Photovoltaic and hybrid energy storage power generation system multi-working-condition optimization control method

Abstract

The invention relates to a multi-working-condition optimization control method for a photovoltaic and hybrid energy storage power generation system. The method comprises the following steps: controlling a grid connection strategy of the photovoltaic and hybrid energy storage power generation system according to an operation working condition; when the photovoltaic and hybrid energy storage power generation system is in a normal grid-connected state, the DC-AC grid-connected inverter adopts DC constant-voltage double-loop control, and the first bidirectional DC-DC converter and the second bidirectional DC-DC converter adopt constant-current control; when the photovoltaic and hybrid energy storage power generation system is in a low-voltage ride-through state, the DC-AC grid-connected inverter adopts single current loop control, the first bidirectional DC-DC converter adopts constant current control, and the second bidirectional DC-DC converter adopts constant voltage control; when the photovoltaic and hybrid energy storage power generation system is in isolated island operation, the DC-AC grid-connected inverter adopts V-f control, the first bidirectional DC-DC converter adopts constant voltage control, and the second bidirectional DC-DC converter adopts constant current control. Different control methods are adopted under different working conditions, stable support of the photovoltaic and hybrid energy storage power generation system to the power grid is achieved, and the service life of energy storage equipment is prolonged.

Description

Technical Field

[0001] The invention relates to a multi-operating condition optimization control method for a photovoltaic and hybrid energy storage power generation system, and belongs to the technical field of photovoltaic energy storage power generation system control. Background Art

[0002] With the transformation of the global energy structure and the vigorous promotion of renewable energy, photovoltaic power generation, as a clean and sustainable form of energy, has received widespread attention and application. However, photovoltaic power generation systems still face a series of technical challenges in actual operation. The grid-connected stability of photovoltaic power generation systems is the key to their large-scale application. Due to the intermittent and unstable nature of solar energy, the output power of photovoltaic power generation systems fluctuates with changing weather conditions, which poses a challenge to the stability of the power grid. Especially when the grid voltage drops, the low voltage ride-through capability of photovoltaic power stations is reduced, which may lead to grid disconnection and increase the risk of grid operation. In order to ensure the continuity and stability of photovoltaic power generation, the application of energy storage technology is particularly important. At present, chemical battery energy storage is a more common choice. Chemical battery energy storage has the advantages of flexible capacity and power design, high energy conversion efficiency, and high energy density. It plays an important role in the application of large-scale energy storage systems, but its power density is small, and the charging and discharging speed and number are limited, which cannot meet the needs of fast dynamic power compensation. As a new type of energy storage technology, supercapacitors have great potential in photovoltaic power generation and energy storage systems with their advantages of fast charging and discharging capabilities, high cycle life and maintenance-free.

[0003] At present, there are many studies on using energy storage technology to improve the stability of photovoltaic power generation systems. Xu Shaohua proposed a voltage management control strategy based on chemical energy storage in "Grid-connected / Islanded Operation Control Strategy of Photovoltaic Storage Microgrid System" (Proceedings of the Chinese Society of Electrical Engineering, 2013, 33(34)). The control method of chemical battery energy storage is switched to meet the system stability requirements. The PQ control strategy is used to maintain the bus voltage stability at the PCC point during grid-connected operation, and Vf control is used to ensure the stability of the system voltage and frequency during islanded operation. However, chemical battery energy storage belongs to energy storage. Its high energy density and power supply stability make it more suitable for application scenarios that require long-term and stable power supply. In some occasions that require fast response and short-term high-power output, such as low voltage ride-through, all short-term fluctuations in a single chemical battery energy storage system must be smoothed by chemical battery energy storage, which is not conducive to maintaining the life of the chemical battery.

[0004] Liu Yaoyuan proposed a photovoltaic grid-connected low voltage ride-through control strategy based on supercapacitor energy storage in "Research on Photovoltaic Grid-Connected Low Voltage Ride-Through Control Strategy Based on Supercapacitor" (Power System Protection and Control, 2014, 42(13)). By controlling the supercapacitor to absorb the unbalanced power generated by the photovoltaic power generation system during low voltage ride-through, the DC bus voltage is balanced, the power injected into the inverter by the photovoltaic array is reduced, and the inverter is prevented from overcurrent. However, supercapacitor energy storage is a power-type energy storage with a low energy density. When the system requires more sustained power support, chemical battery energy storage is more suitable. Summary of the invention

[0005] In order to overcome the above problems, the present invention provides a multi-operating condition optimization control method for a photovoltaic and hybrid energy storage power generation system.

[0006] The technical solution of the present invention is as follows:

[0007] A multi-operating condition optimization control method for a photovoltaic and hybrid energy storage power generation system is provided, wherein the photovoltaic and hybrid energy storage power generation system comprises a photovoltaic unit, a chemical battery energy storage unit and a super capacitor energy storage unit, wherein the photovoltaic unit is connected to a DC bus through a Boost converter, wherein the chemical battery energy storage unit and the super capacitor energy storage unit are connected to the DC bus through a first bidirectional DC-DC converter and a second bidirectional DC-DC converter respectively, and the DC bus is connected to a power grid through a DC-AC grid-connected inverter, and the method comprises the following steps:

[0008] Acquire grid operation mode data, determine the operation condition of the photovoltaic and hybrid energy storage power generation system according to the grid operation mode data, and control the grid connection strategy of the photovoltaic and hybrid energy storage power generation system according to the operation condition, wherein the grid connection strategy includes normal grid connection, low voltage ride-through and island operation;

[0009] The Boost converter adopts MPPT control;

[0010] When the photovoltaic and hybrid energy storage power generation system is in a normal grid-connected state, the DC-AC grid-connected inverter adopts a DC constant voltage dual-loop control, and the first bidirectional DC-DC converter and the second bidirectional DC-DC converter both adopt a constant current control;

[0011] When the photovoltaic and hybrid energy storage power generation system is in low voltage ride-through, the DC-AC grid-connected inverter adopts single current loop control, the first bidirectional DC-DC converter adopts constant current control, and the second bidirectional DC-DC converter adopts constant voltage control;

[0012] When the photovoltaic and hybrid energy storage power generation system is in island operation, the DC-AC grid-connected inverter adopts Vf control, the first bidirectional DC-DC converter adopts constant voltage control, and the second bidirectional DC-DC converter adopts constant current control.

[0013] Furthermore, the grid operation mode data is time series data of grid voltage;

[0014] The operation condition of the photovoltaic and hybrid energy storage power generation system is determined according to the grid operation mode data, and the grid connection strategy of the photovoltaic and hybrid energy storage power generation system is controlled according to the operation condition, specifically:

[0015] When the photovoltaic and hybrid energy storage power generation system is in a normal grid-connected state, it is determined whether the grid has experienced a voltage drop caused by a disturbance or fault based on the grid operation mode data;

[0016] If the voltage drop caused by both disturbance and fault occurs, the photovoltaic and hybrid energy storage power generation system is connected to the grid in normal operation;

[0017] If a voltage drop occurs due to a disturbance or fault, the photovoltaic and hybrid energy storage power generation system is operated in a low voltage ride-through state;

[0018] When the photovoltaic and hybrid energy storage power generation system is in the low voltage ride-through state, the execution state of the low voltage ride-through is determined according to the grid operation mode data;

[0019] If the low voltage ride-through is completed, the photovoltaic and hybrid energy storage power generation systems will be connected to the grid as normal;

[0020] If the low voltage ride-through is not completed, the photovoltaic and hybrid energy storage power generation system is allowed to maintain the low voltage ride-through state;

[0021] If the low voltage ride through fails, the photovoltaic and hybrid energy storage power generation system is operated in an island operation state;

[0022] When the photovoltaic and hybrid energy storage power generation system is in an island operation state, it is determined whether the grid has voltage drops caused by disturbances or faults based on the grid operation mode data;

[0023] If no voltage drop caused by disturbance or fault occurs, the photovoltaic and hybrid energy storage power generation system is connected to the grid in normal operation;

[0024] If a voltage drop occurs due to a disturbance or a fault, the photovoltaic and hybrid energy storage power generation system is kept operating in an island operation state.

[0025] Furthermore, the Boost converter adopts MPPT control, specifically:

[0026] Get the output voltage U of the photovoltaic unitPV and output current I PV ;

[0027] The output voltage U is adjusted by the MPPT algorithm. PV and output current I PV Processing is performed to obtain the photovoltaic voltage command value U PV-ref ;

[0028] The output voltage U of the photovoltaic cell PV With the photovoltaic voltage command value U PV-ref The error is input into the PI controller of the Boost converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal;

[0029] The switch tube of the Boost converter is driven according to the driving signal to adjust the duty cycle of the Boost converter.

[0030] Furthermore, the DC-AC grid-connected inverter adopts a DC constant voltage dual-loop control, specifically:

[0031] Get the DC bus voltage U dc and reference voltage U dc-ref ;

[0032] The DC bus voltage U dc With reference voltage U dc-ref The error is input into the PI controller of the DC-AC grid-connected inverter, and the output of the PI controller is used as the d-axis component command value i of the inductor current. Ld-ref ;

[0033] Obtain the inductor current i of the DC-AC grid-connected inverter Labc and grid voltage phase θ;

[0034] The inductor current i of the DC-AC grid-connected inverter Labc and the grid voltage phase θ are input into the coordinate transformation module abc / dq0 to obtain the d-axis component i of the inductor current of the DC-AC grid-connected inverter Ld and the q-axis component i Lq ;

[0035] The d-axis component i Ld The d-axis component command value i Ld-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the modulation wave d-axis component u md ;

[0036] Get the inductor current q-axis component command value i Lq-ref ;

[0037] The q-axis component i Lq The q-axis component command value i Lq-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the modulation wave q-axis component u mq ;

[0038] The modulated wave d-axis component u md , the modulated wave q-axis component u mq and the grid voltage phase θ are input into the coordinate transformation module dq0 / abc to obtain the PWM modulation wave u mabc ;

[0039] After the PWM modulation wave is subjected to pulse width modulation, a driving signal is obtained;

[0040] The switch tube of the DC-AC grid-connected inverter is driven according to the driving signal.

[0041] Furthermore, the first bidirectional DC-DC converter adopts constant current control, specifically:

[0042] Get the charging current reference value I of chemical battery energy storage bat-ref and charging current I bat ;

[0043] The charging current I bat With the charging current reference value I bat-ref The error is input into the PI controller of the first bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal;

[0044] The switch tube of the first bidirectional DC-DC converter is driven according to the driving signal, so that the chemical battery energy storage is in a constant current charging state.

[0045] Furthermore, the second bidirectional DC-DC converter adopts constant current control, specifically:

[0046] Get the charging current reference value I of the supercapacitor energy storage sc-ref and charging current I sc ;

[0047] The charging current I sc With the charging current reference value I sc-ref The error is input into the PI controller of the second bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal;

[0048] The switch tube of the second bidirectional DC-DC converter is driven according to the driving signal, so that the supercapacitor energy storage is in a constant current charging state.

[0049] Furthermore, the DC-AC grid-connected inverter adopts single current loop control, specifically:

[0050] Obtain the filter inductor current amplitude I of the DC-AC grid-connected inverter L-lim , the inductor current d-axis component command value i Ld-ref and the inductor current q-axis component command value i Lq-ref ;

[0051] The filter inductor current amplitude I L-lim and the inductor current d-axis component command value i Ld-ref Input limiter, according to the filter inductor current amplitude I L-lim The inductor current d-axis component command value i Ld-ref To limit the clipping;

[0052] The filter inductor current amplitude I L-lim and the inductor current q-axis component command value i Lq-ref Input limiter, according to the filter inductor current amplitude I L-lim The q-axis component command value i of the inductor current is Lq-ref To limit the clipping;

[0053] Obtain the inductor current i of the DC-AC grid-connected inverter Labc and grid voltage phase θ;

[0054] The inductor current i of the DC-AC grid-connected inverter Labc and the grid voltage phase θ are input into the coordinate transformation module abc / dq0 to obtain the d-axis component i of the inductor current of the DC-AC grid-connected inverter Ld and the q-axis component i Lq ;

[0055] The output of A and the d-axis component i Ld The error is input into the PI controller to obtain the modulation wave d-axis component u md ;

[0056] The output of A and the q-axis component i Lq The error is input into the PI controller to obtain the modulation wave q-axis component u mq ;

[0057] The d-axis component u md , the q-axis component u mq and the grid voltage phase θ are input into the coordinate transformation module dq0 / abc to obtain the PWM modulation wave u mabc ;

[0058] After the PWM modulation wave is subjected to pulse width modulation, a driving signal is obtained;

[0059] The switch tube of the DC-AC grid-connected inverter is driven according to the driving signal.

[0060] Furthermore, the second bidirectional DC-DC converter adopts constant voltage control, specifically:

[0061] Get the DC bus voltage U dc , reference voltage U dc-ref and the charging current I of the supercapacitor energy storage sc ;

[0062] The DC bus voltage U dc With reference voltage U dc-ref The error is input into the PI controller of the second bidirectional DC-DC converter to obtain the charging current reference value I of the supercapacitor energy storage. sc-ref ;

[0063] The charging current I sc and the charging current reference value I sc-ref The error is input into the PI controller of the second bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal;

[0064] The switch tube of the second bidirectional DC-DC converter is driven according to the driving signal, so that the charging power of the supercapacitor energy storage can maintain the constant DC bus voltage.

[0065] Furthermore, the DC-AC grid-connected inverter adopts Vf control, specifically:

[0066] Get the DC-AC grid-connected inverter output voltage U abc , output voltage command value U abc-ref and grid voltage phase θ;

[0067] The output voltage U abc The grid voltage phase θ is input into the coordinate transformation module abc / dq0 to obtain the d-axis component U of the DC-AC grid-connected inverter output voltage. d and the q-axis component U q ;

[0068] The output voltage command value U abc-ref The grid voltage phase θ is input into the coordinate transformation module abc / dq0 to obtain the d-axis component U of the DC-AC grid-connected inverter output voltage command value. d-ref and the q-axis component U q-ref ;;

[0069] The d-axis component U d and the d-axis component U d-refThe error is input into the PI controller of the DC-AC grid-connected inverter to obtain the d-axis component command value i of the inductor current Ld-ref ;

[0070] The q-axis component U q With the q-axis component U q-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the q-axis component command value i of the inductor current Lq-ref ;

[0071] Get the inductor current i of the DC-AC grid-connected inverter Labc ;

[0072] The inductor current i Labc and the grid voltage phase θ are input into the coordinate transformation module abc / dq0 to obtain the d-axis component i of the inductor current of the DC-AC grid-connected inverter Ld and the q-axis component i Lq ;

[0073] The d-axis component i Ld and the d-axis component command value i Ld-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the modulation wave d-axis component u md ;

[0074] The q-axis component i Lq and the q-axis component command value i Lq-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the modulation wave q-axis component u mq ;

[0075] The d-axis component u of the modulated wave md , modulation wave q-axis component u mq And the grid voltage phase θ is input into the coordinate transformation module dq0 / abc to obtain the PWM modulation wave u mabc ;

[0076] After the PWM modulation wave is subjected to pulse width modulation, a driving signal is obtained;

[0077] The switch tube of the DC-AC grid-connected inverter is driven according to the driving signal.

[0078] Furthermore, the first bidirectional DC-DC converter adopts constant voltage control, specifically:

[0079] Get the DC bus voltage U dc , reference voltage U dc-ref and the charging current I of chemical battery energy storage bat ;

[0080] The DC bus voltage U dcWith reference voltage U dc-ref The error is input into the PI controller of the first bidirectional DC-DC converter to obtain the charging current reference value I of the chemical battery energy storage bat-ref ;

[0081] The charging current I bat and the charging current reference value I bat-ref The error is input into the PI controller of the first bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal;

[0082] The switch tube of the first bidirectional DC-DC converter is driven according to the driving signal, so that the charging power of the chemical battery energy storage can maintain the constant DC bus voltage.

[0083] The present invention has the following beneficial effects:

[0084] This control method achieves stable support for the power grid, extends the service life of energy storage equipment, and reduces maintenance costs by switching the control modes of photovoltaic DC-DC converters, chemical battery energy storage bidirectional DC-DC converters, supercapacitor energy storage bidirectional DC-DC converters, and DC-AC grid-connected converters under normal grid-connected, low voltage ride-through, and island operation conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 This is the structural diagram of the photovoltaic and hybrid energy storage power generation system.

[0086] Figure 2 This is a flow chart of the photovoltaic and hybrid energy storage power generation system control method of the present invention.

[0087] Figure 3 This is a diagram of the MPPT control structure of a Boost converter according to an embodiment of the present invention.

[0088] Figure 4 This is a DC constant voltage dual-loop control structure diagram of a DC-AC grid-connected inverter according to an embodiment of the present invention.

[0089] Figure 5 This is a constant current control structure diagram of a first bidirectional DC-DC converter according to an embodiment of the present invention.

[0090] Figure 6 This is a constant current control structure diagram of a second bidirectional DC-DC converter according to an embodiment of the present invention.

[0091] Figure 7 1 is a single current loop control structure diagram of a DC-AC grid-connected inverter according to an embodiment of the present invention.

[0092] Figure 84 is a diagram of a constant voltage control structure of a second bidirectional DC-DC converter according to an embodiment of the present invention.

[0093] Fig. 9 4 is a control structure diagram of a DC-AC grid-connected inverter Vf according to an embodiment of the present invention.

[0094] Fig.10 This is a constant voltage control structure diagram of a first bidirectional DC-DC converter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0095] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0096] refer to Figure 1 and 2 A multi-operating condition optimization control method for a photovoltaic and hybrid energy storage power generation system is provided to control the photovoltaic and hybrid energy storage power generation system, wherein the photovoltaic and hybrid energy storage power generation system comprises a photovoltaic unit, a chemical battery energy storage unit and a super capacitor energy storage unit, wherein the photovoltaic unit is connected to a DC bus through a Boost converter, wherein the chemical battery energy storage unit and the super capacitor energy storage unit are connected to the DC bus through a first bidirectional DC-DC converter and a second bidirectional DC-DC converter respectively, and the DC bus is connected to a power grid through a DC-AC grid-connected inverter, and comprises the following steps:

[0097] Acquire grid operation mode data, determine the operation condition of the photovoltaic and hybrid energy storage power generation system according to the grid operation mode data, and control the grid connection strategy of the photovoltaic and hybrid energy storage power generation system according to the operation condition, wherein the grid connection strategy includes normal grid connection, low voltage ride-through and island operation;

[0098] The Boost converter adopts MPPT control;

[0099] When the photovoltaic and hybrid energy storage power generation system is in a normal grid-connected state, the DC-AC grid-connected inverter adopts a DC constant voltage dual-loop control, and the first bidirectional DC-DC converter and the second bidirectional DC-DC converter both adopt a constant current control;

[0100] When the photovoltaic and hybrid energy storage power generation system is in low voltage ride-through, the DC-AC grid-connected inverter adopts single current loop control, the first bidirectional DC-DC converter adopts constant current control, and the second bidirectional DC-DC converter adopts constant voltage control;

[0101] When the photovoltaic and hybrid energy storage power generation system is in island operation, the DC-AC grid-connected inverter adopts Vf control, the first bidirectional DC-DC converter adopts constant voltage control, and the second bidirectional DC-DC converter adopts constant current control.

[0102] The photovoltaic boost converter adopts MPPT control to achieve the maximum power output of the photovoltaic array.

[0103] In the normal grid-connected state, the photovoltaic power generation system generates electricity normally and stores the excess electricity in the battery energy storage device to maintain its SOC level at the set value. At this time, the supercapacitor is in standby mode.

[0104] In the low voltage ride-through state, the supercapacitor quickly releases the stored electric energy to assist the photovoltaic power generation system in low voltage ride-through. Due to the high power density and fast charge and discharge characteristics of the supercapacitor, it can quickly provide the required electric energy support and help the grid stabilize the voltage.

[0105] In the island operation state, the photovoltaic inverter switches to Vf control. At the same time, the chemical battery energy storage device starts to work and provides stable power output in constant voltage mode.

[0106] In one embodiment of the present invention, the grid operation mode data is time series data of grid voltage;

[0107] The operation condition of the photovoltaic and hybrid energy storage power generation system is determined according to the grid operation mode data, and the grid connection strategy of the photovoltaic and hybrid energy storage power generation system is controlled according to the operation condition, specifically:

[0108] When the photovoltaic and hybrid energy storage power generation system is in a normal grid-connected state, it is determined whether the grid has experienced a voltage drop caused by a disturbance or fault based on the grid operation mode data;

[0109] If the voltage drop caused by both disturbance and fault occurs, the photovoltaic and hybrid energy storage power generation system is connected to the grid in normal operation;

[0110] If a voltage drop occurs due to a disturbance or fault, the photovoltaic and hybrid energy storage power generation system is operated in a low voltage ride-through state;

[0111] When the photovoltaic and hybrid energy storage power generation system is in the low voltage ride-through state, the execution state of the low voltage ride-through is determined according to the grid operation mode data;

[0112] If the low voltage ride-through is completed, the photovoltaic and hybrid energy storage power generation systems will be connected to the grid as normal;

[0113] If the low voltage ride-through is not completed, the photovoltaic and hybrid energy storage power generation system is allowed to maintain the low voltage ride-through state;

[0114] If the low voltage ride through fails, the photovoltaic and hybrid energy storage power generation system is operated in an island operation state;

[0115] When the photovoltaic and hybrid energy storage power generation system is in an island operation state, it is determined whether the grid has voltage drops caused by disturbances or faults based on the grid operation mode data;

[0116] If no voltage drop caused by disturbance or fault occurs, the photovoltaic and hybrid energy storage power generation system is connected to the grid in normal operation;

[0117] If a voltage drop occurs due to a disturbance or a fault, the photovoltaic and hybrid energy storage power generation system is kept operating in an island operation state.

[0118] refer to Figure 3 In order to make the photovoltaic cell work at the maximum power point, it is necessary to adjust the duty cycle of the Boost converter in real time. In one embodiment of the present invention, the Boost converter adopts MPPT control, specifically:

[0119] Get the output voltage U of the photovoltaic unit PV and output current I PV ;

[0120] The output voltage U is adjusted by the MPPT algorithm. PV and output current I PV Processing is performed to obtain the photovoltaic voltage command value U PV-ref ;

[0121] The output voltage U of the photovoltaic cell PV With the photovoltaic voltage command value U PV-ref The error is input into the PI controller of the Boost converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal;

[0122] The switch tube of the Boost converter is driven according to the driving signal to adjust the duty cycle of the Boost converter.

[0123] refer to Figure 4 In one embodiment of the present invention, the DC-AC grid-connected inverter adopts a DC constant voltage dual-loop control, specifically:

[0124] Get the DC bus voltage U dc and reference voltage U dc-ref ;

[0125] The DC bus voltage U dc With reference voltage U dc-ref The error is input into the PI controller of the DC-AC grid-connected inverter, and the output of the PI controller is used as the d-axis component command value i of the inductor current. Ld-ref ;

[0126] Obtain the inductor current i of the DC-AC grid-connected inverterLabc and grid voltage phase θ;

[0127] The inductor current i of the DC-AC grid-connected inverter Labc and the grid voltage phase θ are input into the coordinate transformation module abc / dq0 to obtain the d-axis component i of the inductor current of the DC-AC grid-connected inverter Ld and the q-axis component i Lq ;

[0128] The d-axis component i Ld The d-axis component command value i Ld-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the modulation wave d-axis component u md ;

[0129] Get the inductor current q-axis component command value i Lq-ref ;

[0130] The q-axis component i Lq The q-axis component command value i Lq-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the modulation wave q-axis component u mq ;

[0131] The modulated wave d-axis component u md , the modulated wave q-axis component u mq and the grid voltage phase θ are input into the coordinate transformation module dq0 / abc to obtain the PWM modulation wave u mabc ;

[0132] After the PWM modulation wave is subjected to pulse width modulation, a driving signal is obtained;

[0133] The switch tube of the DC-AC grid-connected inverter is driven according to the driving signal.

[0134] In this implementation, the DC-AC grid-connected converter control adopts voltage and current dual-loop control, the outer loop controls the DC bus voltage, and the DC bus voltage U is sampled. dc The error between it and the given voltage reference value is used as the input of the voltage outer loop PI controller, and the output is used as the inductor current d-axis component command value i Ld-ref By adjusting the output active power of the inverter, the DC bus voltage is maintained at a given reference voltage U dc-ref At the same time, single-loop current limiting control is performed on the q-axis current component.

[0135] Since the inverter is usually connected to the grid with unity power factor, the grid-connected inverter only generates active power but not reactive power. The q-axis component command value of the inductor current i Ld-ref Take 0.

[0136] refer to Figure 5 In one embodiment of the present invention, the first bidirectional DC-DC converter adopts constant current control, specifically:

[0137] Get the charging current reference value I of chemical battery energy storage bat-ref and charging current I bat ;

[0138] The charging current I bat With the charging current reference value I bat-ref The error is input into the PI controller of the first bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal;

[0139] The switch tube of the first bidirectional DC-DC converter is driven according to the driving signal, so that the chemical battery energy storage is in a constant current charging state.

[0140] refer to Figure 6 In one embodiment of the present invention, the second bidirectional DC-DC converter adopts constant current control, specifically:

[0141] Get the charging current reference value I of the supercapacitor energy storage sc-ref and charging current I sc ;

[0142] The charging current I sc With the charging current reference value I sc-ref The error is input into the PI controller of the second bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal;

[0143] The switch tube of the second bidirectional DC-DC converter is driven according to the driving signal, so that the supercapacitor energy storage is in a constant current charging state.

[0144] refer to Figure 7 In one embodiment of the present invention, the DC-AC grid-connected inverter adopts single current loop control, specifically:

[0145] Obtain the filter inductor current amplitude I of the DC-AC grid-connected inverter L-lim , the inductor current d-axis component command value i Ld-ref and the inductor current q-axis component command value i Lq-ref The inductor current d-axis component command value i Ld-ref Calculated based on the inductor current limit value and reactive current command value;

[0146] The filter inductor current amplitude I L-limand the inductor current d-axis component command value i Ld-ref Input limiter, according to the filter inductor current amplitude I L-lim The inductor current d-axis component command value i Ld-ref To limit the clipping;

[0147] The filter inductor current amplitude I L-lim and the inductor current q-axis component command value i Lq-ref Input limiter, according to the filter inductor current amplitude I L-lim The q-axis component command value i of the inductor current is Lq-ref To limit the clipping;

[0148] Obtain the inductor current i of the DC-AC grid-connected inverter Labc and grid voltage phase θ;

[0149] The inductor current i of the DC-AC grid-connected inverter Labc and the grid voltage phase θ are input into the coordinate transformation module abc / dq0 to obtain the d-axis component i of the inductor current of the DC-AC grid-connected inverter Ld and the q-axis component i Lq ;

[0150] The output of A and the d-axis component i Ld The error is input into the PI controller to obtain the modulation wave d-axis component u md ;

[0151] The output of A and the q-axis component i Lq The error is input into the PI controller to obtain the modulation wave q-axis component u mq ;

[0152] The d-axis component u md , the q-axis component u mq and the grid voltage phase θ are input into the coordinate transformation module dq0 / abc to obtain the PWM modulation wave u mabc ;

[0153] After the PWM modulation wave is subjected to pulse width modulation, a driving signal is obtained;

[0154] The switch tube of the DC-AC grid-connected inverter is driven according to the driving signal.

[0155] Inductor current q-axis component command value i Lq-ref The calculation method is as follows:

[0156] i Lq-ref =1.5×(0.85-U t );

[0157] Among them, Ut is the per unit value of the grid connection point voltage, 0≤U t ≤0.85;

[0158] Inductor current d-axis component command value i Ld-ref The calculation method is as follows:

[0159]

[0160] refer to Figure 8 In one embodiment of the present invention, the second bidirectional DC-DC converter adopts constant voltage control, specifically:

[0161] Get the DC bus voltage U dc , reference voltage U dc-ref and the charging current I of the supercapacitor energy storage sc ;

[0162] The DC bus voltage U dc With reference voltage U dc-ref The error is input into the PI controller of the second bidirectional DC-DC converter to obtain the charging current reference value I of the supercapacitor energy storage. sc-ref ;

[0163] The charging current I sc and the charging current reference value I sc-ref The error is input into the PI controller of the second bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal;

[0164] The switch tube of the second bidirectional DC-DC converter is driven according to the driving signal, so that the charging power of the supercapacitor energy storage can maintain the constant DC bus voltage.

[0165] refer to Fig. 9 In one embodiment of the present invention, the DC-AC grid-connected inverter adopts Vf control, specifically:

[0166] Get the DC-AC grid-connected inverter output voltage U abc , output voltage command value U abc-ref and grid voltage phase θ;

[0167] The output voltage U abc The grid voltage phase θ is input into the coordinate transformation module abc / dq0 to obtain the d-axis component U of the DC-AC grid-connected inverter output voltage. d and the q-axis component U q ;

[0168] The output voltage command value U abc-refThe grid voltage phase θ is input into the coordinate transformation module abc / dq0 to obtain the d-axis component U of the DC-AC grid-connected inverter output voltage command value. d-ref and the q-axis component U q-ref ;;

[0169] The d-axis component U d and the d-axis component U d-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the d-axis component command value i of the inductor current Ld-ref ;

[0170] The q-axis component U q With the q-axis component U q-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the q-axis component command value i of the inductor current Lq-ref ;

[0171] Get the inductor current i of the DC-AC grid-connected inverter Labc ;

[0172] The inductor current i Labc and the grid voltage phase θ are input into the coordinate transformation module abc / dq0 to obtain the d-axis component i of the inductor current of the DC-AC grid-connected inverter Ld and the q-axis component i Lq ;

[0173] The d-axis component i Ld and the d-axis component command value i Ld-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the modulation wave d-axis component u md ;

[0174] The q-axis component i Lq and the q-axis component command value i Lq-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the modulation wave q-axis component u mq ;

[0175] The d-axis component u of the modulated wave md , modulation wave q-axis component u mq And the grid voltage phase θ is input into the coordinate transformation module dq0 / abc to obtain the PWM modulation wave u mabc ;

[0176] After the PWM modulation wave is subjected to pulse width modulation, a driving signal is obtained;

[0177] The switch tube of the DC-AC grid-connected inverter is driven according to the driving signal.

[0178] refer to Fig.10In one embodiment of the present invention, the first bidirectional DC-DC converter adopts constant voltage control, specifically:

[0179] Get the DC bus voltage U dc , reference voltage U dc-ref and the charging current I of chemical battery energy storage bat ;

[0180] The DC bus voltage U dc With reference voltage U dc-ref The error is input into the PI controller of the first bidirectional DC-DC converter to obtain the charging current reference value I of the chemical battery energy storage bat-ref ;

[0181] The charging current I bat and the charging current reference value I bat-ref The error is input into the PI controller of the first bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal;

[0182] The switch tube of the first bidirectional DC-DC converter is driven according to the driving signal, so that the charging power of the chemical battery energy storage can maintain the constant DC bus voltage.

[0183] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A multi-operating condition optimization control method for a photovoltaic and hybrid energy storage power generation system, which controls the photovoltaic and hybrid energy storage power generation system, wherein the photovoltaic and hybrid energy storage power generation system comprises a photovoltaic unit, a chemical battery energy storage unit and a supercapacitor energy storage unit, wherein the photovoltaic unit is connected to a DC bus through a Boost converter, wherein the chemical battery energy storage unit and the supercapacitor energy storage unit are connected to the DC bus through a first bidirectional DC-DC converter and a second bidirectional DC-DC converter, respectively, and the DC bus is connected to a power grid through a DC-AC grid-connected inverter, wherein: The following steps are involved: Acquire grid operation mode data, determine the operation condition of the photovoltaic and hybrid energy storage power generation system according to the grid operation mode data, and control the grid connection strategy of the photovoltaic and hybrid energy storage power generation system according to the operation condition, wherein the grid connection strategy includes normal grid connection, low voltage ride-through and island operation; The Boost converter adopts MPPT control; When the photovoltaic and hybrid energy storage power generation system is in a normal grid-connected state, the DC-AC grid-connected inverter adopts a DC constant voltage dual-loop control, and the first bidirectional DC-DC converter and the second bidirectional DC-DC converter both adopt a constant current control; When the photovoltaic and hybrid energy storage power generation system is in low voltage ride-through, the DC-AC grid-connected inverter adopts single current loop control, the first bidirectional DC-DC converter adopts constant current control, and the second bidirectional DC-DC converter adopts constant voltage control; When the photovoltaic and hybrid energy storage power generation system is in island operation, the DC-AC grid-connected inverter adopts Vf control. The first bidirectional DC-DC converter adopts constant voltage control, and the second bidirectional DC-DC converter adopts constant current control.

2. The multi-operating condition optimization control method of photovoltaic and hybrid energy storage power generation system according to claim 1 is characterized in that: The grid operation mode data is time series data of grid voltage; The operation condition of the photovoltaic and hybrid energy storage power generation system is determined according to the grid operation mode data, and the grid connection strategy of the photovoltaic and hybrid energy storage power generation system is controlled according to the operation condition, specifically: When the photovoltaic and hybrid energy storage power generation system is in a normal grid-connected state, it is determined whether the grid has experienced a voltage drop caused by a disturbance or fault based on the grid operation mode data; If the voltage drop caused by both disturbance and fault occurs, the photovoltaic and hybrid energy storage power generation system is connected to the grid in normal operation; If a voltage drop occurs due to a disturbance or fault, the photovoltaic and hybrid energy storage power generation system is operated in a low voltage ride-through state; When the photovoltaic and hybrid energy storage power generation system is in the low voltage ride-through state, the execution state of the low voltage ride-through is determined according to the grid operation mode data; If the low voltage ride-through is completed, the photovoltaic and hybrid energy storage power generation systems will be connected to the grid as normal; If the low voltage ride-through is not completed, the photovoltaic and hybrid energy storage power generation system is allowed to maintain the low voltage ride-through state; If the low voltage ride through fails, the photovoltaic and hybrid energy storage power generation system is operated in an island operation state; When the photovoltaic and hybrid energy storage power generation system is in an island operation state, it is determined whether the grid has voltage drops caused by disturbances or faults based on the grid operation mode data; If no voltage drop caused by disturbance or fault occurs, the photovoltaic and hybrid energy storage power generation system is connected to the grid in normal operation; If a voltage drop occurs due to a disturbance or a fault, the photovoltaic and hybrid energy storage power generation system is kept operating in an island operation state.

3. The multi-operating condition optimization control method of photovoltaic and hybrid energy storage power generation system according to claim 1 is characterized in that: The Boost converter adopts MPPT control, specifically: Get the output voltage U of the photovoltaic unit PV and output current I PV ; The output voltage U PV and output current I PV Processing is performed to obtain the photovoltaic voltage command value U PV-ref ; The output voltage U of the photovoltaic cell PV With the photovoltaic voltage command value U PV-ref The error is input into the PI controller of the Boost converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal; The switch tube of the Boost converter is driven according to the driving signal to adjust the duty cycle of the Boost converter.

4. The multi-operating condition optimization control method of photovoltaic and hybrid energy storage power generation system according to claim 1 is characterized in that: The DC-AC grid-connected inverter adopts DC constant voltage dual-loop control, specifically: Get the DC bus voltage U dc and reference voltage U dc-ref ; The DC bus voltage U dc With reference voltage U dc-ref The error is input into the PI controller of the DC-AC grid-connected inverter, and the output of the PI controller is used as the d-axis component command value i of the inductor current. Ld-ref ; Obtain the inductor current i of the DC-AC grid-connected inverter Labc and grid voltage phase θ; The inductor current i of the DC-AC grid-connected inverter Labc and the grid voltage phase θ are input into the coordinate transformation module abc / dq0 to obtain the d-axis component i of the inductor current of the DC-AC grid-connected inverter Ld and the q-axis component i Lq ; The d-axis component i Ld The d-axis component command value i Ld-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the modulation wave d-axis component u md ; Get the inductor current q-axis component command value i Lq-ref ; The q-axis component i Lq The q-axis component command value i Lq-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the modulation wave q-axis component u mq ; The modulated wave d-axis component u md , the modulated wave q-axis component u mq and the grid voltage phase θ are input into the coordinate transformation module dq0 / abc to obtain the PWM modulation wave u mabc ; After the PWM modulation wave is subjected to pulse width modulation, a driving signal is obtained; The switch tube of the DC-AC grid-connected inverter is driven according to the driving signal.

5. The multi-operating condition optimization control method of photovoltaic and hybrid energy storage power generation system according to claim 1 is characterized in that: The first bidirectional DC-DC converter adopts constant current control, specifically: Get the charging current reference value I of chemical battery energy storage bat-ref and charging current I bat ; The charging current I bat With the charging current reference value I bat-ref The error is input into the PI controller of the first bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal; The switch tube of the first bidirectional DC-DC converter is driven according to the driving signal, so that the chemical battery energy storage is in a constant current charging state.

6. The multi-operating condition optimization control method of photovoltaic and hybrid energy storage power generation system according to claim 1 is characterized in that: The second bidirectional DC-DC converter adopts constant current control, specifically: Get the charging current reference value I of the supercapacitor energy storage sc-ref and charging current I sc ; The charging current I sc With the charging current reference value I sc-ref The error is input into the PI controller of the second bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal; The switch tube of the second bidirectional DC-DC converter is driven according to the driving signal, so that the supercapacitor energy storage is in a constant current charging state.

7. The multi-operating condition optimization control method of photovoltaic and hybrid energy storage power generation system according to claim 1 is characterized in that: The DC-AC grid-connected inverter adopts single current loop control, specifically: Obtain the filter inductor current amplitude I of the DC-AC grid-connected inverter L-lim , the inductor current d-axis component command value i Ld-ref and the inductor current q-axis component command value i Lq-ref ; The filter inductor current amplitude I L-lim and the inductor current d-axis component command value i Ld-ref Input limiter, according to the filter inductor current amplitude I L-lim The inductor current d-axis component command value i Ld-ref To limit the clipping; The filter inductor current amplitude I L-lim and the inductor current q-axis component command value i Lq-ref Input limiter, according to the filter inductor current amplitude I L-lim The q-axis component command value i of the inductor current is Lq-ref To limit the clipping; Obtain the inductor current i of the DC-AC grid-connected inverter Labc and grid voltage phase θ; The inductor current i of the DC-AC grid-connected inverter Labc and the grid voltage phase θ are input into the coordinate transformation module abc / dq0 to obtain the d-axis component i of the inductor current of the DC-AC grid-connected inverter Ld and the q-axis component i Lq ; The output of A and the d-axis component i Ld The error is input into the PI controller to obtain the modulation wave d-axis component u md ; The output of A and the q-axis component i Lq The error is input into the PI controller to obtain the modulation wave q-axis component u mq ; The d-axis component u md , the q-axis component u mq and the grid voltage phase θ is input into the coordinate transformation module dq0 / abc, Get the pwm modulation wave u mabc ; After the PWM modulation wave is subjected to pulse width modulation, a driving signal is obtained; The switch tube of the DC-AC grid-connected inverter is driven according to the driving signal.

8. The multi-operating condition optimization control method of photovoltaic and hybrid energy storage power generation system according to claim 1 is characterized in that: The second bidirectional DC-DC converter adopts constant voltage control, specifically: Get the DC bus voltage U dc , reference voltage U dc-ref and the charging current I of the supercapacitor energy storage sc ; The DC bus voltage U dc With reference voltage U dc-ref The error is input into the PI controller of the second bidirectional DC-DC converter to obtain the charging current reference value I of the supercapacitor energy storage. sc-ref ; The charging current I sc and the charging current reference value I sc-ref The error is input into the PI controller of the second bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal; The switch tube of the second bidirectional DC-DC converter is driven according to the driving signal, so that the charging power of the supercapacitor energy storage can maintain the constant DC bus voltage.

9. The multi-operating condition optimization control method of photovoltaic and hybrid energy storage power generation system according to claim 1 is characterized in that: The DC-AC grid-connected inverter adopts Vf control, specifically: Get the DC-AC grid-connected inverter output voltage U abc , output voltage command value U abc-ref and grid voltage phase θ; The output voltage U abc The grid voltage phase θ is input into the coordinate transformation module abc / dq0 to obtain the d-axis component U of the DC-AC grid-connected inverter output voltage. d and the q-axis component U q ; The output voltage command value U abc-ref The grid voltage phase θ is input into the coordinate transformation module abc / dq0 to obtain the d-axis component U of the DC-AC grid-connected inverter output voltage command value. d-ref and the q-axis component U q-ref ;; The d-axis component U d and the d-axis component U d-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the d-axis component command value i of the inductor current Ld-ref ; The q-axis component U q and the q-axis component U q-ref The error is input into the PI controller of the DC-AC grid-connected inverter to obtain the q-axis component command value i of the inductor current Lq-ref ; Get the inductor current i of the DC-AC grid-connected inverter Labc ; The inductor current i Labc and the grid voltage phase θ are input into the coordinate transformation module abc / dq0 to obtain the d-axis component i of the inductor current of the DC-AC grid-connected inverter Ld and the q-axis component i Lq ; The d-axis component i Ld and the d-axis component command value i Ld-ref The error is input into the PI controller of the DC-AC grid-connected inverter. Get the modulated wave d-axis component u md ; The q-axis component i Lq and the q-axis component command value i Lq-ref The error is input into the PI controller of the DC-AC grid-connected inverter. Get the q-axis component u of the modulated wave mq ; The d-axis component u of the modulated wave md , modulation wave q-axis component u mq And the grid voltage phase θ is input into the coordinate transformation module dq0 / abc to obtain the PWM modulation wave u mabc ; After the PWM modulation wave is subjected to pulse width modulation, a driving signal is obtained; The switch tube of the DC-AC grid-connected inverter is driven according to the driving signal.

10. The multi-operating condition optimization control method of photovoltaic and hybrid energy storage power generation system according to claim 1, characterized in that: The first bidirectional DC-DC converter adopts constant voltage control, specifically: Get the DC bus voltage U dc , reference voltage U dc-ref and the charging current I of chemical battery energy storage bat ; The DC bus voltage U dc With reference voltage U dc-ref The error is input into the PI controller of the first bidirectional DC-DC converter to obtain the charging current reference value I of the chemical battery energy storage bat-ref ; The charging current I bat and the charging current reference value I bat-ref The error is input into the PI controller of the first bidirectional DC-DC converter, and the output of the PI controller is used as a modulation wave and subjected to pulse width modulation to obtain a driving signal; The switch tube of the first bidirectional DC-DC converter is driven according to the driving signal, so that the charging power of the chemical battery energy storage can maintain the constant DC bus voltage.

Images