74 results about "Inner current loop" patented technology

A controller for determining the duty-ratio for a pulse width modulator of a converter includes an inner current loop, an outer voltage loop and a multiplier with an input voltage feed forward to connect both loops. A prediction unit determines a correction signal i_cor that is added to the reference current i_ref by means of an adder and it further determines a sample correction signal to correct the current samples in the current loop. This error-controlled duty-ratio prediction with sample correction results in an improved total harmonic distortion as well as in an improved power factor of the converter.

The invention discloses a voltage-equalizing and power-equalizing control method for a multi-module cascade solid-state transformer (SST). An SST power main circuit part applied in the method comprises an input stage, an intermediate stage and an output stage, wherein a common duty ratio control policy based on single-phase d-q vector control is adopted in the input stage so as to realize the unit power factor of an input end of an electric network; a control policy based on voltage feedforward and voltage feedback is introduced for each module in the intermediate stage, the voltage feedforward is used as a reference of the voltage feedback, and an error between the voltage feedforward and the voltage feedback is used as a reference of inner current loop of the module after being output by a voltage PI adjuster. The two control policies of the front stage and the intermediate stage interact so as to realize the functions of voltage and power equalization of each SST module, electrical network side unit power factor, high electrical network current sine degree, low switching tube voltage stress and the like.

The invention relates to a symmetrical drop-off low voltage ride through reactive power control method of a photovoltaic power generation system. A controller detects whether a grid connection point voltage drops off in real time, and if the voltage does not drop off to 90% of a nominal voltage, an active current reference value id* is taken from an outer voltage loop, and grid connection control when the voltage is normal is adopted; if the grid connection point voltage drops off below 90% of the nominal voltage, the outer voltage ring is disconnected, low-voltage ride through control is adopted, namely inner current loop control is adopted, definite reactive power is output to a power grid by the photovoltaic power generation system according to the drop-off amplitude, and recovery of the voltage of the power grid is facilitated; if it is detected that the voltage recovers, the active power of the photovoltaic power generation system recovers at 10% rated power/second, reactive power is gradually reduced to zero at the same time, and finally the grid connection control when the voltage is normal is adopted. According to the method, an outlet current of a photovoltaic grid-connected inverter is limited within an over-current protection action current, reactive power support is provided for the grid voltage to recover to the normal value, investment of reactive power equipment is saved, and resources are saved.

The invention discloses a control circuit of a non-isolated bidirectional DC/DC transducer and a control method thereof. The control circuit comprises an input voltage sensor, an input current sensor, an output voltage sensor, a DSP control plate and an IGBT driver circuit. The input voltage sensor is connected in parallel to the input terminal on the main circuit of the bidirectional DC/DC transducer. The input current sensor is connected in series to the input circuit on the main circuit of the bidirectional DC/DC transducer. The output voltage sensor is connected in parallel to the output terminal on the main circuit of the bidirectional DC/DC transducer. The DSP control plate is respectively connected with the input voltage sensor, the input current sensor, the output voltage sensor and IGBT drive circuit. The control method comprises sampling, inner voltage loop regulating, inner current loop regulating and generating PWM waveform. An automatic control unit is added to the invention so as to write the major algorithm of the control method to the DSP control plate. Therefore the automatization level of the non-isolated bidirectional DC/DC transducer is improved.

The invention provides a method for controlling high-dynamic properties of high-power bidirectional DC/DC converters. The method includes steps of enabling a controller to receive constant-voltage control instructions and constant-voltage control instruction values and acquiring AD (analog-digital) sampled voltage feedback values; changing PI (proportion and integration) control parameters of outer voltage loops when low fluctuating power is outputted by a DC/DC converter and determining current instructions outputted by closed voltage loops under PI control; changing PI parameters of the outer voltage loops according to voltage difference values when the DC/DC converter is subjected to high-power charge and discharge conversion, and outputting the current instructions; changing integration items of inner current loops according to state switching directions when working modes of the DC/DC converter are switched over; transmitting PWM (pulse width modulation) driving signals according to the working modes and a duty cycle of the DC/DC converter. The method has the advantage that the method is used for solving the problem of poor stability of outputted voltages when DC/DC converters are subjected to high-power charge and discharge conversion or run in low-power ranges.

The invention relates to a smooth switching control method for an operating mode of a micro-grid inverter of different capacity micro sources. The method is applied to a micro-grid consisting of multiple different capacity micro sources. The method comprises the following steps: by virtue of switching among different switches, realizing smooth switching of an inverter control method under island/grid-connected operating modes, wherein the island operation is controlled by robust V-f based on capacitive equivalent output impedance so as to generate the voltage reference quantity, and the grid-connected operation is controlled by adopting PQ; adding a pre-synchronization link to be used for controlling the inverter output voltage to trace the power grid voltage when the inverter is switched from island operation to the grid-connected operation, and ensuring that the grid-connected operation is smoothly finished; introducing virtual impedance, designing the equivalent output impedance of the inverter to be capacitive, reducing loop current between parallel inverters, and well realizing power distribution among different capacity micro sources; and adopting double-loop control of the outer voltage loop and inner current loop, wherein the outer voltage loop is controlled by PI, and the inner current loop is controlled by dead beat. Therefore, the system is high in stability and high in dynamic response speed.

The invention discloses a non-isolated bi-directional DC-DC converter control method. A double closed-loop control structure formed by an outer voltage loop and an inner current loop is employed to control single end voltage, the inner current loop employs a current feedback control mode or a current composite control mode, and the sum of current feedback control output and current feedforward control output is control output of the inner current loop. According to the method, the unified control of the non-isolated bi-directional DC-DC converter in a buck mode and a boost mode can be realized, through employing the composite control mode, a response speed of the voltage loop and/or the current loop can be effectively raised, and the performance of the non-isolated bi-directional DC-DC converter is improved.

The invention discloses an ISOS inverter system and its input voltage equalization output same-phase control method, belonging to the field of DC-AC converters. The inverter system includes a power circuit and n inverter modules. Each inverter module adopts a two-stage structure with high-frequency isolation. The front stage is a full-bridge DC converter, and the rear stage is a full-bridge inverter. ; The control loop of the inverter system mainly includes the shared output voltage loop and the input voltage equalizing loop and current inner loop of each inverter module. The three loops work together to achieve the phase consistency of the output voltage of each module, and combine The function of input voltage equalization realizes output voltage equalization. The invention realizes the input voltage equalization and output voltage equalization of the inverter system, and realizes the decoupling of the input voltage equalization loop and the output voltage loop, thereby effectively simplifying the loop design of the system.

The invention discloses a voltage-equalizing and power-equalizing control method for a three-phase multi-module cascade solid-state transformer. A three-phase SST system power main circuit part applied in the method comprises an input stage, an intermediate stage and an output stage, wherein a control policy based on three-phase d-q-0 vector control is adopted in the input stage, a common duty ratio control policy is adopted in modules in the same phase so as to achieve the unit power factor of an input end of an electric network; a control policy based on voltage feedforward and voltage feedback is introduced for each module in the intermediate stage, the voltage feedforward is used as a reference of the voltage feedback, and an error between the voltage feedforward and the voltage feedback is used as a reference of an inner current loop of each module after being output by a voltage PI adjuster. The two control policies of the front stage and the intermediate stage interact so as to achieve the functions of voltage and power equalization of each SST module, electrical network side unit power factor, high electrical network current sine degree, low switching tube voltage stress and the like.

The invention relates to a micro-grid system, which comprises a storage battery, an energy storage converter, a monitoring circuit and a controllable switch. When the micro-grid system is in a grid-connected mode, the energy storage converter outputs a constant power under the control of an inner current loop unit; an outer voltage loop unit does not participate in the control in the grid-connected mode, but is still in an operating state; and the outer voltage loop unit estimates a given current loop signal in advance when the micro-grid system is switched into an island mode from the grid-connected mode according to four input signals of the outer voltage loop unit. When the micro-grid system is switched into the island mode from the grid-connected mode, the outer voltage loop unit is put into operation, and the inner current loop unit controls output voltage and frequency of the energy storage converter to be constant according to the given current loop signal which is estimated in advance and output by the outer voltage loop unit. According to the micro-grid system, the outer voltage loop unit controls the output given current loop signals to be the same before and after the mode is switched, so that seamless switching of the grid-connected mode or the island mode can be achieved. The invention further relates to a control method for the micro-grid system.

The invention discloses a fruit fly-leapfrog-based linear synchronous motor control method employing a fuzzy neural network PID. A control system comprises an outer speed loop and an inner current loop, the current loop is designed into a traditional PID adjuster and the speed loop is designed into a fuzzy neural network PID speed controller; a fruit fly-leapfrog hybrid algorithm is formed through fusing a fruit fly optimization algorithm and a leapfrog algorithm; structure parameters of a fuzzy neural network are adjusted and optimized in real time, optimal parameters kp, ki and kd suitable for the PID controller are output and self-adaptation and intellectualization of speed control on a permanent-magnet linear synchronous motor are achieved. Simulation analysis and experiment results show that the control accuracy and the disturbance resistance of a permanent-magnet linear synchronous motor control system can be improved by adopting a fuzzy neural network PID speed control strategy optimized on the basis of the fruit fly-leapfrog hybrid algorithm, and an excellent control effect is achieved.

The invention discloses a control method for a three-phase PWM rectifier suitable for power grid waveform distortion. The control method for the three-phase PWM rectifier suitable for the power grid waveform distortion mainly includes that extracting a current reference signal under input voltage distortion and unbalanced disturbance, and actively injecting negative-sequence current, improved dead-beat inner current loop which is forecast through combining with linear extrapolation, and outer direct voltage loop performed with active disturbance rejection control. The control method for the three-phase PWM rectifier suitable for the power grid waveform distortion plays roles of inhibiting the harmonic wave of the input current of the PWM rectifier, injecting proper negative-sequence current to eliminate the secondary power pulse of the output direct current voltage of the PWM rectifier, improving the transient response of the output direct current voltage, and compensating the influences of all kinds of delay on the dead-beat control. The control method for the three-phase PWM rectifier suitable for the power grid waveform distortion is capable of obviously reducing the secondary wave of the output direct current voltage under the disturbance of the input harmonic wave and unbalanced voltage, improving the transient response speed of the PWM rectifier, reducing the transient offset of the direct current voltage, and improving the system control precision.

The invention provides an induction machine vector control method taking account of iron loss adopts dual closed-loop control of an outer speed loop and an inner current loop, wherein the outer speed loop adopts the rotational speed PI modulating control of a motor and outputs a torque current instruction value of the inner current loop; the inner current loop adopts torque current and field current PI modulating control; in the inner current loop, the torque current and the field current are respectively compensated; and the compensated torque current and field current components are led into the current PI regulation. The induction machine vector control method takes the influence of iron loss on the field orientation and the field intensity into consideration, and improves the field orientation accuracy and control performance of a traditional induction machine vector control method, particularly the speed operating precision in a weak magnetic region and the stability in current control.

The invention provides an MMC-based low-voltage ride through control method and system of a photovoltaic grid-connected inverter. On the basis of traditional inner current loop and outer voltage loop double closed-loop vector control, when a grid-connected point voltage drop is detected, a reactive current instruction value as shown in the specification is redistributed by judging the voltage drop degree to achieve reactive current injection; the capacitor voltage fluctuation range of an MMC sub-module is adjusted by optimizing bridge arm current; a new active current instruction value is introduced to limit active current; and the active current is limited, so that low-voltage ride through is achieved and safe photovoltaic grid-connected operation is ensured. Through the system and the method, capacitor voltage fluctuation is suppressed by optimizing bridge arm loop current; output reactive power is increased; and the capacitor voltage fluctuation range of the sub-module is optimized by controlling reference voltage of the sub-module, so that the problem that the capacitor voltage fluctuation of the MMC sub-module is out of the limit during reactive injection is solved; and low-voltage ride through is smoothly achieved.

The present invention provides a parallel current-sharing device and control method without a current-sharing bus, for implementing parallel current sharing of direct-current outputs of a plurality of power conversion submodules. The parallel current-sharing device comprises a voltage control module and a plurality of power conversion submodules. The voltage control module and the plurality of power conversion submodules having parallel outputs form an outer voltage loop. The power conversion submodules comprise respective inner current loops and sample respective current feedback signals to generate inner current loop control signals, and the inner current loop control signals are superposed with an outer voltage loop control signal to control output of the power conversion submodules. An independent current bus is not required, and only one unidirectional outer control voltage loop is required. Functions the same as those of a conventional device are realized; the design, production and debugging of circuits of the parallel current-sharing device are simpler; a rapid multi-parallel dynamic response is realized; a ground wire loop current is eliminated, improving the anti-interference capability of the device; and multi-module parallel current sharing of a switching power supply or a linear power supply under analog control or digital control is realized very easily.

The invention discloses a multi-functional storage battery charging and discharging device and a control method thereof. The device adopts two-stage transformation. A front-stage unit adopts a three-phase PWM rectifier to obtain a DC-side voltage, the grid-side access current harmonics is reduced, the power factor is improved, and the energy loss is reduced; a rear-stage unit uses an interleaved parallel bidirectional half-bridge converter to greatly reduce the output filter inductance. The three-phase PWM rectifier adopts a double closed-loop control strategy of the voltage outer loop and thecurrent inner loop to realize high-precision control of the DC bus voltage and high-power factor control of the grid-side current; when the bidirectional half-bridge converter controls the output voltage, the double closed-loop control strategy of the voltage outer loop and the current inner loop is adopted to use the single loop control of the inner current loop during control of the output current; when a storage battery is charged, the control current is positive, and when the storage battery is discharged, the control current is negative; and when more power is required, the output ends of the two devices are switched to work in series or in parallel through a switch.

An NPC converter is controlled by estimating current flow during the short vector periods of a space vector modulation drive signal. The current estimation is used to close a first order inner current regulator loop that steers current to either the upper capacitor or the lower capacitor of a DC link. An outer voltage regulator measures the voltage imbalance across the capacitors and drives the inner current loop. By managing the associated duty cycle of each vector a bias current is formed that balances the capacitor voltages.

The invention discloses a design of a nonlinear predictive controller for a permanent magnet synchronous motor with a disturbance observer, and belongs to the technical field of a high-performance motor driving control system. According to the invention, firstly, all model errors and external disturbances are considered under a dq coordinate system, and a nonlinear mathematical model of the PMSM (Permanent Magnet Synchronous Motor) is constructed; secondly, predictive controllers of an outer speed loop and an inner current loop are respectively designed on the basis of the model, and a disturbance observer is designed when there is a control device limitation. The design disclosed by the invention overcomes a defect that the system has limitations for processed variables and greatly depends on electric parameters of the motor on the aspect of the limiting current through designing the nonlinear model predictive controller with a cascade structure and designing the anti-saturation disturbance observer, and the disturbance is considered and compensated in predictive controller, thereby enhancing the robustness of the permanent magnet synchronous motor control system. Experiments showthat the method can enable the system to output a more accurate tracking reference trajectory, and it is considered that the current limitation can keep high robustness when there is a model parameter error or load change at the same time.

The invention discloses a static synchronous compensation circuit. The static synchronous compensation circuit comprises a static synchronous compensator. The output end of the static synchronous compensator is connected with a capacitor Cc in series and then connected into a power distribution system. The invention further discloses a decoupling control method based on the static synchronous compensation circuit. The decoupling control method based on the static synchronous compensation circuit comprises the steps that firstly, the alternating-current voltage us on a net-side PCC and the alternating-current voltage ucs on the capacitor Cc are detected through a voltage inductor, and a reactive compensation current ic is detected through a current inductor; secondly, the voltage udc on a direct-current capacitor C is obtained through a direct-current voltage detection circuit; thirdly, a balance equation of voltage on the alternating-current side of a VSC and a relational expression between the voltage and the current on the capacitor Cc are listed; fourthly, double loop control of an outer voltage loop and an inner current loop is adopted by the static synchronous compensator. By the adoption of the static synchronous compensation circuit and the decoupling control method based on the static synchronous compensation circuit, the starting performance is remarkably improved, the voltage stress of a switching device is reduced obviously, and the total harmonic distortion of an output current of a compensation device is reduced.

The invention discloses a control method of a three-phase PWM (pulse width modulation) rectification based on novel model prediction control. The control method mainly consists of an outer voltage loop and a model prediction control step, wherein the outer voltage loop is a PI link, and the model prediction control is an inner current loop control. According to key points of the control method of the three-phase PWM rectifier, the algorithm is simplified on the basis of traditional finite set model prediction control, the switch actuation times is reduced, the switch frequency is reduced, the switch actions at two adjacent sampling moments are mutually associated to each other, a feedback characteristic is realized, and the switch action is not random and irregular. According to the control method of the three-phase PWM rectifier, the advantages of the finite model prediction control are maintained, the advantages such as rapidness in control algorithm and low switch loss can be achieved.

The invention relates to a control method for a direct current voltage of a grid-side converter of a high-voltage doubly-fed power generation system. The control method for the direct current voltage of the grid-side converter of the high-voltage doubly-fed power generation system includes the following steps: 1) when a power grid voltage is located at a normal working condition, controlling the direct current voltage of the grid-side converter through an inner current loop and an outer direct current voltage loop; 2) judging whether the power grid voltage rises stably, if not, performing a step 3), if so, re-determining a proper direct current running voltage U'dc-ref and a working voltage of a Chopper component, and using the same control process as that of the step 1) to control the grid-side direct current voltage of the converter; 3) judging whether the power grid voltage appears transient change, if not, ending the control process, if so, controlling the direct current voltage of the grid-side converter through the single close-loop control of current. The control method for the direct current voltage of the grid-side converter of the high-voltage doubly-fed power generation system can be broadly used for controlling the grid-side direct current voltage of the converter.

The invention discloses a method for suppressing a transient drop of DC voltage of a photovoltaic inverter. The method comprises the steps of (1) calculating differential Udc-d of DC voltage Udc of aninverter in each control period; (2) summing the differential Udc-d of the DC voltage and the DC voltage Udc, producing a difference between the sum and a reference value Udc<*> of the DC voltage toobtain an error of the DC voltage, and obtaining output Udc-out of an outer DC voltage loop through a DC voltage PI controller according to the error of the DC voltage; (3) adding DC all-feedforward iffd to the output Udc-out of the outer DC voltage loop to obtain a reference value i1<*> of an inner current loop; (4) subtracting a current sampling value i1 from the reference value i1<*> of the inner current loop to obtain a current error value, and obtaining controlled quantity of the control period through an inner current loop PI controller according to the current error value; and (5) modulating the controlled quantity to obtain PWM pulses of various switch tubes. According to the method, the transient drop of the DC voltage can be greatly suppressed and the response is fast.