributed power sources, loads, and converters connected in parallel to the DC bus. The impedance of the cable and the converter characteristics will cause voltage variations between the converter and the load, which in turn will generate circulating currents in the microgrid network. Therefore, a current sharing strategy needs to be adopted to maintain the bus voltage and avoid circulating currents. However, when a large load is connected to or removed from the microgrid, or even when the utility grid is disconnected, a voltage drop may occur, which may lead to electronic device failures and become the cause of micro-distribution network failures. The distribution system has grid disturbances such as transients, voltage sags, voltage swells, harmonics, and momentary interruptions, which are related to power quality problems. Therefore, stability and power quality improvement are important components of network reliability. In addition, the development of DC networks depends on power electronic devices, and correct control commands are crucial for determining the expected operation of any power electronics-based system. However, the protection scheme for DC systems with bidirectional power flow is still a bottleneck in the implementation of DC microgrids. The protection of any network depends on the type of DC fault, network grounding, and DC circuit breaker technology. Therefore, fault current analysis is crucial for designing protection systems as well as maintenance and post-fault recovery.

[0004] To solve the power quality problems of current and voltage, installing power quality control equipment is a common technology. Power quality management equipment generally refers to customized power equipment based on power electronics technology, mainly including static synchronous compensator (STATCOM), active power filter (APF), dynamic voltage restorer (DVR) and unified power quality conditioner (UPQC). Among them, UPQC combines the functions of shunt active power filter and series dynamic voltage restorer, can realize the comprehensive management of current and voltage power quality, and has broad application prospects. Some experts and scholars have proposed distributed integrated power generation and power quality management, combined with the functions of UPQC, adding an energy storage system to UPQC to realize the function of uninterruptible power supply.

[0005] In the conventional control strategy, the series converter generally only works when the grid voltage drops suddenly and is usually in an idle state, while the shunt converter needs to perform reactive power compensation and eliminate current harmonics and is often in a heavy load state. Some scholars have explored in the field of microgrid control and proposed a UPQC power control strategy based on power angle control, which can make the series converter emit a certain amount of reactive power, but only realizes the amplitude compensation of the load, and the phase of the load may change suddenly. In addition, AC coil contactors and adjustable speed drive devices are also very sensitive to phase jumps. For the UPQC voltage compensation strategy of reactive power control, the compensation voltage of the series converter and the source current are perpendicular to each other, eliminating the active circulating current, but there is still a sudden change in the phase after compensation. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a new energy microgrid power quality improvement device and method with coordinated optical storage feeding, so as to improve the power quality of the new energy microgrid.

[0007] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0008] On the one hand, the present invention provides a new energy microgrid power quality improvement device with coordinated optical storage feeding, including a series converter, a shunt converter, a battery energy management system and a DC power supply unit;

[0009] The series converter and the parallel converter are connected to a common DC bus in a back-to-back form; the series converter is a controlled current source and is connected in series with the three-phase transformer of the power grid through a first resistor, the interface inductor of the series converter, and the capacitor of the series converter; the parallel converter is a controlled voltage source and is connected in parallel with the three-phase load through a second resistor, the interface inductor of the parallel converter, and the capacitor of the parallel converter; the DC power supply unit includes a photovoltaic array and a reverse-blocking diode, and the photovoltaic array is connected in series with the reverse-blocking diode to the battery energy management system; the battery energy management system is of a three-level bidirectional DC / DC converter structure and is connected to both ends of the series converter;

[0010] On the other hand, the present invention provides a method for improving the power quality of a new energy microgrid with coordinated optical storage feeding, including the following steps:

[0011] Step 1: Establish the mathematical models of the series converter and the parallel converter in the stationary coordinate system respectively;

[0012] The mathematical model of the series converter in the stationary coordinate system is shown by the following formula:

[0013]

[0014] Where, L se is the interface inductor of the series converter, i f is the current flowing through the interface inductor L se of the series converter, C se is the capacitor of the series converter, u f is the voltage of the capacitor C se of the series converter, R is the resistor, i s is the grid current, u' is the output voltage of the series converter, and t is the time;

[0015] The mathematical model of the parallel converter in the stationary coordinate system is shown by the following formula:

[0016]

[0017] Where, L sh is the interface inductor of the parallel converter, i o is the current flowing through the interface inductor L sh of the parallel converter, u is the output voltage of the parallel converter, u c is the voltage of the capacitor C sh of the parallel converter, i c is the compensation current of the parallel converter;

[0018] Set the switching function S x of any arm of the series converter and the switching function S x ' of any arm of the parallel converter as:

[0019]

[0020] Among them, a, b, and c are respectively the three bridge arms of the series converter or the parallel converter;

[0021] The output voltage u' of the series converter and the output voltage u of the parallel converter are respectively:

[0022]

[0023] Among them, the rotation factor α = e j(2π / 3) , u dc is the DC bus voltage;

[0024] Step 2: Construct a control strategy based on control objective decoupling, and use the control strategy based on control objective decoupling to achieve the control of the series converter;

[0025] Step 2.1: Set the control objective, establish the control equation of the discrete series converter, and construct the value function;

[0026] Set the current of the interface inductor of the series converter and the voltage of the capacitor of the series converter as the control objective;

[0027] Establish the control equation of the series converter, as shown in the following formula:

[0028]

[0029] Discretize the control equation of the series converter to obtain the discretized control equation of the series converter, as shown in the following formula:

[0030]

[0031] Among them, i fx (k + 1) is the current flowing through the inductor L se on any bridge arm x at the (k + 1)-th moment, u fx (k + 1) is the voltage of the capacitor C se on any bridge arm x at the (k + 1)-th moment, i sx (k) is the grid current on any bridge arm x at the k-th moment, u x '(k) is the output voltage of the series converter on any bridge arm x at the k-th moment, i fx (k) is the current flowing through the inductor L se on any bridge arm x at the k-th moment, u fx (k) is the voltage of the capacitor C se on any bridge arm x at the k-th moment, k is the current moment, and T s is the sampling period;

[0032] Construct the value function g x , as shown in the following formula:

[0033]

[0034] Among them, is the reference value of the grid current at the (k + 1)th moment;

[0035] Step 2.2: Construct a delay compensation control equation to perform delay compensation on the discrete series converter control equation to obtain the predicted value function;

[0036] The delay compensation control equation is constructed as shown in the following formula:

[0037]

[0038] After delay compensation, the predicted value function g at the (k + 2)th moment x ′ is:

[0039]

[0040] Among them, is the reference current flowing through the inductor L on any bridge arm x se ;

[0041] Step 2.3: Based on the delay compensation control equation, establish a prediction equation with the grid current as the only control variable to decouple the control objective;

[0042] The prediction equation is as shown in the following formula:

[0043]

[0044] Step 2.4: Calculate the reference value of the output voltage of the series controller, and convert the grid current reference quantity into the reference quantity of the output voltage of the series converter through SVPWM modulation to realize the control of the series converter;

[0045] Take the partial derivative of the value function g x and set the value of the partial derivative function of the value function to 0, as shown in the following formula:

[0046]

[0047] Calculate the current i flowing through the inductor L on any bridge arm x of the series converter at the (k + 2)th moment se , and obtain the reference value u of the output voltage of the series converter at the kth moment based on the prediction equation fx ′(k): x ′(k):

[0048]

[0049] Among them, the reference value of the grid current at the (k + 2)th moment As shown in the following formula:

[0050]

[0051] The reference value u x ′(k) of the output voltage of the series converter at time k is obtained as follows:

[0052]

[0053] Step 3: Construct an adaptive compensation control strategy based on the VLLMS algorithm as the control strategy of the shunt converter, extract the active and reactive components of the load current respectively, and generate the control signal of the shunt converter;

[0054] Step 3.1: Calculate the phase voltage amplitude according to the instantaneous voltages of phases a, b, and c of the power grid, and calculate the in-phase and quadrature components of phases a, b, and c of the power grid respectively;

[0055] According to the instantaneous voltages u sa , u sb , u sc of phases a, b, and c of the power grid, calculate the phase voltage amplitude V sp , as shown in the following formula:

[0056]

[0057] Calculate the in-phase components j pa , j pb , j pc and the quadrature components j qa , j qb , j qc of phases a, b, and c of the power grid respectively, as shown in the following formula:

[0058]

[0059]

[0060] Step 3.2: Based on the VLLMS algorithm, take the in-phase components j pa , j pb , j pc of phases a, b, and c of the power grid as the input of the VLLMS algorithm, take the load current i la , i lb , i lc as the expected output of the VLLMS algorithm, and extract the active component of the load current; take the quadrature components j qa , j qb , j qc of phases a, b, and c of the power grid as the input of the VLLMS algorithm, take the load current as the expected output of the VLLMS algorithm, and extract the reactive component of the load current;

[0061] The in-phase components j of the a, b, and c phases of the power grid pa , j pb , j pc are used as the input x(κ) of the VLLMS algorithm, and the load current i la , i lb , i lc is used as the expected output d(κ) of the VLLMS algorithm. The magnitudes w pa , w pb , w pc of the active components of the load currents of the a, b, and c phases of the power grid are iteratively calculated. The magnitude w pa of the active component of the load current of the a phase of the power grid at time κ + 1 is as follows:

[0062]

[0063] where w pa (κ) is the magnitude of the active component of the load current of the a phase of the power grid at time κ, e pa (κ) is the error of the load current of the a phase of the power grid at time κ, μ pa (κ) is the variable step size of the load current of the a phase of the power grid at time κ, γ pa (κ) is the change omission factor of the load current of the a phase of the power grid at time κ, j pa (κ) is the in-phase component of the a phase of the power grid at time κ, i la (κ) is the load current of the a phase of the power grid at time κ;

[0064] The magnitudes w pb (κ + 1), w pc (κ + 1) of the active components of the load currents of the b and c phases of the power grid at time κ + 1 are as follows:

[0065]

[0066] where w pb (κ) is the magnitude of the active component of the load current of the b phase of the power grid at time κ, w pc (κ) is the magnitude of the active component of the load current of the c phase of the power grid at time κ, e pb (κ) is the error of the load current of the b phase of the power grid at time κ, e pc (κ) is the error of the load current of the c phase of the power grid at time κ, μ pb (κ) is the variable step size of the load current of the b phase of the power grid at time κ, μ pc (κ) is the variable step size of the load current of the c phase of the power grid at time κ, γ pb (κ) is the change omission factor of the load current of the b phase of the power grid at time κ, γ pc(κ) is the change omission factor of the load current of phase c of the power grid at time κ, j pb (κ) is the in-phase component of phase b of the power grid at time κ, j pc (κ) is the in-phase component of phase c of the power grid at time κ;

[0067] The quadrature components of phases a, b, and c of the power grid j qa ,j qb ,j qc are used as the input x(κ) of the VLLMS algorithm, and the load currents i la ,i lb ,i lc are used as the desired output d(κ) of the VLLMS algorithm. The magnitudes w qa ,w qb ,w qc of the reactive components of the load currents of phases a, b, and c of the power grid at time κ + 1 are iteratively calculated. The magnitude w pa (κ + 1) of the reactive component of the load current of phase a of the power grid at time κ + 1 is as shown in the following formula:

[0068]

[0069] where w qa (κ) is the magnitude of the reactive component of the load current of phase a of the power grid at time κ, e qa (κ) is the error of the load current of phase a of the power grid at time κ, μ qa (κ) is the variable step size of the load current of phase a of the power grid at time κ, γ qa (κ) is the change omission factor of the load current of phase a of the power grid at time κ, j qa (κ) is the quadrature component of phase a of the power grid at time κ, i la (κ) is the load current of phase a of the power grid at time κ;

[0070] The magnitudes w qb (κ + 1), w qc (κ + 1) of the reactive components of the load currents of phases b and c of the power grid at time κ + 1 are as shown in the following formula:

[0071]

[0072] where w qb (κ) is the magnitude of the reactive component of the load current of phase b of the power grid at time κ, w qc (κ) is the magnitude of the reactive component of the load current of phase c of the power grid at time κ, e qb (κ) is the error of the load current of phase b of the power grid at time κ, e qc (κ) is the error of the load current of phase c of the power grid at time κ, μ qb (κ) is the variable step size of the load current of phase b of the power grid at time κ, μ qc(κ) is the variable step of the grid c-phase load current at the κ-th moment, γ qb (κ) is the change omission factor of the grid b-phase load current at the κ-th moment, γ qc (κ) is the change omission factor of the grid negative c-phase load current at the κ-th moment, j pb (κ) is the quadrature component of the grid b-phase at the κ-th moment, j pc (κ) is the quadrature component of the grid c-phase at the κ-th moment;

[0073] Calculate the average value w of the active component of the load current respectively pavg and the average value w of the reactive component of the load current qavg , as shown in the following formula:

[0074]

[0075] Step 3.3: Calculate the control compensation at the κ + 1 moment, and synthesize the reference current according to the power supply power P of the DC power supply unit PV and the phase voltage amplitude V sp . Based on the average value w of the active component of the load current pavg , combine the control compensation at the κ + 1 moment and the reference current to calculate the total amplitude of the reference current;

[0076] Since there is a certain active power loss in the parallel converter switch, in order to maintain the DC link voltage, by comparing the DC link voltage V dc and the reference DC bus voltage V dcref calculate the control compensation amount w loss (κ + 1) at the κ + 1 moment, as shown in the following formula:

[0077] e dc (κ) = V dcref (κ) - V dc (κ) (24)

[0078] w loss (κ + 1) = w loss (κ) + k p {e dc (κ + 1) - e dc (κ)} + k i e dc (κ + 1) (25)

[0079] where, e dc (κ) is the error between the DC link voltage V dc and the reference DC bus voltage V dcref , e dc (κ + 1) is the error between the DC link voltage V dc and the reference DC bus voltage V dcrefError, w loss (κ) is the control compensation at time κ, k p is the correction coefficient, k i is the correction coefficient;

[0080] According to the power generation power P of the photovoltaic array PV and the total amplitude V of the output voltage of the photovoltaic array sp synthesize the reference current i sa , i sb , i sc total amplitude w PV :

[0081]

[0082] Based on the average value w of the active component of the load current pavg , combined with the control compensation at time κ + 1 w loss (κ + 1), calculate the reference current i sa , i sb , i sc total amplitude w PV active component w sp and the reference current i sa , i sb , i sc total amplitude w PV reactive component w sq , as shown in the following formula:

[0083] w sp = w pavg + w loss - w PV (27)

[0084] w sq = - w qavg (28)

[0085] Step 3.4: Synthesize the reference source current as the control signal of the parallel converter;

[0086] According to the total amplitude w of the reference current i sa , i sb , i sc total amplitude w PV active component w sp 、reference current i sa , i sb , i sc total amplitude w PV reactive component w sq 、in-phase component j of each phase pa , j pb , j pc and the quadrature component j of each phase qa,j qb ,j qc Synthesize the reference source current As the control signal of the parallel converter, as shown in the following formula:

[0087]

[0088] Wherein, is the active component of the reference current i sa , is the reactive component of the reference current i sa , is the active component of the reference current i sb , is the reactive component of the reference current i sb , is the active component of the reference current i sc , is the reactive component of the reference current i sc ;

[0089] Step 4: Construct a virtual inertia control strategy as the control strategy of the battery energy management system;

[0090] Construct a virtual inertia control strategy, as shown in the following formula:

[0091] P c = sign(ΔU)ΔU 2 C c (31)

[0092] Wherein, P c is the output power of the virtual inertia control, the DC voltage change ΔU = U Hset - U H , U Hset is the DC rated voltage, U H is the DC voltage, C c is the virtual inertia control coefficient, sign(·) is the sign function;

[0093] In the virtual inertia control strategy, the output power P c of the virtual inertia control is proportional to the square of the DC voltage change ΔU, which is used to ensure rapid release or absorption of energy in case of voltage fluctuations, providing inertial support for the series converter and the parallel converter; the sign function sign(△U) is used to judge whether the voltage is in the sudden rise or sudden drop condition, sign(△U) = 1 is the voltage sudden drop condition, and the battery management system quickly releases energy; sign(△U) = -1 is the voltage sudden rise condition, and the battery management system quickly absorbs energy;

[0094] Step 5: For the non-ideal voltage situation, based on the PB control and SM control, construct the PB-SM compensation strategy of the new energy microgrid power quality improvement device with coordinated optical storage feeding;

[0095] Step 5.1: For the new energy microgrid power quality improvement device with coordinated optical storage feeding with passive characteristics, construct the EL model of PB control, and construct the positive and negative sequence PB control laws of the new energy microgrid power quality improvement device with coordinated optical storage feeding;

[0096] Establish a unified model of the series converter and the parallel converter in the two-phase stationary coordinate system, as shown in the following formula:

[0097]

[0098] where, u sd1 and u sq1 are respectively the voltage on the d-axis and the voltage on the q-axis of the DC side voltage of the new energy microgrid power quality improvement device with coordinated optical storage feeding converted into the two-phase stationary coordinate system, u sd and u sq are respectively the voltage on the d-axis and the voltage on the q-axis of the output voltage of the new energy microgrid power quality improvement device with coordinated optical storage feeding in the two-phase stationary coordinate system, L is the inductor of the new energy microgrid power quality improvement device with coordinated optical storage feeding, i d and i q are respectively the grid current on the d-axis and the grid current on the q-axis in the two-phase stationary coordinate system;

[0099] Based on the unified model of the series converter and the parallel converter in the two-phase stationary coordinate system, construct the PB control EL model of the new energy microgrid power quality improvement device with coordinated optical storage feeding, as shown in the following formula:

[0100]

[0101] where, is the state vector, is the input vector, is the energy storage matrix, is the dissipation matrix, is the interconnection matrix;

[0102] In the two-phase stationary coordinate system, the positive sequence current balance point x +* and the negative sequence current balance point x -* of the new energy microgrid power quality improvement device with coordinated optical storage feeding are respectively:

[0103]

[0104] where, is the positive sequence current reference value of the grid current on the d-axis in the two-phase stationary coordinate system, is the positive-sequence current reference value of the grid current on the q-axis in the two-phase stationary coordinate system, is the negative-sequence current reference value of the grid current on the d-axis in the two-phase stationary coordinate system, is the negative-sequence current reference value of the grid current on the q-axis in the two-phase stationary coordinate system;

[0105] State variable error and are:

[0106]

[0107] where x + is the positive-sequence component of the state vector x, and x - is the negative-sequence component of the state vector x;

[0108] The state variable errors and are introduced into the PB control EL model of the new energy microgrid power quality improvement device with coordinated photovoltaic and energy storage feeding, as shown in the following formula:

[0109]

[0110] Inject damping R g into the resistance R of the system of the new energy microgrid power quality improvement device with coordinated photovoltaic and energy storage feeding to obtain the interconnected matrix R t ′ after injecting damping, as shown in the following formula:

[0111]

[0112] where and are the positive-sequence damping amount and negative-sequence damping amount of the interconnected matrix R t ′ after injecting damping respectively, and are the positive-sequence damping amount and negative-sequence damping amount of the damping amount R g respectively, is the positive-sequence damping component on the d-axis in the two-phase stationary coordinate system, is the positive-sequence damping component on the q-axis in the two-phase stationary coordinate system, is the negative-sequence damping component on the d-axis in the two-phase stationary coordinate system, is the negative-sequence damping component on the q-axis in the two-phase stationary coordinate system;

[0113] The positive and negative sequence PB control laws of the new energy microgrid power quality improvement device with coordinated photovoltaic and energy storage feeding are obtained, as shown in the following formula:

[0114]

[0115] Among them, is the positive-sequence output voltage of the d-axis in the two-phase stationary coordinate system, is the positive-sequence output voltage of the q-axis in the two-phase stationary coordinate system, is the negative-sequence output voltage of the d-axis in the two-phase stationary coordinate system, is the negative-sequence output voltage of the q-axis in the two-phase stationary coordinate system, is the positive-sequence line voltage of the d-axis in the two-phase stationary coordinate system, is the positive-sequence line voltage of the q-axis in the two-phase stationary coordinate system, is the negative-sequence line voltage of the d-axis in the two-phase stationary coordinate system, is the negative-sequence line voltage of the q-axis in the two-phase stationary coordinate system, is the positive-sequence current of the grid current of the d-axis in the two-phase stationary coordinate system, is the positive-sequence current of the grid current of the q-axis in the two-phase stationary coordinate system, is the negative-sequence current of the grid current of the d-axis in the two-phase stationary coordinate system, is the negative-sequence current of the grid current of the q-axis in the two-phase stationary coordinate system;

[0116] Step 5.2: Introduce the SM control on the basis of the PB control of the EL model to obtain the control law of the PB-SM control compensation strategy of the new energy microgrid power quality improvement device with coordinated optical storage feeding under non-ideal grid voltage conditions;

[0117] Select the sliding mode surfaces s 1 and s 2 of the new energy microgrid power quality improvement device with coordinated optical storage feeding as:

[0118]

[0119] Based on the unified model of the series converter and the parallel converter in the two-phase stationary coordinate system, the positive and negative sequence models of the grid current are obtained as shown in the following formula:

[0120]

[0121] Use the sign functions sgn(s 1 ) and sgn(s 2 ) to reduce chattering, and select the reaching law of the SM control as:

[0122]

[0123] Among them, ρ + is the positive-sequence adjustment parameter of the SM control, and ρ - is the negative-sequence adjustment parameter of the SM control, is the positive-sequence regulation parameter of d-axis SM control in the two-phase stationary coordinate system, is the positive-sequence regulation parameter of q-axis SM control in the two-phase stationary coordinate system, is the negative-sequence regulation parameter of d-axis SM control in the two-phase stationary coordinate system, is the negative-sequence regulation parameter of q-axis SM control in the two-phase stationary coordinate system, u + is the positive-sequence component of the input vector u, u - is the negative-sequence component of the input vector u;

[0124] Replace the sign function sgn(·) with the saturation function sat(·), as shown in the following formula:

[0125]

[0126] Obtain the relationship between the grid current i d in the two-phase stationary coordinate system and the reference value i dref of the grid current in the two-phase stationary coordinate system, as shown in the following formula:

[0127]

[0128] Obtain the control law of the PB-SM control compensation strategy under non-ideal grid voltage conditions, as shown in the following formula:

[0129]

[0130] By selecting appropriate damping parameters and regulation parameters Adjust the control law of the PB-SM control compensation strategy of the new energy microgrid power quality improvement device with coordinated optical storage feeding under non-ideal grid voltage conditions, so as to realize the control of the grid voltage by the new energy microgrid power quality improvement device with coordinated optical storage feeding under non-ideal voltage conditions.

[0131] The beneficial effects of adopting the above technical solutions are as follows: The present invention provides a method and device for improving the power quality of a new energy microgrid with coordinated optical storage feeding. It gives priority to the overall health of the system. For the series converter, a prediction equation with the inductor current as the only control variable is established to decouple the control objectives. By rewriting and simplifying the prediction equation, the decoupling of the inductor current and capacitor voltage of the series converter is achieved, and the acquisition of the optimal modulation amount is realized, enabling accurate compensation of the grid current. For the parallel converter, an adaptive compensation control technology based on the VLLMS algorithm is adopted. The VLLMS algorithm extracts basic information from the source voltage and load current to generate control signals for the parallel converter. It can accurately and quickly track the fundamental components of highly distorted current and voltage signals without a low-pass filter and converges to the required conditions faster by using an iterative method, keeping the weights of the updated parameters within the specified limits. Since the photovoltaic array of the DC power supply unit participates in the compensation technology of the parallel converter, problems related to current-related electrical energy and reactive power compensation are alleviated. By using the in-phase component and quadrature component of the voltage unit to generate the reference current signal, the performance of the parallel converter under highly polluted grid voltages is enhanced, and it is no longer affected by voltage sags / swells and harmonics existing in the grid voltage. A virtual inertia control strategy is proposed. The inertia support ability of this strategy is proportional to the square of the voltage fluctuation amplitude and is not affected by the voltage change rate. At the same time, the greater the voltage fluctuation, the greater the inertia support ability provided, solving the problem that the traditional virtual inertia control strategy cannot provide inertia support for the system when the voltage change rate is negative or zero. In addition, considering the non-ideal grid voltage, it is difficult to guarantee the power quality at the load end. A strategy combining PB control and SM control is proposed for power quality compensation of the device for improving the power quality of a new energy microgrid with coordinated optical storage feeding. For the device for improving the power quality of a new energy microgrid with coordinated optical storage feeding with passive characteristics, an EL model of PB control is constructed, and the control law of the PB-SM control compensation strategy under non-ideal grid voltage conditions is obtained. The PB-SM compensation strategy has the characteristics of fast response speed and global steady state of PB control, and also has the advantages of strong anti-interference ability and robustness of SM control. Description of the Drawings

[0132] Figure 1 It is the topological structure diagram of the device for improving the power quality of a three-phase three-wire new energy microgrid with coordinated optical storage feeding provided by the embodiment of the present invention;

[0133] Figure 2 It is the schematic diagram of the control strategy based on the decoupling of control objectives provided by the embodiment of the present invention;

[0134] Figure 3 It is the flow chart of the VLLMS algorithm provided by the embodiment of the present invention;

[0135] Figure 4Schematic diagram of the adaptive compensation control strategy based on the VLLMS algorithm provided by the embodiments of the present invention;

[0136] Figure 5 Topological structure diagram of the battery energy management system provided by the embodiments of the present invention. Detailed implementation manners

[0137] The following further describes in detail the specific implementation manners of the present invention with reference to the drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0138] A new energy microgrid power quality improvement device with coordinated optical storage feeding in this embodiment, as Figure 1 shown, includes a series converter, a parallel converter, a battery energy management system, and a DC power supply unit;

[0139] The series converter and the parallel converter are connected to the common DC bus in a back-to-back form; the series converter is a controlled current source and is connected in series with the three-phase transformer of the power grid through a first resistor, a series converter interface inductor, and a series converter capacitor; the parallel converter is a controlled voltage source and is connected in parallel with the three-phase load through a second resistor, a parallel converter interface inductor, and a parallel converter capacitor; the DC power supply unit includes a photovoltaic array and a reverse blocking diode, and the photovoltaic array is connected in series with the reverse blocking diode to the battery energy management system; the battery energy management system is a three-level bidirectional DC / DC converter structure and is connected to both ends of the series converter;

[0140] The series converter suppresses grid current harmonics and improves the grid power factor by injecting compensation current into the grid. The interface inductor of the parallel converter limits the high-frequency current components that cannot be controlled by the parallel converter due to dynamic conditions such as sudden changes in load current. The battery energy storage system is a three-level bidirectional DC / DC converter structure and has a series of advantages such as small output current and voltage ripple, low switching frequency, and small required filter inductance and voltage stress of the switching devices.

[0141] A new energy microgrid power quality improvement method in this embodiment includes the following steps:

[0142] Step 1: Establish the mathematical models of the series converter and the parallel converter in the stationary coordinate system respectively;

[0143] The mathematical model of the series converter in the stationary coordinate system is shown by the following formula:

[0144]

[0145] Wherein, L se is the series converter interface inductor, and i f is the current flowing through the series converter interface inductor L seThe current, C se is the capacitor of the series converter, u f is the capacitor C of the series converter se The voltage, R is the resistance, i s is the grid current, u′ is the output voltage of the series converter, t is the time;

[0146] The mathematical model of the parallel converter in the stationary coordinate system is shown by the following formula:

[0147]

[0148] Among them, L sh is the interface inductor of the parallel converter, i o is the current flowing through the interface inductor L of the parallel converter sh The voltage of, u is the output voltage of the parallel converter, u c is the capacitor C of the parallel converter sh The voltage of, i c is the compensation current of the parallel converter;

[0149] According to the topological structure of the new energy microgrid power quality improvement device with coordinated optical storage feeding, it can be known that u f = u T u c = u l Among them, u f is the voltage of the capacitor C se u T is the voltage of the transformer T, u c is the voltage of the capacitor C sh Since the filtering capacitor C se is very small and can be ignored, therefore, the current i se flowing through the inductor L f and the secondary side current i d of the transformer T have the relationship of i f = i d Also, since the secondary side current i d of the transformer T and the grid current i s have the relationship of i d = i s Therefore, the current i se flowing through the inductor L f and the grid current i s have the relationship of i f ≈ i s ;

[0150] The current i sh flowing through the interface inductor L of the parallel converter o , the grid current i s , the compensation current i c, the current i flowing through the interface inductor L of the series converter se , the current i f , the output voltage u of the parallel converter, the output voltage u' of the series converter, the capacitor C of the series converter se , the voltage u f , the capacitor C of the parallel converter sh , the voltage u c are converted into electrical quantities in the complex plane and can be expressed as: i o = i oα + ji oβ , i s = i sα + ji sβ , i c = i сα + ji сβ , i f = i fα + ji fβ , u = u α + ju β , u c = u cα + ju cβ , u' = u' α + ju' β , u f = u fα + ju fβ ;

[0151] For the grid current i in the series converter in the stationary coordinate system s , the current i flowing through the interface inductor L of the series converter se , the current i f , the capacitor C of the series converter se , the voltage u f and the current i flowing through the interface inductor L of the parallel converter in the parallel converter sh , the current i o , the compensation current i of the parallel converter c , the capacitor C of the parallel converter sh , the voltage u c are subjected to the inverse Clark transformation as shown in the following formula:

[0152]

[0153] Set the switching function S of any arm of the series converter x and the switching function S x ' of any arm of the parallel converter as:

[0154]

[0155] where a, b, and c are the three arms of the series converter or the parallel converter respectively;

[0156] The output voltage u′ of the series converter and the output voltage u of the parallel converter are respectively:

[0157]

[0158] Among them, the rotation factor α = e j(2π / 3) , u dc is the DC bus voltage;

[0159] Step 2: Construct a control strategy based on the decoupling of control objectives, and use the control strategy based on the decoupling of control objectives to achieve the control of the series converter;

[0160] Step 2.1: Set the control objective, establish the control equation of the discrete series converter, and construct the value function;

[0161] The traditional series controller uses the phase angle θ of the grid current and the transformation matrix M to obtain the instantaneous active current i p and the instantaneous reactive current i q , and uses a first-order low-pass filter to obtain the DC active component i pa and the DC reactive component i qa . The transformation matrix M is shown in the following formula:

[0162]

[0163] Use the transformation matrix M to perform Clark inverse transformation on the instantaneous active current i p and the instantaneous reactive current i q to obtain the grid current reference value; The DC bus voltage u dc is subtracted from and superimposed with the bus reference voltage u dc-ref and then superimposed on the fundamental active component i pa to maintain the stability of the bus voltage.

[0164] The mathematical model of the traditional series converter in the two-phase stationary coordinate system is shown in the following formula:

[0165]

[0166] Among them, u fd , u′ d , i sd , i fd are respectively the voltage of the capacitor C se of the d-axis of the series converter, the output voltage of the series converter, the grid current, and the current flowing through the interface inductor L se of the series converter. u fq , u q ′, i sq , i fqThey are the voltage of the q-axis series converter capacitor C se , the output voltage of the series converter, the grid current, and the current flowing through the interface inductor L se of the series converter;

[0167] The cross-coupling of the current of the traditional series converter interface inductor and the voltage of the series converter capacitor makes the control structure of the traditional series converter complex, the parameter tuning difficult, and it is difficult to obtain the best compensation effect.

[0168] In this embodiment, the current of the series converter interface inductor and the voltage of the series converter capacitor are set as the control objectives. The schematic diagram of the control strategy decoupled based on the control objectives is as shown in Figure 2 ;

[0169] The control equation of the series converter is established as shown in the following formula:

[0170]

[0171] The control equation of the series converter is discretized to obtain the discretized control equation of the series converter as shown in the following formula:

[0172]

[0173] where, i fx (k + 1) is the current flowing through the inductor L on any arm x at the (k + 1)-th moment, u se (k + 1) is the voltage of the capacitor C on any arm x at the (k + 1)-th moment, i fx (k) is the grid current on any arm x at the k-th moment, u se ′(k) is the output voltage of the series converter on any arm x at the k-th moment, i sx (k) is the current flowing through the inductor L on any arm x at the k-th moment, u x (k) is the voltage of the capacitor C on any arm x at the k-th moment, k is the current moment, and T fx (k) is the current flowing through the inductor L on any arm x at the k-th moment, u se (k) is the voltage of the capacitor C on any arm x at the k-th moment, k is the current moment, and T fx (k) is the voltage of the capacitor C on any arm x at the k-th moment, k is the current moment, and T se is the sampling period; s ;

[0174] The value function g x is constructed as shown in the following formula:

[0175]

[0176] where, is the reference value of the grid current at the (k + 1)-th moment;

[0177] Step 2.2: Construct the delay compensation control equation, perform delay compensation on the discrete control equation of the series converter, and obtain the predicted value function at time k+2;

[0178] Construct the delay compensation control equation as shown in the following formula:

[0179]

[0180] It can be seen from the delay compensation control equation that the two control objectives of the current of the interface inductor of the series converter and the voltage of the capacitor of the series converter are cross-coupled, and it is difficult to construct a prediction equation for compensating the grid current on the series side;

[0181] After delay compensation, the predicted value function g at time k+2 is obtained x ′ as:

[0182]

[0183] where is the reference current flowing through the inductor L on any leg x at time k+2 se ;

[0184] Step 2.3: Based on the delay compensation control equation, establish a prediction equation with the grid current as the only control variable to decouple the control objectives. The prediction equation is as shown in the following formula:

[0185]

[0186] Since the sampling period T s is much smaller than the voltage change period, the prediction equation can be further simplified as:

[0187]

[0188] Step 2.4: Calculate the reference value of the output voltage of the series controller, and convert the grid current reference quantity into the reference value of the output voltage of the series converter through SVPWM modulation to realize the control of the series converter;

[0189] To accurately track the grid current reference value and obtain the minimum value of the value function, take the partial derivative of the value function g x and set the partial derivative function value of the value function to 0, as shown in the following formula:

[0190]

[0191] Calculate the current i se flowing through the inductor L on any leg x of the series converter at time k+2 fx (k+2), and obtain the reference value u x ′(k) of the output voltage of the series converter at time k based on the prediction equation:

[0192]

[0193] Among them, the reference value of the grid current at the k+2 moment is as shown in the following formula:

[0194]

[0195] The reference value u′(k) of the output voltage of the series converter at the k moment is obtained x as:

[0196]

[0197] Since the value function g x is always greater than zero, and the value function g x is equal to 0 at the first-order partial derivative, there is an extreme value. The second-order partial derivative of g(x) is obtained as shown in the following formula:

[0198]

[0199] Since the second-order partial derivative function of the value function g(x) is always greater than zero, therefore, when the first-order partial derivative function of the value function g(x) is equal to zero, the corresponding value function is the minimum value. The proposed control strategy can achieve accurate tracking of the grid current reference value and effectively improve the compensation effect of the series converter on the grid current distortion.

[0200] According to the Lyapunov stability criterion, the stability of the series converter control is analyzed as follows:

[0201] Define the current i se flowing through the inductor L fx deviation e as:

[0202]

[0203] Construct the Lyapunov function V = e 2 / 2, then the first-order derivative function of the Lyapunov function is:

[0204]

[0205] According to the discretized control equation and the delay compensation control equation, the first-order derivative function of the Lyapunov function is further obtained as

[0206]

[0207] According to the Lyapunov stability condition, in this embodiment, the continuous set model predictive direct control strategy based on the control objective decoupling meets the stability requirements.

[0208] Step 3: Construct an adaptive compensation control strategy based on the VLLMS algorithm as the control strategy for the parallel converter, extract the active component and reactive component of the load current respectively, and generate the control signal of the parallel converter;

[0209] The VLLMS algorithm converges to the desired condition faster by an iterative method, keeps the weights of the updated parameters within the specified limits, can efficiently and smoothly manage the power balance among the power grid, load and photovoltaic, and ensures the regulation of the DC bus voltage. In this embodiment, the control of the parallel converter is implemented based on the VLLMS algorithm to generate the switching signal for the parallel converter under dynamic and steady-state conditions. The VLLMS algorithm is a soft computing technology based on neural networks. As Figure 3 shown, it can adaptively update the weight parameters to track the changes occurring in the system and achieve a more accurate and stable control effect, specifically including:

[0210] Select the input x(κ) and the desired output d(κ), and perform linear filtering on the input x(κ) to obtain the actual output y(κ):

[0211] y(κ + 1) = w T (κ)·x(κ) (24)

[0212] where κ is the discrete time instant and w(κ) is the weight;

[0213] Calculate the error e(κ) between the desired output d(κ) and the actual output y(κ), as shown in the following formula:

[0214] e(κ) = d(κ) - y(κ) (25)

[0215] Adjust the weight w(κ) in an iterative manner to make the error e(κ) converge to the minimum value, as shown in the following formula:

[0216] w(κ + 1) = {1 - 2μ(κ)γ(κ)}w(κ) + 2μ(κ)e(κ)x(κ) (26)

[0217] γ(κ + 1) = γ(κ) - 2μ(κ)ρe(κ)x T (κ)w(κ - 1) (27)

[0218] μ(κ + 1) = λμ(κ) + γ(κ)P 2 (κ) (28)

[0219] where μ(κ) is the variable step size, γ(κ) is the change omission factor, λ ∈ (0, 1) and ρ > 0 are the convergence time control parameters;

[0220] Calculate the error autocorrelation P(κ) of the error e(κ) at time κ and the error e(κ - 1) at time κ - 1, and determine whether the error e(κ) converges to the minimum value. The error autocorrelation P(κ) is shown in the following formula:

[0221] P(κ) = βP(κ - 1) + (1 - β)e(κ)e(κ - 1) (29)

[0222] where β ∈ (0, 1) is the exponentially weighted parameter that controls the average estimation time;

[0223] Based on the VLLMS algorithm, establish a parallel controller control scheme, as Figure 4 shown.

[0224] Step 3.1: Calculate the phase voltage amplitude according to the instantaneous voltages of phases a, b, and c of the power grid, and calculate the in-phase components and quadrature components of phases a, b, and c of the power grid respectively;

[0225] According to the instantaneous voltages u sa , u sb , u sc of phases a, b, and c of the power grid, calculate the phase voltage amplitude V sp , as shown in the following formula:

[0226]

[0227] Calculate the in-phase components j pa , j pb , j pc and quadrature components j qa , j qb , j qc of phases a, b, and c of the power grid respectively, as shown in the following formula:

[0228]

[0229] Step 3.2: Based on the VLLMS algorithm, take the in-phase components j pa , j pb , j pc of phases a, b, and c of the power grid as the inputs of the VLLMS algorithm, take the load currents i la , i lb , i lc as the desired outputs of the VLLMS algorithm, and extract the active components of the load currents; take the quadrature components j qa , j qb , j qc of phases a, b, and c of the power grid as the inputs of the VLLMS algorithm, take the load currents as the desired outputs of the VLLMS algorithm, and extract the reactive components of the load currents;

[0230] Take the in-phase components jpa , j pb , j pc As the input x(κ) of the VLLMS algorithm, the load current i la , i lb , i lc As the expected output d(κ) of the VLLMS algorithm, iteratively calculate the amplitudes w pa , w pb , w pc , the amplitude w pa of the active component of the load current in phase a of the power grid at time κ + 1 is as follows:

[0231]

[0232] where w pa (κ) is the amplitude of the active component of the load current in phase a of the power grid at time κ, e pa (κ) is the error of the load current in phase a of the power grid at time κ, μ pa (κ) is the variable step size of the load current in phase a of the power grid at time κ, γ pa (κ) is the change omission factor of the load current in phase a of the power grid at time κ, j pa (κ) is the in-phase component of phase a of the power grid at time κ, i la (κ) is the load current in phase a of the power grid at time κ;

[0233] The amplitudes w pb (κ + 1), w pc (κ + 1) of the active components of the load currents in phases b and c of the power grid at time κ + 1 are as follows:

[0234]

[0235] where w pb (κ) is the amplitude of the active component of the load current in phase b of the power grid at time κ, w pc (κ) is the amplitude of the active component of the load current in phase c of the power grid at time κ, e pb (κ) is the error of the load current in phase b of the power grid at time κ, e pc (κ) is the error of the load current in phase c of the power grid at time κ, μ pb (κ) is the variable step size of the load current in phase b of the power grid at time κ, μ pc (κ) is the variable step size of the load current in phase c of the power grid at time κ, γ pb (κ) is the change omission factor of the load current in phase b of the power grid at time κ, γ pc (κ) is the change omission factor of the load current in phase c of the power grid at time κ, j pb (κ) is the in-phase component of phase b of the power grid at time κ, jpc (κ) is the in-phase component of phase c of the power grid at time κ;

[0236] The orthogonal components j of phases a, b, and c of the power grid qa , j qb , j qc are used as the input x(κ) of the VLLMS algorithm, and the load currents i la , i lb , i lc are used as the expected output d(κ) of the VLLMS algorithm. The magnitudes w qa , w qb , w qc of the reactive components of the load currents of phases a, b, and c of the power grid are iteratively calculated. The magnitude w pa of the reactive component of the load current of phase a of the power grid at time κ + 1 is as shown in the following formula:

[0237]

[0238] where w qa (κ) is the magnitude of the reactive component of the load current of phase a of the power grid at time κ, e qa (κ) is the error of the load current of phase a of the power grid at time κ, μ qa (κ) is the variable step size of the load current of phase a of the power grid at time κ, γ qa (κ) is the change omission factor of the load current of phase a of the power grid at time κ, j qa (κ) is the phase orthogonal component of the power grid of phase a at time κ, i la (κ) is the load current of phase a of the power grid at time κ;

[0239] The magnitudes w qb (κ + 1), w qc (κ + 1) of the reactive components of the load currents of phases b and c of the power grid at time κ + 1 are as shown in the following formula:

[0240]

[0241] where w qb (κ) is the magnitude of the reactive component of the load current of phase b of the power grid at time κ, w qc (κ) is the magnitude of the reactive component of the load current of phase c of the power grid at time κ, e qb (κ) is the error of the load current of phase b of the power grid at time κ, e qc (κ) is the error of the load current of phase c of the power grid at time κ, μ qb (κ) is the variable step size of the load current of phase b of the power grid at time κ, μ qc (κ) is the variable step size of the load current of phase c of the power grid at time κ, γ qb(κ) is the change omission factor of the load current of phase b of the power grid at time κ, γ qc (κ) is the change omission factor of the load current of phase c of the power grid at time κ, j pb (κ) is the quadrature component of phase b of the power grid at time κ, j pc (κ) is the quadrature component of phase c of the power grid at time κ;

[0242] Calculate the average value w of the active component of the load current respectively pavg and the average value w of the reactive component of the load current qavg , as shown in the following formula:

[0243]

[0244] Step 3.3: Calculate the control compensation at time κ + 1, and based on the power supply power P of the DC power supply unit PV and the phase voltage amplitude V sp synthesize the reference current, and calculate the total amplitude of the reference current based on the average value w of the active component of the load current pavg , combined with the control compensation and the reference current at time κ + 1;

[0245] Since there is a certain active power loss in the parallel converter switch, in order to maintain the DC link voltage, by comparing the DC link voltage V dc and the reference DC bus voltage V dcref calculate the control compensation amount w loss (κ + 1), as shown in the following formula:

[0246] e dc (κ) = V dcref (κ) - V dc (κ) (39)

[0247] w loss (κ + 1) = w loss (κ) + k p {e dc (κ + 1) - e dc (κ)} + k i e dc (κ + 1) (40)

[0248] Among them, e dc (κ) is the error between the DC link voltage V dc and the reference DC bus voltage V dcref , e dc (κ + 1) is the error between the DC link voltage V dc and the reference DC bus voltage V dcref , w loss (κ) is the control compensation amount at time κ, kp is the correction coefficient, k i is the correction coefficient;

[0249] According to the power generation power P of the photovoltaic array PV and the total amplitude V of the output voltage of the photovoltaic array sp synthesize the reference current i sa , i sb , i sc the total amplitude w of PV :

[0250]

[0251] Based on the average value w of the active component of the load current pavg , combined with the control compensation w at the (κ + 1)th moment loss (κ + 1), calculate the reference current i sa , i sb , i sc the total amplitude w of PV the active component w of sp and the reference current i sa , i sb , i sc the total amplitude w of PV the reactive component, as shown in the following formula:

[0252] w sp = w pavg + w loss - w PV (42)

[0253] w sq = - w qavg (43)

[0254] Step 3.4: Synthesize the reference source current as the control signal of the parallel converter;

[0255] According to the total amplitude w of the reference current i sa , i sb , i sc the active component w of PV , the reactive component w of the total amplitude w of the reference current i sp 、the in-phase component j of each phase sa , j sb , j sc the total amplitude w of PV and the orthogonal component j of each phase sq 、the in-phase component j of each phase pa , j pb , j pc synthesize the reference source current qa , j qb , j qc As the control signal of the parallel converter, it is shown in the following formula:

[0256]

[0257] Wherein, is the active component of the reference current i sa and is the reactive component of the reference current i sa ; is the active component of the reference current i sb and is the reactive component of the reference current i sb ; is the active component of the reference current i sc and is the reactive component of the reference current i sc ;

[0258] Step 4: Construct a virtual inertia control strategy as the control strategy of the battery energy management system;

[0259] To ensure that the system has sufficient inertia support, a new type of power-based energy storage virtual inertia control strategy is proposed by referring to the Newtonian mechanics idea. The inertia support ability of this strategy is proportional to the square of the voltage fluctuation amplitude and is not affected by the voltage change rate. At the same time, the greater the voltage fluctuation, the greater the inertia support ability provided, solving the problem that the traditional virtual inertia control strategy cannot provide inertia support for the system when the voltage change rate is negative or zero, as Figure 5 shown in the topology structure of the battery energy management system.

[0260] Referring to the Newtonian mechanics law F = CρSv 2 / 2 = D c v 2 , where D c = CρS / 2, a virtual inertia control strategy is constructed as shown in the following formula:

[0261] P c = sign(ΔU)ΔU 2 C c (46)

[0262] Wherein, P c is the output power of the virtual inertia control, the DC voltage change amount ΔU = U Hset - U H , U Hset is the DC rated voltage, U H is the DC voltage, C c is the virtual inertia control coefficient, and sign(·) is the sign function;

[0263] In the virtual inertia control strategy, the output power P of the virtual inertia control c is proportional to the square of the DC voltage change ΔU, which is used to ensure rapid release or absorption of energy when voltage fluctuations occur, providing inertial support for the series converter and the parallel converter; the sign function sign(△U) is used to determine whether the voltage is in a sudden rise or a temporary drop condition. sign(△U) = 1 represents the voltage temporary drop condition, and the battery management system rapidly releases energy; sign(△U) = -1 represents the voltage sudden rise condition, and the battery management system rapidly absorbs energy;

[0264] The output power P of the virtual inertia control c varies with the DC voltage change ΔU and the virtual inertia control coefficient C c The change trend is as follows:

[0265] (1) The output power P of the virtual inertia control c is negative, indicating that when the voltage suddenly rises: the input power of the battery energy management system decreases under the control of the virtual inertia control strategy, suppressing the voltage rise. As the DC voltage change ΔU increases, the output power P of the virtual inertia control c rapidly decreases. The larger the DC voltage change ΔU, the more power the battery energy management system absorbs. When the virtual inertia control coefficient C c increases, the power absorbed by the battery energy management system increases accordingly, indicating that the larger the virtual inertia control coefficient C c , the stronger the inertial support ability of the new control strategy.

[0266] (2) The output power P of the virtual inertia control c is positive, indicating that when the voltage temporarily drops, the energy storage system outputs power under the control of the new virtual inertia control strategy, suppressing the voltage drop. As the DC voltage change ΔU decreases, the output power P of the virtual inertia control c rapidly rises, indicating that the larger the drop amplitude of the DC voltage change ΔU, the more power the energy storage system outputs. When the virtual inertia control coefficient C c increases, the power output by the energy storage system increases accordingly.

[0267] From the above analysis, it can be seen that in the virtual inertia control strategy, the power absorbed by the energy storage system is directly related to the amplitude of the DC voltage change ΔU and the virtual inertia control coefficient C c and has nothing to do with its change rate. At the same time, when the system needs inertial support, it can quickly respond to the power demand of the system, having obvious advantages compared with the existing virtual inertia control strategy.

[0268] The state space equation of the battery energy management system is shown as the following formula:

[0269]

[0270] Among them, C 1 is the filtering capacitor of the upper arm of the high-voltage side of the converter, C 2 is the filtering capacitor of the lower arm of the high-voltage side of the converter, L is the filtering inductor of the converter, R′ is the parasitic resistance of the filtering inductor, u C1 is the voltage of the filtering capacitor of the upper arm of the high-voltage side of the converter, u C2 is the voltage of the filtering capacitor of the lower arm of the high-voltage side of the converter, u 1 is the voltage of the low-voltage side of the converter, I L is the current of the filtering inductor, D is the duty cycle of the switching device V 2 's duty cycle, I 0 is the output current of the converter;

[0271] The state-space equation of the virtual inertia control strategy is shown as the following formula:

[0272]

[0273] Among them, d is the duty cycle of the virtual inertia control strategy, d P is the proportional component of the duty cycle of the virtual inertia control strategy, d I is the integral component of the duty cycle of the virtual inertia control strategy, K IP is the proportional coefficient, K II is the integral coefficient, K c = C c / U H is the virtual inertia control factor;

[0274] According to the Lyapunov theory, the derivative dd I of the integral component d I of the duty cycle of the virtual inertia control strategy with respect to dt is linearized as shown in the following formula:

[0275]

[0276] The state-space matrix A of the virtual inertia control strategy is obtained as:

[0277]

[0278] Analysis of the new virtual inertia control strategy by the state matrix A shows that as K c increases, the eigenvalues move towards the imaginary axis, indicating that as K c increases, the stability margin of the system becomes smaller and smaller. Therefore, when designing the virtual inertia control coefficient, in addition to considering the actual control effect, the influence of K c on the stability margin of the system should also be considered to ensure the stable and reliable operation of the system.

[0279] Step 5: For the non-ideal voltage condition, based on PB control and SM control, construct the PB-SM compensation strategy for the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding

[0280] When considering the non-ideal grid voltage, it is difficult to guarantee the power quality at the load end. Therefore, in this embodiment, a strategy of combining PB (Passivity-based) control and SM (Sliding mode) control is proposed for power quality compensation of the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding. First, for the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding with passivity characteristics, construct the EL (Euler-Lagrange) model of PB control; then derive the control law of the PB-SM control compensation strategy under non-ideal grid voltage conditions. The PB-SM compensation strategy has the characteristics of fast response speed and global steady state of PB control, and also has the advantages of strong anti-interference and robustness of SM control.

[0281] Step 5.1: For the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding with passivity characteristics, construct the EL model of PB control and construct the positive and negative sequence PB control laws of the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding

[0282] Establish the unified models of the series converter and the parallel converter in the two-phase stationary coordinate system as shown in the following formula:

[0283]

[0284] where, u sd1 and u sq1 are respectively the voltages of the d-axis and q-axis of the DC side voltage of the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding converted into the two-phase stationary coordinate system, u sd and u sq are respectively the voltages of the d-axis and q-axis of the output voltage of the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding in the two-phase stationary coordinate system, L is the inductor of the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding, i d and i q are respectively the grid currents of the d-axis and q-axis in the two-phase stationary coordinate system;

[0285] Based on the unified models of the series converter and the parallel converter in the two-phase stationary coordinate system, construct the PB control EL model of the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding as shown in the following formula:

[0286]

[0287] where, is the state vector, is the input vector, is the energy storage matrix, is the dissipation matrix, is the interconnection matrix;

[0288] For the PB - controlled EL model of the new - energy micro - grid power - quality improvement device with coordinated optical - storage feeding, if the equilibrium point of the system is the state - error variable is x e = x - x * , and the storage function is If H(x e ) tends to 0 when it is stable, then x e can also be stable to 0.

[0289] The derivative of the energy - storage function is obtained from the PB - controlled EL model as shown in the following formula:

[0290]

[0291] The new - energy micro - grid power - quality improvement device with coordinated optical - storage feeding has strict passivity, that is, the increase in system energy H(x e (t)) - H(x e (0)) is lower than the externally added energy

[0292] Under the two - phase stationary coordinate system, the positive - sequence current equilibrium point x +* and the negative - sequence current equilibrium point x -* of the new - energy micro - grid power - quality improvement device with coordinated optical - storage feeding are respectively:

[0293]

[0294] where, is the positive - sequence current reference value of the grid current on the d - axis under the two - phase stationary coordinate system, is the positive - sequence current reference value of the grid current on the q - axis under the two - phase stationary coordinate system, is the negative - sequence current reference value of the grid current on the d - axis under the two - phase stationary coordinate system, is the negative - sequence current reference value of the grid current on the q - axis under the two - phase stationary coordinate system;

[0295] The state - variable errors and are:

[0296]

[0297] where, x + is the positive - sequence component of the state vector x, x -is the negative sequence component of the state vector x;

[0298] The state variable error and are introduced into the PB control EL model of the new energy microgrid power quality improvement device with coordinated photovoltaic and energy storage feeding, as shown in the following formula:

[0299]

[0300] Select the positive and negative sequence energy storage functions H + (x e ) and H - (x e ), as shown in the following formula:

[0301]

[0302] Inject damping R g into the resistance R of the new energy microgrid power quality improvement device system with coordinated photovoltaic and energy storage feeding to obtain the interconnected matrix R t ′ after injecting damping, as shown in the following formula:

[0303]

[0304] Among them, and are the positive sequence damping amount and negative sequence damping amount of the interconnected matrix R t ′ after injecting damping respectively, and are the positive sequence damping amount and negative sequence damping amount of the damping amount R g respectively, is the positive sequence damping component of the d-axis in the two-phase stationary coordinate system, is the positive sequence damping component of the q-axis in the two-phase stationary coordinate system, is the negative sequence damping component of the d-axis in the two-phase stationary coordinate system, is the negative sequence damping component of the q-axis in the two-phase stationary coordinate system;

[0305] Obtain the positive and negative sequence PB control laws of the new energy microgrid power quality improvement device with coordinated photovoltaic and energy storage feeding, as shown in the following formula:

[0306]

[0307] Among them, is the positive sequence output voltage of the d-axis in the two-phase stationary coordinate system, is the positive sequence output voltage of the q-axis in the two-phase stationary coordinate system, is the negative - sequence output voltage of the d - axis in the two - phase stationary coordinate system, is the negative - sequence output voltage of the q - axis in the two - phase stationary coordinate system, is the positive - sequence line voltage of the d - axis in the two - phase stationary coordinate system, is the positive - sequence line voltage of the q - axis in the two - phase stationary coordinate system, is the negative - sequence line voltage of the d - axis in the two - phase stationary coordinate system, is the negative - sequence line voltage of the q - axis in the two - phase stationary coordinate system, is the positive - sequence current of the grid current of the d - axis in the two - phase stationary coordinate system, is the positive - sequence current of the grid current of the q - axis in the two - phase stationary coordinate system, is the negative - sequence current of the grid current of the d - axis in the two - phase stationary coordinate system, is the negative - sequence current of the grid current of the q - axis in the two - phase stationary coordinate system;

[0308] Step 5.2: Add the SM control on the basis of the PB control of the EL model to obtain the control law of the PB - SM control compensation strategy of the new - energy micro - grid power - quality improvement device with coordinated optical storage feeding under non - ideal grid voltage conditions;

[0309] Select the sliding mode surfaces s 1 、s 2 as:

[0310]

[0311] Based on the unified model of the series converter and the parallel converter in the two - phase stationary coordinate system, the positive - and negative - sequence models of the grid current are obtained as shown in the following formula:

[0312]

[0313] To reduce the high - frequency chattering problem of the SM control, use the sign functions sgn(s 1 )、sgn(s 2 ) to reduce chattering, and select the reaching law of the SM control as:

[0314]

[0315] where, ρ + is the positive - sequence adjustment parameter of the SM control, ρ - is the negative - sequence adjustment parameter of the SM control, is the positive - sequence adjustment parameter of the d - axis SM control in the two - phase stationary coordinate system, is the positive - sequence adjustment parameter of the q - axis SM control in the two - phase stationary coordinate system, is the negative - sequence adjustment parameter of the d - axis SM control in the two - phase stationary coordinate system, is the negative sequence regulation parameter of q-axis SM control in the two-phase stationary coordinate system, u + is the positive sequence component of the input vector u, u - is the negative sequence component of the input vector u;

[0316] Replace the sign function sgn(·) with the saturation function sat(·), as shown in the following formula:

[0317]

[0318] Obtain the relationship between the grid current i d in the two-phase stationary coordinate system and the reference value i dref of the grid current in the two-phase stationary coordinate system, as shown in the following formula:

[0319]

[0320] Obtain the control law of the PB-SM control compensation strategy under non-ideal grid voltage conditions, as shown in the following formula:

[0321]

[0322] By selecting appropriate damping parameters and regulation parameters Adjust the control law of the PB-SM control compensation strategy of the new energy microgrid power quality improvement device with coordinated optical storage feeding under non-ideal grid voltage conditions, so as to realize the control of the grid voltage by the new energy microgrid power quality improvement device with coordinated optical storage feeding under non-ideal voltage conditions.

[0323] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope defined by the claims of the present invention.

Claims

1. A device for improving the power quality of a new energy microgrid with coordinated photovoltaic and energy storage feeding, characterized in that: It includes a series converter, a parallel converter, a battery energy management system and a DC power supply unit; The series converter and the parallel converter are connected to a common DC bus in a back-to-back manner; the series converter is a controlled current source, which is connected in series with the three-phase transformer of the power grid through a first resistor, a series converter interface inductor, and a series converter capacitor; the parallel converter is a controlled voltage source, which is connected in parallel with the three-phase load through a second resistor, a parallel converter interface inductor, and a parallel converter capacitor; the DC power supply unit includes a photovoltaic array and a reverse blocking diode, and the photovoltaic array and the reverse blocking diode are connected in series to a battery energy management system; the battery energy management system is a three-level bidirectional DC / DC converter structure, which is connected at both ends of the series converter.

2. A method for improving the power quality of a new energy microgrid with coordinated photovoltaic and energy storage feeding, based on the system described in claim 1 to improve the power quality of a new energy microgrid, characterized in that: The following steps are involved: Step 1: Establish mathematical models of the series converter and the parallel converter in a stationary coordinate system respectively; Step 2: Construct a control strategy based on control target decoupling, and use the control strategy based on control target decoupling to realize the control of the series converter; Step 3: Construct an adaptive compensation control strategy based on the VLLMS algorithm as the control strategy of the parallel converter, extract the active component and reactive component of the load current respectively, and generate the control signal of the parallel converter; Step 4: Construct a virtual inertia control strategy as the control strategy of the battery energy management system; Step 5: For non-ideal voltage conditions, based on PB control and SM control, a PB-SM compensation strategy for the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feed-in is constructed.

3. According to claim 2, a method for improving power quality of a new energy microgrid with coordinated photovoltaic and energy storage feeding is characterized by: The step 1 of establishing the mathematical model of the series converter and the parallel converter in the stationary coordinate system includes: The mathematical model of the series converter in the stationary coordinate system is shown in the following formula: Among them, L se is the series converter interface inductor, i f is the current flowing through the series converter interface inductor L se The current, C se is the series converter capacitor, u f is the series converter capacitor C se voltage, R is the resistance, i s is the grid current, u′ is the output voltage of the series converter, and t is the time; The mathematical model of the parallel converter in the stationary coordinate system is shown in the following formula: Among them, L sh is the parallel converter interface inductance, i o is the current flowing through the parallel converter interface inductor L sh The current, u is the output voltage of the parallel converter, u c is the parallel converter capacitor C sh The voltage, i c Compensation current for parallel converters; Set the switching function S of any bridge arm of the series converter x The switching function S of any bridge arm of the parallel converter x 'for: Wherein, a, b, and c are three bridge arms of a series converter or a parallel converter respectively; The output voltage u′ of the series converter and the output voltage u of the parallel converter are: Among them, the rotation factor α = e j(2π / 3) ,u dc is the DC bus voltage.

4. The method for improving power quality of a new energy microgrid with coordinated photovoltaic and energy storage feed-in according to claim 3 is characterized by: The step 2 comprises: Step 2.1: Set the control target, establish the control equation of the discrete series converter, and construct the cost function; Setting the current of the series converter interface inductor and the voltage of the series converter capacitor as control targets; The control equation of the series converter is established as shown in the following formula: The control equation of the series converter is discretized to obtain the discretized control equation of the series converter, as shown in the following formula: Among them, i fx (k+1) is the current flowing through the inductor L on any bridge arm x at time k+1 se The current, u fx (k+1) is the capacitance C on any bridge arm x at time k+1 se The voltage, i sx (k) is the grid current on any bridge arm x at time k, u′ x (k) is the output voltage of the series converter on any bridge arm x at time k, i fx (k) is the current flowing through the inductor L on any bridge arm x at time k se The current, u fx (k) is the capacitance C on any bridge arm x at time k se The voltage of the circuit, k is the current moment, T s is the sampling period; Constructing the value function g x , as shown in the following formula: in, is the grid current reference value at time k+1; Step 2.2: Construct a delay compensation control equation, perform delay compensation on the discrete series converter control equation, and obtain a predicted value function; Construct the delay compensation control equation as shown in the following formula: After delay compensation, the predicted value function g at time k+2 is obtained. x 'for: in, is the current flowing through the inductor L on any bridge arm x se The reference current; Step 2.3: Based on the delay compensation control equation, a prediction equation is established with the grid current as the only control variable to decouple the control target; The prediction equation is shown as follows: Step 2.4: Calculate the output voltage reference value of the series controller, convert the grid current reference into the series converter output voltage reference through SVPWM modulation, and realize the control of the series converter; For the value function g x Find the partial derivative and set the partial derivative value of the value function to 0, as shown in the following formula: Calculate the current flowing through the inductor L on any bridge arm x of the series converter at time k+2 se The current i fx (k+2), and based on the prediction equation, the output voltage reference value u of the series converter at time k is obtained x ′(k): Among them, the grid current reference value at time k+2 is As shown in the following formula: Get the output voltage reference value u of the series converter at time k x ′(k) is:

5. The method for improving power quality of a new energy microgrid with coordinated photovoltaic and energy storage feed-in according to claim 4 is characterized by: The step 3 comprises: Step 3.1: Calculate the phase voltage amplitude according to the instantaneous voltage of phases a, b and c of the power grid, and calculate the in-phase component and quadrature component of phases a, b and c of the power grid respectively; According to the instantaneous voltage u of phases a, b and c of the power grid sa 、u sb 、u sc Calculate the phase voltage amplitude V sp , as shown in the following formula: Calculate the in-phase component j of phases a, b and c of the power grid respectively pa ,j pb ,j pc and the orthogonal component j qa ,j qb ,j qc , as shown in the following formula: Step 3.2: Based on the VLLMS algorithm, the in-phase components j of phases a, b, and c of the power grid are pa ,j pb ,j pc As the input of the VLLMS algorithm, the load current i la ,i lb ,i lc As the expected output of the VLLMS algorithm, the active component of the load current is extracted; the orthogonal components j of the grid phases a, b and c are qa ,j qb ,j qc As the input of the VLLMS algorithm, the load current is taken as the expected output of the VLLMS algorithm, and the reactive component of the load current is extracted; The in-phase components j of phases a, b and c of the power grid pa ,j pb ,j pc As the input x(κ) of the VLLMS algorithm, the load current i la ,i lb ,i lc As the expected output d(κ) of the VLLMS algorithm, the amplitude w of the active component of the load current of phases a, b, and c of the power grid is iteratively calculated pa ,w pb ,w pc , the amplitude w of the active component of the load current of phase a of the power grid at time κ+1 pa (κ+1) is shown in the following formula: Among them, w pa (κ) is the amplitude of the active component of the load current of phase a of the power grid at time κ, e pa (κ) is the error of the load current of phase a of the power grid at time κ, μ pa (κ) is the variable step size of the load current of phase a of the power grid at time κ, γ pa (κ) is the change omission factor of the load current of phase a of the power grid at time κ, j pa (κ) is the in-phase component of phase a of the power grid at time κ, i la (κ) is the load current of phase a of the power grid at time κ; The amplitude w of the active component of the load current of grid phase b and grid phase c at time κ+1 pb (κ+1), w pc (κ+1), as shown in the following formula: Among them, w pb (κ) is the amplitude of the active component of the load current of phase b of the power grid at time κ, w pc (κ) is the amplitude of the active component of the load current of phase c of the power grid at time κ, e pb (κ) is the error of the load current of phase b of the power grid at time κ, e pc (κ) is the error of the load current of phase c of the power grid at time κ, μ pb (κ) is the variable step size of the load current of phase b of the power grid at time κ, μ pc (κ) is the variable step size of the load current of phase c of the power grid at time κ, γ pb (κ) is the change omission factor of the load current of phase b of the power grid at time κ, γ pc (κ) is the change omission factor of the load current of phase c of the power grid at time κ, j pb (κ) is the in-phase component of phase b of the power grid at time κ, j pc (κ) is the in-phase component of phase c of the power grid at time κ; The orthogonal components j of the grid phases a, b and c are qa ,j qb ,j qc As the input x(κ) of the VLLMS algorithm, the load current i la ,i lb ,i lc As the expected output d(κ) of the VLLMS algorithm, the magnitude w of the reactive component of the load current of phases a, b, and c of the grid is iteratively calculated. qa ,w qb ,w qc , the amplitude w of the reactive component of the load current of phase a of the power grid at time κ+1 pa (κ+1) is shown in the following formula: Among them, w qa (κ) is the amplitude of the reactive component of the load current of phase a of the power grid at time κ, e qa (κ) is the error of the load current of phase a of the power grid at time κ, μ qa (κ) is the variable step size of the load current of phase a of the power grid at time κ, γ qa (κ) is the change omission factor of the current of phase a of the power grid load at time κ, j qa (κ) is the orthogonal component of phase a of the power grid at time κ, i la (κ) is the load current of phase a of the power grid at time κ; The amplitude w of the reactive component of the load current of grid phase b and grid phase c at time κ+1 qb (κ+1), w qc (κ+1), as shown in the following formula: Among them, w qb (κ) is the amplitude of the reactive component of the load current of phase b of the power grid at time κ, w qc (κ) is the amplitude of the reactive component of the load current of phase c of the power grid at time κ, e qb (κ) is the error of the load current of phase b of the power grid at time κ, e qc (κ) is the error of the load current of phase c of the power grid at time κ, μ qb (κ) is the variable step size of the load current of phase b of the power grid at time κ, μ qc (κ) is the variable step size of the load current of phase c of the power grid at time κ, γ qb (κ) is the change omission factor of the load current of phase b of the power grid at time κ, γ qc (κ) is the change omission factor of the negative c-phase load current of the power grid at time κ, j pb (κ) is the orthogonal component of the grid phase b at time κ, j pc (κ) is the orthogonal component of the grid phase c at time κ; Calculate the average value w of the active component of the load current respectively pavg and the average value of the reactive component of the load current w qavg , as shown in the following formula: Step 3.3: Calculate the control compensation at time κ+1 and calculate the power supply power P of the DC power supply unit. PV and phase voltage amplitude V sp The synthetic reference current is based on the average value of the active component of the load current w pavg , the total amplitude of the reference current is calculated by combining the control compensation and the reference current at time κ+1; Since there is a certain active power loss in the parallel converter switch, in order to maintain the DC link voltage, the DC link voltage V dc and the reference DC bus voltage V dcref Calculate the control compensation w at time κ+1 loss (κ+1), as shown in the following formula: e dc (k)=V dcref (k)-V dc (k) (24) w loss (k+1)=w loss (k)+k p {e dc (k+1)-e dc (k)}+k i e dc (k+1) (25) Among them, e dc (κ) is the DC link voltage V at time κ dc and the reference DC bus voltage V dcref The error, e dc (κ+1) is the DC link voltage V at time κ+1 dc and the reference DC bus voltage V dcref The error, w loss (κ) is the control compensation amount at time κ, k p is the correction factor, k i is the correction factor; According to the photovoltaic array power generation P PV And the total output voltage amplitude of the photovoltaic array V sp Synthetic reference current i sa ,i sb ,i sc The total amplitude w PV : Based on the average value of the active component of the load current w pavg , combined with the control compensation w at time κ+1 loss (κ+1), calculate the reference current i sa ,i sb ,i sc The total amplitude w PV The active component w sp and the reference current i sa ,i sb ,i sc The total amplitude w PV The reactive component w sq , as shown in the following formula: In sp =in pavg +in loss -In PV (27) In sq =-in qavg (28) Step 3.4: synthesize the reference source current as the control signal of the parallel converter; According to the reference current i sa ,i sb ,i sc The total amplitude w PV The active component w sp , reference current i sa ,i sb ,i sc The total amplitude w PV The reactive component w sq , the in-phase component j of each phase pa ,j pb ,j pc and the orthogonal components j of each phase qa ,j qb ,j qc Synthesized reference source current As the control signal of the parallel converter, it is shown in the following formula: in, is the reference current i sa The active component of is the reference current i sa The reactive component of is the reference current i sb The active component of is the reference current i sb The reactive component of is the reference current i sc The active component of is the reference current i sc The reactive component.

6. The method for improving power quality of a new energy microgrid with coordinated photovoltaic and energy storage feed-in according to claim 5, characterized in that: The specific method of step 4 is: Construct a virtual inertia control strategy as shown in the following formula: P c =sign(ΔU)ΔU 2 C c (31) Among them, P c The output power is controlled by virtual inertia, and the DC voltage change ΔU = U Hset -U H , U Hset is the DC rated voltage, U H is the DC voltage, C c is the virtual inertia control coefficient, sign(·) is the sign function; In the virtual inertia control strategy, the virtual inertia controls the output power P c It is proportional to the square of the DC voltage change ΔU, and is used to ensure rapid release or absorption of energy when voltage fluctuations occur, providing inertial support for series converters and parallel converters; the sign function sign(△U) is used to determine whether the voltage is in a sudden rise or sag condition, sign(△U) = 1 for a voltage sag condition, and the battery management system quickly releases energy; sign(△U) = -1 for a voltage sudden rise condition, and the battery management system quickly absorbs energy.

7. The method for improving power quality of a new energy microgrid with coordinated photovoltaic and energy storage feed-in according to claim 6 is characterized by: The step 5 comprises: Step 5.1: For the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding with passive characteristics, the EL model of PB control is constructed, and the positive and negative sequence PB control law of the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding is constructed; Step 5.2: Introduce SM control based on the PB control of the EL model to obtain the control law of the PB-SM control compensation strategy for the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage feeding under non-ideal grid voltage conditions.

8. The method for improving power quality of a new energy microgrid with coordinated photovoltaic and energy storage feed-in according to claim 7, characterized in that: The step 5.1 comprises: A unified model of the series converter and the parallel converter in a two-phase stationary coordinate system is established, as shown in the following formula: Among them, u sd1 and u sq1 The DC side voltage of the new energy microgrid power quality improvement device fed by the photovoltaic and energy storage coordination is converted into the d-axis voltage and the q-axis voltage in the two-phase stationary coordinate system, u sd and u sq are the d-axis voltage and q-axis voltage of the output voltage of the new energy microgrid power quality improvement device fed by the photovoltaic and energy storage coordination in the two-phase stationary coordinate system, L is the inductance of the new energy microgrid power quality improvement device fed by the photovoltaic and energy storage coordination, i d and i q are the grid current of d axis and the grid current of q axis in the two-phase stationary coordinate system respectively; Based on the unified model of series converter and parallel converter in two-phase stationary coordinate system, the PB control EL model of the new energy microgrid power quality improvement device with coordinated photovoltaic and energy storage feeding is constructed, as shown in the following formula: in, is the state vector, is the input vector, is the energy storage matrix, is the dissipation matrix, is an interconnection matrix; The positive sequence current balance point x of the power quality improvement device of the new energy microgrid with coordinated photovoltaic and energy storage in the two-phase stationary coordinate system +* and negative sequence current balance point x -* They are: in, is the positive sequence current reference value of the grid current on the d-axis in the two-phase stationary coordinate system, is the positive sequence current reference value of the grid current on the q axis in the two-phase stationary coordinate system, is the negative sequence current reference value of the grid current on the d-axis in the two-phase stationary coordinate system, is the negative sequence current reference value of the grid current on the q axis in the two-phase stationary coordinate system; State variable error and for: Among them, x + is the positive sequence component of the state vector x, x - is the negative sequence component of the state vector x; The state variable error and The PB control EL model of the new energy microgrid power quality improvement device with the introduction of photovoltaic and storage coordinated feeding is shown in the following formula: Inject damping R into the resistor R of the power quality improvement device system of the new energy microgrid coordinated with photovoltaic storage g , and the interconnection matrix R after injection damping is obtained t ′, as shown in the following formula: in, and The interconnection matrix R′ after injecting damping t Positive sequence damping and negative sequence damping, and R g The positive sequence damping and negative sequence damping of for The positive sequence damping component of the d-axis in the two-phase stationary coordinate system is: for The positive sequence damping component of the q axis in the two-phase stationary coordinate system is: for The negative sequence damping component of the d-axis in the two-phase stationary coordinate system is: for The negative sequence damping component of the q axis in the two-phase stationary coordinate system; The positive and negative sequence PB control law of the new energy microgrid power quality improvement device with coordinated photovoltaic and storage input is obtained, as shown in the following formula: in, is the positive sequence output voltage of the d-axis in the two-phase stationary coordinate system, is the positive sequence output voltage of the q axis in the two-phase stationary coordinate system, is the negative sequence output voltage of the d-axis in the two-phase stationary coordinate system, is the negative sequence output voltage of the q axis in the two-phase stationary coordinate system, is the positive sequence line voltage of the d-axis in the two-phase stationary coordinate system, is the positive sequence line voltage of the q axis in the two-phase stationary coordinate system, is the negative sequence line voltage of the d-axis in the two-phase stationary coordinate system, is the negative sequence line voltage of the q axis in the two-phase stationary coordinate system, is the positive sequence current of the grid current on the d-axis in the two-phase stationary coordinate system, is the positive sequence current of the grid current on the q axis in the two-phase stationary coordinate system, is the negative sequence current of the grid current on the d-axis in the two-phase stationary coordinate system, It is the negative sequence current of the grid current on the q axis in the two-phase stationary coordinate system.

9. The method for improving power quality of a new energy microgrid with coordinated photovoltaic and energy storage feed-in according to claim 8, characterized in that: The step 5.2 comprises: The sliding surfaces s1 and s2 of the power quality improvement device for the new energy microgrid with coordinated photovoltaic and energy storage are selected as follows: Based on the unified model of the series converter and the parallel converter in the two-phase stationary coordinate system, the positive and negative sequence model of the grid current is obtained, as shown in the following formula: Use the sign functions sgn(s1) and sgn(s2) to reduce chattering, and select the approach rate of SM control as: Among them, ρ + is the positive sequence adjustment parameter of SM control, ρ - It is the negative sequence adjustment parameter of SM control. is the positive sequence adjustment parameter of d-axis SM control in the two-phase stationary coordinate system, is the positive sequence adjustment parameter of q-axis SM control in two-phase stationary coordinate system, ρ1 - is the negative sequence adjustment parameter of d-axis SM control in the two-phase stationary coordinate system, is the negative sequence adjustment parameter of q-axis SM control in the two-phase stationary coordinate system, u + is the positive sequence component of the input vector u, u - is the negative sequence component of the input vector u; The saturation function sat(·) is used to replace the sign function sgn(·), as shown in the following formula: Get the grid current i in the two-phase stationary coordinate system d and the grid current reference value i in the two-phase stationary coordinate system dref The relationship is shown in the following formula: The control law of the PB-SM control compensation strategy under non-ideal grid voltage conditions is obtained as shown in the following formula: By choosing appropriate damping parameters and adjustment parameters The control law of the PB-SM control compensation strategy of the new energy microgrid power quality improvement device with coordinated photovoltaic and storage feeding under non-ideal grid voltage conditions is adjusted to realize the control of the grid voltage by the new energy microgrid power quality improvement device with coordinated photovoltaic and storage feeding under non-ideal voltage conditions.

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