RU2711312C1 - Resonance key control method - Google Patents

Abstract

FIELD: electronic equipment.SUBSTANCE: invention relates to power electronics, particularly to control of hybrid power modules, and can be used in development of converters with energy-efficient resonant switching methods. Technical result is achieved by the fact that in the resonance key control method two additional intervals of free circulation of the resonant throttle current part in the circuit of the short-circuited loop are introduced.EFFECT: technical result is provision of identical durations of control pulses of auxiliary switch and their independence from electric operating mode of circuit and parameters of spread of nominal values of elements of resonance circuit; thus providing synchronization of control pulses of all key elements in the resonant key with pulse width modulated pulse width of signals of converter control logic circuit.1 cl, 5 dwg

Description

The proposal relates to power electronics, in particular to the management of hybrid power modules and can be used in the development of converters with energy-efficient resonant switching methods.

The most effective way to reduce the power of dynamic losses in semiconductor switches is to actively separate the edges of its current and voltage, which in practice is realized using various methods of resonant switching.

The resonant switch (RC) consists of connecting a semiconductor element with an LC oscillatory circuit - a circuit. The resonant LC circuit forms a “smooth” trajectory of the voltage and current changes of the semiconductor switch and ensures its switching in zero voltage and current modes. The most effective solution is to use a RC with a composite series - parallel LCC circuit. When unlocking the semiconductor key, the composite circuit operates as a parallel LC circuit, which provides a forced voltage drop to zero in its output circuit. When locking a semiconductor key, the composite circuit operates as a sequential LC circuit, forming a current directed counter-to the load current, ensuring that the semiconductor switch is turned off at zero current. An integral element of the RK circuit used in converters with a pulse-width regulation method (PWM) is an auxiliary semiconductor switch. The purpose of this key is to activate the resonant process at the right time. As a rule, the activation of the resonance process must be carried out immediately before turning on and immediately before turning off the main semiconductor switch as part of the RC. In this case, the auxiliary key must be unlocked for a relatively short time interval, however, sufficient for the resonant process in the output circuit of the main key to provide a zero voltage level when turned on and a zero current level when turned off.

A known method of controlling a resonant key (RU 2457600 G1, 07.27.07.2012), in which the auxiliary key is unlocked twice for a relatively short time in each of the switching cycles. The first time it is unlocked immediately before turning on the main key, which provides a resonant discharge of the output capacitance of the main key, and creates the condition for its subsequent unlocking at zero voltage. The second time, the auxiliary key is unlocked immediately before the main key is turned off, which provides a resonant current discharge in the output circuit of the main key, and creates a condition for its subsequent locking at zero current. The disadvantage of this control method is that the pulse widths of the auxiliary key control, in addition to the main intervals necessary for conducting the main resonant processes, ensuring zero voltage and current levels of the main key, contain additional intervals within themselves. In the first control pulse, this is half the period of the resonant frequency of the serial LC circuit, necessary for additional recharging of the resonant capacitor of this circuit. In the second control pulse, this is the time interval necessary for the linear charge of the resonant capacitor to the voltage of the power source by the load current, and another time interval equal to three quarters of the resonant frequency period of the serial LC circuit, which occurs automatically and provides the initial voltage on the resonant capacitor of the circuit for the next cycle commutation.

The initial time instants of the auxiliary key control pulses are synchronized with the PWM pulses of the converter control logic. However, their finite durations, due to the presence of the indicated additional intervals, are parameters that depend on the load current, voltage of the power supply and tolerances of the spread of the nominal values of the capacitors and inductances of the resonant circuits. All this leads to the necessity of compiling separate control algorithms for both the auxiliary and the main key in the composition of the Republic of Kazakhstan. In this case, the durations of the control pulses of the main key are not synchronized with the duration of the logical pulses of the PWM control, which are initially set by the control system to generate the required quality of the converter output signal. In addition, the dependence of the times at which zero voltages and currents are mainly realized on the parameters of the electric mode of the circuit and the parameters of the resonant circuit requires the installation of additional monitoring sensors that complicate the design of the circuit.

The closest in technical essence to the claimed solution is a method for controlling a resonant key (RU 169427 U1, 03.16.2017), in which the auxiliary key is unlocked twice for a relatively short time in each of the switching cycles. The first time it is unlocked immediately before turning on the main key, which provides a resonant discharge of the output capacitance of the main key, and creates the condition for its subsequent unlocking at zero voltage. The second time, the auxiliary key is unlocked immediately before the main key is turned off, which provides a resonant current discharge in the output circuit of the main key, and creates a condition for its subsequent locking at zero current. In this case, the initial time instants of the auxiliary key control pulses are synchronized with the PWM pulses of the converter control logic signals. In contrast to the previous analogue, the durations of the control signals of the auxiliary key of the prototype depend almost exclusively on the duration of the resonant processes that form the zero voltage and zero current in the output circuit of the main key as part of the RC. In this case, the minimum duration of the first control signal (immediately before unlocking the main key) is selected as a quarter of the resonant frequency of the parallel LC circuit, and the minimum duration of the second control signal (immediately before locking of the main key) is selected as a quarter of the resonant frequency of the serial LC circuit. The disadvantage of this control method is that the duration of the control pulse of the main key is still not synchronized with the pulses of the PWM signals of the converter control logic. This circumstance is determined by the fact that, as a rule, the capacitance values of a composite LCC circuit are different. As a result of this, the minimum required duration of the first control pulse of the auxiliary key does not equal the duration of the second control pulse. Another disadvantage of the prototype is the dependence of the minimum pulse widths of the auxiliary key control on the tolerances of the nominal parameters of the resonant LC - circuit, the relative influence of which increases with increasing switching frequency.

The technical result, to which the proposed technical solution is directed, is to ensure the same pulse widths for controlling the auxiliary key and their independence from the electric mode of operation of the circuit and the parameters of the scatter of the nominal values of the elements of the resonant circuit. This ensures synchronization of the control pulses of all key elements in the RC with the PWM pulses of the converter control logic, which allows you to maintain the required quality of the converter output signal when switching from classical methods of hard switching to more energy-efficient resonant methods.

The technical result is achieved by the fact that the control method of the resonant key, in which the auxiliary key as part of the resonant key is unlocked twice in each of the switching cycles, the beginning of the first pulse of the auxiliary key control is synchronized with the leading edge of the PWM signal in the logical sequence of the signals of the converter control system, the beginning the second pulse control auxiliary key synchronize with the trailing edge of the PWM signal, the beginning of the duration of the control pulse the key as part of the resonance key is synchronized with the trailing edge of the first auxiliary key control pulse, and the end of the duration of the main key control pulse is synchronized with the trailing edge of the second auxiliary key control pulse, characterized in that two additional free circulation intervals are introduced into each of the switching cycles of the resonant key parts of the resonant inductor current in the squirrel-cage circuit formed by the auxiliary key connected in series with it a resonant inductor, as well as an anti-parallel diode of the main key and its antiphase diode, while the duration of the first control pulse of the auxiliary key is set equal to the duration of the second control pulse of the auxiliary key, and the control pulse of the main key becomes equal to the pulse width of the PWM signal and shifted relative to its front front by a fixed time value.

The essence of the proposed invention and its technical result is illustrated by the relevant drawings.

FIG. 1 Logic pulse diagrams in accordance with the presented control method.

FIG. 2 Scheme of switching the load current with a resonant switch.

FIG. 3 Diagrams of logical impulses, voltage and current of the main switch during the switching process at nominal values of the circuit parameters and its electrical operation mode.

FIG. 4 Diagrams of logical impulses, voltage and current of the main switch during switching when the parameters deviate from the nominal values.

FIG. 5 Experimental diagrams of logical control pulses, voltage and current of the main switch during the switching process.

FIG. 1 contains three diagrams of logical control pulses in accordance with the proposed control method. The first diagram shows the PWM signal 1 in the sequence of logical signals of the control system of the Converter 1.

The second diagram shows the first pulse of control 2 of the auxiliary key and the second pulse of control 3 of the auxiliary key equal to it in duration as part of the PK. In this case, the beginning of the first pulse of control 2 by the auxiliary key is synchronized with the leading edge of the PWM signal 1, and the beginning of the second pulse of control 3 by the auxiliary key is synchronized with the falling edge of the PWM signal 1.

The third diagram shows the control impulse 4 of the main key in the composition of the Republic of Kazakhstan. The beginning of the control pulse 4 is synchronized with the trailing edge of the first control pulse 2 auxiliary key. The end of the control pulse 4 is synchronized with the trailing edge of the second control pulse 3 auxiliary key. With equal duration of control pulses 2 and 3 with the auxiliary key, the control pulse 4 of the main key is shifted relative to the PWM signal 1 by the amount of the fixed delay and is equal in duration to the PWM signal 1.

The implementation of the inventive method for controlling a resonant switch is illustrated by the example of a switching circuit of a continuous load current. FIG. 2.

FIG. 2 represents a basic circuit for switching a load current In with a power supply voltage of circuit E and a resonant switch as a switching element of the circuit. The composition of the RK includes: the main key with an anti-parallel diode 7; a composite diode circuit 8 connected in series with the main key, comprising an antiphase main diode 7 diode 9 and an additional antiphase diode 10 sequentially connected to it; auxiliary key 11; resonant circuit 12, which includes two resonant LC circuits with magnetically coupled resonant inductors L1 and L2 of the same inductance L and magnetic coupling inductance M = L and capacitors C1 and C2; additional diode 13.

Basic diagrams illustrating switching processes in the circuit of FIG. 2 are shown in FIG. 3 at nominal values of the circuit parameters and the electric mode of its operation.

FIG. 3 contains diagrams of logical impulses for controlling a resonance key in accordance with the proposed control method and voltage diagrams 5 and current 6 of the main switch synchronized with them in time as part of the PK. It also shows the main intervals of a separate switching cycle, which is triggered by a given PWM signal 1.

Let the initial key 7 and the auxiliary key 11 be in the open state at the initial time. Then, the load current In flows through the circuit of open diodes 9 and 10 in the composite diode circuit 8. The initial voltage at the output capacitance C1 of the main switch 4 is equal to the value E. Since the antiphase diode 9 is open, the initial voltage at the capacitance C2 is zero. With the auxiliary key 11 open, the initial values of the currents in the inductors L1 are equal to zero.

The switching cycle begins at time t0 with the arrival of the PWM signal 1, the leading edge of which triggers the pulse control auxiliary key 8.

Interval (t1 - t0).

This interval includes a linear increase in the current in the inductance L connected in series with the auxiliary key 8, and the resonant discharge process of the capacitor C1 after the current in the inductance L1 reaches the load current In. The duration of the linear increase in current in the inductance L1 depends on the parameters of the electric mode of the circuit E and In, and the discharge duration of the capacitor C1 is equal to a quarter of the period of the resonant frequency of the process occurring in the parallel resonant circuit formed by the inductance L1 and the capacitance of the capacitor C1:

In the prototype device, immediately after the discharge of capacitor C1, the auxiliary key 11 was locked, and a control signal was supplied to the main key 7, which ensured the unlocking of the main key 7 at zero voltage.

Interval (t2 - t1).

In the presented control method, after the discharge of the capacitor C1, the auxiliary key 11 remains in the closed state. In this case, the first additional interval is introduced into the switching cycle, based on the free circulation of a part of the current ΔI of the resonant inductor L1 in the short-circuit circuit formed by the auxiliary key 11, the resonant inductor L1, as well as the anti-parallel diode of the main switch 7 and its antiphase diode 9. Current ΔI is the part of the current of the resonant inductor L1 that exceeds the load current In, which was formed as a result of the absorption of additional energy by the inductor L1 during the discharge of the capacitor C1. The magnitude of the initial circulation current is determined by the formula:

- волновое сопротивление параллельного резонансного контура L1C1.Where

- wave impedance of the parallel resonant circuit L1C1.

With an active resistance of a short-circuited circuit of units of mOhm, the damping time constant of the circulation current is many times greater than the duration of the first additional interval. As a result, the magnitude of the circulation current over the entire duration of the first additional interval can be considered unchanged and equal to the value of ΔI. Denote the duration of the first additional interval by the symbol ΔТ1. Moreover, ΔT1 = t3-t2.

Interval (t3 - t2).

At the end of the interval ΔT1, the auxiliary key 11 is locked, and the main key 7 is unlocked, taking on itself the load current In. Due to the magnetic coupling between the inductances of the resonant circuit 12, the current accumulated in the inductance of the inductor L1, equal to the sum of the load current In and the circulation current ΔI, is converted into the inductance of the inductor L2, after which this current charges the capacitor C2 with an additional diode 13 to the initial voltage :

- волновое сопротивление резонансного контура L2C2.Where

- wave impedance of the resonant circuit L2C2.

Interval t4 - t3.

. Когда через четверть периода резонансной частоты последовательного резонансного контура L1C2 емкость конденсатора С2 полностью разряжается, амплитуда встречного тока достигает значения: U_C2(0)/ρ₂=I_H+ΔI и рассматриваемый интервал заканчивается. В устройстве прототипа сразу после разряда конденсатора С2 вспомогательный ключ 11 запирался. При этом снимался сигнал управления и с основного ключа 7, что обеспечивало его запирание при нулевом токе.At the end of the duration of the PWM signal 1, its trailing edge starts the second pulse 3 control auxiliary key 13 in the considered switching cycle. In this case, the inductance of the resonant inductor L1 and the capacitance of the capacitor C2 form a series resonant circuit that generates a current directed counter to the load current in the main key. The impedance of this circuit due to the equality of the inductances of the resonant reactors L1 and L2 corresponds to the value

. When after a quarter of the period of the resonant frequency of the series resonant circuit L1C2, the capacitance of the capacitor C2 is completely discharged, the amplitude of the counter current reaches the value: U _C2 (0) / ρ ₂ = I _H + ΔI and the interval under consideration ends. In the prototype device, immediately after the discharge of the capacitor C2, the auxiliary key 11 was locked. At the same time, the control signal was also taken from the main key 7, which ensured its locking at zero current.

Interval (t5 - t4).

In the presented control method, after the discharge of the capacitor C2, the auxiliary key 11 remains in the closed state. At the same time, a second additional interval is introduced into the switching cycle based on the free circulation of the current ΔI of the resonant inductor L1 in the short-circuit circuit formed by the auxiliary key 11, the resonant inductor L1, and also the counter-parallel diode of the main switch 7 and its antiphase diode 9. Denote the duration second additional interval with the symbol ΔТ2. Moreover, ΔT2 = t6-t5.

Interval (t6 - t5).

At the end of the interval ΔT2 auxiliary key 11 is locked. In this case, the control pulse 4 is removed from the main key 7, after which it is locked at zero current. Due to the magnetic coupling between the inductances of the resonant circuit 12, the current accumulated in the inductance of the inductor L1, equal to the sum of the load current 1n and the circulation current ΔI, is converted to the inductance of the inductor L2, after which this current starts charging the capacitor C2 using an additional diode 13. However, when the main key 7 is turned off, the load current In through the open additional antiphase diode 10 simultaneously begins to discharge the capacitance of capacitor C2 and charge the capacitance of capacitor C1. After the capacitor C1 is charged to the voltage of the power source E, the capacitor C2 is completely discharged. In this case, the antiphase diode 9 opens and the load current Iн completely transfers to the circuit of the composite diode circuit 8. At the end of the last interval, the initial currents and voltages on all elements of the RK will return to the initial initial values, and the RK circuit will be ready for a new switching cycle, the beginning of which will be set the subsequent PWM signal.

Consider the influence of the deviation of the parameters of the electric mode of the circuit (E and In) and the parameters of the components of the resonant circuit 12 (L1, L2, C1 and C2) from the nominal values on the duration of the switching intervals, which is illustrated by the diagrams in FIG. 4.

The maximum duration of the first interval (t1max-t0) is determined by the formula:

For all other valid parameter values, the duration of the first interval (t1-t0) will be shorter, while the minimum duration of the first interval (t1min-t0) will be:

Note that a change in the parameter E, in accordance with formula (2), will lead to a change in the amplitude of the circulation current ΔI.

Choosing the duration of the first control signal 2 auxiliary key 11 from the condition:

we obtain the independence of the condition for unlocking the main key 7 at zero voltage from changing the parameters. In this case, the difference between the maximum duration of the first interval (t1max-t0) and the remaining possible but shorter intervals (t1-t0) will be compensated by the first additional interval ΔТ1 of free circulation of current ΔI of the resonant inductor L1 in the short-circuit circuit.

The maximum duration of the time interval (t4max-t3) is determined by the formula:

For all other valid parameter values, the duration of the time interval (t4-t3) will be shorter, while the minimum value of the duration of this interval (t4min-t3) will be:

Choosing the duration of the second control signal 3 auxiliary key 11 from the condition:

we obtain the independence of the condition for locking the main key 7 at zero current from changing parameters. In this case, the difference between the maximum duration of the time interval (t4max-t3) and the remaining possible but shorter intervals (t4-t3) will be compensated by the second additional interval ΔТ2 of free circulation of the current ΔI of the resonant inductor L1 in the short-circuit circuit.

The introduction of two new intervals ΔT1 and ΔT2 in the switching cycle allows you to set equal to the duration of the first 2 and second 3 control signals of the auxiliary key 11 and synchronize the control pulse 4 of the main key 7 with the pulse of the PWM signal 1.

Of the two maximum time intervals (t1max-t0) and (t4max-t3), the one that is the largest is selected. In RC circuits of this type, the capacitance of capacitor C2 is much greater than the capacitance of capacitor C1. For this reason, the condition is almost always satisfied: (t4max-t3)> (t1max-t0). Therefore, the duration of the second control signal 3 by the auxiliary key 11 is still selected from condition (9). Moreover, to establish the equality Δt2 = Δt3, the duration of the first 2 control signals of the auxiliary key 11 is artificially increased due to the additional duration of the first additional free circulation interval by:

In this case, the duration of the control pulse 4 by the main key 7 in the RC, becomes equal to the pulse width of the PWM signal 1 in the logical sequence of signals of the converter control system and shifted relative to its leading edge by a fixed value in time. Thus, in the presented control method, the synchronization of control pulses of all keys in the PK with the classical signals of the PWM sequence is provided.

In confirmation of the result achieved in the proposed method for controlling the resonance key in FIG. 5 shows the experimental data of the process of switching a continuous current of inductive load of 100 A in a circuit similar to FIG. 2, with a voltage source of 600 V.

In FIG. 5 shows the following diagrams:

- logical control pulses: the first 2 and second 3 control pulses of the auxiliary key 11 of the same duration of 150 ns and the control pulse 4 of the main key 7 as part of the RC with a duration of 1 μs;

- voltage 5 and current 6 of the main switch 7 synchronized in time with the control pulses during the switching process.

Vertical scale: for logic control pulses 2, 3 and 4 - 10 V per division; for the voltage of the main switch 7 - 500 V per division; for the current of the main switch 7 - 100 A per division. The horizontal scale for all diagrams is 200 ns per division.

Claims (1)

A method for controlling a resonant key, in which the auxiliary key in the resonant key is unlocked twice in each of the switching cycles, the beginning of the first pulse of control of the auxiliary key is synchronized with the leading edge of the PWM signal in the logical sequence of signals from the converter control system, the beginning of the second pulse of control of the auxiliary key is synchronized with a trailing edge of the PWM signal, the beginning of the duration of the control pulse of the main key in the composition of the resonance key sync they are synchronized with the trailing edge of the first auxiliary key control pulse, and the end of the duration of the main key control pulse is synchronized with the trailing edge of the second auxiliary key control pulse, characterized in that two additional free-circulation intervals of the resonant inductor part of the current are introduced into the circuit in each of the switching cycles of the resonant key a short-circuited circuit formed by an auxiliary key connected in series with a resonant inductor, as well as a counter-pa allelic diode master key and its antiphase diode, wherein the duration of the first pulse controlling the auxiliary key is set equal to the duration of the second auxiliary key control pulse, and the pulse control main key becomes equal to the duration of the PWM signal and shifted relative to its leading edge at the time a fixed value.

Images