Network construction type energy storage converter control method and system

Abstract

The invention discloses a control method and system for a network-forming type energy storage converter, and relates to the technical field of power electronics, and the method comprises the following steps: obtaining sampling signals of voltage and current at the network side of a converter circuit, extracting three-phase voltage and three-phase current, executing network-side power control, and calculating network-side reference voltage and reference angular frequency; converting a modulation signal under a direct current coordinate system into a modulation signal under a static coordinate system based on coordinate system conversion of voltage and current numerical values, and converting the modulation signal into a trigger signal of a switch tube based on a signal modulation algorithm; and obtaining the direct current side current of the converter circuit, executing double-current cooperative control by introducing the reference current, and calculating the phase shift angle between the primary side voltage and the secondary side voltage of the high-frequency transformer. By acquiring the grid-side sampling signal and calculating the reference quantity, it is ensured that the output of the converter and the power grid are kept synchronous, power transmission is optimized, harmonic pollution is reduced, and efficient inversion control is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a control method and system for a grid-connected energy storage converter. Background Art

[0002] With the vigorous development of the new energy industry, photovoltaics, microgrids, energy storage, etc. have ushered in new development opportunities. The above systems all contain DC power characteristics, so AC-DC power converters have become a necessary link. Traditional energy storage inverters usually use a two-stage AC-DC converter, that is, a DC-DC converter plus a DC-AC converter. This structure usually requires the addition of large capacitors on the DC bus at both levels, which not only increases the system volume, reduces the system's power density and service life, but also increases the system cost. The three-phase-single-phase matrix converter is a new type of converter for energy storage. Its AC-DC power conversion and electrical isolation are achieved only through a primary structure. This single-stage structure has no intermediate energy storage link, thereby reducing power loss and has obvious advantages in volume, life and efficiency.

[0003] Three-phase-single-phase matrix converters usually use grid-following control, but as the penetration rate of new energy and power electronic equipment increases, the inertia and damping of the power system decrease, and grid-following control will not be enough to meet the needs of the power grid. Grid-building control can enable energy storage converters to have active support capabilities and solve the above problems. However, the three-phase-single-phase matrix converter has more control freedom, and the DC side of the converter must also be controlled. At the same time, traditional matrix converters mostly use current source type, and existing grid-building technology cannot meet the requirements.

[0004] Therefore, a network control technology for a three-phase to single-phase matrix converter type energy storage converter is needed. Summary of the invention

[0005] Based on this, it is necessary to provide a grid-type energy storage inverter control method and system to address the above technical problems.

[0006] In a first aspect, the present invention provides a control method for a grid-connected energy storage converter, the method comprising the following steps:

[0007] S1, obtaining sampling signals of voltage and current on the grid side of the converter circuit, performing grid side power control by extracting three-phase voltage and three-phase current, calculating grid side reference voltage and reference angular frequency, and generating modulation signals in a DC coordinate system by double closed-loop control of the sampling signal and the reference quantity;

[0008] S2. Based on the coordinate system conversion of the voltage and current values, the modulation signal in the DC coordinate system is converted into the modulation signal in the static coordinate system, and based on the signal modulation algorithm, the modulation signal is converted into a trigger signal of the switch tube, and the trigger control of the switch tube in each sub-circuit in the converter circuit is executed;

[0009] S3. Obtain the DC side current of the converter circuit, perform dual current coordinated control by introducing a reference current, calculate the phase shift angle between the primary and secondary voltages of the high-frequency transformer, and then feed the phase shift angle variable back to the signal modulation algorithm for coordinated control to adjust the transmission power in the converter.

[0010] Further, obtaining sampling signals of voltage and current on the grid side of the converter circuit, extracting three-phase voltage and three-phase current, performing grid-side power control, calculating grid-side reference voltage and reference angular frequency, and generating a modulation signal in a DC coordinate system through double closed-loop control of the sampling signal and the reference quantity include the following steps:

[0011] S11, collecting the three-phase voltage on the three-phase filter capacitor and the three-phase current flowing through the three-phase filter inductor in the AC side filter circuit as the sampling signal on the grid side;

[0012] S12, using the three-phase voltage and the three-phase current to calculate the actual power on the grid side, by setting the grid side reference power, moment of inertia and damping coefficient, establishing an active-frequency control equation, and introducing power regulation into the control, limiting the output frequency of the converter, generating a reactive-voltage control equation, and calculating the power control output voltage;

[0013] S13, using a double closed-loop control converter to decouple the output voltage and the inductor current, and calculating the control amount of the output voltage and current as a modulation signal through parameter calculation of the double closed-loop controller.

[0014] Furthermore, the formula of the active power-frequency control equation is:

[0015]

[0016] In the formula, ω ref is the output frequency; J0 is the initial value of the moment of inertia; k is the power feedback coefficient; ΔP is the difference between the grid-side reference power and the grid-side actual power.

[0017] Furthermore, the formula of reactive power-voltage control equation is:

[0018] u ref =u0+M Q (Q ref -Q e )

[0019] In the formula, u refis the power control output voltage; u0 is the voltage setting value; Q ref is the reactive power setting value on the grid side; Q e is the grid-side reactive power; M Q is the reactive voltage regulation coefficient.

[0020] Furthermore, the output voltage of the converter is decoupled from the feedforward of the inductor current by using a double closed-loop control, and the control amount of the output voltage and current is calculated as a modulation signal by the parameter calculation of the double closed-loop controller, including the following steps:

[0021] S131, using the output of the voltage outer loop as the current given value of the current inner loop, obtaining the proportional parameter and integral parameter of the voltage outer loop proportional-differential controller, and the component of the power control output voltage in the DC coordinate system, establishing the voltage control equation, and calculating the current inner loop given value;

[0022] S132. Control the converter output voltage through the voltage outer loop, control the inductor current through the current inner loop, convert the three-phase current and three-phase voltage on the grid side to the DC coordinate system through the three-phase coordinate system, obtain the proportional parameter and integral parameter of the current inner loop proportional-differential controller (PI controller), combine the current given value of the current inner loop, establish the dual closed-loop controller output formula, and calculate the dual closed-loop controller output.

[0023] Furthermore, the calculation formula of the voltage control equation is:

[0024]

[0025] In the formula, i dref is the component of the current inner loop given value on the d-axis; i qref K is the component of the current inner loop given value on the q axis; vp K is the proportional parameter of the voltage outer loop proportional-differential controller; vl is the integral parameter of the voltage outer loop proportional-differential controller; u dref is the power control output voltage u ref The component below the d axis; u qref is the power control output voltage u ref The component below the q axis; u cd u is the component of the d-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; cq is the component of the q-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; C f is the three-phase filter capacitor; ω ref is the power control output frequency; s is the Laplace operator.

[0026] Furthermore, the output formula of the dual closed-loop controller is:

[0027]

[0028] In the formula, v d is the component of the double closed-loop controller output on the d-axis; v q is the component of the double closed-loop controller output on the q axis; K ip K is the proportional parameter of the current inner loop proportional-differential controller; il is the integral parameter of the current inner loop proportional-differential controller; i dref is the component of the current inner loop given value on the d-axis; i qref is the component of the current inner loop given value on the q axis; i Ld is the component of the three-phase current on the grid side transformed from the three-phase coordinate system to the d-axis component in the DC coordinate system; i Lq u is the component of the three-phase current on the grid side transformed from the three-phase coordinate system to the q-axis component in the DC coordinate system; cd u is the component of the d-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; cq is the component of the q-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; L f is the three-phase filter inductance; ω ref is the power control output frequency; s is the Laplace operator.

[0029] Furthermore, based on the coordinate system conversion of the voltage and current values, the modulation signal in the DC coordinate system is converted into a modulation signal in the static coordinate system, and based on the signal modulation algorithm, the modulation signal is converted into a trigger signal of the switch tube, and the trigger control of the switch tube in each sub-circuit in the converter circuit is executed, including the following steps:

[0030] S21, using inverse Park transform to construct an inverse transform formula of the modulation signal, and converting the modulation signal of the converter circuit in the DC coordinate system into a modulation signal in the static coordinate system;

[0031] S22, based on the space vector pulse width modulation technology, processing the modulation signal after the coordinate system conversion, and converting the modulation signal into a trigger signal of each switch tube in the matrix converter;

[0032] S23. Based on the pulse width modulation technology, the modulation signal after the coordinate system conversion is processed, and the modulation signal is converted into a trigger signal of each switch tube in the full-bridge circuit.

[0033] Furthermore, the DC side current of the converter circuit is obtained, and the reference current is introduced to perform dual current coordinated control, and the phase shift angle between the primary and secondary voltages of the high-frequency transformer is calculated, and then the phase shift angle variable is fed back to the signal modulation algorithm for coordinated control. Adjusting the transmission power in the converter includes the following steps:

[0034] S31, obtaining the square wave amplitude of the input and output voltages of the high-frequency transformer, setting the primary side voltage and the secondary side voltage to have periodic waveforms, and calculating the ideal current during the phase shift period of the high-frequency transformer;

[0035] S32, combining the ideal current with the energy storage side voltage, the phase shift angle between the primary voltage and the secondary voltage of the high-frequency transformer, calculating the transmission power between the primary side voltage and the secondary side voltage, ignoring the transmission loss, and setting the transmission power to the actual power on the grid side;

[0036] S33. The phase shift angle calculation formula is obtained by converting the formula of the ideal current and the actual power on the grid side, and the reference phase shift angle is obtained by closed-loop control of the DC side current. The reference phase shift angle variable is then introduced into the space vector pulse width modulation technology and the pulse width modulation technology, and the triggering time of the matrix converter switch tube and the triggering time of the full-bridge circuit switch tube are kept at the reference phase shift angle to control the transmission power in the converter, wherein the calculation formula of the reference phase shift angle is:

[0037]

[0038] In the formula, K is the reference phase shift angle between the primary side voltage and the secondary side voltage of the high frequency transformer; idcp is the proportional parameter of the proportional-derivative controller in cooperative control; K idcl is the integral parameter of the proportional-derivative controller in cooperative control; i dc is the DC side current; i dc * is the DC side current reference value.

[0039] In a second aspect, a grid-type energy storage converter control system is provided, the system comprising: a converter circuit, a power control module, a dual closed-loop control module, a coordinated control module, a pulse width modulation module, a space vector pulse width modulation module and a coordinate system transformation module;

[0040] Among them, the converter circuit is used to build the circuit structure of the grid-type energy storage converter to realize energy transmission and conversion, including DC energy storage link, DC side filter circuit, full-bridge circuit, high-frequency transformer, matrix converter, AC side filter circuit and grid side circuit;

[0041] The power control module is used to sample the grid-side voltage and current in real time, calculate the active power and reactive power of the converter, and control the output voltage of the converter grid side;

[0042] A dual closed-loop control module is used to control the inductor current in the converter using the inner current loop and the output voltage of the converter using the outer voltage loop, thereby improving the anti-interference capability of the converter;

[0043] A collaborative control module is used to collaboratively control the DC side and AC side of the converter, adjust the phase shift angle between the primary side and the secondary side of the high-frequency transformer, and regulate the transmission power of the converter;

[0044] A pulse width modulation module is used to generate a trigger signal for controlling the switch tube in the matrix converter;

[0045] A space vector pulse width modulation module is used to generate a trigger signal for controlling the switch tube in the full-bridge circuit;

[0046] The coordinate system transformation module is used to transform signals between different coordinate systems.

[0047] The beneficial effects of the present invention are:

[0048] 1. By acquiring the grid-side sampling signal and calculating the reference quantity, the output of the converter is ensured to be synchronized with the grid, which helps to optimize power transmission and reduce harmonic pollution; the modulated signal in the DC coordinate system is converted into a signal in the static coordinate system, and the trigger signal of each switch tube is generated to achieve efficient inverter control, which not only improves the control accuracy of the converter, but also enhances the anti-interference ability of the system; in addition, by sampling the DC side current and combining the current reference quantity, the phase shift angle between the primary and secondary sides of the high-frequency transformer is calculated, which further optimizes the energy conversion efficiency of the system.

[0049] 2. The present invention can simultaneously control the AC side and DC side of the converter, overcoming the limitation that the traditional three-phase-single-phase matrix converter type energy storage converter cannot perform network control, greatly improving the flexibility and adaptability of the system, and being suitable for different grid conditions and load requirements; it not only improves the energy management efficiency of the converter, but also enhances the stability of the power system, provides higher energy quality, promotes the effective use of renewable energy, and provides reliable technical support for the construction of smart grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0051] Figure 1 is a flow chart of a grid-type energy storage converter control method according to an embodiment of the present invention;

[0052] Figure 2 1 is a schematic diagram of the system principle structure of a grid-type energy storage converter control system according to an embodiment of the present invention;

[0053] Figure 3 1 is a schematic diagram of a power control module in a system of a grid-type energy storage converter control system according to an embodiment of the present invention;

[0054] Figure 4 1. It is a schematic diagram of a dual closed-loop control module in a system of a grid-type energy storage converter control system according to an embodiment of the present invention;

[0055] Figure 5 is a schematic diagram of voltage and current waveforms of a high-frequency transformer according to an embodiment of the present invention;

[0056] Figure 6 It is a schematic diagram of a collaborative control module in a system of a grid-type energy storage converter control system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0058] See also Figure 1 , provides a grid-type energy storage converter control method, the method comprising the following steps:

[0059] S1. Obtain sampling signals of voltage and current on the grid side of the converter circuit, perform grid-side power control by extracting three-phase voltage and three-phase current, calculate grid-side reference voltage and reference angular frequency, and generate modulation signals in a DC coordinate system by double closed-loop control of the sampling signal and the reference quantity.

[0060] In the description of the present invention, obtaining sampling signals of voltage and current on the grid side of the converter circuit, performing grid side power control by extracting three-phase voltage and three-phase current, calculating grid side reference voltage and reference angular frequency, and generating a modulation signal in a DC coordinate system by double closed-loop control of the sampling signal and the reference quantity includes the following steps:

[0061] S11, collecting the three-phase voltage on the three-phase filter capacitor and the three-phase current flowing through the three-phase filter inductor in the AC side filter circuit as the sampling signal on the grid side.

[0062] S12. Calculate the actual power on the grid side using the three-phase voltage and three-phase current. Establish the active-frequency control equation by setting the grid-side reference power, moment of inertia and damping coefficient. Introduce power regulation into the control to limit the output frequency of the converter, generate the reactive-voltage control equation, and calculate the power control output voltage.

[0063] In the description of the present invention, the formula of the active power-frequency control equation is:

[0064]

[0065] In the formula, ω refis the output frequency; J0 is the initial value of the moment of inertia; k is the power feedback coefficient; ΔP is the difference between the grid-side reference power and the grid-side actual power.

[0066] In the description of the present invention, the formula of the reactive power-voltage control equation is:

[0067] u ref =u0+M Q (Q ref -Q e )

[0068] In the formula, u ref is the power control output voltage; u0 is the voltage setting value; Q ref is the reactive power setting value on the grid side; Q e is the grid-side reactive power; M Q is the reactive voltage regulation coefficient.

[0069] S13, using a double closed-loop control converter to decouple the output voltage and the inductor current, and calculating the control amount of the output voltage and current as a modulation signal through parameter calculation of the double closed-loop controller.

[0070] In the description of the present invention, the feedforward decoupling of the output voltage and the inductor current of the converter is controlled by a double closed-loop control, and the control amount of the output voltage and current is calculated as a modulation signal by the parameter calculation of the double closed-loop controller, including the following steps:

[0071] S131. Use the output of the voltage outer loop as the current given value of the current inner loop, obtain the proportional parameter and integral parameter of the voltage outer loop proportional-differential controller, and the component of the power control output voltage in the DC coordinate system, establish the voltage control equation, and calculate the current inner loop given value.

[0072] In the description of the present invention, the calculation formula of the voltage control equation is:

[0073]

[0074] In the formula, i dref is the component of the current inner loop given value on the d-axis; i qref K is the component of the current inner loop given value on the q axis; vp K is the proportional parameter of the voltage outer loop proportional-differential controller; vl is the integral parameter of the voltage outer loop proportional-differential controller; u dref is the power control output voltage u ref The component below the d axis; u qref is the power control output voltage u ref The component below the q axis; u cd u is the component of the d-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; cqis the component of the q-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; C f is the three-phase filter capacitor; ω ref is the power control output frequency; s is the Laplace operator.

[0075] S132. Control the converter output voltage through the voltage outer loop, control the inductor current through the current inner loop, convert the three-phase current and three-phase voltage on the grid side to the DC coordinate system through the three-phase coordinate system, obtain the proportional parameter and integral parameter of the current inner loop proportional-differential controller, combine the current given value of the current inner loop, establish the dual closed-loop controller output formula, and calculate the dual closed-loop controller output.

[0076] In the description of the present invention, the output formula of the dual closed-loop controller is:

[0077]

[0078] In the formula, v d is the component of the double closed-loop controller output on the d-axis; v q is the component of the double closed-loop controller output on the q axis; K ip K is the proportional parameter of the current inner loop proportional-differential controller; il is the integral parameter of the current inner loop proportional-differential controller; i dref is the component of the current inner loop given value on the d-axis; i qref is the component of the current inner loop given value on the q axis; i Ld is the component of the three-phase current on the grid side transformed from the three-phase coordinate system to the d-axis component in the DC coordinate system; i Lq u is the component of the three-phase current on the grid side transformed from the three-phase coordinate system to the q-axis component in the DC coordinate system; cd u is the component of the d-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; cq is the component of the q-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; L f is the three-phase filter inductance; ω ref is the power control output frequency; s is the Laplace operator.

[0079] S2. Based on the coordinate system conversion of the voltage and current values, the modulation signal in the DC coordinate system is converted into a modulation signal in the static coordinate system, and based on the signal modulation algorithm, the modulation signal is converted into a trigger signal of the switch tube to execute the trigger control of the switch tube in each sub-circuit in the converter circuit.

[0080] In the description of the present invention, based on the coordinate system conversion of the voltage and current values, the modulation signal in the DC coordinate system is converted into the modulation signal in the static coordinate system, and based on the signal modulation algorithm, the modulation signal is converted into the trigger signal of the switch tube, and the trigger control of the switch tube in each sub-circuit in the converter circuit is executed, including the following steps:

[0081] S21. Using the inverse Park transform, construct an inverse transform formula of the modulation signal, and convert the modulation signal of the converter circuit in the DC coordinate system into a modulation signal in the static coordinate system.

[0082] S22. Based on the space vector pulse width modulation technology, the modulation signal after the coordinate system conversion is processed, and the modulation signal is converted into a trigger signal of each switch tube in the matrix converter.

[0083] S23. Based on the pulse width modulation technology, the modulation signal after the coordinate system conversion is processed, and the modulation signal is converted into a trigger signal of each switch tube in the full-bridge circuit.

[0084] S3. Obtain the DC side current of the converter circuit, perform dual current coordinated control by introducing a reference current, calculate the phase shift angle between the primary and secondary voltages of the high-frequency transformer, and then feed the phase shift angle variable back to the signal modulation algorithm for coordinated control to adjust the transmission power in the converter.

[0085] In the description of the present invention, the DC side current of the converter circuit is obtained, a reference current is introduced, dual current coordinated control is performed, the phase shift angle between the primary and secondary voltages of the high-frequency transformer is calculated, and the phase shift angle variable is fed back to the signal modulation algorithm for coordinated control. The transmission power in the converter is adjusted, and the following steps are included:

[0086] S31. Obtain the square wave amplitudes of the input and output voltages of the high-frequency transformer, set the primary side voltage and the secondary side voltage to have periodic waveforms, and calculate the ideal current during the phase shift of the high-frequency transformer.

[0087] S32. The ideal current is combined with the energy storage side voltage, the phase shift angle between the primary voltage and the secondary voltage of the high-frequency transformer, the transmission power between the primary side voltage and the secondary side voltage is calculated, and the transmission loss is ignored, and the transmission power is set to the actual power on the grid side.

[0088] S33. The phase shift angle calculation formula is obtained by converting the ideal current and the actual power on the grid side, and the reference phase shift angle is obtained by closed-loop control of the DC side current. The reference phase shift angle variable is then introduced into the space vector pulse width modulation technology and the pulse width modulation technology, and the triggering time of the matrix converter switch tube and the triggering time of the full-bridge circuit switch tube are maintained at the reference phase shift angle to control the transmission power in the converter.

[0089] In the description of the present invention, the calculation formula of the reference phase shift angle is:

[0090]

[0091] In the formula, K is the reference phase shift angle between the primary side voltage and the secondary side voltage of the high frequency transformer; idcp is the proportional parameter of the proportional-derivative controller in cooperative control; K idcl is the integral parameter of the proportional-derivative controller in cooperative control; i dc is the DC side current; i dc * is the DC side current reference value.

[0092] See also Figure 2 , and also provides a grid-type energy storage inverter control system, which includes: an inverter circuit, a power control module, a dual closed-loop control module, a collaborative control module, a pulse width modulation module, a space vector pulse width modulation module and a coordinate system transformation module.

[0093] Among them, the converter circuit is used to build the circuit structure of the grid-type energy storage converter to realize energy transmission and conversion, including a DC energy storage link, a DC side filter circuit, a full-bridge circuit, a high-frequency transformer, a matrix converter, an AC side filter circuit and a grid side circuit.

[0094] The power control module is used to sample the grid-side voltage and current in real time, calculate the active power and reactive power of the converter, and control the output voltage of the converter grid-side.

[0095] The dual closed-loop control module is used to control the inductor current in the converter by using the current inner loop and to control the converter output voltage by using the voltage outer loop, thereby improving the anti-interference ability of the converter.

[0096] The collaborative control module is used to collaboratively control the DC side and AC side of the converter, adjust the phase shift angle between the primary and secondary sides of the high-frequency transformer, and regulate the transmission power of the converter.

[0097] The pulse width modulation module is used to generate a trigger signal for controlling the switch tube in the matrix converter.

[0098] The space vector pulse width modulation module is used to generate a trigger signal for controlling the switch tube in the full-bridge circuit.

[0099] The coordinate system transformation module is used to transform signals between different coordinate systems.

[0100] The following describes in detail a grid-type energy storage converter control system and a grid-type energy storage converter control method in conjunction with the accompanying drawings and specific embodiments.

[0101] like Figure 2As shown, the grid-type energy storage converter control system includes a converter circuit and related control modules. First, the grid-type energy storage converter circuit includes a DC energy storage link, a DC side filter circuit, a full-bridge circuit, a high-frequency transformer, a matrix converter, an AC side filter circuit and a grid side circuit.

[0102] Among them, the DC energy storage link is a DC power supply, whose positive electrode is connected to the inductor L d , the negative electrode is connected to the capacitor C d ; The DC side filter circuit includes a filter inductor L d And filter capacitor C d The full-bridge circuit includes four switch tubes Q1 to Q4, which converts the DC current u dc Convert to high frequency AC p ; The high-frequency transformer includes two leakage inductors L k and transformer T r , which converts the primary side high frequency AC current u p Transmitted to the secondary side, converted into voltage u s The matrix converter consists of three-phase bridge arms, both ends of which are connected to the two sides of the high-frequency transformer, and the midpoints of the bridge arms are connected to the three-phase AC filter circuits. Each bridge arm is divided into two upper and lower half bridge arms, and each half bridge arm consists of a group of bidirectional switches. The matrix converter includes 12 switch tubes S ah1 To S cn2 , which converts high frequency alternating current u s Converted to three-phase industrial frequency AC power; the AC side filter circuit includes a three-phase filter inductor L f And three-phase filter capacitor C f ; The grid side circuit includes the grid impedance R g , grid inductive reactance L g and power supply (u ga ,u ga ,u gc ).

[0103] In addition, in order to realize the control method of grid-type energy storage converter, such as Figure 2 As shown, in addition to the converter circuit, a power control module, a dual closed-loop control module, a cooperative control module, a PWM (pulse width modulation module) and a SVPWM modulation module (space vector pulse width modulation module) and a coordinate system transformation module are additionally provided.

[0104] The control method performs power control by sampling the grid-side voltage and current to obtain the grid-side reference voltage and reference angular frequency; obtains the modulation signal in the dq coordinate system (DC coordinate system) through double closed-loop control of the obtained reference quantity and the grid-side sampling signal; obtains the signal in the αβ coordinate system (static coordinate system) after coordinate transformation of the modulation signal, and obtains the trigger signal of each switch tube of the matrix converter through SVPWM modulation (space vector pulse width modulation technology); generates the trigger signal of each switch tube of the full-bridge circuit through PWM modulation (pulse width modulation technology); samples the DC side current and adds the reference current, obtains the phase shift angle between the primary and secondary side voltages of the high-frequency transformer through coordinated control, and acts on PWM and SVPWM modulation for coordinated control.

[0105] In one embodiment, Figure 3 As shown, the power control is performed by sampling the three-phase voltage u on the grid-side filter capacitor. c and the three-phase current i flowing through the grid-side filter inductor L , calculate the actual grid-side power P e , set the grid-side reference power P ref , the active power-frequency control equation can be listed as:

[0106]

[0107]

[0108] Among them, ω0 is the frequency setting value, ω ref is the output frequency, J is the moment of inertia, J0 is the initial value of the moment of inertia, D is the damping coefficient, and k is the power feedback coefficient;

[0109] Combining equations (1) and (2), ignoring the damping coefficient, the active power-frequency control equation can be expressed as:

[0110]

[0111] Where ΔP = P ref -P e , when power regulation is introduced into the control, the rate of change of the converter output frequency is limited, and the following relationship can be further obtained:

[0112]

[0113] The reactive power-voltage control equation in power control is:

[0114] u ref =u0+M Q (Q ref -Q e ) (5)

[0115] Among them, u0 is the voltage setting value, u ref is the output voltage, Q ref is the grid-side reactive power setting value, Q e is the grid-side reactive power, M Q is the reactive voltage regulation coefficient.

[0116] In one embodiment, Figure 4 As shown, the double closed-loop control includes a voltage outer loop and a current inner loop, where the voltage outer loop is a control loop for the converter output voltage u c The inner current loop is used to control the inductor current i L Control is performed to feedforward decouple the converter output voltage and inductor current, and the following formula can be obtained:

[0117]

[0118] Among them, v d and v q is the output of the double closed-loop controller, K ip and K il are the proportional and integral parameters of the current inner loop PI controller, i dref and i dref is the given value of the current inner loop, i Ld 、i Lq 、u cd and u cq It is the quantity of grid-side current and voltage transformed from abc coordinate system (three-phase coordinate system) to dq coordinate system;

[0119] Taking the output of the voltage outer loop as the given of the current inner loop, the voltage control equation can be obtained:

[0120]

[0121] Among them, K vp and K vl are the proportional and integral parameters of the voltage outer loop PI controller, u dref and u dref is the output voltage u in power control ref The component under the dq coordinate axis.

[0122] In one embodiment, Figure 5 As shown, at this time, the power flows from the energy storage DC side to the grid AC side, which requires the transformer secondary side voltage u s The primary voltage of the lagging transformer u p , and the full-bridge circuit controls the primary voltage of the transformer, and the matrix converter controls the secondary voltage of the transformer, so by delaying the trigger time of the matrix converter switch tube to the trigger time of the full-bridge circuit switch tube Angle, that is, the transformer secondary voltage lags behind the transformer primary voltage The angle is adjusted to achieve the effect of adjusting the transmission power. Cooperative control takes into account that the square wave amplitude of the input and output voltages of the high-frequency transformer is the same. Assuming that the primary side voltage u p and the secondary voltage u s If there is a periodic waveform, the ideal current can be calculated during the phase shift:

[0123]

[0124] Among them, i p is the primary current of the high-frequency transformer, is the phase shift angle between the primary and secondary voltages of the high-frequency transformer, T s is the switching period, u dc is the voltage on the energy storage side, I is the ideal current value, at the end of the phase shift angle (i.e. ), the ideal current can be expressed as follows:

[0125]

[0126] The transmission power expression is as follows:

[0127]

[0128] Among them, P t is the transmitted power, when losses are neglected:

[0129] P e =P t (11)

[0130] The phase shift angle expression can be obtained by equations (9), (10) and (11):

[0131]

[0132] Collaborative control Figure 6 As shown in the figure, since power can flow in both directions, the phase shift angle has two values. The reference phase shift angle can be obtained by closed-loop control of the DC side current:

[0133]

[0134] Among them, K idcp and K idcl are the proportional and integral parameters of the PI controller in the collaborative control, i dc is the DC side current, i dc *The phase shift angle variable is obtained by controlling the DC side current and introducing it into PWM and SVPWM modulation to keep the trigger time of the matrix converter switch tube and the trigger time of the full-bridge circuit switch tube. Angle, thereby achieving the effect of adjusting the transmission power.

[0135] In one embodiment, the coordinate system transformation module includes two parts: transformation from the abc coordinate system to the dq coordinate system and transformation from the dq coordinate system to the αβ coordinate system. The transformation from the abc coordinate system to the dq coordinate system adopts Clark transformation, and the transformation from the dq coordinate system to the αβ coordinate system adopts Park inverse transformation. L and the output voltage u c The Clark transforms of are respectively equations (13) and (14), and the Park inverse transform of the modulated signal is equation (15).

[0136]

[0137]

[0138]

[0139] In the formula, i La ,i Lb ,i Lc and u ca ,u cb ,u cc They are the inductor current i L and the output voltage u c The quantity of each phase in the three phases, θ is the angle output by the power control module.

[0140] In summary, with the help of the above technical solution of the present invention, by obtaining the grid-side sampling signal and calculating the reference quantity, it is ensured that the output of the converter is synchronized with the grid, which helps to optimize power transmission and reduce harmonic pollution; the modulation signal in the DC coordinate system is converted into a signal in the static coordinate system, and the trigger signal of each switch tube is generated, so as to realize efficient inverter control, which not only improves the control accuracy of the converter, but also enhances the anti-interference ability of the system; in addition, by sampling the DC side current and combining the current reference quantity, the phase shift angle between the primary side and the secondary side of the high-frequency transformer is calculated, and the energy conversion efficiency of the system is further optimized. The present invention can simultaneously control the AC side and the DC side of the converter, overcomes the limitation that the traditional three-phase-single-phase matrix converter type energy storage converter cannot be controlled by the grid, greatly improves the flexibility and adaptability of the system, and is suitable for different grid conditions and load requirements; not only improves the energy management efficiency of the converter, but also enhances the stability of the power system, provides higher energy quality, promotes the effective use of renewable energy, and provides reliable technical support for the construction of smart grids.

[0141] It should be understood that, although the steps in the flowchart of the accompanying drawings are displayed in sequence as indicated by the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least a part of the steps in the flowchart of the accompanying drawings may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn or alternately with other steps or at least a part of the sub-steps or stages of other steps.

Claims

1. A control method for a grid-type energy storage converter, characterized in that: The method comprises the following steps: S1, obtaining sampling signals of voltage and current on the grid side of the converter circuit, performing grid side power control by extracting three-phase voltage and three-phase current, calculating grid side reference voltage and reference angular frequency, and generating modulation signals in a DC coordinate system by double closed-loop control of the sampling signal and the reference quantity; S2. Based on the coordinate system conversion of the voltage and current values, the modulation signal in the DC coordinate system is converted into the modulation signal in the static coordinate system, and based on the signal modulation algorithm, the modulation signal is converted into a trigger signal of the switch tube, and the trigger control of the switch tube in each sub-circuit in the converter circuit is executed; S3. Obtain the DC side current of the converter circuit, perform dual current coordinated control by introducing a reference current, calculate the phase shift angle between the primary and secondary voltages of the high-frequency transformer, and then feed the phase shift angle variable back to the signal modulation algorithm for coordinated control to adjust the transmission power in the converter.

2. A grid-type energy storage converter control method according to claim 1, characterized in that: The method of obtaining the sampling signal of the voltage and current on the grid side of the converter circuit, extracting the three-phase voltage and the three-phase current, performing grid-side power control, calculating the grid-side reference voltage and the reference angular frequency, and generating a modulation signal in a DC coordinate system through double closed-loop control of the sampling signal and the reference quantity comprises the following steps: S11, collecting the three-phase voltage on the three-phase filter capacitor and the three-phase current flowing through the three-phase filter inductor in the AC side filter circuit as the sampling signal on the grid side; S12, using the three-phase voltage and the three-phase current to calculate the actual power on the grid side, by setting the grid side reference power, moment of inertia and damping coefficient, establishing an active-frequency control equation, and introducing power regulation into the control, limiting the output frequency of the converter, generating a reactive-voltage control equation, and calculating the power control output voltage; S13, using a double closed-loop control converter to decouple the output voltage and the inductor current, and calculating the control amount of the output voltage and current as a modulation signal through parameter calculation of the double closed-loop controller.

3. A grid-type energy storage converter control method according to claim 2, characterized in that: The formula of the active power-frequency control equation is: In the formula, ω ref is the output frequency; J0 is the initial value of the moment of inertia; k is the power feedback coefficient; ΔP is the difference between the grid-side reference power and the grid-side actual power.

4. A grid-type energy storage converter control method according to claim 2, characterized in that: The formula of the reactive power-voltage control equation is: u ref =u0+M Q (Q ref -Q e ) In the formula, u ref Output voltage for power control; u0 is the voltage setting value; Q ref It is the reactive power setting value on the grid side; Q e Reactive power on the grid side; M Q is the reactive voltage regulation coefficient.

5. A grid-type energy storage converter control method according to claim 2, characterized in that: The method of utilizing a double closed-loop control to decouple the output voltage of the converter from the feedforward of the inductor current and calculating the control amount of the output voltage and current as a modulation signal through parameter calculation of the double closed-loop controller comprises the following steps: S131, using the output of the voltage outer loop as the current given value of the current inner loop, obtaining the proportional parameter and integral parameter of the voltage outer loop proportional-differential controller, and the component of the power control output voltage in the DC coordinate system, establishing the voltage control equation, and calculating the current inner loop given value; S132. Control the converter output voltage through the voltage outer loop, control the inductor current through the current inner loop, convert the three-phase current and three-phase voltage on the grid side to the DC coordinate system through the three-phase coordinate system, obtain the proportional parameter and integral parameter of the current inner loop proportional-differential controller, combine the current given value of the current inner loop, establish the dual closed-loop controller output formula, and calculate the dual closed-loop controller output.

6. A grid-type energy storage converter control method according to claim 5, characterized in that: The calculation formula of the voltage control equation is: In the formula, i dref is the component of the current inner loop given value on the d-axis; i qref is the component of the current inner loop given value on the q axis; K vp is the proportional parameter of the voltage outer loop proportional-differential controller; K vl is the integral parameter of the voltage outer loop proportional-differential controller; u dref is the power control output voltage u ref The component below the d axis; u qref is the power control output voltage u ref The component below the q axis; u cd It is the component of the d-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; u cq It is the component of the q-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; C f It is a three-phase filter capacitor; ω ref Output frequency for power control; s is the Laplace operator.

7. A grid-type energy storage converter control method according to claim 5, characterized in that: The output formula of the dual closed-loop controller is: In the formula, v d is the component of the double closed-loop controller output on the d-axis; v q is the component of the double closed-loop controller output on the q axis; K ip is the proportional parameter of the current inner loop proportional-differential controller; K il is the integral parameter of the current inner loop proportional-differential controller; i dref is the component of the current inner loop given value on the d-axis; i qref is the component of the current inner loop given value on the q axis; i Ld It is the component of the three-phase current on the grid side transformed from the three-phase coordinate system to the d-axis component in the DC coordinate system; i Lq It is the component of the q-axis of the three-phase current on the grid side transformed from the three-phase coordinate system to the DC coordinate system; u cd It is the component of the d-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; u cq It is the component of the q-axis of the three-phase voltage on the grid side transformed from the three-phase coordinate system to the DC coordinate system; L f is the three-phase filter inductor; ω ref Output frequency for power control; s is the Laplace operator.

8. A grid-type energy storage converter control method according to claim 2, characterized in that: The coordinate system conversion based on the voltage and current numerical values ​​converts the modulation signal in the DC coordinate system into the modulation signal in the static coordinate system, and based on the signal modulation algorithm, converts the modulation signal into a trigger signal of the switch tube, and executes the trigger control of the switch tube in each sub-circuit in the converter circuit, including the following steps: S21, using inverse Park transform to construct an inverse transform formula of the modulation signal, and converting the modulation signal of the converter circuit in the DC coordinate system into a modulation signal in the static coordinate system; S22, based on the space vector pulse width modulation technology, processing the modulation signal after the coordinate system conversion, and converting the modulation signal into a trigger signal of each switch tube in the matrix converter; S23. Based on the pulse width modulation technology, the modulation signal after the coordinate system conversion is processed, and the modulation signal is converted into a trigger signal of each switch tube in the full-bridge circuit.

9. A grid-type energy storage converter control method according to claim 8, characterized in that: The method of obtaining the DC side current of the converter circuit, introducing a reference current, performing dual current coordinated control, calculating the phase shift angle between the primary and secondary voltages of the high-frequency transformer, and then feeding back the phase shift angle variable to the signal modulation algorithm for coordinated control, and adjusting the transmission power in the converter includes the following steps: S31, obtaining the square wave amplitude of the input and output voltages of the high-frequency transformer, setting the primary side voltage and the secondary side voltage to have periodic waveforms, and calculating the ideal current during the phase shift period of the high-frequency transformer; S32, combining the ideal current with the energy storage side voltage, the phase shift angle between the primary voltage and the secondary voltage of the high-frequency transformer, calculating the transmission power between the primary side voltage and the secondary side voltage, ignoring the transmission loss, and setting the transmission power to the actual power on the grid side; S33. The phase shift angle calculation formula is obtained by converting the formula of the ideal current and the actual power on the grid side, and the reference phase shift angle is obtained by closed-loop control of the DC side current. The reference phase shift angle variable is then introduced into the space vector pulse width modulation technology and the pulse width modulation technology, and the triggering time of the matrix converter switch tube and the triggering time of the full-bridge circuit switch tube are kept at the reference phase shift angle to control the transmission power in the converter, wherein the calculation formula of the reference phase shift angle is: In the formula, is the reference phase shift angle between the primary side voltage and the secondary side voltage of the high frequency transformer; K idcp is the proportional parameter of the proportional-derivative controller in cooperative control; K idcl is the integral parameter of the proportional-derivative controller in cooperative control; i dc is the DC side current; i dc * is the DC side current reference value.

10. A grid-type energy storage converter control system, used to implement the grid-type energy storage converter control method according to any one of claims 1 to 9, characterized in that: The system includes: a converter circuit, a power control module, a dual closed-loop control module, a coordinated control module, a pulse width modulation module, a space vector pulse width modulation module and a coordinate system transformation module; The converter circuit is used to construct a circuit structure of a grid-type energy storage converter to achieve energy transmission and conversion, including a DC energy storage link, a DC side filter circuit, a full-bridge circuit, a high-frequency transformer, a matrix converter, an AC side filter circuit and a grid side circuit; The power control module is used to sample the grid-side voltage and current in real time, calculate the active power and reactive power of the converter, and control the output voltage of the converter grid side; The dual closed-loop control module is used to control the inductor current in the converter by using the current inner loop and control the output voltage of the converter by using the voltage outer loop, thereby improving the anti-interference ability of the converter; The collaborative control module is used to collaboratively control the DC side and the AC side of the converter, adjust the phase shift angle between the primary side and the secondary side of the high-frequency transformer, and regulate the transmission power of the converter; The pulse width modulation module is used to generate a trigger signal for controlling the switch tube in the matrix converter; The space vector pulse width modulation module is used to generate a trigger signal for controlling the switch tube in the full-bridge circuit; The coordinate system transformation module is used for performing signal transformation between different coordinate systems.

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